How do ConvertToRGB* handle out-of-range YUV combinations?

[fvisagie]

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 (http://avisynth.org/mediawiki/ConvertToRGB) of how this done. What exactly happens in such cases?

Thanks,
Francois

[2Bdecided]

The resulting RGB values are clipped to be within the range 0-255.

Cheers,
David.

[fvisagie]

Thanks, appreciated.

[Gavino]

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.

[fvisagie]

Thanks, Gavino, that's a very useful function and thread.

[fvisagie]

In the case where

Input is in out-of-RGB-gamut YUV
Intermediate conversion to and from RGB32 is needed, and
Output is in YUV


a useful approach seems to be

# 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 ;).