Published by: Larry Bloomfield & Jim
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Note - 045
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Note: Jim Mendrala is at SMPTE
- New York. Look for his report
Fixing On Air digital Errors
Note: Ray is the
Transmitter Supervisor at KGO-TV, Channel 7 & KGO-DT, Channel 24,
(ABC) San Francisco, CA)
ran into a little problem that we didn't know we had with our on air DTV signal.
Gus Fernandez of TeraLogic did an analysis on our off air signal and
found that it had about 35 errors per minute.
digital signal path starts with our Harris/Lucent encoder.
From there we go to a Leitch Digibus interface, into a DS3 line and then
on to the transmitter site. At the transmitter site, it goes from the DS3, to
the Leitch interface and then to the exciter.
seems that the Leitch interface was changing some bits on some of the packets.
The Sencore analyzer says the Adaptation Field of the Null Field Packet header
was being changed to '00' instead of '01.'
This was causing a loss of some video packets: sometimes one, two or
three packets. Most receivers cannot correct for three lost packets and will
breakup. The new hardware from Leitch will be installed by the time this Tech
Note gets on the street. Leitch was
very concerned about this and was very responsive.
who is using a similar setup might like to know about this and check for errors.
For the most part, on air you can't see the result, but add to it, the
multipath problems with the present receivers, and you magnify the problem.
Hope this helps someone out. Your newsletter is an absolute gem, thanks.
Increasing Optical Media Densities
Kurt Hageman - KHageman@Trigaero.com
Note: Kurt is an engineer
well experienced in audio systems and a sometime inventor. His list of credits is numerous.)
as you know the DVD was made possible by the blue laser diode.
The smaller the wavelength of the light the closer we can pack the data.
A company, Nichia, in Japan has come out with a 370nm laser diode. Yes,
that is black light!! Now we will be able to pack data even tightly.
could even replace those large fluorescent blacklight tubes, left over from the
1960's, with a solid-state blacklight source.
Wow! It's a whole new way to look at blacklight posters. Anyway the 370nm
LED comes with an eye hazard warning. You cannot see the light. Unlike
fluorescent blacklights that have some visible spectrum emitted from the
phosphor, the LED is monochromatic, you cannot see if it is on and it can damage
your eye by looking at it.
predict that the next step in the evolution is most certainly in the short wave
ultraviolet range, i.e., UVB or UVC, black light is UVA. This will increase the
density of optical storage.
application of this technology and as a side note, when are they going to
increase the sampling rate on audio CD's? 44.1KHz
is not fast enough to properly reproduce the complex harmonics generated by
classical, jazz, and other music styles. All the sounds combine and produce very complex harmonics and
are not replicated by sampling at 44.1KHz. If we can get all the video
information on a DVD read with blue laser light why not improve the audio CD??
Look at it this way, the audio CD is in its original form: the same as the
Edison cylinder was the first form of groove recordings. I want to see the CD
process evolve up to where LP's were when CD's took over. I can hear the
differences between the CD version and the LP version of a particular piece of
music. The LP has a warmer more musical sound. Now we are talking about
classical and jazz here, not this #*&!% that is put out today, it would
sound just as bad no matter how you recorded it.
A "bit" concerning encoder comparisons.
Note: Jerry works for
most remarkable test was done this week (circa 11/16/99) at the Model Station
Technical meeting in Washington, DC. Amidst many demonstrations, a test was done
with the encoders loaned to the Model station. Five different encoders encoded the output bitstream of the
Sarnoff Digital Television Encoder Stress Patterns, with the decoded results
shown on monitors that were positioned in such a way, that it was easy to
compare the final results. NDS,
Tierman, Divicom, Mitsubishi and Thompson supplied the encoders.
After looking at the pictures for some time, it became very apparent to
me, that the Divicom encoder was the best encoder. It had far less artifacts
than any of the other encoders. The next best encoder was the NDS encoder.
(Ed Note: We have not
included the worst encoder) This
test and comparison was unique and will not likely happen again in the future.
Divicom was reported as having more MPEG experts than any other company
in the US. The Divicom encoder uses "LookAhead" technology for a more
constant bitrate and "ClearMotion" Integrated Noise Reduction.
again for your Newsletter.
Note: If the
next two stories aren't a wake up call to the cable industry to
do what is necessary to bring good, crisp pictures into subscribers
homes, they can begin the count down to their demise.
EchoStar plans Local Channels; Congress finished, finally!
