🚀 go-pugleaf

In article <599@limbic.UUCP>, gil@limbic.UUCP (Gil Kloepfer Jr.) writes:
> 
> 	1.  Are there any FCC regulations or industry standards
> 	    which govern the VBI, and how signals are to be
> 	    superimposed here?

The FCC says where.  The what is up to the originator.  There are a couple
of systems used in the US.  NABTS is defined in an EIA standard.  The
version I have is called an interim standard (IS-14).  It may be real
by now.  World Teletext is derived from the UK system.

> 
> 	2.  Specifically, how is closed captioning transmitted?  Is
> 	    it data, or a slow-scan representation of pixels to be
> 	    overlayed on the TV picture?

ASCII.

> 
> 	3.  What is the best way to get at the information on the VBI?
> 	    Specifically, what is the best way to detect the start
> 	    and end of the "dead" portion where information would be
> 	    transmitted?

Most signals have a distinctive header that exists in a fixed relationship
to the horizontal sync.  Just look at every line to see if it fits.

A quick browse thru "Television Engineering" by Benson will give you a lot.
For the WTS system, try the Signetics Linear Data Book volume for Video
products.

markz@ssc.uucp