Re: [stella] Some Questions That Bug Me
Subject: Re: [stella] Some Questions That Bug Me|
From: Glenn Saunders <cybpunks@xxxxxxxxxxxx>
Date: Sun, 24 Jun 2001 10:14:20 -0700
At 01:11 AM 6/24/2001 -0700, you wrote:
all-in-one deluxe video cards. Also at 30 fps. How many scanlines of
*real* information is that? Is it more like 240 or 480? And what does
It's hard to say. A lot of capture cards, knowing that they are going to
only play back on progressive-scan rather than interlaced monitors (as most
computer video modes are) will only scan in video at half-res. Computer
monitors do not play back interlaced video very well, although DVD player
software has some elaborate method of doing so.
Glenn mean by interlaced? Does a video signal repeat the same information
twice so that the screen is updated at 60 fps? Or is it new information
each time? But updating every other scanline?
New information every field, alternating even and odd scanlines so that for
any given field every other scanline is blank.
Video game consoles, until recently, all used a noninterlaced video mode
that doesn't leave these gaps but sacrifices half the vertical resolution.
Nevertheless, the 480 pixels of vertical res of interlaced video is only
when you take both fields into account. For any individual field there is
only 240 pixels of vertical res and 240 missing scanlines, which is why
framegrabs almost always look crappier than moving video. If there is any
motion in the video it has to be de-interlaced which usually means just
halving the vertical res. If it's a still, you can merge both fields to
make one full-res video still. In many cases you can composite between
both approaches in a framegrab and I guess some software these days can do
that automatically. I don't know.
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