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What is AVI?

AVI, or Audio Video Interleave, is a multimedia container format. Developed by Microsoft in 1992, it is the most common format for audio and video data on a computer. AVI is actually a type of RIFF (Resource Interchange File Format), which divides a file’s data into chunks, or blocks, each chunk being identified by a FourCC tag.

In an AVI file, the first chunk is the header containing metadata about the video (its width, height, frame rate and so on); the second chunk contains the actual audio and video data making up the actual movie; and the third and final chunk indexes the physical addresses of the data chunks within the file. The first two are mandatory, while the third chunk is optional.

The audio and video data in an AVI file are stored next to each other. The audio data is stored uncompressed in PCM (Pulse Code Modulation) format in various parameters, while the video data is stored in compressed format with various codecs and parameters. The variety of codecs used in the files often becomes a problem. This is because the particular codecs used in producing the AVI files may be different from the codecs installed on the computer used in playback, thus making playback erroneous. Despite this drawback (which may be overcome by installing the right codecs), AVI files remain popular because of their high compatibility with the editing software VirtualDub and the playback software Windows Media Player.

Video clarity of AVI files (with file extension ‘.avi’) mostly depends on the codecs used, and the type and level of compression. Fidelity of the audio is mostly excellent, the options being the same as those for MP3 and WAVE.

AVI files may be opened on Windows with Windows Media Player, QuickTime Player, VLC media player, and Winamp; on Mac OS with Windows Media Player, QuickTime Player, and VLC media player; and on Linux with VLC media player and Xine multimedia player.


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