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Resolution extrapolation

Posted: Fri May 13, 2011 9:12 pm
by Jones
Okay, as far as one can read the 3DO operates internally
with a resolution of 320x240, the output signal however
is extrapolated to 640x480 by default.

My question: Why?
What's the advantage in that?

I mean if a 320x240 picture gets extrapolated (stretched) by hardware
to 640x480 or if the 320x240 gets simply streched by the TV to fit the
full screen - what's the difference?

Posted: Sat May 14, 2011 12:18 am
by Silanda
AFAIK the 640x480 output did not have to be a simple 2:1 stretch. IIRC the 3DO had a kind of anti-aliasing feature to make the image look nicer than the typical 320x240 screen. I suppose the idea was simply to get a good balance between image quality and memory/bandwidth use.

Posted: Tue May 17, 2011 6:54 am
by ewhac
Part of it was a lesson learned from the Amiga. If you display a typical computer UI on an interlaced television display, you'll get some degree of flickering. People complained about this on the Amiga.

So when it came time to design the 3DO, they decided to put a box filter into the display output such that every other line would be the average of the lines surrounding it. This cut down on flicker a lot.