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DTV Tech Notes

% Larry Bloomfield & Jim Mendrala

(541) 385-9115 or (805) 294-1049

E-mail =


April  22, 1998


DTV Tech Note - 018


     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!  



(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."


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


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. 


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



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


* Round Table Discussion:  "Achieving Success in the Era of HDTV"

*       HDTV Exhibition View first-hand actual ATSC digital television


        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


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



(1)  We now have over 150 subscribers and we're on the SCRI web page. Check

it out:, 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.


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.    

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