Published by: Larry Bloomfield & Jim Mendrala
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November 19, 2000
Tech Note – 066


Sharing experiences, knowledge, observations or anything relating to Digital Television, Digital Cinema, etc. with fellow engineers and readers is our purpose. Our mission statement, other relative information and this current issue of the Tech-Notes is now posted on our website.  You can also find all our past issues there as well. We’ve had over 2800 visitors since July 1st, 2000. Thanks.  We are growing.  We now have over 860 subscribers. Thanks to our regulars and welcome to the new folks.  This is YOUR forum! 


Subj: Reader Responses
From: Michael Karagosian

RE: Tech-Note #65 
Broadcast Engineering editorial: DVB-T/COFDM - Ralph L. Cerbone 

I have no reason to disbelieve what Cerbone says.  When things go bad, everyone likes to blame it on scandal.  If the process that Cerbone describes is true, then isn't it also flawed?  What I hear him saying is that VSB was the best of the lot tested.  If this was the best, then wouldn't it have been worth waiting for something better?  My sense is that there was a political push to approve something in a certain time frame, along with a poor understanding of the negative impact that an immature decision could create.
There is an assumption by many that more technology can fix technological problems.  If only this were true.

While the scope of impact is much smaller, let's hope that standards for digital cinema hold out for high goals, and not bend to political push.

Best regards,
Michael Karagosian

More Reader Responses

Subj: The Cost of COFDM
From: Roy Trumbull (Assistant Chief Engineer, KRON-TV, San Francisco, CA)

Be sure to read Expert’s Corner (page 26) in the Oct 2000 issue of Broadcast Engineering. In it, Geoff Mendenhall of Harris is asked about converting to COFDM with the same coverage provided by 8VSB. I’ll summarize some of the points in this table:

                                    8VSB     COFDM
Xmitter Power Av            50KW     200KW
Annual Power Cost        $175K       $586K
Co-channel Interference 
Protection required           as is     +4.8 dB

The FCC would have to rework the allotment table to permit the higher COFDM power. As there is already DTV to DTV interference built-in to the table and DTV to ATV interference as well, it is unlikely that the additional power would be granted for COFDM.

That leaves two possibilities. One is that a DTV station, operating with COFDM, and using the average power permitted for 8VSB, would cover only a 30 mile radius and not replicate the NTSC coverage of its parent station. The second is that the European model would have to be adopted with every population center requiring its own low power repeater. 

I think the cost of the repeater equipment would be nothing compared to the site development costs. Imagine the legal fees to overcome the “not in my backyard” factor. As one goes further out, there is also the domino effect of site B failing so Site C no longer has an input signal.



Subject: Getting Signals into your TV Set

A more elegant solution is now available for designers seeking low voltage and VHF/UHF booster/splitter functions thanks to two new modulator ICs introduced by Motorola Inc. The MC44BC373 and MC44BC374 -- that integrate the antenna Booster/Splitter functions with the traditional VHF/UHF Multi-Channel Modulator function, combine all sound subcarrier and VHF/UHF VCOS (Voltage Controlled Oscillators) on a single chip. This DigitalDNA(TM) solution will assist Motorola's customers in shortening design-time on television-related applications.

These chips allow for lower power consumption and are designed for applications that range from videocassette recorders (VCR), analog and digital set-top-boxes (STB) for satellite, terrestrial or cable television, to DVD players and video games.

"With these devices, there is no longer a need for external varactor diodes or coils. In addition, they solve the sensitivity problems related to bonding wire and PCB stray capacitances and inductances," states Don Bosco Grant, video front-end operations manager of Motorola's Entertainment Division's Center of Excellence for High Frequency TV Tuner products. "Potential customers no longer require the High Frequency skills that were once necessary for this type of system implementation. Now, all this functionality is encapsulated in a single chip."

The very small number of external components required makes it possible to implement a complete modulator module on the main VCR or STB chassis, or to dramatically reduce tuner module size. Design of the module is greatly simplified, as well as the manufacturing flow since the remaining external components do not require any alignment, adjustment or matching.

The use of the BiCMOS(TM) technology in these ICs not only provides excellent RF performance but also reduces the power consumption by a factor of two for both the Modulator and Antenna Splitter sections. In addition, it eliminates the need for a 33V
supply since everything functions from 5V.

