Data compression introduction

DATA COMPRESSION

Rahul V. Khanwani

Roll No. 47

Department Of Computer Science

Introduction

• WinRaR

• Now A days data And Information Being A Major thing.

• The Data Compression Refers To the name Compress. It Means To compress The data And Utilize the System Space.

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Why To Utilize Space ?

• For Example • Similar Kind Of Starting Character In Database

– Amit. – Amin.

• Reducing Size Length

• Thus To Reduce Unnecessary Space We Need Data Compression.

A M I T

R A H U L


Need Of Data Compression

• To Reduce The Space:

– Compression of space Depends on Compression Technique

• Increase Channel bandwith:

– Send-Receive Data In Minimal Form

– Smaller Data Increase The Channel Bandwith

• Security:

– Compression Change The Original Value Of data.

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Types Of Data Compression 1. Lossless Compression

1. Shannon-Fano

2. Huffman

3. Lempel-Ziv (LZ)

4. Arithmetic Coding

5. Run Length Encoding

6. Burrows-Wheeler (BWT)

7. Deflate

2. Loosy Compression

1. Image

2. Audio

3. Video Rahul Khanvani For More Visit Binarybuzz.wordpress.com

Loosy data compression

• In this type of compression data which was compressed are not recovered properly.

• In this technique some part of data in range of time period is drop in short some part are cut from chain of data bits.


Lossless data compression

• In this compression technique after compression at recovery time x:-we will get data as we have before compression.

– Ex:- » Zip file


Terms Of Compression

• Coding – Describes the procedure defining the

transformation of symbols from one set of symbols to another one.

• Encoding – Process denotes the coding into a

particular destination format. – Converting Bitmap to JPEG

• Decoding – Process denotes the reverse process

related to Encoding – JPEG to Bitmap


Data compression an example

• Image Conversations: • RAW • BMP(bitmap image):

2.25MB • TTIF(tagged image file

format):1.65MB • PNG(Portable Network

Graphics):1.44MB • GIF(Graphic Interchange

Format):254KB • JPEG(Joint Photographic

Experts Group):291KB


DATA COMPRESSION TECHNIQUES


Shannon-Fano

Huffman

Lempel-Ziv (LZ)

Arithmetic Coding

Run Length Encoding

Burrows-Wheeler (BWT)

Deflate

1

2

3

4

5

6

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SHANNON-FANO

• Developed In 1960.

• Shannon–Fano coding, named after Claude Elwood Shannon and Robert Fano, is a technique for constructing a prefix code based on a set of symbols and their probabilities.

• Also Known As Variable Length Coding (VLC).

• Top Down Approach. Rahul Khanvani For More Visit Binarybuzz.wordpress.com

Shannon-Fano Algorithm 1. For a given list of symbols, develop a corresponding list of

probabilities or frequency counts.

2. Sort the lists of symbols according to frequency, with the most frequently occurring symbols at the left and the least common at the right.

3. Divide the list into two parts, with the total frequency counts of the left part being as close to the total of the right as possible.

4. The left part of the list is assigned the binary digit 0, and the right part is assigned the digit 1. This means that the codes for the symbols in the first part will all start with 0, and the codes in the second part will all start with 1.

5. Recursively apply the steps 3 and 4 to each of the two halves, subdividing groups and adding bits to the codes until each symbol has become a corresponding code leaf on the tree.


Example:

Symbol Count

A 15

B 7

C 6

D 6

E 5


Example:

Symbol Count Value

A 15 0

B 7 0

C 6 1

D 6 1

E 5 1

22

17


Example:

Symbol Count Value

A 15 00

C 6 1

D 6 1

E 5 1

B 7 01


Example:

Symbol Count Value

A 15 00

C 6 10

B 7 01

D 6 110

E 5 111


Example:

Symbol Count Value

A 15 00

C 6 10

B 7 01

D 6 11

E 5 11


Example:

Symbol Count Value

A 15 00

C 6 10

B 7 01

D 6 110

E 5 110

39


Conclusion

• Shannon–Fano is almost never used.

• Huffmam coding is almost as computationally simple and produces prefix codes that always achieve the lowest expected code word length.

• Shannon–Fano coding is used in the IMPLODE compression method, which is part of the ZIP file format, where it is desired to apply a simple algorithm with high performance and minimum requirements for programming.


THANK YOU


Data compression introduction

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