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 Some of the information may be out of date.
**********************************************DTV Tech Notes
DTV Tech Notes #11
% Larry Bloomfield & Jim Mendrala
(541) 385-9115 or (805) 294-1049
E-mail = larrybend@aol.com
J_Mendrala@compuserve.com
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November 25, 1997
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Sharing your experiences, knowledge or anything else relating to DTV,
HDTV etc. with your fellow engineers is what we are all about. We've seen the need for our fellow engineers to have a "not so formal" media to express them selves. We will not pass on anything that cannot be verified or the source cannot be identified. If we inadvertently pass on erroneous information, we will make every effort to get it corrected as soon as possible. The above disclaimer is for obvious reasons.
Who will we send these issues to? Anyone interested!. All we ask is for interested person to e-mail us their request to be added to the mailing list and it's done! Feel free to forward this on to your associates, but let them know that you've done so and it's not directly from us. If we've sent this to you and you're not interested, just let us know and we will take you off the mailing list.
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Subj: H/P Test Equipment
From: LARCANTX (Dave Hill)
In the November 6, 1997 issue of TV Technology there is an article on page 16 detailing the new Hewlett-Packard 89441V VSB/QAM Signal Analyzer used for testing the ATSC's 8-VSB DTV transmission mode. If you would like additional information on this unit you may call H/P at 800+452-4844 and ask them to FAX or send you the Technical Data (16 pages). Had tried to have them send it to me as an e-mail attachment but they are not (presently) set up to do this. Good Luck as we charge gently ahead with DTV.
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Subj: Education on wheels
From: Larry Bloomfield
Several issues back, we ran a piece about the DTV Express. Not much was said at that time, but since I was in the Washington, DC area recently, I spoke to the folks at the Harris offices to check out the progress of the DTV Express and found them to be moving right along to the point they are staffing the mobile part of the operation. For those who don't know what the DTV Express is, I'll try to explain. The Public Broadcast Service (PBS) has joined ranks with the Harris Corp. (or visa versa) to put together a traveling, teaching, demonstration - road show of how DTV should be or can be done. The "thinking" on this is that it is easier for technical and non-technical managers to understand what is needed and expected of them (by the FCC. et al) if they can see, touch, smell, etc. a real live High Definition DTV set up and have someone who knows what's up, explain it all to them in language they can understand.
As I understand the distribution of responsibilities, it goes like this: PBS is responsible for the teaching and road show scheduling and Harris will get various manufacturers to loan them equipment to be installed in a very long trailer (like on an 18 wheeler) with 15 foot pull outs on either side. The real estate of the trailer is divided into three sections. One end will be dedicated to equipment racks loaded with all the "on-loan" equipment and paraphernalia require to put on a DTV program from any of several programming sources. In the center will be a working control room and the other end will be a classroom/presentation area.
The mobile unit is being put together in Alexandria, Virginia and will be moved to Harris's home offices for outfitting with both Harris equipment and the "on loan" gear. Harris/PBS is targeting NAB in Las Vegas in Spring '98 to have everything ready for the DTV Expresses' first public appearance. After NAB, the road show follows. It is a rigorous schedule covering 18 plus months. Plans are to visit the top 40 markets where personal attention can be given to anyone who will ante up a small stipend (I think I heard $200 per person) for the information they have to impart. I also understand that Harris/PBS plans to up date - up grade the DTV Express as improvements come out and the various supporting manufacturers get the newer "on loan" equipment to them. Keeping things on the cutting edge!
I believe this is a golden opportunity for our industry to belly up to the learning tree and drink their fill of the information PBS and Harris
has to offer. So many times innovations and or technology have come out and there are no ears to hear or minds to grasp and no one who can explain it if there are. With the briefness of the schedule facing all television broadcasters to make "the transition," DTV Express is a timely project. I'm surprised there aren't more of this kind of thing. Keep an eye out for them at both NAB and when they visit your neighborhood. You'll hear more about this as we get information.
