crosstyan
d0f3dc5cf1
Move the legacy /camera/* contract into its own reference page so the main MCAP layout doc can stay focused on current bundled and copy-layout behavior. Document the compatibility model explicitly: legacy single-camera is operationally equivalent to one-camera copy when the effective camera label is treated as the literal `camera`. Update the mcap_rgbd_example helper and recipe docs to accept legacy /camera/* inputs under that compatibility rule instead of rejecting them.
61 lines
2.6 KiB
Markdown
61 lines
2.6 KiB
Markdown
# Legacy Single-Camera MCAP Layout
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This page is the reference for the older `/camera/*` MCAP wire shape.
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It is still used by some generic sink/tester paths in the repository, but it is no longer the default shape written by `zed_svo_to_mcap` for a single `.svo` or `.svo2` input.
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## Compatibility With Copy Layout
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In practice, this layout is very close to the one-camera `copy` shape:
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- legacy single-camera uses `/camera/video`, `/camera/depth`, and related `/camera/*` topics
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- one-camera `copy` uses `/{label}/video`, `/{label}/depth`, and related `/{label}/*` topics
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So the compatibility mental model is:
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- treat the camera label as the literal `camera`
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- replace `/{label}/...` with `/camera/...`
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- there is still no `/bundle`
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- timestamps remain per-camera sample timestamps
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That is why legacy single-camera is conceptually compatible with `copy`, even though the topic paths are not namespaced the same way.
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## Topics
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| Topic | Schema / Encoding | Notes |
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|------|------|------|
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| `/camera/video` | `foxglove.CompressedVideo` | H.264 or H.265 Annex B access units |
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| `/camera/depth` | `cvmmap_streamer.DepthMap` | RVL-compressed depth payload |
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| `/camera/calibration` | `foxglove.CameraCalibration` | Video intrinsics |
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| `/camera/depth_calibration` | `foxglove.CameraCalibration` | Written only when depth resolution differs from video |
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| `/camera/pose` | `foxglove.PoseInFrame` | Optional; only when pose export is enabled and tracking is valid |
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| `/camera/body` | raw `cvmmap.body_tracking.v1` | Optional raw body-tracking packets; see [mcap_body_tracking.md](./mcap_body_tracking.md) |
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## Timestamp Semantics
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Legacy single-camera export preserves the original per-frame source timestamp on video, depth, and pose messages.
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Like `copy`, there is no separate bundle time:
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- `/camera/video`, `/camera/depth`, and `/camera/pose` use the original camera sample timestamp
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- calibration and depth-calibration messages use the timestamp of the first emitted sample
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## Corruption Behavior
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Like `copy`, this layout has no manifest or placeholder contract:
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- unreadable tail frames are treated as end-of-stream
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- mid-stream corruption is skipped until a readable frame is found
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- the topic stream simply resumes at the recovered readable frame
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## Validation Expectations
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The current validation contract is:
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- `/camera/video` must exist and contain at least one message
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- `/camera/depth` must exist and contain at least one message
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- `/camera/calibration` must exist exactly once
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- `/camera/video` and `/camera/depth` message counts must match
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- `/camera/depth_calibration` may appear zero or one time
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- `/camera/pose` is optional, but it may not outnumber `/camera/video`
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