Compressing Data Konstantin Tretyakov (
[email protected]) MTAT.03.238 Advanced Algorithmics April 26, 2012 Algorithmics 26.04.2012 Claude Elwood Shannon (1916-2001) Algorithmics 26.04.2012 C. E. Shannon. A mathematical theory of communication. 1948 Algorithmics 26.04.2012 C. E. Shannon. The mathematical theory of communication. 1949 Algorithmics 26.04.2012 Shannon-Fano coding Nyquist-Shannon sampling theorem Shannon-Hartley theorem Shannon’s noisy channel coding theorem Shannon’s source coding theorem Rate-distortion theory Ethernet, Wifi, GSM, CDMA, EDGE, CD, DVD, BD, ZIP, JPEG, MPEG, … Algorithmics 26.04.2012 MTMS.02.040 Informatsiooniteooria (3-5 EAP) Jüri Lember http://ocw.mit.edu/ 6.441 Information Theory https://www.coursera.org/courses/ Algorithmics 26.04.2012 Basic terms: Information, Code “Information” “Coding”, “Code” Can you code the same information differently? Why would you? What properties can you require from a coding scheme? Are they contradictory? Show 5 ways of coding the concept “number 42” What is the shortest way of coding this concept? How many bits are needed? Aha! Now define the term “code” once again. Algorithmics 26.04.2012 Basic terms: Coding Suppose we have a set of three concepts. Denote them as A, B and C. Propose a code for this set. Consider the following code: A → 0, B → 1, C → 01 What do you think about it? Define “variable length code”. Define “uniquely decodable code”. Algorithmics 26.04.2012 Basic terms: Prefix-free If we want to code series of messages, what would be a great property for a code to have? Define “prefix-free code”.