著者

Satoshi Yoshida Takashi Uemura Takuya Kida Tatsuya Asai Seishi Okamoto

出版者

Information and Media Technologies 編集運営会議

雑誌

Information and Media Technologies (ISSN:18810896)

巻号頁・発行日

vol.7, no.1, pp.129-140, 2012 (Released:2012-03-15)

参考文献数

32

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We address the problem of improving variable-length-to-fixed-length codes (VF codes). A VF code that we deal here with is an encoding scheme that parses an input text into variable length substrings and then assigns a fixed length codeword to each parsed substring. VF codes have favourable properties for fast decoding and fast compressed pattern matching, but they are worse in compression ratio than the latest compression methods. The compression ratio of a VF code depends on the parse tree used as a dictionary. To gain a better compression ratio we present several improvement methods for constructing parse trees. All of them are heuristical solutions since it is intractable to construct the optimal parse tree. We compared our methods with the previous VF codes, and showed experimentally that their compression ratios reach to the level of state-of-the-art compression methods.