CO -- Nov. 19, 1999--With final passage of satellite TV legislation, EchoStar
Communications Corporation will begin providing better competition to cable by
offering local ABC, CBS, NBC and FOX network channels to consumers.
24 hours of President Clinton signing the bill into law, EchoStar's DISH Network
will offer consumers in Atlanta, Boston, Chicago, Dallas/Ft. Worth, Miami, Los
Angeles, New York, Pittsburgh, Washington, DC, Denver, Phoenix, Salt Lake City
and San Francisco their local channels by satellite. Consumers across the
country living in areas where they are unable to receive a local off-air
will continue to be offered distant network signals. EchoStar also plans to
launch local channels by satellite to 30 total markets next year.
go to the broadcasters for a hard-fought victory in Congress," said Charlie
Ergen, CEO and chairman of EchoStar. "We're disappointed that the bill
didn't go further to protect the rights of consumers and does not allow
consumers the freedom of choice to watch the network channels they choose. The
legislation also should have done more to foster competition by creating better
equality between cable and satellite TV providers. With no statutory guarantee
of fair pricing, the best we can do is hope that the broadcasters will not
demand terms and prices from us that are higher than cable pays and that will
raise costs to our customers and keep us from competing effectively with
first approached Congress three years ago with the intent to protect the rights
of consumers and to seek competition to the rising rates and poor customer
service of cable television. "EchoStar
extends a heartfelt thanks to those in Congress who backed the fight for the
rights of millions of consumers and to the hundreds of thousands of consumers
and retailers across the nation who made phone calls and sent e-mails and
letters to Congress in support of a bill that offered a true alternative to
cable TV," Ergen added.
look forward to working with the broadcasters and Congress in 2000 to further
create effective competition to cable television and, in particular, to address
the needs of rural customers who seek popular
DIRECTV Applauds Passage of Satellite Home Viewer Act
SEGUNDO, Calif. -- Nov. 19, 1999--DIRECTV, Inc. today applauded Congress for
passing the "Satellite Home Viewer Improvement Act of 1999." The bill
permits improved competition between satellite carriers and cable operators.
The bill allows satellite TV companies -- for the first time -- to offer
local broadcast network channels, and it also provides a five-year reprieve to
hundreds of thousands of consumers who were scheduled to lose distant network
signals as the result of a federal court decision earlier this year.
passage of this legislation is a tremendous win for consumers and ushers in a
new era for satellite TV," said Eddy W. Hartenstein, president of DIRECTV.
"Every month, two-thirds of our new customers come to DIRECTV from cabled
areas, which underscores the need for enhanced competition in the home
entertainment industry. Upon President Clinton signing the bill into law, we
will begin offering local channels to major metropolitan markets throughout the
country -- finally leveling the playing field between satellite and cable."
previously announced, DIRECTV will offer local broadcast network channels via
satellite to up to 50 million homes, or about half of the nation's television
households. DIRECTV will begin rolling out local channels in Los Angeles and New
York within hours following the President's signature of the new law, and will
continue adding markets throughout the remainder of 1999 and in 2000.
In addition to Los Angeles and New York, the first markets to receive
this new local channel service include San Francisco, Washington, DC, Denver,
Detroit and Miami. Additional markets will be announced in the coming weeks as
the rollout continues.
customers will be able to subscribe to their local channel package -- which will
include a national PBS feed -- for $5.99 per month.
DIRECTV will deliver local broadcast network channels in approximately 20
markets from its satellites at 101 degrees West Longitude (WL), its primary
orbital slot. As a result, DIRECTV customers in those markets can receive their
local channels as well as DIRECTV's current lineup of national digital
entertainment and information programming through their existing digital set-top
box and 18-inch antenna.
will deliver local channels in additional cities from the 110 and 119-degree WL
orbital slots. Local channels delivered from the 110 and 119 degree WL orbital
slots will be received via the new DIRECTV Plus System, which features an 18-by
24-inch oval satellite dish. The DIRECTV Plus System also receives and
seamlessly integrates the existing lineup of popular networks, premium movie
selections and sports programming subscriptions from 101 degrees WL.
has approximately 7.8 million customers, including customers subscribing to
PRIMESTAR By DIRECTV. Visit DIRECTV on the World Wide Web at www.directv.com.
