The explosive growth of multimedia data in online media repositories and social networks has led to the high demand of fast and accurate services for large-scale multimedia retrieval. Hashing, due to its effectiveness in coding high-dimensional data into a low-dimensional binary space, has been considered to be effective for the retrieval application. Despite the progress that has been made recently, how to learn the optimal hashing models which can make the best trade-off between the retrieval efficiency and accuracy remains to be open research issues. This thesis research aims to develop hashing models which are effective for image and video retrieval. An unsupervised hashing model called APHash is first proposed to learn hash codes for images by exploiting the distribution of data. To reduce the underlying computational complexity, a methodology that makes use of an asymmetric similarity matrix is explored and found effective. In addition, the deep learning approach to learn hash codes for images is also studied. In particular, a novel deep model called DeepQuan which tries to incorporate product quantization methods into an unsupervised deep model for the learning. Other than adopting only the quadratic loss as the optimization objective like most of the related deep models, DeepQuan optimizes the data representations and their quantization codebooks to explores the clustering structure of the underlying data manifold where the introduction of a weighted triplet loss into the learning objective is found to be effective. Furthermore, the case with some labeled data available for the learning is also considered. To alleviate the high training cost (which is especially crucial given a large-scale database), another hashing model named Similarity Preserving Deep Asymmetric Quantization (SPDAQ) is proposed for both image and video retrieval where the compact binary codes and quantization codebooks for all the items in the database can be explicitly learned in an efficient manner. All the aforementioned hashing methods proposed have been rigorously evaluated using benchmark datasets and found to outperform the related state-of-the-art methods.

This thesis reviews the usual properties and requirements for key agreement protocols. It then focuses on MIKEY, a work-in-progress protocol designed to conduct key agreements for secure multimedia exchanges. The protocol was implemented and incorporated in a SIP user agent - minisip. This implementation was used to measure the additional delay required for key exchange during call establishment. Finally, some schemes are proposed regarding the use of MIKEY in advanced VoIP scenarios, such as conferences and terminal mobility.

IPTV is gaining increasing attention. It is an expanding field where a lot of people are working hard to solve the problems that delay its wide-spread use. One major problem is that the existing IPTV distribution mechanisms do not seem to work well when applied on a large scale. Especially, IP multicast does not seem to meet the requirements of highly demanding IPTV services. In contrast, peer-to-peer architectures for distributing content have been available for a number of years (since the late 1990’s), and their success suggests that this is a promising alternative means of distributing content. Although peer-to-peer architectures are well known for file transfer, this kind of architecture has been used in this thesis for distributing streaming video flows. We combine results from two different approaches - IPTV and peer-to-peer systems - as part of our design and implementation of a new solution for distributing IPTV. Our proposal aims to avoid any weaknesses that the existing solutions have, whilst offering a viable solution for distributing live content. / Intresset kring IPTV ökar hela tiden, och många människor arbetar på att lösa de problem som hindrar området från att växa snabbt. Ett av huvudproblemen är att den existerande IPTV-distributionstekniken inte fungerar bra då den appliceras på stora lösningar. Bland de största problemen är att IP-Multicast inte möter de krav som marknaden ställer på global distribution av material. I motsats till detta har peer-to-peer teknik, som funnits sedan 90-talet, visat sin styrka för fil distribution på en mycket global skala på existerande infrastruktur. I denna uppstats kombinerar vi dessa två områden för att utröna vilka möjligheterna som finns för att optimera kostnaden för distrubition av live-tv samtidigt som vi försöker att undvika de svagheter som normalt associeras med de olika arkitekturerna. Vårt mål är att utnyttja de bästa egenskaperna från de olika teknikerna för att skapa en livsduglig och långsiktig lösning för TV-distribution.

Augmented reality, defined as a real-time direct or indirect view of a physical real-world environment that has been enhanced by adding digital computer generated information to it, is rapidly developing in terms of associated hardware (wearable displays, wireless mobile devices) and software (development platforms). AR enhanced instruction has been shown to provide cognitive and psychomotor support during procedural learning and has been shown to use both words and pictures when delivering instructional content.  A set of message design guidelines, created using a design and development research approach, can be used by novice designers to effectively manage the use of words and pictures while developing instructional applications for AR. / Ph. D.

A multimedia novel of speculative fiction exploring the mental health crisis in America.

