Re: [FFmpeg-devel] [PATCH] av1dec: handle dimension changes via get_format

[Dave Airlie <airlied@gmail.com>]

On Thu, 22 Jun 2023 at 02:36, James Almer <jamrial@gmail.com> wrote:
>
> On 6/20/2023 8:36 PM, airlied@gmail.com wrote:
> > From: Dave Airlie <airlied@redhat.com>
> >
> > av1-1-b8-03-sizeup.ivf on vulkan causes gpu hangs as none of the
> > images get resized when dimensions change, this detects the dim
> > change and calls the get_format to reinit the context.
> > ---
> >   libavcodec/av1dec.c | 12 ++++++++----
> >   1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
> > index e7f98a6c81..1cec328563 100644
> > --- a/libavcodec/av1dec.c
> > +++ b/libavcodec/av1dec.c
> > @@ -721,6 +721,7 @@ static av_cold int av1_decode_free(AVCodecContext *avctx)
> >   }
> >
> >   static int set_context_with_sequence(AVCodecContext *avctx,
> > +                                     int *dim_change,
> >                                        const AV1RawSequenceHeader *seq)
> >   {
> >       int width = seq->max_frame_width_minus_1 + 1;
> > @@ -753,6 +754,8 @@ static int set_context_with_sequence(AVCodecContext *avctx,
> >           int ret = ff_set_dimensions(avctx, width, height);
> >           if (ret < 0)
> >               return ret;
> > +        if (dim_change)
> > +            *dim_change = 1;
> >       }
> >       avctx->sample_aspect_ratio = (AVRational) { 1, 1 };
> >
> > @@ -859,7 +862,7 @@ static av_cold int av1_decode_init(AVCodecContext *avctx)
> >               goto end;
> >           }
> >
> > -        ret = set_context_with_sequence(avctx, seq);
> > +        ret = set_context_with_sequence(avctx, NULL, seq);
> >           if (ret < 0) {
> >               av_log(avctx, AV_LOG_WARNING, "Failed to set decoder context.\n");
> >               goto end;
> > @@ -1202,7 +1205,7 @@ static int av1_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
> >           CodedBitstreamUnit *unit = &s->current_obu.units[i];
> >           AV1RawOBU *obu = unit->content;
> >           const AV1RawOBUHeader *header;
> > -
> > +        int dim_change = 0;
> >           if (!obu)
> >               continue;
> >
> > @@ -1220,7 +1223,8 @@ static int av1_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
> >
> >               s->raw_seq = &obu->obu.sequence_header;
> >
> > -            ret = set_context_with_sequence(avctx, s->raw_seq);
> > +            dim_change = 0;
> > +            ret = set_context_with_sequence(avctx, &dim_change, s->raw_seq);
> >               if (ret < 0) {
> >                   av_log(avctx, AV_LOG_ERROR, "Failed to set context.\n");
> >                   s->raw_seq = NULL;
> > @@ -1229,7 +1233,7 @@ static int av1_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
> >
> >               s->operating_point_idc = s->raw_seq->operating_point_idc[s->operating_point];
> >
> > -            if (s->pix_fmt == AV_PIX_FMT_NONE) {
> > +            if (s->pix_fmt == AV_PIX_FMT_NONE || dim_change) {
> >                   ret = get_pixel_format(avctx);
>
> Dimensions can change between frames without a seq header showing up to
> change the max_width/height values. get_pixel_format() would need to be
> called on frame headers instead.

It can but my reading of the spec is that it is illegal to go beyond
the max in sequence header.

6.8 Frame header OBU semantics
6.8.4 Frame size semantics

"
It is a requirement of bitstream conformance that frame_width_minus_1
is less than or equal to max_frame_width_minus_1.
It is a requirement of bitstream conformance that frame_height_minus_1
is less than or equal to max_frame_height_minus_1.
"

Dave.
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