Conferences

Stephan Kopf, Mariia Zrianina, Benjamin Guthier, Lydia Weiland, Philipp Schaber, Simone Paolo Ponzetto und Wolfgang Effelsberg. CSREA Press, 2017 Enhancing bag of visual words with color information for iconic image classification . Athens, GA
Philip Mildner, Oliver Beck, Marcel Reinsch und Wolfgang Effelsberg. Academic Conferences and Publishing International Limited ; Curran, 2016 The influence of learning and gaming coherence on the effectiveness of serious games . Reading ; Red Hook, NYWhen creating digital game-based applications in educational contexts, a key aspect is how to combine the game and the learning part into a serious game that is both fun and effective. Such games can coarsely be categorized into games where learning and game parts are tightly linked together, and games that feature an exchangeable learning content. The former type gives game developers a high degree of freedom for integrating the learning content in a meaningful way. The latter type, on the other hand, allows non-expert game creators, such as teachers, to create customized games by using easy-to-use authoring components. In this work we examine both categories of games concerning their potential effectiveness and accessibility. We use two games: one that combines a generic game scenario with exchangeable quiz questions, and a second one with specialized content for teaching historic knowledge. Two comparative studies with a total of over 60 participants have been conducted with both games. The first study focuses on the effects of a game-based approach in comparison to one without game elements. The second study compares a generic game environment to one where game and learning content matches. Results show that the second game variant is able to produce better results in terms of fun and learning effectiveness. However, the generic variant still is able to produce good results with the benefit of not having to invest an additional development effort. These considerations are further elaborated to give practical advice for the creators of learning games.
Daniel Schön, Melanie Klinger, Stephan Kopf und Wolfgang Effelsberg. SCITEPRESS, 2016 Customized teaching scenarios for smartphones in university lecture settings: experiences with several teaching scenarios using the MobileQuiz2 . Setubal, PortugalMany teachers use Audience Response Systems (ARS) in lectures to re-activate their listeners and to get an insight in students’ knowledge of the current lecture contents. Plenty of such applications have been developed in recent years, they provide a high variety of different teaching scenarios with the use of the students’ smartphones, including quizzes, lecture feedback and dynamic message boards. We developed a novel application based on an abstract model to enable this variety of customizable teaching scenarios within one application. After presenting the application to the first charge of lecturers, the responses were quite good, and several new teaching scenarios were created and used. This paper presents first experiences when using a variety of customizable teaching scenarios, the special opportunities and challenges as well as the opinions of lecturers and students, which we collected with a survey at the end of the semester.
Daniel Schön, Melanie Klinger, Stephan Kopf, Thilo Weigold und Wolfgang Effelsberg. Springer, 2016 Customizable learning scenarios for students’ mobile devices in large university lectures : a next generation audience response system Communications in Computer and Information Science. Cham
Matthias Wichtlhuber, Gregor Wicklein, Stefan Wilk, Wolfgang Effelsberg und David Hausheer. ACM Digital Library, 2016 RT-VQM : real-time video quality assessment for adaptive video streaming using GPUs . New York, NY
Stefan Wilk und Wolfgang Effelsberg. ACM Digital Library, 2016 The content-aware video adaptation service for mobile devices . New York, NY
Stefan Wilk, Dominik Schreiber, Denny Stohr und Wolfgang Effelsberg. IEEE, 2016 On the effectiveness of video prefetching relying on recommender systems for mobile devices . Piscataway, NJ
Stefan Wilk, Roger Zimmermann und Wolfgang Effelsberg. ACM, 2016 Leveraging transitions for the upload of user-generated mobile video . New York, NY
Okan Aydingül, Philip Mildner, Stephan Kopf und Wolfgang Effelsberg. Association for the Advancement of Computing in Education (AACE), 2015 EOOC - Easy Open Online Courses : a platform to create and run open online courses . Waynesville, NC
Stephan Kopf, Daniel Schön, Benjamin Guthier, Roman Rietsche und Wolfgang Effelsberg. Association for the Advancement of Computing in Education (AACE), 2015 A real-time feedback system for presentation skills . Waynesville, NC
Philip Mildner, Nicolas Stamer und Wolfgang Effelsberg. Springer International Publishing, 2015 From game characteristics to effective learning games : evaluation of a component-based quiz game Lecture Notes in Computer Science. Cham [u.a.]When developing learning games, emphasis should not only be put on a good integration of the learning content, but also on an engaging game design, in order to create learning tools that both train and motivate. In this paper, we examine the influence of specific game elements to both factors. Therefore, we first analyze models for the characterization of game elements. We then apply an adapted model to the design of a component-based learning game based on a quiz. Various game elements can be added to the game dynamically. This includes, among others, different forms of presentation, challenge, competition and constraints. Using this application we performed a user study to evaluate which game elements are most effective in delivering knowledge as well as in fostering motivation. Results show that a combination of game elements is suited best for influencing both factors positively.
Simone Paolo Ponzetto, Hartmut Wessler, Lydia Weiland, Stephan Kopf, Wolfgang Effelsberg und Heiner Stuckenschmidt. Peter Lang Edition, 2015 Automatic classification of iconic images based on a multimodal model : an interdisciplinary project Sprache - Medien - Innovationen. Frankfurt am Main ; Bern; Wien
Philipp Schaber, Sally Dong, Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. ACM, 2015 Modeling temporal effects in re-captured video . New York, NYThe re-capturing of video content poses significant challenges to algorithms in the fields of video forensics, watermarking, and near-duplicate detection. Using a camera to record a video from a display introduces a variety of artifacts, such as geometric distortions, luminance transformations, and temporal aliasing. A deep understanding of the causes and effects of such phenomena is required for their simulation, and for making the affected algorithms more robust. In this paper, we provide a detailed model of the temporal effects in re-captured video. Such effects typically result in the re-captured frames being a blend of the original video's source frames, where the specific blend ratios are difficult to predict. Our proposed parametric model captures the temporal artifacts introduced by interactions between the video renderer, display device, and camera. The validity of our model is demonstrated through experiments with real re-captured videos containing specially marked frames.
Matthias Schulz, Denny Stohr, Stefan Wilk, Benedikt Rudolph, Wolfgang Effelsberg und Matthias Hollick. IEEE, 2015 APP and PHY in harmony: a framework enabling flexible physical layer processing to address application requirements . Piscataway, NJ
Daniel Schön, Melanie Klinger, Stephan Kopf und Wolfgang Effelsberg. SCITEPRESS, Science and Technology Publications, 2015 A model for customized in-class learning scenarios - an approach to enhance audience response systems with customized logic and interactivity . [Setúbal]
Daniel Schön, Licheng Yang, Melanie Klinger, Stephan Kopf und Wolfgang Effelsberg. Assoc. for the Advancement of Computing in Education , Universität Mannheim 2015 On the effects of different parameters in classroom interactivity systems on students . Waynesville, NCClassroom Response Systems (CRS) are often used in higher education lectures. They help to activate students and to get a deeper insight on the students' knowledge base and on their opinion on currently discussed topics. Many different systems were created, offering a similar amount of functionality. We thus investigate what the important parameters of such systems are, and how they influence the students’ behavior. Therefore, we consider classic response systems as well as systems with a higher amount of interactivity. In a first step, we have defined eight possible parameters, like the usage of pictures or a progress bar. We did a field study in thirty six lectures comparing the impact of the different parameters. As expected, the overall satisfaction with CRS is very high but we have obtained surprising results with particular parameters. We present the most interesting results and give a suggestion on which parameters are useful for an investigation in greater depth.
