Aspect Ratio: The ratio of image width to image height. Common motionpicture ratios are 1.85:1 and 2.35:1. Television screens are usually 1.33:1 (also known as 4:3), which is similar to the Academy standard for films in the `50s. HDTV is 1.78:1, or 16:9. When widescreen movies (films with aspect ratios wider than 1.33:1) are displayed on 1.33:1 televisions, the image must be letterboxed, anamorphically squeezed, or panned-andscanned to fit the screen.

ATSC: Advanced Television Systems Committee. Government-directed committee that developed our digital television transmission system.

Attenuate: To turn down, reduce, decrease the level of the opposite of boost.

Black Level: Light level of the darker portions of a video image. A black level control sets the light level of the darkest portion of the video signal to match that of the display`s black level capability. Black is, of course, the absence of light. Many displays, however, have as much difficulty shutting off the light in the black portions of an image as they do creating light in the brighter portions. CRT-based displays usually have better black levels than DLP, plasma, and LCD, which rank, generally, in that order.

Brightness: For video, the overall light level of the entire image. A brightness control makes an image brighter however, when it is combined with a contrast, or white level control, the brightness control is best used to define the black level of the image (see Black Level). For audio, something referred to as bright has too much treble or high frequency sound.

B-roll: Supplementary video of scenes and interviews used to complement the primary video.

Cathode Ray Tube: (CRT) Analog display device that generates an image on a layer of phosphors that are driven by an electron gun.

Chrominance: (C) The color portion of a video signal.

Coaxial: 1) A speaker typically with one driver in the middle of, and on the same axis as, another driver. 2) An audio or video cable with a single center pin that acts as the hot lead and an outer shield that acts as a ground.

Codec: Mathematical algorithms used to compress large data signals into small spaces with minimal perceived loss of information.

Component Video: A signal that`s recorded or transmitted in its separate components. Typically refers to Y/Pb/Pr, which consists of three 75-ohm channels: one for luminance information, and two for color. Compared with an S-video signal, a Y/Pb/Pr signal carries more color detail. HDTV, DVD, and DBS are component video sources, though most DBS material is transcoded to component from composite signals.

Composite Video: A signal that contains both chrominance and luminance on the same 75-ohm cable. Used in nearly all consumer video devices. Chrominance is carried in a 3.58-mHz sideband and filtered out by the TV`s notch or comb filter. Poor filtering can result in dot crawl, hanging dots, or other image artifacts.

Contrast: Relative difference between the brightest and darkest parts of an image. A contrast control adjusts the peak white level of a display device.

DBS: Direct Broadcast Satellite. Term that replaced DSS to describe smalldish, digital satellite systems such as DirecTV and Network.

Digital Theater Systems: See DTS.

D-ILA: Direct Drive Image Light Amplifier. This Hughes/JVC technology uses a reflective LCD to create an image. A light source is then reflected off the reflective LCD and is directed through a lens to a screen.

Direct-View Television: Display whose image is created on the surface from which it is viewed.

DLP: Digital Light Processing. A Texas Instruments process of projecting video images using a light source reflecting off of an array of tens of thousands of microscopic mirrors. Each mirror represents a pixel and reflects light toward the lens for white and away from it for black, modulating in between for various shades of gray. Three-chip versions use separate arrays for the red, green, and blue colors. Single-chip arrays use a color-filter wheel that alternates each filter color in front of the mirror array at appropriate intervals.

DMD: Digital Micromirror Device. Texas Instruments engine that powers DLP projectors. Uses an array with tens of thousands of microscopic mirrors that reflect a light source toward or away from the lens, creating an image. Each mirror represents a pixel.

Dot Crawl: An artifact of composite video signals that appears as a moving, zipper-like, vertical border between colors.

DTV: Digital Television. Umbrella term used for the ATSC system that will eventually replace our NTSC system in 2006. HDTV is a subset of the DTV system. While the FCC does not recognize specific scan rates in the adopted DTV system, typically accepted rates include 480i, 480p, 720p, and 1080i.

D-VHS: Digital VHS. Digital signals recorded onto magnetic tape. Greater capacity than typical VHS can record compressed HDTV signals. See D- Theater.

DVD: Officially known as the Digital Video Disc, though marketers unofficially refer to it as the Digital Versatile Disc. DVD uses a 5-inch disc with anywhere from 4.5 Gb (single layer, single-sided) to 17 Gb storage capacity (double-layer, double sided). It uses MPEG2 compression to encode 720:480p resolution, full-motion video and Dolby Digital to encode 5.1 channels of discrete audio. The disc can also contain PCM, DTS, and MPEG audio soundtracks and numerous other features. An audio-only version, DVD-A uses MLP to encode six channels of 24-bit/96-kHz audio.

DVD-A: Digital Versatile Disc-Audio. Enhanced audio format with up to six channels of high-resolution, 24-bit/96-kHz audio encoded onto a DVD, usually using MLP lossless encoding. Requires a DVD-A player and a controller with 6-channel inputs (or a proprietary digital link) for full compatibility.

DVD-R: A recordable DVD format similar to CD-R in that it is a write-once medium. Backed by Pioneer, Panasonic, Toshiba, and others.

DVD-RW: A recordable DVD format similar to CD-RW in that it is rerecordable medium. Backed by Pioneer, Panasonic, Toshiba, and others.

DVD+R: A recordable DVD format similar to CD-R in that it is a write-once medium. Backed by Sony, Philips, Yamaha, HP, and others.

DVD+RW: A recordable DVD format similar to CD-RW in that it is rerecordable medium. Backed by Sony, Philips, Yamaha, HP, and others.

DVD-RAM: A recordable DVD format similar to DVD-RW in that it is a rewriteable format. Unlike DVD-RW it is capable of being written to and erased over 100,000 times. Backed by Hitachi, Panasonic, Toshiba, and others

DVI: Digital Visual Interface. Connection standard developed by Intel for connecting computers to digital monitors such as flat panels and DLP projectors. A consumer electronics version, not necessarily compatible with the PC version, is used as a connection standard for HDTV tuners and displays. Transmits an uncompressed digital signal to the display. The latter version uses HDCP copy protection to prevent unauthorized copying. See also HDMI.

Dynamic Range: The difference between the lowest and the highest levels in audio, it`s often expressed in decibels. In video, it`s listed as the contrast ratio.

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