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Re: IIgs RGB to YPbPr Component experiment

mdj wrote:

Michael J. Mahon wrote:



A true scan conversion from NTSC scan standards to VGA *could* produce
a rock-solid display--if the sampler locks to the Apple II dot clock
(14.3MHz), but this would only work if the size of the Apple display
on the LCD caused it to occupy an equivalent number of LCD pixels,
which would call for some "windowing" in the converter.

For example, a 560-dot Apple screen could be beautifully mapped to
560 LCD pixels, or 1120 LCD pixels.



The VGA approach would work wonderfully, but only copes with older
displays.

My concern with the LCD approach is that a direct mapping won't produce
an image with correct aspect ratio, as the Apple pixels are not square.


True--but I was only describing the constraints in the horizontal
direction.  You can use some integral number of vertical lines
to approximate the shape of Apple pixels.

560x384 (two display lines per Apple line) isn't too bad a match.


Unfortunately LCD's aren't quite at the resolution needed to do a nice
job. You can have either a clear picture with shonky aspect, or a
slightly distorted one that's correct aspect. It'll work well for
colour composite emulation, but not RGB or monochrome unfortunately,
without having an incorrect aspect ratio.

I'd like to see both implemented


I think we're going to see some attempts soon...

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
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