Scheduling multimedia presentations in educational digital libraries

An educational digital library is a specialized digital library containing instructional materials, such as class lectures, seminar presentations, and various training materials. These materials consist of a combination of audio, video, and image data. In such an environment, basic parts of multimedia data are usually stored in databases and sophisticated multimedia presentations may be assembled to generate various presentations. In this paper, we investigate a theory of the scheduling strategies for supporting the synchronized presentations of multimedia streams which is applicable to educational digital libraries. This scheduling theory includes the specification and representation of synchronization on media streams, the realization of appropriate synchronization granularity, and the scheduling principles for the presentations of multimedia streams. This investigation formulates criteria for specifying and scheduling the skipping/pausing of media streams with asynchronous presentations when various delays occur. Adaptability to various quality-of-service requirements is supported in the scheduling strategies. Various synchronization mechanisms at both client and server sides are proposed to implement the scheduling theory. Experimental analysis is conducted using instructional materials.     

Online algorithms for advance resource reservations

We consider the problem of providing QoS guarantees to Grid users through advance reservation of resources. Advance reservation mechanisms provide the ability to allocate resources to users based on agreed-upon QoS requirements and increase the predictability of a Grid system, yet incorporating such mechanisms into current Grid environments has proven to be a challenging task due to the resulting resource fragmentation. We use concepts from computational geometry to present a framework for tackling the resource fragmentation, and for formulating a suite of scheduling strategies. We also develop efficient implementations of the scheduling algorithms that scale to large Grids. We conduct a comprehensive performance evaluation study using simulation, and we present numerical results to demonstrate that our strategies perform well across several metrics that reflect both user- and system-specific goals. Our main contribution is a timely, practical, and efficient solution to the problem of scheduling resources in emerging on-demand computing environments.     

Retrieval scheduling for collaborative multimedia presentations

The single-system approach is no longer sufficient to handle the load on popular Internet servers, especially for those offering extensive multimedia content. Such services have to be replicated to enhance their availability, performance, and reliability. In a highly replicated and available environment, server selection is an important issue. In this paper, we propose an application-layer broker (ALB) for this purpose. ALB employs a content-based, client-centric approach to negotiate with the servers and to identify the best server for the requested objects. ALB aims to maximize client buffer utilization in order to efficiently handle dynamic user interactions such as skip, reverse presentation, go back in time. We also present details of a collaborative multimedia presentation platform that we have developed based on ALB.     

True multimedia presentations: A case study

This paper describes work undertaken as part of a three-stranded project. The main deliverable will be a suite of software tools, classes and components, as well as teaching resources and methodologies to facilitate the production of intelligent multimedia tutoring systems.

The three strands of this project explore differing aspects of multimedia, and while they stand as separate pieces of work in their own right, they also form the building blocks of the final deliverable, which is an intelligent tutoring system. Intermediate outcomes include a multimedia shell and the Manley Group Demonstrator.

This paper focuses on the design and development of the “true multimedia” demonstrator that has now reached the stage of being a fairly mature prototype. It is used commercially by a communications company to illustrate the varying levels of sophistication which can be achieved in presentation systems and provides an exemplar demonstrating the varying degrees of functionality possible using current technology. The main requirement in the design and implementation has been usability both for end users and content developers.

Real-time control of the multimedia devices is achieved using sophisticated software which is tightly integrated with dedicated control hardware. The software can be used to produce canned presentations or highly interactive systems.

The system is installed in a dedicated presentation suite, thus allowing the true nature of multimedia to be demonstrated. It is scaleable in that it can be used to produce stand-alone portable solutions, highly interactive touch-screen controlled applications or complete multi-device high end presentations. This is achieved using the appropriate combination of software tools and hardware for a specific application.

Macromedia Director is used to produce visual and creative material for the system, while Macromedia Authorware can be used to provide interactivity. © 1997 Elsevier Science B.V.     