Denny Stohr, Tao Li, Stefan Wilk, Silvia Santini und Wolfgang Effelsberg. EEE Operations Center, 2015 An analysis of the YouNow live streaming platform . Piscataway, NJ
Denny Stohr, Matthias Schulz, Matthias Hollick und Wolfgang Effelsberg. IEEE, 2015 APP and PHY in harmony: demonstrating scalable video streaming supported by flexible physical layer control . Piscataway, NJ
Stefan Wilk, Stephan Kopf und Wolfgang Effelsberg. ACM, 2015 Video composition by the crowd : a system to compose user-generated videos in near real-time . New York, NY
Stefan Wilk, Julius Rückert, Denny Stohr, Björn Richerzhagen und Wolfgang Effelsberg. IEEE, 2015 Efficient video streaming through seamless transitions between unicast and broadcast . Piscataway, NJ
Stefan Wilk, Julius Rückert, Timo Thräm, Christian Koch, Wolfgang Effelsberg und David Hausheer. IEEE, 2015 The potential of social-aware multimedia prefetching on mobile devices . Piscataway, NJ
Stefan Wilk, Sophie Schönherr, Denny Stohr und Wolfgang Effelsberg. ACM, 2015 EnvDASH: an environment-aware dynamic adaptive streaming over HTTP systems . New York, NY
Stefan Wilk, Denny Stohr und Wolfgang Effelsberg. ACM, 2015 VAS: a video adaptation service to support mobile video . New York, NY
Stefan Wilk, Dimitri Wulffert und Wolfgang Effelsberg. IEEE, 2015 On influencing mobile live video broadcasting users . Piscataway, NJ
Johannes Kiess, Daniel Gritzner, Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. ACM, 2014 GPU Video Retargeting with Parallelized SeamCrop . New York, NY
Stephan Kopf, Benjamin Guthier, Christopher Hipp, Johannes Kiess und Wolfgang Effelsberg. IEEE, 2014 Warping-based video retargeting for stereoscopic video . Piscataway, NJ
Philip Mildner, Christopher Campbell und Wolfgang Effelsberg. Springer Internat., 2014 Word Domination: Bringing Together Fun and Education in an Authoring-Based 3D Shooter Game Lecture Notes in Computer Science. Cham [u.a.]In this paper, the multiplayer serious game Word Domination is presented. The key aspects of this project are to create one fixed game scenario with strong emphasis on motivational aspects and to combine this with a variable learning content. Therefore, a web based authoring tool has been created that allows for the integration of arbitrary quizzes into the game. This frees teachers from hassling with game design details. At the same time, it offers players the same level of engaging gameplay throughout different learning scenarios by making use of the popularity of 3D shooter games. Apart from the beneficial aspects of in game learning, the game also offers rankings and statistics, which might serve as a motivational aspect on the one hand, and as an evaluation tool for instructors on the other hand. In addition to a description of game mechanisms and the technical background of the game, this paper will present suggestions for application scenarios and further development possibilities. Some player impressions and reactions were gathered in a study at the University of Mannheim and at the Darmstadt GameDays 2013 exhibition, during which the game was played by a broad audience.
Philip Mildner, Benjamin John, Alexander Moch und Wolfgang Effelsberg. IEEE, 2014 Creation of Custom-made Serious Games with User-generated Learning Content . Piscataway, NJIntegrating user-generated content into digital games helps to increase re-usability and to decrease development effort. In terms of learning games, the content creation can be extended to the learning parts of the game as well, e.g., allowing teachers to create custom games for their students. In this work, we propose a method of how to create learning games with arbitrary user-generated learning content. This includes not only different topics of learning content, but also different types of knowledge acquisition. To do this we combine a static game scenario with lightweight HTML5-based mini games. Learning content can be conveniently added through a web-based authoring tool that does not require any programming or game design knowledge. In addition to that, we created a game prototype based on the Unity3D engine that uses a tower defence game setting to integrate the learning content. These mini games are retrieved from the backend service at runtime. The implemented solution already allows for the integration of arbitrary content and can easily extended without altering the game client.
Björn Richerzhagen, Stefan Wilk, Julius Rückert, Denny Stohr und Wolfgang Effelsberg. ACM, 2014 Transitions in live video streaming services . New York, NY
Philipp Schaber, Stephan Kopf, Christoph Wesch und Wolfgang Effelsberg. ACM, 2014 CamMark : a camcorder copy simulation as watermarking benchmark for digital video . New York, NYIn 1998, Petitcolas et al. proposed StirMark as a benchmark for image watermarking schemes. The main idea was to introduce a re-sampling process that mimics the analog process of printing and scanning a watermarked image. For digital video, the corresponding concept is a camcorder copy, where a video displayed on a screen is (digitally) recorded using a video camera. As most commercial video streaming systems (VOD, IPTV) and offline distribution (Blu-ray, HDDs for cinemas) are strongly protected by means of DRM, filming a display is actually a relevant use case and a requirement for robust video watermarking systems to survive. We therefore present a tool to simulate content re-acquisition with a camcorder. Our goal is to support watermark development by enabling automated test cases for such camcorder copy attacks, as well as to provide a benchmark for robust video watermarking. Manually creating camcorder copies is a cumbersome process, and even more problematic, it is hardly reproducible with the same setup. By re-sampling each video frame, we simulate the typical artifacts of a camcorder copy: geometric modifications (aspect ratio changes, cropping, perspective and lens distortion), temporal modifications (unsynchronized frame rates and the resulting frame blending), sub-sampling (rescaling, filtering, Bayer color array filter), and histogram changes (AGC, AWB). We also support simulating camera movement (e.g., a hand-held camera) and background insertion.
Daniel Schön, Philip Mildner, Stephan Kopf und Wolfgang Effelsberg. Gesellschaft für Informatik, 2014 SMASH: Ein generisches System für interaktive Szenarien in der Vorlesung GI-Edition : Lecture Notes in Informatics. Proceedings. Freiburg, Br.
Daniel Schön, Steffen Sikora, Stephan Kopf und Wolfgang Effelsberg. RWTH, 2014 GLA: A Generic Analytics Tool for e-Learning CEUR Workshop Proceedings. AachenSeveral software applications are used at the University of Mannheim for learning and teaching purposes. The majority of them, like lecture feedback, quizzes, forums, and wikis, are hosted within our learning management system ILIAS. In addition, we run several prototypes of serious games and mobile feedback systems. While the data generated by students and teachers is mainly used for current courses, it could be further used for Learning Analytics if it was stored in an adequate format. Considering the variable and fast-moving nature of our learning applications, we invented a concept for a generic database structure, that can handle analyses on a variety of original tools. This paper presents the prototype application GLA (Generic Learning Analytics), which tries to provide a step in the right direction. Data from wikis, forums, quizzes and serious games transformed into one homogeneous format that can be used to do comparable analyzes. Beside comparing several semesters and courses of one application, we can also match related data sets e. g. user behavior between a wiki and a file upload.
Denny Stohr, Stefan Wilk und Wolfgang Effelsberg. ACM, 2014 Monitoring of User Generated Video Broadcasting Services . New York, NY
Lydia Weiland, Wolfgang Effelsberg und Simone Paolo Ponzetto. Asooc. for Computational Linguistics, 2014 Weakly supervised construction of a repository of iconic images . Stroudsburg, Pa.We present a first attempt at semi-automatically harvesting a dataset of iconic images, namely images that depict objects or scenes, which arouse associations to abstract topics. Our method starts with representative topic-evoking images from Wikipedia, which are labeled with relevant concepts and entities found in their associated captions. These are used to query an online image repository (i.e., Flickr), in order to further acquire additional examples of topic-specific iconic relations. To this end, we leverage a combination of visual similarity measures, image clustering and matching algorithms to acquire clusters of iconic images that are topically connected to the original seed images, while also allowing for various degrees of diversity. Our first results are promising in that they indicate the feasibility of the task and that we are able to build a first version of our resource with minimal supervision.
