Glossary of Terms

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Select a letter to browse the glossary, or search for a specific term.

A/D
Analog to digital conversion.

Addressable Resolution
The inherent resolution of a display device (plasma screen, television, projector or monitor) which enables pixels to be individually addressed. The device, however, may not be capable of displaying this resolution.

Aliasing
An artifact produced by distorting or not using the high frequency components of an image, signal, data stream, etc. due to some limitation such as undersampling or inadequate detection bandwidth. The result is unwanted appearance of low frequency components (aliases) which must be filtered out and replaced with the missing high frequency components. The process of removal/replacement of frequencies is called "anti-aliasing".

Analog
A form of data transmission using a continuously variable signal, in contrast to digital transmission, which uses discrete numerical steps.

Analog TV
"Standard" television broadcasts analog TV. Analog signals vary continuously, representing fluctuations in color and brightness. NTSC is an analog system.

Anamorphic
A process of storing images with different horizontal and vertical magnifications for later display through a reversed procedure. Generally, the image is squeezed inward from the sides in relation to the height. So, if the original picture is of a circle, then the anamorphic processing would produce a tall, thin oval. On receiving the signal, some device will readjust these different horizontal and vertical magnifications back to normal. The anamorphic process has the advantage of enabling wide aspect ratio pictures to be stored on a recording medium originally designed for the 4x3 aspect ratio. Specifically, an anamorphic DVD stores a high quality widescreen movie for viewing on widescreen TVs.

ANSI Lumens
A unit that indicates lumen brightness of projectors. ANSI (American National Standards Institute) has established the standard for measurement of lumen brightness. For example, if one projector uses Halogen lamps and another metal-halide, the halogen projector will seem noticeably dimmer even if the two units rate the same.

Anti-aliasing
In electronic communication, the term refers to the adding of additional images or parts of images so as to convince the eye that it sees something that cannot be represented digitally. The goal is usually to make curved or diagonal lines appear smooth, or to show straight horizontal or vertical lines in certain positions. Lines cannot be represented smoothly or in the proper position because the display device resolution is not sufficient to represent the image accurately. In practice, the eye is fooled into completing the edge between the background and foreground colors.

Artifacts
Unwanted visible effects in a picture created by disturbances in the transmission or image processing, for example "edge crawl" or "hanging dots" in analog pictures, or "pixelation" in digital images.

Aspect Ratio
The aspect ratio of a display screen is described by the width x height, for example 4x3 means 4 units wide by 3 units high. Current U.S. TV broadcasts use a 4:3(1.33:1) aspect ratio. Digital TV is broadcast with a 16:9 (1.78:1) ratio, and most feature films are shot in the ratio range of 1.85:1 up to 2.35:1.

ATSC
The Advanced Television Systems Committee Inc., is an international, non-profit organization developing voluntary standards for digital television. The ATSC member organizations represent the broadcast, broadcast equipment, motion picture, consumer electronics, computer, cable, satellite, and semiconductor industries. The most common formats are 480p (525 scan lines, 480 of them active, per frame progressive scan, each scan line divided into 640 or 704 parts or pixels, 720p which is 720 active scan lines each with 1280 pixels, and 1080i (1080 active scan lines as two 540 scan line interlaced fields, 1920 pixels on a line).

ATTC
The Advanced Television Technology Center is a private, non-profit corporation organized by members of the television broadcasting and consumer products industries to test and recommend solutions for delivery and reception of a new U.S. terrestrial transmission system for digital television (DTV) service, including high definition television (HDTV). The Technology Center operates a state-of-the-art laboratory facility that supports the needs of the U.S. television industry and private standards-setting bodies. Its primary activity is to facilitate implementation of digital television.
Website: www.attc.org

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