Mark Schubin's visit to NxtWave
Note: Since Mark was there
and saw first had, we asked his permission to reprint this from one of the
Internet lists we both subscribe to. We're
grateful for his kind permission.)
went to NxtWave on Friday afternoon. I was not asked to sign any nondisclosure
agreement. I visited their lab and the demo setup in CEO Matt Miller's office. I
also got to sit in on some discussions with
other guests who HAD signed NDAs, which eventually made NxtWave uncomfortable
(as it should have). I left NxtWave at my own pace; they didn't shoo me out.
The NxtWave equalizer is effective. In the lab, we adjusted to a condition of
"completely closed eye" pattern (actually, for 8-VSB it's eight lines
rather than an eye). For those of you who have seen demos
the Tektronix equalizer for SMPTE 259 built into the WFM 601 series of waveform
monitors, the effect was similar: without equalization mush, with equalization
eight distinct lines. NxtWave's goal is to be "best of class" (i.e.,
the best 8-VSB equalization). I do not have sufficient experience with all the
alternatives to say whether they have met that goal, but I would say that this
was the best 8-VSB demodulation I have yet seen.
It is not magic, however. The present algorithm could not always handle a zero
dB static echo (sometimes it could), for example. It also has some problems with
very close-in echoes. The NxtWave people believe that they know what needs to be
done to fix these problems and plan to do so in second-generation chips. There
is, however, a practical limit to how much can be done at a certain level of
power consumption and chip cost. The current package (100-contact plastic) draws
about 1.2 watts. NxtWave's
goal is for the chips to be able to live in PCMCIA cards. An increase in
equalization complexity that raised the power level to over two watts would mean
different packaging for heat removal. NxtWave,
has to weigh what is technically possible with what makes business sense.
There is no manual intervention required to handle different echo ensembles, nor
was any manual intervention used in the "real-world" demo other than
to change channels and orient the antenna.
The ability to handle dynamic multipath was demonstrated in the lab.
The appearance on the spectrum analyzer was that of a waving flag. The
other guests and I both noticed, however, that the effect of the
on the dynamic multipath was not constant. At one point in each cycle, which
appeared to be when the notch was in the vicinity of the pilot, the pattern
closed a little. There was clear correlation
the pattern closing and the frequency of the dynamic multipath, but I cannot say
for sure that it was at the pilot.
There IS a sensitivity reduction caused by the equalizer, but it's not a lot. I
saw demodulation at a C/N in the vicinity of 15 dB. With a ghost ensemble (I
personally viewed ensemble "A" being tested), the
was on the order of 1.0 to 1.5 dB (C/N around 16.5 dB).
NxtWave's specs submitted to the FCC claim the same reduction for
ensembles "A" through "G."
The field tests conducted by NxtWave (which I did NOT personally see) were
conducted under conditions similar to those used in the non-Sinclair testing:
van, 30-foot mast, log-periodic directional antenna on a rotator. The big
difference is that there was no MPEG decoder. They tested based on
"eye" (line) pattern. I believe that to be valid methodology (I also
believe Sinclair used valid methodology in its tests -- in both cases one could
argue about the equipment used and sites selected). You may wish to take this entire section with a grain of salt
because it's secondhand, but I think there's a very important point at the end
that is quasi-first hand. I'll concentrate on just the Philadelphia field tests.
There were seven sites: Sites 1-4 were NOT in center-city locations;
sites 5-7 were. Sites 1-4 were said to be successful on all four Philadelphia
DTV stations. That means that, with the antenna rotated for maximum signal
strength, a clear eight-line pattern was demodulated.
Sites 5-7, the inner-city sites, were NOT successful on all stations. It
is said that CBS was okay at all sites, ABC less so, and NBC and Fox not
receivable. That's in approximate descending order of transmitting-antenna
height and effective radiated power.
comes the quasi-first-hand stuff: NxtWave personnel described what they called a
"tunneling" effect at the bad sites, where a signal bounces back and
forth between buildings, creating a very long ghost.
discussed this at length and eventually got around to what it looked like on a
spectrum analyzer. We were at the demo setup at the time and had a spectrum
analyzer in front of us so we could point and gesture and say things like,
"It looked like that part, but maybe 10 dB peak-to-peak."
As a result, we came to the conclusion that what the NxtWave personnel
had seen at the inner-city sites where some DTV stations could not be received
very closely matched what I had seen once before. The place I had seen it was at
the high-rise, Inner Harbor apartment site at the Sinclair tests in Baltimore.