Stefan Wilk und Wolfgang Effelsberg. ACM, 2014 Mobile video broadcasting services - combining video composition and network efficient transmission . New York, NY
Stefan Wilk und Wolfgang Effelsberg. ACM, 2014 Systematic assessment of the video recording position for user-generated event videos . New York, NY
Stefan Wilk und Wolfgang Effelsberg. IEEE, 2014 The influence of camera shakes, harmful occlusions and camera misalignment on the perceived quality in user-generated video . Piscataway, NJ [u.a.]
Torben Dittrich, Stephan Kopf, Philipp Schaber, Benjamin Guthier und Wolfgang Effelsberg. ACM, 2013 Saliency Detection for Stereoscopic Video . New York, NY
Benjamin Guthier, Kalun Ho, Stephan Kopf und Wolfgang Effelsberg. ACM, 2013 Determining Exposure Values from HDR Histograms for Smartphone Photography . [New York, NY]
Benjamin Guthier, Johannes Kiess, Stephan Kopf und Wolfgang Effelsberg. IEEE, 2013 Seam Carving for STereoscopic Video . Piscataway, NJ
Melanie Klinger, Daniel Schön und Wolfgang Effelsberg. Ges. für Informatik, 2013 Implementierung und Evaluation eines QR-Code gestützten Umfrage-Tools für Präsenzveranstaltungen GI-Edition : Lecture Notes in Informatics. Proceedings. Bonn
Philip Mildner, Frederik Claus, Stephan Kopf und Wolfgang Effelsberg. ACM, 2013 Navigating Videos by Location . New York, NY
Philipp Schaber und Wolfgang Effelsberg. IEEE, 2013 A Component System for Spontaneous Virtual Networks . Piscataway, NJ
Daniel Schön, Melanie Klinger, Stephan Kopf und Wolfgang Effelsberg. AACE, 2013 HomeQuiz: Blending Paper Sheets with Mobile Self-Assessment Tests . Chesapeake, Va.
Stefan Wilk und Wolfgang Effelsberg. ACM, 2013 Crowdsourced Evaluation of the Perceived Viewing Quality in User-generated Video . New York, NY
Stefan Wilk, Stephan Kopf, S Schulz und Wolfgang Effelsberg. AACE, 2013 Social Video: A Collaborative Video Annotation Environment to Support E-Learning . Chesapeake, Va.Our social video system allows users to enrich video by additional information like external websites, hypertext, images, other videos, or communication channels. Users are able to annotate whole videos, scenes, and objects in the video. We do not focus on a single user accessing the system but on multiple users watching the video and accessing the annotations others have created. Our web-based prototype differs from classical hypervideo systems because it allows annotation (authoring) and navigation in videos by focusing on collaboration and communication between the users. The prototype is integrated into the online social network Facebook and was evaluated with more than 300 users. The evaluation analyzes the usage of the system with a learning scenario in mind and indicates a learning success of users.
Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. ACM, 2012 A Real-Time System for Capturing HDR Videos . New York, NY
Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. IEEE, 2012 Optimal Shutter Speed Sequences for Real-time HDR Video . Piscataway, NJ
Benjamin Guthier, Stephan Kopf, Matthias Wichtlhuber und Wolfgang Effelsberg. IEEE, 2012 Parallel Algorithms for Histogram-based Image Registration . Piscataway, NJ
Johannes Kiess, Rodrigo Garcia, Stephan Kopf und Wolfgang Effelsberg. IEEE, 2012 Improved Image Retargeting by Distinguishing between Faces in Focus and out of Focus . Piscataway, NJ
Johannes Kiess, Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. ACM, 2012 Seam Crop: Changing the Size and Aspect Ratio of Videos . New York, NY
Johannes Kiess, Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. SPIE, 2012 SeamCrop for image retargeting Proceedings of SPIE. Bellingham, Wash.
Stephan Kopf, Stefan Wilk und Wolfgang Effelsberg. IEEE, 2012 Bringing Videos to Social Media . Piscataway, NJ
Sascha Schnaufer, Johannes Kiess, Hendrik Lemelson, Stephan Kopf, Sebastian Geiger und Wolfgang Effelsberg. IEEE, 2012 Proximity Detection and Message Exchange in WLANs . Piscataway, NJ
Daniel Schön, Stephan Kopf und Wolfgang Effelsberg. IEEE, 2012 A lightweight mobile quiz application with support for multimedia content . Piscataway, NJ
Daniel Schön, Stephan Kopf, Stephan Schulz und Wolfgang Effelsberg. Assoc. for the Advancement of Computing in Education, 2012 Integrating a Lightweight Mobile Quiz on Mobile Devices into the Existing University Infrastructure . Chesapeake, Va.
Daniel Schön, Hendrik Lemelson und Wolfgang Effelsberg. IEEE, 2012 Situation-aware scoice of the most accurate positioning system . Piscataway, NJ
Tonio Triebel, Max Lehn, Robert Rehner, Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. IEEE, 2012 Generation of Synthetic Workloads for Multiplayer Online Gaming Benchmarks . [Piscataway, NJ]
Stefan Wilk, Stephan Kopf und Wolfgang Effelsberg. IEEE, 2012 Robust tracking for interactive social video . Piscataway, NJ
Benjamin Guthier, Stephan Kopf, Marc Eble und Wolfgang Effelsberg. SPIE, 2011 Flicker Reduction in Tone Mapped High Dynamic Range Video Proceedings of SPIE. Bellingham, Wash.
Philip Mildner, Tonio Triebel, Stephan Kopf und Wolfgang Effelsberg. ICST, 2011 A scalable Peer-to-Peer-overlay for real-time massively multiplayer online games . Brussels
Ruzana Davoyan und Wolfgang Effelsberg. CSREA Press, 2010 Exploring the Impact of Transmission Initiator Determination on Retail and Wholesale Markets . Irvine, CA
Ruzana Davoyan und Wolfgang Effelsberg. Springer, 2010 Intercarrier Compensation between Providers of Different Layers: Advantages of Transmission Initiator Determination Lecture Notes in Computer Science. Berlin [u.a.]
Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. IEEE , 2010 Histogram-based Image Registration for Real-time High Dynamic Range Videos . Piscataway, NJ
Johannes Kiess, Stephan Kopf, Benjamin Guthier und Wolfgang Effelsberg. SPIE, 2010 Seam Carving with Improved Edge Preservation Proceedings of SPIE. Bellingham, Wash.
Max Lehn, Tonio Triebel, Christof Leng, Alejandro Buchmann und Wolfgang Effelsberg. IEEE Computer Soc., 2010 Performance Evaluation of Peer-to-Peer Gaming Overlays . Piscataway, NJ [u.a.]
Hendrik Lemelson, Sascha Schnaufer und Wolfgang Effelsberg. IEEE, 2010 Automatic Identification of Fingerprint Regions for Quick and Reliable Location Estimation . Piscataway, NJ [u.a.]
