-
Archived
Tech-Notes
Published by: Larry Bloomfield & Jim Mendrala
The following are our current e-mail addresses:
E-mail = hdtvguy@garlic.com
or J.Mendrala@ieee.org
We have copied the original Tech-Notes below as it
was sent out. Some of the information may be out of date.
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Tech Notes
Published
by: Larry Bloomfield & Jim Mendrala
E-mail
= HDTVGuy@aol.com or J.Mendrala@ieee.org
January 24, 2000
Our First Tech Note of the
New Year
Tech Note – 049
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Talent
does what it can, but genius does what it must!
Our Mission: Sharing experiences,
knowledge, observations, concerns, opinions or anything else relating
to Electronic Cinema, DTV, etc., with fellow engineers and readers.
We do hope that everyone will participate with comments, experiences,
questions and/or answers. Please note the new E-mail addresses.
To remove yourself from this list, send an E-mail to: HDTVGuy@aol.com
in the subject place the word Remove. We now have over 570
subscribers & growing. This is YOUR forum! The
Tech Notes are posted and past issues available at: http://www.SCRI.com
and http://www.hdpictures.com.
**********************************************
Subj: A
Job Well done!
From: Gerald Brown
While yes, I am a European; my comment was not a nationalistic sentiment.
But what interests me is the one point you make that you say you
did not have access to the BBC. Neither did I.
I am in Greece and watched segments that originated from ABC and
PBS as well as dozens of TV stations and networks worldwide. But
above all the Greek stations had the courtesy to thank the BBC time
and again for its central role in planning and coordination for
making this amazingly smooth broadcast of some 25 hours a true technological
achievement.
I am sure you saw the London, Berlin, Rome, Athens, Sydney, Kiribati,
ANTARTICA etc segments (courtesy as you mentioned of either/both
the ABC and PBS)..
BBC London was, I believe the nerve center for all the planning
and execution for the worldwide broadcast.
I hope you will appreciate, and take into account, that your newsletter
emails are read outside of the US. Non-US readers' perspectives
can be very different to those of a domestic US audience...as you
know too well from the debate over DVB and ATSC issues.
Regards and a profitable year ahead for us all.
Gerald - mgbhk@hkstar.com
PS. As an interesting aside...where would CNN's much touted Millennium
coverage have been without the BBC coordinated feeds?
**********************************************
Subj: HDTV
on big screens
From: Wade Ramsey
Thanks for your technical rundown on the TI and Hughes systems.
But there is a small side issue in your article that is one
of my pet peeves, and that is the use of the term "subtractive
primary" to refer to what are secondary colors (CMY.) As you
point out, the whole color theory scene is confusing enough. Please
don't muddy it even more by designating secondaries as primaries.
Wade Ramsey, DP -- Div. of Film, Video, and Broadcasting
-- Bob Jones University, Greenville, SC
In
response to Wade Ramsey from Jim Mendrala
I agree with you the Yellow, Cyan and Magenta (YCM) are in reality
secondaries not primaries. But YCMs are what some consider the opposites
of the Red, Green and Blue (RGB) primaries and are sometimes called
"secondary primaries". The eye is sensitive to RGB not
YCM. YCM absorbs blue red and green respectively. Thanks
for the comments. Jim
****************************************
Subj: Colorimetry
for Digital Mastering and Digital Cinema
By:
Jim Mendrala
Digital
Cinema at this time is in its infancy. Thousands of people have
seen demonstrations of Digital Cinema in about a dozen or so theaters
across the country. All of these demonstrations have been plagued,
however, by the lack of a Digital Master Colorimetry Standard. The
Society of Motion Picture and Television Engineers (SMPTE) has organized
a Task Force on Digital Cinema, chaired by Curt Belhmer. He has
organized the task force into eight study group committees--one
committee for each part of the digital cinema process. The committees
range from the Mastering committee through the Projection committee.
However, there is not any committee on colorimetry.
In
order for Digital Mastering to work, we must look at the overall
digital cinema system. The committees must formulate requirements
on how film images will get from a piece of film on through the
electronic media into a theater and then projected onto the cinema
screen. The committees must also be aware of other uses of those
images from a Digital Original Master.
At
this time, all images are recorded for some form of television,
including HDTV, CRT type of display. Only a select few are being
reworked to accommodate something other than a CRT display and projected
on to the motion picture screen.
If
it weren’t for the 2K DaVincis and Pogels, digital cinema colorimetry
would be in very big trouble.
