近年, 放送をケーブルテレビ経由で視聴している世帯が増えている.デジタル放送時代が本格化するなかで, CS, BS, 地上放送の再送信やインタネット接続を通して, ケーブルテレビはますます身近で重要な情報インフラとなってきた.本稿では, アナログからディジタルへと進化し, さらなる高度化をめざすケーブルテレビの技術動向や次世代にむけた情報通信技術の研究開発の課題について解説する.

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MPEG-21の標準化が活発化してきた.またブロードバンドの急速な普及により日本でもマルチメディア利用の将来像への関心が高まっている.MPEG-21は国際標準である以上, 近い将来まで有効な標準となることを目指すべきだと考えられるが, マルチメディア利用の将来像は必ずしも鮮明ではない.以下では近い将来のユビキタスマルチメディアの展望を描きながらMPEG-21への課題と期待を述べる.

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We developed RF-wave-receiving equipment with an optical modulator for digital terrestrial broadcasting. This new equipment uses optical fiber cables as a transmission line, it does not require electrical power lines at the receiving end and enables multi-digital television wave transmission. This equipment can be effectively used to construct sfn (single frequency networks), because the transmission and receiving ends can be easily separated. This equipment is based on polarization-independent optical modulation at the receiving station and the use of a low-noise amplifier powered by laser optical power from the transmitting station. This makes it possible to use a laser diode as an optical source instead of two YAG lasers, which greatly reduces the cost of equipment.

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Recently, media convergence and interoperability over multiple networks are becoming a determining factor for the success of new digital broadcasting and telecommunication services. In this paper, we present an original architecture framework providing a mean for seamless transport of RTP based streaming over both Internet and ISDB (ARIB) networks. This goal is achieved by using the independence of the RTP protocol from the transport layer, and by remarking that MPEG-2 Systems based ISDB provides a high-quality packet delivery scheme with the DSM-CC protocol. We propose to carry RTP/RTCP packets in DSM-CC messages, whereas an RTSP messages subset is being mapped onto ARIB DSM-CC event messages. The complete architecture is evaluated using a PC based simulator including a BML browser and a transport stream demultiplexer card.

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Several cancelers have been developed for coping with multipath arid loop coupling at relay stations in ISDBT digital terrestrial broadcasting systems using OFDM (Orthogonal Frequency Division Multiplexing) signals, This paper describes simplified iteratively adaptive algorithms based on a least means square method for cancellation filters, The use of an adaptive filter operating in IF bands greatly simplifies the required hardware, minimizes its size, and does not degrade the system performace. The results of a computer simulation showed that the algorithms can be used in OFDM digital broadcasting systems.

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This paper describes an array-antenna-assisted Doppler spread compensator for terrestrial digital television broadcasting based on orthogonal frequency division multiplexing (OFDM). A linear array antenna is installed on top of the vehicle. The compensator estimates the received signal at a certain point on the linear array antenna by using space domain interpolation. Because the relative position of the estimated receiving point with respect to the ground does not change during the effective symbol duration of an OFDM signal, the time variation due to the movement of the vehicle can be compensated for. Computer simulation shows that the compensator can compensate for the bit error rate performance degradation due to time-variation of the channel when the velocity of the vehicle is up to 180km/h and a two-element array antenna is used at the carrier frequency of 600 MHz. The bit error rate performance can be further improved by using a four-element array anetenna.

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Diversity reception is an effective method for improving the bit-error-rate characteristics of OFDM signal in frequency-selective fading environments. However, the hardware complexity of the receiver increases in proportion to the number of antennas used. In this paper, we describe an OFDM diversity receiver whose hardware is much simpler than that of conventional diversity receivers. This receiver improves the bit error rate characteristics of OFDM signals, compared to those obtainded in single-antenna reception. In the proposed receiver, signals from each antenna are combined at the intermediate stage of FFT and the total hardware required for FFT operations is the same as in a single-antenna receiver. We examined, both theoreticaly and by computer simulations, and found that the bit-error-rate characteristics of OFDM signals obtained by using the proposed reciever were better than that of the single antenna receiver.

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This paper describes a high compression MPEG-2 encoding scheme for distributing HDTV programs at a bit-rate of up to 15 Mbps that can be used for digital terrestrial broadcasting in Japan. Obtaining an adequate picture quality in broadcasting at such a low bit-rate by using conventional MPEG-2 coding scheme is impossible.We thus developed optimum coding for the picture and macroblock layer, i.e. scene adaptive picture type assignment and optimum selection of macroblock coding modes. In the scene adaptive picture type assignment, the characteristics of input HDTV signals are analyzed prior to actual encoding. The optimum selection of macroblock coding modes is used to encode each macroblock to minimize the source information while preserving the target picture quality. This new scheme can be used with MPEG-2 standards and it is compatible with any MPEG-2 decoder. Experiments using various motion pictures showed that the proposed optimum MPEG-2 encoding scheme significantly improves encoding and can thus be used for digital terrestrial broadcasting in Japan.

