source/README.md

Source: how the CamStack YOLO builds are made

This folder is the Corresponding Source under the GNU AGPL-3.0 for the Ultralytics-derived weights in this mirror (objectDetection/yolo26, objectDetection/yolov9, segmentation/yolo26-seg). The full source offer is in THIRD_PARTY_MODELS.md.

File	What it is
build-camstack-models.py	Rebuilds every file in the three folders above. One recipe per hosted file stem: upstream checkpoint, input size, the Ultralytics export() arguments, the OpenVINO precisions and the INT8 calibration count. Each value is what the hosted file records about itself in its metadata.
convert_lib.py	The converter build-camstack-models.py calls for OpenVINO: ONNX to IR (ov.convert_model, FP32 or FP16-compressed), NNCF INT8 post-training quantisation, and validation of every IR. It is the same file CamStack's Model Studio runs.
requirements.txt	Python dependencies of convert_lib.py, with per-platform markers.
export-models.py	An older bulk exporter for YOLOv8 / YOLOv9 / YOLO11 ids. No file in this mirror needs it.

Rebuilding

python3 -m venv .venv && . .venv/bin/activate
pip install -r requirements.txt ultralytics openvino nncf
python build-camstack-models.py --list            # the recipes: one per hosted file stem
python build-camstack-models.py --check-hosted    # every hosted file is a recipe output?

python build-camstack-models.py --variant camstack-yolo26n-320   # one hosted model, every format
python build-camstack-models.py --family yolov9                  # one mirror folder
python build-camstack-models.py --all                            # the whole set
python build-camstack-models.py --all --formats onnx,openvino    # some formats only

Results go to ./exported-models/<mirror path>, for example exported-models/objectDetection/yolo26/openvino/camstack-yolo26n-320-int8.xml. Each build step runs in its own Python process: on macOS, CoreML, OpenVINO and TensorFlow crash one another when they share one. CoreML needs macOS.

What the recipes encode (the hosted files record each of these):

Folder	Files	ONNX	CoreML	OpenVINO IR
objectDetection/yolo26	camstack-yolo26{n,s,m,l,x} @640	static, opset 17	static, batch 1, FP16	FP16 as <stem>.xml and <stem>-fp16.xml; INT8 <stem>-int8.xml (128 images)
objectDetection/yolo26	camstack-yolo26{n,s,m,l}-{320,256}	dynamic axes, opset 17	static, batch 1, FP16	FP32 <stem>.xml; INT8 <stem>-int8.xml (128 images)
objectDetection/yolov9	camstack-yolov9{t,s,m,c}-{320,640}	static, opset 13	static, batch 1, FP16	FP16 <stem>-fp16.xml; INT8 <stem>-int8.xml (300 images)
segmentation/yolo26-seg	camstack-yolo26{n,s,m}-seg @640	static, opset 17	static, batch 1, FP16	FP16 <stem>.xml

Recorded tool versions (Ultralytics / PyTorch / coremltools / OpenVINO): YOLO26 @640 and YOLO26-seg 8.4.24 / 2.10.0 / 9.0 / 2026.2.1; YOLO26 @320 and @256 8.4.92 / 2.13.0 for ONNX, 2.5.1 for CoreML / 8.3.0 / 2026.2.1; YOLOv9 8.4.98 / 2.13.0 / 9.0 / 2026.2.1. The script warns when the installed Ultralytics differs. With these versions a rebuild gives the hosted weights. Other versions give the same weights in a possibly different graph. The @320 and @256 CoreML exports use coremltools 8.3 with PyTorch 2.5.1, the macOS pins in requirements.txt.

The @320 and @256 CoreML packages were batch-flexible (1..16) until 2026-10-07. That package aborts any process that loads it on macOS 26.2, on every compute unit, because Core ML's gather_nd shape pass fails on a flexible batch. They are now exported with a static batch of 1 and were replaced in place, under the same names. The script refuses a batch-flexible CoreML recipe for a YOLO26 checkpoint.

