MP3 is the name (and frequently the file extension) for files containing data formatted in a commonly used format. It is used to digitally represent audio files compressed using the MPEG audio layer 3 compression technology.
Note that MP3 is a lossy compression format.
See MP3 (wikipedia.org) for additional information on the subject.
Reassembling and Decoding MPEG-1 Video Packets (comp.nus.edu.sg) is a student project from the National University of Singapore, features C++ code for decoding and encoding MPEG video packets, with Tcl bindings via OTcl