Digital TV Basics
DTV stands for digital television, and by June 12, 2009, it will be the only television signal on the airwaves. Although the switch to all-digital TV marks an important shift in the way television is created and transmitted, it doesn't have to be a great change from the way you currently watch TV. Here's what you need to know about the switch from analog to digital television.
Analog vs. digital signals
The difference between an analog and a digital television signal is the way in which the information is encoded:
- Analog signal: Since the first television broadcasts hit the airwaves in the late 1920s, television shows have been sent through the air using an analog signal. An analog signal theoretically has an infinite number of variations, which means that it can (theoretically) transmit an infinite number of subtle variations. If you think of a slide whistle (an analog instrument), as you pull in the slide, the pitch goes up. If you pull the slide in very slowly, the pitch rises smoothly, and you don't hear definite changes from one pitch to the next. Those infinitely smooth gradations of pitch mirror the smooth gradations in an analog television signal.
- Digital signal: A digital signal stores information in the form of a gazillion 1s and 0s. Because each variation in the signal must be represented by 1s and 0s, the number of variations is finite, so a digital signal doesn't have the infinite variability that an analog signal has. To return to the slide whistle example, if you slowly pull in the slide and record it with a digital recorder, the pitch will not rise as smoothly. The pitch will "jump" from one tone to the next, leaving microscopic gaps between any two tones. If the recording is of any decent quality, though, the human ear won't be sensitive enough to hear those tiny jumps, and the recording will sound like a smooth rise in pitch.
Although it may sound like an analog signal is better than a digital signal (and in theory, this is true), analog signals suffer from degradation in a way that digital signals do not. In TV-land, that analog signal degradation comes through as television "snow." You won't get snow from a DTV signal.
Is DTV the same as HDTV?
No — DTV isn't the same as HDTV. DTV stands for "digital television." HDTV (high-definition television) is a specific DTV quality standard, but definitely not the only one. Here are the three most popular DTV quality standards, in order of quality:
- SDTV — Standard Definition Television: SDTV is the most basic quality level for television display and resolution for both analog and digital signals. TV stations already transmit their shows as SDTV-quality analog signals. In fact, many channels have already started transmitting digital SDTV signals alongside their standard analog signals. But many of these analog signals have already gone away, and the great majority of them will be off the air by June 12, 2009.
- EDTV — Enhanced Definition Television: EDTV was a short-lived enhanced format that has a higher resolution than SDTV, but isn't as clear as HDTV. Early adopters of enhanced television quality may have EDTV-quality sets, but you don't see them sold much anymore.
- HDTV — High-Definition Television: This is the highest quality digital signal out there — at least for now. An HDTV signal not only carries enhanced video, but also digitally enhanced sound, so you can get theater-like surround sound from over-the-air HDTV signals. Although HDTV broadcasts are becoming more common (especially for sporting events), most DTV broadcasts will not be high definition, at least for the foreseeable future.
You won't need to get rid of your older analog TV when the time comes to switch to a digital signal; you'll just need to get a set-top box that converts (SDTV and HDTV) digital signals to (SDTV) analog signals that your TV set can understand. If you have a cable or satellite connection, your signal provider should take care of all of that for you, and you won't need a converter box.
An industry standard for a type of wireless computer LAN.
An acronym for Advanced Audio Codec. AAC is the default audio codec format used by Apple's iTunes Music Store.
Supporting devices (such as universal remote controls, touchpads, or digital media adapters) that make the content in your home theater accessible from another location.
A type of telecommunications signal (audio or video) that is translated into electronic pulses with varying strength or frequency.
The width of a video display compared to its height and defined as a ratio, such as 16:9 for widescreen and 4:3 for a traditional TV.
A technical standard developed by the Advanced Television Systems Committee that is synonymous with digital TV, or DTV. HDTV is a subset of ATSC.
The weakening of an audio signal as it travels over a cable. Use the shortest cables possible to lessen sound degradation in a home theater.
