05-compression-02-entropy coding.pptx - ICSY

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Huffman Coding Evaluation } Limitations (cont.) • For a usual german text p("e") > p("h") is valid, but if the preceding characters have been "sc" then p("h") > p("e") is valid - (non-satisfying) solutions for both scenarios: • Solution: Use a special coding where "sch" is one character only. But this requires knowledge about frequent character combinations in advance. • Solution: use different huffman codes with respect to the context. But this leads to large code tables which must be appended to the coded data Prof. Dr. Paul Müller, University of Kaiserslautern 22
Arithmetic Coding } arithmetic coding generates codes that are optimal according to information theory - supports average code word length smaller than 1 - supports strings of different length } probability model is separated from encoding operation - probability model: • encoding strings and not single characters • assign "codeword" to each possible string • codeword consists of a half open subinterval of the interval [0,1] • subintervals for different strings do not intersect Prof. Dr. Paul Müller, University of Kaiserslautern 23
Page 1 and 2: Entropy Coding } different probabil
Page 3 and 4: The Braille Prof. Dr. Paul Müller,
Page 5 and 6: Morse Code Example: Letter statisti
Page 7 and 8: Huffman Coding } Idea: Use short bi
Page 9 and 10: Huffman Coding Symbol Count P2 205
Page 11 and 12: Huffman Coding Symbol Count Huffman
Page 13 and 14: Adaptive Huffman Coding } Problem -
Page 15 and 16: Adaptive Huffman Coding } Example n
Page 17 and 18: Adaptive Huffman Coding } A was inc
Page 19 and 20: Adaptive Huffman Coding } n+4-th Hu
Page 21: Huffman Coding Evaluation } Limitat
Page 25 and 26: Arithmetic Coding } Example I - Fou
Page 27 and 28: Arithmetic Coding } Example I (cont
Page 29 and 30: Arithmetic Coding Example II (cont.
Page 31 and 32: Arithmetic Coding } Remarks - if th
Page 33 and 34: Lempel - Ziv (LZ77) } Algorithm for
Page 35 and 36: Lempel - Ziv (LZ77) } Remarks - the
Page 37 and 38: Lempel - Ziv - Welch (LZ78) } LZ78:

05-compression-02-entropy coding.pptx - ICSY

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