72ad415f___MPEG_21_Multimedia_Framework__Description
[Part#] 9-FF [Description] 
An MPEG-21 Digital Item can be a complex collection of information. Both still and dynamic media (e.g. images and movies) can be included, as well as Digital Item information, meta-data, layout information, and so on. It can include both textual data (e.g. XML) and binary data (e.g. an MPEG-4 presentation or a still picture). For this reason, the MPEG-21 file format will inherit several concepts from MP4, in order to make ‘multi-purpose’ files possible. A dual-purpose MP4 and MP21 file, for example, would play just the MPEG-4 data on an MP4 player, and would play the MPEG-21 data on an MP21 player.
Information Technology — MPEG-21 Multimedia Framework
Description