The clip duration came from the media duration (`mdhd`), which runs on
the decode timeline. ffmpeg / x264 MP4s with B-frames skip the reorder
delay with an edit, so every one imported a frame too long (a 120-frame
file became 121 frames, the last a held repeat). A video track delayed
by a leading empty edit was a frame short, and its last frame could not
be reached.
Use the sum of the track's edits (movie timescale, what `tkhd` records)
when there is an edit list. Fragmented files, and edit lists that add up
to nothing or overflow a Tick, keep the media duration.
Tests: a unit test with crafted edit lists (skip, empty edit, hostile
sizes) and an ffmpeg oracle test (libx264 with B-frames: 60 frames,
was 61).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
EthanSuquetandClaude Opus 5.5
1f2f20a700