Consider
this. All telecine transfers, both HDTV and SDTV are designed to
feed basic color equations for television CRTs. If you want to go
to any other type of display device with a gamma different from
that of a CRT, that gamma must first be removed. That is easier
said than done. Digital cinema projectors, such as the Texas Instrument
(TI) Digital Light Processing (DLP) Cinema projector have Digital
Micromirror Devices (DMDs) with linear transfer functions and do
not want or need CRT gamma corrected signals.
RGB
signals need to be first normalized so that the relationship between
the RGB signals and the CIE tristimulus XYZ are defined. In a true
digital world, the basic RGB tristimulus signals still need to be
normalized, but the transformation to other display primaries needs
to done in the display devices themselves. The basic RGB normalized
digital signals should not be converted to signals intended for
CRT display. They should be kept in their basic normalized linear
format so that later the display devices themselves can convert
those signals to display properly.
Reference
white for television cameras and displays is CIE illuminant D65.
The chromaticities of D65, rounded to four significant digits as
per CIE 15.2 (1986) are:
x
= 0.3127 and y = 0.3290
Reference
white for film cameras and displays is CIE illuminant D55. The chromaticities
of D55, also rounded to four significant digits as per CIE 15.2
(1986) are:
x
= 0.3324 and y = 0.3474
As
you can see, television is not intended to be displayed with CIE
illuminant D55 and film was not intended to be displayed with CIE
illuminant D65. This can only be accomplished through basic color
equations. These equations are defined but are being implemented
today at the wrong points in the system. We all know that film on
a telecine looks great on a CRT monitor but when displayed on a
linear device looks pretty bad. The blacks and mid ranges look too
thin and are generally noisy. This is because a gamma of 0.45, intended
for a CRT, is present and is compensating for the natural black
compression of a CRT display device. In order for the recorded HDTV
digital images to display correctly on a linear display device,
similar to the TI Digital Cinema projector, the gamma for the CRT
must first be removed from the signal. This is not an easy task
and is prone to all kind of errors. It would not have to be removed
if the telecine device hadn’t put it there in the first place.
What
has to change is where we insert the gamma correction, if needed,
for the display device. Since the Digital Master Original does not
know where it will ultimately be used, it only needs to output normalized
linear RGB signals. These linear signals later, when converted to
SDTV, can have CRT gamma added. The same holds true for HDTV with
its slightly different gamma. In ITU-R BT.709, HDTV gamma is defined
as being linear up to 0.018 or slightly less than 2% and with a
gamma of 0.45 for anything greater than 2% on up to 100% signal
level. In Digital Cinema, however, with a linear display device,
no gamma correction would need to be inserted.
A
Digital Master Original would contain in a DPX file format the data
images at whatever frame rate, resolution and color pixel depth
for each frame. From this Digital Master original, it could be converted
to all of the various formats in use today including, SDTV, HDTV,
Digital Cinema and film recording. For SDTV such as NTSC, PAL and
SECAM, a gamma of 0.45 can be added to the three RGB tristimulus
values creating the three nonlinear primary components, R’, G’,
and B’. For HDTV, anything over 2% can have added a 0.45 gamma creating
three nonlinear primary components in accordance with ITU-R BT.709
and SMPTE 240M. For Digital Cinema applications, no gamma needs
to be added to the three tristimulus RGB signals, as the projection
device will insert whatever it needs, if anything, for its display.
For
film recording applications, the film recorder would insert whatever
curve is needed to achieve the desired look. Film recorders record
negatives with a slope of approximately 0.45 and include a “Knee”
and a “Toe” region. A print with a slope of about 2.2 also has a
“Knee” and a “Toe”. An intermediate, such as an Inter-Positive (IP)
or an Inter-Negative, with a slope around 1.1 has a “Knee” and a
“Toe” also. The curve resembles somewhat of an “S” curve. This “S”
curve is part of what is commonly referred to as “The Film Look”.
In
conclusion, Digital Mastering needs to address the colorimetry issue
by first normalizing the RGB data so that the data stored therein
can later be manipulated through basic color equations and derive
the necessary RGB signals to drive the various additive type displays
with other sets of primaries and/or other white points. In the future,
this basic information will be manipulated within the display devices
themselves to display as close as possible a consistent colorimetry
similar to what the graphic arts and print industry are doing today.
