Published by: Larry Bloomfield & Jim Mendrala
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Tech Note - 019
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
of the Presentations include:
--Charles Poynton--Tutorial on the Viewing
Psychophysics of Advanced Television
& 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
Network/SMPTE Engineering VP--The plans of the Terrestrial Broadcaster--Find
out why ABC picked 720 Progressive.
Cable Labs--Hear Cable TV's plans for carrying or not carrying all
the Digital Signals at Full Resolution
High Definition Production for Direct TV--The plans of Direct TV
for HD to your home in the entire US this year
and Tours of the Advanced Television Exhibition
Techniques for Advanced Television
Production for 16 x 9 & 4 x 3 Display--
Production for Columbia TriStar--He will show Examples of Columbia
shows in HD Film Production in 16 mm and 35 mm
of the latest film stocks in HD will be displayed Electronic Production
--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
Manager--Warner Bros. Video Operations -- Telecine Transfer--Methods
Pacific Hollywood--(One of largest Episodic Post Operations in the
World) Episodic TV Post-Production
and Wilcox--Format Conversion --Examples and Working Hardware will
be shown--Down Conversion, Up Conversion and Aspect Ratio Conversion
will be shown
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
Production Company in the World--Gavin is sure to bring us all down
to earth with some of the practical financial and technical considerations
Consultant to Microsoft will discuss the integration of the new
video technologies with the Computer Industry
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
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
--Fujitsu: 42" Plasmavision Flat
--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
--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
--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
--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
Transfers displayed on identical monitors.....You Be The
More Displays will be added by Saturday:
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.
Bill Hogan, Sprocket Digital
Nelson Meacham, Walt Disney Imagineering
From: Mike Tinker
and Multimedia Applications
This is a late response, but I couldn't let
it go by. In Tech Note #17 you say:
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.
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."
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.
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?
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
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.
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 www.vasgroup.com
or phone (818) 843-4831.
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.
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
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
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.
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.
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."
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
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, but usually not.
--------- J_Mendrala@compuserve.com <<<
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