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AC Adapter: A circuit which modifies an AC current, usually converting it to a DC current. More info: AC Adapter
A/D Converter: A circuit which converts a signal from analogue to digital form; the opposite of a D/A converter. More info: A/D Converter
Adobe: A software manufacturer based in San Jose, California, and traded on the Nasdaq National Market under the symbol ADBE. Adobe is a leading provider of media productivity software. More info: Adobe Tutorials, Adobe Premiere, Adobe Photoshop, Adobe ImageReady
AGC: Automatic Gain Control. A circuit which automatically adjusts the input gain of a device, in order to provide a safe and consistent signal level. AGCs can be handy features, but professional applications often require manual gain control for optimum results.
Aliasing: Distortion of an image file or sound recording due to insufficient sampling or poor filtering. Aliased images appear as jagged edges, aliased audio produces a buzz. More info: Anti-aliasing
Alpha Channel: A special channel in some digital images reserved for transparency information. More info: Alpha Channel
AM: Amplitude Modulation. A method of radio transmission which sends information as variations of the amplitude of a carrier wave.
Amperage: The amount of electrical current transferred from one component to another.
Ambient: The environmental conditions, e.g. surrounding light and sound. More info: Ambient Sound, Ambient Light
Amplifier: A device which increases signal amplitude. More info : Amplifiers
Amplify: To increase amplitude.
Amplitude: The strength or power of a wave signal. The "height" of a wave when viewed as a standard x vs y graph.
Anamorphic Lens: A special type of wide-angle lens which stretches the width of the image but not the height, creating a widescreen aspect ratio. More info: Anamporhic
Analogue: Information stored or transmitted as a continuously variable signal (as opposed to digital, in which the analogue signal is represented as a series of discreet values). Analogue is often technically the more accurate representation of the original signal, but digital systems have numerous advantages which have tended to make them more popular (a classic example is vinyl records versus CDs).
Antenna: A device which radiates and/or receives electromagnetic waves.
Aperture: Literally means "opening". The camera iris; the opening which lets light through the lens. By adjusting the size of the aperture, the amount of incoming light is controlled. The aperture size is measured in f-stops. More info: Video exposure/iris
ASF: Windows Media file format ending with the extension .asf. Used for delivering streaming video. More info: ASF files
Aspect Ratio: The ratio of width to height of an image. Can be expressed as a number, or a relationship between two numbers. For example, the standard television screen ratio is 4:3 (4 units wide by 3 units high) or 1.33 (the width is 1.33 times the height). The new "wide screen" television ratio is 16:9 (1.78), and many new video cameras have the option to record using this format. Theatrical film aspect ratios vary, but the most common is 18.5:10 (1.85). More Info: Aspect Ratios
ASX: Windows Media file format ending with the extension .asx. This is a metafile which works in conjunction with ASF files for delivering streaming video. More info: ASX files
Attenuator: A device used to reduce the gain of a signal. Effectively the opposite of an amplifier. More info: Attenuators
Audio: Sound. Specifically, the range of frequencies which are perceptible by the human ear. More info: Audio tutorials
Audio Dub: The process of adding audio to a video recording without disturbing the pictures. The original audio may be replaced, or kept and combined with the new audio.
Audio Insert: A feature of some video equipment which allows audio dubbing.
Automatic functions: Functions which are performed by equipment with little or no input from the operator. Auto-functions can be very useful, but tend to have serious limitations. As a general rule, it is desirable to be able to operate audio-visual equipment manually.
Auxiliary Channel: On audio mixers, a bus which has an independent feed from each individual channel. Each channel has a control to adjust the level being sent to the auxiliary master output, which in turn has a control to adjust the overall level at the output bus. The auxiliary channel may be a simple output (to feed a device such as a tape machine or monitor), or it may be a "loop". An auxiliary loop sends a signal from the auxiliary output bus to a signal processing device such as a reverb generator, then brings the output of that device into an "auxiliary return" bus (thus creating a loop from the desk to the device, back to the desk). This return bus will have a level control pot, which is used to mix the incoming signal into the mixer's master output bus. More info: Auxiliary Channel
AVI: "Audio Video Interleaved". A common digital video format, in which the audio is interleaved as "packets", into the video frames.