Hi,
I did a module ages ago for BlitzMax that would read and change ID3 tags. From what I remember, they are made up of frames which each have a header describing what info they hold and the body which contains the actual data.
A main reference I used was this specification, which has the format clearly outlined. Definitely worth reading before attempting to "decode" them.
Another thing to note is that there are 2 main versions of ID3 tags - v1 and (you guessed it) v2. Version 1, iirc, is stored at the end of the file and is really easy to read though the problem is that it only supports basic info like song name/artist. Version 2 supports tonnes more information but is stored at the start of the file in the frame part, and is significantly harder to extract.
A little hint: when I first started to look at file specifications, it helped to download a hex editor (I recommend XVI32) that allows you to view the actual bytes in any file (in this case an MP3 file), to see exactly how it's made, and you can follow it byte-for-byte with the specification.
It was so long ago, that I can't remember much more than that,
Sorry
Seb
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