published_or_final_version / Electrical Engineering / Master / Master of Philosophy

A new automatic compression scheme that adapts to any image set is presented in this thesis. The proposed scheme requires no a priori knowledge on the properties of the image set. This scheme is obtained using a unified graph-theoretical framework that allows for compression strategies to be compared both theoretically and experimentally. This strategy achieves optimal lossless compression by computing a minimum spanning tree of a graph constructed from the image set. For lossy compression, this scheme is near-optimal and a performance guarantee relative to the optimal one is provided. Experimental results demonstrate that this compression strategy compares favorably to the previously proposed strategies, with improvements up to 7% in the case of lossless compression and 72% in the case of lossy compression. This thesis also shows that the choice of underlying compression algorithm is important for compressing image sets using the proposed scheme. / x, 77 leaves ; 29 cm.

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Video surveillance today can look very different depending on the objective and on the location where it is used. Some applications need a high image resolution and frame rate to carefully analyze the vision of a camera, while other applications could use a poorer resolution and a lower frame rate to achieve it's goals. The communication between a camera and an observer depends much on the distance between them and on the contents. If the observer is far away the information will reach the observer with delay, and if the medium carrying the information is unreliable the observer has to have this in mind. Lost information might not be acceptable for some applications, and some applications might not need it's information instantly. In this master thesis, IP network communication for an automatic tolling station has been simulated where several video streams from different sources have to be synchronized. The quality of the images and the frame rate are both very important in these types of surveillance, where simultaneously exposed images are processed together. The report includes short descriptions of some networking protocols, and descriptions of two implementations based on the protocols. The implementations were done in C++ using the basic socket API to evaluate the network communication. Two communication methods were used in the implementations, where the idea was to push or to poll images. To simulate the tolling station and create a network with several nodes a number of Raspberry Pis were used to execute the implementations. The report also includes a discussion about how and which video/image compression algorithms the system might benefit of. The results of the network communication evaluation shows that the communication should be done using a pushing implementation rather than a polling implementation. A polling method is needed when the transportation medium is unreliable, but the network components were able to handle the amount of simultaneous sent information very well without control logic in the application.

This thesis consists of three parts, each of independent interest, yet tied together by the problem of matching with mismatches. In the first chapter, we present a motivated exposition of a new randomized algorithm for indexed matching with mismatches which, for constant error (substitution) rates, locates a substring of length m within a string of length n faster than existing algorithms by a factor of O(m/ log(n)). The second chapter turns from this theoretical problem to an entirely practical concern: delta compression of executable code. In contrast to earlier work which has either generated very large deltas when applied to executable code, or has generated small deltas by utilizing platform and processor-specific knowledge, we present a naïve approach — that is, one which does not rely upon any external knowledge — which nevertheless constructs deltas of size comparable to those produced by a platformspecific approach. In the course of this construction, we utilize the result from the first chapter, although it is of primary utility only when producing deltas between very similar executables. The third chapter lies between the horn and ivory gates, being both highly interesting from a theoretical viewpoint and of great practical value. Using the algorithm for matching with mismatches from the first chapter, combined with error correcting codes, we give a practical algorithm for “universal” delta compression (often called “feedback-free file synchronization”) which can operate in the presence of multiple indels and a large number of substitutions.

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Thesis (Ph.D.)--University of Melbourne, Dept. of Computer Science and Software Engineering, 2004. / Typescript (photocopy). Includes bibliographical references (leaves 247-263).

Thesis (M.S.)--Rochester Institute of Technology, 1988. / Includes bibliographical references.