Video Compression and Streaming

" Digital video is having a significant impact on a variety of industries, from broadcast to multimedia. As commonplace as digital video is, it is often misunderstood and misrepresented. Terms like AVI, Quicktime, and MPEG are thrown around interchangeably without regard to the differences between these formats."
Streaming video is a term often heard when discussing the Internet. The advent of high speed connections to the Internet has allowed developers to design for Video delivery over the Internet. An ever expanding range of software, hardware and content is available to expand the viewing of Video over the 'net. When you view Video via a network connection, or Stream it, you never have a copy of it on your computer. This makes possible the viewing of very long or live events. The main difference between Streaming Video and other types of Video which you view on a computer screen, Digital Video, is the ability for player software designed for Streaming Video to begin playing the file you wish to see without downloading it. While all Digital Video is made viewable via some type of compression, streaming video is often the most highly compressed. "While the various forms of digital video look similar to the end user, each format has idiosyncrasies that make it more suitable for some purposes and completely inappropriate for others. "

" To appreciate the differences between digital video formats, you must realize the challenges they try to address. Digital video without audio is captured at about 640 x 480 pixels per frame. Each frame has 307,200 pixels that can be any one of 16.7 million colors. This means that a single frame of video is almost 1 MB. Video is displayed at 30 frames per second. Consequently, without compression, the computer must store, transfer, and display more than 1.5GB for a single minute of video. At these rates, uncompressed digital video is neither practical nor portable without high-end equipment. "
Television skirts the issue of moving the Video around as large single files by using a method of displaying the picture by tracing a single horizontal line out of many hundreds one line at a time across the screen from left to right and top to bottom . But it does so at the rate of 1/30th of a second each. This fools the eye into thinking that the image is complete at all times. Computers do not display images that way. They shoot an image at the screen all at once all over the screen. This means a lot of information has to move through the computer and be waiting at the monitor ready to be blasted out all at once. Developers have countered this by using compression technology to lessen the size of the Video file to be displayed on a computer screen. Video Compression defined is the resaving of a file with the intent being to reduce the actually amount of data while retaining a large amount of the necessary visual data. Essentially all compression schemes, and there are many, use the same concept. They throw away redundant visual information.

" There are several compression schemes designed to reduce the size of digital video and to reduce the throughput requirements. Compression methods target the same basic areas: frame size, frame rate, image quality, and file storage. Digital video files are compressed for storage and then decompressed for playback. The method of compression and decompression is a CODEC. Various CODECs have been developed to address the many needs of digital video users."