[QuadList] What to do with 1/2 inch tapes and proc amps

[COURYHOUSE at aol.com]

David,  what is the  part #  of  it??    Ed#
 
In a message dated 12/13/2011 7:00:46 A.M. US Mountain Standard Time,  
dixie at westpoint.tv writes:

Hi List
 
Here is a trick I have used with half inch tapes, I have a dual standard  
Panasonic DVD recorder which acts as one of the best TBCs I have seen,  put 
in any old signal, and it outputs broadcast PAL or NTSC, (depends on  which 
standard is selected). It is useful to have a variable attenuator on the  
input. Dont forget to pass the sound through it as well to keep it in sync  !
 
Jobs a goodun
 
  
David Dean
Westpoint Television
Archiving Services 
2" Quad , 1"  B, 1"C, D1, D2, D3, D5, HDCam and HDV 
.5", EIAJ, In Various Standards  where supported
Alchemist Ph.C conversions with Clean Cut
Snell and  Wilcox Ukon for HD frame rate conversions and Up and Down  
conversions
Digital Vision DVNR with scratch  and dropout  concealment
Tel 020 8742 3400 

----- Original Message ----- 
From:  _Chill315 at aol.com_ (mailto:Chill315 at aol.com)  
To: _quadlist at quadvideotapegroup.com_ 
(mailto:quadlist at quadvideotapegroup.com)   
Sent: Tuesday, December 13, 2011 1:35  PM
Subject: [QuadList] What to do with 1/2  inch tapes and proc amps


This is a good discussion regarding 1/2 inch tapes.  I hope I  do not get 
too verbose with this answer.
 
The EIA-J tapes may be a real problem.  The first step is to look  at the 
raw video on a waveform monitor.
 
Is the sync even interlaced?  Some of the early cameras were just  free 
running horizontal oscillators and vertical locked to power line.
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.
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.  
 
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.
 
There are video DA's that have sync stretch in them, that may be  something 
to try.
 
What will the proc Amp do for you?
 
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.  
 
What will be the bad things it will do?
 
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.  
 
If not RS-170 sync it will burp a lot if it only works with RS-170  sync.  
Again never, never land.
 
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.
 
Where do you put it in the chain?
 
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.
 
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.
 
Chris Hill
WA8IGN





 
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