FFMPEG / VLC Demuxen

ffmpeg -i input.mp4 -c:a copy -vn -sn output.m4a

vn and sn disable video and subtitle streams, if there are any. -c:a copy tells it to copy the audio bitstream as-is, without re-encoding the file. This will take less than a few seconds.

https://wiki.videolan.org/Extract_audio/#Extracting_audio_in_original_fo...

Quelle:
http://superuser.com/questions/633752/how-to-extract-an-audio-track-from...