[x264-devel] Corrupted slices

[Jan Brothánek]

Hi,

I ran into a bug occasionally causing output frames with gray stripes (see
screenshot and output.mp4 in links below), using slices. Reproducible with
these parameters (originally found using API) and input.mp4 (link below):

x264 --bitrate 8000 --vbv-bufsize 1600 --vbv-maxrate 8000 --output-depth 10
--profile high422 --output-csp i422 --preset ultrafast --tune zerolatency
--threads 16 --slices 16 -I 120 -b 0 -o output.mp4 input.mp4

Tested with 5a9dfdd (latest master), 5db6aa6 (from Ubuntu repo), aaa9aa8
(from Centos7 repo), and 90a61ec. The bug seems to be non-deterministic but
demonstrates similarly on similar frames - a complex scene followed by a
simple scene that fades to white or black. It looks like the probability of
corruption increases with the number of threads (that's why I used 16) and
the VBV size limitation.

screenshot of input frame:
https://drive.google.com/file/d/1ZiVU5BrKYY_pWr-VzstnOl3AbcW96PhE/view?usp=drive_link
screenshot of output frame:
https://drive.google.com/file/d/1MhxC8GaKOfnCL11nPt2jsTVbX6kigVq_/view?usp=drive_link

input.mp4:
https://drive.google.com/file/d/1e8abTsbs8R-CxNNLDKy1jAfR66-guQMt/view?usp=drive_link
output.mp4:
https://drive.google.com/file/d/1YzcjVGkmzsHvGTXiOh1rVCXGTKw5kIVW/view?usp=drive_link

Best,
Jan
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