[Coco] Re: CoCo to SVGA converter?

[jdaggett at gate.net]

Componert video has three components and is called component 
video because at any instance of time the color signal can be 
broken into four components Luminace, and three chrominance 
signals R-Y, G-Y and B-Y. The three needed components for color 
transmission are as follows: 

Y	luminance
B -Y	Blue minus Luminance or Chrominace A
R-Y	Red minus Luminance or Chrominace B

The Y signal is governed by the following formula

Y = 0.3*R + 0.59*G + 0.11*B

The R-Y signal lies upon the x-axis and is vectorally rotated 90 
degrees from the color burst. The B-Y would then lie on the Y-Axis 
and be rotated 180 degrees from the color burst. Like the I and Q 
signals transmitted in NTSC video The R-Y and B-Y are orthogonal 
(perpendicular) to each other. The I and Q signals are shifted 33 
degrees from the R-Y and B-Y signals.

G-Y can be derived from R-Y and B-Y by the governing equation

G-Y = -0.57*(R-Y) -  0.19*(B-Y).

By equally rotating the axis of all three components, Y,  R-Y, and B-
Y, all colors can be derived.  

What this does is allows large color transmission in a relatively 
small amount of bandwidth. What this does is place a higer burden 
on the receiving equiptment to derive the RGB signal from the 
components transmitted. 

Oddly enough these are the same signals that come out of the 
MC6847 VDG chip used in the Coco 1/2; Y, R-Y and B-Y.

james

On 31 Oct 2004 at 9:16, Robert Emery wrote:

Date sent:      	Sun, 31 Oct 2004 09:16:32 -0800 (PST)
From:           	Robert Emery <theother_bob at yahoo.com>
Subject:        	Re: [Coco] Re: CoCo to SVGA converter?
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> > And Component is close to RGB?
> 
> Not close... identical. It's called component because the
> 3 components (R, G and B) are sent out separately.
> Generally sync is combined with Green.