[FFmpeg-devel] [PATCH 1/5] avcodec/vp8: do vp7_fade_frame() later

[Peter Ross]

On Fri, Aug 02, 2019 at 07:19:11PM +0200, Michael Niedermayer wrote:
> On Fri, Aug 02, 2019 at 10:46:04PM +1000, Peter Ross wrote:
> > On Thu, Aug 01, 2019 at 11:44:39PM +0200, Michael Niedermayer wrote:
> > > Fixes: Timeout (100sec -> 5sec)
> > > Fixes: 15073/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP7_fuzzer-5649257362620416
> > > 
> > > Untested as none of the vp7 samples i found executes this codepath
> > 
> > see attached. its all i can find :(
> 
> iam not sure iam making a mistake but these 2 files dont seem to execute
> it

you are right michael. the samples attached have alpha/beta fade bits, but
they are both set to zero, therefore fade() is never called.

i dug up my old vp7-dev branch, and found alpha/beta were forced to specifically
test the fade path with those samples. e.g.:

      int alpha = (int8_t) vp8_rac_get_uint(c, 8) + 1;
      int beta  = (int8_t) vp8_rac_get_uint(c, 8) + 1;

all my other vp7 samples stop before the alpha/beta frame bits.


also, this sample has alpha/beta set to non-zero, but was generated through
fuzzing and produces no video.
https://trac.ffmpeg.org/attachment/ticket/3501/vp7_1_f.avi

cheers,

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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