avconv -i input.mp4 output.wav
Encode wav to mp3
lame --preset standard input.wav output.mp3
For different mp3 quality use another preset mode. Display all preset modes with: lame --preset help
Update mp3 with ID3 tag
eyeD3 --encoding=utf8 -a "Author" -t "Title" -A "Album" --add-image image.jpg:FRONT_COVER input.mp3
Copy out audio from mp4 file as AAC
avconv -i input.mp4 -c:a copy output.aac
