Xref: utzoo sci.electronics:7311 rec.video:7440
Path: utzoo!utgpu!watmath!iuvax!rutgers!uwvax!astroatc!brown
From: brown@astroatc.UUCP (Vidiot)
Newsgroups: sci.electronics,rec.video
Subject: Re: sync signal generator
Message-ID: <2548@astroatc.UUCP>
Date: 8 Aug 89 20:18:24 GMT
References: <89216.120136BHB3@PSUVM> <21056@cup.portal.com> <26659@amdcad.AMD.COM>
Reply-To: brown@astroatc.UUCP (Vidiot)
Organization: Vidiot's Hangout
Lines: 32

In article <26659@amdcad.AMD.COM> rpw3@amdcad.UUCP (Rob Warnock) writes:
<
<Otherwise, it [MM5320] works o.k., I guess...

Yep, the part works just fine.  I use it to drive the sync inputs on the
3/4" Umatic decks that I use for editing (through a TTL buffer).  I also
have a sync separator part that I use to set off a one-shot to resync the
sync generator every frame.  The one shot is used because the timing of the
signals available do not exactly match what the generator needs, but since
one of them is early enough, I put it through a one-shot.

The problem with the 3/4" Sony decks (older ones) is that when the input
video is used for sync, a very minor glitch will cause the recorder to
lose gen-lock.  It is worse when editing and the source tape is used as the
sync source.  So, by feeding external sync into both decks, there isn't a
sync separator problem in the 3/4" deck.  I looked at the internals of the
3/4" and noticed that the composite video signal used as sync was about
1/5th of the size of external TTL sync.  This extra level internally provided
enough to keep glitches from screwing things up.

I use the sync separator to take in video signals from the TV and provide
re-sync for the sync generator.  This keeps minor glitches from screwing up
the 3/4" deck when recording off-the-air stuff.  Also, the one-shot is such
that it finishes a short while before the next frame starts, keeping random
glitches between frames was causing random re-syncs.  Of course, massive
changes in original sync timing will still cause glitches.  If only I had
a frame-store unit :-)
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