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Tech Notes

Published by: Larry Bloomfield & Jim Mendrala

(408) 778-3412 or (661) 294-1049

E-mail = or

August 30, 1999

Tech Note - 039


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.  The other stuff that used to be up here is now at the end of this newsletter.  We're growing.  We now have over 465 subscribers.

                                                          This is YOUR forum! 

                                   Past issues are available at: WWW.SCRI.COM


(Editor's NoteOur Tech Note #38 received the most reader response of any of our Tech Notes todate.  The following are representative of the e-mails we received.)


From: Ed Williams of PBS    >>> ewilliams@PBS.ORG <<<

About the Harris radio and TV Open House to be held at our new 165,000 square foot "Center of Excellence for Digital Technology" in Greater Cincinnati, Oct 1.  Ed said:  "It is quite a place. It opened on the same day the DTV Express arrived for it's decommissioning. It's quite a place. It's a huge place. The DTV Express Truck looked small in their "high bay" area. They could handle 6 at once in there. They also have a special area for operating several full size transmitters at the same time. The office area is also designed for serious expansion - which, I suppose what Harris has in mind.  Big place! Go see it. Find an excuse."  Cheers,  Ed Williams, PBS

For additional information and registration, call 800-622-0022


In response to our Subj: A couple of questions

We raided the possibility of a virus being introduced into a digital television system or set top box. One reader, who works at one of the major networks, said: "If the STB is only connected to a closed system such as the program originator or cable system, it should be fairly well protected from the outside world. Not immune from employee malice, but pretty well protected. If the STB is connected to the Web you could have protection similar to a corporate LAN firewall that could filter known viruses.

"Concerning the DTV plant, we are already so reliant on Windows and Macs that anything can happen. As your television becomes more like your computer, you have to treat it more like a computer. Now excuse me while I go do my daily backup on my STB."

Name withheld by request


Also in response to our Subj: A couple of questions

Martin Caniff commented: "Thanks for bringing up the problem with CBS's west coast feed to the satellite providers. I've noticed the same problem -- and couldn't figure out the right place to lodge my complaint."  Regards, Martin Caniff  >>> <<<


Comments from a well-respected San Francisco Bay area engineer

By:  Roy Trumbull

 The Dr. Yiyan Wu article is available from the ATSC site. I found it interesting that the actual signal level penalty vs. 8VSB is far worse that the predicted penalty. COFDM certainly has an advantage in areas of high multipath but it remains to be seen how it does in an apple-to-apples comparison (same power level and same bandwidth) on medium to far paths when the first Fresnel zone is partially or completely obstructed.

For DTV reception, the bowtie array antenna is worth considering. There are several ways to build it but it is essentially four stacked bowties against a screen reflector.  Quality is another matter. Some antennas are built out of very flimsy brittle materials. I'm trying to get a Lance bowtie array. Their antennas are heavy duty and you can buy galvanized versions.

The GI encoder is able to insert a watermark. As soon as I can get a file prepared by our art department, we'll have one on the air.

Roy Trumbull  >>> <<<


In response to the story, "What will it take," Dick Hobbs (DH) wrote us to which Jim Mendrala (JM) responds.  Mendrala's responses are in parenthesis after each of Hobbs' paragraphs.  

Mendrala says:  (Thank you for writing in with your comments. I have added my comments [in parenthesis] in answer to your concerns. Electronic cinema is still in it's infancy so many things will be looked at and redone if necessary.)

Hobbs said:  "Larry and Jim wrote a thought-provoking piece on electronic cinema, addressing the resolution issues. However, I am not quite convinced that it analyzed the whole story.

DH:  It is true that the resolution of film is much higher than any electronic medium yet developed. Most authorities suggest that 35mm is capable of what we for convenience call 4k resolution, i.e. there are about 4,096 pixel equivalents along a single horizontal line. Because all film is made in exactly the same way up until the moment when it is sliced and the perforations punched, 16mm has proportionally fewer pixels per line, 70mm proportionally more.

