DG1: Digital Video Basics and Compression

Digital Video Basics
http://www.insanely-great.com/features/010625.html

There are many different kinds of digital video. Each type is encoded in a format designed to compress the video into a usable form. Some popular formats include DV, MPEG-1, MPEG-2, MPEG-4, QuickTime Video, Sorenson Video, Cinepak, M-JPEG and AVI. Each format has its specialized use, and some are better than others. We'll touch on some of the best video codecs for use in two classes of video compression. For our purposes we'll separate desktop video into three areas, video for TV, video for CD-ROM/Internet download and video for Internet streaming.
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by Michael Flaminio


Video Compression
http://www.insanely-great.com/features/010626.html

In its simplest form, video compression takes a series video images and optimizes them to contain the least amount of data possible. When video is compressed, data is removed from the video image that is considered unneeded.

For example, lets say you're drawing a cartoon and in the background there are two trees and a hill. To make the cartoon move, you'll need to animate objects by drawing variations of movement. While the main object moves, your background of trees and a hill do not. There's no need to continually redraw the background, so you can just copy it from frame to frame.
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by Michael Flaminio


Video Compression Technology
http://www.wave-report.com/tutorials/VC.htm

At its most basic level, compression is performed when an input video stream is analyzed and information that is indiscernible to the viewer is discarded. Each event is then assigned a code - commonly occurring events are assigned few bits and rare events will have codes more bits. These steps are commonly called signal analysis, quantization and variable length encoding respectively. There are four methods for compression, discrete cosine transform (DCT), vector quantization (VQ), fractal compression, and discrete wavelet transform (DWT).
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by Wave Report


Digital Video Compression Explained
http://www.microsoft.com/windowsxp/using/moviemaker/expert/digitalvideo.mspx

If you use digital video, file size is an important concern because digital video files tend to take up a lot of storage space on your hard drive. The answer is compression—making files smaller.

With text files, size is less important because the files are full of “spaces” and can be compressed very tightly—a text file can be made at least 90 percent smaller, resulting in a high compression ratio (the ratio of compressed data to uncompressed data). Other file types, like MPEG video or JPEG photos, hardly compress at all because they're in a format that's tightly compressed to begin with.

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by Jason R. Dunn