Empirical Evaluation of Boundary Policies for Wavelet-Based Image Coding

The wavelet transform has become the most interesting new algorithm for still image compression. Yet there are many parameters within a wavelet analysis and synthesis which govern the quality of a decoded image. In this paper, we discuss different image boundary policies and their implications for the decoded image. A pool of gray-scale images has been wavelet-transformed with different settings of the wavelet filter bank and quantization threshold and with three possible boundary policies. Our empirical evaluation is based on three benchmarks: a first judgement regards the perceived quality of the decoded image. The compression rate is a second crucial factor. Finally, the best parameter settings with regard to these two factors is weighted with the cost of implementation. Contrary to the new standard JPEG-2000, where mirror padding is implemented, our investigation proposes circular convolution as the boundary treatment

Videoconferencing Offers More than Audio and Video – Making Creative Animation Artists Collaborate between Remote Offices

For more than forty years, since videoconferencing was introduced for telecommunication, researchers and market analysts have been predicting a new era of communication, that distance might soon become insignificant in human communication, and forecasting a virtualisation of work places and communities. Today, the shortcomings of telecommunication systems have been acknowledged: people still travel to meet each other face to face in order to improve the perception of sharing time and space, the establishment of common ground, awareness and presence perception. However, this paper suggests that for specialised purposes in confined environments, technology does indeed offer the promise to allow people collaborate intensively over a distance. We present a user study about how creative digital animation artists collaborate in a current co-located situation in the digital media production industry before we enter a discussion of hardware choices and user control interface design for the purpose of creating a non-intrusive, spontaneity-enabling high-quality videoconferencing system between their workspaces

Layered Wavelet Coding for Video

Video coding for Internet applications faces major challenges. Due to the heterogeneity of the network, users with very different access bandwidths to the Internet want to be satisfied by the highest possible quality of their real-time application. A good coding scheme for layered video asks for maximization of the subjective visual quality at a given bandwidth, for scalability and coding complexity. In this article, we discuss and evaluate different policies for layered wavelet video coding. A heuristic of the actual bit rate originating from our implementation, the degree of scalability, and the visual quality of the coded video lead us to pronounce parameter setting recommendations

Lehrszenarien-übergreifende Erzeugung und Verwendung Multimedialer Teachware

Das Erstellen multimedialer Lehrdokumente ist ein aufwendiger Prozeß. In der traditionellen Lehre werden für verschiedenen Lehrszenarien (Vorlesung, Nachbearbeitung durch den Studenten, etc.) oft unterschiedliche Dokumente erstellt, die denselben Stoff behandeln. Weiterhin entstehen während einer Vorlesung durch die Erklärungen des Dozenten implizit Dokumente, die auch in anderen Lehrszenarien sinnvoll eingesetzt werden können. In diesem Artikel wird beschrieben, wie die in Lehrveranstaltungen entstehenden Dokumente aufgezeichnet und auf einem Server bereitgestellt werden. Mit dem vorgestellten Verfahren können die Aufzeichnungen flexibel mit zusätzlichen multimedialen Inhalten zu einer Computer-Based-Training-Einheit verknüpft werden. Dadurch ist es möglich, Dokumente effektiv sowohl in synchronen als auch in asynchronen Lehrszenarien zu einzusetzen

Wavelet Filter Evaluation for Image Coding

The wavelet transform has become the most interesting new algorithm for still image compression. Yet there are many parameters within a wavelet analysis and synthesis which govern the quality of a decoded image: decomposition strategy, image boundary policy, quantization threshold, etc. In this paper we discuss different image boundary policies and their implications for the decoded image. A focal point is the trade-off between the length of an orthogonal, compactly supported Daubechies-n wavelet filter bank and the decomposition depth of an image during analysis. An evaluation of the visual quality of images at different parameter settings leads to recommendations on the wavelet filter parameters to be used in image coding

Multimedia Applications of the Wavelet Transform

This dissertation investigates novel applications of the wavelet transform in the analysis and compression of audio, still images, and video. Most recently, some surveys have been published on the restoration of noisy audio signals. Based on these, we have developed a wavelet-based denoising program for audio signals that allows flexible parameter settings. The multiscale property of the wavelet transform can successfully be exploited for the detection of semantic structures in images: A comparison of the coefficients allows the extraction of a predominant structure. This idea forms the basis of our semiautomatic edge detection algorithm. Empirical evaluations and the resulting recommendations follow. In the context of the teleteaching project Virtual University of the Upper Rhine Valley (VIROR), many lectures were transmitted between remote locations. We thus encountered the problem of scalability of a video stream for different access bandwidths in the Internet. A substantial contribution of this dissertation is the introduction of the wavelet transform into hierarchical video coding and the recommendation of parameter settings based on empirical surveys. Furthermore, a prototype implementation proves the principal feasibility of a wavelet-based, nearly arbitrarily scalable application. Mathematical transformations constitute a commonly underestimated problem for students in their first semesters of study. Motivated by the VIROR project, we spent a considerable amount of time and effort on the exploration of approaches to enhance mathematical topics with multimedia; both the technical design and the didactic integration into the curriculum are discussed. In a large field trial on "traditional teaching versus multimedia-enhanced teaching", the objective knowledge gained by the students was measured. This allows us to objectively rate positive the efficiency of our teaching modules

A Wavelet Transform Applet for Interactive Learning

In recent years, new forms and techniques of teaching have appeared, based on the Internet and on multimedia applications. In the teleteaching Project Virtual University of the Upper Rhine Valley (VIROR), multimedia simulations and animations complement traditional teaching material. Lecturers use Java applets in their courses to explain complex structures. These are then stored in a multimedia database to enable asynchronous learning. The wavelet transform has become the most interesting new algorithm for still image compression. Yet, there are many parameters within a wavelet analysis and synthesis: choice of the wavelet filter bank, decomposition strategy, image boundary policy, quantization threshold, etc. We consider the wavelet transform to be a typical example of a complex, hard-to-understand algorithm that needs illustration by interactive multimedia. In this article, we present the didactic background and the implementation of a sample applet on the discrete wavelet transform, as taught in our multimedia course

Decomposition Strategies for Wavelet-Based Image Coding

The wavelet transform has become the most interesting new algorithm for still image compression. Yet there are many parameters within a wavelet analysis and synthesis which govern the quality of a decoded image. In this paper, we discuss different decomposition strategies of a two-dimensional signal and their implications for the decoded image: a pool of gray-scale images has been wavelet-transformed with different settings of the wavelet filter bank, quantization threshold and decomposition method. Contrary to the new standard JPEG-2000, where non-standard decomposition is implemented, our investigation proposes standard decomposition for low-bitrate coding