(JM: This is true. Film has a grain structure that is capable of resolving over 3,500 pixels. To scan that film and convert those random film grains to a digital image requires, like you say, 4,096 pixels in one horizontal line. Larger film formats will require a higher pixel count to equal the larger area of the larger film. By the same token, smaller film formats can get away with lesser pixels because the area of the film is less.)

DH:  But here is the interesting point. Although that is the theoretical figure, in practice both amateur consumer eyeballs and professional post-production systems are surprisingly tolerant of much lower resolutions. Although in the first flush of digital film excitement systems were built to 4k resolution they were almost never used, with most people happy at 2k resolution (2,048 pixels across a line of 35mm film, or barely more than HDTV). Astoundingly, the dinosaurs in Jurassic Park were largely created and composited at 1k resolution, i.e. lower than HDTV.

(JM:  There are many reasons for doing 2K (2,048) pixel scans. The main reason is cost and throughput. Cinesite in Hollywood offers digital mastering for CGI. They take the 35mm film and put it onto a "Spirit" telecine and do 2K scans. The film is sampled by four 480 pixel sensors for a total of 1,920 pixels per horizontal line. The color is sub sampled at half that. By doing 2K scans the throughput is around 4 frames per second at this time on a "Spirit" Other scanners that do 4K scans in use at the present take about 8 seconds per frame. That's about 30 times slower. Newer telecine machines are rumored to be closer to real
time but won't be available for at least a year or more. Then there is the problem of "pin registration". Film is exposed in the camera after it has been registered. In order to reduce compression pin registration has been shown to reduce the bit rate in MPEG systems up to as much as 20%.)

In "Star Wars - The Phantom Menace" straight film shots were reduced in resolution to match all the 2K EFX by also scanning them at 2K. Interestingly if you are more than three screen heights from the screen it is difficult to see the loss in resolution. No problem in the home where people generally sit that far back but a lot of theaters at three screen heights you are at the last row in the auditorium.

If you get to the theater late and all the best seats are taken you have to have the better resolution or you will be greatly disappointed.)

DH:  The recent demonstrations of electronic cinema have used either the Hughes light projector or the Texas Instruments DMD system. I cannot speak for the Hughes, but the highest resolution TI chips currently available have 1,280 pixels horizontally. Yet its projection quality was considered directly comparable to 35mm film.

(JM:  No, the quality from the TI and the Hughes-JVC is not that good. What is considered directly comparable on the TI projector is the color rendition and light output is comparable to 35mm film through a standard projector i.e. 16 ft. Lamberts. Color because it is RGB additive has a wider color gamut capability then the film with white light.)

DH:  My view is that, for purists, clearly there is much to be done. But we should all be aware that there is a pragmatic view, which is that we probably have enough resolution now. The advantage of digital projection - a consistent quality, not related to how many times a print has been shown and how badly it has been handled - is worth achieving in itself.

(JM:  We have enough resolution to start making money on it, yes. But the other advantages are a real plus for the theater-goer.  Resolution will improve as projector technology improves. TI is holding at 1280 x 1024. That is a computer standard and has an aspect ratio of 1.25:1 which necessitates the need for special non-standard transfers and different anamorphic lenses for the different aspect ratios.)

DH:  But I've only been talking about two dimensions of resolution. It is depth that is the real problem: how do we store and move enough bits to get a 1,000:1 contrast ratio?

(JM:  1,000:1 can be handled with 10 bits. 10 bits per color channel is equal to 1,024 levels of gray or a wee bit more than 1,000:1.)

Dick Hobbs >>> <<<


Subj:  New Digital Receiver Technology from Motorola Enhances 8-VSB Reception, Solves Multipath Problems

By      Frank Eory, Designer, Digital Television Operations, Motorola

A new digital receiver technology from Motorola solves a potentially serious reception problem in digital and high-definition television (DTV/HDTV) broadcasts that use the Advanced Television Systems Committee (ATSC) transmission.

Broadcasters expressed concern recently when third-party test results showed that multipath reflections interfered with DTV reception. Addressing this issue, Motorola, in collaboration with Sarong Corporation, created a new digital signal processing architecture and its first implementation in the

MCT2100 demodulator and forward error correction (FEC) chip.  The chip uses proprietary algorithms and unique equalization architecture, providing optimal signal reception even for the most extreme static and dynamic multipath signal ensembles.

