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KET Digital Guide

DTV Glossary

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4:3—the aspect ratio of the NTSC TV screen, proportionally four units wide for every three units high, no matter the size of the screen.

16:9—the aspect ratio of widescreen DTV video (including all high- and some standard-definition video), proportionally 16 units wide for every 9 units high, no matter the actual size of the screen.

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analog—the technology in use for more than 50 years to transmit conventional radio and TV signals. Vinyl recordings and motion picture films are other examples of analog technology.

aspect ratio—the ratio of television picture width to height. In NTSC and PAL video, the present standard is 4:3. In widescreen video, it is typically 16:9.

ATSC—an acronym for Advanced Television Systems Committee, and the name of the DTV system used by broadcasters in the U.S. (akin to European COFDM).

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bandwidth—the amount of broadcast spectrum available to each communications licensee. For digital transmission, the FCC has allocated 6 MHz (megahertz) of UHF bandwidth for each broadcaster. This amount of bandwidth can carry full-spectrum HD signals, several multicast digital signals, data, or a combination of these elements.

barn doors—a term used in television production to describe the effect that occurs when a 4:3 image is viewed on a 16:9 screen. Viewers see black bars (“barn doors”) on the sides of the screen. Also called pillar-boxing.

binary—a numbering system using only the digits 0 and 1. All computer programs are executed in binary form.

bit—a binary digit—the smallest unit of data in a digital system. A bit is a single 1 or 0. A group of bits, such as 8-bits or 16-bits, compose a byte.

byte—a group of bits. The number of bits in a byte depends on the processing system being used. Typical byte sizes are 8, 16, and 32.

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COFDM: (acronym for “Coded Orthogonal Frequency Division Mulitiplexing”)’the DTV standard used in Europe (akin to ATSC in the U.S.).

compression—the process of fitting a large file into a space that is many times smaller. In the case of video, the method used for the DTV standard is MPEG-2.

computer input—Some HDTV sets have an input (typically SVGA or VGA) that allows the TV set to be connected to a computer.

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datacasting—Digital television allows for the transmission of not only digital sound and images, but also digital data (text, graphics, maps, services, etc.). See our KET DataCast page for more information.

DBS—See direct broadcast via satellite.

digital cable—a service provided by many cable operators which offers viewers more channels, access to pay-per-view programs, online guides, and in some cases HDTV.

digital television (DTV)—a more efficient and flexible form of television broadcast technology. Since television came into being, stations have broadcast programs using an analog signal, where subtle changes in the waveform define the image and sound. With digital television, the signal is broadcast as “bits and bytes,” the same as computers use. That means DTV can deliver high-definition pictures, surround-sound audio, and several channels all at the same time.

digital tuner or digital receiver—A digital tuner serves as the decoder required to receive and display digital broadcasts. A digital tuner can downconvert broadcasts for an analog TV or provide a digital signal to a digital television. It can be included inside a TV set or via a digital TV converter box.

digital TV converter box—a set-top device that connects to a traditional analog television set and enables it to receive digital broadcast signals via an antenna.

digital video recorder (DVR)—a video recording device (such as TiVo) that uses a hard disk drive to record programs.

direct broadcast via satellite (DBS)—a form of television delivery in which subscribers receive programs via a small satellite dish. The signal is NTSC, digitized and compressed via a proprietary format and decompressed by a set-top box. Some DBS services offer DTV and HDTV content.

Dolby Digital—the approved 5.1-channel (surround-sound) audio standard for ATSC digital television. Six distinct audio channels are used: left, center, right, left rear, right rear (indicated by the “5”), and a subwoofer (indicated by the “.1”).

Dolby Surround (Dolby Stereo)—four audio channels (left, center, right, and surround) converted to two channels referred to as right-total and left-total.

downconverting—the process by which a high-definition signal is converted to a standard-definition picture.

DTV—See digital television.

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electronic programming guide (EPG)—an application that provides an on-screen listing of all programming and content that a DTV viewer has available. Also called interactive programming guide (IPG).

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FCC—the Federal Communications Commission; the body that governs, among other things, radio and television broadcasting in the U.S.