There are two versions of the ICs: A multistandard version (PAL/NTSC/SECAM) and a PAL/NTSC version. Both devices are offered in the space-saving TSSOP24 package.
A complete development kit with a populated application board, 10 samples, software, connectors, PC interface and user manual is available.

The modulator section is extremely versatile and fully controlled by a high speed I(2)C compatible bus, offering several test modes for easier production. In the multistandard version, it corresponds to all worldwide standards by operating on channels 21 to 69 in the PAL, NTSC and SECAM standards, while the sound subcarrier is selectable to 4.5,
5.5, 6.0 and 6.5 MHz, plus the ability to function in the VHF range by selectable internal divider ratios.

The antenna booster and splitter section operates from 40 to 860 MHz and provides exceptional gain flatness and isolation performance.  The inputs from the antenna and the modulator section are added internally to feed the TV output.

For more information: 


Subj:  SCSI vs. USB 2.0 – Is SCSI dead?
From: Sarah Jane Watson

After a recent conversation about whether or not SCSI is "dead/dying" in light of the introduction of USB 2.0, I did a little research to make sure that I had my facts straight.

Basically, SCSI is nowhere near "dead" and is the first choice for any serious usage.  SCSI maintains data transmission speed no matter how many peripherals are attached while each additional peripheral attached to USB 2.0 dramatically decreases its transmission speed.  Furthermore, dependant upon the peripheral, USB 2.0 almost never performs at 480 Mbs (please see portion of article inserted below).

Ultra160 SCSI is ideally suited for high traffic environments that can benefit from its added speed, management or both. Digital video environments, one of the most throughputs intensive, were one of the earliest to adopt Ultra160 SCSI. Multi-node server clusters were another early adopter. When a server fails, it can bring I/O to a crawl. With twice the throughput of Ultra2 SCSI, Ultra160 SCSI host adapters have the bandwidth to handle the additional loads until a failed device is replaced. 

In large disk farms the added speed of Ultra160 SCSI is an obvious plus. As databases expand into the terabyte range, information access requires more time. Ultra160 SCSI provides an easy-to-implement solution that can cut data transfer times in half. Moreover, its ability to negotiate transfer rates and guarantees connection during hot pluggable drive replacements can help maintain a higher level of drive availability -- even under less than ideal circumstances. Ultra160 SCSI is attractive to Internet service providers, corporate intranets, data mining and data warehousing operations. 

SCSI is the only high-performance interface that allows devices operating at different speeds to be connected on a single chain, and the only I/O solution that offers a method for connecting both internal and external devices. The Adaptec Ultra160 SCSI card family provides one bus segment for legacy SCSI devices and another bus segment for Ultra160 and Ultra2 SCSI devices by using Adaptec's exclusive SpeedFlex technology. 

SpeedFlex technology ensures maximum performance while maintaining full backward compatibility with legacy equipment. It does so by creating two electronically isolated SCSI bus segments for the host adapter--one for single-ended devices and one for Low Voltage Differential (LVD) devices. LVD is a standard which combines the cost-reducing features of older single-ended (SE) technology with resistance to signal noise and ground shifts traditionally offered by High Voltage Differential (HVD) design. Without SpeedFlex technology, directly attaching any legacy single-ended SCSI device to an LVD bus would degrade the performance of the bus and, therefore, all attached LVD devices. 

I have included an article by David Every, which I found posted on, entitled "USB 2.0: Yesterday's Technology Today."  I believe it further explains the situation. 

“Problems with the design

“By jumping speeds so dramatically, Intel is creating "issues". The old high-speed mode of USB (1.1) was 12 megabits per second, and the low-speed mode was 1.5 megabits per second.  When the low speed mode's data (packet) is being sent, then you can't be sending the high-speed data (packets). If you have a mix of both devices, the slower speed devices reduce the performance of the bus -- so even in USB 1.1 the bus isn't really able to transmit 12 megabits per second if you are using any low speed devices at the same time. However, the difference between 1.5 and 12 isn't that big a deal for most users -- and in low speed devices you really don't care about a small loss of performance, it is still "fast enough". With USB 2.0 the issues become much bigger. High speed devices are a completely different market -- when working with video or high end sound and so on, you care about speed (a lot) -- and glitches in performance really matter!

