Internet users have become well acquainted with the World Wide Web (WWW) system, and WWW has become the most significant service on the Internet. In the near future, the importance of large scale hypermedia database systems based on WWW technologies is expected to continue to increace. The present study focuses on the issue of managing hyperlink integrity constraints on WWW like hypermedia database systems. After formally defining path existence constraint definitions(PEDs) using intuitive examples, we apply the notion of PEDs to represent hyperlink integrity constraints. Intuitively, a PED can be used to represent the following integrity constraint. If a reference path exists in a given database, then another corresponding reference path must also exist. An outline of a prototype hypermedia database system, AYATORI, which is based on the proposed model and under development, is also mentioned.

This paper presents results of subjective assessment of the media synchronization quality in the virtual-time rendering (VTR) media synchronization algorithm. For the assessment, stored voice and video streams were transmitted as two separate transport streams from a source to a destination on various traffic conditions in an experimental system. At the destination, they were output after synchronization control. We subjectively assessed the quality of media synchronization in a systematic way. This paper examines the effects of the difference between methods of recovery from asynchrony on the media synchronization quality. The paper also clarifies the relationships between the subjective and objective performance measures. Furthermore, it examines the effect of the difference in scene between media streams and that of the modification of the target output time on the media synchronization quality.

This paper surveys recent research activities on three major areas of digital media information base, namely, video database systems as a typical example of temporal application, database systems for mixed reality as an instance of spatial application, and kansei management for digital media retrieval as a case of humanistic feelings application. Current research results by the project Advanced Database Systems for Integration of Media and User Environments are reported.

For advanced data-oriented applications in distributed environments, effective information is frequently obtained by integrating or merging various autonomous information sources. There are many problems: how to search information sources, how to resolve their heterogeneity, how to merge or integrate target sources, how to represent information sources with a common protocol, and how to process queries. We have proposed a new language, QUIK, as an extension of a deductive object-oriented database (DOOD) language, QUIXOTE, and extend typical mediator systems. In this paper, we discuss various features of QUIK: programming capabilities as integrating an exchange model and mediator specifications, merging subsumption relations for maintaining consistency, searching alternative information sources by hypothesis generation, and identifying objects.

The Web is a collection of multimedia documents in the form of HTML pages connected through hyperlinks. Unlike most search engines, which focus on information retrieval based on keywords, WebDB aims at supporting database-like comprehensive query functionalities as well navigation, and document generation functionalities with customizability. To support hypermedia database functionalities, we augment the traditional concepts of tables in relational databases and classes in object-oriented databases with notions of document formats and navigation. We design WQL (Web Query Language) as an HTML document manipulation language. WQL language statements contain two parts: SELECT. . . FROM. . . WHERE clauses for specifying retrieval of data contents from hypermedia databases and CREATE. . . AS. . . clauses for specifying the output HTML format and navigation of the query results. This paper presents the architecture of WebDB and its functionalities. The extension to SQL for hypermedia document manipulation, query, and navigation and implementation on NEC PERCIO OODBMS are described in detail.

Support of collaborative work and management of spatio-temporal data has become one of the most interesting and important database applications, which is due to the tremendous progress of database and its surrounding technologies in the last decade. In this paper, we investigate the new generation database technologies that are needed to support such advanced applications. Because of the recent progress of virtual reality technology, virtual work spaces are now available. We examine a typical CSCW (Computer Supported Cooperative Work) fsystem to identify database problems that arise from it. We introduce typical approaches to database improvement based on the high-level view and the virtual reality technique. Also, in this paper, the following are introduced and discussed: the design and implementation of three- and four-dimensional spatio-temporal database systems, VRML (Virtual Reality Modeling Language) database systems, fast access methods to spatio-temporal data, and the interval-based approach to temporal multimedia databases.

IEEE 802. 11 is a standard for wireless LANs. The basic access method in its MAC layer protocol is the distributed coordination function (DCF) for the ad hoc networks. It is based on the mechanism of carrier sense multiple access with collision avoidance (CSMA/CA). DCF is used to support asynchronous data transmission. However, frames in DCF do not have priorities, making it unsuitable for real-time applications. With a little bad luck, a station might have to wait arbitrarily long to send a frame. In this paper, we propose a method to modify the CSMA/CA protocol such that station priorities can be supported. The method is simple, efficient and easy to implement in comparison to point coordination function (PCF), another access method in IEEE 802. 11 based on access points (base stations). Simulations are conducted to analyze the proposed scheme. The results show that DCF is able to carry the prioritized traffic with the proposed scheme.

