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
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