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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: <2026@cbmvax.cbmvax.cbm.UUCP>
Date: Tue, 16-Jun-87 11:23:56 EDT
Article-I.D.: cbmvax.2026
Posted: Tue Jun 16 11:23:56 1987
Date-Received: Sun, 21-Jun-87 07:30:50 EDT
References: <173@mv06.ecf.toronto.edu> <6583@shemp.UCLA.EDU> <1171@osiris.UUCP>
Reply-To: hedley@cbmvax.UUCP (Hedley Davis)
Organization: Commodore Technology, West Chester, PA
Lines: 18
Keywords: video overlaying, keying
Xref: mnetor sci.electronics:827 comp.graphics:801

In article <1171@osiris.UUCP> phil@osiris.UUCP (Philip Kos) writes:
>Question for all you serious broadcast people out there: I imagine the
>original chroma key hardware was analog.  Is it still done that way, or is
>it done digitally now?  Seems to me that with these new-fangled digital
>video controllers stuff like this would be getting much simpler, if not
>cheaper...
>
Typically, the computer is phase locked to the incoming video signal.
The actual switching is done with analogue hardware. This avoids ever
having to digitize the incoming video signal ( an expensive proposition
).

I've heard of full digital units which do digitize the incoming video.
These often give you other bells and whistles like freeze frame, color
and contrast corrections ( under software control ), and frame
grabbing. They are more expensive then your run of the mill genlock.

Hedley