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High Definition Television (HDTV), if you have ever seen it, promises to dazzle even the most jaded home electronics fan.
The picture, as many would say, is like looking through a clear glass window. The high resolution digital picture is so detailed that many will forget they are looking at a television screen.
So what is HDTV? What is it all about? What are the basic facts that you must know?
In this tutorial, we cover the basics of HDTV and how it compares with
Digital Television (DTV) as a whole, what programs are available in HDTV, how you could view HDTV in your own
home and make recordings of HDTV programs, and what's in store in the near
Digital Television, The Formats
High Definition Television (HDTV) is actually a subset of the Digital Television
(DTV) family of formats, as defined by the Advanced Television Systems Committee
(ATSC). DTV uses digital data (1's and 0's) transmission of the picture and sound
information, as opposed of the traditional analog signals used for what we
know as analog television, devised by the National
Television System Committee (NTSC). The relatively new DTV picture formats are generally characterized by the
horizontal and vertical resolutions, aspect
ratio, interlaced or progressive scanning, and
Vertical and Horizontal Resolution.
How many pixels (picture elements) each dimension of the picture
holds. For example, 480 lines of vertical resolution means there
are 480 horizontal lines of information in the vertical axis.
Each horizontal line consists of 640 or 704 pixels lined up.
Ratio. The ratio of the picture's width to height is expressed as “width:height”.
For example, “4:3” aspect ratio means that the picture width is 4 units
wide by 3 units high. Another way to express this aspect ratio is “1.33:1”,
meaning it is 1.33 times wider than it is high. This traditional aspect
ratio is commonly called “full screen”, since it fills the traditional TV
screen. In contrast, “16:9” aspect ratio calls for a picture that is
16 units wide by 9 units high, or 1.78 times wider than it is high, or “1.78:1”
aspect ratio. This new aspect ratio used by some DTV formats, and by all
HDTV formats, is usually called “widescreen” or “16 x 9”. The
widescreen format is closer to the movie aspect ratios of 1.78:1 and
2.35:1. Widescreen aspect ratios take advantage of the physiological
fact that our eyes have wider horizontal field-of-view than in the vertical
direction. By filling more of our natural vision, directors and content
producers can better draw us into the action. That's why movie screen
have gone to the 1.78:1 and 2.35:1 aspect ratios decades ago. It's a
more visually involving experience.
Interlaced or Progressive Scanning. The
television picture can be “drawn” in one of two ways.
Traditionally, the picture is drawn with two passes, one for the
odd-numbered horizontal lines (first frame update), and another for the
even-numbered horizontal lines (second frame update). So it takes
two passes (or two frame updates) to refresh the entire picture.
This is called interlaced scanning. An analog TV picture
is completely refreshed about 30 times a second (or 30 Hz). To
put it another way, the entire picture is redrawn 30 times every
second, with the odd- and even-numbered lines redraw cycle repeated 30
times per second. Some of the new DTV formats call
for progressive scanning, where the entire picture (both
odd-numbered and even-numbered horizontal lines) is updated in a
single pass or scan. Progressive scanning results in a brighter
image with no visible TV scan lines and fewer motion artifacts (the
stair-step edges that you see on moving objects). Progressive
scan correlates better with the film medium, where the entire film
cell is protected onto the screen one cell at a time.
Refresh Rate. This is the rate at
which the entire picture is redrawn, expressed in number of times per second
(or Hz, short for Hertz). DTV supports interlaced scanning at 30 Hz and progressive scanning at 24, 30, and 60 Hz. The 24 Hz
refresh rate corresponds nicely with film projection's 24 frames
per second (fps) rate.
The table below summarizes all
18 of the ATSC Digital Television
formats. There are a total of six (6) HDTV formats, of which
720p/30 and 1080i/30 are the most common. Again, It is important to realize that HDTV is only a subset of the
DTV standards, and so DTV is the more general term, while HDTV specifically
references the six high definition formats of the 18 DTV formats. The
DTV formats are most frequently referred by their horizontal lines of resolution and whether they
scan in progressive or interlace (e.g., 480p, 720p, 1080i). The suffix “p”
stands for progressive scan, while the suffix “i” stands for interlaced
scan. Sometimes, they are further distinguished by their refresh rate,
as designated with a slash (“/”), followed by the refresh rate. For
example, “1080i/30” refers to 1080 horizontal lines of resolution with
interlaced scanning at 30 Hz refresh rate.
of the 18 Digital Television formats, including 6
Standard Definition Television (SDTV) consists of the first
DTV format of 480i/30. It is equivalent to interlaced video output of DVD-Video
in 4:3 aspect ratio. This format is used for when bandwidth is a bigger consideration than absolute picture quality.
