UBC Theses and Dissertations

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UBC Theses and Dissertations

Design, implementation and evaluation of a variable bit-rate continuous media file server Makaroff, Dwight J.


A Continuous Media File Server (CMFS) is a computer system that stores and retrieves data that is intended to be presented to a client application continuously over time. The primary examples of this kind of data are audio and video, although any other type of time-dependent media can be included (closed-caption text, presentation slides, etc). The presentation of these media types must be performed in real-time and with a low latency for user satisfaction. This dissertation describes the design, implementation and performance analysis of a file server for variable-bit-rate (VBR) continuous media. A CMFS has been implemented on a variety of hardware platforms and tested within a high-speed network environment. The server is designed to be used in a heterogeneous environment and is linearly scalable. A significant aspect of the design of the system is the detailed consideration of the variable bit-rate profile of each data stream in performing admission control for the disk and for the network. The disk admission control algorithm simulates reading data blocks early and storing them in memory buffers at the server, achieving read-ahead and smoothing out peaks in the bandwidth requirements of individual streams. The network algorithm attempts to send data early and reserves bandwidth only for the time that it is required. The algorithms are sensitive to the variability in the bandwidth requirements, but can provide system utilization that approaches 100% of the disk bandwidth achievable for medium length video streams in the test hardware environment.

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