[FFmpeg-devel] [PATCH] lavc/vaapi_h26[45]: add crop info support in vaapi_h26[4, 5]

[wm4]

On Wed, 30 Nov 2016 18:25:59 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> > > AVFrame had a pan_scan parameter to store one or more croping
> > > rectangles.
> > > That is now available as side data
> > > 
> > > I remember the intend that this could be used for multiple rectangles
> > > of different sizes for example for storing recommanded display
> > > rectangles for a 4:3 and a 16:9 display device, but it seems only a
> > > single size per frame is supported in the API
> > > 
> > > [...]  
> > 
> > This one is very "special" - I don't know if I'd want to further its
> > existence. What's it used for at all?  
> 
> I only know whats written in the specs, i dont remember having
> investigated what real world files do with it, and my knowledge of the
> specs is many years old so the spec would be a better place than my
> memory of it for further research ...

If we're going to have a crop rectangle, lots of code (including many
video filters) will need to be able to interpret them. Considering
this, the pan scan side data is prohibitively complex. Maybe it
accurately reflects some standard (mpeg1/2 apparently?), but I'd say
it's not simple enough for general use.