[FFmpeg-trac] #3345(swscale:closed): Bias in planar YUV to YUV bit depth conversion

[FFmpeg]

#3345: Bias in planar YUV to YUV bit depth conversion
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             Reporter:  abc123      |                    Owner:  (none)
                 Type:  defect      |                   Status:  closed
             Priority:  normal      |                Component:  swscale
              Version:  git-master  |               Resolution:  worksforme
             Keywords:  bounty      |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Changes (by Niklas Haas):

 * resolution:   => worksforme
 * status:  open => closed

Comment:

 I double-checked this using synthetic data and can confirm that FFmpeg is
 rounding accurately as of the latest version, in all dithering modes
 (except "none"). Command line for verification:

 $ ffmpeg -f lavfi -i color=color=black:size=128x128 -vf
 "format=yuv420p10,geq=lum=842,format=yuv420p,extractplanes=y" -frames:v 1
 -y luma.png && identify -verbose luma.png
 ...
   Channel statistics:
     Pixels: 16384
     Gray:
       min: 210  (0.823529)
       max: 211 (0.827451)
       mean: 210.5 (0.82549)
       median: 210 (0.823529)
       standard deviation: 0.500015 (0.00196084)
       kurtosis: -2.00012
       skewness: -1.20334e-21
       entropy: 1
   Colors: 2
   Histogram:
           8192: (210,210,210) #D2D2D2 gray(210)
           8192: (211,211,211) #D3D3D3 gray(211)
 ...

 This is exactly the result we would expect. Similar can be observed for
 different values, e.g. 841 gives an exact average of 210.25. One thing to
 note is that sizes which are not a multiple of 8x8 give a slight deviation
 on account of the dithering pattern being cut off prematurely, but this
 effect is miniscule and isolated to the edges.

 Tentatively closing this one as working correctly.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/3345#comment:16>
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