SDTV uses a data rate of about 4-7 Mbps, so three to six SDTV channels can be crammed into the same
bandwidth as a HDTV channel.
Enhanced Definition Television
(EDTV) is a step up from SDTV,
but not quite as good as HDTV. EDTV consists of some 11 formats as shown
in the above table. The vertical resolution is limited to 480 lines, but
horizontal resolution varies 640 to 704 vertical lines. It encompasses
both 4:3 and 16:9 aspect ratios, a number of refresh rates, and both
interlaced and progressive scanning. EDTV is used when better picture
quality is desired, but without the full bandwidth of HDTV.
Definition Television (HDTV) uses a data rate of 25 - 27 Mbps for the
best possible picture. All HDTV formats are in 16:9 aspect ratio.
The 720 vertical resolution only uses progressive scanning, but at various
refresh rates. The highest resolution is commonly used in interlaced
scanning mode (1080i), due to limitations of current broadcast and consumer
equipment. But the format includes 1080p, to accommodate future growth
as imaging and display technologies catches up. HDTV is used for premium
programming when picture quality is of utmost priority, and bandwidth is less
of a concern. This includes select prime time shows, major sporting
events, and premium movies.
At its highest resolution, HDTV offers
2,116,800 pixels (picture elements). This is over a six-fold improvement
in picture detail of standard definition television which only has 307,200
pixels. Color resolution is also improved by a factor of two. All of the DTV formats use
MPEG-2 as the video compression standard, just like DVD-Video. MPEG-2
is a flexible video encoding algorithm and scales up nicely for the
of DTV. With digital transmission, there are no analog
transmission artifacts and degradations such as snow due to weak signal,
double images or ghosting due to multi-path interference of large buildings
and structures, and sparkles due to noise from a vacuum cleaner.
The Audio Format
Not only does DTV bring us a near-perfect picture, but included in the DTV formats
is digital audio as well.
Dolby Digital is the standard
digital audio encoding format for all DTV formats. Many of you know Dolby Digital for its
multi-channel surround sound capability from DVD-Video.
What some of you may not realize is that Dolby Digital is more flexible than just a 5.1-channel
surround sound format.
Dolby Digital is actually a scalable digital audio encoding algorithm that supports 1.0-channel (mono) and 2.0-channel (stereo,
with optional Dolby Pro-Logic/Pro-Logic II) when the original programming only has a mono or stereo soundtrack.
Dolby Digital only uses as much data as it needs to encode these
1.0-channel and 2.0-channel audio soundtracks.
Home theater fans will realize of course that Dolby Digital can scale up to “6.1”
extended surround sound as in
Dolby Digital EX. If you are not familiar with surround sound, be sure to read our
Surround Sound Tutorial and
Home Theater Receiver Buying Guide for more
Just like analog TV, Digital Television and HDTV can be delivered in one of four ways:
Over-the-Air (OTA) Broadcasts. Many local broadcasters in large cities and metropolitan areas have
already started broadcasting
Digital Television and HDTV over the airwaves. Yes, this is old rabbit-ear
indoor antenna (and unsightly roof-top outdoor antenna) approach to receiving
television signals. What you will need is an roof-top HDTV antenna (if your neighborhood
and city code allow for it) or an indoor HDTV antenna to pull in these signals.
You will also need an integrated DTV (with a DTV receiver built-in) or a DTV receiver and
a DTV monitor (also known as “DTV-ready television”). Alternatively,
you can use an DTV receiver and your existing analog TV, but you won’t be able to see
DTV and HDTV in its native high resolution formats. In this case, the
DTV receiver will down-convert the high resolution DTV signal, scaling it down to a lower resolution that your analog TV can handle.
