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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: HDTV: Feasible?
Message-ID: <1991May27.181213.194@milton.u.washington.edu>
Date: 27 May 91 18:12:13 GMT
Article-I.D.: milton.1991May27.181213.194
References: <1991May24.222600.1988@murdoch.acc.Virginia.EDU> <okeJ32w163w@zl2tnm.gp.co.nz>
Organization: University of Washington, Seattle
Lines: 25

In article <okeJ32w163w@zl2tnm.gp.co.nz> don@zl2tnm.gp.co.nz (Don Stokes) writes:
>cfk6u@fermi.clas.Virginia.EDU (Charles F. Kramer) writes:

>> HDTV: Feasible?

>No.  Not under current bandplans.

	It's not clear that this sort of thing is infeasible.  Standard
TV transmission includes NO data compression of any sort, and the signal
usually has a lot of information that either (1) is repetitive of other
parts of the screen or (2) is repetitive with respect to the previous
(in time) frame.  
	Variations on conditional-update and difference-signal techniques
can easily compress this sort of signal.  Much of HDTV's promise
resides in the low current cost of memory to buffer a video screen's
information so that the signal from the transmitter need not
be a continuous set of full-screen updates.

	Of course, the BEST schemes would require a lot of fancy 
decision circuitry at the transmit end, and would not be compatible
with current receivers.  We (USA) may see UHF stations with a HDTV signal
with duplicate VHF transmissions that remain NTSC (for _Never _Twice
the _Same _Color :-)    ).

	John Whitmore