hehehe...
Anyways, I don't need the (licensed) encoding/decoding itself (avoiding the name mpeg/mp3/whatever here otherwise I'll make a mistake again
) I needed the fileformat: where are the tags stored, what are the first bytes indicating, etc... etc...
=> found plenty of info on sites like
http://www.wotsit.org/,
http://www.filespecs.com/, ...
On the other part, I needed a program that could compare the uncompressed audio streams of two mp3-files easly (without converting the mp3 first to a PCM, then comparing those PCM's, etc... etc...) (<= dont say I use the term wrong again
)
=> still didn't try out SoundForge, so I dunno...
EDIT: by this time I've indeed found plenty of info about the MPEG audio format and everything I need (including the official licensed papers)...