You will get the clear, noise-free digital picture benefits of DTV
programming, but you won't see the much-improved high resolution picture due
to limitations of your existing analog TV. (This in fact fact how many
consumers will transition to DTV when analog TV
broadcasting stops. More on this later.)
Fact: More than
861 stations offer over-the-air
DTV broadcasts, and 60 percent of Americans are in areas where there at least five stations
broadcasting in D TV, as of May 2003.
Satellite. Broadcast satellite providers such as DirecTV
and Dish Network
were relatively quick to provide HDTV channels.
If you already have broadcast satellite equipment, you may still need to upgrade your satellite dish to a dual-LNB model (so it can receive from both the HDTV satellite and the “regular service” satellite.
You will also need to upgrade your satellite set-top box to a new
receiver or Dish Network receiver so that
it can decode the high resolution HDTV signals. Check with your satellite service provider for the specifics.
(Note that “digital satellite TV” is not the same as DTV. It
is simply the NTSC analog TV signals, transmitted in digital form via
satellite, then converted back to analog TV signal for display on your
TV set. These “digital satellite TV” signals do not provide
any of the true 18 DTV formats, as explained
To receive HDTV programming, look for the Model 6000U series HDTV
broadcast satellite receiver and a dish antenna pointed at 61.5 or 148
To receive HDTV programming, look for the
and a 18"x24"
DirecTV Multi-Satellite dish antenna with a Sat-C kit or an 18"x20"
DirecTV Multi-Satellite dish antenna (Triple-LNB).
Cable. For some time, cable TV companies were reluctant to upgrade their infrastructure to provide HDTV.
In response to the Federal Communications Commission’s (FCC) strong urging, some terrestrial cable TV provides (e.g., Time
Warner Cable) have begun to roll out HDTV channels. With cable TV delivery, you
may need a different set-top box, a “QAM-capable” DTV cable
receiver, to decode the DTV signals. (QAM stands for Quadrature
Amplitude Modulation. Simply put, this is the modulation used to
transmit DTV via cable TV. It differs from the 8-VSB modulation
used in over-the-air broadcasts of DTV. 8-VSB stands for 8-level
Sideband.) Some of the newer integrated DTVs incorporate
a built-in “QAM-capable” DTV decoder for terrestrial cable, in addition to
the 8-VSB DTV decoder for over-the-air reception. The early integrated
DTVs only have the latter for over-the-air reception of DTV, and require an
additional set-top box for decoding cable delivered DTV programming. Check with your local cable TV
provider to see if and when DTV programming will be available. (Note
that “digital cable” is not the same as DTV. It is simply the NTSC
analog TV signals, transmitted in digital form via upgrade cable equipment,
then converted back to analog TV signal for display on your TV set.
These “digital cable” signals do not provide any of the true 18 DTV
formats, as explained above.)
Media. Today, you can view pre-recorded HDTV movies in 1080i
on Digital-VHS video tapes using
the D-Theater copy
protection feature. So far, only DreamWorks, Fox, Universal, and Artisan
have embraced this format and released a handful of movies in D-Theater.
Read more about this in Digital-VHS and D-Theater Overview.
on HDTV? A Question of Content
So what programming is available on DTV, and particularly in
HDTV? After all, “content is king” is the mantra of the broadcasting world.
Though many networks are national, the availability of these HDTV networks
depends a lot on where you live. Here is the information we have
compiled. Click on the web links for additional information (links open
in a new web browser window).
Major national broadcasting networks:
is the only network to broadcast HDTV in the 720p format. ABC HDTV
programming include prime time shows such as “Alias”, “The Practice”, “NYPD
Blue”, “My Wife and Kids”, “MD's”, and “The Drew Carey Show”,
as well as network world-premiere movies such as “Gladiator”, “Charlie's
Angels”, “The Green Mile”, and “E.T. The Extra-Terrestrial”.
to check if your local ABC-affiliated channel provides over-the-air
feature HDTV broadcasts in 1080i for most of its prime time program, including
shows such as “CSI: Crime Scene Investigation”, “CSI: Miami”, “JAG”, “The
Guardian”, “Everybody Loves Raymond”, “The King
of Queens”, and “Touched by an Angel”. CBS also offers HDTV
broadcast for major sporting events such as the NCAA Playoffs and even
a day-time soap opera “The Young and the Restless”. Click
here to check if your local CBS-affiliated channel is currently
broadcasting HDTV over-the-air.
also broadcasts HDTV in the 1080i format. Prime time shows such as “ER”, “Frasier”, “Law
& Order”, “Law & Order: Criminal Intent”, “Law &
Order: Special Victims Unit”, “The Tonight Show with Jay Leno”, “In-Laws”,
“Hidden Hills”, and occasionally feature films and made-for-TV
movies are broadcasted in HDTV. Click
here to check if your local NBC-affiliated channel is currently
broadcasting HDTV over-the-air.