****************************************
Subj:
The Outback
By:
Brian Park
In my new role as a projector reseller, it has become very apparent
in my dealings with the public and business here in Central Texas
that no one has a clue about HDTV. They've heard of it, never seen
it, don't know what's coming, etc. Being a third tier city, although
a very hi-tech one, with a lot of “techies” and home theaters, we
won't have HD broadcasts or HD cable for a few years, but we can
get satellite today. And progressive DVD.
I'm thinking about putting some demonstrations together at one of
the art galleries to promote HDTV here, primarily to educate, but
with a little plug for the company I work for. I want to put together
a system based on the new Sony and/or Epson projectors and a Dolby
sound system, but wonder what content and media I should use. Should
I use the Panasonic digital VCR, with its associated STB, or content
taped (how?) from DirecTV from the RCA box, or should I find some
720p content that demonstrates these 1300 x 720 pixel projectors?
Any broadcasters willing to send us some tapes? I don't want to
use professional gear, like D5, but equipment that the consumer
will use.
Any ideas would be welcome.
Brian Park - floman@eden.com
**********************************************
Subj: "TELEVISION
IN THE SPRING" (Is history repeating itself?)
By: H.W. Secor"
Reprinted from the January, 1939 issue of RADIO and TELEVISION Magazine
(Illustrations omitted) "David Sarnoff, President of the Radio
Corporation of America, has made the statement that television will
be ready when the New York World's Fair opens in the spring. Other
signposts, along the avenue of television which point to a great
activity shortly in this newest radio art,
are that several of the leading radio set manufacturers are starting
to build television receivers of the HOME type. Further, RCA
has announced that they are ready to supply television transmitters,
a 1 kilowatt unit, at a cost of about sixty thousand dollars (1939
monetary rate). A number of new licenses, for the erection of experimental
television stations, have been granted by the F.C.C. So, all in
all, it looks as if television will surely make its debut early
this year, and several well-known radio authorities have voiced
this opinion.
Television -- First Transmitters
The larger cities will, undoubtedly, be first to enjoy television
programs, and New York City will have two stations operating shortly
after the first of the year, the NBC transmitter, atop the 1300
foot Empire State Building, and the CBS transmitter in the Chrysler
Tower. Another station is to be erected by the Du Mont Laboratories
at Passic, New Jersey, about 16 miles from New York. Several Experimental
television station permits have been sought by the General Electric
Company. Chicago and Kansas City will soon have television
broadcasts, according to reports, and on the West Coast, the Don
Lee station, in Los Angeles, (W6XAO) has been active for many years.
The local broadcasting companies, in the larger cities,
will, undoubtedly, have to finance the erection, and the operation,
of television stations at first, until the F.C.C. grants regular
commercial licenses for these stations, so that sponsored programs
can be broadcast, and thus provide revenue to make the television
stations self supporting.
What To Expect In A Television Set
The RCA home television receiver has the picture tube pointed upwards,
reflecting off of a mirror mounted on a top hinged door that is
left at a 45 degree angle for normal viewing. By reflecting the
image off of a mirror, the horizontal scan rate must be reversed.
Of course, many experimenters, and radio fans,
will build kit receivers for the images, and several of these kits
have been on sale in the New York area for some time. To receive
an image about 3 inches by 4 inches, a receiving kit, complete with
a cathode ray tube, is available at a little under $100.00. For
half of this sum or less, the experimenter may build a set to pick
up the image of a smaller C-R tube, and the small picture may be
enlarged with a magnifying lens.
The cheapest start, in home viewing, is a model utilizing an image
receiver only, with no sound pickup. A combined image and sound
receiver is available for a slightly higher price. On the small
table type sets, the image will average about 3 by 4 inches and
these sets will probably cost about $125.00 to $175.00. Many
people ask whether their present broadcast, or all wave, receivers
can be used for television. No receiver, of this type, can be used
to pick up the image. A brand new, specially built television receiver,
capable of passing 1 ½ to 2 ½ megacycles, must be employed for seeing
the image. All wave receivers, which tune down to 5 meters, can
be used to pick up the sound channel, which will be somewhere in
the neighborhood of six meters (50-60 Megahertz).
Converters for "Sound" Pickup
Another arrangement, for both seeing and hearing television images,
will be to purchase a receiver for images only, and a 5 to 7 meter
short wave converter may be built, or purchased, for the sound channel.
This converter may be connected to your present day all wave receiver.
For a price, varying between possibly $250.00 and $350.00, a combined
television image and sound receiver, built into a console cabinet,
will be available. The size of the image, in this class of receivers,
will be 7 by 9 inches. Many of our readers have raised the
question as to whether a television IMAGE (picture) converter will
be available for use in connection with their broadcast receivers.
