Elsevier

Computer Communications

Volume 25, Issue 2, 1 February 2002, Pages 169-182
Computer Communications

Continuous media support in the distributed component object model

https://doi.org/10.1016/S0140-3664(01)00381-4Get rights and content

Abstract

The demand for a great variety of sophisticated telecommunications services with multimedia characteristics is increasing. This trend highlights the need for the efficient creation of distributed programs with multimedia data exchanges running on distributed processing environments. Therefore, it is necessary to support the object-oriented development of distributed multimedia applications in a flexible manner. This paper recognises Microsoft's Distributed Component Object Model (DCOM) as a key potential technology in the area of service engineering and examines a structured approach to enhance it for the handling of continuous media streams through the design and implementation of a collection of suitable multimedia support services. The proposed approach focuses on the modelling of continuous media communications in DCOM and is validated through the design and implementation of a multimedia conferencing service. Though the approach is targeted to DCOM, the paper lays a set of concrete concepts for realising stream interfaces in distributed object platforms.

Introduction

Driven by technological advances, market growth and deregulation, the global telecommunications industry is rapidly adopting a highly dynamic and open character, which, in combination with the evolving synergy between information and telecommunication technologies, provides a wide range of opportunities for the delivery of advanced multimedia telecommunications services (also referred to as telematic services). Based on recent developments in object orientation and distributed computing, these telecommunications services are designed, realised, and deployed as multimedia applications operating on distributed computing platforms [17].

These platforms are object-oriented Distributed Processing Environments (DPEs), which provide a uniform distributed computational model, isolating service designers and developers from the heterogeneity of underlying systems (i.e. different networks, end-systems, communication protocols, operating systems, and programming language environments), and thus hiding many of the complexities encountered in building distributed software [1]. However, there are key application areas in which distributed object platforms have lagged behind ad-hoc approaches to building distributed applications. In particular, support for distributed multimedia applications is weak or non existent in the most important of today's distributed object products.

Despite the fact that multimedia support has been considered in general terms in the ISO's/ITU-T's Reference Model for Open Distributed Processing (RM-ODP) [7], [12], it has not yet been examined in Microsoft's Distributed Component Object Model (DCOM) [3], and is not yet mature in the Object Management Group's (OMG) Common Object Request Broker Architecture (CORBA) [11], [18], [19]. Recently, a wide range of new telecommunications services are becoming increasingly popular by employing video to convey information and to enhance communication among human users (e.g. videoconferencing, video on-demand, interactive teletraining, etc.). Therefore, in the emerging multi-vendor, multi-stakeholder telecommunications environment, it is necessary to facilitate the rapid and flexible deployment of a great diversity of multimedia, multi-party services by providing support for continuous media in DPEs. The role of DCOM is expected to be important as it is one of the promising distributed object platforms for service engineering. Key advantages are its ubiquity and the fact that it supports key DPE features such as multiple interfaces per object and object groups [2].

This paper presents an approach which extends DCOM to an environment suitable for the development of advanced multimedia telecommunications services. More specifically, it examines central issues associated with the provision of object-oriented support in DCOM for the handling of continuous media in terms of representation, transmission, and management. The proposed approach is validated through the design and implementation of a multimedia conferencing service. Finally, experiments are conducted in order to assess the flexibility and efficiency of the proposed approach and conclusions are drawn.

Section snippets

Modelling multimedia telecommunications services

Multimedia computing is concerned with the integration of a variety of media types (text, graphics, still images, animation, motion video, voice, sound) into a single coherent computing environment, while multimedia communication involves the interaction of devices which can deal with networked suppliers and consumers of various types of digitally represented information [20]. The tasks broadly involved in this process can be divided into the coding and transport of the different media, and

Enhancing DCOM for the support of continuous media

DCOM is the distributed extension to COM (Component Object Model) that builds an Object Remote Procedure Call (ORPC) layer on top of DCE RPC to support remote objects. In general, DCOM provides all the necessary facilities for the integration of heterogeneous components in a distributed environment [3], [8].

However, DCOM does not satisfy the more complicated and stringent requirements of handling multimedia streams. To enable DCOM to be the basis for new telecommunications services which

Validation and experimentation

The proposed multimedia support infrastructure and the related API have been tested in several simple scenarios (such as the one depicted in Fig. 7) involving different configurations of source and sink devices associated by various stream connections. It has been found that they constitute a viable, flexible, consistent, coherent, and relatively intuitive way of building multimedia telecommunications services in DCOM.

To verify and reinforce these results under (more) realistic conditions, and

Conclusions

There is a technology push in the area of multimedia communications, which is acting as a catalyst for the specification and development of new multimedia telecommunications services. These services will be deployed in a distributed object environment. Therefore, there is an increasingly important need for distributed object platforms to support continuous media interactions in a flexible manner.

Recognising this need, OMG attempts to promote the use of continuous media in CORBA DPEs, by

Acknowledgements

Although this work did not explicitly take place in the context of an EU ACTS project, it has been influenced by work on stream interfaces and DPEs in general in the ACTS ReTINA and VITAL projects, which have in turn relied on the TINA DPE architectural principles.

References (25)

  • V Gay et al.

    Multimedia in the ODP-RM standard

    IEEE Multimedia

    (1997)
  • R Grimes

    Professional DCOM Programming

    (1997)

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