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 Some of the information may be out of date.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
(541) 385-9115 or (805) 294-1049
E-mail = larrybend@aol.com
J_Mendrala@compuserve.com
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December 9, 1997
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DTV Tech Note - 012
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Sharing 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 its done! Feel free to forward this on to your associates, but let them know that you've done so and its 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.
PLEASE DON'T USE OUR MAILING LIST FOR ANY PURPOSE with out permission.
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Subj: Wide Screen, Big Screen and HDTV Viewing Angles
From: James Mendrala)
In the coming months we are going to see what the TV set manufacturers are
going to have to receive the new DTV. While we are waiting let me say a few
things about the differences between Wide Screen, Big Screen and HDTV.
Television of today has an aspect ratio of 4x3. From the NTSC transmitter
we are able to receive an image of around 480x360 pixels. Because of the
limitations of the eye, as long as that image is viewed with a horizontal
viewing angle of less than eight degrees the viewer will see a high
resolution image on that screen. Now this viewing angle is not very wide
but fits nicely into the average living room with a 27 inch diagonal
conventional display. If we now implement the new DTV with its 702 pixel
wide image, we will be able to transmit the same images with a higher
horizontal resolution. The vertical resolution would still be around 360 as
it would remain the same.
In an article by Frank Becham in the TV Technology (Vol. 15 No. 22 Pg. 8),
Sony's Larry Thorpe explained that as long as the amount of spectral energy
(bandwidth or detail) in the scene does not exceed the limits of the
525-line television system, standard definition will look about the same
as a high definition. This means that if you are viewing an image from an
SDTV DTV transmitter with a 27 inch diagonal screen at a viewing distance
of 17 feet you would have a viewing angle of about 8 degrees. A high
definition image would look similar to that of an SDTV image on that
display viewed from the same distance. If the SDTV image was blown up or
magnified to a 32 degree viewing angle, it would look soft.
Viewing angle is related to bandwidth, or as Larry Thorpe likes to say,
Spectral Energy. A lot of manufacturers already know that their video
demos (using close-ups of people, flowers, animals, etc.) are quite
spectacular. These images contain less spectral energy and lower bandwidth
and less detail. We've all seen this at TV trade shows regularly.
We know the number of scan lines in NTSC and SDTV are fixed at 525 lines
and by definition cannot be changed. So we are stuck with 360 vertical
pixels (525 lines minus vertical blanking and other non picture lines,
times the Kell Factor.)
If you have a 27-inch diagonal display that can resolve 480 horizontal
pixels, you would have to be about 13 ft. from the screen to view a NTSC
image, as transmitted, in high resolution. This is a viewing angle of about
8 degrees.
If the 27-inch display could resolve 720 horizontal pixels, one and a half
times the resolution of NTSC, DTV then would move you up to a viewing
distance of about 8.5 ft. This is a viewing angle of about 12 degrees. But
the same number of scan lines in the 4x3 image would mean the vertical
resolution would be less than the horizontal resolution. This is not good
because the image should have equal vertical and horizontal resolution. By
changing to a wide screen image we now have equal horizontal and vertical
pixels.
If the 27 inch display could display 1920 horizontal pixels (five times the
resolution of NTSC), DTV then would move you up to about 3 ft. from the
screen. This is a viewing angle of about 32 degrees.
Now if all of the above images were viewed at the same distance of 13 ft.
then all would have a viewing angle of 8 degrees. All images would look
similar at that distance. Reason? The eye (for the average person) would be
at its limit of resolving detail of less than one minute of arc. Even
though HDTV has more bandwidth, spectral energy, or detail, the images at
the 8-degree viewing angle would look similar.
Computer monitors typically can display about 72 dots per inch. A 21 inch
monitor with a .28 dot pitch could display up to about 1200 horizontal
pixels. This is less than HDTV's 1920 pixels. Making the screen larger with
the same .28 dot pitch we reach a point where the tube would be too large
to get it through the average doorway. Therefore it appears that the
maximum size screen for a CRT device would be about 34 inches and could
resolve about 1920 horizontal pixels. The minimum viewing angle for this
would be 32 degrees and you would be 4 ft. from the display. Any closer and
you would exceed the minimum viewing angle and your eye would start picking
up artifacts in the image. Further away the viewing angle would be less
than the minimum and the image would look fine except smaller.