Philipp Schaber, Stephan Kopf, Fabian Bauer und Wolfgang Effelsberg. ACM Press, 2010 Robust Digital Watermarking in Videos Based on Geometric Transformations . New York, NY
Philipp Schaber, Stephan Kopf, Wolfgang Effelsberg und Niels Torwirth. ACM, 2010 Semi-automatic Registration of Videos for Improved Watermark Detection . New York, NY
Sascha Schnaufer, Thomas Haenselmann und Wolfgang Effelsberg. ACM, 2010 Demo Abstract: BSMX - Message Exchange Between Unassociated WLAN Devices . New York, NY
Sascha Schnaufer, Stephan Kopf und Wolfgang Effelsberg. ETH, 2010 BSMX - A Prototype Implementation for Distributed Aggregation of Sensor Data . Zürich
Sascha Schnaufer, Stephan Kopf, Hendrik Lemelson und Wolfgang Effelsberg. IEEE, 2010 Beacon-based Short Message Exchange in an Inner City Environment . Washington, DC [u.a.]
Tonio Triebel, Sascha Schnaufer, Benjamin Guthier, Hendrik Lemelson, Gregor Schiele und Wolfgang Effelsberg. IEEE, 2010 REWARD A Real World Achievement and Record Database . Piscataway, NJ [u.a.]
Ruzana Davoyan, Jörn Altmann und Wolfgang Effelsberg. Springer, 2009 A New Bilateral Arrangement between Interconnected Providers Lecture Notes in Computer Science. Berlin [u.a.]
Ruzana Davoyan, Jörn Altmann und Wolfgang Effelsberg. CSREA Press, 2009 Exploring the Effect of Traffic Differentiation on Interconnection Cost Sharing . Las Vegas, Nev.
Ruzana Davoyan, Jörn Altmann und Wolfgang Effelsberg. IEEE Computer Soc., 2009 Intercarrier Compensation in Unilateral and Bilateral Arrangements . Los Alamitos, Calif. [u.a.]
Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. SPIE, 2009 High-Resolution Inline Video-AOI for Printed Circuit Assemblies Proceedings of SPIE. Bellingham, Wash.
Stephan Kopf, Benjamin Guthier, Hendrik Lemelson und Wolfgang Effelsberg. SPIE, 2009 Adaptation of web pages and images for mobile applications Proceedings of SPIE. Bellingham, Wash.
Stephan Kopf, Johannes Kiess, Hendrik Lemelson und Wolfgang Effelsberg. ACM Press, 2009 FSCAV - Fast Seam Carving for Size Adaptation of Videos . New York, NY
Hendrik Lemelson, Stephan Kopf, Thomas King und Wolfgang Effelsberg. IEEE Computer Soc., 2009 Improvements for 802.11-based Location Fingerprinting Systems . Los Alamitos, Calif. [u.a.]
Tonio Triebel, Benjamin Guthier, Thomas Plotkowiak und Wolfgang Effelsberg. IEEE, 2009 Peer-to-peer voice communications for massively multiplayer online games . Piscataway, NJ
Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. IEEE Service Center, 2008 Capturing High Dynamic Range Images with Partial Re-exposures . Piscataway, NJ
Thomas King, Thomas Haenselmann und Wolfgang Effelsberg. IEEE Service Center, 2008 On-Demand Fingerprint Selection for 802.11-based Positioning Systems . Piscataway, NJ
Stephan Kopf, Thomas King, Philipp Bostan, Hendrik Lemelson, Sina Deibert und Wolfgang Effelsberg. ICST, 2008 Fundamental Services for Context-Sensitive Mobile Applications . Brussels
Fleming Lampi, Stephan Kopf und Wolfgang Effelsberg. ACM Press, 2008 Automatic Lecture Recording . New York, NY
Hendrik Lemelson, Thomas King und Wolfgang Effelsberg. ICST, 2008 A Study on User Acceptance of Error Visualization Techniques . Brussels
Hendrik Lemelson, Thomas King und Wolfgang Effelsberg. AMC, 2008 Pre-processing of Fingerprints to Improve the Positioning Accuracy of 802.11-based Positioning Systems . New York, NY
Sascha Schnaufer und Wolfgang Effelsberg. IEEE Service Center, 2008 Position-Based Unicast Routing for City Scenarios . Piscataway, NJ
Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. IEEE Computer Soc., 2007 Energy-Efficient Aggregation Forwarding for Wireless Sensor Networks . Piscataway, NJ
Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. IEEE Computer Soc., 2007 Energy-Efficient Data Dissemination for Wireless Sensor Networks . Los Alamitos, Calif. [u.a.]
Holger Füßler, Sascha Schnaufer, Matthias Transier und Wolfgang Effelsberg. IEEE, 2007 Vehicular Ad-Hoc Networks: From Vision to Reality and Back . Piscataway, NJ
Thomas Haenselmann, Thomas King, Marcel Busse, Wolfgang Effelsberg und Markus Fuchs. Springer, 2007 Embedded Script-Driven Home-Automation with Sensor Networks IFIP Advances in Information and Communication Technology. New York, NY [u.a.]
Thomas Haenselmann, Thomas King, Marcel Busse, Wolfgang Effelsberg und Markus Fuchs. Springer, 2007 Scriptable Sensor Network based Home-Automation Lecture Notes in Computer Science. Berlin [u.a.]
Thomas King, Thomas Butter, Matthias Brantner, Stephan Kopf, Thomas Haenselmann, Alexander Biskop, Andreas Färber und Wolfgang Effelsberg. IEEE Operations Center, 2007 Distribution of Fingerprints for 802.11-based Positioning Systems . Piscataway, NJ [u.a.]
Thomas King, Thomas Butter, Hendrik Lemelson, Thomas Haenselmann und Wolfgang Effelsberg. ACM Press, 2007 Loc{lib,trace,eva,ana}: Research Tools for 802.11-based Positioning Systems . New York, NY
Thomas King, Thomas Haenselmann und Wolfgang Effelsberg. Springer , 2007 Deployment, Calibration, and Measurement Factors for Position Errors in 802.11-based Indoor Positioning Systems . Berlin [u.a.]
Thomas King, Thomas Haenselmann, Stephan Kopf und Wolfgang Effelsberg. IEEE Computer Soc., 2007 Overhearing the Wireless Interface for 802.11-based Positioning Systems . Los Alamitos, Calif. [u.a.]
Stephan Kopf und Wolfgang Effelsberg. SPIE, 2007 Color Adaptation of Videos for Mobile Devices Proceedings of SPIE. Bellingham, Wash.
Stephan Kopf, Fleming Lampi, Thomas King, Malte Probst und Wolfgang Effelsberg. Ges. für Informatik, 2007 EDL-Editor: Eine Anwendung zur automatischen Aufbereitung von Vorlesungsvideos GI-Edition : Lecture Notes in Informatics. Proceedings. Bonn
Fleming Lampi, Stephan Kopf, Manuel Benz und Wolfgang Effelsberg. ACM, 2007 An Automatic Cameraman in a Lecture Recording System . New York, NY
Fleming Lampi, Stephan Kopf und Wolfgang Effelsberg. AACE , 2007 Automatic FSM-Based Video Directors for Lecture Recording . Chesapeake, Va.
