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 Some of the information may be out of date.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
% Larry Bloomfield & Jim Mendrala
(408) 778-3412 or (805) 294-1049
E-mail = larrybend@aol.com or J_Mendrala@compuserve.com
April 11, 1999
DTV Tech Note - 028
The Pre-NAB Edition
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Published when any of us have something to share and it is sharing our experiences, knowledge or anything else relating to DTV, HDTV, etc., with fellow engineers: That's what we are all about. We will send this directly to anyone asking, just E-mail us. There is no charge for this Newsletter and no one gets paid (sigh!). If you are receiving this newsletter and want to get off the list, just e-mail us that request. There is no "majordomo," automatic server; we administer this manually. We hope everyone will participate in all ways with comments, experiences, questions and/or answers. This is YOUR forum! Past issues are available at: WWW.SCRI.COM. Welcome to all new subscribers. We're now over 260.
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Subj: What's in a Name
From: Bobby Lee Lawrence
At the risk of being picky, the Sony TV at the museum on display showing HD the night of the SMPTE meeting is a VEGA not a WEGA. We all make the same mistake even at Sony. Please add me to your mailing list. I have been receiving the notes via other sources and would like to get them direct. Keep up the good work,
Regards,
Bobby Lee Lawrence, Regional Manager, Sony BPC
(Ed Note: Duly noted in both cases and welcome.)
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Subj: Response to a phone call
By: Larry Bloomfield
My associate and co-publisher, Jim Mendrala, wrote his observations of what he saw at the Consumer Electronics Show (CES) in Las Vegas earlier this year, which appeared in DTV Tech Note #024, dated January 15, 1999. His article: "HDTV in the ATSC DTV Standard is in Trouble," began: "With a lot of expectations, the touted HDTV capability of DTV is in trouble. There are a lot of reasons why, and the broadcast community will have to band together if it is going to get HDTV off the ground." (The complete article can be seen at www.scri.com)
The very last sentence in all of our newsletters states: "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." We were advised to change this policy by an Executive Director of an organization in Washington, D.C. who was very irate over something that had appeared here and subsequently quoted, intact, in another publication. This has been our policy since we began and will continue to be our policy in the future.
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ATSC, etc. - Some observations and comments.
By Larry Bloomfield
There has been a great deal of conversation on several e-mail forums, which Jim and I subscribe to in our efforts to keep abreast of what's going on in the wonderful world to DTV, about problems with ATSC and reception. Many of the correspondents are very knowledgeable and willingly share their vast storehouse of knowledge, but like any body of people, there always are a few who tend to emulate that part of the antinomy which one tends to sit on. Some even speak as if that's where their vocal cords were located. I'm sure there are those who have counted me as one who has done a fine job of developing this trait, but that doesn't seem to stop any of us.
That all aside, I have been following, with a great deal of interest, the concerns of several who are of the opinion that we, the American broadcast industry, have made a very serious and grievous error in selecting 8VSB as our method of modulation. If that is true, the time is now, not in the future when most of the country has made the switch, to take what ever corrective action that may be necessary. Several questions come to mind. First, can we fix what we've got or are they're any ways to salvage it? You don know how I wished I had an answer to those questions. My fellow engineers, with whom I've spoken, don't seem to think so or are of the same frame of mind as am I.
Most all of us realize that the method of modulation is at the very core or heart of any transmitter system. We have to either fix it or change the type of modulation from 8-VSB (eight level Vestigial SideBand) to something else. Either path will have a seriously impact on our industry, not to mention those who have invested heavily in the migration (both at home and at the TV stations). Any changes won't arrest, but will seriously push back, the migration from analog to digital by a significant amount of time. The ripple effect will be incalculable! It will impact multichannel development and any of the perceived Datacasting (content-casting) services that are in development. As you know, these technologies are only possible in the digital world of television.
Many have suggested such modulations techniques as Coded Orthogonal Frequency Division Multiplexing (COFDM), like is specified in the DVB-T standard, but there have been some indication that it may have its' own set of problems. One thing for sure, we don't what to embark on a change only to find out that we need to change horses a second time in midstream. That could all but kill the industry.