If the viewer was at a distance of 8.5 feet, then the NTSC image would NOT
look as sharp as the DTV or HDTV image.
Another factor is that in the NTSC image we only have about 360 lines of
Vertical resolution. Now if you take that vertical resolution and bump it
Up to a 16x9 screen to get square pixels the horizontal pixels needed would
be 640 and now you could view the display at the 12 degree viewing angle.
This DTV 16x9 wide screen image would look much sharper than a NTSC 4x3
image with its fixed vertical resolution.
Now we get into what HDTV is about. From a viewing distance of 13 ft., the
same as for a 27 inch diagonal NTSC display, the screen size jumps up to a
much bigger and wider screen. A screen for this new 32 degree viewing angle
would be about 7.5 ft. x 4.2 ft. Perfect for the home where the ceiling to
floor height is about 8 ft.
So what would the viewer like in his home, a standard 27 inch TV as we know
it today or HDTV-DTV with a BIG and WIDE screen?
Interestingly some of the new displays cannot display all of HDTV's
resolution of 1920x1080 pixels. A higher dot or pixel pitch will display a
lower resolution. Some viewers will opt for smaller screens. The plasma
flat panel display comes to mind. It is in the wide screen 16x9 aspect
ratio but, because of its lower resolution, the viewing angle will have to
be smaller. It will not be able to display all of the spectral energy or
detail in the image.
I have said, in a previous DTV Tech Notes, that camera personnel will have
to learn how to frame for this big wide screen as there is not any
convenient way to compose for both 4x3 SDTV and 16x9 SDTV or HDTV on DTV.
Sony's Larry Thorpe thinks that 16x9 SDTV will hold up quite well when
bumped up to HDTV, especially if the images are shot with a narrow-taking
angle with lower spectral energy (less bandwidth). A good reason to
consider a 16x9 wide screen camera.
A wide screen 27-inch diagonal DTV in 16x9 SDTV would definitely look
better than a 4x3 NTSC image at a viewing distance of 8.5 ft.. The NTSC
image would look soft.
I hope this helps shed some light on why HDTV is meant for the Home
Theater and why SDTV in wide screen would produce a better picture on a
16x9 display of limited resolution. For Big Wide Screens, you cant beat
HDTV.
Summing it up, the wider the viewing angle, the higher the bandwidth,
requiring more pixels, more detail, more bandwidth and more spectral
energy.
Jim
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From: THE CGC COMMUNICATOR #209
Dated: Monday, December 8, 1997
COMPETITIVE BIDDING FOR COMMERCIAL AND ITFS LICENSES -
FULL NPRM TEXT NOW AVAILABLE
http://www.fcc.gov/Bureaus/Mass_Media/Notices/1997/fcc97397.txt or
http://www.fcc.gov/Daily_Releases/Daily_Business/1997/db971201/fcc97397.txt
DETAILS OF THE BROADCAST APPLICATIONS FREEZE
While the Commission is formulating competitive bidding
rules (see above story), it has imposed a freeze on some
broadcast applications. Paragraph 61 of the above linked
text reads as follows:
...As an interim measure, we shall, effective upon the
release of this NPRM, impose a temporary freeze on the filing of
further applications in all commercial broadcast and secondary
broadcast services, pursuant to our existing procedures. During
the freeze, we will continue to accept and process petitions for
rule making requesting the allotment of new FM channels to the FM
Table of Allotments at any time, and applicants will be able to apply
for any such allotments during subsequently announced FM auction
filing windows. The freeze will apply to applications for new
stations and for major changes in existing facilities but not to
minor modification applications. It will also not affect the filing
of applications for new stations or for major changes in existing
facilities in the reserved portion of the FM broadcasting band
(Channels 200-220). Additionally, we will exempt from the freeze
any application timely filed in response to an outstanding AM (or FM
translator) cut-off list or to an open FM window, but we will not
issue any new cut-off lists or open any new filing windows.