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In this paper, we discribe a. method for generating an all-focused image from a. large number of microscopic images of insects. First, we describe our previously proposed select-and-merge method for all-focused image acquisition. We can obtain good results by using this method for two differently focused images. However, this method can't. give a good result when a large number of images are used. We thus developed a method that. compares each image with those preceding and following it based on the estimation of focused regions. We compare the results of image reconstruction by using the new method with those obtained by using our previously method. We then generate a 3D image bye using the intensity of an all-focused image and the depth of in-focus regions, both obtained by our proposed method.

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To broadcast sports games, we need several video cameras and a multi-camera switching system. This paper describes a new automatic shooting and switching system that enables broadcasting an American-football game by controlling cameras and a switcher. This system directs active cameras at the position of the players and switches between the cameras according to the results of image analysis based on the characteristics of the game. In image analysis, the position of the players is detected by background subtraction and calculation of gravity points with labeling and histogram analysis. For this analysis, images from a fixed wide-angle camera are used. In shooting a game by using several active cameras, each active camera records a certain type of players' motion. The switching system determines which active cameras shoot the game according to the analysis of the players' motion. We have designed prototype system. Experimental results show that this system can shoot the players' motion automatically.

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We developed a method for initial region segmentation based on the mixture Gaussian model. First, the distribution parameters corresponding to objects in a scene are estimated from intensity histograms by using the EM algorithm. Next, the range parameters for region segmentation are determined by using the estimated distribution parameters. Finally, that images are segmented by using these range parameters. Experimental results obtained by using real scenes from a PC program showed that the method was effective for the initial region segmentation task. This method can be used in a variety of object recognition systems applied for various industrial applications, including surveillance, in fixed ground sub-systems of intelligent transport systems (ITS), and in welfare support systems.

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A loop canceller is described for coping with loop coupling at relay stations for OFDM (orthogonal frequency division multiplexing) SFNs (single frequency networks) in terrestrial digital broadcasting systems. An iteratively adaptive algorithm based on the least means square method is used for the loop cancellation filter. Use of this adaptive filter reduces hardware complexity and minimizes hardware size. Computer simulation showed that the proposed canceller is effective for loop cancellation in actual OFDM digital broadcasting systems.

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1シンボル当たり10ビットを伝送する1024QAM変調方式について, 変復調器における固定劣化を評価した.直交検波する搬送波の位相やシンボルの識別タイミングが最適でない場合の伝送特性をシミュレーションにより求め, 実装のための指針を得た.

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本稿では, 手話の形状と軌道が同じで, 動作時間の差により複数の意味を持つ同動作異義語の時間弁別閾値について検討を行い, 手話を弁別するには手指の形状や位置, 表情などの他に動作時間の情報も重要であること, また, 同動作異義語に対して, 手話単語の理解がどの時間範囲において確立するのかを示す.

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In recent years, three-dimensional objects have been utilized as internet media contents because computer hardware has high capability and its software cost decreases. In general, the three-dimensional objects are called polygon models that consist of a group of triangle meshes and they can be drawn at high speed by high quality CPU and 3D graphics accelerator mesh simplification have been proposed of late years. In the former methods, polygon models are simplified by using only edge information. On the other hand, the proposed method simplifies the model using triangle edge and face information. Experimental results show that the method is effective for preserving the feature of the polygon model.

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An ultra-high-resolution method using a multiple-step swing and wobbling operation is described for improving the resolution of solid-state image sensors. The method is based on the periodical shifting of the device to form multiple pixels. By analyzing the operation of this method, the optimum operation conditions were derived for achieving high resolution with low aliasing and low field flicker phenomena. Also described is a multiple-step wobbling operation with triangular waves that achieves high resolution with even lower aliasing and a wider operation range. Suitable display conditions of the multiple-step swing imaging signals were derived for achieving high resolution display images.

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通信・放送機構のプロジェクトとして進めてきた, 「字幕番組制作システム」研究の一環として, 多様な字幕表示形式を選択可能な字幕放送受信システムを開発した.これは先に聴覚障害者など多数の評価者の協力を得て行った字幕表示形式に関する主観評価実験結果と, この実験のために研究した字幕生成技術をベースに開発したものである.本システムは, 字幕表示形式に関する字幕放送利用者の多様なニーズに対し, 字幕行数, 文字サイズ, 字幕転換法などの組合せで設定した十数種の形式から, 利用者が好みに応じて任意に選択し, 利用することを可能としたPC版字幕放送受信システムであり, 本稿ではこれらの機能・構成などを中心に述べる.

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