Resource Center: How to Speak A/V
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Entries starting with: sample: The value of a signal at an instant in time. sampling: Repeatedly and regularly obtaining samples of a waveform, such as a soundwave, in order to digitize it; see quantization. sampling frequency (or rate): In digital audio, the number of times a signal is sampled each second. The standard sampling rate for the CD format is 44.1 kHz, which means that the voltage of the audio waveform for each channel is measured 44,100 times per second. The sampling rate must be at least twice the highest frequency to be recorded. SAP (secondary audio program): A separate mono channel broadcast along with the two stereo channels in the U.S. system for stereo analog TV. The SAP channel can be used for an alternative-language soundtrack or descriptions for the sight-impaired. saturation: In video, saturation is the intensity of a color, specifically defined as its “distance” from white (for example, a lightly saturated pink vs. a deeply saturated red); also, the professional name for a video monitor’s color control. scaler: A circuit or digital signal processing program that converts a video signal from one image format to another (for instance, from 480i to 720p). scan doubler: see line doubler. scan line: One of the thin horizontal strips that together make up a video field or frame. The basic subunit of an analog video image; see pixel. scan-velocity modulation: In a tube TV, a technique for improving the apparent sharpness of an image by varying the rate at which a scanning electron beam sweeps across the screen or the face of a CRT. screen-door effect: A faint gridlike pattern in pictures on LCD and DLP projection TVs from the control circuitry surrounding the individual pixels in an LCD or DLP chip, which becomes visible when the image is blown up to a large size. SDTV: see standard-definition TV. SDTV monitor: A TV set that can display a 480i-format standard-definition digital TV signal when connected to an outboard tuner/decoder. SECAM (sequential coulour avec mémoire): The broadcast TV standard in France and much of the former Eastern Bloc; see PAL and NTSC. Secure Digital (SD) card: A flash-memory format supported by Toshiba, Panasonic, and others. sensitivity: A speaker measurement that tells how much sound, expressed as sound-pressure level (or SPL) in decibels (dB), is produced at a specified distance (usually 1 meter) from the speaker when it is fed a specified input signal (usually 2.83 volts, equivalent to 1 watt into 8 ohms). A speaker that is 3 dB more sensitive than another requires only half as much amplifier power to deliver the same playback volume. separation: see channel separation. Serial Copy Management System (SCMS): Incorporated in all consumer digital audio recorders to limit digital-to-digital copying of copyrighted music to a single generation. Any number of first-generation digital copies can be made from a digital original, but the resulting copies cannot themselves be copied via a direct digital link. server: Any hard-disk-based device that makes stored data available to other devices, often through a wired or wireless network; see client, media server. servo: Short for servomechanism, a negative-feedback control system that uses an output signal as feedback, comparing it to a reference signal; the difference between them is used to correct the output; a servomechanism is sometimes used in powered speakers to reduce distortion. set-top box: Still commonly used for several types of outboard decoder — such as for cable TV, digital TV, or Internet functions — designed for hookup to a TV set, though it’s less and less appropriate as TVs get slimmer. 7.1-channel: A 6.1-channel system where a recorded back surround channel is reproduced by two speakers, usually with individual amplification. Strictly speaking, however, unless additional processing is applied to send a different signal to each speaker, it’s still one channel in surround sound terms. shadow mask: A sheet of metal perforated with thousands of tiny holes that are aligned with the phosphor patterns within a color CRT; the purpose is to prevent the electron beam for one color from hitting the phosphors of another. See aperture grille. sharpness control: A TV control that affects the middle to high frequencies of the luminance signal, which convey the subjective impression of sharpness. shotgun microphone: A long, tubular microphone that is highly sensitive in the direction its tip is pointed and strongly rejects sounds from the side and rear; most often sold as a camcorder accessory; see cardioid microphone, omnidirectional. shutter speed: Since camcorders don’t have mechanical shutters, this refers to the length of time the image sensor is exposed to the image before its contents are read out. signal: An electromagnetic wave, current, or voltage whose variations carry audio or video information. signal processor: A component that manipulates line-level audio signals; equalizers and surround sound processors are the most common varieties. signal-to-noise ratio (S/N or SNR): Measured in decibels (dB), the difference in level between a signal (usually at a standard level) and the residual noise of the component through which it is passed; higher numbers are better. 