Algoritmy pro rychlé kódování a dekódování dat

Jiří Walder

Doctoral thesis

Fast data Encoding and Deconding Algorithms

Abstract:

Pˇri zpracov´an´ı dat jsou ˇsiroce vyuˇz´ıvany kompresn´ı metody. Tyto metody nejˇcastˇeji vyuˇz´ıvaj´ı k´ody s promˇennou d´elkou, kdy kratˇs´ı k´odov´a slova jsou pˇriˇrazov´ana sym- bol°um nebo skupin´am symbol°u s vyˇsˇs´ı frekvenc´ı v´yskytu v k´odovan´ych datech. K z´astupc°um tˇechto k´od°u patˇr´ı k´ody Fibonacci, Elias-delta a Elias-Fibonacci, kter´e jsou vyuˇzity i v t´eto pr´aci. Pro nˇekter´e aplikace zpracov´an´ı dat je ˇcasov´a n´aroˇcnost a efektivita k´odov´an´ı a dek´odov´an´ı velmi d°uleˇzit´a, a proto byly ned´avno publikov´any pr´ace zab´yvaj´ıc´ı se metodami rychl´eho dek´odov´an´ı. Metody pro rychl´e k´odov´an´ı vyuˇz´ıvaj´ıc´ı v´yˇse zm´ınˇen´ych k´od°u prozat´ım publikov´any nebyly. V t´eto pr´aci jsou pˇredstaveny nov´e metody rychl´eho k´odov´an´ı a dek´odov´an´ı pro k´ody Fibonacci, Elias- delta a Elias-Fibonacci. Rychl´e kodovac´ı algoritmy jsou aˇz 12.5× rychlejˇs´ı neˇz bˇeˇznˇe pouˇz´ıvan´e k´odovac´ı algoritmy a rychl´e dek´odovac´ı algoritmy jsou aˇz 8.9× rychlejˇs´ı neˇz bˇeˇznˇe pouˇz´ıvan´e dek´odovac´ı algoritmy.

Abstract:

Data compression has been widely applied in many data processing areas. Com- pression methods utilize variable-length codes with shorter codewords assigned to symbols or groups of symbols that appear in the data frequently. Fibonacci, Elias- delta, and Elias-Fibonacci codes are representatives of these codes, and are often utilized for the compression of numbers. The time consumption of encoding as well as decoding algorithms is important for some applications in the data processing area. In this case, the efficiency of these algorithms is extremely important. Some works related to fast decoding of variable-length codes have been published in re- cent years. Fast encoding algorithms for these codes have not yet been studied. In this work, we introduce fast encoding and decoding algorithms. Our fast en- coding algorithms are up to 12.5× faster than conventional bit-oriented algorithms and our decoding algorithms are up-to 8.9× faster than the conventional decoding algorithms.

Keywords

komprese, k´ody s promˇennou d´elkou, rychl´e k´odovac´ı algoritmy, rychl´e dek´odovac´ı algoritmy, Elias-delta, Fibonacci, Elias-Fibonacci

Keywords

compression, variable-length code, fast encoding algorithm, Elias-delta code, Fibonacci codes of order 2 and 3, Elias-Fibonacci code

Language used: Czech

Date on which the thesis was submitted / produced: 27. 5. 2013

Thesis defence

• Date of defence: 19. 8. 2013
• Supervisor: Michal Krátký
• Reader: Jiří Dvorský

VŠB - Technical University of Ostrava

Fakulta elektrotechniky a informatiky

Doctoral programme / field:
Informatika, komunikační technologie a aplikovaná matematika / Informatika