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.
See [L1 ] and [L2 ] for some additional information on the subject.
Note that MP3 is a lossy compression format.
A student project from the National University of Singapore features C++ code for decoding and encoding MPEG video packets, with Tcl bindings via OTcl: [L3 ]