M4A to wav

 for nam in *.M4A; do nice mplayer -ao pcm "$nam" -ao pcm:file="$nam.wav" done

wav to mp3

 for nam in *.wav; do nice lame -h "$nam" "$nam.mp3" ;done


reference
http://gimpel.gi.funpic.de/wiki/index.php?title=Howto:convert_aac/mp4_to_wav/mp3/ogg_on_Linux
posted by citadel