Glossary of Terms

Analog TV - encodes television and transports the picture and sound information as an analog signal, that is, by varying the amplitude and/or frequencies of the broadcast signal. All systems preceding digital television, such as NTSC, PAL or SECAM are analog television systems.

Broadcasters using analog television systems encode their signal using NTSC, PAL or SECAM analog encoding and then modulate this signal onto a VHF or UHF carrier. An analog television picture is "drawn" on the screen an entire frame each time, in the manner of a motion picture (cinematograph) film, irrespective of the picture content.

Analog technology has been in use for the past 50 years to transmit conventional TV signals to consumers. Most current television transmissions are received through analog television sets. Analog signals vary continuously, creating fluctuations in color and brightness.

Aspect Ratio - A numerical expression of the relationship of width to height of a TV screen.

4:3: This numerical sequence refers to the aspect ratio of the National Television Systems Committee (NTSC) TV screen, with "4" unit width corresponding to "3" unit height, proportionally, regardless of the actual size of the screen.

16:9: This numerical sequence refers to the aspect ratio of wide screen DTV formats for all HDTV and some SDTV (Standard Definition) video. A "16" unit width corresponds to "9" unit height proportionally, regardless of the actual size of the screen. The widescreen 16:9 numerical sequence provides a viewing experience very similar to that of 35 mm movies.

ATSC - An acronym for Advanced Television Systems Committee, and the name of the Digital Television system used by broadcasters in the U.S.

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. When this happens, viewers see black bars on the sides of the screen or "barn doors."

Black Level - Describes the appearance of darker portions of a video image. Black is the absence of light, so to create the black portions of an image, a display must be able to shut off as much light as possible. Displays with good black level capability not only produce deeper blacks, but also reveal more details and shading in dark or shadowy scenes.

Burn-in - Screen burn-in can damage displays that rely on a phosphor coating on the screen — plasma TVs and rear-projection CRT-based TVs are the most vulnerable to burn-in, and it's less likely, but possible with direct-view CRT TVs. Burn-in can occur when a static image such as a video game, stock or news ticker, or station logo remains on-screen for an extended period. Over time, these images can become etched into the phosphor coating, leaving faint but permanent impressions on-screen. In recent years, makers of plasma TVs have refined the panel technology and included anti-burn-in features which substantially reduce the chances of burn-in. Plasma owners can further reduce the risk by properly adjusting the TV's brightness and contrast settings.

Codec - A codec is a device or program capable of performing encoding and decoding on a digital data stream or signal. The word codec may be a combination of any of the following: 'Compressor-Decompressor', 'Coder-Decoder', or 'Compression-Decompression algorithm'.

Compression - Compression refers to the reduction of the size of digital data files by removing redundant and/or non-critical information ("data" being the elements of video, audio and other "information"). Digital TV in the U.S. would not be possible without compression.

Computer Input - Some HDTV sets have an input like SVGA or VGA that allows the TV sets to be connected to computers.

CRT (Cathode-Ray Tube) - A CRT ("picture tube") is a specialized vacuum tube in which images are created when an electron beam scans back and forth across the back side of a phosphor-coated screen. Each time the beam makes a pass across the screen, it lights up a horizontal line of phosphor dots on the inside of the glass tube. By rapidly drawing hundreds of these lines from the top to the bottom of the screen, images are created. The regular "direct-view" TVs most people grew up watching have a single large picture tube, while CRT-based rear-projection and front-projection TVs use three CRTs: one each for the red, green, and blue primary colors.

Datacasting - Also known as "enhanced TV." Datacasting is the act of providing enhanced options offered with some digital programming to provide additional program material or non-program related resources. This allows viewers the ability to download data (video, audio, text, graphics, maps, services, etc.) to specially equipped computers, cache boxes, set-top boxes, or DTV receivers.

Decoder - A device or program that translates encoded data into its original format (i.e., it decodes the data). See "codec".

Digital - A digital system is one that uses discrete values (often electrical voltages), representing numbers or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (ie, as in an analog system). The distinction between "digital" and "analog" can refer to method of input, data storage and transfer, or the internal working of a device.

The word digital is most commonly used in computing and electronics, especially where real-world information is converted to binary numeric form as in digital audio and digital photography. Such data-carrying signals carry one of two electronic or optical pulses, logic 1 (pulse present) or 0 (pulse absent).

Digital Cable - A service provided by many cable providers, digital cable offers viewers more channels. Contrary to many consumers' beliefs, digital cable is not the same as High- Definition Television or digital television; rather digital cable simply offers cable subscribers the options of paying for more services.

Digital Monitor - DTV monitors are televisions that can display a digital signal but lack an integrated tuner (unlike an integrated digital set), and thus cannot receive a digital broadcast signal without an additional set-top box.

Digital Television (DTV) - is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to analog signals used by analog (traditional) TV. DTV uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set, or a standard receiver with a set-top box, or a PC fitted with a television card. Introduced in the late 1990s, this technology appealed to the television broadcasting business and consumer electronics industries as offering new financial opportunities.

Digital Tuner - A digital tuner serves as the decoder required to receive and display digital broadcasts. It can be included inside TV sets or via a set-top box.

Direct-view TV - A general term for non-projection types of TVs, which include conventional tube TVs and flat-panel plasma and LCD TVs.

DLP - DLP stands for Digital Light Processing. A projection TV technology developed by Texas Instruments, based on their Digital Micromirror Device (DMD) microchip. Each DMD chip has an array of tiny swiveling mirrors which create the image. Depending on the TV's resolution, the number of mirrors can range from several hundred thousand to over two million. DLP technology is used in both front- and rear-projection displays.