Every CoreML package computes in FP16, the only precision the Apple Neural Engine runs. An FP32 package runs on the GPU or the CPU instead, 2–4× slower. The YOLOv9 packages were FP32 until 2026-10-07: Ultralytics 8.4.98 pins FP32 unless half=True is passed. They were re-exported FP16 and replaced in place, under the same names. The YOLO26 @640 and YOLO26-seg packages record half: False but are FP16, because Ultralytics 8.4.24 left Core ML's FP16 default in place; their recipes now pass half=True so a current Ultralytics gives the same precision. The script refuses an FP32 CoreML recipe.

INT8 calibration

The INT8 IRs are NNCF post-training quantisation of the ONNX (convert_lib.quantize_openvino_int8), calibrated on COCO images. The documented calibration set is COCO val2017:

curl -LO http://images.cocodataset.org/zips/val2017.zip && unzip -q val2017.zip
python build-camstack-models.py --family yolo26 --calib-dir ./val2017

The recipe takes the first N images in file-name order: 128 for YOLO26, 300 for YOLOv9, as recorded in each IR's rt_info. Each image is letterboxed to the model's input size, CENTRED with grey (114) padding, and scaled to [0, 1], the way CamStack feeds the model at runtime. --calib-samples overrides N. An IR does not record WHICH images calibrated it, so a different set gives an equivalent INT8 model, not a bit-identical one. Without calibration images the INT8 files are skipped and the run says so.

Until 2026-10-08 the calibration padded TOP-LEFT. On that date every INT8 IR was re-quantised centred from the hosted ONNX (--reuse-onnx, OpenVINO 2026.2.1 + NNCF 3.2.0) and measured against the old one. 13 replaced the old IR, 8 measured worse and were kept. The replaced IRs are under archive/2026-10-08-int8-topleft-calibration/ at the mirror root. archive/convert_lib-before-2026-10-08.py reproduces the top-left ones; it rebuilds the hosted yolov9m-640 INT8 IR bit for bit.

INT8 recipe (since 2026-10-09)

convert_lib.quantize_openvino_int8 keeps the YOLO Detect head in float.

• YOLOv9: the head's own ops stay float: the DFL softmax and the box decode (anchor ± distance, ×stride, class sigmoid). The conv branches stay INT8.
• YOLO26: the whole end-to-end head stays float.
• Every model: NNCF preset MIXED and full bias correction.

This follows the Ultralytics OpenVINO INT8 exporter and NNCF's YOLO26 example. The previous recipe quantised the decode, which put box coordinates on a 256-level grid.

Result:

• On all 8 YOLOv9 IRs, mAP50-95 went from 0.01–0.18 below float to within noise of it, at NPU latency within 1 %.
• 14 IRs were replaced in place: every yolov9*-int8, yolo26{n,s,l}-int8, yolo26n-320-int8 and yolo26{n,s}-256-int8.
• The previous files are under archive/2026-10-09-int8-before-head-float-recipe/ at the mirror root.

Seven YOLO26 IRs were kept, because the float head cost 11–22 % latency on the Intel iGPU:

• yolo26{m,x}-int8 and yolo26{m,l}-256-int8 (centred) are reproduced by archive/convert_lib-before-2026-10-09.py;
• yolo26{s,m,l}-320-int8 (top-left) are reproduced by archive/convert_lib-before-2026-10-08.py.

build-camstack-models.py lists which IR carries which recipe.

Licences

• These scripts (build-camstack-models.py, convert_lib.py, export-models.py, requirements.txt) are CamStack's own code and are offered under the MIT licence.
• The weights they produce keep their upstream licence. The Ultralytics checkpoints are AGPL-3.0 (LICENSES/AGPL-3.0.txt), and so is every file derived from them in this mirror. Nothing here is relicensed; see LICENSE and each folder's README.md.