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DTV Tech Notes

% Larry Bloomfield & Jim Mendrala

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

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May 13, 1998


DTV Tech Note - 019


     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 new and long time subscribers will participate with question, answers and/or comments. This is YOUR forum!



This Saturday, May 16 the Local Hollywood Section of SMPTE will present an all day Seminar at USC on Advanced/HD Television.  This event will present many speakers and presentations and will also feature an extensive exhibition of Consumer and Production/Post Production Equipment.

The highlights of the Presentations include:

--Charles Poynton--Tutorial  on the Viewing Psychophysics of Advanced Television

--Dave Taylor & Tom Brentnall of Walt Disney Imagineering--Display Technologies for Advanced Television (Examples in the Exhibit Area)

--Bruce Babcock--VP RCA/Thomson--Examples of Consumer Product for this Fall's  Receiver/Display Products Delivery Methods for Advanced Digital Television--This will be one

of the highlights of the Seminar--Find out the plans of the Delivery


--Bill Miller--ABC Network/SMPTE Engineering VP--The plans of the Terrestrial Broadcaster--Find out why ABC picked 720 Progressive.

--Dick Green--President, Cable Labs--Hear Cable TV's plans for carrying or not carrying all the Digital Signals at Full Resolution

--Jim Williams--VP, High Definition Production for Direct TV--The plans of Direct TV for HD to your home in the entire US this year

    Lunch Provided and Tours of the Advanced Television Exhibition

    Production Techniques for Advanced Television

        Production for 16 x 9 & 4 x 3 Display--

--Ed Lammi--VP Production for Columbia TriStar--He will show Examples of Columbia shows in HD Film Production in 16 mm and 35 mm

--Janet Anderson--Kodak--Examples of the latest film stocks in HD will be displayed Electronic Production for HDTV

--Marc Pingy--Producer/Director at KCTS-TV, Seattle--KCTS has produced many hours of HD all over the world Post Production Techniques for Advanced Television      

--Jan Yarbrough, Manager--Warner Bros. Video Operations -- Telecine Transfer--Methods and Techniques

--Leon Silverman--Laser Pacific Hollywood--(One of largest Episodic Post Operations in the World) Episodic TV Post-Production

--Adolfo Rodriguez--Snell and Wilcox--Format Conversion --Examples and Working Hardware will be shown--Down Conversion, Up Conversion and Aspect Ratio Conversion will be shown

    The Afternoon will Close with a panel discussion with many of the above presenters participating with the addition of:Gavin Schutz--Chief Operating Officer of 4MC--Probably the

largest Post Production Company in the World--Gavin is sure to bring us all down to earth with some of the practical financial and technical considerations

--Tom McMahon--Technical Consultant to Microsoft will discuss the integration of the new video technologies with the Computer Industry

    After the Seminar the Technology Exhibits will remain open for some time for you to examine the demonstrations--Details Below.

Some of the Exhibits are as follows--More to be added and the following in random order:

--Tektronix: WFM's for HD, MPEG Quality Assessment Equipment and HD Transmitter Testing Equipment, HD Test Signal Generators

--Dolby:  How you will handle 6/8 Channels of  Audio in a Stereo Plant

--Kodak:  Direct CRT Viewing of 35/16mm Film Examples

--Fujitsu:  42" Plasmavision Flat Panel Display

--Cable Labs:  Actual Cable Transmission of HD with Set top Decoder connected to High Definition Display via 1394/Firewire connection

--Digital Vision:  Products for HD post production

--Barco:  HDTV Displays

--Philips:  Live 16 x 9 525(480I) Camera for Up Conversion Source, Examples of Spirit High Definition Transfers

--Sony HD Center, Culver City--Playback of HD transfers of motion picture material

--Sony:  HDCAM Camcorder, HD Studio Cameras, HD Monitors and CRT Projection and Consumer HD Displays(Flat Panel WEGA Trinitron HDTV)

--Panasonic:  HD-D5 Recorders Playing both 1080I and 720P, 480P playback, HD Monitors and  Consumer HDTV's

--Microsoft:  Actual Terrestrial HD transmission with Receiver with line Doubling--Progressive Display and Demo of Television Reception with integrated auxiliary data and WEB reception

--Leitch:  Products for HDTV Post Production

--VAS Group:  Down Conversion and Aspect Ratio Conversion

--M & K:  Speaker System for 5.1 Channel Professional Audio Monitoring and for Home use

--Asaca:  HD Television Displays

--Philips/Polaroid:  Live 720P Camera and Playback of Philips NAB Camera Show in 720P

--Hughes/JVC Projection:  Full Screen Projection of HD in the Norris Theatre and Projection in the Typical Living Room HD Demo Area

A Special Display will show a side by side example of identical 720P and

1080I Telecine Transfers displayed on identical monitors.....You Be The


More Displays will be added by Saturday:  BE THERE............