DTV in what they call “Fox Widescreen High Resolution TV”.
As if terminology wasn't difficult enough in today's world, Fox
actually broadcast in one of the EDTV formats,
specifically the 480 x 704 in progressive scan 16:9 widescreen format
(480p/30, see format #11 in the table
above). The picture quality is comparable to a “enhanced
for 16:9 widescreen TV” DVD-Video in progressive scan mode, but not
quite as good as HDTV. Fox DTV programming includes shows such as “Ally
McBeal” and “Dark Angel”.
broadcasts in HDTV and “Widescreen Standard Definition” (similar to
Fox's 480p/30, format #11). Its programming
includes specials and series such as “Nova”, “National Geographic
Special”, “Nature”, “Smart Travel”, and “Great Performances”.
PBS also broadcasts an HDTV demo loop.
For a complete
listing of of local TV stations broadcasting in HDTV, click
Major national premium networks
(available from cable or broadcast satellite providers):
is the premiere premium network specializing in 1080i HDTV programming, as its name
implies. This premium channel is included for DirecTV subscribers.
HDNet features live sports such as NHL, USOC, CART auto racing,
college and pro basketball, football, tennis, boxing, and horse
racing. It even features world news with its HDNet World Report
programming. HDNet Movies is another channel, providing
movies in HDTV from Warner Bros. and independent studios, as well as
made-for-TV movies and short features.
HDTV broadcasts movies in HDTV and is available on the DirecTV and Dish Network
broadcast satellite systems.
broadcasts movies in HDTV and is available on the DirecTV and Dish Network broadcast satellite systems.
HD Theater offers select Discover Channel program in HDTV.
This channel is available on the Dish Network.
Major satellite providers with
premium/optional HDTV channels:
offers the following channels in HDTV: Discovery HD Theater, HBO HDTV,
Showtime HDTV and CBS HD.
offers the following channels in high definition: HDNet,
HBO HDTV, Showtime HDTV, and a High Definition Pay-Per-View channel. To
sign up for HDTV on DirecTV,
Analog to Digital Television
When the Federal Communications Commission (FCC) auctioned the airwaves that would serve as
Digital Television broadcasts back in the mid-1990s, the goal was for the United States to “fully” transition to new
ATSC DTV standard by the year 2006. At such a time, Congress would take back the airwaves originally allocated to
NTSC analog television and re-allocate it for other purposes.
(Not everyone is aware of this fact.) Analog television signals would cease to be broadcasted over-the-air, and everyone in the United States would watch
Digital Television signals.
Analog television signals would cease to
be broadcasted over-the-air,
and everyone in the United States would watch Digital Television
To make the huge
number of existing analog televisions forward compatible with the DTV signals, manufacturers would make set-top boxes (STB), much like the set-top boxes that you may have today from your cable TV or satellite TV provider, that
down-convert the DTV signal to an analog television signal so you would be able to
drive your existing analog TVs with a signal that it is able to display.
The down-conversion process takes the higher resolution picture of DTV signals
and re-formats it to a lower resolution picture that analog TV sets is capable
Well, it's already 2003 and the
DTV transition has been rather slow to date. Only a few percent of all
U.S. households have DTVs or DTV-ready displays. The problem is similar
to that of the chicken and the egg. The chicken being DTVs and the egg
being DTV programming. (Or is it the other way around?) Without
DTV programming, why would consumers want to upgrade to the more expensive
DTVs or DTV-ready displays? From the content producers and broadcasters’
perspective, why would they upgrade their production equipment to DTV when
there are not enough consumers with DTV capability to justify the investment?
