At first, the Moving Picture Expert Group (MPEG) had the plan to define a video coding system for High Definition Television (HDTV) apllications. This coding system should be called MPEG-3. However, MPEG realised that the tools that are needed for the video coding of HDTV were already contained in the MPEG-2 system for video coding. So, the development of MPEG-3 was stopped and the work was continued within MPEG-2.
Sometimes, the term MPEG-3 is, improperly, used for the MPEG-1/2 Layer III (MP3) audio coding system.