The broadcast community is like an inductor, it will oppose any change in current flow, so it's not likely that any of this will happen, but, as stated, there has been a lot of fuss, from a number of different sources about 8VSB not being very robust. The exchange in coverage broadcasters will go through when they move from NTSC coverage to the coverage that appears to be what comes with 8VSB is not equitable in most cases, especially if indoor antennas are considered. The DTV (8VSB) broadcaster is going to come up short.
Sinclair Broadcasting has already raised this issue and has demonstrated that the initial power allocations given DTV Broadcasters was insufficient. They got the FCC to up the power levels and change the signal levels out at specified distances from the transmitter. Examples of the kind of problems they are discovering are with high power levels in the city grade contours that create very objectionable multipath, which is disastrous.
Sinclair has even taken it further and demonstrated that reception with the 8VSB system is only good typically when the viewer has an antenna (nominally 30 feet), with a clear shot to the transmitter site, outside his house (or whatever), but not everyone lives where this is possible. Apartment dwellers are in deep trouble. Rabbit-ear antennas just don't work, according to their survey and a number of others that have taken place in the "real world." This was discovered only after a few DTV stations had gotten on the air.
COFDM, which came out after 8VSB, appears to be more robust when it comes to using indoor antennas, antennas in a mobile environment and is not nearly affected by multipath. The need for tall antenna structures at your home may still be necessary in the distant areas, but not close in, as is the case with 8VSB.
I wrote an article for the May 99 issue of BE that reports on a survey I made of a number of Chief Engineers across the country who believe that this move to DTV with 8VSB will relegate terrestrial television to the roll that AM radio stations now play. Most feel that viewers will get their signals either via Satellite or some form of cable.
The issue boils down to the type of modulator that is used in the very flat; over it's bandwidth, transmitter. The retrofit would be more reasonable now than if we wait until more stations have come on to the digital airwaves.
I believe if Sinclair and the others who are pushing this really serious issue are successful, the whole idea of DTV will go into limbo and get put on hold for about a year or so. Are we ready for that? Yes or no, we're at a crossroads and the signals are flashing. We've got to do something. As the man once said, lead, follow or get the hell out of the way. Digital television will make its visitation on us in one form or another, sooner or later and that you can bet on.
One redeeming factor is that most of the DTV ready TV sets accept video, audio and data bitstreams only after they have been demodulated, having no tuners or RF sections. Many DTV ready TV's today do not have their tuners built in and rely on a STBs (set top boxes) to demod their signals.
A concluding though: assuming this is all true and we do nothing, you can bet cable penetration will increase and the need for terrestrial broadcasters will diminish accordingly. If you think that cable tries to be in the driver's seat now, standby, they'll have you by the you know what! If nothing else, all of us should be considering what impact this will have and can we weather the storm? Good luck
A note from Larry and on Jim's behalf:
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NAB Notes:
As of this writing, Jim is somewhere in a car traveling between Los Angeles and the Eastern Seaboard, but we'll both be at NAB '99. We'd sure like to meet as many of you as would care to say hello. As many of you know, I wear three hats: DTV Tech Notes, Broadcast Engineering and SunUp Digital Systems. Broadcast Engineering and SunUp have set aside Monday, 1 to 3:00pm and Wednesday, 2 to 4:00pm at the SunUp booth (S-2559) so Jim and I can meet anyone who'd care to stop by. The remainder of the time Jim will be on the convention floor visiting booths and I'll either be at the Intertec booth (Broadcast Engineering) or tooling around in my electric go-cart from press conference to press conference. If you see either Jim or I anywhere, step up, introduce yourself and say hi. It would be nice to put a face with the e-mail address.
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From: Randall Paris Dark
Subj: HD Vision and their new HD remote truck
HD VISION provided Bill Young Productions of Houston, Texas with mobile unit HDV-3 for their taping of The George Strait Country Music Festival in Tampa, Florida. This was the maiden voyage for HDV-3 following the installation of a new Snell & Wilcox HD1024 Digital High Definition Production Switcher. Also on board were six Sony HDC-500 cameras, two Sony HDC-750 cameras, four HDW-700 camcorders, five Panasonic HDD5 recorders and two Sony HDW-500 recorders.
