Publications of Wolfgang Effelsberg

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Artikel

  • Rainer Lienhart und Wolfgang Effelsberg. 2000 Automatic Text Segmentation and Text Recognition for Video Indexing Multimedia Systems, 8, 6, 69-81
    Efficient indexing and retrieval of digital video is an important function of video databases. One powerful index for retrieval is the text appearing in them. It enables content-based browsing. We present our methods for automatic segmentation of text in digital videos. The output is directly passed to a standard OCR software package in order to translate the segmented text into ASCII. The algorithms we propose make use of typical characteristics of text in videos in order to enable and enhance segmentation performance. Especially the inter-frame dependencies of the characters provide new possibilities for their refinement. Then, a straightforward indexing and retrieval scheme is introduced. It is used in the experiments to demonstrate that the proposed text segmentation algorithms together with existing text recognition algorithms are suitable for indexing and retrieval of relevant video sequences in and from a video database. Our experimental results are very encouraging and suggest that these algorithms can be used in video retrieval applications as well as to recognize higher semantics in videos.
  • Rainer Lienhart, Wolfgang Effelsberg und Ramesh Jain. 2000 VisualGREP: A Systematic Method to Compare and Retrieve Video Sequences Multimedia Tools and Applications, 10, 2, 47-72
    In this paper, we consider the problem of similarity between video sequences. Three basic questions are raised and (partially) answered. Firstly, at what temporal duration can video sequences be compared? The frame, shot, scene and video levels are identified. Secondly, given some image or video feature, what are the requirements on its distance measure and how can it be easily transformed into the visual similarity desired by the inquirer? Thirdly, how can video sequences be compared at different levels? A general approach based on either a set or sequence representa-tion with variable degrees of aggregation is proposed and applied recursively over the different levels of temporal res-olution. It allows the inquirer to fully control the importance of temporal ordering and duration. The general approach is illustrated by introducing and discussing some of the many possible image and video features. Promising experimental results are presented.
  • Claudia Schremmer, Volker Hilt und Wolfgang Effelsberg. 2000 Erfahrungen mit synchronen und asynchronen Lernszenarien an der Universität Mannheim Praxis der Informationsverarbeitung und Kommunikation : PIK, 23, 2, 121-128
    An der Universität Mannheim werden seit 1996 TeleTeaching-Projekte durchgeführt. Der Schwerpunkt liegt dabei in synchronen Lernszenarien, worunter wir eine zeitgleiche (Internet-) Übertragung einer Veranstaltung an verschiedene Orte verstehen. Die Audio- und Videoströme des Dozenten werden zugleich aufgezeichnet und als Bestandteil eines Computer-Based-Trainings zeitunabhängig für asynchrone Lernszenarien zur Verfügung gestellt. Die implementierten synchronen und asynchronen Lernszenarien werden seit 1998 im Verbundprojekt VIROR der ober-rheinischen Universitäten Freiburg, Heidelberg, Karlsruhe und Mannheim eingesetzt. Dieser Artikel beschreibt verschiedene Lernszenarien bei TeleVeranstaltungen, ihre Besonderheiten und spezifischen Anforderungen. Die zugrunde liegende Technologie wird kurz vorgestellt, einige selbst entwickelte Software Werkzeuge beschrieben und weitere, bislang nicht realisierte Anforderungen an die Technik formuliert. Das Hauptaugenmerk aber legen wir auf Erfahrungen, die wir in den nunmehr vier Jahren aktiven TeleTeachings gewonnen haben.

