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| DTV: Digital Television |
Countdown to DTV Transition:
February 17, 2009 |
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| DTV is a new type of broadcasting technology
that will transform television. Because DTV is
delivered digitally, the television signal is virtually
free of interference. And because DTV is more
efficient than analog, broadcasters are able to
offer television with movie-quality pictures and
surround sound. Ultimately, DTV will replace
today’s analog television broadcasting system. |
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DTV Why Now?
In the late 1990s, Congress determined that broadcast stations must transition from analog
television broadcasting to digital television broadcasting. Converting to DTV will free up
parts (“bands”) of the scarce and valuable broadcast spectrum, allowing these bands to be
used for public safety and emergency services and new wireless services. Because public
safety and emergency services have become even more important today, Congress recently
established a “hard” DTV transition deadline that requires all full-power television stations to
cease analog broadcasts after February 17, 2009. (The deadline for low power television
and translator stations will be established at a future date.) Until then, most television
stations will continue broadcasting on both their digital and analog channels. Already today,
more than 1,500 television stations servicing markets throughout the United States are
delivering television programming in digital format. |
DTV Programming
Digital television offers many advantages over analog television for viewing broadcast
signals. DTV is more versatile and efficient than analog television and allows stations to
broadcast more programming using less spectrum. In the same bandwidth that a
broadcaster currently provides one analog channel, a broadcaster may provide a super
sharp “high definition” (HD) program or multiple “standard definition” DTV programs
simultaneously. Providing several program streams in one broadcast signal is called
“multicasting.” A broadcaster also can use its DTV signal to provide video and data services
that are not possible with analog technology.
Television stations serving every market in the United States are currently delivering digital
television programming. For a list of available digital programming, visit
http://www.dtv.gov/partners.html. |
DTV and Your Analog TV
Today, most people have
analog televisions. Analog TVs have been used since the
beginning of television to receive and display
programming. Your analog television will work
as it does today until the transition to digital is
completed. Even then, you will be able to
continue using your analog television. |
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Analog televisions will work with a digital television
set-top box.
If you receive TV programming over the air, you will be able to purchase a set-top box
(sometimes referred to as a digital-to-analog converter box) to enable your analog TV to
continue working after February 17, 2009. Beginning in 2008, your household may be
able to receive up to two coupons worth $40 each toward the purchase of set-top boxes.
The National Telecommunications and Information Administration (NTIA) has
responsibility for administering the coupon program, and will issue rules regarding the
coupons in the future. Additional information can be found at http://www.ntia.doc.gov/.
If you are a cable or satellite customer, you may need a set-top box to receive DTV
signals and convert them into the format of your current analog television, even after the
DTV transition is complete. A DTV set-top box also may receive multicast channels and
high definition programming and display them in analog picture quality. Check with your
cable or satellite provider to determine if and when you will need a set-top box. |
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DTV uses the same antennas as analog TV.
If you already have a good VHF and UHF antenna, either indoors or
on your roof, you don’t have to buy an antenna that is “HD Ready.”
DTV broadcasters have been assigned channels in the VHF and
UHF bands, between 54 and 700 MHz, where analog channels 2 to
51 are now. Therefore, as long as a DTV signal is available, your
existing antenna should still work after the transition is complete. |
DTV takes advantage of your home theater surround
sound.
Analog television broadcasts sound just like FM stereo radio. DTV broadcasts are digital
and allow many more options, including Dolby® Digital 5.1 Surround Sound, just like a
DVD. With a DTV set-top box, the digital surround sound will be converted to analog for
your current television. If you have a home theater system, a set-top box will allow you to
enjoy the benefits of digital sound even with an analog television. |
DTV Equipment
The DTV transition has two parts. Broadcasters
must upgrade to digital transmission, and viewers of
over-the-air TV must upgrade to digital reception.
Even with a set-top box, your current analog
television will not be capable of taking full advantage
of DTV. To enjoy the full picture quality and benefits
of DTV, you may want to purchase a new DTV set.
