[FFmpeg-devel] [PATCH] movenc: support GPMF track (gpmd) remuxing

Clément Bœsch u at pkh.me
Fri Jul 21 17:09:29 EEST 2017

On Fri, Jul 21, 2017 at 03:03:19PM +0100, Derek Buitenhuis wrote:
> On 7/21/2017 2:55 PM, Clément Bœsch wrote:
> > It's basically the same layout for every stsd sample description. Check
> > the other tags that extend that layout, the also have that data ref idx to
> > 1. I think I copied from the rtp code, but it's the same for the other as
> > well. This gpmd atom just extends the stsd sample description with a
> > reserved 32-bit value.
> How very useful.

Well, I didn't write the ISO specifications.

If you're refering to the reserved 32-bit value, I suppose it's meant to
allow extensions in the future. Typically it could be reused as a version
or version+flags, which would define more fields, who knows. It's probable
the presence of that field is necessary for some players, so it had to be
present in the first place.

Clément B.
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