Heutige Systeme zur Aufzeichnung von Lehrveranstaltungen arbeiten weitgehend automatisiert. Sie beschränken sich dabei nicht nur auf die reine Aufnahme einer Audio- oder Videospur, sondern sind in der Lage, Vorlesungsinhalte wie PowerPoint-Folien zu verarbeiten und diese mit Hilfe einer speziellen Wiedergabekomponente in geeigneter Form zu präsentieren. Mit dem an der Universität Osnabrück entwickelten virtPresenter- Framework existiert ein Vorlesungsaufzeichnungssystem, das alle Schritte von der Erstellung über die Aufbereitung der Aufzeichnungen bis zur Darstellung mit Hilfe einer Flash-basierten Abspielkomponente beherrscht. Mit den Fähigkeiten des Standards HTML5, der sich zur Zeit in der finalen Entwicklungsphase befindet und der von allen Browserherstellern in weiten Teilen bereits verwendet wird, steht eine neue Technologie zur Verfügung, die neue Möglichkeiten bei der Wiedergabe von multimedialen Inhalten im Webbrowser bietet, ohne dabei auf proprietäre Browser-Plugins wie den Flash-Player zurückgreifen zu müssen. Im Rahmen der dieser Arbeit wurde daher der web virtPresenter entwickelt, der eine Wiedergabekomponente für das virtPresenter-Framework darstellt, der die vielfältigen Möglichkeiten von HTML5 ausschöpft. Mit dem web virtPresenter ist es erstmals möglich, Vorlesungsinhalte plattformunabhängig einer größeren Nutzergruppe zugänglich zu machen. Das Hauptziel dieser Arbeit ist die Integration dieser entwickelten Wiedergabekomponente web virtPresenter in das soziale Netzwerk Facebook. Die Applikation social virtPresenter verknüpft das Angebot an hochwertigen Vorlesungsaufzeichnungen mit den Kommunikationsfunktionen eines sozialen Netzwerks. Der social virtPresenter bietet durch diese Kombination einen virtuellen Hörsaal, der es dem Benutzer möglich macht, von jedem Ort mit anderen Benutzern zusammen Vorlesungsaufzeichnungen zu betrachten und gemeinsam Vorlesungsinhalte zu lernen. Über Diskussionsforen, Wikis, Kommentar- und Chatsystem können die Nutzer jederzeit untereinander in Kontakt treten, um sich in einer Art virtuellem Hörsaal während der Wiedergabe einer Aufzeichnung untereinander über Vorlesungsinhalte auszutauschen. Ein besonderer Fokus dieser Arbeit liegt dabei auf den sozialen Konzepten des social virtPresenter. Ausgehend von der User Awareness werden die Kommunikationsmöglichkeiten der Benutzer untereinander beschrieben und klassifiziert, die die Grundlage für den social virtPresenter bilden. Neben der Software hat sich in den letzten Jahren aber auch die Hardware stark weiterentwickelt. Der aktuelle Trend entfernt sich derzeit vom klassischen Desktop-Computer und geht hin zu mobilen Tablet-Computern wie das iPad von Apple oder vergleich- baren Geräten mit dem Betriebssystem Android. Sie zeichnen sich einerseits durch eine hohe Mobilität aus, andererseits enthalten sie eine weit entwickelte Betriebssysteme, die inzwischen vollwertige Webbrowser enthalten, die die neuesten Technologien wie HTML5 bereits unterstützen. Daher wurde der web virtPresenter in die Tablet-kompatible Webapplikation mobile virtPresenter portiert, die speziell an die Bedienung durch Touch-Gesten angepasst ist, um dem Benutzer überall und jederzeit die Gelegenheit zu bieten, Vorlesungsaufzeichnungen schauen zu können.

This thesis describes two methods collectively called Time Series Generation (TSG) that can be used to generate time series inputs modeling packet loss to test IP-based streaming video software. The TSG methods create packet loss models that recreate the mean, variance, and autocorrelation signatures of an actual trace. The synthetic packet loss traces can have their inherent statistics altered, thus allowing for thorough testing of video software in ways that could not be done on actual networks. The two methods comprising TSG, which are individually called the primary and secondary method, use the principle of iterated uniformity to create a time series that attempts to match mean, variance, and autocorrelation. The two methods differ in their approach to generating autocorrelation. This leads to trade-offs between the two. The TSG methods are embodied in a software program called TSGen. An evaluation of TSGen is conducted, including a comparison with the well-known Autoregressive-To-Anything Generation algorithm (ARTAGEN) method and tool. The details of capturing packets and parsing video frame counts from packet streams are explained and demonstrated. Sixteen video stream traces were collected from a variety of sources and used to evaluate TSGen. Synthetic traces are generated for the sixteen original traces and both their summary statistics and autocorrelation signatures are compared against the originals. One of the sixteen traces is also compared against a synthetic trace generated using the ARTAGEN tool. Twelve out of the sixteen synthetic traces when compared to the actual traces had Least Square Error (LSE) values under 0.1, three were under 0.4, and the remaining one was under 1.1. Nine synthetic traces had their percent error differences between the mean and variance of the synthetic and actual traces below 5%, one was below 7%, four were under 18%, and the two remaining were at 41%. TSGen is able to effectively model autocorrelation, mean, and variance. Additional intangible benefits of TSG include adjustable run time for the matching process, with longer run time equating to better accuracy, and a simple theoretical model that was easily implemented.

Multimedia learning may be more effective than text-only methods. Researchers have not examined the effects of metacognitive strategies on self-regulated learning (SR) within multimedia learning environments (MLE). The purpose of this quasi-experimental study was to examine potential differences in learning and SR skills between students who use a script as a self-assessment tool and students who do not, while creating a conceptual map. The cognitive-affective theory of learning with media was used to frame the study. The sample included 87 secondary school students from a public school in Puerto Rico, enrolled in 11th and 12th grade English courses. Control and treatment groups completed a questionnaire to measure group difference in goal orientations at the beginning of the study. A t-test results indicated differences between the groups in disposition, and motivation variables. SR was measured before and after the implementation process through questionnaires. A 1-way ANOVA showed no differences in SR skills used by both groups. Results showed no differences in learning in both groups. A multiple regression was run to predict learning from group, disposition, and motivation variables. Results indicated the variable group as the most significant predicting the learning process. These results may encourage more research on SR strategies including a focus on different academic content, self-assessment instruments, and variables related to SR in MLE. These findings can contribute to positive social change in guiding teachers, students, and multimedia designers to develop MLE and SR processes to enhance student performance and obtain better academic results.

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