[FFmpeg-trac] #11182(swscale:closed): yuvtestsrc and yuv444p->rgba->yuv444p conversion result in huge difference

[FFmpeg]

#11182: yuvtestsrc and yuv444p->rgba->yuv444p conversion result in huge difference
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             Reporter:  Andrew-R     |                    Owner:  (none)
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:  swscale
              Version:  unspecified  |               Resolution:  invalid
             Keywords:  colorspace   |               Blocked By:
  color_primaries                    |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Andrew-R):

 Replying to [comment:37 Balling]:
 > You did not read until comment #28 on doom9, it starts talking about
 xvYCC.

 but yuvtestsrc does not produce xvYCC by default?

 >
 > >Not sure how specific figure in YUView should look for invalid colors
 after such roundtrip
 >
 > Depends what algoritm it uses to clip YCbCr out-of-gamut values.
 Typically you need to use LittleCMS to see how to clip YCbCr color in
 xvYCC to closest value representative in RGB. But you can enable zoom box
 in Yuview and you will see actual values.

 Yes, I was using exactly zoom box to see values first!


 I found patent from broadcom :)
 https://patents.google.com/patent/EP1560417A2/en
 "System and method for clipping values of pixels in one color space so not
 to exceed the limits of a second color space"

 and algo from BBC on  this constant hue method realized by SGI machinery.

 But well, may be I just use wrong test source ???
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Ticket URL: <https://trac.ffmpeg.org/ticket/11182#comment:39>
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