The video codec parsers (HEVC, H.264, VC-1, MPEG-2) used
pes.dts.or(pes.pts) as each frame's timestamp. MKV block timecodes
are presentation timestamps; frames are stored in decode order and
the player reorders for display by timecode. Using DTS makes the
timecode monotonic in storage order, presenting B-frames in decode
order — visible motion judder / wrong frames on playback, and
PTS-based seeking lands on the wrong frame.
The compressed video was always byte-correct (verified by NAL-level
diff against a known-good demux); this was purely a timestamp defect
affecting every B-frame title. Fix: prefer PTS (pes.pts.or(pes.dts)).
Verified on a real UHD iso->mkv: emitted PTS now reorders for
B-frames identically to a reference muxer.
Update the two tests that asserted the old DTS-preferred behavior and
add an HEVC regression test pinning PTS as the block timecode.
MattJackson
5b702a76a7