HDTV - The Future of Television
After years of debate and revision, new DTV broadcast standards are in place.
Television stations in most strategic major cities are now broadcasting DTV,
with the remaining stations planning to convert by the year 2004 - or die.
It is with mixed blessings that I witness the evolution of the single largest change in television
broadcasting to occur in over 50 years - Digital Television. DTV, or HDTV, is a total redefinition
of broadcast television as we know it today. With promises of better picture quality and more
diversified programming choice, DTV rolls out in major cities to a cautious consumer market.
Analog - A Technical History
Television signals broadcast worldwide for the last half century have been analog in nature, with
the video being amplitude modulated, and the audio being frequency modulated. These methods
of combining sound, picture and signal carrier are better known to most people as AM and FM.
The U.S. utilizes a format known as NTSC, while Europe and others use either PAL or SECAM.
Differences in these standards primarily relate to differences in established AC power distribution
line frequencies. Power line frequencies in most of Europe are 50Hz, while in the United States
they are 60Hz, which corresponds to their respective 50Hz and 60Hz vertical field rates. Your TV
displays a picture using a method called interlacing which actually paints 2 half-screen pictures,
called fields, onto your TV screen to make up each complete picture, called a frame. Therefore,
an NTSC signal consists of 30 frames with 60 fields per second, while PAL and SECAM signals
are comprised of 25 frames with 50 fields. As a point of reference, most standard movie film runs
at 24 frames per second (FPS), and has no fields. The frames of a video signal are not actually
interlaced with two field images from the same time slice, but are actually two distinct images
captured at the field rate. In other words, each full frame is made up of alternating lines of 2 fields,
with each field consisting of an image captured at twice the frame rate. So what you seen on the
screen at any given moment is actually a combination of two sequential times slices. The human
eye and brain blends what sounds like a mishmash of blurry imagery into the relatively smooth
imagery and motion you call modern TV. To further complicate matters, your TV is actually only
displaying a tiny dot at any given time, it is the persistence of the phosphors in the picture tube
which make the picture appear complete. This is why your TV screen may seem to glow slightly
when the room lights are extinguished. Whew - What a complicated set of interdependencies!
But due to what I call the Analog Smoozing effect, which is inherent in the nature of physics and
analog signals, it all works quite well, and was quite ingenious in 1945. All electronic equipment
exhibits a background noise floor, a DIN if you will, that limits it's Dynamic Range. Dynamic range
is the greatest discernible difference between the loudest (audio) or brightest (video) levels of a
signal, and the softest or dimmest levels. Analog Smoozing is the natural tendency of an analog
signal to degrade gracefully as the signal source deteriorates, and to retain most important content
until the signal simply vanishes into the DIN. Analog signals are natural and simple to implement.
Ch, ch, ch, changes...
DTV on the other hand, is not analog in nature, but digital. The term DTV relates to the overall
specification, which consists of HDTV (High Definition TV) and SDTV (Standard Definition TV)
formats. The FCC will permit broadcasters to choose any format. Although DTV still utilizes an
RF carrier for broadcast, it's content signals are a nightmare of applied computer algorithms.
MPEG-2 compression is utilized to simulate the Analog Smoozing effect, so that the extremely
high bandwidth video signals are compressed into more manageable rates - resulting in a number
of artifacts that the eyes and brain find far more objectionable than analog degradation. Although
the dynamic range of digital signals can be greater than with ordinary analog, detail levels shift
dramatically with changes in scene content - more motion, less detail. The digital DSS satellite
signals I have studied have contained an amazing variety of artifacts, many of which are quite
amusing and completely impossible to obtain with an analog signal. These include the ability to
see through solid objects, banding or paletteization of color information, and wildly vacillating
detail levels. Even though colors are stark, and contrast levels are high, I find the overall picture
quality somewhat disturbing. When displaying still images, the picture is breathtaking, but when
rapid motion exists in the scene, it's a mess. Apparently, the Grand Alliance, which is comprised
of several remarkably avaricious companies, believes the public will readily embrace changes in
picture quality and viewing expectations - After all, it's new and improved, Right?
The ring leader of this pack of greed mongers is Zenith Radio Corp., a pathetic remnant of what
was once a company known for quality and innovation. As the first Amerikan vendor of televisions
to move their manufacturing facilities to Mexico, and to additionally saddle their loyal customers
with the necessity of repairing their sets with poorly remanufactured boards, also from Mexico, a
special place in Hell has been reserved just for them. Until the late 1980's, there was company
in Benton Harbor, Michigan called Heathkit, which had been selling electronic kits to hobbyists
for almost 30 years. Early in the computer years, Heathkit designed and sold a computer known
as the H-89, which became quite popular with both hobbyists and business. Not wanting to miss
out on the lucrative profits to be made selling computers to the government, Zenith purchased the
Heathkit company in order to obtain the H-89 computer system. Shortly thereafter, the Heathkit
company was dismantled, depriving future generations of budding electronics experimenters and
hobbyists from ever knowing the satisfaction of 'building it themselves'. Whether Heathkit would
have survived the volatile marketplace of the 80's without Zenith's interference will never be known,
but I would have liked to have seen them survive. The kits and manuals produced by this small
company set the standards in clarity and thoroughness. The products they sold performed well,
were a good value, and included a broad spectrum of devices. Weatherstations, intrusion alarms,
computers, stereo gear, radio transceivers, and electronic test equipment were just some of the
items offered. Anyone over the age of 30 has probably heard of Heathkit. But I digress...
Turn and face the strain...
