🚀 go-pugleaf

In article <2745@tekig5.TEK.COM> wayneck@tekig5.TEK.COM (Wayne Knapp) writes:
>In article <536@jolnet.UUCP>, rich@jolnet.UUCP (Rich Andrews) writes:
>> >  Yes, this is called genlock. The idea is to take your ST's signal,
>> >synchronize it with your VCR/TV's signal, and blend the two together. Genlock
>> >
>> Neither Antic nor Atari nor anyone else is going to genlock the ST unless
>> Atari engineering reworks the glue chip.  There have been several different
>> versions of the GLUE chip around and the very first rev. was able to be 
>> genlocked, but that version has not been made in over 2 years.  The only
>> way to genlock it now is with a frame synchronizer (read $5,000).  
>> 
>
>   I saw an add by Pratical Solutions for a RGB to composit video adaptor.  I
>have also heard of a genlock device that takes in any video signal and locks 
>it to another.  I forget the name, but I will get the details.  As I understand
>it isn't that expensive (less than $1000, I think) and gives better results 
>that the cheap genlocks that are normally used for Amigas.  Note that the Amiga
>has a more flexible external video sync control than the ST.  If all this is
>true, it would give the ST a much more flexible genlock device than just a 
>genlock designed for the ST.  One could genlock a ST and Atari 800 for example.
>I try to find out the details and post more later.  I think it is much better
>to try and genlock the signals rather than genlock the computer.
>
>                                   Wayne Knapp  


In most normal situations there is a way to acccomplish a gen-lock situation.  
That way is to Gen-lock the VCR to the ST.  This has been done in 
theory and in practice as I will explain in a bit.  To accomplish this we take
the Horizontal and Vertical sync signals from the ST, buffer them (so not to 
blow up the GLUE chip, experience dictates that (:>)) and feed it into the 
Horiz. and Vertical sync inputs on a Home VCR.  The VCR will require modification
by an experienced video engineer.  Now that that is accomplished one has to now
take into consideration timing.  (Timing ???)  For the video signals to mix 
properly, without a horizontal shift or a color shift, the two signals must 
be in perfect timing at the point of mixing.  If you watch TV for any length
or time you will see at some point in time or another, a horizontal shift occur
immediatly after a dissolve or a wipe.  This is caused by poor horiz. timing.
If you see a color shift it is due to poor subcarrier timing.  This will also
hold true for keying also, but I digress.  In Springfield Ill., there is a 
TV station that uses some consumer beta machines on air.  These machines were
modified to accept external sync and subcarrier and the output of those machines
are then fed into a time base corrector (horizontal freq in asynchronous, 
horiz. freq out synchronous) and then to the switcher.  

	In the case of the home VCR we are using the ST as the "standard"
and are "slaving" everything else from it.  Is it worth it?  Not really,
unless you are really set on doing it.  The right way would be to "slave"
the ST to whatever you are feeding in.  To really do it right would require
a good TV sync generator driving all of the other equipment including 
using the outputs from the generator to drive the ST.  I have seen many ads for 
genlock accesories for the ST but have not ever seen any product from the parties
that offer it.  Being an RGB analog output, it would be nice to see an inexpensive
effects switcher with chroma key capabilities for home use with an ST.

If all of this sounds confusing, it is probably because it is! (:>)  Think
about this one.  Digitize a video signal.  Store it in RAM.  Let an external
source clock it out at any rate it wants to.  Now do it in real time.
Now do it in color!
That is what you need to have to build a frame-synchronizer.  With that you 
don't need to genlock the ST.  Just genlock the frame-syncronizer.

rich
andrews

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