The George Strait portion of the Country Music Festival was recorded as a live concert on Saturday evening, March 27, 1999. A music video for the new George Strait single "Write This Down" was edited from the concert video and delivered as a final approved music video on April 1st - a four day turnaround! Working under a tight deadline, the HD VISION and Bill Young Productions crews worked long into the night to provide selected Digital Betacam down-conversions for the music video on-line. Gary Foster, Bill Young Productions' chief editor, delivered the video on time to MCA/Nashville.
Gary, who was also Technical Director for the shoot, said of the HD VISION facility and support team "It is the most professional I've worked with in years. When we arrived at the shoot we realized that they had totally re-engineered the truck just for us. Now, that's service! The new Snell & Wilcox HD1024 switcher was a joy to work with. I felt totally comfortable after only five minutes at the controls. My only wish is that the deadline had allowed us to actually edit and deliver the music video in high definition. The full 105 minute concert should be wonderful." (The concert will be off-lined at Bill Young Productions and then on-lined at HD VISION for eventual broadcast in both high definition and over regular television.)
Bill Young Productions founder Bill Young also enjoyed the experience of shooting in high definition. "Working with HD VISION was a delight. They are professional and, most of all, passionate about the quality of their work."
You can see some of the concert footage, as it will be used for demo purposes at the Sony Booth during the NAB convention in Las Vegas. David Washington, Manager of Broadcast Production Applications accounts at Sony's Business & Professional
Group office in Irving, Texas, had this to say about Sony's NAB use of the material. "We are proud to showcase the material of legendary Country & Western performer George Strait and the technical and creative collaboration between Bill Young Productions, one of the most respected names in artist promotion, and HD VISION, one of the true pioneers of high definition production."
The concert was also Webcast to over 9000 viewers from the George Strait web page, http://www.georgestrait.com. This is the first High Definition concert distributed live over the web. Sid Farbstein, Bill Young Production's New Media Director, worked with HD VISION's engineers to get the best quality possible for the web images. "Working from original high definition images allowed me to provide the best possible pictures to George Strait fans watching the concert throughout the world via the Internet. The quality of the Webcast was reported by Real Networks as some of the best video ever seen streamed over the Internet."
TV, Web and potential CD release audio recording was by TNN Nashville. Audio was mixed by TNN staff and engineered by Steven Tillisch, using the Neve Capricorn console and Studer 48-track Digital Recorder.
Digital audio word-clock sync between the high definition mobile and the audio mobile was managed with the new nVISION SG-4410 Master Digital Audio Generator.
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Editors note: The following three items are courtesy of the CGC Communicator which is published by Communications General Corporation (CGC), consulting radio engineers, Fallbrook, CA.
LIGHT SLOWED TO 17 METERS/SECOND
While many substances slow the velocity of light a little bit, a breakthrough experiment has slowed a traveling light pulse to a crawl of 17 meters per second. Light ordinarily zips along at 300,000,000 meters per second.
While still a laboratory phenomenon using super cooled devices, this remarkable slowing of light raises the possibility that wideband optical delay lines and other extremely useful devices will emerge. See Science News, Vol. 155, page 207, for details. "This experiment is the stuff that Nobel prizes are made of," comments Marlan O. Scully of Texas A&M University at College Station.
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FCC RELEASES Y2K COMMUNICATIONS SECTOR REPORT
http://www.fcc.gov/Daily_Releases/Daily_Business/1999/db990330/nrmc9014.html
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SCANNERS RULES TOUGHENED RE CELLULAR FREQUENCY LOCKOUT
http://www.fcc.gov/Daily_Releases/Daily_Business/1999/db990402/fcc99058.txt
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Correction:
Thanks to Don McCroskey for pointing out that we had erroneously listed "Steve Bloom" of KCBS and it should have been "Steve Blue". Our apologies to Mr. Blue for misspelling his name.
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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 lines (408) 778-3412, (408) 437-4500 ext. 271, (805) 294-1049 or fax at (805) 294-0705. News items, comments, opinions, etc. are always welcome. Letters may be edited for brevity, but usually not.
>>> 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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