Network and Grid Support for Multimedia Distribution and Processing
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| Year of publication | 2005 |
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| Description | In this thesis, we focus our work on two classes of multimedia data distribution and processing problems: synchronous or interactive, which require as low latency as possible, and asynchronous or non-interactive, where latency is not so restrictive. In Part I, we study scalable and user-empowered infrastructure for synchronous data distribution and processing. We propose a concept of a generalized user-empowered modular reflector called Active Element (AE). It supports both running as an element of a userempowered distribution network suitable for larger groups and also distributing the AE itself over tightly-coupled computer clusters. While the networks of AEs are aimed at scalability with respect to number of clients connected, the distributed AE is designed to be scalable with respect to bandwidth of individual data stream. We have also demonstrated both medium-bandwidth pilot applications suitable for both AE networks and high-bandwidth applications for distributed AEs. For AE networks, we have analyzed a number of distribution models suitable for synchronous data distribution, ranging from simple 2D full-mesh models through multiple spanning trees. All the models were evaluated both in terms of scalability and also in terms of robustness of operation with respect to AE failure and network disintegration. The most serious problem of distributed AE, where data is split over multiple equivalent AE units running in parallel, is packet reordering. We have designed and evaluated Fast Circulating Token protocol, which provides limited synchronization among egress sending modules of parallel paths in a distributed AE. While even the distributed AE with no explicit sending synchronization provides limited reordering, we have shown both theoretically and experimentally that FCT improves output packet reordering. Part II presents our approach to distributed asynchronous multimedia processing. We have designed efficient model for distributing asynchronous processing that is capable of very complex processing in real-time or faster, depending on degree of parallelism involved. The model is based on creating jobs with uniform size for parallel computing nodes without shared memory, as available in Grid environments. It uses distributed storage infrastructure as transient storage for source and possibly also target data. We have analyzed scheduling in such environment and found out that our problem with uniform jobs and non-uniform processors belongs to PO-class. When the distributed storage is connected with computing infrastructure via complete graph, the problem of scheduling tasks to storage depots belongs to the same class and thus scheduling as a whole is PO-class problem. In order to experimentally evaluate these models, a prototype implementation called Distributed Encoding Environment (DEE) has been implemented based on Internet Backplane Protocol distributed storage infrastructure. The prototype conrms expected behavior and performance. DEE has become used routinely by its pilot applications, most notably processing of lecture archives recordings, which provides multi-terabyte archives of video material for educational purposes. |
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