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Old 25th March 2013, 12:41   #1  |  Link
fvisagie
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How do ConvertToRGB* handle out-of-range YUV combinations?

When the input clip to ConvertToRGB*() contains pixels with out-of-range YUV combinations no error is thrown, so presumably they are processed somehow. However, I can't find any explanation in the Convert description of how this done. What exactly happens in such cases?

Thanks,
Francois
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Old 25th March 2013, 13:34   #2  |  Link
2Bdecided
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The resulting RGB values are clipped to be within the range 0-255.

Cheers,
David.
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Old 25th March 2013, 18:57   #3  |  Link
fvisagie
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Thanks, appreciated.
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Old 25th March 2013, 20:47   #4  |  Link
Gavino
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See the thread U and V ranges for valid RGB for a demonstration, and post #14 of the thread (and the later post #25) for a function that will identify the out-of-range pixels in a frame.
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Old 26th March 2013, 09:15   #5  |  Link
fvisagie
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Thanks, Gavino, that's a very useful function and thread.
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Old 26th March 2013, 09:47   #6  |  Link
fvisagie
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In the case where
  1. Input is in out-of-RGB-gamut YUV
  2. Intermediate conversion to and from RGB32 is needed, and
  3. Output is in YUV

a useful approach seems to be

Code:
# Reduce number of pixels that will be clipped by RGB conversion
Levels(...)
ConvertToRGB(...)
# RGB32 work
ConvertToYV12(...)
# Back in YUV complete rest of colour treatment to what's desired for aesthetics and what output can handle:
#   restore colour range and/or correct gamma and/or adjust dynamic range etc.
This will require balancing reduced clipping against loss of colour resolution, but in principle this may be worth trying out, correct? I'm asking because I don't always know enough yet to understand what I'm looking at .
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