Compression ha C Oxford Engineering College S2

8/3/2019 Compression ha C Oxford Engineering College S2

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Session 2Session Name: CompressionAuthor Nam e: C. Jaya pritha

Dep artment: Informa tion Tec hnolog y

Subjec t/ Course: Graphics and Multimed ia

Compression Techniques


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Page 2 Ver: 1.0 CompressionC.Jayapritha, Oxford Engineering College

Session Objec tives

At the end of this session, the learner will be ab le to :

Define the term com pression.

List the needs of compression and its types.

Expla in the c om pression standards.

Disc uss the d ifferent typ es of com pression techniques.

Tea c hing Learning Ma terial

Boa rd a nd C halk

Slide Presentation


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C.Jayapritha,Oxford Engineering College

Session Plan

Time(in min)

Content MethodologyFaculty

ApproachTypical Student

Activity

Learning

Outcomes(Blooms +

Gardeners)

05Introduction toCompression

Brainstorming Facilitates Participates

Remembering

LinguisticIntrapersonal

Interpersonal Skills

10Need for

Compression and itsTypes

Chalk and Talk Explains Listens

RememberingUnderstanding

InterpersonalIntrapersonal Skills

15CompressionStandards

Innovative Quiz Facilitates Participates

Applying

LogicalVerbal

InterpersonalIntrapersonal Skills

15CompressionTechniques

Demonstration DemonstratesListens

UnderstandingApplying

LogicalInterpersonalIntrapersonal

Visual

10 ConclusionChoose and

DefendFacilitates

GuidesParticipates

Remembering

LinguisticInterpersonalIntrapersonal

LogicalVerbal


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Session Inputs

Introduc tion to Compression

We can start this session by introducing the concept of

compression to the learners with the help of a Brainstorming

activity.

Suggested Activity: Brainstorming

The lea rners ma y not know anything abo ut c om pression te chniques but

they might know the meaning for the w ord com pression .

Additionally, some of them may have some extra knowledge on the

subject. Here, we can use the brainstorming method to extract the

responses from the learners. Reponses from the learners can be listed on

the boa rd. Then, we can ref ine the responses and the irre levant responses

can be d ismissed with a reason.

Partic ipant 1: Red uc ing the a mount

Partic ipant 2: Dec reasing the size

Partic ipant 3: Compa c tionPartic ipant 4: If we a re sta rting our motor cyc le, the ac tion of c om pression,

the red uc tion in vo lume a nd inc rea se of p ressure of the a ir or com bustib le

mixture in the cylinder prior to ignition, produced by the motion of the

p iston tow ards the c ylinder head a fter intake.

Partic ipant 5: The cod ing o f da ta to save storag e space or transmission

time.

Participant 6: A pump or other machine for reducing volume and

inc reasing pressure o f g ases.

Partic ipant 7: Run leng th enc od ingParticipant 8: A transducer that produces an output with a range of

voltages.

Participant 9: Algo rithm s

Participant 10: Prog rams


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Data compression or source coding is the process of encoding

information using fewer bits through the use of specific encoding

schem es which a re de cod ed in the rec eiver side.

Need for Compression a nd its Types

Having d isc ussed the c onc ep t of c om pression, we c an now

expla in the types of c om pression a nd the need for it to the

learners.

Need for Compression

1. Co mpression is the reduc tion in size of da ta in order to savespace or transmission time.

2. It helps reduce the consumption of expensive resources,such as hard disk space or transmission bandwidth, i.e., to

red uce the a mount of data storag e.

3. It c an a lso red uce the cost for transmission.4. Compression is used to manage large amount of

multimed ia da ta effic iently.

5. Compression is used to rem ove the red unda nc ies.Typ es of Compression

There are two types of com pression. They are:

1. Lossless compression2. Lossy compression

Lossless compression:

In this type, compression can be done without any loss of data.

This is mostly app lied for te xt d oc uments.

Lossy com pression:

In this type, while performing compression some of the data will

be lost.

Lossy image compression is used in digital cameras, to increase

storage cap ac ities w ith m inima l deg rad ation of p ic ture qua lity.

Sim ilarly, DVDs use the lossy MPEG-2 Video codec for video


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compression. Generally speaking, this compression technique isused for ima ges and videos.

Compression Standards

With the help o f the a bove d iscussion, we have ensured the

lea rners have und erstoo d the types of c ompression. Now, we c an

exp lain the com pression stand ards in a simp le way using the

innova tive quiz ac tivity.

Suggested Activity: Innovative Quiz

We can divide the learners into 4 groups. We can invite 2 volunteers to

conduct this quiz, one for asking questions and the other for marking

scores. The questions should b e p rep ared in suc h a way tha t it makes thelea rner think ab out the catego ry of the pa rticular forma t, or the type o f

com pression, e tc . By this method , lea rners will ac tively p artic ipa te and w ill

answer enthusiastically. Additionally, they will learn about different formats

ava ilab le. Fina lly, we c an c larify the ir doubts, if any.

