Audio Video Interleave, or AVI, was the original video format for Windows. AVI files can be played on all Windows computers going back to Windows 3.1, and on many Macs as well, providing that the codec used to create the video is installed on the computer playing the video.
The “Microsoft MPEG-4 v2” codec offers the best combination of high quality, small file size and a large installation base.
AVIs can also be saved with lossless compression using the “Huffyuv” codec or with no compression. The lossless and no compression options are designed for storage (non-Internet) use.
DivX had a somewhat shady start as “DivX ;-) 3”, which is a hacked version of the Microsoft MPEG-4 v3 codec. Further, the installation of “DivX ;-) 3” usually overwrote the Microsoft MPEG-4 v1 and v2 codecs without warning. DivX 4 eventually came along, without any significant improvements, but it was legal. DivX 5 was the first major, legitimate DivX, with DivX 6.8 being the current release.
DivX is essentially an AVI codec, although DivX encoded AVIs can now use the .DIVX file extension. DivX creates high-quality files with small file sizes, but your audience must, of course, have the DivX codec installed.
DivX Profiles ensure playback on DivX certified hardware.
The term "keyframe" is used when creating animated video and when compressing both animated and real-life video. Depending on where the term is used, it has very different meanings. When creating animated videos, Keyframes are used to define frames where major transitions occur. Examples include changes in the position or color of objects and changes in camera position or angle. The animation program then draws (or “renders”) the frames in between the keyframes. The process of only having to draw keyframes makes animation and special effects projects manageable, in terms of time and both artist and computer resources.
The above animation, which contains 900 individual frames, was creating using just 14 keyframes. The rendering software created the remaining 886 frames without any human intervention.
Building on the success of the Joint Photographic Experts Group, developers of the JPG file format, the Moving Pictures Experts Group, created the MPG file format. MPG is the first major audio/video format based on an industry standard, and the first major audio/video format not to require that a particular codec be installed on a user’s computer in order to play a video.
MPG’s file quality is good, and although there are file formats that offer better compression, no file format has better compatibility. MPGs will play on just about any computer made since 1992, regardless of the operating system. MPEG-1 gave us the MPEG-1 Layer 3 (MP3) audio format
MPEG-2 is the format used to encode video for commercial DVDs. It’s not necessarily more effective than MPEG-1 at compressing video for Internet usage, nor was it really designed to be. MPEG-2 was designed specifically to compress video at very high-quality settings using storage media with a great deal of space available, such as optical disks.
Just as MPEG-1 introduced the MP3 audio format, MPEG-2 also makes available audio enhancements. These include multi-channel audio (such as Dolby Digital) and AAC (Advanced Audio Coding). Many encoders, including TMPGEnc (above), have profiles for creating DVD-quality MPG video.