Hendrik Lemelson, Thomas King, Stephan Kopf und Wolfgang Effelsberg. INSTICC Press, 2007 On the Use of Various Power Levels to Improve Wireless LAN-based Positioning : Using Multiple Power Levels With Fingerprinting Algorithms . [Setúbal]
Moritz Steiner, Wolfgang Effelsberg, Taoufik En-Najjary und Ernst W. Biersack. Univ., 2007 Load Reduction in the KAD Peer-to-Peer System . Vienna
Tonio Triebel, Benjamin Guthier und Wolfgang Effelsberg. ACM Press, 2007 Skype4Games ACM Conference Proceedings Series. New York, NY
Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. ACM, 2006 A Comparison of Lifetime-Efficient Forwarding Strategies for Wireless Sensor Networks . New York, NY
Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. IEEE Computer Soc., 2006 Energy-Efficient Forwarding Schemes for Wireless Sensor Networks . Los Alamitos, Calif. [u.a.]
Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. Springer, 2006 Poster Abstract: A Lifetime-Efficient Forwarding Strategy for Wireless Sensor Networks Lecture Notes in Computer Science. Berlin [u.a.]
Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. ACM Press, 2006 TECA: A Topology and Energy Control Algorithm for Wireless Sensor Networks . New York, NY
Thomas Haenselmann, Marcel Busse, Stephan Kopf, Thomas King und Wolfgang Effelsberg. Technische Univ., 2006 Multi-Camera Video Stitching . Eindhoven
Thomas King, Holger Füßler, Matthias Transier und Wolfgang Effelsberg. TUHH, 2006 Dead-Reckoning for Position-Based Forwarding on Highways . Hamburg
Thomas King, Stephan Kopf und Wolfgang Effelsberg. Verl. Dr. Hut, 2006 Positionserkennung von Studierenden in Hörsälen mit dem Chi-Quadrat-Anpassungstest . München
Thomas King, Stephan Kopf, Thomas Haenselmann, Christian Lubberger und Wolfgang Effelsberg. ACM, 2006 COMPASS: A Probabilistic Indoor Positioning System Based on 802.11 and Digital Compasses . New York, NY
Stephan Kopf, Thomas King, Fleming Lampi und Wolfgang Effelsberg. Ges. für Informatik, 2006 Automatische Kamerasteuerung in Interaktiven Vorlesungen GI-Edition : Lecture Notes in Informatics. Proceedings. Bonn
Stephan Kopf, Thomas King, Fleming Lampi und Wolfgang Effelsberg. ACM, 2006 Video Color Adaptation for Mobile Devices . New York, NY
Stephan Kopf, Fleming Lampi, Thomas King und Wolfgang Effelsberg. ACM, 2006 Automatic Scaling and Cropping of Videos for Devices with Limited Screen Resolution . New York, NY
Fleming Lampi, Stephan Kopf und Wolfgang Effelsberg. Ges. für Informatik, 2006 Mediale Aufbereitung von Lehrveranstaltungen und ihre automatische Veröffentlichung - Ein Erfahrungsbericht GI-Edition : Lecture Notes in Informatics. Proceedings. Bonn
Fleming Lampi, Nicolai Scheele und Wolfgang Effelsberg. AACE , 2006 Automatic Camera Control for Lecture Recordings . Norfolk, Va.
Sascha Schnaufer, Holger Füßler, Matthias Transier und Wolfgang Effelsberg. ACM Press, 2006 SLOPE: A System for rapid Deployment of VANET Communication Protocols [Poster] . New York, NY
Sascha Schnaufer, Holger Füßler, Matthias Transier und Wolfgang Effelsberg. TUHH, 2006 Vehicular Ad-Hoc Networks: Single-Hop Broadcast is not enough . Hamburg
Matthias Transier, Holger Füßler, Thomas Butter und Wolfgang Effelsberg. ACM , 2006 Contention-Based Multicast Forwarding . New York, NY
Till Aldinger, Stephan Kopf, Nicolai Scheele und Wolfgang Effelsberg. AACE, 2005 Participatory Simulation of a Stock Exchange . Norfolk, Va.
Giovanni Falcone, Nicolai Scheele, Wolfgang Effelsberg und Colin Atkinson. Ges. für Informatik, 2005 PartSim - Ein System zur Unterstützung interaktiver Simulationen in der Lehre GI-Edition : Lecture Notes in Informatics. Proceedings. Bonn
Thomas Haenselmann und Wolfgang Effelsberg. Ges. für Informatik, 2005 Forking Agents in Sensor Networks . Bonn
Thomas King, Stephan Kopf und Wolfgang Effelsberg. Fernuniv., Fachbereich Informatik , 2005 A Location System based on Sensor Fusion: Research Areas and Software Architecture Informatik-Berichte. Hagen
Stephan Kopf, Thomas Haenselmann und Wolfgang Effelsberg. IEEE Operations Center, 2005 Enhancing curvature scale space features for robust shape classification . Piscataway, NJThe curvature scale space (CSS) technique, which is also part of the MPEG-7 standard, is a robust method to describe complex shapes. The central idea is to analyze the curvature of a shape and derive features from inflection points. A major drawback of the CSS method is its poor representation of convex segments: Convex objects cannot be represented at all due to missing inflection points. We have extended the CSS approach to generate feature points for concave and convex segments of a shape. This generic approach is applicable to arbitrary objects. In the experimental results, we evaluate as a comprehensive example the automatic recognition of characters in images and videos.
Stephan Kopf, Thomas King und Wolfgang Effelsberg. Fernuniv., Fachbereich Informatik, 2005 Improvement of Accuracy for GPS Informatik-Berichte. Hagen
Stephan Kopf, Nicolai Scheele, Lilli Winschel und Wolfgang Effelsberg. WIT Press, 2005 Improving Activity and Motivation of Students with Innovative Teaching and Learning Technologies . Southampton [u.a.]
Nicolai Scheele, Anja Wessels, Wolfgang Effelsberg, Manfred Hofer und Stefan Fries. Erlbaum, 2005 Experiences with Interactive Lectures : Considerations from the Perspective of Educational Psychologie and Computer Science . Mahwah, NJ [u.a.]
Dirk Farin, Susanne Krabbe, Wolfgang Effelsberg und Peter H. N. de With. SPIE, 2004 Robust Camera Calibration for Sport Videos using Court Models Proceedings of SPIE. Bellingham, WAWe propose an automatic camera calibration algorithm for court sports. The obtained camera calibration parameters are required for applications that need to convert positions in the video frame to real-world coordinates or vice versa. Our algorithm uses a model of the arrangement of court lines for calibration. Since the court model can be specified by the user, the algorithm can be applied to a variety of different sports. The algorithm starts with a model initialization step which locates the court in the image without any user assistance or a-priori knowledge about the most probable position. Image pixels are classified as court line pixels if they pass several tests, including color and local texture constraints. A Hough transform is applied to extract line elements, forming a set of court line candidates. The subsequent combinatorial search establishes correspondences between lines in the input image and lines from the court model. For the succeeding input frames, an abbreviated calibration algorithm is used that predicts the camera parameters for the new image and optimizes them using a gradient-descent algorithm. We have conducted experiments on a variety of sport videos (tennis, volleyball, and goal area sequences of soccer games). Video scenes with considerable difficulties were selected to test the robustness of the algorithm. Results show that the algorithm is very robust to occlusions, partial court views, bad lighting conditions, or shadows.
