Video files

A video file is composed of several, time synchronized elements including video streams, audio streams, still images, titles, chapter information (for DVDs and Blue Ray disks), etc. This information is all collected in a video container file. AVI (Microsoft), RealMedia (Real), FLV (Adobe Flash), and MOV (Apple) are common video container formats.

The audio and video streams that are contained within the file are generally, though not always, compressed. The container will identify the compressor/decompressors (codecs) used to compress the audio and video. You must have the appropriate audio and video codecs installed on your computer to play or create a video.

Common container formats like MOV, AVI and Flash are proprietary -- they are developed and controlled by a private company. Ogg (OGM) is an open source container format. Ogg development is coordinated by the non-profit Xiph foundation, which has several related programs including vorbis, an audio codec, and Theora, a video codec.

Converting a media file from one format to another format or bit rate is called transcoding.

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