Multimedia Database Systems as the tool to extract and generate additional values from multimedia 'Contents' are discussed in this paper with putting emphasis on the mediator functions between users and contents. Firstly, we discuss about 'what to do' from the view point of four promising contents sources: 'on the network,' 'in the digital broadcasting' 'in the library' and 'in the real world.' From this view pont, four types of multimedia database systems are defined. 'What to do' for each database system is also discussed. Two concrete multimedia database systems with unique mediator functions, stream-type multimedia database platform GOLS and the intelligent access and authoring system using multiple media synchronization are proposed with experimental evaluation results and concrete multimedia database applications.

This paper is concerned with spoken language translation in multimedia communication environment. We summarize the current research activities, by describing various spoken language translation systems and the multimodal technology related to spoken language translation. We propose a spoken language translation system that exploits the multimedia communication environment in order to overcome the limits caused by imperfect speech recognition. Our approach is in contrast to that of most conventional speech translation systems that limit their dialogue domains to obtain better speech recognition. We also propose a performance measure for spoken language translation systems. Our measure is defined as the ratio of the information quantities at each end of communication. Using this measure, we show that multimedia enhance spoken language translation systems.

In order to produce high quality multimedia contents efficiently, DTPP -desktop program production system- has been proposed. The DTPP is capable of supporting all the necessary procedures of program production, from planning to broadcasting, by molding each process into the desktop environment of program producers. The DTPP system consists of multimedia terminals, a media server, a computing server, and network system. In the DTPP, new technological concepts such as cooperative program production, indexing and utilization of attribute information of images, and video components and spatio-temporal editing will be installed.

This paper presents the design concept of the MEMORI, MHEG Engine for Multimedia information Object Retrieval and Interchange, which consists of three functional modules; the decoder, the object manager, and interpreter. Based on our modular design, the MEMORI has been implemented on the UNIX workstation. The menu-driven object generator has also been developed to generate the test objects conforming to the MHEG. Using the object generator, several multimedia/hypermedia test objects have been composed on the basis of presentation scenarios. The results show that the MEMORI correctly decodes, manages, and interprets the MHEG objects. The MEMORI can be utilized for the interactive multimedia server as well as the multimedia presentation system.

In this paper, the real-time scheduling mechanism which could support multimedia retrieval services more efficiently is investigated. In order to support multimedia service, the MEDF (modified earliest deadline first) algorithm that takes advantage of the priority queue and the virtual deadline mechanism is proposed. Additionally, its performance is analyzed and compared with conventional RR (round robin), FCFS (first come first serve), SS (sporadic server), MRF (minimum remained-time first), and EDF (earliest deadline first) algorithms. According to the simulation results, the proposed MEDF algorithm shows better performance than other scheduling algorithms in the multimedia environments.

Time-critical-communication, which should guarantee a time limit of a communication service is getting important in multimedia and factory automation fields. This paper proposes an IP-based protocol, Network Protocol with Performance (NPP) to provide the advanced best-effort service which takes a time constraint into account for real-time applications on the Internet. NPP uses the packet-scheduling function to make an effort to guarantee time constraints. Packet-scheduling algorithm chooses a packet in a NPP queue by a precedent level and a time constraint of each packet. We also discuss an application of NPP to multimedia communication system, and investigate performance of NPP by simulation.

In this paper, we describe the design and implementation of a hypermedia system that has the following characteristics. First, being designed according to the Dexter hypertext reference model, it has a layered architecture and thus maintains commonality with other hypermedia systems based on the Dextermodel. Second, being designed based on the MHEG standard, it has data structures that are inherently suitable for data interchange and synchronization. Third, adopting the MIME protocol, it provides multimedia mail services. Finally, being built on top of an object-oriented DBMS, it makes it easy to represent Dexter and MHEG models and also provides efficient storage and search capabilities. The contribution of this paper is combining these characteristics to build an integrated hypermedia system reflecting reference architectures and international standard efforts.

In this paper, we show that by suitably selecting a notation to construct synchronization requirement specifications (SRS) for multimedia presentation we can express the timing characteristics at an abstract level, verify the specification, and obtain a hardware implementation through a sequence of transformations of the specification. First, we introduce the notion of a well-formed SRS and its hardware model. Second, we model an SRS as a timed Petri net and interpret the transitions of the net as hardware signals. To obtain logic functions from the SRS, we simplify the net and obtain a signal transition graph satisfying the unique state coding property. Finally, we show how to obtain a logic-level design of synchronizers.

