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AVI File

AVI file extension is used by audiovisual container files in Audio Video Interleaved format. AVI format was introduced by Microsoft in 1992 as a reaction to Apple QuickTime technology which added digital video support to Macintosh platform. Initially AVI file format only supported video of 320 to 240 pixels with a maximum frame rate of 30 frames per second. With later iterations of AVI file format, support for more codecs and higher resolutions was added. At this moment AVI container format supports possibly the most codecs out of all audiovisual container formats. Also, AVI is one of the formats which is widely adopted by many hardware devices. Many DVD players and smart TVs (including older models) have AVI support.

If you need to open AVI file on Windows platforms all you need to do is to double click on it. By default, Windows Media Player is assigned to play AVI files on Windows. If you’re using Mac OS or Linux, you can download VLC Media Player for corresponding platform and use it to open AVI file.

Internally AVI file is based on Resource Interchange File Format (RIFF) specification. RIFF file consists of multiple chunks with a tag assigned to each of them. Typical RIFF chunks for AVI files are:

  • hdrl – AVI file header with metadata about the video like height, width and frame rate
  • movi – contains actual video and audio data
  • idx1 – offsets of the data chunks inside the RIFF file

Data contained in movi chunks is encoded or decoded by a specific codec. Thus the data format inside the movi chunk is not dependent on AVI file structure.

There are several issues with AVI file which prevent its wide adoption in the modern environments. These include: no standardized aspect ratio encoding, multiple incompatible ways to encode time codes, limited support of modern compression methods like MPEG-4, no variable bit rate support, significant overhead in storage.

To transfer AVI files over internet following Internet Media Types (formerly known as MIME types) are used:

  • video/vnd.avi
  • video/avi
  • audio/msvideo
  • audio/x-msvideo
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