Transcode multichannel audio to keep multichannel support

[cewert]

If the device supports multichannel audio and the selected audio stream has more than 2 channels, tell the server we want ac3 (or dts) instead of the usual aac for stereo speakers.

Issues

Remake of #1466
Fixes #1979

[dathbe]

Posted a testing comment here #1979 (comment)

[cewert]

@dathbe thanks for testing. Can you post the file info? Either ffprobe or the media info from the web client. Does it create a transcode log for the server? If so can you post that too

[dathbe]

I tried three files. One I had created for testing purposes with 5.1 AAC, and the other two were just standard files already on my HDD. Here are the stats for the new file.

ffprobe version 4.3.8-0+deb11u1 Copyright (c) 2007-2024 the FFmpeg developers
  built with gcc 10 (Debian 10.2.1-6)
  configuration: --prefix=/usr --extra-version=0+deb11u1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, matroska,webm, from 'aac_5.1.mkv':
  Metadata:
    creation_time   : 2024-10-21T19:34:54.000000Z
    ENCODER         : Lavf60.16.100
  Duration: 00:06:40.02, start: -0.021000, bitrate: 938 kb/s
    Chapter #0:0: start 8.782000, end 353.919000
    Metadata:
      title           : Chapter 2
    Chapter #0:1: start 353.919000, end 399.965000
    Metadata:
      title           : Chapter 3
    Stream #0:0: Video: hevc (Main), yuv420p(tv, bt709), 1280x542 [SAR 1:1 DAR 640:271], 23.98 fps, 23.98 tbr, 1k tbn, 23.98 tbc (default)
    Metadata:
      DURATION        : 00:06:40.007000000
    Stream #0:1(eng): Audio: aac (LC), 48000 Hz, 5.1, fltp (default)
    Metadata:
      title           : Surround 5.1
      DURATION        : 00:06:40.021000000

I do not see any transcode logs. The existing files on my HDD should have direct played without any transcoding.

Also, flagging that @closesim tested and replied here: #1979 (comment)
Same results.

I'll also add that I tested both the new and existing files in the production version of the app, and they all played fine (with the expected downmixing of AAC 5.1 to 2.0).