[opendtv] Re: "we'll forever be stuck with by going ATSC"
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 12 Jan 2005 10:50:38 -0500
At 2:49 PM -0500 1/11/05, Manfredi, Albert E wrote:
>As of now, although I don't have the numbers, I suspect
>that the very *vast* majority of ATSC users are HDTV
>users. *Because* that is what differentiates ATSC from
>NTSC, as of today, for the most part.
Good start Bert. Yes, NTSC and HDTV are VERY different.
Obviously, as you correctly stipulate on a regular basis, there is
little incentive to buy an ATSC receiver for an existing analog TV.
You may enjoy an improvement in SDTV quality that parallels the
difference between watching a movie on VHS versus DVD.
In fact, this is exactly what the Europeans decided to do; they took
a baby step, first eliminating many of the most objectionable
artifacts of PAL encoding, while simultaneously upgrading receivers
to take full advantage of the component digital signals that are
delivered - but typically connected to the display via analog
component inputs. And they added the ability to deliver content in
widescreen 16:9. As we are learning, many of the new displays being
sold in Europe are indeed HD capable - the primary exception is
direct view CRT displays, which are incapable of delivering the HDTV
viewing experience because of their size and limited resolution.
The only incentive today to buy an ATSC receiver is IF you own an
HDTV and do not have access to HD programming from any source other
than local broadcasters. This appears to be the motivation for the
handful of early adopters who represent the small installed base of
ATSC receivers today.
> > > In the US, we have (and will have increasingly)
>> > low-cost receivers that can decode HD content. These
>> > are in part low cost because they are sold in large
>> > quantities.
>>
>> Do you have any facts to support this statement.
>
>Can you point to a single other example of HDTV STB that
>costs $176 to consumers? From any country? Or built-in
>receiver HDTV chipset that costs $37 to the OEM?
What is your point? Obviously these capabilities are and have been
available at SOME price point. It is equally obvious that this price
point is coming down, although the average price for an ATSC receiver
is considerably higher than $176 at retail. What is not obvious is
the large quantities of these boxes that HAVe been sold, or any
trends that suggest that a large number of these receiver will be
sold in the future.
>These low prices are only the result of large quantities
>either now or soon to be expected.
No Bert, they are a reflection of the real costs to produce DTV products.
There is only ONE component in an ATSC receiver that is NOT being
produced in large quantities - the 8-VSB demod/equalizer. MPEG-2
decoders, both MP@ML and MP@HL are being produced in large quantities
for digital cable and DBS boxes. QAM demods are being produced in
HUGE quantities for digital cable STBs; the DBS demod is similarly
being produce in huge quantities. And all of these components (except
for MP@HL decoder chips) are being produced in huge quantities for
DTV deployments around the world. Still, according to Bob Miller, the
cost to USDTV for a STV is $150...not much margin, but for this
application, the cost of the receiver is being subsidized by the
subscription fees.
Yes there is anticipation that the FCC receiver mandates will lead to
large quantities of ATSC receivers being produced. To date, however,
this has not been the case. The vast majority of HDTV capable
products covered by the first phase of the FCC mandates did NOT
include ATSC receivers. You can lead the cattle to the water, but the
government cannot force them to drink.
>Obviously. Anything 1 Mpel or greater, in a TV display,
>is HDTV by definition. What deterimines HD is the
>resolution of the display. Size and viewing distances
>are only incidentals.
Sorry Bert, but you are completely wrong.
Before proving this, please answer this question.
How many people would pay >$5 for a ticket to go to a theater where
hundreds of people would sit and watch a 70-80 inch plasma panel at a
viewing distances of 10 to 80 feet?
Going to the movie theater IS about the viewing experience.
The development of HDTV WAS and IS all about the HDTV viewing experience.
YOU are confusing HDTV and DTV.
DTV can deliver HDTV as an application, but HDTV is NOT a
requirement, even here in the U.S.
The HDTV viewing experience is based in the laws of physics and the
requirements of the human visual system. The following description
by Professor Kelin J. Kuhn SHOULD BE sufficient to prove you wrong
http://www.ee.washington.edu/conselec/CE/kuhn/hdtv/95x5.htm
The basic concept behind high-definition television is actually not
to increase the definition per unit area ... but rather to increase
the percentage of the visual field contained by the image.
The majority of proposed analog and digital HDTV systems are working
toward approximately a 100% increase in the number of horizontal and
vertical pixels. (Proposals are roughly 1 MB per frame with roughly
1000 lines by 1000 horizontal points). This typically results in a
factor of 2-3 improvement in the angle of the vertical and horizontal
fields. The majority of HDTV proposals also change the aspect ratio
to 16/9 from 4/3 -- making the image more "movie-like".
It should be obvious that increasing the image definition per unit
area was not the main problem that NHK was trying to solve. NTSC DOES
present a sharp image to the viewer when the screen size and viewing
distance are within the design parameters of the system. The design
parameters for NTSC were to deliver about 21 cycles per degree of
resolution on a 19" screen viewed at seven picture heights, covering
just less than 11 degrees of the human field of view.
When you INCREASE the screen size while holding the viewing distance
constant, as has been the trend for NTSC displays for the past five
decades, the system falls apart. There is inadequate resolution per
unit area and all kinds of scanning artifacts become perceptible.
