Codec

Short for “coder/decoder,” a codec is essentially an algorithm for encoding (and compressing) a stream of data for transmission, and then decoding and decompressing it at the receiving end. Usually the data involved represents audio or video content. Typically the data is being downloaded from a Web site to be played on a personal computer or portable player. A codec is described as “lossy” if some of the original information is lost in the compression process. It then becomes a question of whether the loss in quality is perceived by the user as significant. A codec that preserves all the information needed to re-create the original file is “lossless.” For most purposes, the much greater size of the lossless version of a file is not worth the (often imperceptible) increase in quality or fidelity. A codec is usually used in connection with a “container format” that specifies how the encoded data is to be stored in a file. Often a container can hold more than one data stream and even more than one kind of media (such as video and audio). When one refers to a Windows WAV file, for example, one is actually referring to a container. Most of the popular codecs and file formats are proprietary, which creates something of a dilemma for users who prefer open-source solutions. However, while most Linux distributions do not include support for formats such as MP3 out of the box, distributions such as Ubuntu are now making it easier for users to choose nonsupported proprietary codecs if desired. The preceding table lists some codecs likely to be encountered by program developers and consumers.