Que stion 1: CCITT is app lied for wha t type o f doc uments?

Group 1: CCITT is app lied for text doc ume nts.

Que stion 2: Wha t typ e of c om pression is it?

Group 2: It is a typ e of lossless c ompression.

Question 3: Where is it actually used?

Group 4: It is mostly used in sending Fax documents.

Question 4: Ca n it be used for ima ge s? If yes, wha t typ e of ima ges?

Group 1: Yes, CC ITT can be used for b ina ry images.

Question 5: JPEG means?

Group 2: pass

Group 3: Joint Photographic Experts Group .

Que stion 6: What type o f doc ume nts it is used for?

Group 4: Pass

Group 1: It is used particularly for co lor ima ges.


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Que stion 7: Wha t typ e of c om pression is it?

Group 2: It is a typ e of lossy c ompression.

The important te rms d iscussed in the session are a s fo llows:

1. CCITT- Consultative C om mittee for Inte rnationa l Telephonyand Teleg raphy

For binary imageslossless compression that too in

text d ocuments

2. JPEG-Joint Photograp hic Expe rts GroupFor color ima ges-lossy c ompression

3. MPEG-Motion Pic tures Expe rt g roupFor videos-lossy c ompression

4. Gp3 Vide os-lossy compression

Com pression Tec hniques

After explaining about the c om pression standards, it w ould nowbe approp ria te to e xpla in the c om pression tec hniques with the

help of e xec ution o f a simp le program.

Sugg ested Ac tivity: Dem onstration

We can e xec ute a simp le prog ram for text com pression. The p rog ram c an

be executed in such a way that the repeated elements in the text are

rem oved and it is g iven a symb ol to rep resent the rep ea ted eleme nts. This

can b e app lied to the repea ted wo rd a lso. The wo rd w hich oc cur mo re

number of times can be given a symbol which will reduce the space

oc cup ied . This me thod c an be fo llowed for ima ge c om pression a lso.


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Program:

#include

#include

#include

#include

#include

void main()

{

FILE *f1,*f2;

int i=0,j=0,a=0,b=0,k,count=1;

char s[30],s2[30],s1[30],c[30];

clrscr();

printf("\n Enter the message");

scanf("%s",&s);

f1=fopen("Z:\INPUT.TXT","w");

while(s[i]!='\0')

{if(s[i]!=s[i+1])

{

if(count>=2)

{

s1[j+1]=s[i];

itoa(count,c,10);

s1[j++]='#';

s1[j++]=c[0];

if(count>9)

s1[j++]=c[i];

}

else

for(k=0;k


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c[1]='\0';

count=atoi(c);

for(k=0;k


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Group 1: No loss of data

Group 2: Even though there is loss, it will not affect the content in thedocument.

Group 1: But it c an a ffec t the qua lity of the p ic ture.

Group 2: As the images and videos occupy lot of memory space unlike

text, we ma y have to c om promise.

Group 1: Simple

To summarize , while performing lossy compression some o f the

data will be lost. Lossy image compression is used in digitalcameras, to increase storage capacities with minimal

degradation of picture quality. Similarly, DVDs use the lossy MPEG-

2 Video cod ec for video c om pression. Generally, this com pressiontec hnique is used for ima ges and videos.

Lossless compression can be executed without any loss of data.

This is mostly app lied for text doc uments.


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Summary

In this session, we lea rnt to :

Define the term com pression.

List the needs of compression and its types.

Expla in the c om pression standards.

Disc uss the d ifferent typ es of com pression techniques.


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Assignment

1. Take a text doc ument, define your ow n co mp ression fo rma t and try toapp ly that to the d oc ument. Then, convert your defined stand ard into

C code which should perform compression for any given text

document.

2. Take a b lack and white ima ge , tec hnic a lly a b inary ima ge and p utc hec ked lines in tha t ima ge . Now ma rk 1 for tha t particular check box

if it is in black color and 0 if it is white. Do it for the entire image. Nowwrite a C program which will accept your binary codes and should

rep roduce the ima ge .


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References

And leigh, P.K. and Thakrar, K., Multimed ia Systems and Design , Prentice

Ha ll of India , 2003.Jud ith Jeffc oa te, Multime dia in Prac tice: Tec hnolog y and Ap p lica tions ,

Prent ice Hall of India , 1998.

ht tp :/ / 59.163.61.3:8080/ GRATEST/ SHOWTEXFILE.do?p age_id=user_ima ge&u

ser_ima ge_id=2447

Compression ha C Oxford Engineering College S2

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