Take this for what it is worth. What is odd about it is that the NxtWave
personnel believe that problem to be caused by a very lengthy echo, which would
supposedly cause a problem for COFDM if it exceeded the guard-interval length.
Yet, there was clearly perfect and stable COFDM reception in the apartment; it
was the 8-VSB receivers that failed. I was there. The Sinclair personnel
couldn't understand why the 8-VSB had failed there, since there were no huge
nulls visible on the analyzer.
NxtWave plans to send a team to my apartment to record the DTV spectra and take
them back to the lab for testing. They say they will tell me:
a) whether they could demodulate the signals at all, and b) whether they
think they could be demodulated cost (and power) effectively. I like the idea of
the famous (infamous?) Schubin site. They also reminded me (DUH!) that, even
though I can't get DTV reception in my apartment with the receiver/decoder and
antennas available to me, I COULD see what the spectrum looks like. As soon as I
get a chance, I'll drag over an analyzer and have a look.
Now to the meat: The "real-world" demo. NxtWave is using a
thrown-together setup with different manufacturers for the different components
(tuner, SAW filters, MPEG decoder, etc.). The MPEG decoder was not always
working well (it appeared not to always refresh with I-frames), but I did not
have any difficulty distinguishing between a decoder problem and a demodulation
I decided to compare apples and apples. When we walked over to the demo setup,
an NTSC receiver was tuning in the CBS analog station in Philadelphia on rabbit
ears, and the NxtWave setup was getting the CBS digital via a directional UHF
antenna. The CBS analog looked awful. BUT
the CBS analog is VHF channel 3. I asked for an analog UHF near the CBS digital
(channel 26). We chose a Fox station (WTXF) on channel 29 and split the antenna
three ways (to the analog TV, to the DTV receiving apparatus, and to the
spectrum analyzer). The analog station came in superbly. I would rate the analog
picture quality as "very-good to excellent." NxtWave personnel
wandering by glanced at it and said, "Wow!
How'd the analog get so good?"
The strange antenna referred to in a previous posting about NxtWave is a Silver
Sensor "Antiference" indoor set-top yagi from the UK. It was possible
to use it to get not merely excellent analog reception but also perfectly stable
DTV reception that was not affected by our walking around the room behind the
antenna. The antenna DID have to be positioned, but that was pretty easy, and
NxtWave's chip offers a tap-energy output that can be used as a positioning
indicator (or for Charles Rhodes' crossed-dipole electronic-steering idea). The
antenna was about six feet above the floor on a stand.
We also tried a standard cheap UHF bow tie of the sort packed with every TV set
in the US (it was also one of the antennas used in the Sinclair testing). Its
positioning was more critical, but it, too, could be positioned so as to provide
absolutely stable DTV reception. There
was not "just one" position in the room for it. Perfectly stable
reception was possible from a height of only about four feet. The bow tie, too,
was not affected by our merely walking around the room behind the antenna, but,
with a metal chassis-grille plate, I COULD cause reception to fail at certain
points (looking at the spectrum analyzer, I could also IMPROVE reception, with
the plate acting as a back reflector).
Please note that, while we were able to make the DTV reception fail (by
misaligning the antenna or stalking it with the chassis plate), we never got the
ANALOG to fail completely. Channel 29 looked great.
we tested ABC's digital at channel 64 and NBC's at channel 67, we switched to an
analog Philadelphia station (WPSG - UPN) at 57. It wasn't as good as WTXF, but
it, too, was quite watchable when the DTV failed. We passed other, perfectly
good UHF signals between 29 and 57, too. It is clearly not the case that there
will always be DTV reception where there is analog reception.
also note: From NxtWave's offices, the Philadelphia stations (analog and
digital) are all essentially co-located. BUT, without moving the antenna, we
also got good reception on channel 58, an analog New Jersey Network (PBS)
station (WNJB) in New Brunswick, New Jersey, in the opposite direction (and
probably farther away). I'd say the
Philadelphia stations are some 25-30 miles from NxtWave. Based on my previously
driving and taking a train over a similar route, I'd say the terrain is
relatively flat (some low rolling hills). There IS a road outside the demo-room
window, but it is considerably lower (at no time was there any correlation
between road traffic and reception). There are trees, however, across the road,
which the signals probably have to pass through.
At no time when there was successful DTV reception at the NxtWave demo did the
spectrum analyzer display appear to be anything like what I saw in Baltimore.
