Using FFMPEG to split a 16 channel audio input source into 4 seperate 4 channel audio feeds for streaming

Question

I hope someone can help

I am currently trying to split a 16ch Dante audio feed from a separate machine into 4 different audio streams that I can use to then TX via RTMP to Wowza for MPEG-DASH encoding, at present i am just trying to split them into files, I will add the RTMP streaming later.

The biggest issue I am encountering at current is that FFMPEG is returning me this error from my input string

Filter channelsplit:WR has an unconnected output

here is my current input string

ffmpeg -f dshow -i audio="Dante Via Receive (Dante Via)" -filter_complex "[0:a]channelsplit=channel_layout=hexadecagonal[FL][FR][FC][BL][BR][BC][SL][SR][TFL][TFC][TFR][TBL][TBC][TBR][WL][WR]" -map "[FL][FR][FC][BL]" 1-4.wav -map "[BR][BC][SL][SR]" 5-8.wav -map "[TFL][TFC][TFR][TBL]" 9-12.wav -map "[TBC][TBR][WL][WR]" 13-16.wav

and here is the full FFMPEG output

ffmpeg version git-2019-12-26-b0d0d7e Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.2.1 (GCC) 20191125
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --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-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 37.100 / 56. 37.100
  libavcodec     58. 65.100 / 58. 65.100
  libavformat    58. 35.101 / 58. 35.101
  libavdevice    58.  9.101 / 58.  9.101
  libavfilter     7. 69.101 /  7. 69.101
  libswscale      5.  6.100 /  5.  6.100
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, dshow, from 'audio=Dante Via Receive (Dante Via)':
  Duration: N/A, start: 103082.790000, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
File '1-4.wav' already exists. Overwrite? [y/N] y
File '5-8.wav' already exists. Overwrite? [y/N] y
File '9-12.wav' already exists. Overwrite? [y/N] y
File '13-16.wav' already exists. Overwrite? [y/N] y
Filter channelsplit:WR has an unconnected output 

I'm also getting the issue where FFMPEG is guessing that the channel count is stereo, which is incorrect but i'm having problems figuring out how to define the input stream as 16ch's of audio

Any help with this would be greatly recieved

Cheers

M

Answer 1

ffmpeg -f dshow -channels 16 -i audio="Dante Via Receive (Dante Via)" -filter_complex "[0:a]channelmap=0|1|2|3[1-4];[0:a]channelmap=4|5|6|7[5-8];[0:a]channelmap=8|9|10|11[9-12];[0:a]channelmap=12|13|14|15[13-16]" -map "[1-4]" 1-4.wav -map "[5-8]" 5-8.wav -map "[9-12]" 9-12.wav -map "[13-16]" 13-16.wav

• Try adding the -channels 16 dshow input option.
• Filter output labels can't be combined in -map, so do all mixing with filters and give each -map a single label.
• channelsplit only outputs channels as individual streams, and it does not mix multiple channels into a single stream, so channelmap is used instead.
• I don't have dshow so I couldn't test this.