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From: lief@hpfcrs.UUCP (lief)
Newsgroups: net.video
Subject: Re: Orphaned Response
Message-ID: <19300001@hpfcrs.UUCP>
Date: Sat, 9-Mar-85 12:13:00 EST
Article-I.D.: hpfcrs.19300001
Posted: Sat Mar  9 12:13:00 1985
Date-Received: Fri, 15-Mar-85 05:34:32 EST
References: <-198900@sun.UUCP>
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Nf-ID: #R:sun:-198900:hpfcrs:19300001:37777777600:2589
Nf-From: hpfcrs!lief    Mar  7 09:13:00 1985


     Digital TV has been around since around 1981, over in Europe.  However,
its only been recently introduce in the USA.  In fact, I believe that the
first commercially available digital TV in the USA just started selling last
month (a Toshiba model).  Panasonic plans to introduce theirs in April.  
Zenith also plans to introduce one this year.

     Virtually every digital TV is using the ITT digital chip set.  This chip
set samples the composite video input at 14.3 MHz for NTSC (17 MHz for PAL),
digitizes the data into pseudo-8-bit resolution, and then procedes to process
it.  It does fancy things like noise inversion to get rid of specking due to
interference.  The luma data and the chroma data are then digitally seperated,
with the chroma data in the form of R-Y and B-Y.  After processing, the digital
R-Y and B-Y data (each 8 bits), and the 10-bit luma data are all put through 
D/A converters and then fed through the RGB matrix to drive the monitor.
The low bandwidth of chroma data allows it to be multiplexed on a 4-bit wide
bus.  Likewise, the luma data is actually transferred on an 8-bit wide bus,
with the least significant bit of the 8-bit path modulated according to the
least significant 2 bits of the 10-bit word (understand what I mean?).  In
otherwords, they make good use of time averaging (rather than numerical
averaging) to save on circuitry and connection pins.  Real slick.

     The Toshiba set is really a little disappointing in the picture quality.
Either they are not using all the available capabilities of the chip set, or
they don't have the latest revision.  It's probably a function of both.  ITT
just started shipping the latest rev. of their chip set to the TV makers
and so I don't think they could possibly be implemented in the Toshiba model
yet.  The latest rev. allows more features and corrections, allows 2 video
input sources, uses a new clock design (to eliminate RF interference which
their previous clock circuit is hampered with), etc.

     Personally, I am very exited about these chips.  If used correctly,
they should really enhance the quality of TV.  However, don't expect these
chips to perform miracles on the already bandwidth limited video input.
About all you can expect is that your picture quality will be precessed to
the limit of the carrier bandwidth.  In fact, Zenith plans to sell their unit
as a 'high res' TV, where they double the number of scan lines.  Actually,
all they are doing is interpolating between actual scan lines.

     Yes, I believe it is worth the wait.

Lief Sorensen
Hewlett Packard Co.