There are times when converting a video to mp3 is just needed because you needed just the audio. There are, for example, Youtube videos that are karaokes or videokes. If you love singing, you know just what they are. You have the lyrics already and may have memorized it even, all you needed now is the audio accompaniment so that you can sing with it even when the file is in your mobile phone. It is a good way to practice whenever you want to and where ever you think it is possible. The vlc media player can do just that by "Saving As" to mp3. Simple.