Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!att!cbnews!gwe
From: gwe@cbnews.att.com (George W. Erhart)
Newsgroups: comp.windows.ms
Subject: Re: video boards and system configuration -- request for info
Summary: All of the video toys that I have seen seem to use the VGA
	 feature connector, not the computer's backplane to display
	 the image.
Message-ID: <1990Dec30.031638.17817@cbnews.att.com>
Date: 30 Dec 90 03:16:38 GMT
References: <9848.7709.forumexp@mts.rpi.edu>
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 40


I have a friend that is "playing" with a live video board ... that is, a
board from Matrox that can digitize video in real-time and display
on any VGA card that has the VGA feature connector. The real question of
bus speed tends to be an issue if the source for the video display is
from a disk (CD ROM or other). In these cases, the data transfer rate for
the back plane must be high enough to avoid the nasty flicker.

For example, I have a disk drive containing a sequence of digitized
video images that form an animated sequence. I wish to display them 
on a 1 megapixel display with 8 bit planes (256 colors). To display 
a single image (frame) will require transfering 1 megabyte of data 
from the disk to the display.  The standard video refresh rate is 
30 frames per second. Thus, the transfer rate from disk to display 
will need to be 30 Megabytes per second. The ISA bus is not capable 
of this speed. Both MCA and EISA are capable of this rate. However, 
realize 2 things, at 1 megabyte per frame, 30 megabytes per second, 
you will need a lot of disk space AND finding a disk drive that will be
able to get 30 megabytes per second off the disk will be expensive. 
(The newest ESDI drives are ~15 megaBITS per second.) Now project this
to a 24 bit color system ... 3 megabytes per frame!!!

A lot of work is being done in the area of image compression. Several
new chips are on the market that will compress/uncompress in real-time 
with minimal loss of image quality. These chips can significantly cut the
amount of data that must be stored.

If you are simply interested in watching the Finacial News Network in
a window on your VGA display ... you can do this now with off the
shelf hardware/software with the ISA bus, using the VGA feature connector.

Hope this helps. 

(Disclaimer: I am not promoting Matrox products. It just happens to be the
hardware I am most familar with.)

-- 
George Erhart
AT&T Bell Laboratories
att!archie!gwe