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scans/metal_chain/converted/README.md

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+# Converted Robotics Dataset
+
+This dataset stores authoritative timestamps and metadata in Parquet tables and
+stores frame payloads in video containers. Video presentation timestamps are not
+used for synchronization; use `tables/frames.parquet` and `video_frame_idx`.
+
+Core loading rule:
+
+```text
+decoded video frame k == frames.parquet row where video_frame_idx == k
+```
+
+Useful files:
+
+- `dataset_manifest.parquet`: converted sessions in this dataset root
+- `sessions/<session_id>/metadata/streams.parquet`: stream IDs and modalities
+- `sessions/<session_id>/metadata/videos.parquet`: stream-to-video mapping
+- `sessions/<session_id>/tables/frames.parquet`: authoritative timestamps,
+  frame indices, clock domains, and hashes
+- `sessions/<session_id>/tables/robot_states.parquet`: robot states, if present
+- `sessions/<session_id>/metadata/calibration.json`: calibration and transform
+  conventions
+- `sessions/<session_id>/metadata/validation_report.json`: validation status
+
+Downstream reading requires Python, NumPy, PyArrow, and PyAV/FFmpeg-compatible
+decoders. Camera SDKs are conversion-only dependencies.