mp3 -tutorial

I've tried to find a good mp3 - tutorial, but had no luck with it.
I would be very grateful if somebody would send me a link to some mp3 tutorial.

Are you looking for how to use them or what? If you're looking to make an encoder or something that's a different story. Give an example of what you're trying to do.

There are some open-source MP3 codecs. Some come with a lot of info.

One of them:
bladeenc.mp3.no/

Well...
I'm trying to make a mp3-player,
with a visualisator (like in the Media Player, but it would be in 3D).