Voice activity detection (VAD) is to determine whether a short time speech frame is voice or silence. VAD is useful in reducing the mean speech coding rate by suppressing transmission during silence periods, and is effective in transmitting speech and other data simultaneously. This letter describes a VAD system that uses a neural network. The neural network gets several parameters by analyzing slices of the speech wave form, and outputs only one scalar value related to voice activity. This output is compared to a threshold to determine whether the slice is voice or silence. The mean code transfer rate can be reduced to less than 50% by using the proposed VAD system.

This paper studies the application of a media synchronization mechanism to the interleaved transmission of video and audio specified by the H.223 Annex in PHS. The media synchronization problem due to network delay jitters in the interleaved transmission has not been discussed in either the Annex or any related standards. The slide control scheme, which has been proposed by the authors, is applied to live media. We also propose a QOS control scheme to control both quality of the media synchronization and that of the transmission delay. Through simulation we confirm the effectiveness of the slide control scheme and the QOS control scheme in the interleaved transmission.

When wireless multi-media information such as voice, video, data and so on are transmitted, the difference required quality of Service (QoS) including required Bit Error Rate (BER), required information bit rate, message's delay constraints as well as traffic performance should be taken into account. A wireless multi-media system should achieve a flexible balance of these differences. In this letter, an Adaptive Chip/Bit Control Method is proposed for Wireless Multi-media CDMA System. The proposed method controls both chip and bit rate of each medium according to the offered traffic condition and the quality measurement of each medium. In the proposed method, measurement are carried out in the base station. Simulation results show that the proposed method not only maintain the required BER of each medium, but achieve a higher total throughput even in high traffic condition. Thus we see that the proposed method possesses higher flexible ability than conventional methods.

When multiple flows including continuous media streams are simultaneously sent from a computer, allocation and management of both processor capacity and network bandwidth need to be considered. We propose a framework of Quality of Service (QoS) management inside a sending host that controls execution of sending threads in consideration of utilization of processor capacity and network bandwidth. To distinguish from flows which require only best-effort service, we call a flow which requires a specific rate of service "reserved flow. " To guarantee QoS of such reserved flow both in processor- and network-intensive cases in a sending host, processor capacity reserve is allocated such that the rate of each reserved flow is attained and non-conforming data are policed before they are transmitted. Processor Capacity Manager and the network device driver exchange information in a cooperative manner to support the rate adaptive allocation of processor capacity reserve. In this paper, we describe design and implementation of our framework on RT-Mach. The results of performance evaluations demonstrate that our scheme performs well for full-duplex Ethernet.

This article proposes active-ATM, a flexible, simple and cost-effective ATM-WAN architecture that can handle multiple user-customized ATM-layer protocols, such as ABR and ABT, by using a simple universal ATM transit network. The proposed active-ATM architecture enables the construction of flexible networks that can evolve easily. With active-ATM and the ATM multi-protocol emulation network architecture called ALPEN, it is easy to implement new ATM-layer protocols by using user-created programs called active-program capsules that modify only the edge nodes. Because these user-sent program capsules can be used to quickly customize the edge nodes, there is no waiting for standardization and implementation of new services. The ATM-layer protocols are emulated only at the edge nodes, making the transit network independent of customer ATM-layer protocols. The active-ATM edge node is based on the flexible programmable node architecture called PUN(programmable unified node). The PUN is a platform for user-programmable ATM-layer services; it is achieved by using programmable devices, such as FPGAs and DSPs. An prototype system has demonstrated the flexibility of the resulting ATM network. The active-ATM architecture is an efficient approach to implementing multimedia, multi-protocol ATM services in an ATM WAN.

This paper presents a performance comparison between the single-stream and the multi-stream approaches to lip synchronization of live media (voice and video). The former transmits a single transport stream of interleaved voice and video, while the latter treats the two media as separate transport streams. Each approach has an option not to exert the synchronization control at the destination, which leads to four basic schemes. On an interconnected ATM-wireless LAN, we implemented the four basic schemes with RTP/RTCP on top of UDP and two variants which exercise dynamic resolution control of JPEG video. Making the performance measurement of the six schemes, we compare them to identify and evaluate advantages and disadvantages of each approach. We then show that the performance difference between the two approaches is small and that the dynamic resolution control improves the synchronization quality.