Motorola expects that the new technology will make the broadcasting industry's efforts towards ATSC a reality. Motorola combined its 0.18-micron CMOStechnology with state-of-the-art signal processing algorithms to provide a proven, low-cost solution.

Early implementations of 8-VSB (vestigial side band) HDTV transmissions showed problems in dynamic multipath and long-delay static multipath reception. Motorola's new technology, MCT2100, compensates for a broad range of dynamic echo ensembles with echo amplitudes approaching the level of the desired signal. In static multipath with long delays, the MCT2100 corrects ghosts with up to 41 microseconds of delay. It achieves this bys incorporating a full equalizer design, which avoids the sparse equalizer techniques that compromise performance.

Glenn Reitmeier, Vice President for DTV and Web Media at Sarnoff, said the new chip means that all of the capabilities of the ATSC standard will be available to TV set makers and their customers, the viewers. "The MCT2100 is a major step forward in implementing the perfect pictures and reliable data transmissions that the creators of the ATSC standard intended for DTV and HDTV."

The MCT2100 is a member of Motorola's M-DTV(tm) chip set.

(Ed Note:  We did not get an e-mail address for Motorola's Mr. Eory.  We will be more than happy to pass on any inquiries through Motorola's PR firm who arranged for this article.)


Subj:  A Two Bit Stereo?  

By:    Larry Bloomfield

The connotation of a two bit anything is not something most would relish, but when it applies to digital products, the fewer bits to do the same job is usually better.  If two bits are good, then one bit should even be better.  Such is the case with core amplification technology developed by Sharp utilizing 7th order Delta-Sigma modulation with noise shaping and an incredibly high speed switching circuit.  In theory, reproduction, under the most ideal of circumstances, is usually only at half the sample rate.  For example, if the sample rate is 1000 cycles, the absolute best one could hope for would be 500 cycles, and even that is wishful thinking.  As the sample rate increases, expectations for better quality reproduction improve.  The Sharp 1 bit amplifier circuit samples at a rate of 2.8224 MHz, allowing for sound reproduction incredibly close to the original signal, with plenty of room left over.

As we address the wonderful world of digital television, we sometimes tend to forget that there is sound with our pictures and with AC-3 breathing down our necks, we have 5.1 times as much to deal with as with old fashion monaural.  Keeping track of bits, audio or anything else, begins to be important in the over all scheme of judicious bandwidth management. 

There are some rather interesting benefits that come with this one bit amplifier.  Things like frequency response of 5 Hz to 100 kHz, transient response of 2.8224 MHz, and a dynamic range that approaches 110 dB in the audible range.  Power consumption is also a concern and the one bitter requires about half that of traditional analog amplifiers.  This reduces heat dissipation to about 20% of it's analog cousin and all this requiring about 1/4 as much space and better use of the building's air conditioning system.   What makes this amplifier worth considering is it rated power output of 100 watts plus 100 watts at 8 ohms.

The intellectual properties associated with the 1-bit amplifier are covered by no less that 58 patents filed by Sharp, including 12 that relate to Analog/Digital conversion and DS (Delta-Sigma) modulation. To this add 14 additional patents that relate to applied audio technical conversion and 22 that relate to playback and decoding technology.  With that much invested in that many patents it is obvious that Sharp plans to utilize this technology to its' fullest.  No mention was made by Sharp to license this technology to other manufacturers, but don't be surprised if they do.

One more note.  Sharp has announced a CD that will hold 40 two-hour movies.  That's 80 hours on one disk.  Stay tuned. 

For more information, visit the Sharp web site at:


Question:  Does anyone know about the September 9, 1999 as being any special with computers?  We've been told that 9999 is a code that is commonly used in computers to shut programs down.  Your input is most appredciated.


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.     


The Tech Notes are published for broadcast professionals, and others, who are interested in Electronic Cinema, DTV, 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 (661) 294-0705. 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.