Multimedia stream adaptation services

Abstract

During the last decade, a clear trend towards all-over-IP multimedia communication has evolved. There exists a great variety of stationary and mobile devices which allow streaming of digital audio and video content over IP networks. But this variety of multimedia-enabled devices comes along with a great variety of different hardware and software capabilities and different access network technologies. Even if two applications support a common set of media formats, it is often impossible to use such a common format because of resource constraints imposed by the different hardware capabilities and network types. Existing media gateways handle only audio streams and they offer only static adaptation services, i.e., they do not adapt to changing network conditions, which may occur in networks without QoS guarantees. Furthermore, existing adaptation services support only a limited set of media formats and adaptation operations, and they are usually tightly coupled with a certain communication infrastruture. This thesis enhances the current state-of-the-art by developing a generic stream-adaptation service that supports a great variety of different adaptation operations, automatically adapts to changing resource availability, and can be easily enhanced with new functionality. Since specific service announcement mechanisms for adaptation services currently do not exist, a mechanism for describing stream-adaptation services is developed which enables the discovery of adaptation nodes suitable for specific types of adaptation operations. Using this service description, adaptation services may either be discovered and used directly by end users who are explicitly requesting certain adaptation operations, or they may be used by network operators and service providers to serve the customers´ needs transparently while optimizing the total network load. In the last part of this thesis, mechanisms for providing novel heterogeneous broadcast streaming services are elaborated.