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Path: utzoo!mnetor!seismo!rutgers!cbmvax!hedley
From: hedley@cbmvax.cbm.UUCP (Hedley Davis)
Newsgroups: sci.electronics,comp.graphics
Subject: Re: Mixing computer and video signals
Message-ID: <1993@cbmvax.cbmvax.cbm.UUCP>
Date: Wed, 10-Jun-87 11:03:55 EDT
Article-I.D.: cbmvax.1993
Posted: Wed Jun 10 11:03:55 1987
Date-Received: Sat, 20-Jun-87 04:19:23 EDT
References: <173@mv06.ecf.toronto.edu>
Reply-To: hedley@cbmvax.UUCP (Hedley Davis)
Organization: Commodore Technology, West Chester, PA
Lines: 43
Keywords: video overlaying, keying
Summary: Amiga Genlock
Xref: mnetor sci.electronics:815 comp.graphics:786

In article <173@mv06.ecf.toronto.edu> drascic@ecf.UUCP writes:
>I want to overlay the graphics output of a computer onto a video image
>of the real world, to implement a cursor.  This means that I have to
>sync the camera to the computer's video, which is reasonably easy to do.
>But once I have the two signals, I have to combine.  Someone suggested
>that "keying" was the route.  This involves switching between the two
>signals, depending on the level of one of them.  Unfortunately, this
>seems to be very expensive.
>
>Is it possible to simply add the two signals through appropriate
>resistors?  Or are there chips available suitable for building a
>simple keyer?  Any hints, suggestions, or suppliers would be much
>appreciated.
>
>	David Drascic    UUCP: drascic@ecf.toronto.edu  OR drascic@utecfb

The synchonization is the tricky part. For a simple cursor, you could
probably do it with hardware of small complexity. For anything more
complex, there is really only one cost effective solution.

Please no flames for this ( requested ) advert.

The Amiga seris of computers from Commodore support genlocking. This
allows the amiga video output to be synchonized with, and overlayed
upon an external composite video source ( like a camera or VCR ). The
genlock then produces a composite video output ( suitable for feeding
to a VCR or monitor ).

If your needs are immediate, I suggest that you obtain a A1000 with a
A1300 genlock ( manufactured by commodore ). If you can wait a few months
the A2000 ( fancier box with better expansion capabilities ), with its
genlock would be a better bet. Still later, other goodies ( as yet
unannounced ) will be forth coming.

On the software end, several video titlers and animiation packages
are available now ( and others are RSN ).

If indeed this is for the university, we have a discount program for
such originizations. You might contact Dave Archambault at
(215)-431-9193 about such policies. He is the man handling all the
university marketing and accounts.

Hedley