Rajshahi University of Engineering & Technology

Department of Electronics and Telecommunication Engineering

Information Theory ETE 315

Submitted to –

Sham Datto

Lecturer : Dept. of ETE

Submitted by -

Hasan Sarkar

Roll: 114041

Content of information encoding:1. Source coding or bit-rate

reduction 2. Digital signal processing &3. Data compressions

Topics :

1. (a) Compression of information.

(b) information content of compressed

data &2. continuous amplitude signals.

1. Compression of information

WHAT IS COMPRESSION? Compression is the process of reducing the size of a

file by encoding its data information more efficiently.

the result is a reduction in the number of bits and bytes used to store the information.

In effect, a smaller file size is generated in order to achieve a faster transmission of electronic files and a smaller space required for its downloading.

Data without compression

Data with compression

Compression

technique

Why is data compression needed?

1. Data compression is needed because it allows the data to be stored in an area without taking up an unnecessary amount of space.

2. a smaller file size is generated in order to achieve a faster transmission and downloading.

3. It reduces redundant information by using different and more efficient ways of representing the information.

Types of data compression

According to Loss : 1. Lossless compression.

2. Lossy compression.

According to compression rate: 1. Low rate compression.

2. High rate compression.

Lossless compression : With lossless compression, every single bit of data that was originally in the file remains after the file is uncompressed.

Lossy compression : lossy compression reduces a file by permanently eliminating certain information, especially redundant information.

Low and high (quality) compression :

Low compression (high quality) High compression (low quality)

How does compression work ? When you have a file containing text, there can be repetitive

single words, word combinations and phrases Or there can be media such as high tech graphical images . To reduce this inefficiency electronically, you can compress the document.

Compression is done by using compression algorithms (formulae) that rearrange and reorganize data information so that it can be stored more economically.

By encoding information, data can be stored using fewer bits. This is done by using a compression/decompression program that alters the structure of the data temporarily for transporting, reformatting, archiving, saving, etc.

Methods may include simply removing space characters, using a single character to identify a string of repeated characters, or substituting smaller bit sequences for recurring characters.

Compression ratio : the size of the compressed file compared to that of the uncompressed file -

Video can be compressed immensely (e.g. 100:1) with little visible quality loss

Audio can often be compressed at 10:1 with imperceptible loss of quality

Still images are often lossily compressed at 10:1, as with audio, but the quality loss is more noticeable, especially on closer inspection.

Name of compressed file format :

.rar

.zip

.pf

.7z

.arc

.tar

.iso

Etc…………..

2. Continuous amplitude signalsWhat is continuous signals ? A continuous signal or a continuous-

time signal is a varying quantity whose domain, which is often time, is a continuum.

X = sin (t)

T= 0 pi

A typical example of an infinite duration signal is:

A finite duration counterpart of the above signal could be:

and   otherwise.

The value of a finite (or infinite) duration signal may or may not be finite. For example,

and   otherwise,

is a finite duration signal but it takes an infinite value for  .

Thank you all