[Vision2020] Digital Television:HDTV:1080 Interlaced/720 Progressive

[Ted Moffett]

All:

One technical fact of importance that was omitted, unless I missed it, in 
Sam's description of HDTV, was that the HDTV standard indicates 720 line 
PROGRESSIVE SCAN or 1080 line INTERLACED SCAN.  There is some debate among 
videophiles as to which of these technical HDTV standards of scanning gives 
the best picture.  But the 1080 interlaced picture is not necessarily better 
than the 720 progressive picture due to the increase in lines:  Interlaced 
scanning is, line for line, inferior to progressive scan.

The NTSC standard we have been watching for years for televised on air 
broadcasts is an interlaced picture, which means that one set of scan lines 
is run, then another set of scan lines that alternates with the first set 
are run a split second later, and the two sets of lines are "interlaced" or 
"woven together" to create the picture.  This process was used to allow a 
picture to be fitted into the available analog capacity of the broadcast 
signal at the time the NTSC standard was set.  But interlaced scanning 
causes errors in picture display that progressive scan does not.

Progressive scan runs the scan lines all in one pass continuously, creating 
a more seamless, film like picture.  But if you increase the scan lines on 
an interlaced display, interlaced scanning can compete in picture quality 
with progressive scan, thus the 720 progressive scan or 1080 interlaced scan 
standards for true HDTV, that in fact many so called HDTVs on the market 
CANNOT in reality display!  These HDTVs will of course accept and allow 
viewing of HDTV signals and give a wonderful picture, but a technical 
analysis of the actual viewable scan lines will demonstrate that the monitor 
is not showing full 720P or 1080i.  CRT display of true HDTV at the 
brightness levels people want in their homes is problematic.

As far as I know, computer displays are always progressive scan.  So if you 
are comparing the quantity of scan lines between different picture displays, 
you must know if you are comparing interlaced scan to progressive scan, to 
really judge the differing quality of the two displays.  A computer display 
scanning progressive needs many fewer scanning lines for the same quality of 
picture that a TV monitor will display scanning interlaced.

Ted





>From: "MoscowSam" <MoscowSam@moscow.com>
>To: <vision2020@moscow.com>
>Subject: [Vision2020] Digital TV is in Moscow, now ....
>Date: Thu, 17 Apr 2003 13:42:39 -0700
>
>I haven't been reading all the V2020 posts lately; there are so many!
>
>So maybe I missed some content on the "Digital Television" thread. If
>I am repeating what has been said already, then just DELETE.
>
>KUID now broadcasts digital television on Channel 12 with four different
>content channels during the day until 4 p.m. Yes, that is four separate
>digital "channels" in the bandwidth of what was just one analog channel.
>Public television is making very effective use of its channel allocation!
>
>12-1 is the digital version of the "regular" analog channel program (now
>over the air on Channel 35); 12-2 is "PBS Kids"; 12-3 is "Learn" which is
>educational courses, I presume for credit; 12-4 is "Citizen" which seems
>to focus on news and issues.  These four are in "standard" 4:3 aspect
>ratio to which those of us who watch TV are accustomed.
>
>At 4 pm, 12-2, 12-3 and 12-4 are shut down, while 12-1 continues
>with the addition of 12-5 in high definition, often in wide-screen
>format.
>
>If you have not seen wide-screen high-definition TV on a large television
>screen, then you are in for an experience when you do.  Ordinary analog
>television may display 350 lines or so of discernible definition.  KUID's
>12-1, 12-2, 12-3 and 12-4 probably are 480 lines, while 12-5 is 1080.
>Yes, that is 1080 pixels, vertically.  In wide screen format that should
>be 1920 x 1080 pixels.
>
>Compare that to the settings of your computer's monitor.  The
>most common computer monitor setting probably is 800 x600 pixels
>while quite a few are 1024 x 768.  Some folks with big computer
>screens and good close vision even set theirs to 1280 x 960.
>
>Hence 1920 x 1080 on a big, wide-screen TV is truly spectacular.
>
>Apparently we will have the addition of KWSU by the end of May.
>Lewiston has been on the air in digital format for a while on
>Channel 32, but their signal is not strong enough for me to
>get a picture at my home on Indian Hills Drive in Moscow.  I
>believe that KLEW-DT does not broadcast in high definition nor
>in wide screen format yet.
>
>These over-the-air broadcasts are "free".  E.g., you do not
>have to subscribe to a satellite TV service to get them, nor
>can you get them via local cable.  You have to have an antenna
>and a "set-top box" or a TV with an "integrated" digital signal
>tuner.  And that is the rub to receive and view these fine
>broadcasts; the cost right now is high for the special gear
>required.
>
>I checked two stores while in Portland a few days ago.  The lowest
>cost for an over-the-air digital receiver was priced at $399.  That
>was without DirecTV or Dish TV capabilities.  Set-top boxes with
>the additional satellite abilities run from $500 to $850 and
>maybe more.
>
>There is more than one store in Moscow that has high-definition,
>wide-screen TV's available.  They are of excellent quality.  If
>you are curious, visit these stores and you can see for yourself
>the difference between conventional/analog TV and the new mode
>now emerging.
>
>I agree with Shawn.  Once analog, over-the-air television broadcasts
>cease, prices for digital to analog converters to use with existing
>TVs should come down drastically because many makers will want a
>piece of the market and competition will do its thing to lower prices.
>
>If you lament what is being foisted on the U.S. public in the way
>of new television broadcast standards, then those of you old enough
>to remember, please think back to the advent of color television.
>Same thing as now:  Few channels carrying color, few programs, high
>prices for color TV's.
>
>Would you rather, now, still be watching black and white broadcasts
>on TV's of 1960's quality?
>
>Yes; I suppose I am a vidiot.
>
>Sam Scripter
>Moscow
>
>----- Original Message -----
>From: "Shawn Clabough" <shawnc@outtrack.com>
>To: <vision2020@moscow.com>
>Sent: Thursday, April 17, 2003 12:58 PM
>Subject: RE: [Vision2020] Digital television
>
>
> > Don't confuse a digital signal with HDTV.  Although HDTV is digital, a
> > standard resolution picture can also be digital, which is what many 
>stations
> > will be moving to first.  These standard resolution converters should be
> > relatively inexpensive. Cable boxes and satellite boxes are already 
>doing
> > this conversion for many people.  Only if you want over-the-air 
>broadcasts
> > would you need an additional box.
> >
> > Shawn
>
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