Data Compression GTU Question IMP

1	Differentiate between lossy n lossless compressions.
2	Define search buffer and look ahead buffer’s use in LZ77 algorithm.
3	What is dictionary technique of compression? Explain its types.
4	Explain DCT with the help of an example.
5	Compare and contrast LZ77 and LZSS techniques.
6	Compare and contrast speech compression and text compression.
7	Write a note on silence compression.
8	Write a note on JPEG compression.
9	Explain LZSS algorithm.
10	How can we do lossless compression of sound? Explain various techniques.
11	Explain Adaptive coding.
12	What is Quantization? Why do we do quantization in JPEG compression?
13	Explain LZ77 algorithm and problems with it.
14	Explain LZ78 algorithm.
15	Explain balancing act with the help of example.
16	What is Arithmetic coding? How does it work explain with an example
17	What is Hoffman coding? explain with suitable example
18	Explain overflow problem with an suitable example
19	Explain the Practical matters and also List out the complication found in arithmetic coding
20	Define Data Compression. Mention advantages and disadvantages of data compression
21	Give difference between Huffman Coding and Shannon-Fano Coding
22	Check whether following code are uniquely decodable? a) { 0,11,01,111 } b) { 1,10,110,111 } c) { 0,01,110,111 }
23	Why Adaptive Huffman coding is preferred over Huffman coding? List out the enhancements
24	Generate Arithmetic Code for the following: p(y)=0.1, p(e)=0.2, p(r)=0.1, p(g)=0.1, p(n)=0.1 , p(m)=0.1 , p(a)=0.1 , p(f)=0.1, p(c)=0.1 and string is german
25	What is the underflow problem in arithmetic coding? How it is taken care of ?
26	What is the difference between lossless and lossy compression? How can be a compression algorithm is evaluated
27	What are the various applications of Huffman coding
28	Explain Adaptive Huffman Coding. How it is different from conventional Huffman Coding?
29	Write Short notes on the following: A)The Escape Symbol  B)Entropy
30	Consider source alphabet of A, B, C,………G,H having probabilities P(xi)=1/2, 1/4, 1/16, 1/16, 1/32, 1/32, 1/32, 1/32. Design the Huffman code. Calculate average length of code word and code efficiency?

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Generating Arithmetic Coding in DC

Description

The ‘coder’ object attached to this article can work box implementation of an arithmetic encoder. However, to use it, we used understand the basics of statistical modeling for arithmetic coding and  concepts of arithmetic coding.

In general, using arithmetic coding effects creating a statistical model of the data. In this example, I will assume that we are trying to encode the words “HELLO WORLD”.

Creating the statistical model of the data proceeds as follows:

1. Taking the number of independent characters in the words to be encoded (HELLO WORLD), we obtain, in alphabetical order:
1. D
2. E
3. H
4. L
5. 1. O
   2. R
   3. W
   The total number of characters to be encoded is 10. For convenience and clarity, I have ignored the space between the words HELLO and WORLD.
   2. We can arrange these characters into a table with their corresponding frequency, as below:

   Character	Frequency
   D	1
   E	1
   H	1
   L	3
   O	2
   R	1
   W	1

   1. Each of the characters will be assigned a range based on its frequency/ probability of occurrence. This range will be between 0 and 1, as below (note that I have not used any optimizations for the frequency and probability model; for the most optimal compression, this is necessary; however, for the purposes of our example, this should do).

   Character	Frequency	Probability	Range
   D	1	1/10	0.0 – 0.1
   E	1	1/10	0.1 – 0.2
   H	1	1/10	0.2 – 0.3
   L	3	3/10	0.3 – 0.6
   O	2	2/10	0.6 – 0.8
   R	1	1/10	0.8 – 0.9
   W	1	1/10	0.9 – 1.0

   2. The algorithm for encoding is as below:
   
   
   Set low to 0.0
   Set high to 1.0
   While there are still input symbols do
       get an input symbol
       code_range = high - low.
6. 1. The algorithm for decoding the number and retrieving the encoded string/data is as below:
   Find the symbol represented by the range that the number is in, output it. Remove the effects of encoding and repeat. In pseudo-code:

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