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RE: YUV/RGB Color Space Issues



	-----Original Message-----
	From:	Stephane Blondin [SMTP:Stephane_Blondin at Discreet.COM]
	Sent:	Thursday, December 18, 1997 2:18 PM
	To:	multiple recipients of
	Subject:	RE: YUV/RGB Color Space Issues



	You are right. The RGB color space has a larger gammut than the YUV
space.
	BUT, because the end-of -the-line display devices, CRTs are RGB
devices,

	>  yes but the CRT displays these colors nonlinearly and you process
them in RGB space linearly.  I believe the SGI luma transfer functions are
different than normal video transfer functions.
	this greatly influences how we define a signal as being legal or not
(I
	know it's not the only factor..). So it is safe to assume that an
approach
	where the RGB color space is fit within the YUV space is safe and
will
	cover the vast majority of the colors which we can safely assume
will
	display accurately on the end projection devices.

	In this case is this space still shaped like a cube?


	AS a side note, how will you handle the fact that the luma equations
as defined in Rec. 709 (HDTV) are different than those defined in 601 or
240M?  I realize we probably can't see these differences, but which will you
pick?  

	Thanks for the education.





	     

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