Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site nicmad.UUCP
Path: utzoo!linus!decvax!genrad!panda!talcott!harvard!uwvax!astroatc!nicmad!brown
From: brown@nicmad.UUCP
Newsgroups: net.video
Subject: Re: Help w/VHS slow dubbing
Message-ID: <558@nicmad.UUCP>
Date: Wed, 26-Feb-86 16:44:12 EST
Article-I.D.: nicmad.558
Posted: Wed Feb 26 16:44:12 1986
Date-Received: Sun, 2-Mar-86 07:32:45 EST
References: <5031@alice.uUCp>
Reply-To: brown@nicmad.UUCP (Mr. Video)
Organization: Nicolet Instrument Corp. Madison WI
Lines: 42

In article <5031@alice.uUCp> d@alice.UucP (Dan Rosenberg) writes:
>I have a slight video problem that I need a quickie fix for:
>	I am, along with six other students, producing a video tape on various
>subjects in physics. Several scenes MUST be in slow motion. All video was shot
>on a 1/2" VHS deck (Panasonic PV-8000) then dubbed up to 3/4" U-matic format.
>The scenes that had to be in slow motion were then dubbed up using the frame by
>frame "slow" advance feature of the PV-8000. In viewing the 3/4" tape, and the
>3/4" composite master, we were quite pleased. Cheap, crisp, clear slow motion
>video. 
>	Problem: The tape is to be distributed on 1/2" (i.e. for our home
>collection, school's collection, and so forth and so on...) VHS. When we dub
>down to 1/2" (not to the PV-8000, but just a 3-4 year old Industrial Quality SP
>only Panasonic VHS) things begin to look funny. All of the standard play video
>dubs fine, but the slow motion "rolls" a bit. It is not the type of rolling
>that you get when you have the Vert. Hold set wrong on a monitor, but each
>frame (of slow motion original video, not each frame of Composite 3/4") moves
>down the screen as it is being played.

I believe you have what is known as a time-base error.  Someone on the net
will correct me if I am wrong, but basically what is the matter is that the
slow motion stuff that you get recorded on the 3/4" machine isn't exactly
NTSC standard anymore.  When the machine is placed in slow motion, the
vertical sync area has a little something added to it.  You're lucky that
the 3/4" deck will record it, the one I have doesn't always.  When you played
it back to the other VHS machine, the bastardized vertical sync probably
caused the recorder to not record correctly.  Try going from the 3/4" deck
to the newest VHS table-top unit you can find.  They tend to be more tollerant
of bad vertical sync.

To fix the problem, you need to send the output of the VHS machine through
a TBC unit, that will sync itself up to the incoming video, then record
the slow motion stuff on 3/4".

I don't do any slow-motion recording/editing at home, because of the above
reasons.
-- 

              ihnp4------\
            harvard-\     \
Mr. Video      seismo!uwvax!nicmad!brown
              topaz-/     /
             decvax------/