6.1-channel: Any system that has provisions for a back surround channel, reproduced by one or two speakers centered behind the listening position, in addition to the conventional left and right surround channels of a 5.1-channel system; see 7.1-channel. 16:9, 16x9: The shape of a widescreen TV, as called for by the HDTV standard; see aspect ratio. slew rate: The rate at which a signal changes amplitude, or the maximum rate at which an amplifier can change the amplitude of its output; usually expressed in volts per microsecond. slope: The rate at which a filter or crossover rolls off out-of-band frequencies, in decibels per octave. Typical slopes are 6, 12, 18, and 24 dB/octave, which are also referred to as first- through fourth-order filters, respectively; the higher the order, the faster the rolloff. SmartMedia card: A flash-memory format used in many MP3 players and digital still cameras. solid-state: Electronic circuits whose active elements are transistors and integrated circuits, and specifically not vacuum tubes. Sony Dynamic Digital Sound (SDDS): A multichannel audio reproduction system for movie theaters utilizing ATRAC encoding and featuring as many as five front channels along with two surround channels and an LFE channel. Sony/Philips Digital Interface (SPDIF): The standard format for exchanging digital audio signals (whether mono, stereo, or multichannel) between consumer audio components. Connections can be coaxial (usually RCA) or optical (usually Toslink). sound-pressure level (SPL): A measure of physical loudness, usually encountered in speaker sensitivity ratings; expressed in decibels. soundstage: The virtual space created by an audio system; either the imaging of a stereo pair of speakers at the front of a room or the three-dimensional sound field created by all of the speakers in a multichannel home theater system. (Of course, the original soundstage is the real space where a movie soundtrack is recorded.) speaker (or loudspeaker): A component that accepts audio signals from a receiver or amplifier and converts them into sound waves for listening at some distance (unlike headphones); see driver. speaker-level: Audio signals that have been sufficiently amplified to drive a speaker; see line-level. specification (spec): A manufacturer’s numerical rating of a component’s performance in terms of a discrete, measurable characteristic such as frequency response or distortion. spectrum: The distribution of energy vs. frequency in a signal, commonly shown in a graph with level in decibels (dB) on the vertical axis and frequency in hertz (Hz) on the horizontal. standard-definition TV (SDTV): A subset of the digital TV (DTV) standard covering digital signals that will yield picture quality at least as good as that of analog NTSC television; see high-definition TV (HDTV) and enhanced-definition TV (EDTV). ST (AT&T ST) connection: A fiber-optic digital audio connector that uses glass fibers rather than plastic; see Toslink. stereo: The use of two or more audio channels to provide spatial realism or directional effects; nowadays “stereo” usually refers only to two-channel programs, equipment, or systems. See imaging, binaural, multichannel. streaming media: Digital audio or video data downloaded from the Internet or from a computer on a home network for simultaneous decoding and playback. subsonic filter: Commonly used instead of the more technically correct infrasonic filter. subwoofer: A speaker designed to reproduce only low-bass frequencies. A powered subwoofer contains an amplifier and an electronic crossover. Super Audio CD (SACD): A high-density audio disc that uses Direct Stream Digital (DSD) audio encoding to support a wider bandwidth and dynamic range than CD as well as up to six channels. “Hybrid” SACD pressings can be played on both SACD and standard CD players. supertweeter: A tweeter used to reproduce only extremely high frequencies. Super VHS (S-VHS): A development of the VHS videocassette system that originally required special tape to obtain its greater picture detail. surround: Channels or speakers in a multichannel audio system whose purpose is to create a sense of sonic envelopment or all-around directionality. Also a compliant suspension at the outer edge of a speaker driver’s diaphragm. surround sound: A reproduced sound field that is three-dimensional instead of a soundstage heard primarily in front of the listener; an audio system or part of a home theater system that creates such a sound field. See 5.1-channel, 6.1-channel, Dolby Digital, Dolby Surround, Dolby Surround EX, Dolby Pro Logic, DTS, DTS-ES, home theater, and THX. S-video: A connector that separately carries the luminance and chrominance information for a single video signal; a set of video signals divided into luminance and chrominance components. SXRD (Silicon Crystal Reflective Display): Sony’s reflective liquid-crystal technology used in high-resolution TVs; a variant of LCoS (liquid crystal on silicon). sync: That part of a video signal that tells a video component what part of the picture is being processed. Sync signals are usually carried along with the luminance (light/dark) information except in computer video signals and some wideband component video, where they are completely separate; see red, green, and blue (RGB). Abbreviations |
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