Teleteaching over Low-Bandwidth Network Channels

Teleteaching has become an important application of the Internet and the MBone. Unfortunately the costs for the hardware, necessary to participate in remote lectures, are still prohibitively high and the degree of distributiveness of the implemented scenarios is very low. In the Interactive Home Learning project we plan to provide methods to participate in a Teleteaching lecture live from a PC at horne via a low-bandwidth connection (e.g. ISDN). This paper summarises technical aspects of this learning scenario and presents our approach, the fully Java-based Reflection and Scaling Tool jrst, which meets the requirements of an application layer multicast routing demon with a highly restrictive broadcasting policy and a dynamic tunnelling mechanism

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

Efficient Video Transport over Lossy Networks

Nowadays, packet video is an important application of the Internet. Unfortunately the capacity of the Internet is still very heterogeneous because it connects high bandwidth ATM networks as well as low bandwidth ISDN dial in lines. The MPEG-2 and MPEG-4 video compression standards provide efficient video encoding for high and low bandwidth media streams. In particular they include two paradigms which make those standards suitable for the transmission of video via heterogeneous networks. Both support layered video streams and MPEG-4 additionally allows the independent coding of video objects. In this paper we discuss those two paradigms, give an overview of the MPEG video compression standards and describe transport protocols for Real Time Media transport over lossy networks. Furthermore, we propose a real-time segmentation approach for extracting video objects in teleteaching scenarios

On the Detection and Recognition of Television Commercials

TV commercials are interesting in many respects: advertisers and psychologists are interested in their influence on human purchasing habits, while parents might be interested in shielding their children from their influence. In this paper, two methods for detecting and extracting commercials in digital videos are described. The first method is based on statistics of measurable features and enables the detection of commercial blocks within TV broadcasts. The second method performs detection and recognition of known commercials with high accuracy. Finally, we show how both approaches can be combined into a self-learning system. Our experimental results underline the practicality of the methods

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

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

A General Framework and Communication Protocol for the Real-Time Transmission of Interactive Media

In this paper we present a general framework for the real-time transmission ofinteractive media, i.e. media involving user interaction. Examples of interactive media are shared whiteboards, Java animations and VRML worlds. By identifying and supporting the common aspects of this media class the framework allows the development of generic services for network sessions involving the transmission of interactive media. Examples are mechanisms for late join and session recording. The proposed framework is based on the Real-Time Transport Protocol (RTP) which is widely used in the Internet for the real-time transmission of audio and video. Using the experience gained through the framework for audio and video, our work consists of three important parts: the definition of a protocol profile, the instantiation of this profile for specific media, and the development of generic services. The profile captures those aspects that are common to the class of interactive media. A single medium must instantiate this profile by providing media-specific information in the form of a payload type definition. Based on the profile, generic services can be developed for all interactive media. In this paper we focus on the description of the profile for the real-time transmission of interactive media. We then present the main ideas behind a generic recording service. Finally we show how multi-user VRML and distributed interactive Java animations can instantiate the profile

Transmitting MPEG-4 Video Streams over the Internet : Problems and Solutions

In this work we discuss the transmission of MPEG-4 video streams over lossy packet networks like the Internet. Due to the efficient compression achieved by the MPEG-4 standard, parts of the bitstream show high inter-dependencies. Consequently, without any precautions packet loss within the transmission of a video session severely affects the video quality. Based on the error resilience tools already provided by the MPEG-4 video coding standard, we define an RTP payload format for MPEG-4 video streams and appropriate fragmentation rules. Furthermore, we present experimental results to evaluate the overall robustness of the approach

New Tools for Synchronous and Asynchronous Teaching and Learning in the Internet

In this paper we describe the new tools for synchronous and asynchronous learning developed within the context of the TeleTeaching Projects at the University of Mannheim. With our tools, students are enabled to follow lectures not only in the lecture halls of the connected universities but also at home. The innovative processing of course material allows the production of educational documents that consider the requirements of synchronous and asynchronous learning modes out of a single primary document. Course material is provided within a Web-based training unit designed specifically to support asynchronous student learning