Extracting Audio From Video Files Using FFmpeg
Extracting audio without re-encoding
$ ffmpeg -i video.mp4 -vn -c:a copy output.aac
Extracting audio with re-encoding
$ ffmpeg -i video.mp4 -vn output.mp3
$ ffmpeg -i video.mp4 -vn -c:a copy output.aac
$ ffmpeg -i video.mp4 -vn output.mp3