Code: apt-get install mplayer lame mplayer file.flv -ao pcm -vo null lame audiodump.wav file.mp3 First command will generate audiodump.wav WAV PCM file (you can change it's name, see mplayer man), second is LAME mp3 encoder - convert it to mp3.
apt-get install mplayer lame mplayer file.flv -ao pcm -vo null lame audiodump.wav file.mp3