Devices in a home theater system that provide audio-only playback, such as CD players/recorders, AM/FM tuners, satellite radio tuners, audio cassette players, and turntables.
Speaker cable connectors resembling a pin connector that bows out in the middle. Comes in both single and dual configurations.
An Internet-related feature set included with some Blu-ray disc players. Provides access to Internet sites supplying information related to the movie or program you are watching, as well as other features such as online chat.
A pole position of speakers in which the drivers are on two faces, opposite each other. Bipole speakers are designed for side or rear surround sound in a home theater. They fire their cones at the same time, in phase.
A continuous stream of bits (binary digits) transmitted over a communications path, such as a cable connecting components in a home theater system.
A high-definition optical media storage alternative to DVDs, developed by Sony Corporation. The name Blu-ray is derived from the blue-colored laser that reads the disc inside a Blu-ray disc player.
A feature set that provides enhanced menus and other extras for some Blu-ray disc players. Includes secondary audio and video circuitry that allows picture-in-picture and audio voiceovers.
The level of black that you see on a video display. The brightness control on a display enables you to adjust this setting.
A smartcard with an embedded chip that descrambles premium channels. You rent a CableCARD — which plugs in to a slot on your HDTV — from your cable service provider.
A long-run Ethernet cabling system most commonly used in homes to carry audio and video signals for computer networks and a whole-home theater network.
A long-run Ethernet cabling system used to carry audio and video signals for computer networks and a whole-home theater network; suitable for very fast computer networks.
A place in your home where you locate the infrastructure devices that enable you to connect your home theater to other parts of the house in a whole-home theater system.
The color portion of the two-component video signal that runs through a video cable (the other component is luminance).
1. (noun) A digital audio interconnect cable with RCA jacks on each end, used to connect home theater components to the A/V receiver. 2. (noun) A cable (also called coax) with an F connector, used to connect a cable TV feed, antenna, or satellite dish to a home theater.
Programs that can compress (for efficient storage and distribution) and decompress (for playback) music and other file types into either lossless or lossy digital files.
A measure of the number of digital bits used to store the color information for a high-definition TV source.
Separates the color and brightness parts of a video signal into their component parts and sends them to the appropriate internal circuitry. Comb filters are more effective than notch filters, and include these types: 2-D, 3-D, and digital.
A type of short-run analog video connection that provides one path for brightness information and two separate paths for color information. These cables typically have red, green, and blue connectors; a better alternative to composite video or S-video.
A type of short-run analog video connection in which both color and brightness (the two components to a video signal) are combined into a single signal. The comb filter inside a display then separates these signals. These cables are usually color-coded yellow.
The level of white that you see on a video display. The contrast control on a display enables you to adjust this setting.
A numeric ratio (such as 800:1) that measures how well a display can show bright brights compared to nuanced darks. A higher ratio is better, but this measurement isn't standardized so you can't easily compare numbers between manufacturers.
Short for A/V controller. A device that performs switching (between audio and video sources) and preamplification tasks in a home theater. One of three separate components (along with a power amplifier and radio tuner) that can be used in place of an all-in-one A/V receiver.
An acronym for Digital Analog Converter. One of two chips in an A/V receiver that decodes surround-sound formats. The DAC converts digitally encoded music signals into analog signals that a receiver’s amplifier and the surround speakers can understand.
A system supported by high-end HDTVs that provides higher (than typical) levels of color depth, capable of supporting millions of colors.
Just like any other file on your computer, except they contain digitally encoded music files that you can play back on your computer, on a portable device, or in your home theater.
A feature of most HDTVs that enables you to connect a coaxial cable from the wall directly to the TV, skipping a set-top box (for nonscrambled channels).
A music or video system that places restrictions on copying or recording digital assets. Protects the copyright interests of music, movie, and other content owners.
DTS is a company that has invented and developed several surround-sound encoding schemes, including the lossless surround-sound format known as DTS-HD.
