2003 Fiscal Year Final Research Report Summary
Research on Dependable Techniques for Compressed Text Data
| Project/Area Number |
13450152
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
情報通信工学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
FUJIWARA Eiji Tokyo institute of Technology, Graduate School of Information Science and Engineering, Professor, 大学院・情報理工学研究科, 教授 (20211526)
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| Co-Investigator(Kenkyū-buntansha) |
KITAKAMI Masato Chiba University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20282832)
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| Project Period (FY) |
2001 – 2003
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| Keywords | text compression / lossless compression / error recovery / Huffman coding / arithmetic coding / Ziv-Lempel coding / UEP (Unequal Error Protection) / group pattern matching |
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| Research Abstract |
This research has proposed dependable techniques for lossless compressed data which protect the decompressed data from errors occurring in the compressed data. The following presents the proposed techniques.
(1)For Huffman coding:
Huffman coding capable of bidirectional decoding, which can be decompressed not only from the top but also from the tail of the compressed data, is proposed. By comparing decompression results obtained by forward and backward decompression, the candidates of error locations are obtained.
(2)For arithmetic coding:
Compressed data are divided into fixed-length blocks. Parameters in decompression are regarded as internal states of the decompressor and are included into the beginning of each block. These internal states are used in both error detection and recovery from the erroneous state. Recovery method for the erroneous block by additional check information has also been proposed.
(3)For Ziv-Lempel coding:
The method based on Unequal Error Protection, or UEP has been proposed. Compressed data include a part which is more sensitive to the errors than others. Nested error control which uses additional check information for the error sensitive part has been proposed. The separated error control coding where error sensitive part is encoded-separately has also been proposed.
(4)For 2-level compression by LZ77 coding and Huffman coding:
Separated compression method has been proposed. The compressed data of LZSS coding, a variation of LZ77 coding, are divided into two sets, sets of symbols and integers, and are compressed by Huffman coding separately. By bit-rearrangement, the position of the top of each codeword is fixed.
(5)For compression based on group pattern matching:
Important part of the intermediate code word is encoded by error control codes and other part is compressed by entropy coding with error recovery capability.
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