The answer is "NO," except for sound reception, as has
already been explained. In the price class of $350.00 and
up, there should be a console receiver providing reception of the
regular programs in the 200 to 550 meter band (standard AM band),
as well as the usual short wave broadcast bands. Two tuning dials
will probably be built into these receivers to facilitate the tuning
of such a great variety of stations, and one loud speaker will probably
be used, as only one type of station would be tuned in at any given
time. For those, who can afford them, a still more advanced
model will incorporate an electric phonograph along with the reception
on the television, broadcast, and short wave bands. Possibly, also,
these DeLuxe models will incorporate home talking pictures, using
either 8 or 16 millimeter film. On television receivers, costing
from $350.00 up to $500.00,
a larger cathode ray tube will be used, having a diameter of 14
to 16 inches and producing an image about a foot square. Images,
measuring up to 18 by 20 inches, will become available in more advanced
models by projecting the image onto a ground glass screen. Several
models, of this type, have been available on the European market
for some time, but the large image is not so bright on present models
and some means, of intensifying the brilliancy of the image, must
be found. Undoubtedly, some arrangement will be offered in
the near future, when a small high intensity C-R tube will be used
together with a projection lens and the image thrown onto a screen.
The present high cost of the large size C-R tubes will, in the future,
be reduced to a nominal sum. A New York Television Company
has already developed a further idea whereby a number of television
image receivers can be connected to a MASTER receiver for home or
public hall use. These secondary receivers are small units
of nominal cost and these are wired to the master receiver by means
of co-axial cable. Several years ago, Hugo Gernsback, the
editor, devised a
television receiver in the form of a pair of spectacles. Recently,
a similar idea has taken the form of a miniature television receiver,
somewhat resembling a French type telephone, the image being seen
at one end and the sound issuing from the other."
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Subj:
As Others See Us
By:
Larry Bloomfield
The plethora
of written material that crosses ones desk or is received electronically
in a day can be mind-boggling. In reviewing this material,
one begins to get a feel for what is real and what is smoke and
mirrors. One particular report was found to be very interesting
with respect to its perspective on the US migration into digital
television. Other analyst and forecasters have echoed similar
opinions.
The report, entitled
"Interactive and Digital Television: Issues in the Transition
Phase," was written by David Mercer, of Strategy Analytics.
The report says, among other things, that the mandate to move all
terrestrial television broadcasting over to a digital format by
2006 is on the verge of collapse, but goes on to say that the FCC
will most likely see analog frequencies being abandoned in 2013,
at which time most US households are expected to be viewing digital
television.
When Strategy
Analytics was contacted, in an effort to find out where Mercer got
his inside information from, we spoke to Strategy’s president, Harvey
Cohen. Cohen said that Mercer is the Strategy Analytics’ Director
of Interactive Home Service covering both North America and Europe
and is base out of the United Kingdom (UK). Although Cohen
didn’t say specifically, he lead us to believe Mercer’s prospective
was that of an informed consumer sharing his view with others.
You can’t help but wonder how someone in the UK could have a very
firm grip on the exigencies of the US broadcast industry as it relates
to the consumer, much less have any inside tracks of merit.
The report does
address the current turmoil over modulation standards as raised
by Sinclair and their now famous petition to the FCC, but goes on
to say that the technical standard issues has no relationship to
the lack of a proven business model for either HDTV or SDTV.
Those who are familiar with my writing in this venerable publication
know that the term “business model” is the mantra of the bean counters
and non-technical managers they have gotten too. According
to those who chant the “business model” opus, no one has come up
with the magic formula of how to relieve the viewers or users of
this new digital technology of their hard earned cash.
If you don’t
have something to watch high definition on, what good is all the
rest? Mercer says that HDTV receivers will always be too expensive
for mass-market adoption. Apparently proponents of this line
of thought are not familiar with the decreasing costs of products
when mass-produced over a period of time. There are many people
at the Consumers Electronic Manufacturers Association (CEMA) and
any number of their membership who would tend to take serious issues
with this philosophy and disagree with that point of view.
The report said
that terrestrial, standard definition TV, over the next decade is
under threat from both satellite and cable operators who are providing
“superior” digital services and will continue to lose viewers.
Mercer hasn’t apparently seen much local US cable service.
