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 future.
Digital Television, The
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 refresh rate.
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.
Aspect 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.
Summary of the 18
Digital Television formats, including 6 HDTV formats
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.
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
higher resolutions 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
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
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 information.
Just like analog TV, Digital Television and
HDTV can be delivered in one of four ways:
(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 Dish
Network and DirecTV
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 may also
need to upgrade your satellite set-top box 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
Network: To receive HDTV programming, look for the Model
6000U series HDTV broadcast satellite receiver and a dish
antenna pointed at 61.5 or 148 orbital locations.
To receive HDTV programming, look for the DirecTV
High-Definition Receiver 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 Vestigial 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
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.
What's 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”. Click
here to check if your local ABC-affiliated channel provides
over-the-air HDTV broadcasts.
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
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
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
HDTV broadcasts movies in HDTV and is available on the DirecTV
and Dish Network broadcast satellite systems.
HDTV 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:
Network 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.
Analog to Digital
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.
television signals would cease to be broadcasted over-the-air,
and everyone in the United States would watch Digital Television signals.
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 of displaying.
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.
(D-VHS). 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 ($1,600), Mitsubishi 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.
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
High Definition DVD. On the near horizon is the
introduction of the recordable 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.
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
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