Audio Video Interleave (AVI) is a means of digitally storing audio and video media content in a file for playback. Introduced in the early 1990s, the AVI format is a built-in feature of the Windows® computer operating system (OS). AVI-formatted files employ the file extension .avi, and are comprised of a header tag followed by a series of chunks of information. The header portion of the AVI-formatted file provides details about the file contents, such as width, height, and frame rate, while the chunks of information store the actual audio and video data. A key advantage of AVI format is its ability to be played on the majority of computers worldwide.
In order to play a media file of any format — including the AVI format — a compatible software program that understands the details of the file contents is required. When the appropriate software program is not available to open and play a media file, the user is presented with a message dialog stating that Windows® is unable to open the file. Options are then provided to enable the user to either select the program from a list of available software or use the Web to locate the program. The AVI format typically eliminates the need for program selection.
During the years since the inception of the AVI format, many video techniques have been introduced that were not conceived during the definition of the AVI specification. Additionally, the compression schemes used to optimize space requirements when writing AVI files is not as efficient as techniques employed in more recently developed media formats. As such, the AVI format requires approximately 5 megabytes (MB) of storage space for each hour of video and does not support the ability to specify media details, such as aspect ratio, time codes, or audio sample rates below 32 kilohertz (KHz).
Many newer media file formats are making their way around the Internet, including Ogg, MOV, and NUT. Motion Picture Experts Group (MPEG), however, is emerging as a default standard and is ever-increasing in popularity. Software programs to support the creation and playback of MPEG media files are included in both Windows® and Mac® operating systems.
