[QuadList] NEC TBC

[Chill315 at aol.com]

No easy way to compare TBC's.  There are a couple of things to look  for.
 
1    8 bit or 10?  If 10 more quantizing levels to  allow better pictures.
 
2    What is window?  For a vertical lock machine,  It only has to be one 
line.  Then you have the issue of providing advanced  sync to the machine to 
get the correct time out of the TBC and stay centered in  the window.
 
3    Direct color always has a better bandwidth so thus  more detail and 
quality of picture.  But the real issue is how good are the  filters.  The pre 
A-D filter has to be wide enough to not cause artifacts  and yet keep the 
video below the Nyquist frequencies.  The post D-A filter  has to be good 
enough to prevent ringing yet smooth out the samples and keep  bandwidth flat.  
These are tradeoffs that are made during the design of a  TBC.  More with 
cost than anything else.  I say that because it  depends on the market that 
you are marketing the TBC to.  
 
4    Sample rates are always better at higher  numbers.  4X subcarrier is 
one that is popular in NTSC because you can do  some tricks in the color 
process.  Also if you are doing any size changes  it makes the math easier.
 
5    A TBC that is designed for heterodyne process will  always look worse 
than a direct one on a non heterodyne signal.  Just the  nature of the 
filters for Chroma and Luminance processing.
 
Those are my thoughts.  And I am no expert.  These are just  observations 
over the years.
 
Chris Hill
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