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Access control A means of protecting computer data from unauthorised access.Active Matrix A controller which allows the brightness and colour of every pixel on an image.ADSL An Asymmetrical Digital Subscriber Line can transmit at speeds of up to 7Mbps over a single copper pair.Algorithm A sequential, step-by-step, problem-solving procedure that can also determine how to decompress data.Aliasing Also often known as ‘twittering’, this is a problem associated with interlaced video sources and affects the sharp lines and edges during camera movement, causing objects to shimmer.ALIS Alternate Lighting of Surfaces is a method of achieving high definition and high brightnessAmbient light The level of lighting present in a room other than the light emitted by a projector.Analogue Analogue signals are the traditional format in which audio and video are transmitted. A digital signal will usually produce a superior video quality.ANSI American National Standards Institute.ANSI lumens The degree of lamp brightness, measured in candela.Aperture The hole behind a lens through which light is allowed to pass.API Application Programming Interface is the format used by an application to communicate with an operating system.Application Computer software designed for a specific purpose, from sending emails to viewing videos.Archive Data that has been stored in a format suitable for retrieval on demand.ASF Advanced Systems Format is a file format which enables digital media data to be streamed over a network. Active Streaming Format is the standard file format of WindowsMediaTM Technologies files.Aspect ratio The ratio of width to height of an image.Asynchronous Asynchronous refers to two or more signals which operate at different rates despite having the same nominal rates. ATM (Asynchronous Transfer Mode) is the CCITT standard for cell relay, where information for multiple types of services, including voice, video and data, is conveyed in small, fixed-size cells. ATM is used in both LAN and Wan environments.ATM layer This refers to the layer within the ATM protocol stack for routing and processing activities, including building the ATM header, payload identification, header validation and cell reception, cell routing using CPIs and VCIs, cell multiplexing and de-multiplexing, quality of service specification, prioritisation and flow control.Attenuation The loss of signal in a transmission system.Audio in and out Connections for external amplifiers and speakers to allow sound output.Authoring systems Entry level software solutions that help users develop interactive multimedia packages, particularly suited to training and education. Auto balance Automatic correction of errors in colour balance in black and white areas of an image.AVI Audio Video Interleave is a digital file format for developing and storing sound and video.
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