Video Guide Part 3: Video Formats and Compression Methods

The AVI Format

One of the oldest formats in the x86 computer world is AVI. The abbreviation 'AVI' stands for 'Audio Video Interlaced'. This video format was created by Microsoft, which was introduced along with Windows 3.1. AVI, the proprietary format of Microsoft's "Video for Windows" application, merely provides a framework for various compression algorithms such as Cinepak, Intel Indeo, Microsoft Video 1, Clear Video or IVI. In its first version, AVI supported a maximum resolution of 160 x 120 pixels with a refresh rate of 15 frames per second. The format attained widespread popularity, as the first video editing systems and software appeared that used AVI by default. Examples of such editing boards included Fast's AV Master and Miro/Pinnacle's DC10 to DC50. However, there were a number of restrictions: for example, an AVI video that had been processed using an AV Master could not be directly processed using an interface board from Miro/Pinnacle. The manufacturers adapted the open AVI format according to their own requirements. AVI is subject to additional restrictions under Windows 95, which make professional work at higher resolutions more difficult. For example, the maximum file size under the FAT16 file system is 2 GB. The FAT32 file system (came with OSR2 and Windows 98) brought an improvement: in connection with the latest DirectX6 module 'DirectShow', files with a size of 8 GB can (at least in theory) be created. In practice however, many interface cards lack the corresponding driver support so that Windows NT 4.0 and NTFS are strongly recommended. Despite its age and numerous problems, the AVI format is still used in semi-professional video editing cards. Many TV cards and graphic boards with a video input also use the AVI format. These are able to grab video clips at low resolutions (mostly 320 x 240 pixels).

Apple's Format

The MOV format which originated in the Macintosh world, was also ported to x86 based PC's. It is the proprietary standard of Apple's Quicktime application that simultaneously stores audio and video data. Between 1993 and 1995, Quicktime was superior to Microsoft's AVI format in both functionality and quality. The functionality of the latest generation (Quicktime 4.0) also includes the streaming of Internet videos (the realtime transmission of videos without the need to first download the entire file to the computer). Despite this, Apple's proprietary format is continually losing popularity with the increasing use of MPEG. Video clips coded with Apple's format are still found on some CD's because of Quicktime's ability to run on both Macintosh and x86 computers.