Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ig!bionet!csd4.milw.wisc.edu!uxc!uxc.cso.uiuc.edu!ux1.cso.uiuc.edu!uxe.cso.uiuc.edu!mcdonald
From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.graphics
Subject: Re: RGB to NTSC converters
Message-ID: <46900034@uxe.cso.uiuc.edu>
Date: 23 Apr 89 14:50:00 GMT
References: <7753@batcomputer.tn.cornell.edu>
Lines: 27
Nf-ID: #R:batcomputer.tn.cornell.edu:7753:uxe.cso.uiuc.edu:46900034:000:1323
Nf-From: uxe.cso.uiuc.edu!mcdonald    Apr 23 09:50:00 1989


> >We are now in the market for a RGB video to NTSC (i.e. VCR) converter. It
> >seems like this is a rapidly changing field, so the info I had from last
> >year may not be valid. 


It is very easy to program a VGA to get quite close close to NTSC scan rates.
You, of course, lose BIOS mode switching support, so you have to write
your own programs (or generate a TSR to trap an appropriate mode set call.)
AS I recall, I got it to produce 240x640 (noninterlaced of course).
I this works great for sending video to big screen TV's that are
already set up for lectures, etc., as long as they take RGB (NTSC scan rate)
or you get a modulator (OK, I made one from a chip, but you should be able
to buy one.)

Question is, does anybody make a genlock for the VGA? There is a line
on the video connector for inputting the clock rate, but I see no answer
for the non-interlace problem. What would happen if you recorded the
output on a regular high-class home VCR, is it not possible to play these
tapes on pro grade (i.e. very expensive, found only in TV stations)
home format VCRs
that feed out broadcast-grade sync? OR do TV stations, when they play
consumer tapes, just play them on a regular VCR into a generic 
resynchronizer box (something that digitizes the frames and plays them out at 
the right rate)?

Doug McDonald