2022/07/02 更新

写真a

カトウ ヨウイチ
加藤 洋一
所属
理工学術院 国際理工学センター(理工学術院)
職名
教授(任期付)

学内研究所等

  • 2020年
    -
    2022年

    理工学術院総合研究所   兼任研究員

 

研究分野

  • ヒューマンインタフェース、インタラクション   画像処理、ディジタル信号処理、デザイン思考

論文

  • Mission of the ICT design center

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

    NTT Technical Review   9 ( 9 )  2011年  [査読有り]

  • 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年  [査読有り]

     概要を見る

    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

    DOI

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

    Okubo, Sakae, Nishimura, Shinji, Kato, Yoichi

    NTT Review   2 ( 3 )  1990年  [査読有り]

  • 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年  [査読有り]

     概要を見る

    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

    DOI

  • 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年  [査読有り]

     概要を見る

    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

    DOI

  • 384KBIT/S VIDEO CODEC.

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

    Denki Tsushin Kenkyujo kenkyu jitsuyoka hokoku   37 ( 3 )  1988年  [査読有り]

  • 384-KBIT/S VIDEO CODEC.

    Mukawa, Naoki, Kato, Yoichi, Okubo, Sakae

    Reports of the Electrical Communication Laboratory   36 ( 2 )  1988年  [査読有り]

  • 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年  [査読有り]

     概要を見る

    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.

    DOI

  • 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年  [査読有り]

     概要を見る

    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

    DOI

  • RESTORATION OF BLURRED IMAGES USING TWO-DIMENSIONAL DIGITAL FILTERS AND NOISE REMOVAL FILTERS.

    Yahagi, Takashi, Kato, Yoichi

    Systems, computers, controls   15 ( 2 )  1984年  [査読有り]

  • RESTORATION OF BLURRED IMAGES BY AN ITERATIVE ESTIMATION ALGORITHM BASED ON A TWO-DIMENSIONAL WIENER FILTER.

    Yahagi, Takashi, Kato, Yoichi, Shinozaki, Michio

    Systems, computers, controls   15 ( 1 )  1984年  [査読有り]

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特定課題研究

  • 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

    2021年  

     概要を見る

    本テーマは2020年4月の新規嘱任後に開始したものである。今期は渋谷100Banchプログラムから発生したスタートアップの調査と、画像解析を伴うIoT-機械学習系システムの構築、技術検証を実施した。その結果、安定事業を持つ企業に比べ、スタートアップ企業では内部プロトタイピング期間が短く、完成度が低くても実利用を開始する傾向があることを発見した。隣接道路上の車の走行と家屋振動との関係を調査するという目的を設定し、画像認識を含む様々な技術要素を検証した。

  • 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

    2020年  

     概要を見る

    本テーマは4月の新規嘱任後に開始したものである。今期は外部調査一件と、IoT-機械学習系システムの基本部分の構築を実施した。外部調査の結果、プロトタイピング活動は、計画期間を大幅に超過する傾向にあること、達成できた性能や機能が計画時のものから変化していること、などが判明した。プロトタイピング進行に伴い関係者の理解が進み、そのため、システムの有効性に真に必要な性能・機能の要求内容が変化したためと想定される。来期は、上記知見を基に半構造的なインタビュー計画を策定し、他の事例を調査するとともに、プロトタイピングの見通しを改善する手法の考案を試みる。

 

現在担当している科目

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