[Mp4-tech] automatic tagging and gapless playback for MP4 files

[AVARO Olivier FTRD/DIH/REN]

Dear all,
There are a couple a ways to have metadata associated to MPEG-4 content.
On the  way to express metadata MPEG defines:
- OCI (Object Content Information) : simple and straightforward. Defined in 14496-1 before MPEG-7 standard was here. The main content descriptors are: content classification descriptors, keyword descriptors, rating descriptors, language descriptors, textual descriptors, and descriptors about the creation of the content. OCI association is fully defined in 14496-1. 
- MPEG-7 : Much more powerfull expression of description (see MPEG-7 description on the MPEG Web page for more info. or the MPEG-7 standard ISO/IEC 15938). 
- MPEG-21 also could be seen for some part as metadata but this goes beyond the scope of the thread.
On the way to associated metadata to content:
- OCI or MPEG-7 descriptors can be included directly in the related object descriptor or elementary stream descriptor or, if it is time variant, it may be carried in an elementary stream by itself. MPEG-7 association through object descriptor is not yet fully defined though.
- Extensions of the MP4 file format structure under investigation in MPEG allows association of static metadata to content. Use of MPEG-7 (and support of other type of metadata) will be there fully supported. This is documented in N5789 from MPEG meeting in Trondheim (July 2003).
A complete and simple example to use all this is provided in MPEG doc. N5723 from Trondheim (Importing MP3 into an MPEG-4 World). It provides a mapping from ID3V1.1 Tags to MPEG-7 and its packing in MP4.
Kind regards,
Olivier