[FFmpeg-devel] [PATCH v2 1/3] avcodec/snowenc: AV_CODEC_CAP_ENCODER_RECON_FRAME support

[James Almer]

On 3/19/2023 4:42 PM, Michael Niedermayer wrote:
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>   libavcodec/snowenc.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/snowenc.c b/libavcodec/snowenc.c
> index 658684c575..5fb5906ed8 100644
> --- a/libavcodec/snowenc.c
> +++ b/libavcodec/snowenc.c
> @@ -26,6 +26,7 @@
>   #include "avcodec.h"
>   #include "codec_internal.h"
>   #include "encode.h"
> +#include "internal.h" //For AVCodecInternal.recon_frame
>   #include "me_cmp.h"
>   #include "packet_internal.h"
>   #include "snow_dwt.h"
> @@ -1576,6 +1577,7 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
>   {
>       SnowContext *s = avctx->priv_data;
>       RangeCoder * const c= &s->c;
> +    AVCodecInternal *avci = avctx->internal;
>       AVFrame *pic;
>       const int width= s->avctx->width;
>       const int height= s->avctx->height;
> @@ -1877,6 +1879,10 @@ redo_frame:
>                                      s->encoding_error,
>                                      (s->avctx->flags&AV_CODEC_FLAG_PSNR) ? SNOW_MAX_PLANES : 0,
>                                      s->current_picture->pict_type);
> +    if (s->avctx->flags & AV_CODEC_FLAG_RECON_FRAME) {
> +        av_frame_unref(avci->recon_frame);
> +        av_frame_ref(avci->recon_frame, s->current_picture);
> +    }
>   
>       pkt->size = ff_rac_terminate(c, 0);
>       if (s->current_picture->key_frame)
> @@ -1934,7 +1940,9 @@ const FFCodec ff_snow_encoder = {
>       CODEC_LONG_NAME("Snow"),
>       .p.type         = AVMEDIA_TYPE_VIDEO,
>       .p.id           = AV_CODEC_ID_SNOW,
> -    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
> +    .p.capabilities = AV_CODEC_CAP_DR1 |
> +                      AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE |
> +                      AV_CODEC_CAP_ENCODER_RECON_FRAME,
>       .priv_data_size = sizeof(SnowContext),
>       .init           = encode_init,
>       FF_CODEC_ENCODE_CB(encode_frame),

Testing with the tool from 
https://git.khirnov.net/libav.git/commit/?h=recon&id=d78e17840347abfe10b2bc7e789c60665de56e1f 
(Which i hope will be upstreamed eventually) i get

$ tools/enc_recon_frame_test input.y4m snow flags=+bitexact 10
Checksum mismatch in frame ts=0, plane 0

I don't know if this really matters for snow (is it mean to be 
bitexact?), but it seems the very first frame returned by the 
reconstructed frame API is not the same as the one output by the snow 
decoder. The rest seem to match, though.