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<DIV>This is a good discussion regarding 1/2 inch tapes. I hope I do
not get too verbose with this answer.</DIV>
<DIV> </DIV>
<DIV>The EIA-J tapes may be a real problem. The first step is to look at
the raw video on a waveform monitor.</DIV>
<DIV> </DIV>
<DIV>Is the sync even interlaced? Some of the early cameras were just free
running horizontal oscillators and vertical locked to power line.</DIV>
<DIV>Is it industrial or RS-170? Look for equalizing pulses in the
vertical interval. If not, then many professional proc amps and TBC's will
have problems.</DIV>
<DIV>What is the level that you are dealing with? Hopefully 100 over 40
but don't count on it with the early AGC circuits for video. </DIV>
<DIV> </DIV>
<DIV>If you get past this first step, then it is see what works. For non
RS-170 video, you are in never, never land. It is try, try, and try
again. The 3M unit may help. Also there are other very early proc
amps out there. Even a video DA to adjust sync to a 40 IRE level may
help.</DIV>
<DIV> </DIV>
<DIV>There are video DA's that have sync stretch in them, that may be something
to try.</DIV>
<DIV> </DIV>
<DIV>What will the proc Amp do for you?</DIV>
<DIV> </DIV>
<DIV>It will allow you to adjust the video levels prior to Analog to
Digital conversion to give you best range in that process. It will clean
up the sync pulses to allow proper write clock operation. </DIV>
<DIV> </DIV>
<DIV>What will be the bad things it will do?</DIV>
<DIV> </DIV>
<DIV>If used before a TBC, it may put a lot of jitter in your final
picture. This is because the Proc Amp has replaced the sync and the video
is not always coherent with the video anymore. You sometimes see this as
high frequency jitter or Venetian blinds. </DIV>
<DIV> </DIV>
<DIV>If not RS-170 sync it will burp a lot if it only works with RS-170
sync. Again never, never land.</DIV>
<DIV> </DIV>
<DIV>If heterodyne color we are into never, never land again. Each
manufacture treated this in different ways. Grass Valley was not designed
for this. Now if used before the TBC, again it is never, never land.
You have to experiment to see what you can do.</DIV>
<DIV> </DIV>
<DIV>Where do you put it in the chain?</DIV>
<DIV> </DIV>
<DIV>The TBC has a proc amp on the output. It is required in the design of
any TBC to function. Since the Horizontal interval is not digitized, it
has to be re-generated and inserted in the output of the TBC. Along with
the other handles that we expect. Manufactures have a couple of choices on
where to put the video gain in a TBC. Most do it at the output. It
is possible to put it before the A-D converter. This gives you better
dynamic range. It is an engineering trade off.</DIV>
<DIV> </DIV>
<DIV>There is one method that works almost every time. It requires some of
the most sophisticated equipment known to man. A black magic cloth, a good
monitor and a camera. Use an under scan monitor and point a camera at it
to just fill the scans of the camera. Drape it so light does not get in
and start the transfer. The fast time constant of the monitor serves as
the TBC. If you have access to ramp or stair steps, then set up the
monitor and camera to give as good a transfer as possible. Monitor for
correct brightness and contrast. Camera for correct white and black plus
gamma.</DIV>
<DIV> </DIV>
<DIV>Chris Hill</DIV>
<DIV>WA8IGN</DIV></FONT></BODY></HTML>