The widespread use of personal multimedia-rich devices and multi-party video conferencing have made face-to-face communication among multiple users a promising feature. This thesis presents a multi-party conferencing solution with network coding naturally embedded. Our fundamental goal is to study if network coding brings benefits to multi-party conferencing. In this thesis, we first review an existing network coded solution for multi-party conferencing. Then, this solution is evaluated in our framework of evaluating a new transmission protocol for multi-party conferencing. Also, an investigation is set up to dive into the bottlenecks of this network coded solution. Next, an improved solution targeting conferencing services is proposed by tackling the bottlenecks of the existing solution. Based on our experiment results, it is found that network coding does bring benefits in the context of multi-party conferencing.

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Thesis (Ed. D.)--University of Toronto, 2004. / Adviser: Ruth Childs.

Thesis (M.A.)--University of Toronto, 2004. / Adviser: Jim Hewitt.

Thesis (Ed. D.)--University of Toronto, 2005. / Includes bibliographical references (leaves 205-214).

Thesis (Ed. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xi, 129 p. : ill. Includes abstract. Includes bibliographical references (p. 97-105).

This thesis investigates the development of a low cost, component based facial virtual conferencing system. The design is decomposed into an encoding phase and a decoding phase, which communicate with each other via a network connection. The encoding phase is composed of three components: model acquisition (which handles avatar generation), pose estimation and expression analysis. Audio is not considered part of the encoding and decoding process, and as such is not evaluated. The model acquisition component is implemented using a visual hull reconstruction algorithm that is able to reconstruct real-world objects using only sets of images of the object as input. The object to be reconstructed is assumed to lie in a bounding volume of voxels. The reconstruction process involves the following stages: - Space carving for basic shape extraction; - Isosurface extraction to remove voxels not part of the surface of the reconstruction; - Mesh connection to generate a closed, connected polyhedral mesh; - Texture generation. Texturing is achieved by Gouraud shading the reconstruction with a vertex colour map; - Mesh decimation to simplify the object. The original algorithm has complexity O(n), but suffers from an inability to reconstruct concave surfaces that do not form part of the visual hull of the object. A novel extension to this algorithm based on Normalised Cross Correlation (NCC) is proposed to overcome this problem. An extension to speed up traditional NCC evaluations is proposed which reduces the NCC search space from a 2D search problem down to a single evaluation. Pose estimation and expression analysis are performed by tracking six fiducial points on the face of a subject. A tracking algorithm is developed that uses Normalised Cross Correlation to facilitate robust tracking that is invariant to changing lighting conditions, rotations and scaling. Pose estimation involves the recovery of the head position and orientation through the tracking of the triangle formed by the subject's eyebrows and nose tip. A rule-based evaluation of points that are tracked around the subject's mouth forms the basis of the expression analysis. A user assisted feedback loop and caching mechanism is used to overcome tracking errors due to fast motion or occlusions. The NCC tracker is shown to achieve a tracking performance of 10 fps when tracking the six fiducial points. The decoding phase is divided into 3 tasks, namely: avatar movement, expression generation and expression management. Avatar movement is implemented using the base VR system. Expression generation is facilitated using a Vertex Interpolation Deformation method. A weighting system is proposed for expression management. Its function is to gradually transform from one expression to the next. The use of the vertex interpolation method allows real-time deformations of the avatar representation, achieving 16 fps when applied to a model consisting of 7500 vertices. An Expression Parameter Lookup Table (EPLT) facilitates an independent mapping between the two phases. It defines a list of generic expressions that are known to the system and associates an Expression ID with each one. For each generic expression, it relates the expression analysis rules for any subject with the expression generation parameters for any avatar model. The result is that facial expression replication between any subject and avatar combination can be performed by transferring only the Expression ID from the encoder application to the decoder application. The ideas developed in the thesis are demonstrated in an implementation using the CoRgi Virtual Reality system. It is shown that the virtual-conferencing application based on this design requires only a bandwidth of 2 Kbps. / Adobe Acrobat Pro 9.4.6 / Adobe Acrobat 9.46 Paper Capture Plug-in

The confluence of rapid technology developments in microelectronics, telecommunication, computers, networking and displays is making it possible to conceive of systems that offer new ways for people to interact and collaborate. Multi-user networking allows team collaboration for both application development and simulation while hardware and software modularity bring economy of scale. Advances in low power technologies and high energy density storage devices is making it possible to move these technologies off the desk and into the hands of mobile individuals. The human interface to these technologies is still largely unexplored but offers significant potential in applications that have a need for flexibility, improved information flow, and group participation at reduced costs. <p>This objective of this project is to develop a system that will increase performance and reduce costs associated with the interaction and collaboration of people who are remotely located from each other and who are engaged in team-oriented work. The Mobile Electronic Conferencing System (MECS) is designed to solve a problem facing a large (fictitious) manufacturing firm, Macropolis, that has a large percentage of mobile and distributedly located employees who need to confer and share data in real time. Macropolis is not unlike other large corporations that need to find new ways to promote more efficient collaborative work. <p>The concept of MECS is based upon rapidly accelerating trends in microelectronics, displays, telecommunications, computers, information management, etc. that will make it possible to construct an affordable, high value-added system for remote collaboration within the next decade. The approach taken in this project is to design a workable system using technology that is available now. While current technology is limited in bandwidth, resolution, human-computer interfaces, computational speed and energy efficiency for portable equipment, this project shows that a cost effective system can be designed and beneficially used today. The MECS is designed to be modular so that new technologies can be incorporated as they become available. The MECS can also serve as a testbed for evaluating alternatives and to gain a better understanding of human factors issues associated with the efficient use and social acceptability of remote, electronic-based, conferencing in the future. / Master of Science

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