I am converting files from one format to another using afconvert in OS X. The files are stereo and now I am trying to have them come out as mono by mixing the two channels into one. There seems to be an option to downmix channels using the option --mix, but I am not sure how it works. Whatever I try, I only get stereo output.

Update: I installed ffmpeg using homebrew, and added this step to my script: ffmpeg -i file.wav -ac 1 file_mono.wav

It seems is ok, but I haven't confirmed yet that this is really mixing, and not just dropping of channels. works.

  • This is offtopic here as it is not about Sound Design - it may be on topic on one of the other SE sites, but I can't think which. – Rory Alsop Apr 30 '14 at 14:39
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    Well... a lot of the questions on Stack Overflow aren't related to stack overflows. – Jonny May 1 '14 at 1:46

I was going to suggest ffmpeg. ffmpeg -i file.wav -ac 1 output.wav should definitely work.

If you want to check the number of channels that the audio output file, you can drop it into audacity, which by default creates one track per channel.


to specify little-endian (intel) integer 16 or 24 bit wav file:

afconvert -d LEI16 -c 1 --mix input_file.wav output_file.wav


afconvert -d LEI24 -c 1 --mix input_file.wav output_file.wav
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    I assume you mean that "-c 1 --mix" makes it really mix and not drop channels, so +1 for an afconvert only solution – Jonny Apr 16 '14 at 14:47
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    i did check that this is the case and it sounds like this is the case. – georgi Apr 16 '14 at 22:07

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