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

[Michael Niedermayer]

On Wed, Nov 30, 2016 at 04:56:01PM +0100, wm4 wrote:
> On Wed, 30 Nov 2016 16:40:53 +0100
> Michael Niedermayer <michael at niedermayer.cc> wrote:
> 
> > On Wed, Nov 30, 2016 at 02:18:36PM +0100, wm4 wrote:
> > > On Wed, 30 Nov 2016 11:08:10 +0000
> > > Mark Thompson <sw at jkqxz.net> wrote:
> > >   
> > > > On 30/11/16 02:20, Jun Zhao wrote:  
> > > > > From 20bedd18213420c77d5e8a26fbe741d8d204ac10 Mon Sep 17 00:00:00 2001
> > > > > From: Jun Zhao <jun.zhao at intel.com>
> > > > > Date: Tue, 29 Nov 2016 14:14:25 +0800
> > > > > Subject: [PATCH] lavc/vaapi_h26[45]: add crop info support in vaapi_h26[4,5]
> > > > >
> > > > > add crop information support in vaapi_h26[4,5] hwaccel decode,
> > > > > and align h264/hevc software decoder. After this fix, FATE test
> > > > > h264-conformance-cvfc1_sony_c/hevc-conformance-CONFWIN_A_Sony_1
> > > > > will pass in i965/SKL.
> > > > >
> > > > > Signed-off-by: Wang, Yi A <yi.a.wang at intel.com>
> > > > > Signed-off-by: Jun Zhao <jun.zhao at intel.com>
> > > > > ---
> > > > >  libavcodec/h264dec.c        | 13 +++++++++++++
> > > > >  libavcodec/hevc_refs.c      |  7 +++++++
> > > > >  libavutil/hwcontext.h       |  6 ++++++
> > > > >  libavutil/hwcontext_vaapi.c |  1 +
> > > > >  4 files changed, 27 insertions(+)    
> > > > 
> > > > No.  Top/left cropping needs a more general approach, not hacks in specific decoders/hwcontexts.
> > > > 
> > > > Among other things:
> > > > - The hardware frame context is owned by the user, you can't edit it like this from inside the decoder.
> > > > - It can't be per-frame-context anyway, because multiple streams can be decoded into the same frame context.
> > > > - More components need to be aware of it: the scale filters definitely should be (at <https://git.libav.org/?p=libav.git;a=blob;f=libavfilter/vf_scale_vaapi.c;h=50be68eee07374a78bba1eed8850c3ab9e019fe6;hb=HEAD#l291>, in VAAPI, similarly for the other hardware APIs).  Other components can probably ignore it (with docs saying you should put it through the relevant scale filter if you want correctly-cropped images), but we should make that decision explicitly.
> > > > - Messing with pointers/sizes on frame upload/download has issues with APIs which can only transfer whole frames - see the comment at <http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavutil/hwcontext.h;h=785da090b3fc4b4e91f989370ea4606c79bae823;hb=HEAD#l321>.  (That was written with VDPAU in mind, there are likely others.)
> > > > 
> > > > As wm4 notes in another reply, this ends up pointing to some sort of cropping information associated with the AVFrame which all interested components can then read.
> > > > 
> > > > I know several people have expressed interest in this problem: given that, it's probably a good idea to have some discussion first and decide roughly what the result should look like before writing a lot of code for it.  
> > > 
> > > I've always argued for having a cropping rectangle directly in AVFrame,
> > > but the idea was never popular.  
> > 
> > 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 ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Modern terrorism, a quick summary: Need oil, start war with country that
has oil, kill hundread thousand in war. Let country fall into chaos,
be surprised about raise of fundamantalists. Drop more bombs, kill more
people, be surprised about them taking revenge and drop even more bombs
and strip your own citizens of their rights and freedoms. to be continued
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