Multimedia communications, fast growing industry in the world and in Korea, require advanced technology in network, computer, device, and application software. Korean government and industries prepare for this huge opportunity by commitment to national R&D programs. While investing heavily on present multimedia products, private companies also support R&D on future multimedia technologies. This paper surveys key R&D efforts in Korea by programs and organizations.

When people watch such motion pictures as documentaries or educational-type films, it is very natural for them to be interested in moving objects in the movies and be eager to know the detailed information related to these object. Therefore, a mechanism that enables users to directly pick up object information from motion pictures is necessary to make a movie system feasible. For this reason, we are researching techniques on using objects in motion pictures as hypermedia anchors. We call a movie system that provides the above mechanism a video hypermedia system. An object in a motion picture can generally be considered as a complex object which includes many parts. To allow users to obtain information related to each part, a system must be able to provide anchors corresponding to each part in each complex object. For this, authors cannot help defining all anchors in all frames, since the visual status of each part varies from moment to moment. This paper presents our approach for managing objects in motion pictures for video hypermedia systems. The main feature of the proposed method is to apply computer graphic techniques to the defining of anchors for a complex object.

This paper illustrates activities and accomplishments being made by DAVIC, a non-profit organization pushing forward its open, international, cross-industry standards for audio-visual information systems, of which video-on-demand is the representative. Core technologies selected in its firstly published specifications and their interoperability aspects are summarized here. Preliminary results in our interoperability testing are also shown. Finally, we touch upon the coming work plan of DAVIC which covers wider range of access network capabilities and service domains, e.g. internet.

Storage system in a multimedia server must satisfy two contradicting requirements: real-timeliness and large number of parallel user requests. Efficient algorithms for data placement, disk head scheduling, and request admission control schemes are needed to support the requirements. In this paper, we propose efficient schemes to maximize system resource utilization and service availability: cyclic placement scheme, subgroup retrieval scheme, and measurement-based request admission control scheme. Performance analysis through simulation revealed that the amount of system buffers required can be reduced by 70% approximately.

This letter proposes ALPEN, a simple, flexible and cost effective ATM-WAN architecture that emulates multiple ATM-layer protocols at the edge nodes. Any new ATM-layer protocol can be easily implemented by modifying only the edge nodes. The transit network is simple and independent of the protocols emulated, and ALPEN has a short response time. It is very suitable for implementing multimedia ATM networks.

Multiple TDMA bursts assignment between a base station and a personal terminal will be required for multimedia communications that offers high speed signal transmission such as voice and data simultaneous transmission. This paper proposes a reliable packet transmission method for TDMA based wireless multimedia communications. The proposed method employs an adaptive transmission rate control according to the packet length and a burst diversity technique is applied to improve the frame error rate of a packet. The frame error rate performance has been approximated theoretically by using fade- and infade-duration statistics of a Rayleigh fading channel and a computer simulation has been carried out for two control channels, FACCH/SACCH (Fast/Slow Associated Control CHannel) in the PHS as well as GSM. Both results indicate that the frame error rate is dramatically improved, about one order, when two bursts have different frequency and improved by about 25% when the two bursts have the same frequency.

This paper reports experimental results of a media synchronization mechanism which was proposed by the authors, focusing on the graceful recovery scheme. The proposed method consists of intra-stream and inter-stream synchronization mechanisms. The inter-stream synchronization control is performed after the intra-stream synchronization control over each media unit (MU) such as a video frame. Then, whether the intra-stream synchronization is still maintained or not is checked. In the experimental system, video and voice stored in a source workstation are transferred to a destination workstation via an FDDI network, and then they are synchronized and outputted at the destination (i.e., lip-synch). At the transmission of each MU, we simulate network delay jitters by generating a pseudo-delay which is exponentially distributed. Using the system, we have confirmed the validity of the mechanism. We also clarify how to set the threshold and parameter values defined in the mechanism by evaluating mean square error and average MU rate or by subjective assessment. Furthermore, we demonstrate that the intra-stream synchronization control for each streams in addition to the inter-stream control is necessary for high quality synchronization.

