What is the AVI format?
The AVI format was invented by Microsoft more than twenty years ago, however, AVI is still one of the most popular formats for storing video information in the world.
For the first time, the AVI format appeared in November 1992 together with the innovative, for those times, the Windows 3.1 operating system, becoming the main one for storing video in Microsoft Windows operating systems. The abbreviation “AVI” stands for – Audio Video Interleave.
Unlike common formats like MP3 or JPG, AVI is a container that can contain compressed video / audio data using different codec combinations. So if MP3 and JPG files are based on using only the main type of data compression (compression) (MPEG Audio Layer 3 and JPEG), an AVI file can contain several types of compressed data (for example, DivX – video + WMA – audio or Indeo – video + PCM – audio), depending on the codec used for encoding / decoding. All AVI files look the same “on the outside” (they have the extension .AVI), but they can be very different “on the inside”.
Recording in AVI format can be done with or with compression. Motion JPEG is generally used to encode data in AVI. Compression formats are also supported: Microsoft Video 1 (the format works only with 8 and 16-bit color), Microsoft RLE (8-bit color only), Indeo, Cinepak Editable MPEG, which uses only I-frames.
Most of the time, data in the AVI container format is encoded and decoded using the DivX codec, which is a decrypted version of Microsoft’s MPEG-4 video codec.
All Windows operating system software players can understand and play AVI format.
Main disadvantages:
Lack of VBR support
Unfortunately, the AVI format does not support variable bit rate (VBR) audio streams. The developers of the AVI format managed to implement support for the variable bit rate of MP3 tracks, but it does not yet support sound in the Ogg Vorbis format.
Picture and sound out of sync The
Data in the AVI container is stored in the form of sequences of recordings, each consisting of a frame and the corresponding soundtrack. For video, the division into frames is completely natural, but the sound is a continuous stream, artificially divided into fragments corresponding to the frames. If a video capture device is used to record both video and sound, problems generally do not arise. However, if the sound is recorded via a sound card, there is no exact synchronization of the picture and sound, and the sound may “come out of the picture”.
