| 摘要 |
PURPOSE:To improve the compressibility without spoiling the easiness of slide dictionary type algorithm by registering an initial value character string consisting of a special kind of data which is high in appearance frequency in a dictionary. CONSTITUTION:An initial value generation part 14 encodes representative sample data according to the dynamic dictionary type algorithm. Then a counter counts the frequency of use of a reference number, indicating a character string registered in a dictionary generated by this encoding, at the time of the encoding as an appearance frequency, and registered character strings in the dictionary 24 which have appearance frequencies larger than a specific threshold value are extracted and arrayed when the encoding of the sample data ends to generate an initialization character string. The initialization value character string generated by the initialization value generation part 14 is used for data compression using a slide dictionary at a data compression and restoration part 30. Thus, the character strings which are high in use frequency are previously registered in the dictionary, so the probability that long input data match a character string to the longest length becomes high to improve the efficiency of the encoding. |
