Updated on 2022/05/25


KATO, Yoichi
Faculty of Science and Engineering, Global Center for Science and Engineering
Job title
Professor(without tenure)

Research Institute

  • 2020

    理工学術院総合研究所   兼任研究員


Research Areas

  • Human interface and interaction   Image Processing, Digital Signal Processing, Design Thinking


  • Mission of the ICT design center

    Kato, Y., Asano, Y., Ohno, T.

    NTT Technical Review   9 ( 9 )  2011  [Refereed]

  • A study on hybrid motion video coding schemes– block size, comparison of dct and vq schemes, loop filter

    Yoichi Kato, Sakae Okubo, Yutaka Suzuki

    Electronics and Communications in Japan (Part I: Communications)   73 ( 12 ) 45 - 54  1990  [Refereed]

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    To design a highly efficient video codec, comparisons of available techniques from various viewpoints are necessary so that the coding scheme and parameters are chosen appropriately. In recently presented papers and equipment, many systems use motion‐compensated interframe prediction and DCT or VQ schemes for the prediction error coding. A loop filter often is adopted to improve coding efficiency. This paper compares DCT and VQ schemes in an interframe coding scheme, on an optimal blocksize for interfreme prediction error signal coding and on the effect of loop filtering from the viewpoints of coding efficiency and reproduced image quality. Simulations using actual image sequences show that the optimal block size is 4 × 4 or 8 × 8, that the loop filter improves significantly the coding efficiency and reproduced image quality, and that DCT and VQ schemes give nearly the same efficiency with an appropriate loop filter. Copyright © 1990 Wiley Periodicals, Inc., A Wiley Company


  • International standardization of video codecs for ISDN videoconferencing and videophone services

    Okubo, Sakae, Nishimura, Shinji, Kato, Yoichi

    NTT Review   2 ( 3 )  1990  [Refereed]

  • A coding control algorithm for motion picture coding accomplishing optimal assignment of coding distortion to time and space domains

    Yoichi Kato, Naoki Mukawa, Sakae Okubo

    Electronics and Communications in Japan (Part I: Communications)   72 ( 9 ) 63 - 73  1989  [Refereed]

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    In high‐efficient motion picture coding such as systems to compress moving image information below several 100 kbit/s, some visible spatial and temporal distortions are unavoidable. The spatial distortion is perceived by humans as a spatial degradation or noise on the image. On the other hand, the temporal distortion, which is caused by frame dropping, occurs as unnaturalness of motions in the processed image sequence. Here, spatial and temporal distortions are in a trade‐off relationship. Finding the visually best point from this trade‐off is a key feature of good codecs. This paper describes a newly developed coding control algorithm aimed at keeping spatial and temporal distortions in a good balance. In the algorithm, the trade‐off relationship is calculated first from generated information amount vs. the SNR characteristics of the current input frame. Next, an optimal distribution is determined from the viewpoint of human perception. Finally, a coding parameter set is chosen for realizing the distribution and reproduces visually good images. This paper shows the principal of the coding control algorithm and describes an application of the algorithm to an MC‐DCT coding system and simulation results. Copyright © 1989 Wiley Periodicals, Inc., A Wiley Company


  • An adaptive orthogonal transform coding algorithm for images utilizing classification technique

    Yoichi Kato, Naoki Mukawa, Sakae Okubo

    Electronics and Communications in Japan (Part I: Communications)   72 ( 5 ) 1 - 10  1989  [Refereed]

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    An adaptive orthogonal transform coding algorithm utilizing the classification technique is presented. Coding efficiency for natural images can be improved by adjusting coding parameters in accordance with the local property of images. “Classification” is used to categorize small areas of an image into classes based on their characteristics. High coding efficiency results from changing coding parameters adaptively according to the classification index. Classification methods using ac energy, binary pattern and vector quantization index are compared, and the advantage of the classification method with the vector quantization technique is shown. Also, an orthogonal transform coding algorithm with an adaptive variable length coding method is proposed, and its structure and characteristics are described. A coding parameter normalization method to avoid mismatches between input images and coding parameters is also described. Coding experiments show excellent performance of this algorithm, for example, the number of bits for obtaining 40‐dB SNR of monochrome “GIRL” is 0.65 bits/pel, which is 20 percent smaller than conventional methods. Copyright © 1989 Wiley Periodicals, Inc., A Wiley Company



    Mukawa, Naoki, Hashimoto, Hideo, Kato, Yoichi, Okubo, Sakae

    Denki Tsushin Kenkyujo kenkyu jitsuyoka hokoku   37 ( 3 )  1988  [Refereed]


    Mukawa, Naoki, Kato, Yoichi, Okubo, Sakae

    Reports of the Electrical Communication Laboratory   36 ( 2 )  1988  [Refereed]

  • A Motion Picture Coding Algorithm Using Adaptive DCT Encoding Based on Coefficient Power Distribution Classification

    Yoichi Kato, Naoki Mukawa, Sakae Okubo

    IEEE Journal on Selected Areas in Communications   5 ( 7 ) 1090 - 1099  1987  [Refereed]

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    A motion picture coding algorithm using motion-compensated interframe prediction and the adaptive discrete cosine transform (DCT) encoding technique is proposed. High coding efficiency is obtained by the adaptive DCT encoding technique in which encoding parameters are fitted to widely varying characteristics of the interframe differential signal. Segmented DCT subblocks of interframe prediction error are classified into categories based on their coefficient power distribution characteristics. The adaptation gain results from using a suitable variable word length code set designated by the above classification for encoding each quantization index of DCT coefficients. In addition, a new coding parameter control method is introduced based on the information rate estimation of the current frame. This classification promotes high stability because good estimation accuracy of bits consumption for each DCT subblock is obtained by utilizing the category indexes. Simulation results show that the proposed algorithm has enough coding efficiency to transmit videoconferencing motion pictures through a 384 kbit/s channel. Copyright © 1987 by The Institute of Electrical and Electronics Engineers, Inc.


  • Restoration of blurred images using two‐dimensional digital filters with noise suppression

    Takashi Yahagi, Yoichi Kato

    Systems and Computers in Japan   16 ( 5 ) 1 - 9  1985  [Refereed]

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    New two‐dimensional nonrecursive digital filters are proposed for noisy blurred images. A two‐dimensional nonrecursive filter is developed to minimize the mean‐squared error of the restored image. Here, the point spread function of the blurring system and statistics of the original image and noise are assumed to be given. A simplified version of the above filter is also developed and tested for restoring images blurred by a linear blurring system. As a result of their nonrecursive nature the proposed filters are stable and are determined by solving linear systems of equations. The blur by the point spread function and that due to degradation by noise are considered in the design of the filters. Images can be restored while the accompanying noise is suppressed. The filters herein are shown to be more effective if combined with noise‐removal filters. Illustrative examples are included to demonstrate the excellent quality of images restored by the proposed filters. Copyright © 1985 Wiley Periodicals, Inc., A Wiley Company



    Yahagi, Takashi, Kato, Yoichi

    Systems, computers, controls   15 ( 2 )  1984  [Refereed]


    Yahagi, Takashi, Kato, Yoichi, Shinozaki, Michio

    Systems, computers, controls   15 ( 1 )  1984  [Refereed]

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Specific Research

  • AIとIOTが併用される応用開発のプロトタイピング手法に関する研究


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  • ICT/AI/IOT分野での効率的効果的なプロトタイピング手法に関する研究


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