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high-definition television (HDTV)—a digital television format that provides high-quality widescreen pictures with Dolby 5.1 surround sound. The aspect ratio of HDTV pictures is 16:9. This is the most superior video picture available in digital TV. In the U.S., the 1080i (see interlaced scanning) and 720p (see progressive scanning) formats are the two acceptable HDTV broadcast formats. HDTV is a type of DTV.

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interactive programming guide (IPG)—an application that provides an on-screen listing of all programming and content that a DTV viewer has available. Also called electronic programming guide (EPG).

interlaced scanning—Interlaced scanning sends information to each pixel in the even-numbered rows of pixels in a frame of video, then to odd-numbered rows. 1080i is an interlaced-scanning standard. (See also progressive scanning.)

I/O—“input/output”; typically refers to sending data to and from devices.

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letterbox—refers to the image of a widescreen picture on a standard 4:3 aspect ratio television screen, typically with black bars above and below. It is used to maintain the aspect ratio of the original source of 16:9 aspect ratio video.

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MPEG-2—compression standards for moving images and audio set by the Motion Pictures Expert Group (MPEG), an international committee of industry experts. MPEG-2 is the basis for ATSC digital television transmissions in the U.S.

multicasting—the ability to send more than one channel of programming within the allotted channel spectrum. While analog channels have traditionally used a standard amount of spectrum (represented by each click on your tuner dial), digital channels can squeeze four or more channels into their spectrum.

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NTSC—National Television Systems Committee; the group that set the analog television standard 50 years ago. The abbreviation NTSC is also used to refer to the analog television standard in the United States.

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PAL—Phase Alternation Line (PAL) is the analog television display standard that is used in Europe and certain other parts of the world. The U.S. uses the NTSC standard.

Pillar-boxing—a term used in television production to describe the effect that occurs when a 4:3 image is viewed on a 16:9 screen. Viewers see black bars (“barn doors”) on the sides of the screen.

pixel—a combination of the words “picture” and “element.” A pixel is the smallest discernible sample of video information, the “little dots” that make up an overall picture.

pixels per inch (PPI)—the measure of the sharpness (that is, the density of illuminated points) on a television display screen.

progressive scanning—Progressive scanning sends information to each pixel in a frame of video sequentially—left to right, top to bottom—to create the image. 720p is a progressive-scanning standard. (See also interlaced scanning.)

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resolution—the amount of data used to make up a picture, screen, or audio track. The more data in a picture, the richer the image and the higher the resolution. Resolution is measured in a number of ways, depending on the medium used. For example, digital TVs describe their resolutions in terms of the number of pixels or dots that make up the picture along the vertical and horizontal axes. One of the high-definition picture formats is composed of 1080 active lines, and each line is composed of 1920 active pixels. Therefore, each frame has more than 2 million (1080 X 1920 = 2,073,600) color pixels creating the image. By way of contrast, old analog televisions have about 480 active lines, with each line holding about 440 pixels. So each frame has slightly more than 200,000 color pixels in use creating the image.

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standard-definition TV (SDTV)—a digital television format similar in quality to NTSC. While not as high-quality as HDTV, SDTV signals display clear pictures and sound without noise, ghosts, or interference.

SVGA—acronym for the Super Video Graphics Array display mode. SVGA computer monitors have a resolution of at least 800 X 600 pixels.

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terrestrial broadcasting—a broadcast signal transmitted “over the air” from a ground-based transmitter to an antenna.

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upconverting—the process by which a standard-definition picture is changed to a simulated high-definition picture.

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VGA—acronym for the Video Graphics Array display mode. VGA computer monitors have a resolution of at least 640 X 480 pixels.

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widescreen—a term given to picture displays with a wider aspect ratio than NTSC 4:3. Digital HDTV or SDTV is referred to as “16:9 widescreen.” Most motion pictures also have a 16:9 widescreen aspect ratio. Most digital TVs have screens wider than they are tall (for every 9 vertical inches, a DTV screen is 16 inches wide).

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Portions of this glossary were compiled from information published by PBS and KCET/Los Angeles.

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