In USB 2.0 there is a new high speed mode (480 megabit per second), the older high-speed mode (12 megabits per second) and the old low-speed mode (1.5 megabits per second) -- this is HUGE difference in speed (320:1). What this means is that there will be a lot of potential bandwidth wasted -- or things will never come close to their claimed performance. Think of the following:

If you are using 3 devices, a keyboard (or mouse), a printer, and a new USB 2.0 video camera then you could divide your potential performance as seen above. 1/3 the performance would be used up at the lowest speed, and 1/3 at the middle speed, and what is left goes to the highest speed mode -- this means your theoretical 480 Mbps bus (data pipe) might really only achieve about 149 Mbps in our sample usage. In the little diagram above, all the red area is wasted potential (about 330.75 Mbps worth). Imagine how much worse it gets if you have many more slow speed or USB 1 devices (like a keyboard, mouse, joystick, printer, scanner, disk drive, etc.) and only one high speed USB 2.0 device.

Now it isn't quite as clear as the diagram since there is a way for one device to steal as much time as it needs which only allows the others the leftover time (called isochronous mode). However that has tradeoffs too -- it means that the isochronous device (video) will go faster, but at the expense of the other devices -- the printer and keyboard run even slower to make up. Even then USB just can't live up to the promise of 480 Mbps in the real world -- so 480 Mbps in Intel's USB lingo is not the same as 480 Mbps to anyone else.

I hope this fully explains the benefits of SCSI and their continued value in the marketplace. 

Best regards,

Sarah Jane Watson


Subj: Infected video
By: Larry Bloomfield 

With the plethora of viruses computer users encounter on an almost daily basis, I can't help but wonder if there is any way someone could corrupt streaming video or digital television?  I was thinking about viruses and hackers possibly screwing with streaming video or DTV, so I contacted Microsoft’s Tom McMahon and presented the question. 

McMahon said:  “Messing with the basic A/V streams seems pretty remote unless “they” did something with the server prior to air.  But at most I would see that only resulting in a black screen or maybe just messed up pictures.” 
I asked if there were any other areas of the television path, which should be considered a possible weak link or security risk?  To this, McMahon responded:  “More unsettling is the possibility that someone would broadcast a virus (or more accurately, perhaps an app-bomb) application to intelligent set top boxes such as ATSC's DASE receiver platforms.”

It is not my intention to generate any interest in a derogatory light, but rather, as the saying goes, forewarned is forearmed.  Got anything to add to this?



Subject: COFDM vs. 8VSB
By: Jim Mendrala

Nat S. Ostroff, Vice President, New Technology, Sinclair Broadcast Group presented the program at the Society of Television Engineers meeting on November 16, 2000. With an intro from David Smith, CEO, Sinclair Broadcast Group, and some comments by Mark Hyman, VP of Government Affairs, Sinclair Broadcast Group.

Mr. Ostroff gave a short history of the COFDM vs. 8VSB debate. He discussed the advantages and disadvantages of both systems and presented some of the actual field results of the testing done in Philadelphia, PA, Baltimore, MD, New York, NY and Raleigh, NC. He also did a comparison with NTSC reception on fixed antennas, bowtie antennas and a whip antenna. 

A comparison of the two different types of digital transmission was presented with a view as to the effects of choosing one over the other, as applied to a TV station’s digital wireless business.

Mr. Ostroff, when asked about HDTV signals, said that at the NAB 2000 they not only transmitted SDTV from a transmitter 17 miles from the Las Vegas Convention Center but also HDTV at 19.3 Mb/s. Pictures were being received not only with a fixed antenna mounted on the roof but also with a whip antenna on the convention floor. Another advantage of COFDM was that you do not need to change frequency when going through a repeater. A simple distribution amp can be used to amplify the signal inside of difficult buildings or sites.

