CLI hangs instead of exiting on remux error when attempting to mux TX3G to Matroska

[Marth64]

Summary of the bug:

Attempted to remux MP4 to Matroska. Accidentally set -c:s copy from a TX3G track (which cannot fit in Matroska). FFmpeg raises the error to say this is not supported, but then hangs and needs to be killed.

In 6.x, CLI exits properly on error and does not hang.

How to reproduce:

ffmpeg -i "INPUT.mp4" -map 0:0 -codec:0 copy -map 0:1 -codec:1 copy -f matroska "VIDEO.mkv" -map 0:2 -codec:0 copy -metadata:s:0 title=BUG -f matroska "SUBS.mks"

ffmpeg version N-114279-g746c27f314 Copyright (c) 2000-2024 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: --enable-libdvdread --enable-libdvdnav --enable-gpl --enable-demuxer=dvdvideo
  libavutil      59.  2.100 / 59.  2.100
  libavcodec     61.  1.101 / 61.  1.101
  libavformat    61.  0.100 / 61.  0.100
  libavdevice    61.  0.100 / 61.  0.100
  libavfilter    10.  0.100 / 10.  0.100
  libswscale      8.  0.100 /  8.  0.100
  libswresample   5.  0.100 /  5.  0.100
  libpostproc    58.  0.100 / 58.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'INPUT.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: mp42iso6
    creation_time   : 2023-10-13T18:11:59.000000Z
    title           : TITLE
    comment         : COMMENT
  Duration: 00:21:46.46, start: 0.000000, bitrate: 8018 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 7820 kb/s, 23.98 fps, 23.98 tbr, 24k tbn (default)
      Metadata:
        creation_time   : 2023-10-13T18:11:59.000000Z
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](eng): Audio: eac3 (ec-3 / 0x332D6365), 48000 Hz, 5.1(side), fltp, 192 kb/s (default)
      Metadata:
        creation_time   : 2023-10-13T18:11:59.000000Z
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]
      Side data:
        audio service type: main
  Stream #0:2[0x3](eng): Subtitle: mov_text (tx3g / 0x67337874), 0 kb/s (default)
      Metadata:
        creation_time   : 2023-10-13T18:11:59.000000Z
        handler_name    : English
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
  Stream #0:2 -> #1:0 (copy)
Output #0, matroska, to 'VIDEO.mkv':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: mp42iso6
    comment         : COMMENT
    title           : TITLE
    encoder         : Lavf61.0.100
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 7820 kb/s, 23.98 fps, 23.98 tbr, 1k tbn (default)
      Metadata:
        creation_time   : 2023-10-13T18:11:59.000000Z
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
  Stream #0:1(eng): Audio: eac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), fltp, 192 kb/s (default)
      Metadata:
        creation_time   : 2023-10-13T18:11:59.000000Z
        handler_name    : SoundHandler
        vendor_id       : [0][0][0][0]
      Side data:
        audio service type: main
[matroska @ 0x5577bd257000] Subtitle codec 94213 is not supported.
[out#1/matroska @ 0x5577bd252840] Could not write header (incorrect codec parameters ?): Function not implemented
Conversion failed!

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[Marth64]

See latest log in description. Ignore first log, was comparing against 6.1 and pasted on accident

[elenril]

Does this still happen? I think it should have been fixed by da17c4d24a35de1bbdea2b657b367da5287ae19d

[Marth64]

Hi,

It's still happening on master@b89ee2653919c14193f646ba03b2bf1d13c9aa2d

I have been trying to intermittently look into it as well. Thanks for checking it.

[elenril]

Then it should be fixed by ​https://lists.ffmpeg.org//pipermail/ffmpeg-devel/2024-March/324440.html (I didn't notice it actually covers more cases than pthread_create() failing, commit message updated to match).

[Marth64]

Yes, that patch fixes the issue. ffmpeg closes on the error condition without hanging. Thank you!

[elenril]

Fixed in 24b9f29ff2e0b84ae1345f51cbf7240e079d7a2b