[Coco] Re: again: CoCo RGB to VGA conversion
David J Bush
twixt at cstone.net
Mon Aug 23 21:45:09 EDT 2004
> > It's hard for a converter to scale up a line to a fraction of a line,
> > such as 1.5 lines (without some significant gray-level anti-aliasing).
> > Let's see, the VGA has 480 lines. Straight Coco3 has 384, or 80%, so
> > you have 10% of the total screen height blank at top and bottom. Not
> > too bad.
> > RSBASIC and maybe even OS-9 can be poked up to 200 high, or 400 out of
> > 480. Some BASIC hackers claim to have hit 225, or 450 out of 480.
Where does the 384 come from? Is that vertical padding? With 225 lines
to work with, that's 159 extra lines. Right? So the ideal thing for this
conversion hardware to do, would be to snip out those 159 blank scan
lines, and mutliply the usable 225 by a nice integer, namely 2. That
would produce 450 scan lines, with a margin of 30 lines to fit within
a 480 line screen. Piece of cake! :-)
Oh, and a switch to choose either the analog RGB signal or the composite
signal would be nice. That way, users could have the best of both
worlds, RGB for most apps, and composite for software which uses
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