For Further Details Call Herb Farmer At USC:

        Herb Farmer, USC School of Cinema-Television, 213-740-2921,

FAX: 213-740-2920   E-mail:

        He will FAX details and Seminar Sign-up Form.

Regards, Seminar Co-Chairs:

                    Bill Hogan, Sprocket Digital

                    Brad Hunt, Cintel

                    Nelson Meacham, Walt Disney Imagineering


From:  Mike Tinker                    

Head, Video and Multimedia Applications

Sarnoff Labs

609-734-2573 Fax: 609-734-2901

Princeton NJ 08543-5300

This is a late response, but I couldn't let it go by.  In Tech Note #17 you say:

"Probably the most intelligent thing I've heard said to date on this whole matter is that if a 1080 progressive scan algorithm could be developed so it could fit into a 6 MHz. bandwidth, that would be the Holy Grail of TV and I agree."

True.  And it's already been done.  In fact, there are two 1080 progressive formats in the ATSC standard--at 24 Hz and 30 Hz.  As my friend Jim Mendrala points out in Tech Note #18, film is mostly 24 Hz.  A 1920x1080 image at 24 Hz fits film nicely.  In order to make it look flicker free, the display should run at 48 Hz or 72 Hz, equivalent to a two- or three-blade shutter in a film projector.  Note that 72 Hz is a common frame rate for computers, so that film originals digitized and shown on a computer monitor with appropriate resolution should look pretty good.  Actually, seen on DTV, films should look better not only because of the better resolution and progressive scan, but because the ATSC 1080 progressive format (i.e., Holy Grail) at 24 Hz eliminates the need for three-two pulldown. 

Most prime time footage is shot on film anyway. The ATSC standard allows that footage to be displayed in all its pristine glory, without all the NTSC artifacts that now clutter it up. Hollywood should be ecstatic that there is a format designed specifically to make their images look as good as possible.

Mike Tinker


Hardly a week goes by that the FCC Daily Digest doesn't list a Memorandum Opinion and Order (MO&O) addressing one "Must Carry" issues or another. What's interesting is FCC R&R 76.55 makes no provision to exclude or include the new DTV service.  The timetable for conversion to the digital service is very clear and defined.  According to this same timetable, one of your two channels must be turn back over to the FCC, leaving you with a DTV signal on the air in the core channels of 2 through 51 in 2006.  As the new digital services come on line and this transition takes place, what will the cable companies be doing to give you DTV service and when do they have to do it?

John Malone, CEO of TCI answered that question while speaking to reporters during the National Cable Television Association convention in Atlanta, Georgia earlier this month, when Malone said that networks, other than CBS and NBC, are using formats that won't take up too much space.  Unless those two (CBS & NBC) change, Malone said, TCI would not voluntarily carry their stations on local cable systems. In an earlier statement, Malone said TCI would carry CBS and NBC's high-definition signals only if required. "I'll do whatever the government orders me to do," he said.  Remember that these are the same people who claim that the 480-scan rate is high defination television. (See Broadcast Engineering page 14, February, 1998) Leaving things to chance is not the way to do business.  In June of this year, the FCC will consider whether to force cable systems nationwide to carry broadcasters' digital channels. Based on what Ken Johnson, spokesperson for Congressman Billy Tauzin, R-LA, Chairman of the House Telecommunications Sub Committee, in reference to Malone's statement told me, there won't be much room to for the commission to consider.  He said:  "In a nutshell it looks like the cable industry just fired on Fort Sumter.  After cajoling, prodding and then finally mandating that American broadcasters convert to digital, Congress is not going to allow cable to become a road block to progress.  If John Malone wants a war, he'll get one."   

