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README_en.md

@@ -19,8 +19,9 @@ size_categories:
 CAP is a **human hand motion capture + dexterous manipulation demonstration** dataset. It records an operator performing the **cups ordering (`cups_order`)** task with the **right hand**. Data is captured with a DexCap-style pipeline and ships both **compressed trajectory HDF5 files** and **raw multi-view camera frames**, ready for motion retargeting, imitation learning, and hand-pose analysis.
 
 - Repo: `dex-robot/cap`
-- Main file: `cap.zip` (10,694,426,624 bytes ≈ 9.96 GiB)
-- Files: 18,940
+- Main file: `cap.zip` (10,697,737,890 bytes ≈ 9.96 GiB)
+- Contents: 18,939 files + 24 directory entries
+- SHA256: `f91c11ee1761822fa875d4783c1fd9388f6fa3f0fa3feeef6cd5c20775220c10`
 - Capture date: 2026-07-07
 - Task: cups ordering
 - Hand: right
@@ -37,9 +38,9 @@ CAP is a **human hand motion capture + dexterous manipulation demonstration** da
 | Recordings | 5 (16:46:34 / 16:54:35 / 16:56:54 / 16:59:04 / 17:01:24) |
 | Trajectory files | 5 × `.hdf5` (one per recording) |
 | Camera views | 6 (left hand / right hand / head stereo / head global RGB / head global depth) |
-| Image frames | 18,915 × `.png` + 5 × `.mp4` |
+| Image frames | 18,914 × `.png` + 5 × `.mp4` |
 | Other assets | 3 × `.json`, 6 × `.txt`, 5 × `.npy`, 1 × `.raw` |
-| Archive size | 10.7 GB (10,694,426,624 bytes) |
+| Archive size | 10.7 GB (10,697,737,890 bytes) |
 
 ---
 
@@ -92,14 +93,14 @@ cap/
 
 | View directory | PNG frames | Video |
 | --- | --- | --- |
-| `head_global_depth_frames` | 5,567 | ✅ |
-| `right_hand_rgb_frames` | 3,091 | ✅ |
-| `head_zed_right_frames` | 2,631 | ✅ |
-| `left_hand_rgb_frames` | 2,565 | ✅ |
-| `head_zed_left_frames` | 2,548 | ✅ |
-| `head_global_rgb_frames` | 2,524 | ✅ |
+| `head_global_depth_frames` | 5,565 | ✅ |
+| `right_hand_rgb_frames` | 3,089 | ✅ |
+| `head_zed_right_frames` | 2,629 | ✅ |
+| `left_hand_rgb_frames` | 2,563 | ✅ |
+| `head_zed_left_frames` | 2,546 | ✅ |
+| `head_global_rgb_frames` | 2,522 | ✅ |
 
-Frames are named `frame_%06d.png` (zero-based, contiguous) and align by index with the MP4 in the same view directory.
+Frames are named `frame_%06d.png`, but the indices are **not strictly contiguous** (frames were dropped during capture). Always use the sorted filename order; do not assume `i` and `i+1` are adjacent.
 
 ---
 
@@ -132,10 +133,17 @@ https://huggingface.co/datasets/dex-robot/cap/resolve/main/cap.zip
 ## 6. Extract & Verify
 
 ```bash
-# integrity check (no output errors = OK)
+# 1) size
+stat -c %s cap.zip        # expected: 10697737890
+
+# 2) SHA256
+sha256sum cap.zip
+# f91c11ee1761822fa875d4783c1fd9388f6fa3f0fa3feeef6cd5c20775220c10
+
+# 3) CRC check (all 18963 entries must report OK)
 unzip -t cap.zip
 
-# extract -> cap/
+# 4) extract -> cap/
 unzip -q cap.zip
 
 du -sh cap
@@ -146,7 +154,7 @@ Expected:
 ```
 cap/
 ├── hdf5/      (5 .hdf5 files)
-└── raw_data/  (18,935 files)
+└── raw_data/  (18,934 files)
 ```
 
 ---
@@ -217,10 +225,19 @@ pip install h5py opencv-python numpy
 `huggingface-cli download` resumes automatically — just re-run the same command. Add `--max-workers 1` for a more stable (slower) transfer.
 
 **Q: `unzip` says "End-of-central-directory signature not found"?**
-The download is incomplete / truncated. Check that the file size is exactly **10,694,426,624 bytes**; if not, re-download.
+The download is incomplete / truncated. Check that the size is exactly **10,697,737,890 bytes** and the SHA256 matches; if not, re-download.
 
 **Q: I only need trajectories, not the 10 GB of images?**
 Currently only the full bundle is published. Open a Discussion if you need a split release.
 
 **Q: How do I align depth with RGB?**
 `*_frames` and the MP4 of the same view share frame indices (`frame_%06d`). Cross-view alignment: use the calibration JSON under `raw_data/.../observe/vision/`.
+
+---
+
+## 11. Known Limitations
+
+1. **Frame indices are not contiguous.** Each view's `frame_%06d.png` has gaps (frames dropped during capture) — e.g. `right_hand_rgb_frames` holds 3,089 frames with a max index of 3,746. Use sorted filename order; never infer the next frame as `i+1`.
+2. **Raw frames cover the first session only.** Of the 5 recordings, only `164634` ships full multi-view PNG / MP4; the other four provide HDF5 trajectories only.
+3. **HDF5 internal layout may evolve across capture versions.** Group / dataset names can differ between recordings — inspect the structure with `visititems` before reading arrays.
+4. The archive was recovered from an interrupted packing process and passes CRC verification for all 18,963 entries; one incomplete trailing PNG frame was dropped.