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The progress in computer and communication technologies is making the Internet increasingly heterogeneous in terms of network, hardware and software capacities. Moreover, resource availability on the Internet varies unexpectedly. Thus, providing an efficient access to multimedia services requires that multimedia streams be adapted according to the environment constraints. One approach to this issue is based on the use of intermediate nodes within the network to perform such adaptations (media transformations, protocol conversion and data transcoding) thus minimising intrusiveness with respect to legacy applications. Much research work has followed this approach, but lacks the flexibility required to fully address the issue. For this purpose, the authors designed and implemented a framework for network-based adaptations of multimedia streams. To reach the required flexibility, this framework provides support for dynamic configuration and reconfiguration of adaptations processes. A language called APSL (adaptation proxy specification language) allows the specification of such (re)configurations. A specification is translated into a component-based software architecture which evolves dynamically according to execution conditions. The authors describe the implementation of this framework on top of the Microsoft DirectShow® environment and report on a performance evaluation which demonstrates the effectiveness of the approach.
Date of Publication: 7 Oct. 2005