[Coco] Re: again: CoCo RGB to VGA conversion

[Mark Marlette]

At 8/24/2004 01:45 AM +0000, you wrote:

I would not add the composite mode into it......

Garbage in....garbage out. Keep cost down, RGB only.

I would have to review my TV course text book but you have vertical 
blanking which accounts for x number of lines. Heck that was 20 years 
ago.......

My approach would have a line counter so that you could double or run 
original size vertically.

Someone here will probably beat me to this project. Too many other CoCo 
projects in front of this one. Hardware talent all around. lets get some 
more software development going!

Can someone make more hours in a day? I'll buy a couple.... :)

Mark
Cloud-9



> > > 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
>artifacting.
>
>David
>
>
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