In conclusion, I'd like to share an idea here that I shared with Harris when I was there in Alexandria: Someone should put together several of these "trucks," less the classroom area. These "trucks" can be rented to prospective buyers of digital TV equipment so they can make the cutover to digital cleanly. This would give the station the luxury of cleaning out their old analog equipment and install their new gear without any major conflicts. Of course an instructor should go along with this truck to teach the fundamentals of DTV to the operations and maintenance staffs of the various stations who rent the truck. Eventually the "trucks" could be sold for any residual value when things spin down. Seems like a win-win situation to me. When you see this happen, just remember where it is you first saw it......... here. These are my views. Lets hear yours.
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Subj: Larcan Meeting
From: Peter Finch (Norcom) 503/632-7488
I was fortunate enough to attend a meeting at Larcan where Mr. Dennis Wallace made a presentation about DTV and its affect on translators and LPTV. Dennis is part of the "Grand Alliance". Nothing here is guaranteed, merely relayed! These are bullet statements that I got from the meeting:
Much of the existing equipment will be able to be upgraded from NTSC to DTV. The system will require good linearity. A 1-KW
NTSC unit will make a good 200 watt DTV unit. The 200 watt DTV system should give better coverage than the 1-KW NTSC
system.
Transmitter upgrades will include : Replace modulator $20K High stability LO $1K Power metering/AGC $1.5K
Translator upgrades will include: Up and down LO's Power metering/AGC Add filtering to IF Total cost $7.5K
Some of the channel allocations have adjacent channels in the same market. This should work as long as the transmitters are co-located (or at least within one mile of each other). This will not work for larger separations due to mask overlap/power differences.
No test equipment is presently available except a vector signal analyzer from HP costing about $90K.
The DTV threshold is a S/N ratio of about 15 dB. At 14.5 dB, it's gone. This compares to an NTSC system where a S/N ratio of 30 dB gives an almost unusable performance. Decoders take about 1/2 second to lock on again if the bit stream is lost for more than a second. This may cause a "pop" in the audio or a box to appear in the picture. Losing the incoming bits for 10 seconds will cause a 1/2 second loss of video/audio. This will be a problem for "channel surfers".
The phase out of NTSC in 2006 is unrealistic. Dennis sees a date of 2015 to 2020 as more likely.
Bit error rate is not the real problem. Packet error rate is the issue. 2.5 uncorrectable bits per second is the problem threshold.
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Subj: The bits & pieces of HDTV & DTV as it evolved in the US.
From: Larry Bloomfield
I haven't given a book report since my school days, but I found "Defining Vision: - The Battle for the Future of Television" How cunning, conceit and creative genius collided in the race to invent digital, high-definition TV ($27.00 US - Hard Cover) by Joel Brinkley, to be a book I couldn't put down. .....but then my tastes in reading material are different then most. For those of us who are destined to living through the implementation of both High Definition and Digital Television, will find this book most interesting. I got snookered into reading it because several friends, from different parts of the world, both technical and non-technical, suggest it to me due to my involvement in these DTV Technotes and my interest in the historical trivia which goes with our business.
Brinkley puts together, in his book, the saga of the Land-Mobile lobby wanting the unused parts of the television spectrum. How that generated a "keep our spectrum at all costs" syndrome at the NAB and else where in our industry. He shows how "industry" here in the U.S. went about reinventing High Definition TV (the Japanese had it for nearly ten years) and how Digital TV was considered a "near impossibility." Brinkley skillfully told the story of a Korean gentlemen, not long out of college, who didn't know Digital TV was a "near impossibility", brought it into fruition in a small engineering branch of General Instruments Company down in, out of the way San Diego,
CA to the suprise of the big guys back in the Ivy League. He describes how foundering companies joined forces to keep from going into receivership and finally how those who survived got together to form the "Grand Alliance." The 390+ pages are filled with easy to read information many of us are familiar with as bits and pieces. Brinkley weaves this HDTV- DTV novella into an informative, yet enjoyable reading experience. It's worth the bucks to read his perspective.
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Subj: DTV News
From: LARCANTX Dave Hill - LDL COMMUNICATIONS, INC.
