[FFmpeg-trac] #5995(undetermined:new): Blockiness and ringing in prores4444 encoded video with alpha

[FFmpeg]

#5995: Blockiness and ringing in prores4444 encoded video with alpha
-------------------------------------+-------------------------------------
             Reporter:  stib         |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:               |               Resolution:
  prores,alpha                       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by stib):

 None of those commands produce output with an alpha channel, there is no
 noise or blockiness, but the alpha blending is gone, and it looks like it
 is ignoring the alpha in the original image:

 [[Image(http://blob.pureandapplied.com.au/wp-
 content/uploads/2016/12/out.png)]]
 Replying to [comment:4 cehoyos]:
 > Do any of the following commands allow to reproduce the issue you see?
 > {{{
 > $ ffmpeg -i source.png -pix_fmt yuvj444p out.jpg
 > }}}
 > {{{
 > $ ffmpeg -i source.png -vf format=yuv444p out.png
 > }}}
 > {{{
 > $ ffmpeg -i source.png -vcodec prores_ks -pix_fmt yuv444p10 out.mov
 > }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/5995#comment:6>
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