FCC SEEKS COMMENTS ON FILING ADDRESSING DIGITAL TV ALLOTMENTS
On November 20, 1997, the Association for Maximum Service
Broadcasters, Inc. and other broadcasters (MSTV) submitted an
ex parte filing that presents suggestions for addressing two
issues relating to the Table of Allotments for digital television
(DTV).... The first of these issues concerns DTV-to-DTV adjacent
channel assignments. The second concerns assignments in the most
congested areas of the country the Northeast, Great Lakes region,
and California coastal area.
Comments are due by December 17. It is unlikely that this date
will be extended. To find out more, see:
http://www.fcc.gov/Daily_Releases/Daily_Business/1997/db971203/pnmm7238.txt
(Ed Note: Thanks CGC Communicator)
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Subj: A new book for your reference library
From: Larry Bloomfield
At the suggestion of Graham A. Jones, Engineering Director of Harris' DTV Express, I picked up a copy of "Issues in Advanced Television Technology," ($34.95 US - Soft Cover) by S. Merrill Weiss. Although this book is a little pricey for a soft cover, it is packed with a wealth of information. It was not a book that I read comfortably, cover-to-cover, and enjoyed. If approached on a subject-by-subject basis however, I found it to be interesting and informative. Since I don't have a photographic memory, Ill certainly keep it as a valuable part of my growing reference library. From what I read, it was not hard to ascertain that this work is an anthology of articles written by the author from his Advanced Television column in "TV Technology" magazine with one big exception: All the material has been updated, is indexed and, most important, is current and timely.
Weiss covers the subjects of digital video compression, transmission of digital signals, audio compression, adaptive equalizers, packetization, transport and program streams, multiplexing, MPEG-2, serial digital jitter, storage and servers, data broadcasting, and the motivations of the players in the media of the future. These are subjects that I hear executives at the networks giving public talks about that would have been better prepared had they read up on the subject matter in this book.
The author is obviously well informed and the material is presented in a relaxed, conversational style and his explanations are easily understood. The presentation of material is aided by the use of nearly 60 figures and 35 tables that help the reader understand even the more obtuse points. The back cover implies that this is not a textbook, but I disagree. Having taught Junior College for nearly ten years, I believe it would make a good textbook on the subject matter. The publishers, Focal Press, says that this is a book suited for and is of value to business managers making strategic decision, technical managers forming implementation choices, as well as system designers and operators preparing for future work assignment. I agree with them except for the business managers part. I have always been of the opinion that when bean counters stick their noses into things they don't know or understand, we end up with a camel instead of a horse. It is an excellent book for technical types, but I do not recommend it for anyone with out the background.
In closing, I d like to thank Graham for the suggestion. You too will value having this book, "Issues in Advanced Television Technology" as a part of your technical library.
Larry
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(Ed Note: This is a web site worth looking into. We've published their Dec. 3rd Headlines FYI. Check them out.)
Subj: SCRI's Broadcast / Pro Video News Briefs - December 3rd, 1997
From: SC Research International
Headlines Email Version. - news and views on broadcast and video production sectors, worldwide - The complete reports and articles listed in these News Briefs are
available online in the new SCRI Insider Report at http://www.scri.com
TECHNOLOGY NEWS:
SGI Demos Integrated HDTV / SDTV Post-Production Solution At SMPTE
First Digital Communications Tower in U.S. Obtains Final Approval
European Commission Halts German Digital TV Pact
Worlds First Single-Chip MPEG-2 Encoder
Impact of DTV on Translators and LPTV - A Larcan Presentation Report
Sony Delivers More Than 100 API's For DVB Set-Top Box and DVD Applications
Worlds First Commercial Introduction of Internet Access Via Open TV Web
Wave Phore to Broadcast WSJ Interactive Over VBI of TV Broadcast Signal
USA's First Interactive TV Sets - NBC Announces First Wink Enhanced Broadcasts
INDUSTRY NEWS
New Telco Solution To Provide Interactive Multimedia Services Using
Regular Telephone Lines
US Satellite Dishes Ruled Illegal In Canada
VDI Media Acquires Fast-Forward Inc., SF's largest Video Duplication House
Power Trader Software Inc. Announces National Television/Internet Joint Venture
DirecTV Debuts In Crowded Japan Digital TV Market
