ffplay doesn't play audio on file with 12 audio channels

[diogo.r]

Summary of the bug:
When playing this 12 audio channel file, ffplay doesn't play audio and prints a message that seems to indicate undefined behavior (weird characters, different each time).

File: ​https://www.dropbox.com/s/0sysv238h8fl6h0/12-audio-channels.mkv?dl=0

How to reproduce:

% ffplay.exe .\12-audio-channels.mkv
ffplay version 5.1-essentials_build-www.gyan.dev Copyright (c) 2003-2022 the FFmpeg developers
  built with gcc 12.1.0 (Rev2, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora --enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, matroska,webm, from '.\12-audio-channels.mkv': 0B f=0/0
  Metadata:
    COMPATIBLE_BRANDS: mp42isomavc1
    MAJOR_BRAND     : mp42
    MINOR_VERSION   : 0
    ENCODER         : Lavf59.27.100
  Duration: 00:00:05.57, start: 0.000000, bitrate: 13983 kb/s
  Stream #0:0: Audio: pcm_s24le, 48000 Hz, 12 channels, s32 (24 bit), 13824 kb/s
    Metadata:
      ENCODER         : Lavc59.37.100 pcm_s24le
      DURATION        : 00:00:05.568000000
  Stream #0:1: Video: h264 (High), yuv420p(tv, bt709, progressive), 560x320, 30 fps, 30 tbr, 1k tbn (default)
    Metadata:
      VENDOR_ID       : [0][0][0][0]
      ENCODER         : Lavc59.37.100 libx264
      DURATION        : 00:00:05.533000000
SDL_OpenAudio (12 channels, 48000 Hz): Unsupported number of audio channels.
[SWR @ 0000023e85d75640] Rematrix is needed between 12 channels and  Vׅ>? but there is not enough information to do it
Cannot create sample rate converter for conversion of 48000 Hz s16 12 channels to 48000 Hz s16 2 channels!
[SWR @ 0000023e85d75640] Rematrix is needed between 12 channels and  Vׅ>? but there is not enough information to do it
Cannot create sample rate converter for conversion of 48000 Hz s16 12 channels to 48000 Hz s16 2 channels!
[SWR @ 0000023e85d75640] Rematrix is needed between 12 channels and  Vׅ>? but there is not enough information to do it
Cannot create sample rate converter for conversion of 48000 Hz s16 12 channels to 48000 Hz s16 2 channels!
[...]

[Marton Balint]

The fact that ffplay cannot play a 12ch file is kind of expected, because it has no information how to downmix it to a layout your sound device can handle. So that alone is not an issue.

The error message with the grabled channel layout description is strange though, and I can't reproduce it nor can I see how that can happen. After all av_channel_layout_describe() always initializes its output to an empty string.

[diogo.r]

Personally, this issue doesn't bother me much, if you want to leave it open until someone else runs into it, it's perfectly fine by me. Is there anything else I help with?