A pole position of speakers in which the drivers are on two faces, opposite each other. Dipole speakers are designed for side or rear surround sound in a home theater. They fire their cones at different times, out of phase.
A type of display in which the image is created directly on the screen you are watching. Includes old-fashioned tube TVs, plasma displays, and LCD TVs.
A sound signal contained in each of the available audio channels that is distinct and independent from each of the others.
The device in a home theater that shows the picture. Includes direct-view displays (tube, plasma, or LCD TVs) and the separate screen in a front-projection system.
A specification that indicates the level of noise created by an amplifier's power output (the lower, the better).
An acronym for Digital Light Processor. DLP is a method of projecting video in projector systems, developed by Texas Instruments. Uses a special video chip with millions of microscopic mirrors that are moved by computer command to create images.
An all-digital surround-sound format developed by Dolby Laboratories (in 1997) that handles audio compression, available only for digital content.
An all-digital surround-sound format developed by Dolby Laboratories that is an improvement on the older Dolby Digital and Dolby Digital Surround EX systems. Enhancements include an increased bit rate, improved sound encoding, more discrete channels of sound, and backward compatibility.
An all-digital surround-sound format developed by Dolby Laboratories that improves on the older Dolby Digital system. Includes an additional rear (center) surround speaker with a matrixed (intermixed) signal from the left and right surround channels.
An older surround-sound format developed by Dolby Laboratories that includes four channels and five speakers of matrixed (intermixed) multichannel surround sound. An improvement on the Dolby Surround Sound format. Newer enhanced versions include Dolby Pro Logic II and Dolby Pro Logic II.x.
The original surround-sound format developed by Dolby Laboratories that encodes four analog audio channels into two channels.
An all-digital lossless surround-sound format developed by Dolby Laboratories that supports up to 13.1 channels of surround-sound.
1. (noun) The round elements inside a speaker enclosure that move back and forth and create changes in the air pressure (sound waves). 2. (noun) Software files that integrate hardware devices with a PC's operating system.
An acronym for Digital Signal Processor. One of two chips in an A/V receiver that decodes surround-sound formats. The DSP sends the music signals to the correct channels and also can provide sound field enhancements (echo effects).
An acronym for Digital Satellite Service. DSS is a TV source that receives a signal from a satellite dish. The two main DSS services in the U.S. are DirecTV and DISH Network.
A device that decodes television signals feeding in from a satellite dish so that your TV can display the programming.
A lossless surround-sound format on Blu-ray discs and players that can provide up to 7.1 channels of surround sound. There are two variants: DTS-HD High-Resolution Audio (similar to Dolby Digital Plus) and DTS-HD Master Audio (similar to Dolby TrueHD).
A DVD or Blu-ray disc in which you can store media on both sides of the disc, doubling the capacity of a single-layer disc.
1. (noun) A high-capacity optical disc resembling a CD, used primarily for storing video (such as movies) and data. 2. (noun) Other forms of the term DVD indicate a standard for the way data is stored on the disc, such as DVD+RW for a rewriteable disc format.
A device that performs hardware-based decoding of the MPEG video on DVDs. This frees up your computer’s main processor for other tasks (recommended if you have a slower PC that you want to use in your home theater).
DVD-Audio. A newer digital audio format on DVD that offers higher-quality sound and greater capacity than a CD. The DVD-Audio format is not intended for video.
An acronym for Digital Visual Interface. DVI is a digital video technology that was developed as a means to connect computers to digital LCD screens and projectors.
Digital video recorder. A home theater device that records video onto a standard computer hard drive. DVRs (also called PVRs) connect to a program service, usually via a telephone line. TiVo is a major manufacturer of DVRs.
When pertaining to audio CDs, the difference between the softest and loudest musical passages on a compact disc.
File formats used for converting digital content (audio and video files) to smaller file sizes. Some audio encoding formats include MP3, WMA, and AAC. Some video encoding formats include WMV and MPEG.
Federal Communications Commission. The controlling regulatory authority for broadcasters, cable companies, and telephone companies in the United States.
