Data compression unit 5 mcq

Data compression unit 5 mcq 

1. Characteristic of a vector quantizer

(A) Multiple quantization indexes are represented by one codeword
(B) Each input symbol is represented by a fixed-length codeword
(C) Multiple input symbols are represented by one quantization index
(D) All of the above

Correct option is C

2. Vector quantization is rarely used in practical applications, why?

(A) The coding efficiency is the same as for scalar quantization
(B) The computational complexity, in particular for the encoding, is much higher than in scalar quantization and a large codebook needs to be stored
(C) It requires block Huffman coding of quantization indexes, which is very complex
(D) All of the above

Correct option is B

3. Let N represent the dimension of a vector quantizer. What statement about the performance of the best vector quantizer with dimension N is correct?

(A) For N approaching infinity, the quantizer performance asymptotically approaches the rate-distortion function (theoretical limit)
(B) By doubling the dimension N, the bit rate for the same distortion is halved
(C) The vector quantizer performance is independent of N
(D) All of the above

Correct option is A

4. Which of the following is/are correct for advantage of vector quantization over scalar quantization

(A) Vector Quantization can lower the average distortion with the number of reconstruction levels held constant
(B) Vector Quantization can reduce the number of reconstruction levels when distortion is held constant
(C) Vector Quantization is also more effective than Scalar Quantization When the source output values are not correlated
(D) All of the above

Correct option is D

5. Vector quantization is used for

(A) Lossy data compression
(B) Lossy data correction
(C) Pattern recognition
(D) All of the above

Correct option is D

6. The Linde–Buzo–Gray algorithm is a ______ quantization algorithm to derive a good codebook.

(A) Scalar
(B) Vector
(C) Both
(D) None of the above

Correct option is B

7. Vector quantization is used in

(A) Video coding
(B) Audio coding
(C) Speech coding
(D) All of the above

Correct option is C

8. What are process(Techniques) used in video coding?

(A) Partition of frames into macro blocks
(B) Form of Vector Quantization
(C) Both (A) & (B)
(D) None of these

Correct option is C

Data compression unit 4 mcq

 Data compression unit 4 mcq

 

1. Which of the following characterizes a quantizer

(A) Quantization results in a non-reversible loss of information
(B) A quantizer always produces uncorrelated output samples
(C) The output of a quantizer has the same entropy rate as the input
(D) None of the above

Correct option is A

2. What is the signal-to-noise ratio (SNR)?

(A) The ratio of the average squared value of the source output and the squared error of the source output
(B) The ratio of the average squared value of the source output and the mean squared error of the source output
(C) The ratio of the average squared value of the source output and the absolute difference measure of the source output
(D) None of the above

Correct option is B

3. The output signal of a scalar quantizer has property

(A) The output is a discrete signal with a finite symbol alphabet
(B) The output is a discrete signal with a countable symbol alphabet (but not necessarily a finite symbol alphabet)
(C) The output signal may be discrete or continuous
(D) None of the above

Correct option is B

4. What is a Lloyd quantizer?

(A) For a given source, the Lloyd quantizer is the best possible scalar quantizer in ratedistortion sense. That means, there does not exist any other scalar quantizer that yields a smaller distortion at the same rate.
(B) The output of a Lloyd quantizer is a discrete signal with a uniform pmf
(C) Both (A) and (B)
(D) A Lloyd quantizer is the scalar quantizer that yields the minimum distortion for a given source and a given number of quantization intervals.

Correct option is D

5. Which of the following statement is correct for comparing scalar quantization and vector quantization?

(A) Vector quantization improves the performance only for sources with memory. For iid sources, the best scalar quantizer has the same efficiency as the best vector quantizer
(B) Vector quantization does not improve the rate-distortion performance relative to scalar quantization, but it has a lower complexity
(C) By vector quantization we can always improve the rate-distortion performance relative to the best scalar quantizer
(D) All of the above

Correct option is C

6. If {x}_n is the source output and {y}_n is the reconstructed sequence, then the squared error measure is given by
(A) d(x, y) = (y - x)²
(B) d(x, y) = (x - y)²
(C) d(x, y) = (y + x)²
(D) d(x, y) = (x - y)⁴

Correct option is B

7. If {x}_n is the source output and {y}_n is the reconstructed sequence, then the absolute difference measure is given by
(A) d(x, y) = |y - x|
(B) d(x, y) = |x - y|
(C) d(x, y) = |y + x|
(D) d(x, y) = |x - y|²

Correct option is B

8. The process of representing a _______ possibly infinite set of values with a much _______ set is called quantization

(A) Large, smaller
(B) Smaller, large
(C) None of these

Correct option is A

9. The set of inputs and outputs of a quantizer can be
(A) Only scalars
(B) Only vectors
(C) Scalars or vectors
(D) None of these

Correct option is C

10. Which of the folowing is/are correct for uniform quantizer

(A) The simplest type of quantizer is the uniform quantizer
(B) All intervals are the same size in the uniform quantizer, except possibly for the two outer intervals
(C) The decision boundaries are spaced evenly
(D) All of the above

