Video Compression

To digitize and store a IO-second clip of full-motion video in your computer requires transfer of an enormous amount of data in a very short amount of time. Reproducing just one frame of digital video component video at 2.4-bits requires almost 1MB of computer data; 30 seconds of video will fill a gigabyte hard disk. Full-size, full-motion video requires that the computer deliver data at about 30MB per second—this is simply more than Macintoshes and PCs can handle. Typical hard disk drives transfer data at only about 1MB per second, and quad-speed CD-ROM players at a paltry 600K per second. This overwhelming technological bottleneck is currently being overcome by digital video compression schemes or codecs (coders/decoders). A codec is the algorithm used to compress a video for delivery and then decode it in real-time for fast playback. Real-time video compression algorithms such as MPEG P*64, DVI/Indeo, JPEG, Cinepak, ClearVideo RealVideo, and VDOwave are now available to compress digital video information at rates that range from 50:1 to 200:1. JPEG, MPEG, and P*64 compression schemes use Discrete Cosine Transform (DCT), an encoding algorithm that quantifies the human eye's ability to detect color and image distortion. All of these codecs employ lossy compression algorithms.
In addition to compressing video data, steaming technologies are being implemented to provide reasonable quality low-bandwidth video on the Web. By starting playback of a video as soon as enough data have transferred to the user's computer to sustain this playback, users do not have to wait for an often very large file to download. Microsoft, RealNetworks, VXtreme, VDOnet, Xing, Precept, Cubic, Motorola, Vivo, Vosaic, and Oracle are actively pursuing the commercialization of streaming technology on the Web. RealNetworks (http://www.real.com) claims that by 1998 more than 28 million copies of its RealPlayer software had been downloaded electronically and more than 100,000 hours per week of live audio and video content were being broadcast over the Web using their RealAudio and RealVideo technology, and more than 150,000 Web pages were using RealNetworks’ streaming software. Tools such as Terran Interactive’s Media Cleaner Pro (http://www .terran-int.com) allow you to customize the move and audio compression chores and optimize your media for either CD-ROM or Web delivery.
QuickTime, Apple's software-based architecture for seamlessly integrating sound, animation, text. and video (data that change over time), is often thought of as a compression standard, but it is really much more than that.