AC-3 - Audio coding 3 (see Dolby Digital).

ACATS - Advisory Committee on Advanced Television Service; special FCC committee that recommended DTV standards in 1997.

After color temp - Geek box term. The color temperature at a given brightness level after grayscale calibration. Usually expressed in degrees K; ideally as close to 6,500K as possible.

After grayscale variation - Geek box term. After calibration, the average amount of variation from an ideal of 6,500K, measured over the entire range of the grayscale--typically 20 to 100 IRE in 10-IRE increments.

ALiS - ALiS (alternate lighting of surfaces) technology developed by Fujitsu/Hitachi for plasma panel displays. On a conventional plasma TV, all pixels are illuminated at all times. With an ALiS plasma panel, alternate rows of pixels are illuminated so that half the panel's pixels are illuminated at any moment, somewhat similarly to interlaced scanning on a CRT-type TV. This allows higher native resolution than designs with discrete pixels (typically 1,024x1,024 versus 1,024x768 for 42-inch plasmas), but ALiS has historically suffered in other areas, including black-level performance.

analog hole - A perceived chink in the armor protecting copyrighted content from unauthorized distribution--for example, over the Internet. Currently HDTV and other high-bandwidth content can be converted from analog to digital format and distributed widely. The MPAA wants to "plug" the analog hole by placing watermark detection capability in analog-to-digital converters (ADCs), which convert analog audio and video into digital form.

anamorphic - Adopted from the film technique of shooting a wide-screen image on a square 35mm frame, it's the process of compressing wide-screen images to fit into the squarer standard 4:3 television signal. The images are then expanded for viewing in their original format on a wide-screen display device. Wide-screen or letterboxed DVDs that are not anamorphic have less detail when projected on a wide-screen monitor. In other words, a nonanamorphic wide-screen DVD is designed to be shown letterboxed on a standard "square" TV but appears with a black box all around the image when shown on a larger 16:9 wide-screen TV. To fill a 16:9 screen, a nonanamorphic DVD has to be blown up, resulting in loss of resolution and detail. Conversely, a DVD that is anamorphic, enhanced for 16:9, or enhanced for wide-screen delivers 33 percent more resolution than regular letterboxed transfers, is designed to be shown on a 16:9 TV, and does not need to be blown up. When one of these DVDs is shown on a "square" TV, it is often subject to anamorphic downconversion artifacts unless the TV has a vertical compression feature.

anamorphic downconversion - Processing present in all DVD players that converts the image from an anamorphic DVD for display on a regular 4:3 TV. In the initial setup of a DVD player is a choice between a 16:9 or a 4:3 TV; the 4:3 options engage this processing, which often introduces artifacts such as jaggies and undulations during pans.

anamorphic squeeze - See vertical compression.

ANSI - American National Standards Institute, a professional measurements and standards group.

ANSI lumens - Light-output specification set in 1993 used mainly to measure brightness of front-projection televisions; more exact than undefined lumens. The average 7-inch, CRT front-projection television is capable of between 150 and 175 ANSI lumens, while 9-inch CRT sets emit between 200 and 240. DLP and LCD projectors range from 600 to 7,000, depending on the model.

artifact - Any abnormality in a video image; typically results from digital processing, the interlaced-scanning method, the conversion from one video format to another, or signal transmission issues.

aspect ratio - The relationship between the width and height of an image; the standard DTV wide-screen ratio is 16:9 (1.78:1), as compared to the squarer NTSC ratio of 4:3 (1.33:1).

ATRC - Advanced Television Research Consortium, an organization of several large consumer electronics companies, research facilities, and broadcast entities that developed U.S. high-definition television (HDTV) standards.

ATSC - Advanced Television Systems Committee, a government-sanctioned, industry-led standard-setting body that adopted the official DTV standard for the United States in 1997. The acronym also refers to the DTV and HDTV standards.

ATVEF - Advanced Television Enhancement Forum, a coalition of broadcasters as well as hardware and software makers that created a standard for interactive data broadcasting, most of which would be broadcast as part of HD transmissions. These standards are currently under consideration by Society of Motion Picture and Television Engineers (SMPTE). The group discontinued operations on November 1, 2003.