Dirk Farin, Peter H. N. de With und Wolfgang Effelsberg. SPIE, 2004 Minimizing MPEG-4 Sprite Coding-Cost Using Multi-Sprites . San Jose, Calif.Object-oriented coding in the MPEG-4 standard enables the separate processing of foreground objects and the scene background (sprite). Since the background sprite only has to be sent once, transmission bandwidth can be saved. This paper shows that the concept of merging several views of a non-changing scene background into a single background sprite is usually not the most efficient way to transmit the background image. We have found that the counter-intuitive approach of splitting the background into several independent parts can reduce the overall amount of data. For this reason, we propose an algorithm that provides an optimal partitioning of a video sequence into independent background sprites (a multi-sprite), resulting in a significant reduction of the involved coding cost. Additionally, our algorithm results in background sprites of better quality by ensuring that the sprite resolution has at least the final display resolution throughout the sequence. Even though our sprite generation algorithm creates multiple sprites instead of a single background sprite, it is fully compatible with the existing MPEG-4 standard. The algorithm has been evaluated with several test-sequences, including the well-known Table-tennis and Stefan sequences. We were able to reduce the total coding cost by factors of about 2.7 or even higher.
Holger Füßler, Hannes Hartenstein, Jörg Widmer und Wolfgang Effelsberg. TUHH, 2004 Contention-Based Forwarding for Street Scenarios . Hamburg
Stephan Kopf, Thomas Haenselmann, Dirk Farin und Wolfgang Effelsberg. SPIE, 2004 Automatic Generation of Summaries for the Web Proceedings of SPIE. Bellingham, Wash.Many TV broadcasters and film archives are planning to make their collections available on the Web. However, a major problem with large film archives is the fact that it is difficult to search the content visually. A video summary is a sequence of video clips extracted from a longer video. Much shorter than the original, the summary preserves its essential messages. Hence, video summaries may speed up the search significantly. Videos that have full horizontal and vertical resolution will usually not be accepted on the Web, since the bandwidth required to transfer the video is generally very high. If the resolution of a video is reduced in an intelligent way, its content can still be understood. We introduce a new algorithm that reduces the resolution while preserving as much of the semantics as possible. In the MoCA (movie content analysis) project at the University of Mannheim we developed the video summarization component and tested it on a large collection of films. In this paper we discuss the particular challenges which the reduction of the video length poses, and report empirical results from the use of our summarization tool.
Stephan Kopf, Thomas Haenselmann, Dirk Farin und Wolfgang Effelsberg. IEEE Operations Center, 2004 Automatic generation of video summaries for historical films . Piscataway, NJA video summary is a sequence of video clips extracted from a longer video. Much shorter than the original, the summary preserves its essential messages. In the ECHO (European Chronicles On-line) project, a system was developed to store and manage large collections of historical films for the preservation of cultural heritage. At the University of Mannheim, we have developed the video summarization component of the ECHO system. We discuss the particular challenges the historical film material poses, and how we have designed new video processing algorithms and modified existing ones to cope with noisy black-and-white films.
Ralf Schmitz, Hannes Hartenstein, Telemaco Melia, Xavier Perez-Costa und Wolfgang Effelsberg. Ges. für Informatik, 2004 Der Einfluss von Schwankungen der Übertragungsweite auf die Leistungsfähigkeit von Ad Hoc Netzwerken GI-Edition : Lecture Notes in Informatics. Proceedings. BonnDie Leistungsfähigkeit eines drahtlosen, mobilen Ad-Hoc Netzwerkes wird im wesentlichen durch die Fähigkeit der Protokolle bestimmt, auf Änderungen der Netzwerktopologie effektiv zu reagieren. Die für diese Netzwerke charakteristische Eigenschaft der Dynamik in der Netztopologie basiert im wesentlichen auf der Mobilität der Knoten und auf Schwankungen der Funkreichweite. Während der Mobilitätsaspekt bereits umfassend untersucht wurde, werden die Eigenschaften des drahtlosen Mediums in Modellen meist idealisiert mittels konstantem Funkradius evaluiert. Solche Ergebnisse werden den tatsächlichen Begebenheiten, wie Erfahrungen in Feldtests belegen, nicht gerecht. In dieser Arbeit untersuchen wir den Einfluss von Mobilität, von zeitabhängigen Schwankungen der Übertragungsreichweite und der Kombination beider Faktoren auf die Netzwerk-Leistungsmerkmale Topologieänderungsrate (Topological Change Rate, TCR) und Linkstabilität. Die temporären Fluktuationen des Funkradius werden mittels eines Gauss-Markov Prozesses erster Ordnung modelliert, während die Auswirkungen der Mobilität basierend auf dem Random Waypoint Mobilitätsmodell untersucht werden. Die Ergebnisse unserer vergleichenden Simulationsstudie zeigen, dass Fluktuationen der Übertragungsreichweite zusätzlich zur Mobilität die Leistungsmetriken eines Ad-Hoc Netzwerkes erheblich beeinflussen. Daher empfehlen wir, Fluktuationen der Radiowellenausbreitung bei dem Entwurf von Ad-Hoc Protokollen und Ad-Hoc Modellierung nicht zu vernachlässigen.
Matthias Transier, Holger Füßler, Thomas Butter und Wolfgang Effelsberg. Ges. für Informatik, 2004 Implementation of the SPBM Routing Protocol for the Linux Kernel . Bonn
Dirk Farin, Peter H. N. de With und Wolfgang Effelsberg. SPIE Press, 2003 A Segmentation System with Model Assisted Completion of Video Objects Proceedings of SPIE. Bellingham, WAThis paper presents a new algorithm for video-object segmentation, which combines motion-based segmentation, high-level object-model detection, and spatial segmentation into a single framework. This joint approach overcomes the disadvantages of these algorithms when applied independently. These disadvantages include the low semantic accuracy of spatial segmentation and the inexact object boundaries obtained from object-model matching and motion segmentation. The now proposed algorithm alleviates three problems common to all motion-based segmentation algorithms. First, it completes object areas that cannot be clearly distinguished from the background because their color is near the background color. Second, parts of the object that are not considered to belong to the object since they are not moving, are still added to the object mask. Finally, when several objects are moving, of which only one is of interest, it is detected that the remaining regions do not belong to any object-model and these regions are removed from the foreground. This suppresses regions erroneously considered as moving or objects that are moving but that are completely irrelevant to the user.
Dirk Farin, Peter H. N. de With und Wolfgang Effelsberg. Werkgemeenschap voor Informatie- en Communicatietheorie, 2003 Optimal Partitioning of Video Sequences for MPEG-4 Sprite Encoding . EnschedeThis paper shows that the concept of merging several views of a non-changing scene-background into a single background sprite is not necessarily the most efficient way to transmit the background image. We have found that the counter-intuitive approach of splitting the background into several independent parts can reduce the overall amount of data. For this reason, we propose an algorithm that provides an optimal partitioning of a video sequence into independent background sprites, resulting in the minimum coding cost. Moreover, our algorithm results in background sprites with better quality by ensuring that the sprite resolution has at least the final display resolution throughout the sequence.
Dirk Farin, Peter H. N. de With und Wolfgang Effelsberg. SPIE Press, 2003 Recognition of User-Defined Video Object Models using Weighted Graph Homomorphisms Proceedings of SPIE. Bellingham, Wash.In this paper, we propose a new system for video object detection based on user-defined models. Object models are described by model graphs in which nodes represent image regions and edges denote spatial proximity. Each node is attributed with color and shape information about the corresponding image region. Model graphs are specified manually based on a sample image of the object. Object recognition starts with automatic color segmentation of the input image. For each region, the same features are extracted as specified in the model graph. Recognition is based on finding a subgraph in the image graph that matches the model graph. Evidently, it is not possible to find an isomorph subgraph, since node and edge attributes will not match exactly. Furthermore, the automatic segmentation step leads to an oversegmented image. For this reason, we employ emph{inexact} graph matching, where several nodes of the image graph may be mapped onto a single node in the model graph. We have applied our object recognition algorithm to cartoon sequences. This class of sequences is difficult to handle with current automatic segmentation algorithms because the motion estimation has difficulties arising from large homogeneous regions and because the object appearance is typically highly variable. Experiments show that our algorithm can robustly detect the specified objects and also accurately locates the object boundary.