As far as the digital picture is concerned, there isn’t any difference in either system. But as far as flexibility, scalability and ease of use, the COFDM system has a lot going for it. Mr. Ostroff pointed out that the traditional C/N method of coverage does not tell the whole story of DTV reception. Multipath is a killer for 8VSB and is a big trouble when closer in to the transmitter. A lot of DTV receivers would display the “Blue Screen of Death” even though there was a strong signal but the receiver was unable to decipher the payload due to multipath. COFDM on the other hand seems to thrives on multipath. Modification of the transmitter to COFDM is relatively cheap and simple to do in most cases, as he pointed out. Transmission line matching and SWR are not as critical. 

A directional bow tie antenna in the COFDM system can be rotated in a strong signal area up to 270 degrees and still receive beautiful pictures. With 8VSB, a Yagi with up to 26 elements needed and had to be pointed very carefully to receive a picture. In the long run, the difference between COFDM and 8VSB was about a two-mile difference at the RF horizon. 

Mr. Ostroff said that presently there is a small low power COFDM station operating on Long Island and reception in the canyons of New York City is quite robust, and reception with a whip antenna in a moving vehicle was fine.

Mr. David Smith presented a case for the allowing of both systems to be authorized in the US with the market place ultimately deciding which method will survive.

Mr. Smith’s concern was that most TV engineers are doing nothing to let their elected officials know what is happening. Many do not want to “rock the boat” for fear of losing their jobs and seem to be refraining from informing management of the situation. He pointed out that cable, Internet and other content distribution systems do not need an FCC license to operate.  He said that Zenith, which was formerly an American Company that went bankrupt and is know owned by a Korean company, and the new Zenith owners as well as DirecTV are lobbying for 8VSB only, while the rest of the world has or are about to settled on COFDM. DirecTV, he said, was lobbying for 8VSB so as to increase its signups for satellite reception. At the rate it is going, if the US sticks to 8VSB, only we (along with Korea) will end up becoming an island in the sea of nations who have all gone COFDM. 

Mr. Smith was not suggesting abandoning 8VSB but allowing co-existence of 8VSB with COFDM. When the marketplace determines that there no longer is a need for 8VSB, then it could be dropped. Mr. Smith also stated that presently there are about 50,000 8VSB DTV receivers in the US. He sees no reason to worry about the legacy issues because if the broadcasters would pay those owners of 8VSB receivers $1,000, they could apply that to the purchase of a new COFDM receiver. That amount of money would be very small for what is at stake. In England, Mr. Smith said the sale of COFDM receivers has already passed the 1,000,000 mark and is climbing rapidly since its introduction.

Mr. Smith, Nat Ostroff and Mark Hyman all voiced their concerns that if we don’t speak up now through our congressmen and senators, then Free TV as we know it will disappear for lack of viewers. NTSC will go away!

After the meeting, Mark Hyman joined Mr. Ostroff and Mr. Smith in answered many of the interesting questions the broadcasters of Southern California had.



Subject: Digital Cinema vs. HDTV – an Editorial look at Digital Cinema
By: Jim Mendrala

Like the Presidential Election that took place on November 7th, we don’t yet know what Digital Cinema will be like in the near future. Let me try to put Digital Cinema into some sort of perspective.

The MPA (Motion Picture Association) is made up of several major “film” studios. These “film” studios make their bread and butter on DVDs and VHS tapes as well as television episodes. Major television equipment manufacturers and/or service providers own some of these film studios. Movies only get a short play in theatres and, even though they report what seems to be large box office receipts, these monies are small in comparison to the monies made on DVDs, VHS tapes and episodic television programs.

In the 1950s and 60s, the major movie studios were afraid that television would take over and they would lose their movie-going audiences. So they tried improving the movie experience with CinemaScope, Todd-AO, VistaVision, etc. Even a few years ago, the CoSharp printer was invented to allow 65 mm camera negatives to be economically printed on 35 mm intermediate film stock for a much-improved image on the screen. 

These various attempts failed in the economic sense that films are still being delivered in the 35 mm standard format. The studios know what the economics are and no special equipment is needed to project a movie onto the screen. It is also true that many theatres are not even up to SMPTE standards and quite a few don’t even have surround sound with 5.1 channels.

