[FFmpeg-trac] #4365(avcodec:new): Multithreaded slice decoding in HEVC producing incorrect output

FFmpeg trac at avcodec.org
Fri Mar 13 12:52:03 CET 2015

#4365: Multithreaded slice decoding in HEVC producing incorrect output
             Reporter:  kurosu   |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  avcodec  |                  Version:  unspecified
             Keywords:  HEVC     |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
 When using the appropriate sequence (containing slices or wavefronts),
 that kind of command-line produce varying CRCs:
 ./ffmpeg -threads 12 -thread_type slice -i <seq> -an -sn -f crc -

 The expected output is a constant CRC, indicating valid decoding. This is
 what happends when 1 thread is used, or thread type is frame.

 This is a regression since cf92cc8. The commit in itself can cause
 crashes, and to test it, 7117547 is required. I'm unfortunately not sure
 if any other commit/fix is required. Note that the code has changed much
 since cf92cc8, but the issue is still present.

 The sequence on which I observed it is unfortunately not distribuable, and
 I don't know what freely distribuable sequence would exhibit the issue.

Ticket URL: <https://trac.ffmpeg.org/ticket/4365>
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