[Mp4-tech] Necessity of IODS
Richard Sotke
richard sotke.de
Wed Jan 23 09:53:35 EST 2008
Am Mittwoch, 23. Januar 2008 06:49:19 schrieb Praveen Singh:
> Hi all,
> I am working on mp4 parser library.
> When standards says that mp4 follows the Object Descriptor Framework and
> Initial object descriptor serves as the starting point of this framework,
> why the "iods" box/atom is not Mandatory in mp4 files?
You can have a MP4 file which is a Sub-part of a presentation. In the "iods"
specification (ISO/IEC 144496-14) are some file types case lisetd, with
comment if this is a MP4 file or not(free-format). Summary: to have a MP4
Format file there have to be an Object Descriptor.
You can compare this with the "ctts" box, which is only needed with B-Frames.
The "ctts" box is also not mandatory.
>
> How the Object Descriptor Framework is maintained in case of absence of
> "iods" box in mp4 file?
A presentation should always be initialized via an IOD, as far as I know.
>
> Thanks in anticipation
> Praveen
Regards
Richard
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