This paper discusses key technologies for intelligent radio transmissions and intelligent network constitution techniques for advanced wireless communication systems. In the former part, this paper discusses the intelligent radio transmission techniques, in which the adaptive modulation techniques are mainly introduced because it is very effective to intelligently assign radio resources to each terminals as well as to intelligently control radio transmission parameters under dynamically changing traffic, required quality of services (QOS), and channel conditions. In the latter part, this paper discusses intelligent networking techniques, in which autonomous radio networking techniques and IP address control techniques for mobile host in the Internet are introduced to obtain suggestions for future intelligent and robust networking technologies.

We thought that multiple skeletons were inherent in an ordinary three-dimensional object. A thinning method is developed to extract multiple skeletons using 333 templates for boundary deletion based on the hit or miss transformation and 222 templates for checking one voxel thickness. We prepared twelve sets of deleting templates consisting of total 194 templates and 72 one voxel checking templates. One repetitive iteration using one sequential use of the template sets extracts one skeleton. Some of the skeletons thus obtained are identical; however, multiple independent skeletons are extracted by this method. These skeletons fulfill the well-recognized three conditions for a skeleton. We extracted three skeletons from the cube, two from the space shuttle model and four from the L-shaped figure by Tsao and Fu. The digital medial skeleton, which is not otherwise extracted, is extracted by comparing the multiple skeletons with the digital medial-axis-like-figure. One of our skeletons for the cude agreed with the ideal medial axis. The locations of the gravity center of the multiple skeletons are compared with that of the original shape to evaluate how uniform or non-biased skeletons are extracted. For the L-shaped figure, one of our skeletons is found to be most desirable from the medial and uniform points of view.

This paper investigates the problems which inhibits the use of today's WDM networks. These are propagation delay, packet processing overhead, bit & frame synchronization, and tuning latency. So far, these problems, especially propagation delay, have been ignored in most performance analysis papers. They have always hindered network designers, but they are magnified by the order of magnitude increase in speed of optical communications systems as compared to previous media. This paper examines the impact of the propagation delay on the performance of WDM protocols with variations in the number of channels, packet length and system size, specifically in two reservation based protocols with control channels and two pre-allocation protocols without the control channels. Also the impact of three delay factors (packet processing overhead, bit & frame synchronization and tuning latency) are studied with different propagation delay parameters. In reservation protocols, each node has one agile transmitter and two receivers; one of them is fixed and the other one is agile. The fixed receiver continuously monitors the control channel, receives all control packets, and updates their own status tables in order to track the availability of the other nodes as a target and data channels to avoid the destination collisions and the data channel collisions, respectively. In pre-allocation protocols, each node has a tunable transmitter, a fixed or slow tunable receiver, and its own home channel to receive the packets. The performance of this protocol is evaluated through the discrete-event simulation in terms of the average packet delay and network throughput.

This paper discusses an object-oriented approach to temporal multimedia data modeling in OMEGA; a multimedia database management under development at the University of Library and Information Science. An object-orientated approach is necessary to integrate various types of heterogeneous multimedia data, but it has become clear that current object-oriented data models are not sufficient to represent multimedia data, particularly when they are temporal. For instance, the current object-oriented data models cannot describe objects whose attribute values change time-dependently. Also, they cannot represent temporal relationships among temporal multimedia objects. We characterize temporal objects as instances of a subclass of class TimeInterval with the temporal attributes and the temporal relationships. This temporal multimedia data model is designed upward compatible with the ODMG-93 standard object model. To organize a temporal multimedia database, a five temporal axes model for representing temporal multimedia objects is also introduced. The five temporal axes--an absolute, an internal, a quasi-, a physical, and a presentation time axis--are necessary to describe time-dependent properties of multimedia objects in modeling, implementing and use. A concrete example of this organization method is also illustrated.

A particulate recording medium with an ultrathin magnetic layer is presented in this paper. This medium consists of a magnetic layer and a nonmagnetic underlayer composed of very fine titanium dioxide powder. When metal powder was employed, we observed the anticipated advantages of decreasing the thickness of the magnetic layer in tapes and diskettes. By reducing the layer thickness to below 0.3 µm we were able to increase the reproduced output at short wavelengths, and improve both the overwrite erasability and the D50. There was also a decrease in the half peak width of an isolated pulse and a peak shift. Tribological advantages were also observed with this medium. When barium ferrite was employed as the magnetic powder, we observed that the modulation noise of thin-layer barium ferrite medium was less than that of a thinlayer MP medium while it generated an output as high as that of the MP medium. The advantages of the barium ferrite medium lie in its two-layer construction. Particulate media will continue to develop as magnetic powder is improved mainly in terms of its size, saturation magnetization, and coercivity.