When you DECREASE the screen size of an HDTV display the system ALSO
falls apart. There is simply too much detail per unit area for the
viewer to resolve at a comfortable viewing distance. MOre important,
the HDTV induction effect DOES NOT occur on smaller screens at ANY
viewing distance.
hjere is another definition of HDTV. This one comes from the SMPTE
TAsk Force Report on Digital Image Architecture, for which I was the
editor, and writer of much of the document:
http://www.pcube.com/pdf/Report%20of%20the%20SMPTE%20TFDIA.html#3.3.1
* High Resolution - systems designed to deliver images over a
wide field of view, with high spatial and/or high temporal
frequencies, typically have resolution requirements near the limits
of human visual perception. Applications include: motion picture
delivery in theaters; entertainment and information presentations to
large audiences; and personal computer displays.
The report clearly defines the relationship between screen size,
viewing distance , and resolution requirements.
5.2 Designing Display Systems to Deal with Multiple Spatial
Resolution Requirements
The perceived resolution of a display is determined primarily by the
viewing distance and the visual acuity of the observer. Visual acuity
is often determined using sets of alternating black and white lines
of equal width. One black/white line pair represents one cycle. The
number of cycles that can be resolved across one degree of the eye's
viewing field is typically used as a measure of human visual acuity,
and is stated in cycles (line pairs) per degree. Under some
conditions, with high contrast line pairs, human visual acuity extend
beyond 40 cycles per degree; approximately 22 cycles per degree is
perceived as a sharp image.
If the resolution of a display is held constant and the viewing
distance is a variable, the resolution perceived by the viewer -
measured in cycles per degree - will increase as the viewer moves
away from the display. Therefore, all displays can be considered to
be high resolution if viewed from an appropriate distance.
At a distance the varies with the visual acuity of each individual,
the actual resolution of the display equals the limit of that
viewer's ability to resolve image detail. Beyond this viewing
distance additional image detail cannot be perceived; that is, the
display has more resolution than is required for this viewer and set
of viewing conditions.
In some cases excess resolution may be desirable. For example, the
operator of a personal computer can typically reduce the viewing
distance to a high resolution desktop display by one-half, simply by
leaning forward, thus taking advantage of additional resolution
improves enough to be significant, while moving 15 inches in a movie
theatre would have little effect on perceived resolution.
The NTSC transmission standard was designed to provide a resolution
of approximately 21 cycles per degree over a viewing field of just
under 11 degrees. Display size can be variable in today's television,
ranging from a diagonal of a few inches (a personal display) to more
than 30 feet (direct view displays in stadiums and projection
displays in controlled lighting environments). These displays differ
only in the size of their pixels. At the appropriate viewing
distance, the perceived resolution of the personal display and the
stadium display will equal the design goal of 21 cycles per degree,
and both displays will cover 11 degrees of the observer's field of
view.
So Bert is correct. Small displays can indeed deliver high
resolution. But he is incorrect in calling them HDTV displays,
because they are incapable of delivering the HDTV viewing experience.
But wait, there is more...
http://web-star.com/hdtv/publiced.html
The following was developed by the Japanese public broadcaster NHK in
the 1970s when they conducted their basic research into the
requirements for HDTV display.
The HDTV viewing experience requires a display that:
A. delivers what is perceived as a sharp image at the
designed viewing distance--the ability to resolve horizontal,
vertical and diagonal spatial details with a resolution equal to or
greater than 22 cycles per degree;
B. delivers static and moving images that are free of artifacts
that interfere with the perception of the original source material.
C. covers at least 30 degrees of the field of view.
NHK found that a viewing distance in the range of 3.3 picture heights
and an aspect ratio of 3:2 would produce what they called "the
induction effect." This is the point at which the human visual system
responds to the images as if we were seeing a real-world event, and
it requires a big screen that covers a large portion of our field of
view. The induction effect also seems to be sensitive to viewing
distance; although it is possible to meet all of the criteria above
with a direct view display, it doesn't work when the eyes must focus
on an image plane that is very close, as is the case with a computer
display. One European study, where viewres were allowed to position
themselves at any distance from the display, found that on average,
people would not sit 3 picture heights from a display until it had a
screen diagonal above 100 inches, at a viewing distance of
approximately 17 feet.
NHK also reported that picture impairments from interlace and other
forms of aliasing are the biggest barrier to the perception of a high
definition image. The removal of picture impariments makes the
largest contribution to the perception of a high quality image. This
finding appears to be an important factor in why consumers rate the
MPEG-2 encoded images from DirecTV and the Dish Network so highly,
despite the fact that they contain no more resolution than a good
NTSC image--these digital images are free from the impairments of
NTSC encoding...but not interlace artifacts.
NHK found that progressive scanning of the display was highly
desirable, as it reduced picture impairments, allowing the source
image samples to be seen properly. These studies suggest that a
progressive scan image with about 700 lines is adequate to deliver
the HDTV viewing experience.
And yes, Bert, I wrote this article too, but I have all of the NHK
documents to back it up.
>I can choose to view a 36" HDTV display at a distance
>of 3 picture heights, and have a great HDTV
>"experience," as you put it.
NO, you will not have a great HDTV viewing experience, as I and NHK
and others have defined it.
You WILL see a high resolution image on a smallish screen that covers
close to thirty degrees of your field of view, but you will NOT
experience the induction effect. What's more, most people feel very
uncomfortable watching a 36" display at 3 picture heights, which is
approximately 52 inches. My friend Dan has had a 36" Sony HD capable,
direct view CRT display for four years. He has Cox HD. He sits 10
feet away for several reasons:
1. This is the viewing distance where the display looks sharp for HD
- SDTV still looks a bit soft, but is significantly improved thanks
to the deinterlacing.
2. It's difficult to place an L shaped "sofa pit" and coffee table
just four feet from the display.
Sorry Bert, but screen size and viewing distance ARE critical factors
for the HDTV viewing experience...by definition.
Regards
Craig
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