[Coco] Bad news, good news...

[jdaggett at gate.net]

Boisy

By far S-Video would be superior to Composite video. 

Tao major problems in composite video demodulation that is 
eliminated in S-video is:

1) the color burst phase shifter that is needed to feed the 
Chromance demodulator. This will demodulate the I and Q signals 
to for the three components of S-Video. R-Y, B-Y and G-Y.

2) the need for the delay line inline with the luminance portion of the 
composite signal is eleminated as you do not have the demodulate 
the I and Q signals. 

There are problems of many variables going out of adjustment 
when converting composite video to RGB in a TV. Yes that is what 
is happening. The Chromanance info demodulated ends up driving 
the grids of the picture tube. The luminance signal drives the 
cathode. 

S-Video eleiminates intermediate steps. It also eliminated the 
problem of delays through chromanance demodulator circuits. This 
eleminates the possibility of minute fractions of a second difference 
in arrival of the luminance versus the chromanance signals to the 
CRT. 

S-Video preforms in many ways far better than a composite video 
signal. Another problem eliminated is the RF modulation and 
demodulation that comes when composite video is shoved over an 
RF channel. Now you introduce difference between tranmit 
frequency, recive frequency, the effect the AFC circuit has on the 
signal, and finall more chances for noise introduction. 

Separate baseband signals is far more preferred. 


james

On 13 Dec 2005 at 6:23, Boisy G. Pitre wrote:

From:           	"Boisy G. Pitre" <boisy at boisypitre.com>
Subject:        	Re: [Coco] Bad news, good news...
Date sent:      	Tue, 13 Dec 2005 06:23:37 -0600
To:             	CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Send reply to:  	CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
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> 
> On Dec 12, 2005, at 6:35 PM, Stephen H. Fischer wrote:
> >
> > The number of people wanting to use a NTSC S-Video TV to display 
> > the output of a CoCo 3 is zero even though the display is really
> > great. My  interest in getting a 725 is for non-CoCo 3 use.
> 
> I wouldn't say "zero."  I am very interested in seeing how well the 
> CoCo 3 projects video to an S-Video supplied television.  You claim 
> it is comparable to an RGB monitor.  If that's the case, an RGB->S-
> Video convertor would be just as desirable as an RGB->VGA convertor.
> -- Boisy G. Pitre boisy at boisypitre.com "Monde, je suis pas venu ici
> pour vous faire de la peine."
> 
> 
> 
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