You can easily extract audio from video files such as avi, mpg, even flv! into mp3 uses either mplayer or ffmpeg. You can even record online stream into mp3, such as stream from radio cast.
Lets begin with mplayer. To extract audio from video files, use -dumpaudio option and specified the output filename with -dumpfile
mplayer -dumpaudio nodame_theme.flv -dumpfile nodame_theme.mp3
Okay check out the output:
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