Dirk Farin, Peter H. N. de With und Wolfgang Effelsberg. IEEE, 2003 Robust Background Estimation for Complex Video Sequences . Piscataway, NJKnowing the background image of a video scene simplifies the general video-object segmentation problem and therefore it is required by several automatic segmentation algorithms. This paper presents a new background estimation algorithm which is applicable to complex video sequences where many objects are simultaneously visible and the background is visible for a short time period only. The algorithm applies a rough segmentation of the input images into foreground and background regions to exclude the foreground objects from background synthesis. This prevents a bias of the synthesized background image towards the color of foreground objects. Experiments show that the obtained background images differ significantly less from the real background than those obtained with previous algorithms.
Hans Christian Liebig und Wolfgang Effelsberg. Sauerländer, 2003 Automatic Adaption of Exercise Problems to the Proficiency Level of the Learner . BernOnline exercise systems should be able to automatically adapt the level of difficulty of the problems to the level of proficiency of the learner. In our Communication and Tutoring Sys-tem CATS we have implemented a measurement algorithm that keeps track of the perform-ance level of a learner by measuring the percentage of correct answers at the current level, the reliability with which the learner answers the questions and the time he/she takes. From these measures we derive a unified performance parameter that controls the presentation of the next set of questions. These are then generated dynamically by the exercise applet.
Hans Christian Liebig und Wolfgang Effelsberg. IEEE Computer Society Press, 2003 Seamless Integration of Exercise Problems to the Proficiency Level of the Learner . Piscataway, NJDistance learners in traditional online exercise and tutoring systems often get stuck with questions for which they need the help of a tutor or colleague. Learning alone can also be frustrating. In our Communication And Tutoring System, CATS, we have integrated the possibility to dial up a tutor and/or to set up immediate group communication with other distance learners using Internet videoconferencing technology. To find an appropriate partner, we have implemented a measurement algorithm that keeps track of the performance level of a learner by measuring the percentage of correct answers, the reliability with which the learner answers the questions, and the time he/she takes. From these measures we derive a unified performance parameter that controls the presentation of the next set of questions. These are then generated dynamically by CATS. In this paper we explain our pedagogical approach and present the architecture and implementation of the CATS system.
Jürgen Vogel, Jörg Widmer, Dirk Farin, Martin Mauve und Wolfgang Effelsberg. ACM, 2003 Priority-Based Distribution Trees for Application-Level Multicast . New York, NYIn this paper, we propose a novel multicast routing algorithm that is based on application-level priorities and network characteristics: The application may specify an individual priority for each packet-receiver pair. The multicast distribution tree is then constructed such that the higher the priority, the more direct the path from the sender to the packet's destination and the lower the resulting end-to-end delay. This algorithm can be used to realize application-level multicast for delay-sensitive applications such as networked computer games. However, optimizing the multicast tree with respect to the end-to-end delay comes at the cost of an increase in link stress -- the more direct a path, the less likely it is that it can be integrated efficiently into an overlay distribution tree. Our algorithm takes this tradeoff into account and constructs efficient priority-based multicast trees. We demonstrate the performance and characteristics of the algorithm through simulation.
Dirk Farin, Wolfgang Effelsberg und Peter H. N. de With. IEEE Press, 2002 Robust Clustering-Based Video-Summarization with Integration of Domain-Knowledge . Washington, DCClustering techniques have been widely used in automatic video-summarization applications to group shots with comparable content. We enhance the popular k-means clustering algorithm to integrate user-supplied domain-knowledge into the cluster generation step. This provides a convenient way to exclude scenes from the summary which are a-priori known to be irrelevant. Furthermore, we added an additional, time-constrained clustering step preceding the scene clustering step to exclude short ranges with transitional content. This makes the algorithm robust to fading and wipe-effects in the input without requiring explicit cut detection.
Dirk Farin, Michael Käsemann, Peter H. N. de With und Wolfgang Effelsberg. Werkgemeenschap voor Informatie- en Communicatietheorie, 2002 Rate-Distortion Optimal Adaptive Quantization and Coefficient Thresholding for MPEG Coding . EnschedeThis paper presents an MPEG-2 compatible adaptive quantization algorithm that leads to the optimal encoding of I-frames in the sense of maximizing PSNR. It integrates three key features into a single Lagrangian optimization model: adaptive quantization including quantizer-change overhead consideration, coefficient thresholding, and a new coefficient amplitude reduction technique. Our results show that I-frames generated by the TM5 reference encoder are about 1.5-2.0 dB below the theoretical optimum.
Thomas Haenselmann und Wolfgang Effelsberg. SPIE Press, 2002 Texture Resynthesis Using Principle Component Analysis Proceedings of SPIE. Bellingham, Wash.Today's lossless image compression algorithms are not well optimized for high frequency components. These occure especially in textured regions of and image and make image compression ineffective. On the other hand the high demand of storage is not justified since the human visual system perceives texture with regard to it's general structure while omitting specific details. Rather than storing textured parts of an image we present a method for analyzing (in the source image) and resynthesizing (in the decompressed target image) textured regions with regard to it's structural appearance. First we define image blocks in a way that they cover regions with homogenious texture in the source image. These blocks are transformed each in turn. For the transform we use the Karhunen-Loève transform. After the transform into the new domain we statistically analyze the resulting coefficients. For resynthesizing new texture we generate random numbers that exactly meet these statistics. Using the inverse KL-transform the random coefficients are finally transformed back into the spatial domain. The visual appearance of the resulting artificial texture matches the original to a very high degree.
Thomas Haenselmann und Wolfgang Effelsberg. SPIE, 2002 Wavelet-based Semi-automatic Live-wire Segmentation Proceedings of SPIE. Bellingham, Wash.The live-wire approach is a well-known algorithm based on a graph search to locate boundaries for image segmentation. We will extend the original cost function, which is solely based on finding strong edges, so that the approach can take a large variety of boundaries into account. The cost function adapts to the local characteristics of a boundary by analyzing a user-defined sample using a continuous wavelet decomposition. We will finally extend the approach into 3D in order to segment objects in volumetric data, e. g., from medical CT and MR scans.
Gerald Kühne, Joachim Weickert, Markus Beier und Wolfgang Effelsberg. Springer, 2002 Fast Implicit Active Contour Models Lecture Notes in Computer Science. Heidelberg [u.a.]Implicit active contour models are widely used in image processing and computer vision tasks. Most implementations, however, are based on explicit updating schemes and are therefore of limited computational efficiency. In this paper, we present fast algorithms based on the semi-implicit additive operator splitting (AOS) scheme for both the geometric and the geodesic active contour model. Our experimental results with synthetic and real-world images demonstrate that AOS-based implementations clearly outperform their explicit counterparts.
Martin Mauve, Nicolai Scheele, Werner Geyer und Wolfgang Effelsberg. Optimization Software, 2002 Ubiquitous Computing in Education . New York, NY [u.a.]
