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2Bdecided · 19th May 2012, 22:45

Rec709 will give me 0-255 RGB. I'll have to check if it gives the correct values for all colours, but this doesn't help me anyway...

I want 16-235 RGB, but I want the correct values. As found in ITU BT 709.

Is PC.709 trying to solve some other problem? e.g. starting with 0-255 RGB, then for some reason using PC.709 to get 0-255 YUV, and then using PC.709 to get back to 0-255 RGB?

If so, that's not what I want to use PC.709 for. I often want to start with 16-235 YUV, and go to 16-235 RGB to maintain headroom but process in RGB (without the clipped expansion to 0-255 that Rec709 causes), and then go back to 16-235 YUV. I often do that, using PC.709 both ways. Works a treat - or I used to think so!

However, in my current use case, only want to do the first part: start with 16-235 YUV, go to 16-235 RGB using PC.709, and then check some levels in RGB space. But unfortunately, the RGB levels created by converttorgb in this case are wrong for all saturated colours (but fine for greyscale!).

Cheers,
David.

19th May 2012, 22:45	#3 \| Link
2Bdecided Registered User Join Date: Dec 2002 Location: UK Posts: 1,673	Rec709 will give me 0-255 RGB. I'll have to check if it gives the correct values for all colours, but this doesn't help me anyway... I want 16-235 RGB, but I want the correct values. As found in ITU BT 709. Is PC.709 trying to solve some other problem? e.g. starting with 0-255 RGB, then for some reason using PC.709 to get 0-255 YUV, and then using PC.709 to get back to 0-255 RGB? If so, that's not what I want to use PC.709 for. I often want to start with 16-235 YUV, and go to 16-235 RGB to maintain headroom but process in RGB (without the clipped expansion to 0-255 that Rec709 causes), and then go back to 16-235 YUV. I often do that, using PC.709 both ways. Works a treat - or I used to think so! However, in my current use case, only want to do the first part: start with 16-235 YUV, go to 16-235 RGB using PC.709, and then check some levels in RGB space. But unfortunately, the RGB levels created by converttorgb in this case are wrong for all saturated colours (but fine for greyscale!). Cheers, David.