Konferenz Beitrag

  • Robert Denda, Albert Banchs und Wolfgang Effelsberg. Springer, 2000 The Fairness Challenge in Computer Networks Lecture Notes in Computer Science. Berlin [u.a.]
  • Thomas Haenselmann, Claudia Schremmer und Wolfgang Effelsberg. IASTED/Acta Press, 2000 Wavelet-based Semi-automatic Segmentation of Image Objects . Anaheim, Calif. [u.a.]We present a wavelet-based algorithm to cut an object out of an image in a semi-automatic manner. The user of the algorithm selects a piece of a boundary that separates an object from the background. In contrast to other well-known segmentation algorithms, this sample boundary does not have to be a sharp edge, but might also be a smooth transition between two shades or a texture. Based on a multi-scale wavelet analysis of the sample area our algorithm seeks a path around the object by analyzing characteristic frequencies.
  • Volker Hilt, Werner Geyer und Wolfgang Effelsberg. SPIE, 2000 A New Paradigm for the Recording of Shared Whiteboard Streams Proceedings of SPIE. Bellingham, Wash.The number of video conferences conducted over the Internet has constantly increased during the last years. The need to archive the multimedia data streams of the conferences became apparent, and a number of tools accomplishing this task for audio and video streams were developed. In many video conferencing scenarios, shared whiteboards are used in addition to audio and video to transmit slides or to sketch ideas. However, none of the existing recording tools provides an efficient recording service for data streams of these tools. In this paper we present a new approach to the recording and playback of shared whiteboard media streams. We discuss generic design issues of a shared whiteboard recorder, and we present a novel algorithm that enables efficient random access to the recorded streams. We describe an implementation of our algorithms for the media streams of our digital lecture board (dlb).
  • Rüdiger Weis, Wolfgang Effelsberg und Stefan Lucks. Kluwer Academic Publ., 2000 Combining Authentication and and Light-Weight Payment in Active Networks IFIP Advances in Information and Communication Technology. Boston, Mass. [u.a.]
  • Rüdiger Weis, Wolfgang Effelsberg und Stefan Lucks. IEEE Service Center, 2000 Remotely Keyed Encryption with Java Cards : A Secure and Efficient Method to Encrypt Multimedia Streams . Piscataway, NJ
  • Rüdiger Weis, Jürgen Vogel, Wolfgang Effelsberg, Werner Geyer und Stefan Lucks. Springer, 2000 How to Make a Digital Whiteboard Secure: Using JAVA-Cards for Multimedia Applications Lecture Notes in Computer Science. Berlin [u.a.]In this paper we propose a light-weight, provable secure smart card integration for the OpenPGP secure message format. The basic idea is that the secret keys are stored on a smart card and never leave it. We have integrated this new security approach into an enhanced whiteboard, the digital lecture board (dlb). Existing whiteboards neglect security mechanisms almost completely, even though these mechanisms are extremely important to allow confidential private sessions and billing. The primary application field ouf our concept are small and closed groups, whereas the smart card serves to testify group membership. Our first implementation supports the JAVA i-Button which provides an additional hardware security.

Forschungs Papier

  • Martin Mauve, Volker Hilt, Christoph Kuhmünch, Jürgen Vogel, Werner Geyer und Wolfgang Effelsberg. Internet Society (ISOC), Internet-Drafts / Internet Engineering Task Force (IETF). 2000 RTP/I : an application level real-time protocol for distributed interactive media Reston, VA, .
    This document specifies RTP/I, an application level real-time protocol for distributed interactive media. Typical examples of distributed interactive media are shared whiteboards, networked computer games and distributed virtual environments. RTP/I defines a standardized framing for the transmission of data and provides mechanisms that are universally needed for this media class. Thereby RTP/I enables the development of reusable functionality and generic services that can be employed for multiple distributed interactive media. Examples for this kind of functionality are the ability to record sessions, to support late coming participants, and to provide security services. RTP/I is a protocol that follows the ideas of application level framing and integrated layer processing. It has been designed to be independent of the underlying network and transport layers. To a large extend RTP/I has been inspired by the real-time transport protocol (RTP), which is used for continuous non-interactive media. This document is intended to stimulate the discussion on how to transport distributed interactive media over the Internet. There exists an RTP/I mailing list. Instructions on how to subscribe to this list can be found at the RTP/I homepage (http://www.informatik.uni-mannheim.de/informatik/pi4/projects/ RTPI/index.html). Feedback on this document should be addressed to the RTP/I mailing list or directly to the authors.
  • Claudia Schremmer, Christoph Kuhmünch und Wolfgang Effelsberg. , Technical Reports. 2000 Layered Wavelet Coding for Video Mannheim, . 00-019
    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.
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