[FFmpeg-trac] #7388(ffmpeg:new): Using -threads causes distorted output in some frames

FFmpeg trac at avcodec.org
Wed Aug 29 16:50:52 EEST 2018


#7388: Using -threads causes distorted output in some frames
---------------------------------+--------------------------------------
             Reporter:  jluther  |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  ffmpeg   |                  Version:  git-master
             Keywords:           |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
---------------------------------+--------------------------------------
 Summary:

 I am encoding a 1080p H.264 Main Profile MP4 source to 180p scaled
 Baseline MP4 using CRF rate control.

 When I run my FFmpeg command with a -threads value greater than 8, there
 are heavily distorted frames in the lower half of the output at around
 00:00:01 into playback.

 When -threads param is removed from the command, the frames are not
 distorted.

 Reproducing:

 Behavior is reproducible on Mac 10.13.6 using FFmpeg built from August
 28th Git master.

 However, it is only reproducible with this one video. Other samples encode
 fine.

 Command that produces the distorted output:

 ffmpeg -y -report -i jluther-threads-bug-report-source.mp4 -pix_fmt
 yuv420p -vsync cfr -r 25 -filter:v '[in] scale=320:-2 [out]' -c:v libx264
 -profile:v baseline -x264opts keyint=100:vbv-maxrate=300:vbv-bufsize=300
 -threads 12 -an out/with-12-threads.mp4

 Console output and -report log are in attached archive.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7388>
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