.avi Video File Format
According to the Wikipedia page on the subject, the "Audio Video Interleave, known by its acronym AVI, is a multimedia container format introduced by Microsoft in November 1992 as part of its Video for Windows technology. AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback. AVI is a derivative of the Resource Interchange File Format (RIFF), which divides a file's data into blocks, or "chunks."
AVI chunks include:
- hdrl (file header chunk which contains information about the video's width, height and frame rate)
- movi (chunk containing the actual audio/visual data that make up the video)
- idx1 (optional chunk that indexes the offsets of the data chunks within the file)
AVI files use progressive encoding, which requires viewers to download a video file in its entirety before being able to view any of its content.
AVI files also use temporal compression, which reduces the amount of data stored within a sequence of frames by employing key frame technology. Rather than storing every pixel in each frame, temporal compression stores a key frame, the only the information which is changing between key frames. Quality of the footage can be significantly lower than progressive encoding formats as a result of temporal compression being used. Temporal compression also has the drawback of not allowing future editing of the file.
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