[FFmpeg-devel] [PATCH] lavc/vp9: set update_map to 0 when segmentation.enabled is 0

[Philip Langdale]

On Wed, 22 May 2024 11:10:31 -0400
"Ronald S. Bultje" <rsbultje at gmail.com> wrote:

> Hi,
> 
> On Wed, May 22, 2024 at 10:36 AM Hendrik Leppkes <h.leppkes at gmail.com>
> wrote:
> 
> > On Thu, Feb 29, 2024 at 7:19 AM llyyr <llyyr at yukari.in> wrote:  
> > >
> > > segmentation.update_map is never reset to 0 on a new frame, and
> > > retains the value from the previous frame. This bugs out a bunch
> > > of hwaccel drivers when segmentation.enabled is 0 but update_map
> > > isn't because they don't ignore values behind switches. We also
> > > do this for vp8* so this commit is just mirroring the vp8 logic.
> > >
> > > This fixes an issue with certain samples** that causes blocky
> > > artifacts with vaapi and d3d11va (as far as known hwaccel drivers
> > > go). Mesa worked around*** this by ignoring this field if
> > > segmentation.enabled is 0, but d3d11va still doesn't work.
> > >
> > > *  
> > https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/HEAD:/libavcodec/vp8.c#l811
> >  
> > > ** https://github.com/mpv-player/mpv/issues/13533
> > > ***
> > > https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27816
> > >
> > > Signed-off-by: llyyr <llyyr at yukari.in>
> > > ---
> > >  libavcodec/vp9.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/libavcodec/vp9.c b/libavcodec/vp9.c
> > > index 855936cdc1c7..4a628625131e 100644
> > > --- a/libavcodec/vp9.c
> > > +++ b/libavcodec/vp9.c
> > > @@ -717,6 +717,8 @@ static int decode_frame_header(AVCodecContext
> > > *avctx, s->s.h.segmentation.feat[i].skip_enabled =  
> > get_bits1(&s->gb);  
> > >              }
> > >          }
> > > +    } else {
> > > +        s->s.h.segmentation.update_map = 0;
> > >      }
> > >
> > >      // set qmul[] based on Y/UV, AC/DC and segmentation Q idx
> > > deltas
> > >
> > > base-commit: d263fce2b209e86a5a1e8f1b6aa33430ecc2c187
> > > --  
> >
> > Change LGTM.
> > I was debugging the same issue today, and found the same problem
> > with some hwaccels not properly ignoring update_map when
> > segmentation is disabled.
> >
> > Will apply soon if there are no further comments.
> >  
> 
> Is fine, please apply.
> 

Another LGTM. We've been seeing this reported on the mpv side as well.

--phil