[FFmpeg-devel] [PATCH] mp4 and ipod metadata

[Richard Sotke]

Am Freitag, 13. Juni 2008 08:54:14 schrieb Baptiste Coudurier:
> > Michael Niedermayer wrote:
> > Besides, its offtopic but we need to fix our muxer to add these "tracks"
> > one day a well. I wonder how hard it is to generate some empty dummy
> > tracks to conform to the spec ...
>
> Yeah, I'd love to put "mp42" as major brand to our mp4, what we need is
> "iods" atom and hdlr osdm/sdsm bifs tracks.

You could add a minimal MPEG-4 Systems support, like it is done by ISMA 1.01. 
This would work for files with one audio and video object.

You can cretae a sample file with "MP4Box -isma yourFile.mp4". To take a look 
at the MPEG-4 Systems information, you can dump it with "MP4Box -bt 
yourFile.mp4" or "MP4Box -xmt yourFile.mp4"

The pixelWidth and pixelHeight of the scene, in the IOD box/atom, should be 
set to the dimension of the video object (visual stream/track). If the visual 
stream has an pixel aspect ratio unequal 1:1, the pixelWidth and pixelHeight 
in the IOD, should be set to the at playback scaled dimension. 

For files with more than one audio object (audio stream/track), an other 
default BIFS/OD track would be possible. The scene(BIFS track) would need to 
be adjusted, so that you can switch between the audio objects. In the OD 
stream additional object descriptors for the other audio streams would be 
needed.

But for MP4 files with more than one audio and video stream a tool like 
MP4MenuGUI ( http://forum.doom9.org/showthread.php?t=117574 ) is could be 
more suitable.

Regards
Richard