650+347-9700
The following information was passed on from Dave Hill:
(Ed Note: and was printed here with the permission of Tom Topalian, Lucent Technologies, Murray Hill, N.J)
FYI -- HDTV heating up... Date: 97-11-12 16:39:35 EST
BERKELEY HEIGHTS, N.J.--(BUSINESS WIRE)--Nov. 12, 1997--Lucent Technologies' Microelectronics Group announced today the first single-chip receiver for the North American digital television (DTV) standard. DTV is a new technology that will allow the broadcast industry to transmit a mix of crisp digital video, CD-quality audio and data to home TVs, personal computers (PCs), set-top boxes and other digital appliances.
The AV8100 is a complete system on a chip that can receive terrestrial broadcasts of high definition television (HDTV), multichannel standard definition television (SDTV), and broadcast data. It is the first commercially-available single-chip vestigial side-band (VSB) receiver compliant with the Advanced Television Systems Committee (ATSC) standard. VSB is the North American modulation standard for TV broadcasting.
"Our new receiver chip will help bring about a new generation of DTV-based products and services," said Ahmed Nawaz, vice president of network communications ICs at Lucent's Microelectronics Group. "Consumers will be able to receive new types of digital broadcast services such as web casting, stock price updates, software distribution and other interactive media thanks to enabling devices like ours."
The AV8100 is part of a high-definition television (HDTV) receiver chip set Lucent and Mitsubishi Electric Corporation (MELCO) have been jointly developing. Mitsubishi is now testing the chip for implementation into its front-end RF tuner and other products.
"For several months, we've been verifying the ability of the AV8100 algorithms, programmed on Lucent test boards, to receive ATSC signals over the air," said Tommy Poon, senior vice president of Mitsubishi Electric ITA Advanced Television Laboratories. "Those experiments have been very successful and now we've started testing the chip itself in conjunction with Mitsubishi's RF tuner system and video and audio decoder and display processor components."
The AV8100 chip interfaces with a variety of RF tuner front-ends to receive incoming DTV signals from terrestrial broadcast stations.
In addition, it performs three core VSB reception functions on a single chip. This integration reduces power consumption, system cost, component count and board space. Capable of receiving all 18 of the ATSC formats including HDTV as well as multi-channel SDTV and data broadcasts, the AV8100 receives digital signals at rates of up to 19.39 Mbits/sec.
The AV8100 is available in a 160-pin, plastic quad flat pack and is manufactured in advanced 0.35-micron, 3.3-volt, CMOS process technology for high performance and low power dissipation. Lucent has begun sampling the chip to beta-site customers and will start commercial sampling early in 1998. Volume production will begin within the second quarter of 1998 and is expected to fuel the availability of consumer-based DTV products by the fall of 1998.
Lucent's rich history in digital video technology includes 25 years of research and development from Bell Labs. The company provides expertise in digital communication applications that includes encoders, receivers and other integrated circuits (ICs) that link PCs to digital networks.
Recently, Lucent's Bell Labs and Microelectronics Group received an Emmy Award for their pioneering work in MPEG digital compression and other high-definition television work under the HDTV Grand Alliance. This August, Lucent joined Compaq, Microsoft, and Intel as part of the DTV Team to help accelerate the deployment of DTV technology for PCs and television sets.
Lucent Technologies, headquartered in Murray Hill, N.J., designs, builds and delivers a wide range of public and private networks, communications systems and software, data networking systems, business telephone systems and microelectronic components. Bell Labs is the research and development arm for the company. For more information on Lucent Technologies, visit our web site at http://www.lucent.com.
Lucent's Microelectronics Group designs and manufactures integrated circuits, and optoelectronic components for the computer and communications industries. More information about the Microelectronics Group's business is available from its web site at www.lucent.com/micro. CONTACT: Tom Topalian 908-508-8673 (office) ttopalian@lucent.com or Michael Jacobs 908-508-8225 (office) mejacobs@lucent.com
******************************************************* Subj: More Web pages and FYI
From: James Mendrala & Larry Bloomfield
A web site to go to for info on MPEG 2 and Grand Alliance info is: http://www.sarnoff.com/techpape.htm
There are two selections to choose from. The home page is Sarnoff Labs division of SRI.
