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 Some of the information may be out of date.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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April 22, 1998
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DTV Tech Note - 018
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Sharing experiences, knowledge or anything else relating to DTV, HDTV
etc. with your fellow engineers: That's what we are all about. We will send
this to anyone asking, just E-mail us. Welcome to all the new subscribers.
We hope you will participate with question, answers and/or comments. This
is YOUR forum!
*************
Additional THIRD PARTY QUOTES IN SUPPORT OF PROGRESSIVE SCAN
(carried over from our 17th issue.)
Michael Silbergleid (Television Broadcast): "Your decision should be
720-line progressive. Why? It looks better even at a lower number. Looks
can be deceiving. And 1080I looks great, at least when there is not a lot
of motion in the shot. Remember, an interlace frame is made of two fields
that contain half as many lines as a frame that occur at different moments
in time. Alvy Ray Smith, on his Website at Microsoft says that, to be fair,
1080I should be renamed 540I and 480I should be renamed 240I. The reason
for this is simple: In 1/60th of a second, the eye is presented the entire
720 lines of a progressive frame. But in that same 1/60th of a second, the
eye is presented only one field - 540 lines - of the 1080 interlaced
frame... Oh, by the way, progressive has some other benefits as well: It
compresses easier, there are no interlace artifacts, and it converts to
interlace a lot easier than interlace converts to progressive."
Dick Wiley Interview (Broadcasting & Cable, 12/4/95): "Our final report
will call for migration to an all-progressive scanning system as soon as
compression technology permits squeezing lines into it. And I think that
will come sooner rather than later."
Proceedings of the IEEE, Vol. 83, No. 7, July 1995, pgs. 1037-1038
Yoshitaka Hashimoto, Masanobu Yamamoto and Takashi Asaida of Sony Corp.:
Cameras and Display Systems: "There are two trends for area sensors in
television applications: 1) To further increase resolution and decrease
size with higher density pickups and 2) to adopt progressive scanning. By
increasing the vertical spatial resolution, image sensors that use
progressive scanning are better suited for format conversion and image
compression. The demand for these higher density, progressive scan image
sensors will be used in the next generation of broadcasting systems,
multimedia systems, and electronic still cameras. In the area of computer
interface applications, progressive scan and square-pixel structures will
be used in order to improve interoperability and image processing."
James Meyer, Thomson, CEO (The Hollywood Reporter, 1/12/98): "We will not
build a product that won't connect to all formats."
Alvy Ray Smith, Microsoft, (Scientific American, 3/98): "It's {interlace} a
roadblock on the way to convergence. It accommodates only low-resolution
text and graphics if you want to avoid flicker... Viewers will need an
expensive board to convert interlaced HDTV transmissions to progressive.
The board could easily cost $1,000. Even at a price, the de-interlacing
will not be perfect and will result in poorer image."
SMPTE, 3/81 Research and development on HDTV in Japan: "Picture quality
with 2:1 interlacing is almost equivalent to that of progressive scanning
with 60% of the number of scanning lines."
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Subj: Free Training and talks on DTV & HDTV
By: Larry Bloomfield
Leitch has developed a comprehensive advanced-television-training program
that began when they established a digital television (DTV) hotline and
created a DTV seminar for industry groups. Response to these offers was so
great that Leitch decided also to co-sponsor advanced television seminars
at Toronto's Ryerson Polytechnic University and participate in Harris' DTV
Express.
Leitch's own DTV seminar, entitled Destination Digital is free to
professional groups and societies in half-hour, two-hour or full-day
formats. The seminar is made-up of a series of modules, including (but not
limited to) the Basics of HDTV and DTV, the Role of MPEG Compression in
DTV, Network Origination, Local Station Architectures (suggests progressive
transition using SDI equipment), AES Audio, and the DTV Set of the Future.
Leitch offers custom training on its DTV Hotline during regular business
hours. Broadcast professionals with DTV questions can call (800) 231-9673
between 9 AM and 5 PM EST and request the DTV Hotline for free expert
advice on any aspect of DTV. For more information on any of Leitch's
training programs, call (800) 231-9673.
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Subj: 24/25 fps HDTV.
By: Jim Mendrala
Most of the "prime time" programming is shot on motion picture film by the
major studios at 24 frames per second (fps). Most of the film has been
transferred on an NTSC compatible telecine. It converts the 24-fps images
to 30 fps by the introduction of a 3:2 pulldown. In Europe where they run
in PAL at 25 fps, film is transferred at 25 fps. The difference between
24fps and 25 fps is only 1% and usually goes unnoticed. So it was just a
matter of time before the benefits of a better picture with savings in Bits
would be realized.
The most frequently asked question is: "How can you view a flickering 24
Fps signal?"
The answer is that you display the film at a multiple of the frame rate.
