On Tue, May 7, 2024 at 10:22 PM Mark Thompson <s...@jkqxz.net> wrote:
>
> On 07/05/2024 07:00, David Rosca wrote:
> > If there are missing references, h264 decode does error concealment
> > by copying previous refs which means there will be duplicated surfaces
> > and this code would try to merge them instead of correctly appending
> > to DPB. Make sure the fields were actually merged before early return.
> > ---
> > libavcodec/vaapi_h264.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavcodec/vaapi_h264.c b/libavcodec/vaapi_h264.c
> > index b47531ce1c..c62a320e97 100644
> > --- a/libavcodec/vaapi_h264.c
> > +++ b/libavcodec/vaapi_h264.c
> > @@ -112,8 +112,9 @@ static int dpb_add(DPB *dpb, const H264Picture *pic)
> > } else {
> > va_pic->BottomFieldOrderCnt =
> > temp_va_pic.BottomFieldOrderCnt;
> > }
> > + return 0;
> > }
> > - return 0;
> > + break;
> > }
> > }
> >
>
> I agree that the old code did nasty things, but can you explain a bit more
> about the reasoning for what you've got now?
>
> I'm thinking that given duplication a top field could appear twice, so you'd
> want to merge twice if you have the matching bottom field.
Right, that may be possible.
Also I've looked at vdpau code and there it checks frame_num (in
addition to surface) when searching for the other field, which seems
better to avoid trying to merge when it should not. Posted v2 with
this change + multiple merge.
Thanks,
David
>
> Thanks,
>
> - Mark
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