This object contains an Object Descriptor or an Initial Object Descriptor.
There are a number of possible file types based on usage, depending on the descriptor:
- Presentation, contains IOD which contains a BIFS stream (MP4 file);
- Sub-part of a presentation, contains an IOD without a BIFS stream (MP4 file);
- Sub-part of a presentation, contains an OD (MP4 file);
- Free-form file, referenced by MP4 data references (free-format);
- Sub-part of a presentation, referenced by an ES URL.
NOTE:
The first three are MP4 files, a file referenced by a data reference is not necessarily an MP4 file, as it is
free-format. Files referenced by ES URLs, by data references, or intended as input to an editing process, need not have
an Object Descriptor Box.
An OD URL may point to an MP4 file. Implicitly, the target of such a URL is the OD/IOD located in the 'iods'
atom in that file.
If an MP4 file contains several object descriptors, only the OD/IOD in the 'iods' atom can be addressed using
an OD URL from a remote MPEG-4 presentation. |
