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Tech Notes

Published by: Larry Bloomfield & Jim Mendrala

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January 24, 2000

Our First Tech Note of the New Year

Tech Note – 049


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: 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:  and


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 you know too well from the debate over DVB and ATSC issues.

Regards and a profitable year ahead for us all.

Gerald -

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 -


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."


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


(Ed NoteLarry 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.

Subject: FREE HDTV Report and Free Access to Insider Reports

From: Des Chaskelson , Research Director, SCRI International

 The following report is available FREE to US TV Stations only who respond to SCRI's new HDTV online survey at:

 <<< >>>

 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:


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.