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

Jun Zhao mypopydev at gmail.com
Fri Dec 2 10:15:10 EET 2016

On 2016/12/1 19:03, wm4 wrote:
> 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.
> _

I don't think software dec/enc/filter have the crop issue, so I guess
we just need a general solution for HWAccel dec/enc/hwcontext_xxx_filter.
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