Correct option is D

11. If a Zero is assigned a decision level, then what is the type of quantizer?
(A) A midtread quantizer
(B) A midrise quantizer
(C) A midtreat quantizer
(D) None of the above

Correct option is B

12. If a Zero is assigned a quantization level, then what is the type of quantizer?

(A) A midtread quantizer
(B) A midrise quantizer
(C) A midtreat quantizer
(D) None of the above

Correct option is A

13. The main approaches to adapting the quantizer parameters:
(A) An off-line or forward adaptive approach
(B) An on-line or backward adaptive approach
(C) Both
(D) None of the above

Correct option is C

14. Uniform quantizer is also called as

(A) Low rise quantizer
(B) High rise quantizer
(C) Mid rise quantizer
(D) None of the above

Correct option is C

15. Non uniform quantizer ______ distortion.

(A) Decrease
(B) Increase
(C) Doesn't change
(D) None of the above

Correct option is A

16. The spectral density of white noise is ______.

(A) Poisson
(B) Exponential
(C) Uniform
(D) Gaussian

Correct option is C

 

Data compression unit 2 mcq

1. Huffman codes are ______ codes and are optimum for a given model (set of probabilities).
(A) Parity
(B) Prefix
(C) Convolutional code
(D) Block code

Correct option is B

2. The Huffman procedure is based on observations regarding optimum prefix codes, which is/are
(A) In an optimum code, symbols that occur more frequently (have a higher probability of occurrence) will have shorter codewords than symbols that occur less frequently.
(B) In an optimum code,thetwo symbolsthat occurleast frequently will havethe samelength
(C) Both (A) and (B)
(D) None of these

Correct option is C

3. The best algorithms for solving Huffman codes
(A) Brute force algorithm
(B) Divide and conquer algorithm
(C) Greedy algorithm
(D) Exhaustive search

4. How many printable characters does the ASCII character set consists of?

(A) 128
(B) 100
(C) 95
(D) 90

Correct option is C

5. The difference between the entropy and the average length of the Huffman code is called
(A) Rate
(B) Redundancy
(C) Power
(D) None of these

Correct option is B

6. Unit of redundancy is
(A) bits/second
(B) symbol/bits
(C) bits/symbol
(D) none of these

Correct option is C

7. The redundancy is zero when
(A) The probabilities are positive powers of two
(B) The probabilities are negative powers of two
(C) Both
(D) None of the above

Correct option is B

8. Which bit is reserved as a parity bit in an ASCII set?
(A) 6
(B) 5
(C) 8
(D) 7

Correct option is C

9. Bits are needed for standard encoding if the size of the character set is X
(A) X+1
(B) log(X)
(C) X²
(D) 2X

Correct option is B

10. In Huffman coding, data in a tree always occur in
(A) Leaves
(B) Roots
(C) Left sub trees
(D) None of these

Correct option is A

11. An optimal code will always be present in a full tree.
(A) True
(B) False

Correct option is A

12. Running time of the Huffman encoding algorithm is
(A) O(Nlog(C))
(B) O(Clog(C))
(C) O(C)
(D) O(log(C))

Correct option is B

13. Running time of the Huffman algorithm if its implementation of the priority queue is done using linked lists
(A) O(log(C))
(B) O(Clog(C))
(C) O(C²)
(D) O(C)

Correct option is C

14. The unary code for a positive integer n is simply n ___ followed by a ___.
(A) zero, ones
(B) ones, zero
(C) None of these

Correct option is B

15. The unary code for 4 is ______.
(A) 11100
(B) 11110
(C) 00001
(D) 00011

Correct option is B

16. In the Tunstall code, all codewords are of _____ length. However, each codeword represents a _________ number of letters.
(A) different, equal
(B) equal, different
(C) none of these

Correct option is B

17. Tunstall coding is a form of entropy coding used for
(A) Lossless data compression
(B) Lossy data compression
(C) Both
(D) None of these

Correct option is A

18. The main advantage of a Tunstall code is that
(A) Errors in codewords do not propagate
(B) Errors in codewords propagate
(C) The disparity between frequencies
(D) None of these

Correct option is A

19. Applications of Huffman Coding
(A) Text compression
(B) Audio compression
(C) Lossless image compression
(D) All of the above

Correct option is D

Data compression unit 1 mcq

Data compression unit 1 Mcq

1. Data compression means to ______ the file size.
(A) Increase
(B) Decrease
(C) Can't say
(D) None of the above

Correct option is B

2. Data compression and encryption both work on binary code.
(A) False
(B) True

Correct option is B

3. What is compression?
(A) To compress something by pressing it very hardly
(B) To minimize the time taken for a file to be downloaded
(C) To reduce the size of data to save space
(D) To convert one file to another

Correct option is C

4. Data compression usually works by _______.
(A) Deleting random bits data
(B) Finding repeating patterns

Correct option is B

5. Why data compressed?
(A) To optimise the data
(B) To reduce secondary storage space
(C) To reduce packet congestion on networks
(D) Both (B) and (C)

