[FFmpeg-trac] #6760(ffmpeg:new): Gray screen after transcoding media pix_fmt yuv444p10le to yuv420p. Macroblocks visible

[FFmpeg]

#6760: Gray screen after transcoding media pix_fmt yuv444p10le to yuv420p.
Macroblocks visible
-------------------------------------+-------------------------------------
             Reporter:  leogdiniz    |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:  ffmpeg       |                  Version:  3.1.7
             Keywords:  transcode    |               Blocked By:
  yuv420p gray chroma                |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 When transcoding a video that uses h264 codec and pixel format yuv444p10le
 to h264 yuv420p on any ffmpeg version after 3.0.8 the transcoded media is
 all messed up with a gray screen.
 I found out the using ffmpeg 3.0.8 the problem won't happen. However it
 hapens on version 3.0.9 and after.
 How to reproduce:

 Download the file from this URL:
 https://s3.amazonaws.com/player.hotmart.dev/test/ffmpeg_ticket/h264_pix_fmt_444.mkv
 The file has 2.5MB
 Open the terminal and move to the folder where you downloaded the file
 above.
 Run the command:
 {{{
 docker run -t -v /$(pwd):/home leonardodinizhotmart/ffmpeg:3.4 ffmpeg -i
 /home/h264_pix_fmt_444.mkv -pix_fmt yuv420p /home/output.mp4
 }}}
 The output.mp4 file will have the problem.
 [[Image(https://s3.amazonaws.com/player.hotmart.dev/test/ffmpeg_ticket/thumbnail.jpg)]]
 If you run the command bellow the problem won't happen:
 {{{
 docker run -t -v /$(pwd):/home leonardodinizhotmart/ffmpeg:3.0.8 ffmpeg -i
 /home/h264_pix_fmt_444.mkv -pix_fmt yuv420p /home/output.mp4
 }}}

 The Docker file information can be found at
 https://hub.docker.com/r/leonardodinizhotmart/ffmpeg

 The ffmpeg -v 9 -loglevel 99 log can be found at:
 https://s3.amazonaws.com/player.hotmart.dev/test/ffmpeg_ticket/log-3.0.8.txt
 https://s3.amazonaws.com/player.hotmart.dev/test/ffmpeg_ticket/log-3.4.txt


 I see that ffmpeg reports a gray chroma error during the encoding on
 version 3.4. I can't see why it's doing this since that on version 3.0.8
 it works just fine =(

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6760>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker