[Mp4-tech] Necessity of IODS

[Praveen Singh]

Hi Richard,
thanks a ton.
I have the 3gp file format parsing library with me. Now to make it able to
parse mp4 files, i need to add "iods" parsing.
But how it will be able to parse mp4 file that do not have "iods" box? Are
the mp4 files without "iods" boxes (sub part of a presentation) are exactly
same as 3gp files(apart from brand etc.)? Can they be parsed by 3gp parser?
And can u tell me where i will get the mp4 video files having iods box.
I have downloaded more than 50 video files but none of them contains the
iods box.
Praveen
-----Original Message-----
From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org]On Behalf Of Richard Sotke
Sent: Wednesday, January 23, 2024 2:24 PM
To: mp4-tech lists.mpegif.org
Subject: Re: [Mp4-tech] Necessity of IODS
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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