MP3 to WAV (resolved)

I figured out how to encode from WAV to MP3 but now I want to do the reverse, to decode.

But the problem now is that I don't know how to find out the MP3 format, like the frequency and how many channels and how many KBits per second ?

How can I find that out from the MP3 data ?

http://www.wotsit.org/search.asp?page=5&s=music

That was easy :)

Thanks !