[Mp4-tech] Necessity of IODS

[Richard Sotke]

Am Donnerstag, 24. Januar 2008 06:05:44 schrieb 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.
What exactly do you want to support? 
Do you want playback most common files around? Most files around don't use the 
Object Descriptor Framework, so if your strict, they are not MP4 
files(ISO/IEC 14496-14).
Or do you plan to use features based at the Object Descriptor Framework?  
> 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)
Forget about MP4 files which are a sub part of a presentation for now,
they are not used alone. 
> are exactly  same as 3gp files(apart from brand etc.)? Can they be parsed by 
>3gp parser?
Dependent on your 3gp parser you should be able to archive your goal, parsing 
of ISO base media format compatible files(ISO/IEC 14496-12), with it.  
>
> 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.
You can create MP4 files with IOD with MP4Box from 
http://gpac.sourceforge.net/ . Simple ISMA 1.0 compatibele files created with 
MP4Box should containe an IOD.
You can also take a look at libgpac which comes with support for the Object 
Descriptor Framework, but I guess it is not what your are looking for. 
The Documentatiion at GPAC may be from interest too.
>
> Praveen

Regards
Richard 
>
> -----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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