Convert Video Audio to MP3 with FFmpeg
To rip the audio from a video file and encode it to mp3:
ffmpeg -i MOVIE.webm -q:a 0 AUDIO.mp3
-q: sets fixed quality scale (VBR) to the selected stream, which is
a (all audio streams), and passes
0 to the audio codec (LAME) which interprets it as "highest quality".
9 would be "lowest quality".