[Coco] Re: CoCo 3 to VGA

Kevin Diggs kevdig at hypersurf.com
Mon May 24 17:48:44 EDT 2004


	I can tell by looking at the output of my deuce on a TV that
it is NOT outputting the same picture in each field. As compared to a
"standard" interlaced TV signal, There is a visible space between the
scans on the deuce output. This would not be there if it were outputting
the same picture in each field.

	The question remains:  Does it output both fields (one being
blank) or is it 60 Hz non-interlaced video consisting of 1 262.5 scan
frame? I suspect the latter. Keep in mind that standard multi-sync
monitors can be driven in interlaced modes. They just aren't used
anymore. Look at an old XFree86 config file.

	To pose this question in another way, What is it that makes a
TV interlaced? Is it the TV itself? Or is it the timing of the signal
that drives it (think about the multi-sync monitor)?


Torsten Dittel wrote:
> >I don't think we need the de-interlacing either.
> I always wondered if there is an interlaced picture coming out of the
> CoCo's modulator (just writing the same picture a second time). I made
> some experiments with a 50Hz PAL CoCo2 in the 80s switching between two
> PMODE4 screens with the 50Hz VSYNC interrupt, one containing the odd,
> the second the even scanlines. I wondered if this would help to double
> the vertical resolution (although the picture was flickering with 25Hz
> at the horizontal lines contained in only one of the both interlaced
> screens). I dont remember how it looked on a TV set (if I ever tried it
> at all). On a green monochrome composite monitor it looked fine, but I
> hadn't the impression of a doubled vertical resolution, just of adding
> kind of greyscale to the picture (like anti-aliasing, everything looked
> "smoother").
> TV guys? Gene?
> Torsten
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