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From: lauren@vortex.UUCP (Lauren Weinstein)
Newsgroups: net.video
Subject: Re: Gen Lock
Message-ID: <813@vortex.UUCP>
Date: Wed, 25-Sep-85 15:02:21 EDT
Article-I.D.: vortex.813
Posted: Wed Sep 25 15:02:21 1985
Date-Received: Sun, 29-Sep-85 05:14:11 EDT
References: <3475@utah-cs.UUCP>
Organization: Vortex Technology, Los Angeles
Lines: 23

Very briefly, genlock refers to all video sources running off a common
horizontal and vertical (or composite) sync source.  In a studio, there
is normally a master sync generator for all air-related equipment--
VTRs, cameras, switchers, etc.  To do smooth switching, effects, or virtually
anything else, you gotta be locked onto a common sync.

If a graphics board says it will lock onto external sync, then you can
in theory do things like superimpose or key insert graphics onto an 
external video source.  However, there are several things to watch out for:

1) Many boards that claim to have this capability do it badly, resulting
   in poor supers or insert keying.

2) Many consumer VCRs have pretty crummy sync stability.  Graphics
   "jitter" may result if such machines are used.

3) If you want to have color graphics interact with an external 
   COLOR signal, the circuitry involved is considerably more complex.
.  Many boards can't handle it.  You have to lock onto the colorburst phase
   of the external signal to keep the board's color signals and the external
   signal in phase.

--Lauren--