[FFmpeg-devel] [PATCH 5/5] avcodec/mpeg4videodec: duplicate the last decoded frame when the last coded frame was skipped

[James Almer]

On 12/4/2022 6:52 PM, James Almer wrote:
> This ensures the video stream duration is not lost after decoding.
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>   libavcodec/h263dec.c   | 13 +++++++++++++
>   libavcodec/mpegvideo.h |  1 +
>   2 files changed, 14 insertions(+)
> 
> diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
> index ac7a8521e5..0a2d7487a8 100644
> --- a/libavcodec/h263dec.c
> +++ b/libavcodec/h263dec.c
> @@ -430,6 +430,18 @@ int ff_h263_decode_frame(AVCodecContext *avctx, AVFrame *pict,
>                   return ret;
>               s->next_picture_ptr = NULL;
>   
> +            *got_frame = 1;
> +        } else if (s->skipped_last_frame && s->current_picture_ptr) {
> +            /* Output the last picture we decoded again if the stream ended with
> +             * an NVOP */
> +            if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0)
> +                return ret;
> +            /* Copy props from the last input packet. Otherwise, props from the last
> +             * returned picture would be reused */
> +            if ((ret = ff_decode_frame_props(avctx, pict)) < 0)
> +                return ret;
> +            s->current_picture_ptr = NULL;
> +
>               *got_frame = 1;
>           }
>   
> @@ -500,6 +512,7 @@ retry:
>               s->extradata_parsed = 1;
>           }
>           ret = ff_mpeg4_decode_picture_header(avctx->priv_data, &s->gb, 0, 0);
> +        s->skipped_last_frame = (ret == FRAME_SKIPPED);
>       } else if (CONFIG_H263I_DECODER && s->codec_id == AV_CODEC_ID_H263I) {
>           ret = ff_intel_h263_decode_picture_header(s);
>       } else if (CONFIG_FLV_DECODER && s->h263_flv) {
> diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
> index 6440b906b1..42275953b9 100644
> --- a/libavcodec/mpegvideo.h
> +++ b/libavcodec/mpegvideo.h
> @@ -175,6 +175,7 @@ typedef struct MpegEncContext {
>       Picture *last_picture_ptr;     ///< pointer to the previous picture.
>       Picture *next_picture_ptr;     ///< pointer to the next picture (for bidir pred)
>       Picture *current_picture_ptr;  ///< pointer to the current picture
> +    int skipped_last_frame;
>       int last_dc[3];                ///< last DC values for MPEG-1
>       int16_t *dc_val_base;
>       int16_t *dc_val[3];            ///< used for MPEG-4 DC prediction, all 3 arrays must be continuous

Will apply.