If you are ever in need of just the audio portion of an .mp4 file, here are two commands and a loop to put the audio into an .mp3 file.
#!/bin/sh for file in *.mp4 do echo $file "/cygdrive/c/Program Files/MPlayer/mplayer.exe" -ao pcm $file \ -ao pcm:file=tmp.wav lame -h tmp.wav `basename $file .mp4`.mp3 done
(You might need to customize the path to mplayer.exe. I used an explicit path as I was on Windows and needed to pull in a specific cygwin dll for this executable. You may or may not have this issue.)