A digital video connection used for some devices in a home theater (originating from the computer industry). Now becoming more common for audio home theater connections.
A specification for a receiver that is measured in Hertz (Hz). The lower frequency ranges (for bass sounds) require more amplifier power than the higher frequency ranges.
A media center application developed by Apple, for the Macintosh. Includes the Front Row software (built into the operating system) and a remote control. This application enables you to use a Mac with your home theater.
A type of projection system in a home theater that includes two parts: a front projector unit and a separate screen. The light is projected from the projector unit onto the screen.
The thickness of speaker cables, such as 16-gauge or 14-gauge (the lower the gauge, the thicker the conductors inside the cable).
A digital radio broadcast that can be incorporated into a home theater without paying a monthly fee. Not all receivers are capable of receiving HD Radio.
An acronym for High-bandwidth Digital Content Protection. HDCP is a strong copy protection system used with DVI. It can limit your ability to make a digital copy of what you're watching.
An acronym for High-Definition Multimedia Interface. HDMI is a short-run analog video interconnect that is used to connect home theater components to high-definition TVs. The HDMI interface carries both audio and video signals over the same cable, and is quickly becoming the connection of choice for high-definition systems.
High-definition TV. A subset of ATSC technology. The HDTV offers spectacular high-definition picture quality in a widescreen format and is now considered a must for home theater systems. HDTV content is available in the form of broadcast programming and Blu-ray discs.
A personal computer (that can be considered a high-quality source device) that you attach to the A/V system of your home theater. An HTPC can feed audio and video content into (and receive content from) your home theater system. You can create a home theater PC out of an existing PC, purchase a new home theater PC, or even build your own.
An integrated home theater system that bundles together a receiver, DVD (or Blu-ray) player, surround-sound speakers, and cables. Other configurations are also available.
A characteristic of the screen in a front-projection system in which one part of the screen is brighter than the other parts. Choose a low-gain (less-reflective) screen to avoid this problem.
The centralized connection point for the audio and video equipment in a home theater, which is typically the A/V receiver.
An advanced video processor (an internal device) that can convert a video signal to a custom resolution that is most suitable for a specific projector or other type of display.
A specification for an amplifier that measures electrical resistance. Most amplifiers are rated at 8 ohms impedance.
Short-run cables that you use to connect home theater components that are located within a few feet of each other (or in the same room).
One of the two scanning methods that draws the picture on the TV screen. Traditional TV systems use an interlaced scan, where half of the picture appears on the screen at a time (the other half follows 1/60th of a second later).
A type of television service provided by a phone company. Uses the same Internet systems used for carrying Web pages, e-mail, and Web video to your TV, via a broadband Internet connection.
Local area network. A computer network that links two or more computers together within a limited range. You can add a computer LAN to your home theater infrastructure, resulting in a whole-home computing system that can make use of your home theater.
1. (noun) An acronym for liquid crystal display. An LCD is a flat-panel TV display with pixels consisting of liquid crystal molecules held between two sets of transparent electrodes. 2. (noun) The technology used in LCD panels, computer monitors, LCD projectors in a front-projection system, and many other devices.
An acronym for Liquid Crystal on Silicon. LCoS is a newer type of projection system that reflects light off of the liquid crystals. This results in a significantly brighter image than an LCD projection system.
An approach used to display widescreen (16:9) content (such as movies) on a standard (4:3) television. Letterboxing maintains the original aspect ratio by displaying horizontal black bars at the top and bottom of the screen.
An acronym for Low Noise Blocker. The LNB is a horn-shaped device connected to the front of the parabola of a satellite dish, used to block extraneous signals.
A type of cable that makes up the infrastructure of a whole-home audio and video network. Long-run cable is designed to minimize signal loss due to interference. The longer the signal has to travel over cable, the more likely that signal will be audibly degraded.
A category of codecs in which all the music information in the audio file is preserved when the file is compressed and stored on a computer, with no loss and very large file sizes. Some lossless codecs include Windows Media Lossless, Apple Lossless, PCM, and Free Lossless Audio Codec (FLAC).
