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A study on difference of codelengths between codes based on MDL principle and Bayes codes for given prior distributions

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE 2001年第4期84卷 30-40页

作者： Gotoh, M Matsushima, T Hirasawa, S Univ Tokyo Sch Engn Tokyo 1138656 Japan Waseda Univ Sch Sci & Engn Tokyo 1698555 Japan

The principle of the Minimum Description Length (MDL) proposed by J. Rissanen provides a type of structure for the model estimation based on probabilistic model selection allowing minimization of the codelength. On the other hand;the use of Bayes codes makes it possible to find a coding function from a mix of probabilistic models without specifying any concrete model. It has been pointed out that Codes based on the MDL principle (MDL codes) are closely related to Bayes theory because in the definition of the description length of the probabilistic model, an unknown drier distribution is assumed. In this paper, we apply asymptotic analysis to the codelength difference between the MDL codes and Bayes codes, including cases of different prior distributions. The results of the analysis clearly show that in the case of discrete model families, codes having a high prior distribution in true models (that is, the models for which an advantageous prior distribution is assumed) are favorable, but in the case of parametric model families;Bayes codes have shorter codelength than the MDL codes even in the cases of advantageous prior distribution assumed for the MDL codes. (C) 2000 Scripta Technica.

关键词： Bayes code MDL principle information source coding prior distribution

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Proposal of partially decodable Ziv-Lempel code

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE 1999年第12期82卷 79-87页

作者： Iwata, K Uyematsu, T Okamoto, E School of Information Science Japan Advanced Institute of Science and Technology Ishikawa Japan 923-12

With the digital representation of various data, such as speech, images, and messages, together with enhanced computer capabilities, it has become indispensable to apply data compression techniques to communication systems and recording systems. Among those, universal codes, including Ziv-Lempel codes, are widely used in computers, since the best compression can be realized asymptotically when the input string length is increased, even if the statistical properties of the input sequence are unknown. A problem arises, however, in connection with random data access or browsing, which are important functions in multimedia systems. In the Ziv-Lempel code, decoding must always be started from the top of the codeword sequence, even if only a part of the input coded sequence is to be decoded. This leads to an excessive load on computer resources. This paper proposes a code based on the Ziv-Lempel code in which partial decoding is possible. The proposed code is theoretically analyzed. The condition for the proposed code to be a universal code is presented. The encoding and decoding algorithms are implemented on a computer, and the result of the analysis is shown to be valid. It is shown that the proposed code has advantages over the Ziv-Lempel code from the viewpoint of applications, because the range of error propagation is restricted when an error is produced in decoding, and the decoding process can be accelerated by parallel processing. (C) 1999 Scripta Technica.

关键词： data compression information source coding universal code Ziv-Lempel code

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Generation of a compact code for extended binary memoryless sources with low entropy

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE 2000年第1期83卷 70-77页

作者： Hasegawa, M Kato, S Yamada, Y Utsunomiya Univ Fac Engn Utsunomiya Tochigi 321 Japan

A method is proposed for configuring the compact code for extended binary memoryless sources with probabilistic deviations in symbol appearance. In an n-th order extended information source for binary memoryless sources, messages with identical appearance probabilities are generated abundantly. If these messages are grouped for treatment, no rearrangement of the messages encompassing the groups is generated in degenerate operations by the Huffman algorithm for low-entropy information sources where the appearance probability of the superior symbols approaches arbitrarily close to 1. That is the situation is used in this paper. It is reported that the code length and sets of code words, average code length, and maximum code length of the compact code can be derived by a simple equation without forming a code tree. (C) 1999 Scripta Technica.

关键词： compact code Huffman code information source coding memoryless information source expanded information source

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Picture coding employing B-spline surfaces with multiple vertices

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS 1997年第2期80卷 55-65页

作者： Watanabe, T Toshiba Corp Kawasaki Japan

The effect of the B-spline is that the same result as processing the generated surface is obtained only by providing the image processing to the values at the vertices of the polygon. By having the value of the point on the B-spline surface correspond to the image data and the polygon vertices generating the surface as the object of the coding, the image processing carl directly be applied to the compressed data (polygon vertices). The author and others have investigated the approximation method for the behavior of the pixel value using the B-spline surface with such an advantage. It is shown here that the same or better compression efficiency can be realized compared to the conventional DCT. Also in this paper, the method is applied to the compression coding. In this method, the multiple polygon vertices are utilized to adjust the curvature of the surface without increasing the number of vertices of the polygon to be encoded. The main purpose of the proposed method is to multiplex the polygon vertices corresponding to the rapid change of the pixel value and to improve the approximation to the pixel values by the surface. As a result of simulation, a performance surpassing the method not considering the multiple vertices is obtained, both in terms of the signal-to-noise ratio (SNR) of the restored image and the subjective assessment. In other words, it is verified that it is useful in the compression coding to introduce the multiple vertices.

关键词： picture coding information source coding B-spline surface multiple polygon vertex surface fitting

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Picture coding employing B-spline surfaces with multiple vertices

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Electronics and Communications in Japan (Part I: Communications) 1998年第2期80卷

作者： Toshiaki Watanabe Research & Development Center Toshiba Corporation Kawasaki Japan 210

The effect of the B-spline is that the same result as processing the generated surface is obtained only by providing the image processing to the values at the vertices of the polygon. By having the value of the point on the B-spline surface correspond to the image data and the polygon vertices generating the surface as the object of the coding, the image processing can directly be applied to the compressed data (polygon vertices). The author and others have investigated the approximation method for the behavior of the pixel value using the B-spline surface with such an advantage. It is shown here that the same or better compression efficiency can be realized compared to the conventional DCT. Also in this paper, the method is applied to the compression coding. In this method, the multiple polygon vertices are utilized to adjust the curvature of the surface without increasing the number of vertices of the polygon to be encoded. The main purpose of the proposed method is to multiplex the polygon vertices corresponding to the rapid change of the pixel value and to improve the approximation to the pixel values by the surface. As a result of simulation, a performance surpassing the method not considering the multiple vertices is obtained, both in terms of the signal-to-noise ratio (SNR) of the restored image and the subjective assessment. In other words, it is verified that it is useful in the compression coding to introduce the multiple vertices. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (2):55–65, 1997

关键词： picture coding information source coding B-spline surface multiple polygon vertex surface fitting

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Generation of a compact code for extended binary memoryless sources with low entropy

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Electronics and Communications in Japan (Part III: Fundamental Electronic Science) 1999年第1期83卷

作者： Madoka Hasegawa Shigeo Kato Yoshifumi Yamada Faculty of Engineering Utsunomiya University Utsunomiya Japan 321

A method is proposed for configuring the compact code for extended binary memoryless sources with probabilistic deviations in symbol appearance. In an n -th order extended information source for binary memoryless sources, messages with identical appearance probabilities are generated abundantly. If these messages are grouped for treatment, no rearrangement of the messages encompassing the groups is generated in degenerate operations by the Huffman algorithm for low-entropy information sources where the appearance probability of the superior symbols approaches arbitrarily close to 1. That is the situation used in this paper. It is reported that the code length and sets of code words, average code length, and maximum code length of the compact code can be derived by a simple equation without forming a code tree. © 1999 Scripta Technica, Electron Comm Jpn Pt 3, 83(1): 70–77, 2000

关键词： compact code Huffman code information source coding memoryless information source expanded information source

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