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A device that converts analog signals to digital form for transmission and converts signals traveling in the opposite direction from digital to analog form. Derived from coder-decoder.



(1) (COder/DECoder) A hardware circuit that performs analog-to-digital conversion (ADC) and/or digital-to-analog (DAC) conversion. When a digital device receives analog signals from a microphone, VHS tape or other analog source, the ADC converts them to digital audio samples and video frames. Generally, the results are further compressed to save bandwidth (see definition #2).

(2) (COmpressor/DECompressor) Software and/or hardware that compresses digital audio and video data in order to reduce file size. Compressed files can be transmitted faster and stored in less space. For example, a song on a CD can be reduced to 10% of its original file size using MP3 compression (see MP3). The size of a movie/video file is dramatically reduced using various compression techniques (see video format).

Video formats generally use one codec, which may comprise several quality levels. "Container formats," such as Apple's QuickTime and Microsoft's AVI, support a variety of codecs (see container).

The goal of codec designers is to maintain audio and video quality while compressing the binary data further. Lossy methods are widely used, which actually discard bits that most people cannot hear or see. See lossy compression, codec examples, companding and codec switching.

(3) (COmpressor-DECompressor) A general data compression algorithm; for example, a "Zip codec." The term may also be applied to the built-in algorithms used to create and render images such as GIFs and JPEGs. See data compression.