AVI is a multimedia container that is very popular among PC and Mac users. The format was developed by Microsoft in 1992. Usually AVI is used as a video format but unlike other formats of that time, AVI may contain both audio and video data compressed with a use of different combinations of codecs. More often such video codecs as DivX and XVID are used with .avi files. For audio playback such codecs as MP3, AC3 and PCM are used. It is possible to play AVI files with Windows Media Player or other similar programs.

MP4 is an extension defined by MPEG-4 video standard and AAC audio standard. It is a container that supports all kinds of media such as video, audio, subtitles, 2D and 3D graphics. It is possible to open MP4 file with almost any player on Windows but on Mac you should use a plug-in or just convert the file to another format.