There are two basic types of DLP projector: "single-chip" projectors use a single DMD chip along with a spinning color wheel, while much more expensive "3-chip" projectors dedicate a chip to each primary color: red, green, and blue.

Dolby Digital - A discrete multichannel digital audio format that is the official audio standard for HDTV (and DVD). Dolby Digital is normally associated with 5.1-channel surround sound (five speakers plus a low-frequency subwoofer). Though this channel configuration is common, it is only one of several possible variations — a "Dolby Digital" soundtrack can mean anything from 1 to 5.1 channels.

Flat screen TV - Flat screen TVs, like LCDs and plasmas, are the new thing in television sets. They can sit on a stand or hang on the wall.

HDMI - HDMI stands for High-Definition Multimedia Interface. It's an all-digital audio/video interface used to connect digital equipment like HDTVs and high definition DVD players.

HDTV - An acronym for High Definition Television, the highest quality of digital television, in either 720p, 1080i or the latest 1080p formats.

HDTV-ready - Term used to describe TVs which can display digital high-definition TV formats when connected to a separate HDTV tuner. These TVs generally have built-in tuners for receiving regular NTSC broadcasts, but not digital. An HDTV-ready TV may also be referred to as an "HDTV monitor."

Interlaced Scanning - This process divides and presents each video frame as two fields. Imagine a video frame being divided by the odd and even horizontal lines that make up the picture. The first field presents the odd lines; the second field represents the even lines. The fields are aligned and timed so that, with a still image, the human eye blends the two fields together and sees them as one. Motion in the image makes the fields noticeable. Interlace scanning allows only half the lines to be transmitted and presented at any given moment.

LCD - LCD stands for Liquid Crystal Display and is the most popular type of digital television set because it's the least expensive. LCD projectors send light through a silicone chip, which manipulates the light. In flat panels, images are created by lighting up a fixed grid of pixels.

Letterbox - Letterbox refers to the image of a wide-screen picture on a standard 4:3 aspect ratio television screen, typically with black bars above and below. It is used to maintain the original aspect ratio of the original source (usually a theatrical motion picture of 16:9 aspect ratio or wider).

Multicasting - The option to multicast was made possible by digital technology to allow each digital broadcast station to split its bit stream into 2, 3, 4 or more individual channels of programming and/or data services. (For example, on channel 7, you could watch 7-1, 7-2, 7-3 or 7-4.)

Must-carry - This refers to the legal obligation of cable companies to carry analog or digital signals of over-the-air local broadcasters.

NTSC - NTSC is the acronym that stands for National Television Systems Committee" and the name of the current analog transmission standard used in the U.S., which the committee created in 1953.

Pixel - A pixel (short for picture element, using the common abbreviation "pix" for "pictures") is a single point in a graphic image. Each such information element is not really a dot, nor a square, but an abstract sample. With care, pixels in an image can be reproduced at any size without the appearance of visible dots or squares; but in many contexts, they are reproduced as dots or squares and can be visibly distinct when not fine enough. The intensity of each pixel is variable; in color systems, each pixel has typically three or four dimensions of variability such as red, green, and blue, or cyan, magenta, yellow, and black.

Plasma - In a plasma HDTV, light is created by phosphors excited by a plasma discharge between two flat panels of glass. Plasma HDTVs are expensive, but many think they make the best picture.

Projection TV - There are two types of projection TVs: Front projection, where an image is projected onto a screen like in a movie theater; and rear projection (the "big screen TVs") where an image is projected on the back of a large TV screen.

QAM - QAM is the format that cable companies use to transmit signals to the home. Digital TVs with a built-in QAM tuner can get unscrambled digital cable channels without a cable-box.

Resolution - The sharpness of a video image, signal or display, generally described either in terms of "lines of resolution," or pixels. The resolution you see depends on two factors: the resolution of your display and the resolution of the video signal.

Standard Definition TV Format (SDTV) - There are two main digital formats - HDTV and SDTV. SDTV typically does produce better quality images than that of traditional analog TV and pictures somewhat akin to digital cable. However, its images are not nearly as sharp as the images from the ultimate form of digital television: High-definition TV (HDTV).

Set-top Converter Box - This unit sits on top of the viewer's analog TV, receives the Digital TV signal, converts it to an analog signal, and then sends that signal on to the analog TV.

Super Video Graphics Array (SVGA) - This acronym is short for the "Super Video Graphics Array" display mode. SVGA resolution is 800 x 600 pixels.

Terrestrial Broadcasting - This is a broadcast signal transmitted "over-the-air" to an antenna.

Upconverting - A Process by which a standard definition picture is changed to a simulated high-definition picture.

Video Graphics Array (VGA) - This acronym is short for the "Video Graphics Array" display mode. VGA resolution is 640 x 480 pixels.

Viewing Angle - Measures a video display's maximum usable viewing range from the center of the screen, with 180° being the theoretical maximum. Most often, the horizontal (side to side) viewing angle is listed, but sometimes both horizontal and vertical viewing angles are provided. For most home theaters, horizontal viewing angle is more critical.

Wide Screen - 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 wide screen." Most motion pictures also have a 16:9 wide screen aspect ratio. Most Digital TVs have a screen that is wider than it is tall (if a Digital TV screen is nine inches high, it's 16 inches wide.) When watching a show recorded in the wide screen format on a Digital TV, viewers see more of the movie, while when viewing wide screen format on an analog TV, cropped edges are evident.