Re: [FFmpeg-devel] [PATCH] avcodec/vvcdec: fix seeking for open GOP

[James Almer <jamrial@gmail.com>]

On 2/3/2024 7:34 AM, Nuo Mi wrote:
> how to reproduce:
> wget https://media.xiph.org/video/derf/y4m/students_cif.y4m
> vvencapp --input students_cif.y4m --preset faster --output students.266
> MP4Box -add students.266:fps=30000/1001:par=12:11 -new students.mp4

Can't you do this with ffmpeg? mp4 muxing support was added recently, 
and we have a parser to find frame boundaries from raw bitstreams.

> ffplay testudents.mp4
> ---
>   libavcodec/vvc/vvc_refs.c | 6 ++++++
>   libavcodec/vvc/vvc_refs.h | 1 +
>   libavcodec/vvc/vvcdec.c   | 6 ++++++
>   3 files changed, 13 insertions(+)
> 
> diff --git a/libavcodec/vvc/vvc_refs.c b/libavcodec/vvc/vvc_refs.c
> index bf503e429e..e1895d1cca 100644
> --- a/libavcodec/vvc/vvc_refs.c
> +++ b/libavcodec/vvc/vvc_refs.c
> @@ -80,6 +80,12 @@ void ff_vvc_clear_refs(VVCFrameContext *fc)
>               VVC_FRAME_FLAG_SHORT_REF | VVC_FRAME_FLAG_LONG_REF);
>   }
>   
> +void ff_vvc_flush_dpb(VVCFrameContext *fc)
> +{
> +    for (int i = 0; i < FF_ARRAY_ELEMS(fc->DPB); i++)
> +        ff_vvc_unref_frame(fc, &fc->DPB[i], ~0);
> +}
> +
>   static void free_progress(FFRefStructOpaque unused, void *obj)
>   {
>       FrameProgress *p = (FrameProgress *)obj;
> diff --git a/libavcodec/vvc/vvc_refs.h b/libavcodec/vvc/vvc_refs.h
> index cd3b5f5632..eba4422fb4 100644
> --- a/libavcodec/vvc/vvc_refs.h
> +++ b/libavcodec/vvc/vvc_refs.h
> @@ -33,6 +33,7 @@ int ff_vvc_frame_rpl(VVCContext *s, VVCFrameContext *fc, SliceContext *sc);
>   int ff_vvc_slice_rpl(VVCContext *s, VVCFrameContext *fc, SliceContext *sc);
>   void ff_vvc_unref_frame(VVCFrameContext *fc, VVCFrame *frame, int flags);
>   void ff_vvc_clear_refs(VVCFrameContext *fc);
> +void ff_vvc_flush_dpb(VVCFrameContext *fc);
>   
>   typedef enum VVCProgress {
>       VVC_PROGRESS_MV,
> diff --git a/libavcodec/vvc/vvcdec.c b/libavcodec/vvc/vvcdec.c
> index 83ee472ce6..1a050600eb 100644
> --- a/libavcodec/vvc/vvcdec.c
> +++ b/libavcodec/vvc/vvcdec.c
> @@ -922,9 +922,15 @@ static av_cold void vvc_decode_flush(AVCodecContext *avctx)
>   {
>       VVCContext *s  = avctx->priv_data;
>       int got_output = 0;
> +    VVCFrameContext *last;
>   
>       while (s->nb_delayed)
>           wait_delayed_frame(s, NULL, &got_output);
> +
> +    last = get_frame_context(s, s->fcs, s->nb_frames - 1);
> +    ff_vvc_flush_dpb(last);
> +
> +    s->eos = 1;
>   }
>   
>   static av_cold int vvc_decode_free(AVCodecContext *avctx)
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