In any event, cable claims to have seventy percent plus penetration
into US households and satellite services are well over the ten
million mark, and cables’ move to digital is tantamount to a snails
pace. Very few areas have digital cable service at this time
and although satellite is digitally delivered to subscribers’ homes,
it is still an NTSC medium and can only offer the quality of NTSC,
as it would be seen in the studio. Mercer does see the Internet-based
online video distribution market eventually taking off.
The report takes issue with the fact that more than twenty five
percent of US households own three or more TV sets and says that
they rely on over-the-air analog TV signals. The fact of the matter
is that it makes no difference how the TV set gets its signal. In
the daily life of things to come, if the set doesn’t have digital
reception capabilities, it will need a converter.
Many who forecast
extended closure times for analog television have apparently lost
sight of the fact that the catalyst to all this is the Balanced
Budget Act, where in Congress sees the auctioning of the returned
analog spectrum as a fathomless pit of revenue to help fund the
federal government’s whims.
Mercer would
say that analog broadcasting is an anachronism in today's digital
world, but he says it also fulfills a public service role.
Far be it from me to suggest that Mercer’s thinking is antediluvian,
but then he’s not alone. All he has to do is watch most any housewife
when their soaps are on and he make take a much different attitude.
One key point Mercer makes as he draws a paraphrase from the closing
lines of “A tale of two cities,” he says: “Switching off NTSC is
going to be a far-far greater challenge than most people realize.”
This may be the only thing that is on track in the entire report.
The report says:
“Less than five percent of US households will be watching over-the-air
DTV by 2005.” Cohen wouldn’t put his wallet where his company’s
report is on this one when he was asked to lay a wager.
One way or another,
the folks at Strategy Analytics can rest assured that between the
hype from CEMA, the greed of Congress and America’s fascination
with “new and better,” the broadcasters will be on the air with
digital service by the end of 2006, analog television will be history
and the FCC auctioning arenas will be echoing with the sounds of
“sold to the highest bidder,” shortly thereafter. Those legacy
sets without a converter will make some mighty interesting doorstops
or boat anchors.
Strategy
Analytics' Web site is at http://www.strategyanalytics.com.
****************************************
(Ed Note:
Larry is still looking for some really good cutting edge technology
stories for BE’s pre-NAB March issue, like the one above. If you
know of anything happening in our industry that would be of interest
to the many engineers who read this fine journal, please contact
him by Friday, January 28, 2000 Thanks.)
****************************************
(Ed
Note: The Editors and Publishers of the Tech Notes wish
to thank Des Chaskelson, Research Director of SCRI International
for his generosity in posting the Tech Notes on the SCRI web site.
http://WWW.SCRI.com).
Subject: FREE HDTV Report
and Free Access to Insider Reports
From:
Des Chaskelson , Research Director, SCRI International
des_chas@scri.com
The following
report is available FREE to US TV Stations only who respond to SCRI's
new HDTV online survey at:
<<<
http://207.113.95.4/hdtv.nsf/survey >>>
On completion
of the survey, you will receive via email "The Millennium Report
- The Migration To Digital Television," an 80-page report compiled
by Larry Bloomfield, publisher of DTV Tech Notes and writer for
Broadcast Engineering Magazine. Results of the survey will
again be published in Broadcast Engineering Magazine.
In
addition, broadcast and pro video facilities (not manufacturers)
can earn 3 months free access to SCRI's online Insider Reports by
responding to the new Brand Awareness and Ratings Survey at: http://207.113.95.4/q7.nsf/survey
**********************************************
The Tech Notes
are published for broadcast professionals, and others, who are interested
in DTV, HDTV, Electronic Cinema, etc., by Larry Bloomfield and Jim
Mendrala. We can be reached by either e-mail or land lines (408)
778-3412, (661) 294-1049 or fax at (419) 710-1913 or (419) 793-8340.
(Please note Larry's new e-mail address). The Tech Notes are sent
(BCC) directly only to those who have asked to be on the mailing
list, however feel free to forward them, intact, to anyone who you
think might be interested. There is no charge for this Newsletter,
no one gets paid (sigh), there is no advertising and we do not indorse
any product or service(s). The ideas and opinions are those of the
individual authors. We still administer everything manually. We
don't use any "majordomo" automatic servers. News items,
comments, observations, opinions, etc. are encouraged and always
welcome. We publish when there is something to share. Material may
be edited for brevity, but usually not. Tech Note articles may be
reproduced in any form provided they are unaltered and credit is
given to both Tech Notes and the originating authors, when named.
If they are to be used by a publication that normally compensates
their writers, please contact us first.
END
