Snapshots page shows empty when source JPGs are deleted after transcode #90

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opened 2026-06-05 07:40:39 +00:00 by coding-agent-marvin8 · 1 comment

coding-agent-marvin8 commented

2026-06-05 07:40:39 +00:00

(Migrated from codeberg.org)

The static clip preview is served from the thumbnail copy just fine, so the "No snapshots found" message is clearly wrong whenever is set and the file exists.

When a camera is configured with , the pipeline deletes all source snapshot files alongside the after transcoding completes. The route only searches , so it finds nothing and renders "No snapshots found" — even though a thumbnail copy survives in and is recorded in . The static clip preview is served from the thumbnail copy just fine, so the "No snapshots found" message is clearly wrong whenever is set and the file exists.

coding-agent-marvin8 commented

2026-06-05 07:40:53 +00:00

(Migrated from codeberg.org)

Findings

The pipeline's delete path (pipeline.py _delete_source) removes both the .dav and every associated .jpg snapshot after transcoding when delete_after_transcode is enabled. The clip-snapshots route in src/cang/web/routes/snapshots.py only globs camera.root/day/channel/jpg and never consults clips.thumbnail. The thumbnail copy in output_dir is the only surviving snapshot but is never consulted.

Secondary: _snapshot_time in snapshots.py parses the second component with int(stem) while the Dahua adapter uses a leading-digits regex. If a filename has trailing non-digit characters the route silently drops the snapshot.

Plan of attack

In the clip_snapshot_album and clip_snapshot_image route handlers, after collect_snapshots_for_clip returns empty, fall back to Path(clip[thumbnail]) if it is set and exists on disk.
Extend the safety allow-list in clip_snapshot_image to also accept paths within cfg.server.output_dir (currently only camera_roots are allowed).
Fix _snapshot_time to use a leading-digits regex like the adapter instead of int(stem).
Add failing tests first (TDD) for all three changes, then implement.

Files changed: src/cang/web/routes/snapshots.py, tests/web/test_clip_snapshots.py, tests/test_snapshots.py

**Findings** The pipeline's delete path (pipeline.py _delete_source) removes both the .dav and every associated .jpg snapshot after transcoding when delete_after_transcode is enabled. The clip-snapshots route in src/cang/web/routes/snapshots.py only globs camera.root/day/channel/jpg and never consults clips.thumbnail. The thumbnail copy in output_dir is the only surviving snapshot but is never consulted. Secondary: _snapshot_time in snapshots.py parses the second component with int(stem) while the Dahua adapter uses a leading-digits regex. If a filename has trailing non-digit characters the route silently drops the snapshot. **Plan of attack** 1. In the clip_snapshot_album and clip_snapshot_image route handlers, after collect_snapshots_for_clip returns empty, fall back to Path(clip[thumbnail]) if it is set and exists on disk. 2. Extend the safety allow-list in clip_snapshot_image to also accept paths within cfg.server.output_dir (currently only camera_roots are allowed). 3. Fix _snapshot_time to use a leading-digits regex like the adapter instead of int(stem). 4. Add failing tests first (TDD) for all three changes, then implement. Files changed: src/cang/web/routes/snapshots.py, tests/web/test_clip_snapshots.py, tests/test_snapshots.py

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marvin8/cang#90

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