NEC, Philips tie up to develop chips for consumers
COMPANY NEWS
Tektronix to Pump Resources Into Digital Video Technology Initiatives
Tektronix to Discontinue Older Grass Valley Group Products
Faroudja Labs Gets a Buy Rating From BancAmerica
Sony Electronics Arm Expected to Hit $10 Billion Revenue Mark
Leitch Technology Corporation Revenues and Profits Up
Fairchild Aquisition Provides Entry into the Analog and Mixed Signal Technologies Markets
PRODUCT NEWS
Sony's Digital Betacam Used By Video Game Developer
New Tek Announces Limited Time, Light Wave 3D 5.5/Film Grain Bundle
Strong Response at Comdex to FOCUS Enhancements PC-to-TV Chip
New PC-TV Convergence Solution at Comdex Goes Beyond The Little Black Box
LBT 4040 Prototype Cable Modem Chip to Be Demonstrated at Cable Net 97
New WAN Access Products and Higher-Density ATM Provide High Performance
Data, Voice and Video Service Integration
Scientific-Atlantas New Fiber Optic Broadband Platform Provides Cost
Savings and Increased Revenue Potential
PEOPLE IN THE NEWS
Highly Qualified Chief Engineer and DTV Expert Available
BSkyB Outlook Seen Unchanged as Exec Leaves
Alliance Acquires Citadel Entertainment and Retains David Ginsburg as Citadel CEO
RESEARCH NEWS
Internet and the Web Increasing in Importance as a Source of Product Information
to Broadcasters and Pro Video Users
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Subj: Hi Def hardware sample
FROM: Shelly Jacobs, Managing Director, MEDIA CREATIONS
See Universal Studios Hi Def Telecine page at:
http://www.mca.com./studio/city/post/telecine.html
Regards, Shelly
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Subj: Lest we forget.......
From: Larry Bloomfield
Since this is the holiday season, we thought we'd digress a little from our more serious side and make a few observations. There are terms we use every day in our business and never give them a second thought. This newsletter is called DTV -- (digital television) technical notes. Why ? And what is digital? Our dictionary says: "Digital - adj. 1. Having digits. 2. Expressed in digits, especially for use by a computer." A more correct term would be Binary. Just think "BTV Tech Notes." Why? Using the same authority as before, the dictionary: "Binary - adj. 1. Characterized by or consisting of two parts or components; twofold. 2. Of or relating to a system of numeration having 2 as its base." So we say digital and really mean binary. Go figure! For the sake of sanity and this article, we'll use the terms interchangeably.
Our definition of terms would not be complete if we didn't look at the definition for the word television: "Television - n. 1. The transmission of visual images of moving and stationary objects, generally with accompanying sound. 2. The industry of producing and broadcasting television programs." We could fill a book on definitions alone. We'll not do that; let's just continue.
From the book that was reviewed in our last issue, one would think that digital television was something relatively new. We don't think so! We've been using both visual and non-visual digital or binary techniques in communications for centuries. We're talking a long time and then some. Your knee-jerk reaction is to say that the author has lost it. Not so. Using the definitions above, aren't "smoke signals" visual images of moving, binary or digital information. What about the flashing lights the Romans used thousands of years ago? If you'll permit us to remove the visual part of our definition, we can include the beating of drums. To be more picturesque, you can call them jungle drums. But isn't that still digital and still communicating?
The purists would say that the communications we are speaking of has to be electronic. OK then, several years before the famous message , (What hath God wrought?) was sent between Baltimore and Washington, DC, the principals of telegraphic communications had been demonstrated. This truly is binary or digital communications.
And what about compression. Compression is the principal or concept of packing more information into a given time and space. If that's true, the early telegraphers used automatic keyers and in the early demonstrations of telegraphy, the message was actually recorded on paper by an inking device for decoding (now there's a familiar term) at a later time. As the telegraph gave way to the Teletype, they even employed compression then too when they used electromechanical keyers and the streams of punched paper tape. Are we reinventing the wheel? Is what we are doing really all that new? Well I'm sure many of you can come up with more examples. I had fun writing this and thinking of the ancient possibilities. The idea of all this was to have fun and just get you thinking Well that's our excursion into De Ja Vue. Thanks for putting up with our conjectures. Hope you had as much fun reading this as I did writing it.
