Management of Layered Variable Bitrate Multimedia Streams over DiffServ with A Priori Knowledge
The Internet is developing with a very high speed. Just a few years ago, its main applications were file transfer and e-mail access, all based on the best effort TCP/IP service over quite slow links. With the quickly growing deployment of high-speed Internet accesses, there is a growing demand for also using the Internet in application scenarios like real-time multimedia streaming, particularly for audio and video on demand services. However, such multimedia applications do not only require sufficient bandwidth. They have stricter quality of service demands, like e.g. an upper bound on the transfer delay to ensure interactivity for their users. In the context of this thesis, a system for the cost-efficient transfer of variable bitrate multimedia streams over Differentiated Services (DiffServ) is presented and evaluated. This system supports layered transmission, i.e. streams may be partitioned into sub-streams denoted as layers (e.g. a video layer and an audio layer). Distinct layers may have different priorities as well as quality of service requirements and may therefore use different DiffServ classes for data transmission. Also, the streams may be scalable, i.e. the quality of the transferred media may be decreased in order to reduce the bandwidth requirements when bandwidth becomes scarce. Particularly, the system makes use of the fact that media files in e.g. a video on demand library can be analyzed a priorily. The information that is computed during the offline analysis is used to realize a dynamic and cost-efficient transport of layer data over different DiffServ classes. Furthermore, the system applies an adaptive buffering to smooth the flows – in order to save bandwidth – while also taking care of the delay constraints. Keywords: Multimedia, Quality of Service, Layered Transmission, DiffServ, A Priori Knowledge
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