[FFmpeg-devel] Handling MPEG-4 Custom User Data

Isaac Sutherland isaacsutherland
Wed Aug 19 00:23:45 CEST 2009

On Tue, Aug 18, 2009 at 5:03 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> >
> > However, ffmpeg doesn't appear to allow applications to consume this data,
> > or at least I can't see how it does. decode_user_data in libavcodec/h263.c
> > appears to check for a few data strings (xvid, divx, and ffmpeg identifiers)
> > but throws away unrecognized data. Is providing support for passing custom
> > user data to the user within the scope of ffmpeg? If so, any suggestions on
> > how this should be implemented?
> its sure fine to export user data from the decoder to the user app through
> a AVCodecContext.user_data if someone submits a clean patch.
> Though i am not sure how usefull such a feature would be ...

Thanks for the tip. Unfortunately I do not presently have access to
the ISO spec for MPEG-4, so I do not know exactly what the intent of
the inclusion of user data in the standard was. However, since it was
included, the chances are that somebody would find it useful.

My particular use case is that I need to associate geodata with each
frame of a raw mpeg-4 video stream. The most elegant way to do this on
the encoding end (which does not use ffmpeg) is to send the geodata in
a GOV header along with each frame.

> [...]
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