The theatres are hurting in keeping their doors open. Sales from the concession stand are about the only major source of revenue for the theatre. It is known that up to about 90% of every dollar collected in the box office goes back to Hollywood. Theatres, in order to make going to the movies an experience, have tried various methods to bring in the public. Stadium seating is one of them. Unfortunately from a technical standpoint many theatres leave a lot to be desired. Yes, stadium seating in most cases allow the person in front of you to be lower so as to not interfere with your view of the movie.  However, the distance to the screen has been reduced so that in a lot of cases the ideal seat is in the rear row below the projection port. 

At the present time, HDTV has not taken off like it should have. There are various reasons for the delay, which relate to the broadcasters, cable companies and satellite companies. Even the networks have slowed the implementation of HDTV. 

What effect will this have on the movie studios? Basically this. Hollywood is now transferring the majority of their productions to HDTV tape. High definition DVDs will become available within a year or two. This will increase the sales of “Home Theater” systems. The viewer will be able to go out and buy HD-DVDs with 5.1 or more channels of sound and will be able to watch these movies in the privacy of his own home on screens up to 8 - 10ft wide.

From the movie studios viewpoint, to make these HD-DVDs it will still cost less than $1 to produce but will sell for a bigger profit than a movie theatre will ever collect from its patrons in its limited couple of weeks runs. 

Digital Cinema so far to date has been for the most part HDTV recorded on to a D-5 then compressed using a QuVis wavelet box and then transferred on CD-R discs for shipping to and loading into the theatres. These movies have been shown on Texas Instruments “Digital Cinema DLP Projector” with a resolution of 1280 x 1024. HDTV 1080p has 1920x1080 resolution, so the displayed image isn’t even as good as the source. Resolution is only one of the criteria. Since he color of digital cinema is stunning, it almost achieves the color gamut of film. Standards for HDTV are established and the equipment is readily available “Off-the-Shelf”. It seems that most of the studios are saying that this is good enough. It appears that the main idea is to sell DVDs and VHS tapes because that’s where the money is. The movie is only a means of promoting the DVD or VHF tape sales.

NATO (National Alliance of Theatre Owners) seems to be more concerned with economic issues like “who’s going to pay for the new digital cinema system?” Disney so far has had over 30 theatres equipped with TI projectors and QuVis boxes and would like to have a few hundred by the end of next year. TI as you all know has made deals with several projector manufacturers to build the DLP Cinema Projector. TI knows that to promote the DLP logo on a theatre marquee makes good business sense since the sales of DLP HDTV sets in the millions are seen in the not to distant future. It won’t matter that the broadcaster might not be transmitting HDTV, because other services will be able to provide the HDTV pictures to the home on a pay-for-view basis.

Pay-for-view on the cable or satellite is already happening. It is only a matter of time till the broadcaster attempts to try this, although the FCC probably will not let that happen. If the broadcasters manage to survive in the future with an acceptable digital system with HDTV as a regular offering, then digital cinema will be a total home entertainment experience. But we all know that you cannot get the movie experience on a small screen. Take for example the Warner Bros. movie “Dancing with Wolves”. On regular small screen TV, it is a movie that is not very impressive, but the same movie in high definition with 5.1 channels of sound is a movie that is impressive and is remembered. Alfred Hitchcock’s “North by Northwest”, which was shot in Paramount’s VistaVision, is another example of the big wide screen experience.

Some of us in Hollywood still clinging to the idea that digital cinema should be better than what the moviegoer now gets. We have the technology that can make this happen, but the movie studios don’t appear to see any good reason to invest in this new, future technology when HDTV is already here. It is sad to say, but some people seem to think SDTV on a DVD is high definition. Others looking at a projected digital cinema movie seem to feel that 1280x1024 is more than enough resolution, even though a typical release print has about 55-lp/mm, and the digital cinema projection at 1280x1024 only has an equivalent 22-lp/mm resolution. Answer prints that the Producer and Director view in the film lab screening rooms typically are capable of showing in excess of 80-lp/mm resolution. A digital cinema system to do this would have to have a minimum of at least 4000x2000 pixels.

A lot of ideas are being discussed in the digital cinema DC28 SMPTE committees, but all these ideas will take time to work out and set some standards. Some of the studios don’t seem to want to wait, as HDTV can bring them instant revenues.