We have analyzed a displayed image of TFT-LCD three-dimensionally in case of low power drive using Multi-Field Driving Method (MFD). We have also proposed a concept of multi-media driving method using MFD in which a displayed image was divided into some interlaced subfield images and the number of interlaced subfields can be changed depending on the moving quantities of displayed images. This method made it possible not only to reduce a driving power consumption in case of still images to less than half, compared to that with conventional methods, but also to maintain high moving image quality.

DQRUMA (Distributed-Queueing Request Update Multiple Access) protocol has been proposed as an access protocol for the wireless ATM Local Area Networks. DQRUMA protocol is useful to transmit fixed-length packets (e. g. ATM cells). However, it cannot be applied to multimedia environment because it does not include any access control policy for multimedia traffic. In the paper, we propose a slot assignment scheme of DQRUMA protocol in wireless ATM LAN which supports integrated multimedia traffic with different service requirements. In this scheme we can allocate network resources according to the service requirements of each medium because the base station assigns Transmit-Permission flexibly according to the features of each medium.

This paper proposes a media synchronization mechanism for live media streams. The mechanism can also handle stored media streams by changing parameter values. The authors have implemented the mechanism on a lip-synch experimental system. Live video and voice streams input at a source workstation are transferred, and then they are synchronized and output at a destination workstation. This paper also evaluates the system performance such as mean square error of synchronization, average output rate, and average delay.

In this paper we propose a total quality evaluation method in an ATM network-type remote conference system, and describe the results of evaluations of a proving system. The quality of a remote conference system depends on such various elements as video images, voice signals, and cost; but a total quality index may be regarded as the cost of a remote conference system compared with that of a conventional face-to-face conference. Here, however, the decline in communication quality arising from the remote locations of participants must be included in the evaluation. Moreover, the relative weightings of voice signals, video images of participants, and shared data will vary depending on the type of conference, and these factors must also be taken into account in evaluations. An actual conference systems were constructed for evaluation, and based on a MOS (Mean Opinion Score) of the quality elements, the total system quality was evaluated with reference to the proposed concepts. These results are also described in this paper.

Integrating a 243 MHz dual-issue RISC processor core with a small set of dedicated hardware can create a single chip system for real-time encoding and decoding for MPEG2 MP@ML (main profile at main level). A trade-off between software and dedicated hardware is very important to decide performance of the system. This paper evaluates several MPEG2 encoding and decoding systems, focusing on both chip area and power consumption. For MPEG2 encoding, a newly introduced hybrid approach includes the processor core and the dedicated hardware that performs the discrete cosine transform (DCT), the inverse DCT (IDCT), variable length encoding (VLC) and block loading process. The estimated area for the encoder, 23. 0 mm2 using a 0. 3-micrometer 1-poly 4-metal CMOS process, is 33% smaller than that of the dedicated hardware approach. The estimated power consumption for the encoder is 13% smaller than that of the dedicated hardware approach. The dual-issue RISC processor approach has the advantage of a small chip area, low power consumption and that of being very easy to program for multimedia applications.

This paper presents the architecture of a newly-developed dual-issue RISC processor, D10V, that achieves both high throughput signal processing capability and maintains flexibility for general purpose applications. The RISC processor uses a 2-way VLIW architecture with a 32-bit wide instruction word. Two sub-instructions in a VLIW instruction are executed in two execution units in parallel. It also has several enhancements for signal processing. The processor includes pipelined multiply-and-accumulate instructions allowing a new multiply operation to be initiated every clock cycle and block repeat instructions for zero delay penalty loops. Single-cycle data moves of double-word data elements with modulo addressing are provided to deliver required memory bandwidth for signal processing applications. As a result, the D10V achieves high signal processing capability as 1 clock cycle per tap for FIR filtering. Also, several DSP benchmarks illustrate that the D10V competes favorably and in some instances outperforms conventional 16-bit DSPs. For master controlling application, the processor provides memory operations for signed/unsigned byte and bit wise operations. It shows 49 Dhrystone MIPS at 52 MHz, for general purpose applications.

This paper proposes a bitstream scaling technique for MPEG video for the purpose of media synchronizations. The proposed scaling technique can reduce the frame rate as well as the bit rate of an MPEG data sequence to fit them to the values specified by a synchronization system. The advantage of the proposed technique over existing scaling methods is that it is considering not only the performance of synchronization but also the picture quality of the resulting sequences. To further improve the quality of sequences scaled by the proposed method, this paper also proposes an MPEG encoding technique which sets some of the parameters suitable for the scaling. An experiment using these techniques in an actual media synchronization system has illustrated the usefulness of the proposed approach.