There were no multiple deep notches or slopes.
while I could see myself affecting the spectrum display as I moved around the
room, I had to look carefully to see the effect. In Baltimore, at the 10 West
Lee Street site, we all felt we had to stop breathing lest we affect the test.
The slightest hand motion was clearly visible on the analyzer, and, again, we
were standing behind the antennas.
is not meant in any way as a criticism of NxtWave's demo.
They did not do anything to prevent my affecting the spectrum (although
the antenna was positioned closer to the window instead of farther from it).
It's just very clear that the sites were quite different. That's to be expected.
I saw inner-city sites in Baltimore; NxtWave's offices are suburban.
There WAS, however, a spectrum problem I noted at the NxtWave demo that I never
noticed in Baltimore: impulse noise. I might not have noticed it in Baltimore
because there I was looking only at DTV spectra. At NxtWave, when we were
looking at ANALOG spectra, little spikes would pop up here and there amid the
three NTSC peaks.
NxtWave has never called their chip a "miracle" and objects to that
characterization. I will cease to use it henceforth.
NxtWave personnel seem to feel that diversity reception would be necessary for
8-VSB mobile applications.
NxtWave has looked at a lot of DTV signals from a lot of stations. "Some of
the signals we've looked at give us concern about the consistency of VSB
encoders/modulators," said CEO Matt Miller.
NxtWave's chip works fine with QAM as well as VSB.
about it. If anyone has questions for me, I'll try to answer them (firstname.lastname@example.org).
You might also try Matt Miller (email@example.com).
E-cinema, may be not!
cinema is on the verge of climbing into bed with HDTV.
To let you know where I stand on this, keep in mind that today's NTSC
pictures delivered via digital satellite is comparable to super 8 mm film.
If that were the case, HDTV is then comparable to Super-16 mm film.
Since Electronic Cinema must measure up to 35 mm in it's worst case,
there is no way that this new burgeoning industry can or should ever settle for
glorified HDTV, irrespective of who is doing it or whose name is on it.
Don't get me wrong. There is
nothing wrong with HDTV, for the home, but put it on a theater screen and what
you see is what you get. Yuck! The numbers don't lie, irrespective of who says anything
no question that the HDTV performances (i.e. Star Trek and Toy Story II) that
are or have been given at various venue to date, using the HDTV equipment, has
look quite impressive. But why
should the electronic cinema industry settle for a skateboard when they should
be thinking aircraft? It's time for
the nontechnical types to get the hell out of the way, stop interfering with
their political BS and patronizing old cronyism and let the engineers, who know
what they are doing; get to the business of developing the standards and
technology worthy of Hollywood's glorious history.
whole business of letting the big manufacturers bamboozle this new industry into
using the relatively inferior products and not address where they have to go to
measure up, is absolutely ridiculous and stands against every ethical standard
any engineer of worth would subscribe to. It reminds me of a talk given by one of Thomson
consumer products VPs in Palo Alto, CA, about a year ago, when he stated that
his company's TV sets would be able to display up to one million pixels.
When asked why he was bragging about displaying only half the pixels the
broadcasters were transmitting, he neglected to address the issue.
for HDTV as the electronic cinema standard is comparable to that VP's line of
thinking. 35 mm film is a 4,096 by
2,214 pixel format (per the SMPTE Journal, Nov. 1999, page 753).
HDTV is 1080 by 1920 (per ATSC). You
do the math! Qualified Engineers, not people with high-priced corporate
titles, have always been the ones to get the job done.
It's time for the "suits" to sit down, shut up, and let the
people "in the know" do their jobs.
I trying to stir the pot? You had
better believe it! What to mussel
me? Hire me; I usually don't bite
the hand that feeds me! These are
my opinions, from my prospective: more on this later.
Note: The Editors and
Publishers of the Tech Notes wish to thank Des Chaskelson, Research Director of
SCRI International for his generosity in posting the Tech Notes on the SCRI web
Des Chaskelson, Research Director, SCRI International (firstname.lastname@example.org)
New Website with Industry Press Releases Plus New HDTV Survey
out the SCRI web site, where the Tech Notes are published, for some really great
information on industry trends and other very valuable marketing information,
trade news and current television events. SCRI
is currently in preparation of our latest survey, analyses and report.
Tech Notes are published for broadcast professionals, and others, who are
interested in DTV, HDTV, Electronic Cinema, etc., by Larry Bloomfield and Jim
Mendrala. We can be reached by
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