Given the more realistic (read “slower than expected”) rate of
DTV rollout by content producers, broadcasters, and distributors, and the adoption rate by everyday consumers, this 2006 “deadline” would
have to be extended. The U.S. Congress provision calls for the transition to occur when 85% of the United States population has
Digital Television. So don’t worry. Your analog TVs are safe from
obsolescence for quite a few years.
Digital TV & HDTV
Naturally, with DTV content available, everyday consumers will want to record such programs whether it be for time shifting, sharing programs, or archival purposes.
But recording DTV is one of the sticking points of this new technology. Since
DTV, particularly HDTV, contains very high picture quality and its digital
form theoretically allows bit-for-bit perfect copies to be made, content owners are leery of allowing their
precious, revenue-generating content to be recorded. Most of this is understandable, considering they
are the rightful owners. But for sometimes, their resistance may be
viewed as just paranoia. As a result, there is ongoing debate as to whether consumers should be able to record certain
DTV programs in light of the Fair Use Act.
Whatever the case, recording
DTV does have some technical challenges. First, the data rate for HDTV peaks at some 28 Mbps, about four to seven times that
of the DVD-Video format. So whatever recording medium is used, it must accommodate a
fast data rate. And since many movies and sporting events are a couple of hours long in duration, the recording
medium must also have a large data capacity, on the order of 25 - 50 GB.
Right now, there are
three hypothetical ways in which consumers may be able to record HDTV programs.
Digital-VHS is the only format available today, while high
definition personal video recorders and recordable high
definition DVD are expected to be available soon.
JVC took its aging VHS and Super-VHS formats and gave it new life as a video
tape-based DTV recording medium. The Digital-VHS format is capable of
recording HDTV in either 1080i or 720p, for up to four hours on a single D-VHS video tape.
This recording capability is available now. There are four D-VHS VCRs
available, including the JVC HM-DH30000 ($600, as low as $549.88
at JandR.com), Marantz MV8300
HS-HD1100U, and Mitsubishi
HS-HD2000U. For playback of high definition movies, JVC
also added a proprietary copy protection feature called D-Theater,
allowing movie studios to release movies in full HDTV quality without fear
of it being pirated. So far DreamWorks, Fox, Universal, and Artisan have
embraced the D-Theater format and have begun releasing a handful of movies to
this format. For more information about Digital-VHS and D-Theater, read
our Digital-VHS and D-Theater Overview.
High Definition Personal Video Recorders (HD-PVRs). Hard
disk-based personal video recorders such as TiVo and ReplayTV have
revolutionized the way consumers time shift TV. And soon, by the end
of 2003 or early 2004, HD-PVRs capable of recording HDTV programming may
become available. These devices are likely to be integrated with the
set-top broadcast satellite receivers or cable boxes and come with large
hard disk capacities, in order to capture the high bandwidth of HDTV
programming. Current and previous generations of PVRs are designed
for analog TV, and cannot record DTV and HDTV broadcasts.
Recordable High Definition DVD. On the near horizon is the introduction of
High Definition DVD (HD DVD) format. This new optical disc format would use the new blue-violet laser
technology to allow more data to be recorded on the familiar 12.0-cm optical
disc form factor. Two formats are being considered, Blu-Ray
Disc and Advance Optical Disc
(AOD). The Blu-Ray Disc format seems to have a leg up on the AOD format,
as Sony just released a production Sony BDZ-S77 Blu-Ray Disc Recorder
(equivalent $3800 US, available since April 2003) to the Japanese consumer
market. For more information about these HD DVD formats, read our High
Definition DVD Tutorial.
Future of Digital TV & HDTV
DTVs and DTV-ready displays will undoubtedly get cheaper and better with time.
More and more sets will incorporate a built-in DTV receiver. And hopefully with more
DTV programming comes more DTV adopters. As we discussed above, HD
DVD recorders are only a few years years away, providing the convenience of an optical disc format.
HD-PVRs based on today's TiVo and ReplayTV devices will probably converge with
the new HD DVD recordable format and allow us to archive HDTV quality programming onto removable and shareable
HD DVDs. Years from now, our children will ask us how we ever got along without
Digital Television. Until then, we’ll help you navigate the road
ahead and avoid the pitfalls of an evolving technology.
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