"mplayer -dumpaudio GummyBearSong.avi -dumpfile gummybear.mp3"
"GummyBearSong.avi" is the source video, in the example above it was 30 MB
"gummybear.mp3" is the output audio file (in mp3 format), was about 3 MB in size
and surprisingly it took 1 second only!!
I think it runs on other video formats as well, as the source article was working on an "flv" file.