A category of codecs in which part of the music information in the audio file is discarded when the file is compressed, resulting in smaller file sizes. In many cases, the loss of these bits of audio isn't noticeable. Some lossy codecs include MP3, WMA, and AAC.
An audio channel encoded in the soundtrack of a movie or other surround-sound source that provides the low-frequency bass sounds that you hear from the subwoofer. The LFE channel is the ".1" in 5.1 and other surround-sound formats.
Long playing. A phonograph record, often referred to as vinyl, that plays at 33-1/3 revolutions per minute.
The brightness portion of the two-component video signal that runs through a video cable (the other component is chrominance).
Sequential code combinations in a remote control that can perform multiple tasks with the push of a button. For example, you can program a macro that turns on your TV, receiver, and DVD player; sets the receiver to the appropriate source and output modes; and starts the DVD that is in the tray.
A specialized type of media adapter that enables you to view Windows Media Center on your TV without requiring the PC to be locally connected to your home theater. You can either purchase a standalone Media Center extender or get an Xbox 360, which has the Media Center extender functionality built in.
A type of speaker driver that handles midrange frequencies (200 Hz to 2000 Hz).
A pole position of speakers in which all the drivers are on one face of the enclosure. Monopole speakers are also known as direct radiating speakers and can be used anywhere in a home theater system.
A shortened form of MPEG-1 Audio Layer 3. MP3 is a common audio file format for digitally storing music and other audio files on a computer or other device. Uses a form of lossy data compression.
An acronym for Motion Picture Experts Group. MPEG is a group that meets regularly to develop standards for compressed audio and video formats, such as MPEG-2, which is currently the most common standard used in the video world.
A home theater system that extends beyond a single room, allowing simultaneous access to different audio sources of the home theater in multiple rooms.
A cross between a personal video recorder (PVR) and video-on-demand (VoD), offered by a service provider such as a cable company. The hard drive that records and stores the video content you want to watch is located in the service provider's office.
Separates the color and brightness parts of a video signal into their component parts and sends them to the appropriate internal circuitry. Not as effective as a comb filter.
A technical standard developed by the National Television Standards Committee that is synonymous with analog TV — regular (non-HD) television programming.
A pole position of speakers in which the drivers radiate sound in all directions. Omnipole speakers are popular for outdoor applications.
An approach used to display widescreen (16:9) content (such as movies) on a standard (4:3) television. With Pan and Scan, a decision is made as to what constitutes the action area in each frame of the movie. That part of the film frame is retained, while the rest of the frame is lost.
Pulse Code Modulation. An older system for encoding analog music into a lossless digital format. Music CDs and many computer-based sound files (such as .wav files) are based on PCM.
A type of network that allows multiple users to download and share files simultaneously, using a direct connection between computers (without the need for a file server).
Speaker cable connectors with a straight or angled pin. These connectors work best with spring-loaded clip speaker connectors and five-way binding posts.
The individual points (or picture elements) that combined, form an image on a display.
1. (noun) Sometimes called a PDP (plasma display panel). A type of flat-panel display that contains millions of gas-filled cells (pixels) wedged between two pieces of glass. The most common sizes of plasma displays are 42-, 50-, 56-, and 65-inch sizes. 2. (noun) The ionized gas inside a plasma display.
Digital audio or video files that are available for downloading from a Web site. Usually available in a series that are often packaged like daily newscasts or commentary.
One of the two scanning methods that draws the picture on the TV screen. All HDTVs use a progressive scan, in which the entire picture is drawn at once.
Personal video recorder. A home theater device that records video onto a standard computer hard drive. PVRs (also called DVRs) connect to a program service, usually via a telephone line. TiVo is a major manufacturer of DVRs.
RPTV. A type of projection system in a home theater in which both parts of the front projector (the projector and the screen) are housed in a single box. The projector illuminates the back of the screen instead of the front.