Larry
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Subj: Some things to consider..... and not just for the newcomers.
From: Larry Bloomfield
Since this is the time of the year that most everyone reflects, we'll leave you with these few thoughts: When all those around us say that something can't be done, why does it usually take someone who doesn't know that he or she can't do it, to succeed and make it happen? It could be that they never let what they can't do interfere with what they can do. If you think you can, you can. And if you think you can't, you're right. I guess, as Thomas Edison said: "If we did all the things we are capable of doing, we would literally astound ourselves."
Permit me to share with you some thoughts which I made into notes a long time ago. These thoughts have been developed over the years. Some are original. Some are not. It's been so long since I began these notes and they have been refined time and time again, I truly can't remember the source of most of them. I do share these thoughts with every student of mine, be it in the classroom or on-the-job. Feel free to use them as you see fit and if you have anything to add, please send them to me. Here goes:
Learn and understand thoroughly the basics. They are of the up most importance. The basics are the building blocks of the remainder of your carrier. Don't take lightly the history of our industry. Have a good knowledge of how things began. They say that those who don't know history are condemned to relive it. In your work habits, if you know how, you'll always have a job. If you know why, you'll be the boss. Commit yourself to quality from day one. Just remember that your chances of being run over are doubled if you stay in the middle of the road. On the other hand, if things aren't moving fast enough, consider the turtle_ It can't move at all if it doesn't stick its neck out. Don't try to do something cheaply that shouldn't be done at all. It's better to do nothing at all than to do it badly. The bitterness of poor quality remains long after the sweetness of meeting the schedule has been forgotten. The fastest runner does not always win the race. Sometimes those who just keep running, win it. If, however, in that race you come to a turn in the road, (and you will), it's not the end of the road unless you fail to make the turn. Avoid short cuts. They always take too much time in the long run. If you wish to finish sooner, take your time. People, however who wait for all conditions to be perfect before acting, never act.
You will not always agree with your fellow engineers, but worrying about what's right is always more important than worrying about who's right. People take different roads to achieve success. Just because they're not on your road doesn't mean they've gotten lost. If you must go into battle, be thoroughly prepared. It's better to win the first time. It's not weather you get knocked down. It's weather you get up again. The guy who makes no mistakes usually doesn't make anything. Learn from the mistakes of others. You won't live long enough to make them all yourself. Never be afraid to say, "I don't know" -- The important people will respect you much more and will always place more weight on what you do say.. because they know you're right. Beware, because people who will lie for you, will lie to you.
If you don't think you are making enough money, just remember that wealth comes to those who make things happen and not to those who let things happen. Stay on the cutting edge. Keeping up is always easier than catching up. If you think education is expensive, wait till you see what ignorance costs you. If you keep doing what you're doing, you'll keep getting what you're getting. Never underestimate the importance of money. Right or wrong, it's how business people keep score! On the other hand, never overestimate the value of money either. Cash is important, but sometimes not as important as respect, thanks, integrity, or the thrill of a job well done. Try to convince your employer to spend the extra dollars to maintain the equipment properly. It's like brushing your teeth -- you only brush the ones you want to keep. If you are a competent engineer and your employer doesn't listen to your suggestions, get a second opinions. If this situation continues, get a second employer. Document all that you do. Not many of us have photographic memories.
Knowledge, information and education are priceless. Get them at any cost. You can not afford not to.
Those are my standards, what's yours?
Larry
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In the event we do not put out another issue of this newsletter before the holidays, Happy and Merry Everything.
Larry & Jim
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A fairly knowledgeable (HDTV - DTV) engineer is looking for an employer. If you are interested, please advise and we will pass it on to him. Thanks.
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Last minute item: From: Jim Mendrala
Just heard that the Super Bowl Kick Off will be shot in HDTV. That will
be sometime in January of 1998.
More later. ---- Jim
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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 (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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