A systematic design method for a variable length code (VLC) which makes using a unique word possible is proposed. A unique word is an effective and practical technique for synchronizatiion recovery from continuous erroneous states in binary signal transmission, especially with VLC'_3 that can damage reconstructed signals severely. Use of it, however, restricts the selection of VLC codewords so that no combination of them in a bit stream emulates the unique word in order to guarantee its uniqueness. Due to the need of special care about the bit pattern of the VLC'_3 for a unique word, such VLC'_3 have been constructed only heuristically. This paper proposes a systematic technique to construct an emulation-less VLC with little efficiency loss, and analyzes the efficiency quantitatively based on the occurrence probabilities and unique word length. This paper also suggests application of the new method to multiple VLC'_3.

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In this paper, we propose a lossless motion video coding method using motion compensation with bit-plane expansion under the constrained bitrate. Two approaches, closed bit-plane approach and merged bit-plane approach, are considered and characteristics of their compression efficiency is estimated. Simulation results show that the proposed method is suitable for lossless video coding with bitrate control.

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Structure runlength coding, briefly SRC, is an efficient coding for simple synthetic images. In the coding, only one of four symbols is substituted for each pixel. At the same time, additional 24 bits stand for the color of a pixel which has no relation to its neighbors. With the increase of colors, however, those pixels with no relation to their neighbors increase fast. It decreases dramatically the efficiency of SRC. In this paper, we suggest to separate the symbol data and color data. The symbol data can be compressed by dictionary-based coding, and color data are processed by predictive DPCM (differential pulse code modulation). The predictive coefficients are adapted by the result of SRC. The proposed method can reach the higher efficiency than the SRC, especially for images with many colors, at the cost of additional buffers needed to store all compressed symbol data and color data in a decoder.

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Some kinds of digital signals such as medical images are required to be compressed in a lossless or nearly lossless manner. This paper describes a lossless and nearly lossless conversion with orthogonal transforms which are usually used to perform data compression in a lossy manner. It is assumed that forward and inverse transforms are carried out without producing any errors. The coefficients obtained by forward transform are truncated in floating-point format. Their errors due to finite precision are analyzed, and precision of coefficients necessary to limit errors of reconstructed signals in a given range is derived. The case of the one-dimensional discrete cosine transform in studied.

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This paper describes a new simulator for MPEG encoder with interactive manipulating tools. In this simulator, the sender estimates whether each segment of images is important or not, and select the methods of preprocessing and the quality classes for each segment interactively. This simulator can produce higher quality decoded images than those obtained by automatic encoding.

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We have studied necessary functions for digital video transmission systems using MPEG2 and ATM technology. The functions are interactive data communication for mode negotiation between terminals, multiplexing function on some layers for media and program multiplex transmission, and storage/delivery function of MPEG2 bitstream, for example. We have investigated some methods and proposed a suitable system model for realizing these functions.

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