[opendtv] Re: Disney to Sell Moviebeam

The www.dotcast.com website described adding a reduced level QAM carrier onto 
the visual carrier.
They claim that since it is "in-quadrature" to the video signal, it would 
result in essentially zero signal at the output of an NTSC detector.
Seems to work similiar to how the in-phase portion of a QPSK data signal will 
not be seen by a quadrature detector and vice versa.
 
Hence it is not in the vertical blanking interval, nor is it "between" the 
Visual and Aural carriers.
It's yet another signal that is added onto the Visual carrier.
 
Very clever scheme.....or Kludge....in either case it's days are numbered.
 
                                <holl_ands>
 
==============================================================
Doug McDonald <mcdonald@xxxxxxxxxxxx> wrote:
John Shutt wrote:
>The press release said unused portions of the television spectrum, not 
>unused portions of the television picture. MovieBeam is/was not based on 
>vertical interval blanking. It was based on placing digital information in 
>the spaces between the Visual and Aural carriers.
>
>www.dotcast.com
> 
>


That web site implies that TV sets use some sort of synchronous (PLL?) 
detection of the
video. Huh? I've never seen a TV schematic that did not use a plain 
diode detector. Of course,
I stopped looking before ICs arrived. What the web page describes is a 
kludge QAM
system.

Doug McDonald




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