The place for the ATSC standards is: http://www.ATSC.org
We have found that the fastest way to get the info from ATSC is to down load it as a ZIP file and decompress it later. It decompressesas a "doc" file and reads ok on Microsoft Word. And by the way - FYI - General Instrument is now NextLevel Systems
*********************************************** From the CGC COMMUNICATOR #205
DTV-TO-DTV INTERFERENCE PROBLEMS
In the Commission's haste to avoid DTV-to-NTSC and NTSC-to-DTV interference situations, they failed to anticipate a number of DTV-to-DTV interference problems. In addition, signal propagation anomalies in Southern California and elsewhere were not addressed.
Now, MSTV has published a new DTV channel assignment list in a first attempt to resolve these problems. The results of their efforts may be downloaded (WordPerfect) from: http://www.mstv.org/
Because of the cascading effect caused by the channel changes, about 350 changes were required in all. Your present assignment could be among them. However, the FCC is not obligated to accept any of MSTV's ideas. Further, Chris Buchanan of KRCA-TV claims that there are at least 10 technical flaws in MSTV's new plan.
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Subj: NBC's Digital Skypath Project
By: Larry Bloomfield
The station where I work is an NBC affiliate. We recently received a memo from the Project Leader of the NBC's Digital Skypath Project, dated November 14, 1997 that included, along with a questionnaire, some interesting educational information relating to the task of upgrading their Skypath distribution system from analog to digital. For those who don't know, Skypath is what NBC calls their network distribution system via satellite. They say that this new system will incorporate the latest compression, transmission and automation technology to make it more efficient and reliable then their existing system. The network wide transition project is expected to take about 18 months.
NBC is asking their affiliates if they have space to install the new racks of equipment near the existing analog racks to facilitate the ease
of the transition. NBC says that once the equipment is installed, tested and working satisfactorily, the old analog equipment will be
removed, freeing up some space. It is expected that nearly everything but the satellite dishes will be replaced in this upgrade.
The new Digital Skypath system will transmit component digital video exclusively. Conversion to analog will be accomplished with a digital-to-analog converter as required until the individual stations have made the change over to digital and no longer have the requirement. At that time NBC will remove the converters.
To bring the engineering staffs of their various affiliates up to speed on what NBC will be doing, they sent out a series of books from various sources along with the questionnaire. These books would be good in any engineer's library. Titles, authors and sources are listed below. Tektronix has always been good about the distribution of their books. Just ask your local Tek sales rep. Tek also holds seminars on digital technology. Ask your sales rep when and where the next one is and plan to send as many from your staff as possible. Even the most knowledgeable amongst us can learn from the review and the up dates they will present.
The printed material NBC sent out: *A Guide to Picture Quality Measurements for Modern Television Systems (Tektronix) *A Guide to Digital Television Systems and Measurements by David K Fibush with contributions from Bob Elkind & Kenneth Ainsworth (Tektronix) *Solving the Component Puzzle (Tektronix) *A Broadcaster's Guide to MPEG: - The MPEG technology in perspective by Ole Strender Nielsen and Nanna Eriksen (RE Technology AS) E-mail: osn@re.dk *The Engineer's Guide to Compression by John Watkinson (Snell & Wilcox Handbook Series) Sunnyvale, CA
In closing, it would be nice to know what the other networks/broadcasters are doing. If any of our readers know, please let us know and we'll pass it on.
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The DTV Tech Notes are published for broadcast professionals who are interested in DTV, HDTV etc. by Larry Bloomfield and Jim Mendrala. We can be reached by either e-mail or land line (541) 385-9115, (805) 294-1049 or fax at (805) 294-0705. News items, comments, opinions etc. are always welcome from our readers; letters may be edited for brevity. larrybend@aol.com --------- J_Mendrala@compuserve.com DTV Tech Note articles may be reproduced in any form provided they are unaltered and credit is given to the DTV Tech Notes and the originating authors, when named.
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