ffmpeg -i ${INPUT}.m4a -c:v copy -c:a libmp3lame \
-q:a 0 ${OUTPUT}.mp3The -q:a parameters correspond to LAME’s -V option, so 0 is the highest quality and 9 is the lowest quality. While everyone says to use 3 or 4 for this parameter, in my experience even using 0 will often result in a smaller file than an m4a original. (What’s up with that? I thought that m4a was supposed to be more efficient than mp3?)