MPEG-3
From Just Solve the File Format Problem
MPEG-3 was an MPEG standard for high definition TV (HDTV) which was eventually rolled into MPEG-2, so MPEG-3 didn't end up being put into use as a separate standard.
MPEG-3 is not the same thing as MP3, which is an audio standard based on layer 3 of MPEG-1 and MPEG-2. Nomenclature for the various MPEG-derived formats can be confusing.
