The days we had to remember dozens of
ffmpeg flags has long gone.
avconv is easy as easy could be.
sudo apt-get install ffmpeg libavcodec-extra-53 libav-tools
To convert video.mp4 to song.mp3, all you need to do is,
avconv -i video.mp4 audio.mp3
It’s so easy it just hurts.
You can of course give
avconv a dozen flags to tune the output to your will, but you just need a simple conversion 90% of the time.