But before you do, there are a few things to consider. |
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A digital display may be an integrated television or just a monitor.
“Integrated” or all-in-one DTV sets have built-in tuners to receive over-the-air DTV
broadcasts and a screen to display the programming. Other than a standard antenna, you
don’t need any other equipment to receive DTV.
The FCC has adopted rules that require all digital TVs sold in the United States to include a
DTV tuner. Today, all TVs with a screen size of 25 inches or larger are required to have a
DTV tuner. By March 1, 2007, all TVs sold in the United States, regardless of screen size,
must incorporate a DTV tuner.
A “Monitor” does not have a built-in tuner and requires you to obtain a separate receiver
(e.g., a set-top box) to receive and view digital programming. DTV set-top boxes can be
purchased at retail stores. Cable and satellite providers also sell or lease set-top boxes for
their specific services. |
| A digital television may be digital cable ready (DCR). Cable subscribers may want to consider a digital cable ready (“plug-and-play”) DTV
set. These sets have the circuitry of a digital cable box built in.
With a CableCARD, a security card that DCR TV owners obtain
from their cable company, scrambled programming such as
premium services may be viewed without a set-top box. |
CableCARD |
| Current
DCR sets are for one-way programming only. While the
consumer electronics and the cable television industries are
working on a two-way agreement, cable subscribers will need a
set-top box from their cable provider for two-way services like video-on-demand and payper-view programming. Most major TV set manufacturers produce DCR sets and HD sets
with built-in digital tuners. Not all TV sets with built-in digital tuners are DCR. |
Digital televisions will work with existing components.
DVD players, camcorders, VCRs, and video game consoles (“peripherals”) will work
with your new DTV. Many DTVs and digital-ready TVs have video inputs which take
advantage of their higher display capabilities, such as DVI or Firewire (see “DTV
Definitions” - pg. 10). Virtually all DTVs also retain composite video inputs (for peripherals)
and antenna inputs (for receiving over-the-air TV signals). When using non-high definition
peripherals, DTVs either display the lower resolution or use signal processing to upconvert
the image to HD. Digital video recorders (DVRs) also work with DTV, but you will need a
DVR that is HD capable to record HD. |
DTV Formats—Aspect Ratio
Televisions come in two aspect ratios. These ratios are 4x3 and 16x9. The aspect ratio
is the comparison of the screen’s width to its height. Traditional analog TV has a 4x3
aspect ratio. This means that a TV screen is 4 inches wide for every 3 inches of height.
Many new digital televisions are 16x9, or “widescreen.” The 16x9 aspect ratio more closely
approximates the look of movies, and broadcasters have begun offering programming that
takes advantage of it. |
| “Letterbox” is the term used when 16x9 content is viewed on a
4x3 screen. In order to display the widescreen content without
distortion or missing parts of the picture, the television will place black
bars at the top and bottom of the image. |
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“Pillar box” is the term used when 4x3 content is viewed on a
16x9 screen. In order to display the squarer traditional picture on
a widescreen monitor, black bars are placed down the sides of
the screen. |
| “Postage stamp” is the term used when a 4x3 transmission
contains widescreen images and its own letterbox bars. When viewed on a television, the image will appear as a smaller
box within your screen. |
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DTV Formats—Resolution
Although there are as many as 18 DTV formats, only 4 formats are commonly used. The
most common formats fall into three broad categories: |
| High Definition TV (HDTV) HDTV in widescreen provides the highest
resolution and picture quality of all DTV
formats. A current analog TV picture is made
up of 480 horizontal lines. An HDTV picture
can have up to 1080 lines, allowing for sharp
picture detail. The most common formats are
720p (“p” stands for progressive scan - see
“DTV Definitions,” pg.11) and 1080i (“i” stands
for interlaced - see “DTV Definitions,” pg.11)
with either 720 progressively (non-interlaced)
scanned lines or 1080 interlaced lines.
