Digital Compression

"Digital Compression also called Compression, or Data Compaction, the process of reducing the amount of data needed for the storage or transmission of a given piece of information, typically by the use of encoding techniques."

Digital compression is used to reduce the amount of file space that is needed to store audio, video and data files. By changing the file size we can transmit or access data in a much more convenient manner. Digital compression allows files to be converted and accessed in less time than the original files would have allowed.

The most common use of digital compression is an audio compact disc. We can burn 74 minuets onto a compact disk, which is 640 megs of data. The data is compressed using a type of code called Pulse code modulation.

Digital compression is commonly used today. Just about everything, we listen to or view in media is digitally compressed. Compact discs are a digital media. The digital media is stored on this disc using a digital compression technique. MPEG 2 and MPEG 3 are the most common known forms of digital compression. These are followed by the latest format known as MPEG 4. "MPEG - Motion Picture Experts Group. A standards committee, supported by the ISO, formed to establish uniform methodologies and algorithms for digital audio and video compression."

MPEG 1 is 100:1 and is primarily meant for use only by computers. MPEG 2 however is the format that we start seeing more and more in media and can be used more often in many more applications. This compression rate is good for television broadcasting. MPEG 3 is commonly used in audio compressions for CD quality Audio and MPEG 4 is being used for DVD's

Currently MPEG 2 is the most common being used on websites, and on television. The ratio is an astonishing 19:39 Mbps. There are different bit rates that can be chosen to broadcast the signal. An uncompressed signal will output up to 270Mb per second. This why digital compression is so important so all that information can be squeezed together in to the least amount of space. MPEG 2 is the standard to accomplish this.

Of course video and audio are not the only things that we use that are compressed digitally. We also use digital compression to reduce file size on hard drives. Graphics are typically a large part of compression. You can have over 5000 graphic files on your hard drive and be completely out of space to save more files. By using programs such as win-zip you can compress those files into a folder and have twice as much space available to save more files.

Occasionally digital compression causes a drop out in your image or audio. This dropout can be significant and define the quality as being good or bad. One form of a drop out is something known as an artifact. A noticeable pixilation. The artifact could take the form of snow, noise, or a removal from a piece of the picture. When an artifact occurs in the compression is usually very noticeable to a trained eye.

A software program minimizes the amount of space a specific file will take up and compresses the information. There are programs that are used to convert a digital file from an analog source. This process is known as encoding. Stations that still tape on analog run all there programming through the encoding software to broadcast over their digital transmitters.

Data Compression." Encyclopædia Britannica. 2003. Encyclopædia Britannica Premium Service. 12 Sep, 2003 <http://www.britannica.com/eb/article?eu=2225>.
Semiconductor Service and Support, "Texas Instruments" 1995-2003 Texas Instruments Incorporated. All rights reserved. <http://www.ti.com/sc/docs/glossary/94056.htm>