Retrieval in multimedia presentations

In this paper we discuss issues concerning the consistent retrieval of parts of multimedia presentations from multimedia repositories. We introduce a class of multimedia presentations made of independent and synchronized media and discuss retrieval requirements of presentation fragments. Then we discuss a retrieval model capable of reconstructing the fragments of a presentation from the atomic components returned by the execution of queries to multimedia presentation repositories. The retrieval model is based on an automaton that formally describes the presentation states entered by the events that trigger media playback. Retrieving a consistent fragment corresponds to building a new presentation with all the media related to the retrieved ones, with their original structural and synchronization relationships.     

A framework for synchronous delivery of time-dependent multimedia data

Multimedia data often have time dependencies that must be satisfied at presentation time. To support a general purpose multimedia information system, these timing relationships must be managed to provide utility to both the data presentation system and the multimedia author. Timing management encompasses specification, data representation, temporal access control, playout scheduling, and run-time intermedia synchronization. In this paper we describe the components of our framework for supporting time-dependent multimedia data encompassing these areas and how they are assembled into a unified system.     

Intelligent multimedia layout: A reference architecture for the constraint-based spatial layout of multimedia presentations

With increases in the complexity and dynamics of multimedia information communicated by current applications, there arises a corresponding need towards a standard technology for intelligent multimedia interfaces. In this article, we address those components of an intelligent multimedia presentation system (IMMPS) which deal with the design and the realization of spatial layout. We treat multimedia layout as a multidimensional constraint problem and propose a reference architecture for a general-purpose intelligent multimedia layout manager (IMMLM) that is based on a dedicated constraint solver kernel.     

Delivering presentations from multimedia servers

Most multimedia servers reported in the literature are designed to serve multiple and independent video/audio streams. We think that, in future, multimedia servers will also serve complete presentations. Multimedia presentations provide unique opportunities to develop algorithms for buffer management and admission control, as execution-time consumption requirements of presentations are known a priori. In this paper, we examine presentations in three different domains (heavyweight, middleweight, and lightweight) and provide buffer management and admission control algorithms for the three domains. We propose two improvements (flattening and dynamic-adjustments) on the schedules created for the heavyweight presentations. Results from a simulation environment are presented. Received June 9, 1998 / Accepted October 13, 1998     

An algebra for creating and querying multimedia presentations

Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared by different individuals and organizations. In this paper, we present an algebra for creating and querying interactive multimedia presentation databases. This algebra operates on trees whose branches reflect different possible playouts of a set of presentations. The algebra not only extends all the classical relational operators to such databases, but also introduces a variety of novel operators for combining multiple presentations. As our algebra supports merging parts or all of existing presentations, this algebra can also be used as an authoring tool for creating multimedia presentations. We prove a host of equivalence results for queries in this algebra, which may be used to build query optimizers for interactive presentation databases.     

A model for specification and synchronization of data for distributed multimedia applications

As network technology provides the capability to handle multimedia traffic and the demand of multimedia services increases, protocols are required for effective communication of multimedia data in a distributed environment. Synchronization is one of the key issues in a multimedia system. Most of the current approaches do not support an integrated solution to the problem of synchronization. In this paper we propose a mechanism for synchronization of multimedia data in distributed environment where the accuracy of the protocol can be tailored to the application. The system model supports live and video-on-demand service. We present a scheme where the specification of the temporal requirements provided by the application can be directly mapped to obtain the information necessary to enforce the synchronization required. We present two examples of specifying the temporal requirements and process of obtaining the information and present performance results of our simulation studies.     