Combined with digitally-enhanced sound
technology, HDTV achieves a new benchmark
for sound and picture quality in television. |
| Enhanced Definition TV (EDTV) EDTV is a step up from analog TV and SDTV.
Also called 480 progressive (480p), EDTV is
widescreen 16x9 or traditional 4x3 format and
provides better picture quality than SDTV, but not
as good as HDTV. Most DVDs are encoded as
480p (which means they are not available in high
definition, yet). |
| Standard Definition TV (SDTV) SDTV is the baseline display and resolution for
both analog and digital. Transmission of SDTV is
usually in the traditional 4x3 aspect ratio, but may
be wide-screen 16x9 format. SDTV and analog
TV can deliver up to 480 interlaced (480i)
resolution, although analog TV may be lower. |
DTV Sizes & Costs
As with analog televisions, DTV set sizes
range from very small to quite large. All TV
sizes are measured diagonally across the
screen. So, most DTV sets, which have an
aspect ratio of 16x9, are wider, but shorter,
than analog TV sets of the same screen size.
As with any new consumer electronics
technology, DTV sets have become less
expensive since their introduction. Prices
vary depending on screen size, display
technology, whether a DTV tuner is built-in, and other features. While DTV sets are still more
expensive than their analog counterparts, prices have dropped dramatically.
Shop for TVs |
DTV Screen Choices
You’ll have a number of different screen choices when you look at DTVs. Some of the most
common are: |
| Cathode Ray Tube (CRT) screens - These are traditional color television screens updated for
digital. Their resolution and color capabilities vary from model to model. These screens have a
very bright picture, but are limited in size; the units are typically quite heavy. |
| Rear Projection TVs - Rear projection TVs can be much larger than standard CRTs. They
create the image on a small display, but then enlarge it onto the back of the screen. Older model
rear projection TVs using small CRTs to create the image were dim and hard to see from
extreme angles, but new digital projection technologies like Liquid Crystal Display (LCD), Digital
Light Processing (DLP), and Liquid Crystal on Silicon (LCoS) create brilliant, wide-angle pictures
on ever-larger screens. |
| Front Projectors - Projectors are TVs that create an image by projecting onto a wall or standalone
screen (much like a movie theater). Projectors use the same digital projection technologies
as rear projection TVs but, because the screen is separate, the image can be the size of an entire
wall. Projectors are not as bright and often require the room to be dark in order to clearly see the
image. |
| Flat Panel TVs - Flat Panel TVs are very thin and relatively light weight and are sometimes hung
on the wall. Current flat panels use either LCD or plasma screen technology. Flat panel LCDs
are very thin and produce extremely clear pictures. Plasma screen TVs produce images by
lighting small pockets of colored gas. This technology allows the TV to create a bright, clear
picture in large screen sizes while remaining only a few inches thick. |
| Shop for TV's |
DTV Definitions
Analog TV: Today’s TV system that uses radio frequency (RF) waves to transmit
and display pictures and sound.
Aspect ratio: Screen’s width as compared to its height. For example, for 4x3, the
traditional TV aspect ratio, a 32-inch TV would be 25½ inches wide and 19 inches
tall. A 16x9 widescreen 32-inch TV is closer to a movie screen than a traditional
TV, and would be 28 inches wide and 16 inches tall.
Broadcast Digital-to-Analog Converter Box: A stand-alone device that receives
and converts digital signals into a format for display on an analog television receiver.
CableCARD: Security card that digital cable ready TV owners must obtain from
their cable company in order to view scrambled programming such as premium
services.
Cathode Ray Tube (CRT) Screens: Traditional color television screens are
available for both analog and digital TV. Their resolution and scanning vary from
model to model. These screens have a very bright picture, but are limited in size
and are quite heavy.
Closed Captioning: Service that allows persons with hearing disabilities to
read dialogue, or the audio portion of a video, film, or other presentation, on the TV
screen.
