Official URLs:
http://www.3gpp.org/specifications
ftp://ftp.3gpp.org/specs/2012-09
External overview:
http://www.quintillion.co.jp/3GPP/3gpp_rel8.html
I did not yet read any, so I can't tell you which of them are relevant. I only remember that there was some slight trouble with some "Freeware" 3GPP converter (stealthly using a renamed ffmpeg, with some ambushing registration feature), which was able to create files some mobile players could not play, and it was a quite "usual" combination (MPEG4-ASP with MP3 or AAC-LC, I don't remember exactly...)