Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!ucsd!ucbvax!hplabs!hpfcdc!hpfclm!hpfcdj!myers
From: myers@hpfcdj.HP.COM (Bob Myers)
Newsgroups: comp.graphics
Subject: Re: VCR hook-up to VGA monitor
Message-ID: <17670005@hpfcdj.HP.COM>
Date: 27 Jan 89 19:34:52 GMT
References: <1109@marlin.NOSC.MIL>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 27

>I would be very interested in how to convert an RGB signal to NTSC and vice
>versa.  (Especially as I have a b&w monitor and a NEC MultiSync, I would like
>color!)  Any information anyone could send me on this subject would be greatly
>appreciated.

There is not an "easy" solution for this, as the conversion in either direction
requires some fancy encoding/decoding which is best done by some specialized
ICs; I refer you to the Motorola Linear and Interface ICs data book for
some examples.  (Note particularly the MC1377 NTSC encoder.)

However, one basic question should be answered first; "NTSC" video not only
implies a means of color encoding, but also a very specific timing.  Most
"computer" video formats do not match NTSC timing, and it takes a rather
sophisticated converter to take non-NTSC-rate RGB and produce a signal
suitable for viewing on the ol' home TV.  You should also realize the you
WILL lose image quality in going from nearly any RGB signal to NTSC; besides
the low-res timing, NTSC encoding *purposely* reduces the effective color
resolution.  It also is not particularly good at color fidelity (hence the
old joke "NTSC = Never Twice the Same Color").

Further discussion on NTSC/RGB conversion and color encoding in general may be
more appropriate in sci.electronics or rec.video.


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
{the known universe}!hplabs!hpfcla!myers |  sentient life-form on this planet.