Coaxial: Coaxial inputs (sometimes just called “cable”) provide a simple and
common way to transmit video. Now coaxial inputs are mostly used for connecting a
TV set to an antenna or cable system.
Component Video: Also known as “Y Pb Pr,” this connector splits the video signal
into three parts. With two audio connections, this 5 wire solution is the most
common way to connect EDTVs to DVD players and most HDTV monitors to their
receivers or other set-top boxes.
Composite Video: Also called “RCA” connectors, it is the most common way to
connect peripherals and other components. It consists of one yellow connector for
video and two audio connectors for “right” and “left”. Composite connectors cannot
transmit high definition pictures, so for HDTV, another connector option, such as
HDMI or Component Video, must be used.
Digital Broadcast Satellite (DBS): TV programming delivered via high-powered
satellite. Signals are transmitted to a small dish (usually 18 - 24 inches across)
mounted outside.
Digital Cable Ready TV (DCR): Also referred to as “plug-and-play,” this is a DTV
or other device for digital cable customers that plugs directly into the cable jack, and
does not require a separate set-top box to view analog and unscrambled digital
cable. Used with a CableCARD, it can receive scrambled programming such as
premium services.
Digital TV (DTV): Digital technology television that uses radio frequency (RF) to
transmit computer code and display it as pictures and sound.
Dolby® Digital: Form of multi-channel digital sound, it provides efficient encoding
and noise reduction for high quality surround sound.
Downconvert: Process by which a high resolution signal is reduced to a lower
resolution for display. Usually, extra lines are simply ignored when drawing the lower
resolution image, but sometimes more sophisticated methods are used.
DVI: Digital Video Interface (DVI) is a high quality digital connector. Similar to HDMI
(see definition) and sometimes with HDCP (see definition), DVI can digitally transmit
uncompressed high definition video, preserving perfect picture quality. Unlike HDMI
or Firewire (see definition), DVI requires a separate audio connection.
Enhanced Definition TV (EDTV): Better digital television transmission than SDTV
with at least 480p (progressive), in a 16x9 or 4x3 display and Dolby® digital surround
sound. 480p is the quality of most progressive scan DVDs and players.
EPG: Electronic Program Guide (EPG) is an interactive list of upcoming TV
programming that can be transmitted along with a DTV program.
Flat Panel TVs: Flat Panel TVs are very thin, lightweight TVs that are often hung on
the wall. Current flat panels use either Liquid Crystal Display (LCD) or plasma screen
technology.
Firewire: See IEEE 1394.
Front Projectors: TVs that create the image on a small display, then enlarge it by
projecting it onto a wall or stand-alone screen (much like a movie theater). Front
projectors tend to be dimmer than direct flat panels or CRTs, and often require the
room to be dark to be able to see the image clearly.
HDCP: High Definition Content Protection, a technology used to prevent piracy of
high quality uncompressed video, primarily over DVI connections.
HDMI: High Definition Multimedia Interface, a high quality digital connector. Similar
to DVI and sometimes with HDCP, HDMI can digitally transmit uncompressed high
definition video and audio on the same cable, preserving picture and sound quality.
High Definition TV (HDTV): The highest quality digital television, generally
widescreen 16x9 with at least 720 progressive lines or 1080 interlaced lines and
surround sound.
HDTV Built-In (also Integrated HDTV): HDTV set with the tuner built into the set. It
does not need a separate set-top box to receive over-the-air signals.
HDTV Monitor (also HDTV Ready): TV set with the inputs and capability to become
an HDTV with the addition of an HDTV tuner, HD cable set-top box, or HD satellite
receiver.
HDTV Tuner (also known as decoder or receiver): Device capable of receiving and
decoding HDTV signals. HDTV tuners can either be built into a TV set (see HDTV
Built-In) or be a stand-alone device (see Set-Top Box).
IEEE 1394: Also called Firewire or I-link, IEEE 1394 is a way to transmit compressed
data and video between components on one cable.
Interference: Unwanted electrical signals or noise causing degradation of reception on
a communications circuit.
