Scope setts to audio DTS and verify A/V sync in the repair gate - #840
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Two refinements to the lossless timestamp repair: - Attempt setts only when every non-monotonic DTS is on an audio stream. setts is audio-only (a video setts would reorder B-frames), so a video or subtitle DTS is skipped straight to RepairFailed with no wasted rewrite. DtsInfo records each stream's codec type to decide this. This also fixes a latent false positive: DtsInfo fell back to PTS when a packet had no DTS, but Matroska video stores no DTS and its display PTS is legitimately non-monotonic for B-frames; assess only real DTS now. - The gate compared only the payload hash, which proves the samples are unchanged but not their timing. Also compare each stream's start and duration and reject a repair that shifts any stream beyond the A/V-sync tolerance, so a timestamp nudge can never drift audio out of sync. Validated on the corpus: audio-DTS files (Eureka, Ghosted) repair and the sync gate accepts them; video-DTS (Love Island, 50 First Dates) and post-decode (Diplo) skip setts and stay RepairFailed.
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Pull request overview
This PR tightens the lossless DTS timestamp-repair path by (1) only attempting setts when the detected non-monotonic DTS is audio-only, and (2) extending the regression gate to verify that stream timing (start/duration) is preserved within an A/V-sync tolerance after the timestamp rewrite.
Changes:
- Gate
settsrepair onDtsInfo.NonMonotonicIsAudioOnly(avoid attempting an audio-only rewrite when the non-monotonic stream is video/subtitle or when analysis is inconclusive). - Extend the timestamp-repair regression gate to validate per-stream
start_timeanddurationviaffprobewithin a 40ms tolerance. - Add JSON-schema + tests for stream timing parsing; update release notes wording in
HISTORY.md.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| PlexCleanerTests/StreamTimingsProbeTests.cs | Adds coverage for parsing ffprobe stream timing JSON and missing timings behavior. |
| PlexCleanerTests/DtsInfoTests.cs | Adds tests for audio-only vs mixed vs video non-monotonic DTS classification. |
| PlexCleaner/ProcessFile.cs | Gates setts attempt on audio-only DTS and adds timing-based A/V sync validation to the regression gate. |
| PlexCleaner/FfProbeTool.cs | Adds GetStreamTimings to query per-stream start_time/duration as JSON. |
| PlexCleaner/FfMpegToolJsonSchema.cs | Introduces StreamTimingsProbe/StreamTiming schema for ffprobe output parsing. |
| PlexCleaner/DtsInfo.cs | Tracks stream codec_type and ignores packets without real DTS to avoid false positives. |
| HISTORY.md | Updates release notes to reflect audio-only repair scope and new sync gate. |
WithinSyncTolerance passed whenever either side was NaN, so an asymmetric missing start_time or duration slipped through unverified. Pass only when both sides are NaN (symmetric, uncomparable); a value on just one side now fails the gate.
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Follow-up to #836/#837, from the regression review.
1. Audio-scope the setts attempt.
settsis applied-bsf:a(audio only) - a videosettswould reorder B-frames - so it can only repair an audio-stream DTS.DtsInfonow records each stream'scodec_typeand exposesNonMonotonicIsAudioOnly; a video/subtitle DTS, or a post-decode break with no demux target, skips straight toRepairFailedwith no wasted rewrite + re-verify.This also fixes a latent false positive:
DtsInfofell back to PTS when a packet had no DTS, but Matroska video stores no DTS and its display PTS is legitimately non-monotonic for B-frames, so video was being flagged as non-monotonic. It was harmless before (setts ran regardless) but the audio-only gate exposed it.DtsInfonow assesses only packets that carry a real DTS.2. Verify A/V sync in the gate. The streamhash gate proved the coded packets are byte-identical but said nothing about timing - and
settschanges timestamps. The gate now also compares each stream'sstart_timeandduration(viaffprobe) and rejects a repair that shifts any stream beyond a 40 ms A/V-sync tolerance, so a nudge can never drift audio out of sync. (The #827 design called for this A/V-offset check; the first implementation dropped it.)Corpus validation (local build, ffmpeg 8.0.1): Eureka + Ghosted (audio DTS) ->
Repairing->Timestamp repair succeeded->Repaired, sync gate accepts; Love Island + 50 First Dates (video DTS) and Diplo (post-decode) ->RepairFailed, setts skipped.213 tests pass (added
DtsInfoaudio-only cases and a timings-parse test); build, format, markdownlint clean.🤖 Generated with Claude Code