Re: [stella] Jim's heart will go on demo

Subject: Re: [stella] Jim's heart will go on demo
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 15 Jun 1998 18:45:51 +0200
At 17:15 15.06.98 +0200, you wrote:

>...ah yes, and of course a different number of scanlines for some PAL
>color. By the way, does it lose color on NTSC too?

No, this is something specific to PAL systems. The reason for the
colourloss is Atari's implementation of the PAL (Phase Alternating
Line) feature. 

If you want to display yellow and the TV signal gets delayed a bit while
broadcasting it, it might come out a bit greenish. NTSC TVs have an 
adjusment knob to fix this problem. In PAL a scanline gets broadcasted 
normally in one frame and with the colour phase shifted by 180 degrees 
in the next frame. So if the yellow is delayed to become greene, in the
next frame it will be off the same amount in the other direction,
due to the shifted phase, and turn to blue. And if you display
green and blue on alternating frames you would still see some sort 
of yellow.

Since the phase alternation is also done on every other line in one frame,
doing an odd number of scanlines on the VCS would start the second
frame with the wrong orientation. Therefore one frame would display
a certain colour and the next frame would display the 'anticolour'
for that colour turning the display to only grey.


Ciao, Eckhard Stolberg



--
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/stella.html

Current Thread