In conclusion, it appears that HDTV will become the defacto standard for digital cinema. This will set true digital cinema back many years. HDTV will be the short term “Flash –in-the-Pan” until a true digital cinema system evolves.

At the present time the studios control, through their distributors, what a neighborhood theatre can show. If HDTV does become the defacto standard, then the independent filmmaker will have a better chance of getting his/her film seen. A lot of the short subjects can be easily put on DVDs and/or distributed on the internet.

For the student who wants to become a “film” maker, major film schools are now using HDTV equipment to teach the art of filmmaking. The idea is typically shot in 1080/24p, edited on an Avid system, then either transferred to film for distribution to theaters around the world or distributed over the internet. A few of the well-known directors still evaluate their efforts on the big theatrical screen, but many film directors today evaluate their work on a 14 or 27 inch monitor connected to an Avid system. They are evaluating their work on a small, not big, screens. The art of shooting for the big screen is, sad to say, becoming lost. If the theaters go away for various reasons, then cinema as we know it will disappear.

Digital cinema, as some of us envision, will come to pass, but the road ahead has a fork in it, and, unfortunately, the studios will probably take the path of least resistance and go the HDTV route. 


Parting shots
By:  Larry Bloomfield

It’s that time of the year, again and one cannot help but wonder what the New Year and new administration will bring.  In light of current vote tallying, it sure is refreshing to know that everyone else’s crystal ball isn’t any better than mine. 

It is interesting to note that three of the five FCC commissioners terms, including the Chairman’s, will be up during the next year or so and our new president will have the opportunity to select someone new or to continue the incumbent in his or her office.  There is no question that things are on the move and will change.  Anyone hazard to guess in which direction? 

One thing’s for sure and that is Congress has latched onto the idea of getting as much blood (money) out of the broadcasters, and future users of the current broadcast spectrum, as they possibly can.  Congress sees the spectrum as a bottomless money pit with which they can spend, spend, spend and still balance the infernal budget.

It certainly wouldn’t hurt for broadcasters to wake up to the new world of digital. If you look at the numbers, not even 10% have made the move and the clock is ticking. With 2002 just around the corner, the use it or loose it concept is becoming more of a reality than any of us would care to know.

If you take a good look at the way things are going, technologically, there’s more than one way to get a sponsor’s message into the homes of the American public.  Let’s face it; that’s where it’s all at with our commercial television system. The seeming move to “wireless” this and ‘”Wireless” that is defiantly a catalyst and with every entrepreneur, and their brother, coming up with new and different ways of using the spectrum, the battle lines have formed and are becoming more clearly defined with every passing day. 

There are a few factors in this whole equation that could easily displace the terrestrial broadcasters right off the air, as we currently perceive them. First, if cable ever gets their act together and can deliver a pristine quality picture and, perhaps offer a bit of high definition programming, through a set top box that conforms to a national standard, we got one healthy competitor. 

Secondly, as the direct-to-home purveyors offer would-be viewers even more local-into-local, all the broadcaster needs is a feed to either the cable head-ends or to the up-linkers address and they could do away with the cost of the transmitter and the high monthly power bill to run it. 

The third delivery method, which has been crappy in the past, is rapidly improving and will, in the not too distant future, be equal to anything else in the market place and that’s the Internet with is streaming video, webcasting or what ever else you wish to call it.

With these alternatives staring us in the face and the promise that everything MUST change, it isn’t difficult so envision the fact that if we don’t move to preserve our heritage of free, over-the-air television, we’re going to see it diminish into something that none of us will recognize.  When? Who knows?  But those are my observations. 

Have a Happy Thanksgiving.  I’ll be enjoying it in Florida, visiting my son and his family (three grandkids), where I understand they put tail feathers on an alligator and coax them into saying gobble-gobble.  Go figure……………………… 

The Tech-Notes are published by Larry Bloomfield and Jim Mendrala. We can be reached by either e-mail (above) or land lines (408) 778-3412, (661) 294-1049 or fax at (419) 710-1913 or (419) 793-8340. The opinions expressed herein are those of the individual authors and do not necessarily reflect the opinions or positions of their friends, employers or associates.  If you wish to remove yourself from this list, send an E-mail to:  In the subject area put the word Remove

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