I:\>ffmpeg -loglevel verbose -i "BBC_Short_HDR.mov" -af pan="5.1(side):c2=FL|c3=FR|c4=FC|c5=LFE|c6=SL|c7=SR" -acodec ac3 -ac 6 -ar 48000 -ab 448k -dialnorm -24 -dsur_mode 0 -original 1 -dmix_mode 2 -channel_layout 63 result.ac3
ffmpeg version N-90802-g9f9f56e679 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 7.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth
  libavutil      56. 15.100 / 56. 15.100
  libavcodec     58. 19.100 / 58. 19.100
  libavformat    58. 13.100 / 58. 13.100
  libavdevice    58.  4.100 / 58.  4.100
  libavfilter     7. 19.100 /  7. 19.100
  libswscale      5.  2.100 /  5.  2.100
  libswresample   3.  2.100 /  3.  2.100
  libpostproc    55.  2.100 / 55.  2.100
Guessed Channel Layout for Input Stream #0.3 : mono
Guessed Channel Layout for Input Stream #0.4 : mono
Guessed Channel Layout for Input Stream #0.5 : mono
Guessed Channel Layout for Input Stream #0.6 : mono
Guessed Channel Layout for Input Stream #0.7 : mono
Guessed Channel Layout for Input Stream #0.8 : mono
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'BBC_Short_HDR.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 512
    compatible_brands: qt
    encoder         : Lavf58.2.103
  Duration: 00:00:40.13, start: 0.000000, bitrate: 730854 kb/s
    Stream #0:0(eng): Video: prores, 1 reference frame (apch / 0x68637061), yuv422p10le(progressive), 3840x2160, 719412 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 12800 tbn, 12800 tbc (default)
    Metadata:
      handler_name    : DataHandler
      encoder         : Apple ProRes 422 HQ
      timecode        : 09:59:30:00
    Stream #0:1(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:2(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:3(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:4(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:5(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:6(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:7(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:8(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:9(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:10(eng): Data: none (tmcd / 0x64636D74)
    Metadata:
      handler_name    : DataHandler
      timecode        : 09:59:30:00
File 'result.ac3' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:1 -> #0:0 (pcm_s24le (native) -> ac3 (native))
Press [q] to stop, [?] for help
[Parsed_pan_0 @ 00000232858aac00] This syntax is deprecated. Use '|' to separate the list items ('5.1(side)|c2=FL|c3=FR|c4=FC|c5=LFE|c6=SL|c7=SR' instead of '5.1(side):c2=FL|c3=FR|c4=FC|c5=LFE|c6=SL|c7=SR')
[AVFilterGraph @ 0000023285cc6900] Error initializing filter 'pan' with args '5.1(side):c2=FL|c3=FR|c4=FC|c5=LFE|c6=SL|c7=SR'
Error reinitializing filters!
Failed to inject frame into filter network: Invalid argument
Error while processing the decoded data for stream #0:1
Conversion failed!