      Must Carry shouldn't be our only concern.  While attending a very well presented DTV seminar put on by Leitch's Mike Duckworth and hosted by the Boise chapter of SBE at the new PBS facilities in that fair town, this past week, the grass roots engineers there and elsewhere have expressed a great deal of concerned over what is to become of their translator.  It seems that, in some instances, over 50% of their view audiences receive their signals via translators.  It is not uncommon for stations in Idaho and Oregon to have 40 to 60 translators each.  Many of these translators are above channel 52.  Questions like will they interfere with the new DTV channels or will the reverse be the case.  This matter needs to be addressed and not left to the last minute. 

All this considered, the cost to replace that many translators is sure going to put a dent in someone's budget.  If we do not step up to the bat on this one and the cable companies keep wrangling around, there is one alternative, DBS.  With EchoStar and possibly other Satellite direct broadcast companies applying for direct local into local licenses from the FCC, these issues, in both cases, may become moot.


Subj: HDTV Down Conversion

By:   Jim Mendrala

I recently had the experience of recording some clips out of three major motion pictures in HDTV. Laser Pacific allowed me to use their BTS Spirit telecine and Panasonic AJ HD2000 D-5 recorder. The total time to color correct the three segments took about 5 hours. The difficulty was that there were a multitude of cuts in the film as well as flashing lights and special effects.

After the scenes were color corrected and the sound tracks delivered, The usual bars and tone were laid down then the three clips, with an edit after each clip, to the HD D-5 recorder. The pictures were excellent and met the client's approval.

Why the down conversion? Well these clips were to be playback into a video projector which according to the manufacturer could handle the HDTV signal with it's tri-level sync on green or Y, Pb, Pr with tri-level sync on the Y signal. They had tested this at the factory with a HDTV laser disc with a live video recording.

What happened was bizarre. The display device was an 800x600 array and because of the 600 pixels in the vertical it was decided by the manufacturer to use 540 of those pixels to display the HDTV signal. Since HDTV 1080i is interlaced all that would have to be done was to eliminate every other field, right? Sounds logical. Of course I was not informed of how they did it internally, only that it will accept a HDTV 1090i RGB or Y, Pb, Pr signal. This approach works well with live HDTV television just like it works fine in NTSC or CCIR-601, Correct?

Upon converting the output of the HD D-5 to analog through a Panasonic AJ HDA-500 to RGB with tri-level sync on green. the projected picture looked kind of like a Keystone Cops movie. Immediately I could see that the 3:2 pull-down sequence is what was upsetting the projector. Since the projector was capable of projecting PAL, NTSC and even SECAM, and Computer monitor signals, I immediately was in need of a way to down convert in real time.

PAL runs at 25 frames per second (fps) and 1080i runs at 30 fps. However the film ran at 24 fps and the 3:2 sequence was introduced into the video to bring the frame rate up to 30 fps. In order to down convert the 1080i 30-fps images to 25 fps sounded like it would be a very difficult task.

If one could establish which frames and which fields have the 3:2 sequence in them it would be easy to remove them. Statistically you have a 25% chance of hitting right the first time. Upon playback from the first clip playing, I used a Video Authoring Systems Group Inc. VAS, model RTC HD 3:2, to the HDTV Format and a HDTV master down to PAL. The RTC HD 3:2 will remove the 3:2 sequence and output the original 24 fps as a 625 lines, off speed, RGB signal at 24 fps.

Fortunately the D-1 recorder operating in the 625 mode and receiving its reference from the RTC HD 3:2 will record the 24 fps signal with no problem. Upon playback though the reference to the D-1 comes from a PAL sync generator at 25 fps. Therefore the running time is 4% shorter. A 1:00:00 program down converted will play only 00:57:36. The sound however has to be re-clocked from the original SMPTE/AES bit stream rate to a rate 4% lower. Again upon playback the 25-fps PAL reference is used and the playback then is in the correct pitch. (Nobody I know of makes a 24 fps PAL sync generator so the sync output of the VAS RTS HD 3:2 was used.)

The VAS Group products can be seen on their web site located at or phone (818) 843-4831.

D-1 outputs a serial bit stream and a PAL D/A converter must be used to decode the bitstream back into RGB or Y,Pb,Pr etc. The first A/D converter ran at 30 fps but there was no indication that it was an NTSC only Serial Digital to Analog device.

