I need to mix the first audio-track into left channel and the second into right. When audio-tracks are stereo, this does the job.

ffmpeg -i 1.mkv -filter_complex "[0:a:0][0:a:1]amerge=inputs=2,pan=stereo|c0<c0+c1|c1<c2+c3[aout]" -map "[aout]" 1.mka

But when there are more channels - how can I do it? Without manually checking number of channels and inserting them myself.



ffmpeg -i 1.mkv -filter_complex "[0:a:0]pan=1c[a0];[0:a:1]pan=1c[a1];[a0][a1]amerge=inputs=2[aout]" -map "[aout]" 1.mka

You'll need either FFmpeg 4.0 or a git build later than Feb 19 2018.

With older versions, you have to use multiple commands to do it

ffmpeg -i 1.mkv -map 0:a:0 -ac 1 a0.wav -map 0:a:1 -ac 1 a1.wav

ffmpeg -i a0.wav -i a1.wav -filter_complex amerge 1.mka
  • 4.0 is the only way? on 3.4 it's impossible? Apr 25 '18 at 17:09
  • Before 4.0, one has to manually supply the rematrixing. Which you want to avoid. But you can use new command.
    – Gyan
    Apr 25 '18 at 17:16

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