UNIV4VINU | ENGINEERING ACHIEVERS

B.E, B.Tech.DEGREE EXAMINATION, May/June 2009

Fourth Semester

Information Technology

IT1251 – INFORMATION CODING TECHNIQUES

PART-A(10x2=20 marks)

1. What is the average information or entropy?

2. State channel coding theorem

3. Explain subband coding for speech signals

4. Write the condition required to avoid the slope overload distortion in delta modulation?

5. Why are cyclic codes well suited for error detection?

6. Give the syndrome properties of linear block codes?

7. Explain Run length encoding.

8. How is arithmetic coding advantageous over Huffman coding for text compression.

9. What is Dolby-AC1?

10. What do you understand by frequency masking?

PART-B(5x16=80 marks)

11.a.A discrete memory less source has the following symbols with probability of occurrence as shown below

Symbol s0 s1 s2 s3 s4 s5 s6

Probability 0.125 0.0625 0.25 0.0625 0.125 0.125 0.25

I) Generate the Huffman code with minimum code variance

ii) Determine the code variance and code efficiency

iii) Comment on code efficiency

(OR)

b.A discrete memory less source has an alphabet of five symbols with their Probabilities for its output is given below:

X=(X1, X2, X3, X4, X5)

P(X) = (0.45, 0.15, 0.15, 0.15)

Compute two different Huffman codes for this source. For these two codes find:

i)Average code word length

ii) Variance of Average code word length over the ensemble of source symbol

12. a.With the block diagram explain DPCM system. Compare DPCM system with PCM and DM system.

(OR)

b. With the block diagram explain the transmitter and receiver of Pulse code modulation.

13. a.Verify whether g(x)=1+x+x²+x⁴ is a valid generator polynomial for generating a cyclic code for message[111]

(OR)

b.A convolution encoder is defined by the following generator polynomial

g₀(x)=1+x+x²+x³+x⁴

g₁(x)= 1+x+ x³+x⁴

g₂(x)= 1+ x²+ x⁴

i)What is the constraint length of this code?

ii) How many states are in the trellis diagram of this code?

iii) What is the code rate of this code?

14) a)i)Draw the JPEG encoder schematic and explain

ii) In the context of compressions for text, image audio and video which of the compression techniques are suitable and why?

(OR)

b) With the following symbols and their probability of occurrence, encode the message “went” using arithmetic coding algorithms, Compare arithmetic coding with Huffman coding principles.

Symbol : 0 n t w #

Probability : 0.3 0.3 0.2 0.1 0.1

15) a)Explain the Linear Predictive Coding(LPC) model of analysis and synthesis of speech signal.State the advantages of coding speech signal at low bit rates.

(OR)

b) Discuss in detail the following audio coders

i) MPEG audio coders