Finally, the projector liked what was on its inputs and displayed a beautiful 625 line x 702-pixel picture at 25 fps. The HDTV tape was input with full bandwidth RGB and then outputted as a standard CCIR-601, Y,Pb,Pr or RGB signals.

In this case the 2:35 scope images were letter boxed to fit within the 4:3 aspect ratio rather then resizing, panning, scanning or zooming in. The other two clips were 1.85 aspect/ratio movies. Except for the resolution, (PAL has a few more scan lines and slightly wider bandwidth), playback into a PAL broadcast monitor and the projector was very good and the client was happy!

The VAS RTC HD3:2 performs a variety of functions. For broadcast it will do real time transfer of any ATSC video source (1080i, 720p, 480p and more) to serial digital video CCIR-601. In postproduction you can create a HDTV master and easily down convert to either 625i or 525i with 3:2. You can also playback a 625i at 24 fps and convert to a 525i with 3:2. The box features a 3:2 framing and "A" frame control. It also has digital filtering for both horizontal and vertical axis as well as 64 filtering combinations for anti aliasing, flicker and moiré pattern removal.


It was very easy to down convert from HDTV to PAL and get rid of the 3:2 sequence with the VAS RTC HD 3:2 box.



Subj:  Secondary services may have problems

By:      Larry Bloomfield

      The following is a story I wrote for Broadcast Engineering.  It appeared in the April, '98 issue.  Because of the seriousness of this possibly happening again, it is reprinted with permission here:

      Operators of equipment that are considered as a "secondary service" on any frequency in the television broadcast band, Channels 2 through 69, may find that the frequency they are working on may have some powerful company.  With the introduction of the new digital television channels, these "secondary basis" authorizations will have a rude awakening if they are co-located with a new DTV channel assignment in their area when it signs on the air: such was the case in Dallas, Texas. 

In speaking with David Johnson, Capital Projects Coordinator and a member of the WFAA-TV's Engineering staff, he told me:  "On February 27th we signed on our new DTV transmitter for the very first time.  It operates on Channel 9.  We proceeded to do testing and everything looked good.  Our initial concern was co-channel interference with our NTSC station on Channel 8 and with the cable companies in and around Dallas.  There were no problems.  About 3 AM, Sunday morning  (March 1st), our news assignments desk got a call from Baylor University Medical Center (BUMC) saying that they had determined that our channel 9 transmitter was interfering with 12 of the their heart monitors.  We had already sign off the air at 10 PM the night before."   Beaven Els, WFAA-TV's Chief Engineer met with the A. Webb Roberts Hospital's officials at BUMC later on that same morning.  Johnson continued:  "We came to an agreement to stay off the air with our new DTV Channel 9 until they could resolve the problem."  In the meantime the WFAA-TV's engineering staff have worked with the BUMC administrators to resolve the problem and have tried to coordinate the same efforts with other hospitals in the area.

      Station operators who accept licenses that are designated to operate on a secondary basis must live with any signal levels they encounter from the primary service.  As the FCC R&R's say they:  "must not interfere with and must accept interference from current and future full-power stations" on these frequencies.  But the WFAA-TV's engineers couldn't ignore the life-threatening situation at the local hospital.

      In speaking with Jamie Ramo, Director of Public relations at Baylor University Medical Center, she said:  "We are buying and installing 30 new multi-frequency, wireless heart monitors, to avoid future interference."  It is my understanding that this will cost the hospital nearly $200,000.00.  Ramo said:  "We have a technology team that maintains all of the medical equipment here at our facility.  It was that team that discovered this particular issue.  As a solution, our technology team will be working with the FCC and the Dallas/Fort Worth Hospital Council to educate other medical facilities about such situations."

      If you want to be a good neighbor and avoid any of this kind of thing happening in your neck of the woods, it wouldn't hurt to interface with the local medical community as the folks at WFAA-TV and Baylor did.  It will go a long way in preventing any future situations from sneaking up and getting you or them when you least expect it.


This story is not over.  If anyone has any ideas on how we as an industry can go about preventing this kind of thing from happening in the future, anywhere, please contact me as I am working with several other organizations in an attempt to help resolve this issue.  Thanks  Larry



The DTV Tech Notes are published for broadcast professionals who are

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