mkv demuxer claims corrupt file while lavf plays backs normally

[IzanagisBurden]

mpv Information

mpv v0.39.0-615-gca211b5b Copyright © 2000-2025 mpv/MPlayer/mplayer2 projects
 built on Jan 11 2025 00:10:20
libplacebo version: v7.350.0 (v7.349.0-30-g056b852-dirty)
FFmpeg version: N-118300-g5a72266d4
FFmpeg library versions:
   libavcodec      61.31.100
   libavdevice     61.4.100
   libavfilter     10.6.101
   libavformat     61.9.106
   libavutil       59.55.100
   libswresample   5.4.100
   libswscale      8.13.100

Other Information

- Windows version: Microsoft Windows NT 10.0.26100.0/26100.2605
- GPU model, driver and version: GTX 1080 Ti, 560.94
- Source of mpv: shinchiro
- Latest known working version: N/A
- Issue started after the following happened: N/A

Reproduction Steps

1. Play the file with --no-config. Playback will stutter, skip and show artifacts.
2. Play the file with --demuxer=+lavf. Playback will be normal.

The file can also be demuxed with ffmpeg or mkvextract and each stream can be played back without issue.

Expected Behavior

Play the file normally.

Actual Behavior

Playback will stutter, skip and show artifacts.

Log File

output.txt

Sample Files

https://0x0.st/Xg6E.mkv

I carefully read all instruction and confirm that I did the following:

• I tested with the latest mpv version to validate that the issue is not already fixed.
• I provided all required information including system and mpv version.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.

[llyyr]

You may need to seek around a bit to break it, and seems to be caused by having more than 128 tracks. The file plays perfectly if you remove a few subtitle tracks