Today's monitors are obsolete for this new DTV Standard. New monitors and
DTV receivers will be compliant with "Table 3" and will output a signal
that is compatible with the display. Kind of similar to the new breed of
video projectors that are being perfected.
When DTV starts this fall a lot of people will opt for a "set-top" box to
see the new DTV programming. This means that the DTV signal will be
received and converted to an NTSC composite signal and modulate an RF
carrier (Channel 3/4). Lucent Technologies and Sarnoff/Motorola have these
chips now and both have demonstrated them at the Consumer Electronic Show
(CES) and the NAB'98.
By going to 24 fps there is roughly about a 30% saving in the bit stream.
By using these savings in bits a better MPEG encoding will result.
The DirecTV, PrimeStar and Echo Star Satellite Companies are theoretically
capable of that today. DirecTV is already transmitting 720 x 1280 HDTV as a
test and will be accessible by its subscribers later this fall.
Once you see progressive scanning and compare it to interlace, the majority
agrees that progressive is better.
Film, in most professional telecines, is progressively scanned and has been
for quite some time. Both flying spot scanners and linear array CCDs scan
the film progressively. In today's telecine the frame store is readout as
odd lines first and even lines last. This creates the interlace that NTSC
has to have for transmission. 1080i because of interlace requires more bits
to work properly because the two fields are done individually and adjacent
picture elements are 1/30th of a second apart. In reality the image is at
1/2 the resolution per field and only if the image is stationary will the
image look better. Any movement of the scene or camera will become a half
resolution image. Crawls in progressive scan do not show any artifacts
compared to interlace.
Film has always had that so-called "film look". One reason is that it is
progressively scanned.
Therefore, I predict that 24 fps progressively scanned, will become the
defacto standard for DTV. 1080i at 60 fields and 30 fps will look worse
than 1080p at 30 fps. Even 480p is better than 480i. It is also interesting
to note that only three of the DTV's 18 formats are interlaced. DTV allows
us the transmission of images in the progressive mode that NTSC never could
allow.
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Subj: SMPTE & USC sponsored Conference
By: Vicki Popielinski
You are Invited to the First Conference to offer a Comprehensive View of
Production & Display Technologies for High Definition Television, sponsored
jointly by SMPTE and the University of Southern California on May 16, 1998
in the Norris Cinema Theater, USC, Los Angeles, CA
This one-day conference will feature the following: * Display Technology
Overview CRT, LCD, DLP, Plasma Display
presented by Disney Imagineers
* Applied Advanced Television Technology
including RCA & Panasonic representatives
* Delivery Methods for Advanced TV, Satellite TV, Terrestrial TV, Cable TV
presented by DirectTV, ABC & Cable Labs
* Production Techniques for Advanced Television for 16x9 & 4x3 Display,
Film production, Electronic Production
presented by Columbia TriStar, Eastman Kodak, KCTS-TV
* Post Production Techniques for Advanced Television, Telecine transfer,
Format Conversion, Episodic TV
presented by Warner Bros. Video Ops, Snell & Wilcox & Laser Pacific
reps.
* Round Table Discussion: "Achieving Success in the Era of HDTV"
* HDTV Exhibition View first-hand actual ATSC digital television
signals
Evaluate first-hand, picture quality on consumer televisions
* The conference will feature guest speaker and moderator Charles Poynton
Please call to obtain additional information from Vicki Popielinski / VP
Communications Phone 818.990-1628 o fax 818.907-8195 E-mail vpc@lafn.org
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Subj: CORRECTION & Some notes
From: Larry Bloomfield,
About half way through NAB, I noticed that my business cards from Broadcast
Engineering had my telephone area code wrong. Please be advised that it is
541. They had the 2nd and 3rd numbers reversed. The E-mail address was
also incorrect: There is no _ between Larry and bend. Once discovered, I
tried to correct the mistake by pen. My particulars are as follows:
Larry Bloomfield, News Technical Editor, Broadcast Engineering, 521 Forest
Grove Dr., Bend, Oregon 97702 -- (541) 385-9115 I have no FAX and my E-mail
= larrybend@aol.com
Notes:
(1) We now have over 150 subscribers and we're on the SCRI web page. Check
it out: http://www.scri.com, click on the camera and you'll see us listed
there. It takes a week or two after we put it out on the E-mail to get on
this web page.
(2) I'm looking for input on success stories from NAB. If you had a
particurarly good NAB show, please let me know. Also if you saw anything
in particular that stood out to you, was interesting or different, please
let me know this also.
(3) There were some rumors running around NAB about HNK and something to
do with 720p vs. 1080i. Once source said Microsoft had something to do
with it also. I'm trying to track them down and find out what it was all
about, if anything. Help kill rumors. Let me know please.
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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.
END