一种基于J2EE的异构数据库的同步方法

随着信息化发展和网络与计算机技术的广泛应用,企业或者部门间信息互通共享重要性,文章提出了一种基于J2EE的异构数据库间实现数据同步的方法,该方法在运用数据库触发器的基础上,运用java语言编写同步逻辑脚本,并将同步技术成功应用于某企业ORACLE与SQL Server数据库数据同步中。     

Context-aware adaptation of multimedia documents for consistent presentations

We propose in this paper a context-aware adaptation technique for SMIL encoded multimedia documents. Our approach is mainly dedicated to run in compile-time but we discuss also how it can be used in runtime. Our algorithm aims at improving the execution of a multimedia presentation. This is achieved by scheduling object pre-fetchings in the presentation while monitoring bandwidth and memory space availabilities. For this effect, a request pattern computed from the temporal graph of the SMIL specification is exploited in order to apply an optimal policy to select which objects should be pre-fetched, real time delivered or discarded, even. The algorithm can be used as a tool to evaluate and to monitor the QoS of a presentation. At compile time, it makes it possible to assess whether the QoS of a presentation can be guaranteed after enforcing specific context-oriented adaptations. At authoring stage, this algorithm can be used, for instance, to produce different alternative sub-codes, such that each one is adapted to run in a specific context. In runtime, the algorithm can provide a mechanism to monitor the elastic time computation in case of a mismatch occurrence. In order to advocate our proposal, some experimentation results performed on a simulation platform are reported.     

Canonical processes for creating personalized semantically rich multimedia presentations

Authoring of multimedia content can be considered as composing media assets such as images, videos, text, and audio in time, space, and interaction into a coherent multimedia presentation. Personalization of such content means that it reflects the users’ or user groups’ profile information and context information. Enriching the multimedia content with semantically rich metadata allows for a better search and retrieval of the content. To actually create personalized semantically-rich multimedia content, a manual authoring of the many different documents for all the different users’ and user groups’ needs is not feasible. Rather a (semi-)automatic authoring of the content seems reasonable. We have analyzed in detail today’s approaches and systems for authoring, personalizing, and semantically enriching multimedia presentations. Based on this analysis, we derived a general creation chain for the (semi-)automatic generation of such content. In this paper, we introduce this creation chain. We present our software engineering support for the chain, the component framework SemanticMM4U. The canonical processes supported by the creation chain and SemanticMM4U framework are described in detail. We also provide an explicit mapping of SemanticMM4U framework components to the processes and argue for the benefits of defining canonical processes for creating personalized semantically rich multimedia presentations.     

Conceptual modeling of multimedia objects for user-tailored information presentations

This paper presents a formal framework for the representation of knowledge concerning the use of multimedia information in the context of designing user-tailored information presentations. The aim is to support efficient development and maintenance of knowledge bases and effective utilization of knowledge for adaptive information presentations. It is conjectured that a hybrid knowledge representation framework that mixes formal knowledge structures with canned fragments of multimedia information and distinguishes between categories of medium-independent information items and types of presentation forms comprehensively can achieve this aim. The framework supports subject-based classification of reusable multimedia objects and their utilization according to presentation intentions and to pragmatic constraints. This approach, although it is considered complementary, contrasts to approaches that require systems to build every presentation from scratch.     

TAO: Temporal Algebraic Operators for modeling multimedia presentations

This paper presents TAO: a language based on Temporal Algebraic Operators for composing complex multimedia presentations. Unlike traditional approaches used to specify multimedia presentations, TAO relies on a well-defined semantics with an underlying temporal model based on intervals and causal relations between time points. We derive some properties of TAO presentations and show how to execute TAO presentations on an execution engine: a TAO presentation is compiled into a set of instructions interpreted by the execution engine.     

Tactus: toolkit-level support for synchronized interactive multimedia

Tactus addresses problems of synchronizing and controlling various interactive continuous-time media. The Tactus system consists of two main parts. The first is a server that synchronizes the presentation of multiple media, including audio, video, graphics, and MIDI at a workstation. The second is a set of extensions to a graphical user interface toolkit to help compute and/or control temporal streams of information and deliver them to the Tactus Server. Temporal toolkit objects schedule computation events that generate media. Computation is scheduled in advance of real time to overcome system latency, and timestamps are used to allow accurate synchronization by the server in spite of computation and transmission delays. Tactus supports precomputing branches of media streams to minimize latency in interactive applications.