Interlace Scan: Way to scan vertical lines onto a TV picture by scanning all the odd
lines first, then filling in the even lines. (This happens in the blink of an eye.)
Letterbox: Blank bars above and below the image when viewing 16x9 aspect ratio
content on a 4x3 screen. The opposite of pillar box.
Multicasting: DTV technology that allows each digital broadcast station to split its
digital bandwidth into two or more individual channels of programming and/or data
services. (For example, on channel 7, you could watch subchannel 7-1, 7-2, 7-3 or 7-4.)
Multi-Channel Digital Sound: Feature of DTV that permits numerous streams of
sound to be transmitted for a given program, providing stereo, surround sound, and
even other languages.
Native Resolution: Specific resolution that a television, whether or not integrated, or a
monitor, is designed to display. All other resolutions must be either upconverted or
downconverted for display.
Pan-and-Scan: Alternative to letterboxing, the process by which a 16x9 image is
converted for display on a 4x3 television by zooming in on the picture and panning to
the part of the image that is most interesting. This allows the image to fill the entire
screen, but causes some portions of the image not to be displayed.
Pillar Box: Blank bars to the left and the right of an image when viewing 4x3 aspect
ratio content on a 16x9 screen. The opposite of letterbox.
Pixel: Smallest area of a television picture capable of being sampled and transmitted
through a system, and displayed on a monitor.
Plug-and-Play: See Digital Cable Ready (DCR).
Postage Stamp: Occurs when an image is both letter and pillar boxed. When viewed
on a television, the image will appear as a smaller box within your screen.
Progressive Scan: Way to scan vertical lines onto a TV picture by scanning all the
lines consecutively (progressively). At the same number of lines, progressive scan
produces a higher quality picture than interlace scan. All flat panel and many digital
projection televisions are progressive scan, so they display progressive scan images
more clearly compared to interlaced images.
Pulldown, 3-2: Process by which a movie shot in 24 frames per second (fps) is
shown as an interlaced television image at 30 frames per second.
RCA Connectors: See Composite Video.
Rear Projection TVs: Potentially much larger than standard CRT TVs, rear
projection TVs create an image on a small display, then enlarge it onto the back of
the screen. Old rear projection TVs used a small CRT, while new digital projection
TVs use LCD (Liquid Crystal Display), DLP (Digital Light Processing), or LCoS
(Liquid Crystal on Silicon) to create brilliant, wide angle pictures.
Resolution: Amount of detail that can be seen in a broadcast image. For television,
resolution is measured in horizontal lines displayed (commonly 480, 720, or 1080).
Set-Top Box: A stand-alone device that receives and decodes programming so that
it may be displayed on a television. Set-top boxes may be used to receive
broadcast, cable, and satellite programming.
Spectrum: Range of electromagnetic radio frequencies used in the transmission of
radio, data, and video.
Standard Definition TV (SDTV): Basic digital television format closest to traditional
analog TV.
Ultra High Frequency (UHF): Part of the radio spectrum from 300 to 3000
megahertz which includes TV channels 14-69. After the DTV transition, UHF TV will
be changed to 470 to 698 MHz, which includes channels 14-51.
Upconvert: Process by which a digital, high definition television takes a lower
definition picture and converts it into a higher definition picture. This may be done
by doubling each line as it is drawn on the screen, or by using advanced algorithms
to interpolate the data between each lower resolution line, filling in the missing
image.
Very High Frequency (VHF): Part of the radio spectrum from 30 to 300 megahertz,
which includes TV Channels 2-13, and the FM broadcast band.
Widescreen: Term used generally to describe an aspect ratio wider than 4x3. For
television, refers to the 16x9 aspect ratio.
Yagi Antenna: Type of antenna, generally designed for UHF frequencies, that is
ideal for receiving most DTV stations. Ranging in size from several inches to many
feet, a yagi antenna is the most common design for roof-top antennas. |
| All content credit: www.dtv.gov |
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