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My audio container is M4A, but codec is AAC. When I try to convert it into MP3 I got an error:

afconvert ~/Desktop/src.m4a -f MPG3 -d .mp3 ~/Desktop/dst.mp3
Error: ExtAudioFileSetProperty ('cfmt') failed ('fmt?')

enter image description here

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up vote 0 down vote accepted

Could you just use ffmpeg?

ffmpeg -i file.m4a -aq 2 file.mp3

-aq 2 corresponds to -V2 in lame. ffmpeg preserves tags but not cover art.

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Unfortunately there is no ffmpeg installed on OSX so I have to figure out what is wrong with afconvert. Can't install macports or make from sources on that machine. – Pablo Nov 2 '13 at 21:44
@Pablo You don't have to. On the FFmpeg download page there's a static build that you can just execute. If you do a -c:v copy it might copy the cover art over as well. – slhck Nov 3 '13 at 7:43

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