[FFmpeg-devel] [PATCH 5/6] avcodec/qtrle: return last frame even if unchanged

[James Almer]

On 8/24/2019 3:18 PM, Michael Niedermayer wrote:
> Fixes: Ticket7880
> 
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/qtrle.c        | 30 ++++++++++++++++++++++++++----
>  tests/ref/fate/qtrle-8bit |  1 +
>  2 files changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/qtrle.c b/libavcodec/qtrle.c
> index 2c29547e5a..c22a1a582d 100644
> --- a/libavcodec/qtrle.c
> +++ b/libavcodec/qtrle.c
> @@ -45,6 +45,7 @@ typedef struct QtrleContext {
>  
>      GetByteContext g;
>      uint32_t pal[256];
> +    AVPacket flush_pkt;
>  } QtrleContext;
>  
>  #define CHECK_PIXEL_PTR(n)                                                            \
> @@ -454,11 +455,27 @@ static int qtrle_decode_frame(AVCodecContext *avctx,
>      int has_palette = 0;
>      int ret, size;
>  
> +    if (!avpkt->data) {
> +        if (avctx->internal->need_flush) {
> +            avctx->internal->need_flush = 0;
> +            ret = ff_setup_buffered_frame_for_return(avctx, data, s->frame, &s->flush_pkt);
> +            if (ret < 0)
> +                return ret;
> +            *got_frame = 1;
> +        }
> +        return 0;
> +    }
> +    s->flush_pkt = *avpkt;
> +    s->frame->pkt_dts = s->flush_pkt.dts;
> +
>      bytestream2_init(&s->g, avpkt->data, avpkt->size);
>  
>      /* check if this frame is even supposed to change */
> -    if (avpkt->size < 8)
> +    if (avpkt->size < 8) {
> +        avctx->internal->need_flush = 1;
>          return avpkt->size;
> +    }
> +    avctx->internal->need_flush = 0;
>  
>      /* start after the chunk size */
>      size = bytestream2_get_be32(&s->g) & 0x3FFFFFFF;
> @@ -471,14 +488,18 @@ static int qtrle_decode_frame(AVCodecContext *avctx,
>  
>      /* if a header is present, fetch additional decoding parameters */
>      if (header & 0x0008) {
> -        if (avpkt->size < 14)
> +        if (avpkt->size < 14) {
> +            avctx->internal->need_flush = 1;
>              return avpkt->size;
> +        }
>          start_line = bytestream2_get_be16(&s->g);
>          bytestream2_skip(&s->g, 2);
>          height     = bytestream2_get_be16(&s->g);
>          bytestream2_skip(&s->g, 2);
> -        if (height > s->avctx->height - start_line)
> +        if (height > s->avctx->height - start_line) {
> +            avctx->internal->need_flush = 1;
>              return avpkt->size;
> +        }
>      } else {
>          start_line = 0;
>          height     = s->avctx->height;
> @@ -572,5 +593,6 @@ AVCodec ff_qtrle_decoder = {
>      .init           = qtrle_decode_init,
>      .close          = qtrle_decode_end,
>      .decode         = qtrle_decode_frame,
> -    .capabilities   = AV_CODEC_CAP_DR1,
> +    .caps_internal  = FF_CODEC_CAP_SETS_PKT_DTS | FF_CODEC_CAP_SETS_PKT_POS,
> +    .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
>  };
> diff --git a/tests/ref/fate/qtrle-8bit b/tests/ref/fate/qtrle-8bit
> index 27bb8aad71..39a03b7b6c 100644
> --- a/tests/ref/fate/qtrle-8bit
> +++ b/tests/ref/fate/qtrle-8bit
> @@ -61,3 +61,4 @@
>  0,        160,        160,        1,   921600, 0xcfd6ad2b
>  0,        163,        163,        1,   921600, 0x3b372379
>  0,        165,        165,        1,   921600, 0x36f245f5
> +0,        166,        166,        1,   921600, 0x36f245f5

Following what i said in the nuv patch, do you still experience timeouts
with the current codebase, or even if you revert commit
a9dacdeea6168787a142209bd19fdd74aefc9dd6? Creating a reference to an
existing frame buffer shouldn't be expensive anymore for the fuzzer
after my ref counting changes to target_dec_fuzzer.c

This is a very ugly solution to a problem that was already solved when
reference counting was introduced. Returning duplicate frames to achieve
cfr in decoders where it's expected shouldn't affect performance.