Correct option is D

6. Which is a type of data compression?
(A) Resolution
(B) Zipping
(C) Inputting
(D) Caching

Correct option is B

7. Data compression involves
(A) Compression only
(B) Reconstruction only
(C) Both compression and reconstruction
(D) None of the above

Correct option is C

8. Based on the requirements of reconstruction, data compression schemes can be divided into ____ broad classes.
(A) 3
(B) 4
(C) 2
(D) 5

Correct option is C

9. _______ compression is the method which eliminate the data which is not noticeable and _______ compression does not eliminate the data which is not noticeable.
(A) Lossless, lossy
(B) Lossy, lossless
(C) None of these

Correct option is B

10. ______ compression is generally used for applications that cannot tolerate any difference between the original and reconstructed data.
(A) Lossy
(B) Lossless
(C) Both
(D) None of these

Correct option is B

11. What is compression ratio?
(A) The ratio of the number of bits required to represent the data before compression to the number of bits required to represent the data after compression.
(B) The ratio of the number of bits required to represent the data after compression to the number of bits required to represent the data before compression.
(C) The ratio of the number of bits required to represent the data after reconstruction to the number of bits required to represent the data before compression.
(D) The ratio of the number of bits required to represent the data before reconstruction to the number of bits required to represent the data after reconstruction.

Correct option is A

12. Suppose storing an image made up of a square array of 256×256 pixels requires 65,536 bytes. The image is compressed and the compressed version requires 16,384 bytes. Then compression ratio is _______.
(A) 1:4
(B) 4:1
(C) 1:2
(D) 2:1

Correct option is B

13. Lossy techniques are generally used for the compression of data that originate as analog signals, such as
(A) Speech
(B) Video
(C) Both
(D) None of these

Correct option is C

14. If fidelity or quality of a reconstruction is _____, then the difference between the reconstruction and the original is ______.
(A) High, small
(B) Small, small
(C) High, high
(D) None of the above

Correct option is A

15. The development of data compression algorithms for a variety of data can be divided into ____ phases.
(A) 2
(B) 3
(C) 4
(D) 5

Correct option is A

16. Which of the following is true of lossy and lossless compression techniques?
(A) Lossless compression is only used in situations where lossy compression techniques can't be used
(B) Lossy compression is best suited for situations where some loss of detail is tolerable, especially if it will not be detectable by a human
(C) Both lossy and lossless compression techniques will result in some information being lost from the original file
(D) Neither lossy nor lossless compression can actually reduce the number of bits needed to represent a file

Correct option is B

17. Which of the following would not be suitable for Lossy Compression?
(A) Speech
(B) Video
(C) Text
(D) Image

Correct option is C

18. Which of the following are not in a compressed format?
(A) MP3
(B) Bitmap
(C) MPEG
(D) JPEG

Correct option is B

19. Information theory was given by
(A) Claude von Regan
(B) Claude Elwood Shannon
(C) Claude Monet
(D) Claude Debussy

Correct option is B

20. The unit of information depends on the base of the log. If we use log base 2, the unit is ____; if we use log base e, the unit is ____; and if we use log base 10, the unit is _____.

(A) Hartleys, nats, bits
(B) Hartleys, bits, nats
(C) Bits, nats, hartleys
(D) Bits, hartleys, nats

Correct option is C

21. According to Claude Elwood Shannon's second theorem, it is not feasible to transmit information over the channel with ______ error probability, although by using any coding technique.
(A) Large
(B) May be large or small
(C) Unpredictable
(D) Small

Correct option is D

22. The essential condition/s for a good error control coding technique?
(A) Better error correcting capability
(B) Maximum transfer of information in bits/sec
(C) Faster coding & decoding methods
(D) All of the above

Correct option is D

23. The prefix code is also called as
(A) Block code
(B) Convolutional code
(C) Parity code
(D) Instantaneous code

Correct option is D

24. Self information should be _____.
(A) Negative
(B) Positive
(C) Both
(D) None of these

Correct option is B

25. A code in which no codeword is a prefix to another codeword is called as
(A) Prefix cod
(B) Parity code
(C) Convolutional code
(D) Block code

Correct option is A

26. The set of binary sequences is called a _____, and the individual members of the set are called _______.
(A) Codewords, code
(B) Code, codewords
(C) None of these

Correct option is B

27. Full form of ASCII.
(A) American Standard Code for Information Intercaste
(B) American Standard Codewords for Information Interchange
(C) American Standard Code for Information Interchange
(D) American System Code for Information Interchange

Correct option is C

28. Composite source models is a combination or composition of several sources. In which how many source being active at any given time?
(A) All
(B) Only one
(C) Only the first three
(D) None of these

Correct option is B

29. For models used in lossless compression, we use a specific type of Markov process called a
(A) Continous time Markov chain
(B) Discrete-time Markov chain
(C) Constant time Markov chain
(D) None of the above

Correct option is B

30. Markov model is often used when developing coding algorithms for
(A) Speech
(B) Image
(C) Both
(D) None of these

Correct option is C