|What is AVI?|
We all know about Avi and how it is a video format and so on and so forth. We have so many avi format video files on our computers, but how many of us know what the full form of avi is? AVI is an acronym for Audio Video Interleave. This is basically a multimedia container format and was first released by software giant Microsoft in November 1992. This format was part of a larger package which was called "Video for Windows". As the name goes, the files of avi format can have both video as well as audio data within the space of a single file. This basically means that there can be a synchronized playback of both audio and video at the same. The avi format is like the DVD video format which allow a multiple streaming of data from both audio and video. The file format extensions have been developed by the Matrox OpenDML group in 1996. These are the files which are supported by Microsoft and are called AVI 2.0.
AVI is derived from the Research Interchange File Format or the RIFF. This breaks up a file into blocks or chunks. Each of the data chunk has a FourCC tag. Any avi file is a chunk of the RIFF file and has two further divisions of two chunks and one optional chunk.
Among the chunks of the data, the first chunk has a “hdrl” tag. This sub-chunk is also the file header and has metadata about the video. This data includes width, height, frame rate and so on. There is the second sub chunk and this has the “movi” tag. This has all the important audio as well as the video data which goes in to the components of the AVI movie. Then comes the last optional sub-chunk which has the “idx1” tag. This is the indexing component which indexes the offsets of the data chunks inside the AVI file.
There are certain issues with the AVI files and this is especially prominent when it is being used with codecs like Xvid and DivX. This is because there is an unnecessary increase in the size of the file. Then another point is the fact that the AVI container file cannot support the modern features like B-Frames which are generally associated with MPEG-4 files. At times, hacks are utilized for the MPEG-4 subtitles and so on. But there are many problems which do occur. Then again. The AVI files do not have pixel ratio aspect information. Thus what happens is when the file is played it seems as if the frames are being stretched or maybe squeezed on a horizontal basis. There are other formats like QuickTime, Matroska, Ogg and MP4 and these are much more adaptable than the AVI files.