Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!im4u!ut-sally!utah-cs!utah-gr!spline!thomas
From: thomas@spline.UUCP
Newsgroups: comp.graphics
Subject: Re: NTSC converters
Message-ID: <2049@utah-gr.UUCP>
Date: Tue, 2-Jun-87 13:11:19 EDT
Article-I.D.: utah-gr.2049
Posted: Tue Jun  2 13:11:19 1987
Date-Received: Thu, 4-Jun-87 06:08:36 EDT
References: <1208@batcomputer.tn.cornell.edu>
Sender: news@utah-gr.UUCP
Reply-To: thomas%spline.UUCP@utah-gr.UUCP (Spencer W. Thomas)
Distribution: na
Organization: Univ of Utah CS Dept
Lines: 24
Keywords: NTSC, RGB, Video

In article <1208@batcomputer.tn.cornell.edu> jaf@squid.tn.cornell.edu.UUCP (James Ferwerda) writes:
>
>a way of converting our 1280 X 1024 X 24 bit RGB images into some NTSC
>compatible format.

Cain't be done.  NTSC only applies to "525" line systems.  You need a
frame buffer that has approximately 480 lines in the vertical
direction, and a 30Hz interlaced scan (i.e. 60Hz field rate).  It
should produce "RS-170" compatible video signals.  Then you can get a
fairly simple circuit to do the conversion from RGB to NTSC.  I don't
know of suppliers off the bat, but I imagine that if you come back to
your video supplier with this problem, he will be able to handle it.

There are other issues: NTSC doesn't have the color bandwidth that an
RGB display can put out, so you need to be careful about color changes
in the image.  One reference on this is "A Low Cost, Video Based,
Animated Movie System for the Display of Time Dependent Modeling
Results", by William E. Johnston, Dennis E. Hall, Fritz Renema, and
David Robertson, at Lawrence Berkeley Labs.  It was published in the
proceedings of the Third Computer Graphics Workshop by USENIX
Association (P.O. Box 7, El Cerrito, CA 94530 USA).  It contains lots
of useful information about NTSC.

=Spencer   ({ihnp4,decvax}!utah-cs!thomas, thomas@cs.utah.edu)