A/V receiver. A device that controls your home theater by selecting audio/video sources, decoding surround-sound formats, amplifying sound, and tuning in radio programming.
A measure of the precision and sharpness of a video display's picture, based on the pixels or lines of resolution available on the screen. For HDTVs, display vendors typically focus on the vertical lines of resolution, usually 720 or 1080.
A type of coaxial long-run cable that you can use to connect your home theater to the rest of your house.
Short for Recommended Standard 232. RS-232 is more commonly known as a serial connection. You might use this type of connection between a modem and an older PC. USB has replaced most RS-232 connections.
An acronym for Super Audio Compact Disc. SACD is a newer digital audio format that offers higher-quality sound and greater capacity than a CD.
A service that offers digital radio programming broadcast by satellite to your home theater or car. Satellite radio services such as XM Radio and Sirius offer more than 100 radio stations and charge monthly access fees.
The fine details in the picture of a video display. Most displays enable you to adjust the sharpness setting.
Connections between home theater components that are sitting just a few feet from each other or at least in the same room.
A DVD or Blu-ray disc in which you can store media on only one side of the disc.
Home theater components (devices) that provide the content that you watch or listen to, such as DVD or Blu-ray disc players, DVRs, gaming consoles, CD players, AM/FM tuners, turntables, or home theater PCs.
U-shaped speaker cable connectors that fit behind a screw on a five-way binding post. Spade lugs provide one of the most secure cable connections.
Devices in a home theater system that supply the sound that you listen to. Most home theaters include a surround-sound speaker system with two front speakers, one front center speaker, two side speakers, two or four rear speakers, and a subwoofer.
A method of sending audio or video content in which the content plays while it is delivered over your home network, the Internet, or both.
A speaker in a home theater surround sound system that is designed to play low-frequency (bass) sounds. Typically placed along the front wall of the room.
A feature in a home theater system that enables you to take full advantage of all the audio signals in your source content (such as television programs and DVD or Blu-ray movies).
A type of short-run analog video connection in which color and brightness are separated onto two separate signal paths, so the signal can bypass the display's comb filter. Typically results in a clearer picture than composite video (but not component video).
A video display setting that enables you to set the balance of colors in a display, within a range between red and green.
The major manufacturer of DVRs. With TiVo, you can record video content onto a hard drive of a standalone device. Two models are available: a standard definition model or an HD DVR, which records high-definition content. Both require a monthly service plan.
A type of speaker driver that handles the high-frequency treble range (above 2000 Hz).
Remote control devices used in a home theater that are supposed to work with any electronics device via onboard code databases. Some programmable remotes allow you to create macros that perform multiple tasks at one time.
A scaling of the resolution of a video signal to a higher resolution. This process can occur inside a DVD or Blu-ray disc player, an A/V receiver, or an HDTV. For example, an A/V receiver with upconversion takes lower-resolution video input (such as composite or S-video) and converts it to a higher-resolution format (such as component video or HDMI).
An acronym for Universal Serial Bus. USB is a serial bus standard that allows you to connect peripheral devices to a computer.
Devices in a home theater system that provide video content (TV or movies), such as DVD players, Blu-ray disc players, VCRs, satellite TV receivers, and digital video recorders.
Video-on-demand. A service that provides movie rentals online, similar to pay-per-view (but the content is available at any time, rather than at set times). Many cable companies now offer VoD as part of their digital cable services.
A trademark for products that are based on 802.11 wireless computer LAN standards.
Media software included in certain versions of the Microsoft Windows Vista operating system (Window Vista Home Premium and Windows Vista Ultimate). Using a PC with Windows Media Center is one of the easiest ways to incorporate a computer into your home theater system.
A device that acts as a base station of a wireless LAN, connecting one or more wireless devices to a wired LAN.
An acronym for Windows Media Audio. WMA is the standard audio format used by Windows Media Player. Most WMA files use a lossy data compression system.
A type of speaker driver that handles the low-frequency bass range (below 200 Hz).