Data Compression Lec #1 (word) - 2019

Introduction
The last decade we have been witnessing a transformation—some call it a revolution—in the way we communicate, and the process is still under way. This transformation includes the ever-growing Internet; the explosive development of mobile communications; and the ever-increasing importance of video communication. Data compression is one of the enabling technologies for each of these aspects of the multimedia revolution.

So, what is data compression, and why do we need it? Most of you have heard of JPEG and MPEG, which are standards for representing images, video, and audio. Data compression algorithms are used in these standards to reduce the number of bits required to represent an image or a video sequence or music.

Data Compression
Data compression for (image, audio, video, text, or graphic) is the art or science of representing information in a compact form to reducing the size of the data. The primary goal of data compression is to reduce the file size. Compression is used just about everywhere for several reasons:

1) To save space when storing it.
2) To save time when transmitting it.

The task of compression consists of two components, an encoding algorithm that takes a message and generates a “compressed” representation and a decoding algorithm that reconstructs the original message or some approx¬imation of it from the compressed representation.

Types of data compression
There are two major families of compression techniques in terms of the possibility of reconstructing the original source. They are called Lossless and lossy compression.

Lossless compression
A compression approach is lossless only if it is possible to exactly reconstruct the original data from the compressed version. There is no loss of any information during the compression1 process. Lossless compression techniques are mostly applied to symbolic data such as character text, numeric data, computer source code and executable graphics and icons.