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Research on Dependable Techniques for Compressed Text Data

可靠的文本数据压缩技术研究

基本信息

批准号：
13450152
负责人：
FUJIWARA Eiji
金额：
$ 8.26万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

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.

这项研究提出了可靠的技术，无损压缩数据，保护解压数据发生错误的压缩数据。下面介绍所提出的技术。（1）对于霍夫曼编码：提出了能够双向解码的霍夫曼编码，其不仅可以从压缩数据的顶部而且可以从尾部解压缩。通过比较前向和后向解压缩得到的解压缩结果，获得错误位置的候选者。（2）对于算术编码：压缩数据被分成固定长度的块。解压缩中的参数被视为解压缩器的内部状态，并包含在每个块的开头。这些内部状态用于错误检测和从错误状态恢复。提出了利用附加校验信息对错误块进行恢复的方法。（3）对于Ziv-Lempel编码：已经提出了基于不等错误保护或UEP的方法。压缩后的数据中有一部分对错误的敏感度比其他部分高。嵌套错误控制，它使用额外的检查信息的错误敏感部分已被提出。还提出了分离差错控制编码，其中差错敏感部分被单独编码。（4）对于LZ 77编码和霍夫曼编码的二级压缩，提出了分离压缩方法。LZSS编码是LZ 77编码的一种变体，它将压缩数据分为符号集和整数集，分别采用霍夫曼编码进行压缩。通过比特重排，每个码字的顶部的位置是固定的。（5）对于基于组模式匹配的压缩：中间码字的重要部分由差错控制码编码，而其它部分由具有差错恢复能力的熵编码压缩。