[FFmpeg-devel] [PATCH 5/5] avcodec/pafvideo: Only clear frame when it was written to

[Lynne]

Aug 6, 2019, 10:30 PM by michael at niedermayer.cc:

> This avoids unneeded operations and makes the code faster.
>
> Fixes: Timeout (12sec -> 9sec)
> Fixes: 15724/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PAF_VIDEO_fuzzer-5750842205929472
>
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/pafvideo.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/pafvideo.c b/libavcodec/pafvideo.c
> index 323c662c59..72d5d4b523 100644
> --- a/libavcodec/pafvideo.c
> +++ b/libavcodec/pafvideo.c
> @@ -55,6 +55,7 @@ typedef struct PAFVideoDecContext {
>  
>  int current_frame;
>  uint8_t *frame[4];
> +    int dirty[4];
>  int frame_size;
>  int video_size;
>  
> @@ -187,6 +188,7 @@ static int decode_0(PAFVideoDecContext *c, uint8_t *pkt, uint8_t code)
>  j      = bytestream2_get_le16(&c->gb) + offset;
>  if (bytestream2_get_bytes_left(&c->gb) < (j - offset) * 16)
>  return AVERROR_INVALIDDATA;
> +            c->dirty[page] = 1;
>  do {
>  offset++;
>  if (dst + 3 * c->width + 4 > dend)
> @@ -329,9 +331,13 @@ static int paf_video_decode(AVCodecContext *avctx, void *data,
>  c->pic->palette_has_changed = 1;
>  }
>  
> +    c->dirty[c->current_frame] = 1;
>  if (code & 0x20)
> -        for (i = 0; i < 4; i++)
> -            memset(c->frame[i], 0, c->frame_size);
> +        for (i = 0; i < 4; i++) {
> +            if (c->dirty[i])
> +                memset(c->frame[i], 0, c->frame_size);
> +            c->dirty[i] = 0;
> +        }  
>

The extra code doesn't justify that speedup.