Like it or not, HDTV is the 'next big thing'. The U.S. Government has set into motion a plan which
will deallocate the current LO-VHF band from the TV spectrum and turn it over to the 'personal device'
communications industry. Cell phones and personal information appliances will probably be the
recipients of this spectrum. All TV broadcasting will then occur in the current HI-VHF and UHF range,
in digital format. What this means is that for the first time in history, your current television will not
receive and display the TV signals broadcast by your local station. You are required to purchase
either a new receiver or a converter box. Since current screens are fixed at 4:3 aspect ratio, any
broadcasts that are in Wide Aspect Ratio mode (16:9) will be letterboxed on a standard set. Sets
that display 16:9 programming have been slow in coming to the market, probably because of tepid
consumer interest, although video laser disc players in letterbox mode (not DVD) prompted a few
manufacturers to test the waters of wide-displays years before the acceptance of HDTV standards.
Time may change me...
So what does all this talk of aspect ratios and formats and resolution mean? Here is a chart that
attempts to define the different modes available under the Grand Alliance's HDTV specification.
|
Aspect Ratio
|
Horizontal Lines
|
Vertical Lines
|
Scan Rate
|
Progressive or
Interlaced |
|
HDTV
|
||||
|
16:9
|
1920
|
1080
|
60
|
I
|
|
16:9
|
1920
|
1080
|
30
|
P
|
|
16:9
|
1920
|
1080
|
24
|
P
|
|
16:9
|
1280
|
720
|
60
|
I
|
|
16:9
|
1280
|
720
|
30
|
P
|
|
16:9
|
1280
|
720
|
24
|
P
|
|
SDTV
|
||||
|
16:9
|
704
|
480
|
60
|
P & I
|
|
16:9
|
704
|
480
|
30
|
P
|
|
16:9
|
704
|
480
|
24
|
P
|
|
4:3
|
640
|
480
|
60
|
P & I
|
|
4:3
|
640
|
480
|
30
|
P
|
|
4:3
|
640
|
480
|
24
|
P
|
Broadcasters have expressed differing interests in these formats, and each one may eventually
choose to concentrate on formats which differ from their neighbors. In fact, there seems to be
ample evidence that even more formats may appear in the future as things get hashed about in
the marketplace. This will probably lead to incompatibilities with the software of existing sets,
necessitating the upgrading of software in your TV via FLASH EEPROM's or actual hardware
replacement in order to remain fully functional. Oh, shit - here we go again, upgrade Hell!
But I can't change time.
It's the PC revolution all over again, only this time it's occurring in your TV. One can only hope
that the blue screen of death syndrome doesn't migrate into the entertainment world, but my
exposure to early HDTV broadcasts in Atlanta, have not been reassuring on this point. Frozen,
stuttering video, choppy audio, and complete lapses in programming content have been frequent,
and sets which are designed to receive the broadcasts are, at this time, outrageously expensive.
Early adopters of HDTV do not understand the bizarre artifacts that they see, which has brought
forth a deluge of complaints and returned products. Additionally, repair of these products will be
nightmarish, as manufacturers are already having difficulty keeping up with the brisk demand for
replacement boards, which are generally not repairable, and are not even out of warranty. Unlike
your average PC, there is no standardized motherboard in these sets, and supplies of proprietary
(read: expensive) replacement boards will most likely be depleted very quickly as these sets die
an early death from poor quality design, workmanship, and lack of support for upgrades.
What to Expect from Your New HDTV Receiver
Vendors have no intention of supporting or upgrading products once sold and out of warranty,
and if they have promised to do so, they (or the salesman) are lying. This is the result of VCR's
being sold for $90, and TV's for $159. It's that 3rd world manufacturing problem again - everyone
wants it now, and they want it cheap. No matter that it may last 6 months, and be unworthy of
repair at the end of it's pathetic pre-planned life span - just throw it in the landfill and line up to
buy another when it dies. That's what keeps the money flowing into the hands of the brokers and
importers. Sony has proven repeatedly, that if you build something unique or of high quality, no
one here will buy it, because of it's slightly higher cost. Even they have seen the light, and have
thrown in the towel, producing plastic VCR's and selling Funai Combo TV/VCRs as their own.
Mitsubishi, who once built one of the finest sets one the market under the MGA moniker, has
deteriorated into a purveyor of high-failure, pre-planned life-span garbage. They sell televisions
as their own which are actually manufactured by Sharp, and VCR's containing plastic parts which
are decomposing on loading docks and in warehouses before even being sold, while their premiere
products are failing because of dozens to hundreds of small electrolytic capacitors which leak acid
onto the printed circuit boards. Repairing this mess is not something many shops want to do, and
most are simply closing their doors and giving up. The cost of test equipment, inventory, and the
prevailing trend for manufacturers to gouge servicers with outrageous prices on schematic diagrams
and parts, has reduced profits to the point that many are working for near minimum wage or simply
quitting. Add to this scenario a customer base that doesn't understand why their father's TV lasted
16 years, but the new imported-wonder-wiz-plastic-crappo-$159-special broke after 2, and it's easy
to understand why consumer electronics servicing is a dying business. The manufacturers rarely
hear about their failed product a year and a half after the sale, but the local Joe who used to make
a living fixing equipment generally gets an earful of how it must be his fault that the crap isn't worth
fixing, or that the parts cost more than the set cost when new, or that it will take more than 8 hours
to replace all the bad components, and the corresponding labor exceeds the value of the set. Joe
lives in this country, not Korea or China or Malaysia , and has to pay U.S. prices for housing, food,
cars, and insurance just as his neighbors do. He cannot compete with assembly lines full of foreign
machinery and 50 cent an hour workers. So enjoy that new DTV receiver while it lasts.
(With apologies to David Bowie)