Resource Center: How to Speak A/V
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Entries starting with: AAC (Advanced Audio Coding): An increasingly used audio codec for downloaded music files (such as from Apple’s iTunes Music Store), streaming-media, and satellite-radio applications; see codec. access point: A transmitter/receiver that allows wireless devices to connect to a wired local-area network, or LAN. accessory shoe: A connector on the top of a camcorder that can hold a floodlamp, an external microphone, or other accessories. acoustical treatment: Measures to absorb or diffuse sonic reflections from room surfaces that can cause uneven bass response or muddy the sonic image. acoustic-suspension: A speaker enclosure design that uses the air trapped inside a sealed cabinet to help control woofer motion; see infinite-baffle. active crossover: An electronic component that divides the audio signal from a source component into frequency bands (low and high, for example) before each band is separately amplified. active scan lines: Scan lines in a video frame that carry picture information rather than being used for other data (such as closed captioning) or for synchronization. adjacent-channel selectivity: A measure of how well an FM tuner rejects signals from stations one channel up or down (0.2 MHz away) from the tuned frequency; higher figures are better. AES/EBU interface: The professional standard for transmitting digital audio signals between components, jointly specified by the Audio Engineering Society (AES) and the European Broadcasting Union (EBU). alternate-channel selectivity: A measure of how well an FM tuner rejects signals from stations two channels (0.4 MHz) away from the tuned frequency; higher figures are better. ambience: The acoustical character of a listening or performing space, determined mainly by the timing, level, frequency balance, and directions of the sound reflections in it. Some digital signal processors can synthesize ambience by generating artificial reflections. AM rejection: A measure of a tuner’s ability to ignore changes in an FM signal’s amplitude (level) caused by multipath and other types of interference; higher figures are better. ampere (A, amp): The primary unit of electrical current, which is the rate of flow of electrical charges. amplifier: A separate component, or a section built into an integrated component, that strengthens the electrical signal (increases its amplitude). A power amplifier, which is designed to drive speakers, must be connected to a preamplifier (or “control amplifier”) to switch signals and process the sound. amplitude modulation (AM): A technique used for analog radio and TV broadcasting in which the audio or video signal is conveyed by varying the the amplitude (level) of a high-frequency carrier wave. analog: A type of component or recording medium that represents changing physical values — like the point-to-point brightness in an image or the moment-to-moment variation of air pressure in a sound — by a continuously varying signal, such as a video or audio waveform; see digital. analog-to-digital (A/D) converter (or ADC): An electronic circuit that converts an analog electrical signal into a digital signal, or sequence of binary numbers. anamorphic: A means of recording a widescreen image using special lenses or processing such that the image is distorted in the storage medium, like a DVD, but restored to proper proportions during playback. aperture: In a video camera, an adjustable opening in the optical pathway that controls both the amount of light reaching the image sensor and the image’s depth of field. aperture grille: In a TV’s color picture tube, a type of shadow mask consisting of a metal sheet with thin vertical openings (instead of round holes) that are aligned with the red, green, and blue phosphors coating the inside face of the screen. artifact: An audio or video distortion introduced during digital encoding or decoding; in video, blocking and mosquito noise are the most common artifacts. aspect ratio: The ratio of width to height of a screen or image; expressed in whole numbers (4:3, 16:9) or divided out (1.33, 1.78). Conventional TVs have a squarish 4:3 shape, while newer HDTVs are 16:9 widescreen. assemble edit: An editing process used with camcorders and write-once DVDs in which a new program segment is added to the end of an existing segment; see insert edit. ATRAC (Adaptive TRansform Acoustic Coding): The codec used in the MiniDisc (MD) format as well as in Sony’s SDDS theater sound system; see codec. MD equipment that supports the long-play MDLP option also uses the newer ATRAC3 codec, as do Sony’s NetMD players, and it is incorporated in RealAudio 8 streaming media when that codec is operated at certain bit rates. ATSC (Advanced Television Systems Committee): The industry/government body that issued the U.S. digital TV standard. attenuate: To reduce or lower a signal’s strength. Audible: An Internet spoken-word format for computers and portable players that also play MP3 files. autofocus: A camcorder subsystem that focuses the image without user intervention by moving the focusing elements of the lens. aux (auxiliary): An input that can be used to connect line-level source components; also, any general-purpose A/V input. A-weighted (A-wtd): A standard equalization curve applied in sound-level meters and signal-to-noise ratio (S/N) measurements to make the readings conform more closely with perceived loudness, particularly at low levels, since human hearing is not equally sensitive at all levels and frequencies. Abbreviations |
