[Mp4-tech] Necessity of IODS

[Richard Sotke]

Am Freitag, 25. Januar 2008 12:55:23 schrieb Praveen Singh:
> Hi Richard,
> thanks again, your reply helped me a lot.
> Now i am having following issues:
> 1. For mp4 file, the InitialObjectDescriptor(mp4_IOD_Tag) contains some
> profile and level indications (ISO/IEC 14496-1). 
Beside the profile and level there are information about the track ID of the 
BIFS and OD track.  
> a)What will be the use of that information (levels and profiles) to parse
> the file.
The profiles/level information in the IOD are there, to tell the player what 
have to be supported for a correct presentation of the MP4 file. 
> b)How i can extract trak(BIFS) and trak(OD) inormation from that.
Inside the IOD you get informed where to find the ESDescriptor for the BIFS 
and OD track, you get the track ID.
> c)And where i can get the detail description regerding that.
You can buy the involved standards at http://www.iso.org/iso/store.htm .
ISO/IEC 14496-12  
   ISO/IEC 14496-15
   ISO/IEC 14496-14
      ISO/IEC 14496-1
      ISO/IEC 14496-11
...
But to understand everything it would be a wise decision to search for a 
company, which is involved in this and is giving paid training courses.
I can't help you there any further, I would be more intrested in creating 
content for a player which is using this framework, not in creating a 
player ;) . 
You could try to contact someone from GPAC/ENST, there lib is also available 
with an commercial license.
Or someone from:
http://www.bsoft.info/index.html
http://www.resonate-mp4.com/
http://www.streamezzo.com
But before you do this, you should make clear, if in your use case you need 
all this. You should be able to display most files around, the way it was 
planed, only with the information from the moov box. 
Regards
Richard 
>
> 2. When i converted few 3gp files to mp4 files through MP4Box, the contains
> of "esds' box is got changed(e.g. maxBitrate and avgBitrate fields of
> DecoderConfigDescriptor became 0). I could not understand the reason behind
> that?
Can't reproduce it here, try to cantact someone from GPAC.
>
> Praveen
>
>
> -----Original Message-----
> From: Richard Sotke [mailto:richard sotke.de]
> Sent: Thursday, January 24, 2024 4:21 PM
> To: mp4-tech lists.mpegif.org; Praveen Singh
> Subject: Re: [Mp4-tech] Necessity of IODS
>
> 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
> 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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