Resource Center: How to Speak A/V
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Entries starting with: laser: A device that generates a coherent, monochromatic beam of light. These two characteristics allow a laser beam to be focused down to very small areas, a trait essential to its use in the CD, DVD, MiniDisc, and other optical or magneto-optical data-storage systems. late reflections: Echoes in an enclosed space that reach the ear after multiple reflections and, consequently, have a relatively long delay time; see early reflections and reverberation. LCD (liquid-crystal display): A matrix of thin-film transistors applies voltage to liquid crystal-filled cells sandwiched between two sheets of glass. When hit with an electrical charge, the crystals “untwist” to filter light coming from behind the cells. Color LCD panels or chips — with each pixel comprising a red, green, and blue cell — are used in many flat-screen TVs and computer monitors as well as in video front projectors and rear-projection HDTVs. Monochrome LCD readouts are used on the faceplates of many A/V components and remote controls. LCoS (liquid crystal on silicon): A display technology in which liquid crystals are applied to silicon chips. As voltage is applied, the light reflected by pixels on the chips varies. It is used in both high-definition front projectors and rear-projection TVs. See DLP and LCD. LED (light-emitting diode): A semiconductor device used as an indicator light on many components. lenticular: In video, anything containing many small lenses; commonly used to describe video projection screens optimized to produce high picture brightness in certain viewing directions. letterboxing: The scaling of a widescreen image to fit within a squarish 4:3 aspect ratio screen by shrinking the image’s vertical dimension so that the width fits exactly and filling the resulting spaces above and below the image with black bars. Critics of the technique think that the screen area is being “wasted” by the letterboxing bars; see pan-and-scan. LFE (low-frequency effects) channel: The “0.1”-channel of a 5.1-channel surround sound system, containing only very deep bass; in movie soundtracks it is used primarily to enhance loud sound effects. limiter: A circuit that prevents a signal from exceeding a certain level. line doubler: A circuit or standalone component that smoothes the picture by doubling the number of scan lines in an interlaced video image, normally by deinterlacing it; line triplers and line quadruplers are also available (see deinterlacing). line interpolation: A process by which additional scan lines are synthesized out of the original scan lines present in a video image; used to smooth the picture and increase apparent vertical resolution; see line doubler. linearity: Describes the accuracy with which a component’s output signal tracks the input signal; a device whose output varies in direct proportion to the input is said to be linear. line-level: Signal voltages in the range delivered from the outputs of most audio source components (such as CD players) and preamplifiers; also known as low-level or preamp-level. See speaker-level. lines of resolution: The units that describe the ability of a TV, camera, video recorder, or other device to convey fine picture detail; higher values are usually better. Normally refers to horizontal resolution but can also describe vertical resolution; see scan lines, with which lines of resolution are often confused. LNB (low-noise block downconverter): A device mounted at the focal point of a satellite dish that amplifies the microwave signals collected by the dish and converts them to a lower frequency that’s sent to a satellite receiver over standard coaxial cable. An LNBF is an LNB with an integrated feedhorn. local-area network (LAN): A system for connecting computers and other digital devices in close proximity so they can share files, multimedia content, and resources. logic: In a surround sound system, “logic-steering” is used to improve separation between multiple channels derived from matrix-encoded two-channel signals. “lossless” and “lossy” compression: Two types of data encoding to reduce digital file sizes for storage or transmission. In lossless compression — such as the Apple Lossless encoding available for the iPod — mathematically redundant data are compressed in such a way that the original signal can be reconstructed exactly. In lossy compression — as in MP3, AAC, Dolby Digital, and most other common codecs — besides redundancies, actual parts of the signal are thrown away because they aren’t needed for perceptually accurate reproduction. For instance, some soft sounds might be dumped because they’d be masked by simultaneous louder sounds in the same parts of the spectrum. loudness compensation: A form of equalization that progressively emphasizes low frequencies (and sometimes high frequencies) as volume is reduced. Loudness-compensation circuits are designed to offset the ear’s loss of low-frequency sensitivity as the sound level decreases. low-pass filter: A circuit, as in a speaker’s crossover network, that progressively rolls off signals above its cutoff frequency, passing those below to, say, a woofer; see filter and high-pass filter. lumen: A unit for the rate of visible light output from, say, a TV. luminance (Y): The portion of a video signal in which variations of lightness and dark — not changes of color (chrominance) — in an image are encoded. Black-and-white TVs display only luminance signals. lux: A unit of illumination, equal to one lumen per square meter. Abbreviations |