Claudia Schremmer, Wolfgang Effelsberg, Jean-Claude Grattarola und Edoardo Berera. net4net [u.a.], 2002 A Novel Student Cooperation Across Country Borders . Berne [u.a.]In the winter term 2001/02, the universities of Mannheim/Germany and Nice/France have invented a new form of student cooperation on a tele-seminar basis. Our international tele-seminar on e-commerce encompassed a joint introductory week in Nice, cooperative student work in bi-national teams during the winter term, and a concluding joint week in Mannheim with a presentation of the groups' results. Twelve students of each university were selected to participate at this seminar. Since it could not be expected from neither side to master the other's language, the common language was defined to be English. In this paper we describe the set-up of the tele-seminar and its technical, peda-gogic, and cultural issues for the students and their teachers.
Volker Hilt, Martin Mauve und Wolfgang Effelsberg. IEEE Computer Soc., 2001 A Light-Weight Repair Protocol for the Loss-Free Recording of MBone Sessions . Los Alamitos, Calif. [u.a.]With the increasing popularity of MBone conferences, the need arose to archive the multimedia streams of these conferences. Like all network applications, a conference recorder is subject to packet loss, which introduces gaps into recorded media streams. Such gaps degrade the playback quality of an archived media stream or even disable the correct playback. In this paper, we present a novel scheme for the loss-free recording of media streams. In contrast to existing systems that require the placement of recording caches within the network, our approach enables an end-to-end system design. We present a detailed protocol analysis that confirms the validity of our approach.
Volker Hilt, Martin Mauve, Jürgen Vogel und Wolfgang Effelsberg. ACM Order Dep., 2001 Interactive Media on Demand: Generic Recording and Replay of Interactive Media Streams . New York, NYIn this demonstration we present a generic recording service for distributed interactive media, i.e., media which allow a distributed group of users to interact with the medium itself. Typical examples of this media class are shared whiteboard systems, distributed virtual environments and networked computer games. By defining an abstract model and an application level protocol we were able to develop the first generic recording service for arbitrary distributed interactive media. This service is called Interactive Media on Demand (IMoD), and it is able to record and replay all applications that are based on the RTP/I protocol. In particular it allows random access to the recorded media streams. We demonstrate the IMoD system by recording and replaying a shared whiteboard, a networked computer game and a 3D telecooperation application.
Claudia Schremmer, Christoph Kuhmünch und Wolfgang Effelsberg. IEEE, 2001 Layered Wavelet Coding for Video . [Piscataway, NJ]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.
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.
Wolfgang Effelsberg. Shaker, 1999 Erfahrungen aus den TeleTeaching-Projekten der Universität Mannheim . Aachen
Wolfgang Effelsberg. WAKI [u.a.], 1999 Kommunikationsunterstützung für TeleTeaching . [Flensburg]
Volker Hilt, Martin Mauve, Christoph Kuhmünch und Wolfgang Effelsberg. Springer, 1999 A Generic Scheme for the Recording of Interactive Media Streams Lecture Notes in Computer Science. Berlin [u.a.]Interactive media streams with real-time characteristics, such as those produced by shared whiteboards, distributed Java applets or shared VRML view-ers, are rapidly gaining importance. Current solutions to the recording of interac-tive media streams are limited to one specific application (e.g. one specific shared whiteboard). In this paper we present a generic recording service that enables the recording and playback of this new class of media. To facilitate the generic recording we have defined a profile for the Real-Time Transport Proto-col (RTP) that covers common aspects of the interactive media class in analogy to the profile for audio and video. Based on this profile we introduce a general-ized recording service that enables the recording and playback of arbitrary inter-active media.
Martin Mauve, Volker Hilt, Christoph Kuhmünch und Wolfgang Effelsberg. IEEE Computer Soc., 1999 A General Framework and Communication Protocol for the Transmission of Interactive Media with Real-Time Characteristics . Los Alamitos, Calif. [u.a.]In this paper we present a general framework for the transmission of interactive media with real-time characteristics, i.e. media involving user interaction. By identifying and supporting the common aspects of interactive media the framework allows the development of generic services for distributed, collaborative work involving the transmission of interactive media.
Silvia Pfeiffer, Rainer Lienhart und Wolfgang Effelsberg. IEEE Computer Soc. Press, 1999 Scene Determination Based on Video and Audio Features . Los Alamitos, Calif. [u.a.]Determining automatically what constitutes a scene in a video is a challenging task, particularly since there is no precise definition of the term scene. It is left to the individual to set attributes shared by consecutive shot which group them into scenes. Certain basic attributes such as dialogs, like settings and continuing sounds are consis-tent indicators. We have therefore developed a scheme for identifying scenes which clusters shots according to detected dialogs, like settings and similar audio. Results from experiments show automatic identification of these types of scenes to be reliable.
Albert Banchs, Wolfgang Effelsberg, Christian Tschudin und Volker Turau. IEEE Press, 1998 Multicasting multimedia streams with active networks . Los Alamitos, Calif.
Wolfgang Effelsberg. Springer, 1998 Erfahrungen aus den TeleTeaching-Projekten der Universität Mannheim . Berlin [u.a.]
Wolfgang Effelsberg. VDE-Verlag, 1998 Erfahrungen aus den TeleTeaching-Projekten der Universität Mannheim ITG-Fachbericht. Berlin [u.a.]
Wolfgang Effelsberg und Werner Geyer. Kluwer, 1998 Tools for Digital Lecturing - What We Have and What We Need . DeventerIn the past many distance learning projects have concentrated on the development of educational multimedia material for offline use. Effective learning requires online contact between teachers and students, and also among students. In this paper we claim that the multimedia application software we have today is insufficient for online (synchronous) teleteaching. We list the requirements for good teleteaching tools, analyze the deficiencies of existing software for the purpose of teleteaching, and present the teleteaching tools currently under development at the University of Mannheim.
Wolfgang Effelsberg, Werner Geyer und Andreas Eckert. Springer, 1998 Project TeleTeaching Mannheim-Heidelberg Proceedings of the ... annual conference of the Gesellschaft für Klassifikation e.V.. Berlin [u.a.]The technology needed for teleteaching is widely available today. Interest focuses on the use of multimedia technology and high-speed networks to disseminate course content and work and deepen understanding on the part of the students. The Universities of Mannheim and Heidelberg are engaged in a joint pilot project to develop and test new technologies for teleteaching in a digital network. High-capacity multimedia workstations and PSs are linked via ATM to enable access over the network to lectures, exercises and stored teaching materials. The departments of education and psychology of the two universities are scientifically advising and evaluating the project.
Werner Geyer und Wolfgang Effelsberg. AACE , 1998 The Digital Lecture Board - A Teaching and Learning Tool for Remote Instruction in Higher Education . Charlottesville, Va.This paper presents a novel, integrated teaching and learning tool - called digital lecture board - which takes into account the requirements of synchronous, computer-based distance education. For almost two years, the TeleTeaching project Mannheim-Heidelberg has been using video conferencing tools for transmitting lectures and seminars. These tools prove to be insufficient for the purpose of teleteaching since they are not powerful enough to support team work, they are not flexible enough for the use of media, and are somewhat difficult to handle by non-experts. We discuss shortcomings of the existing tools and disclose features we had in mind while designing the digital lecture board. Embedded in a teaching and learning system, the digital lecture board even allows for asynchronous usage modes, for instance, the preparation of lectures. Moreover, we cover implementation issues of the current prototype.
Rainer Lienhart, Wolfgang Effelsberg und Ramesh Jain. SPIE, 1998 Towards a Visual Grep: A systematic analysis of various methods to compare video sequences . Bellingham, Wash.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. Promising experimental results are presented.
Rainer Lienhart, Wolfgang Effelsberg und Ramesh Jain. SPIE, 1998 VisualGREP: A Systematic Method to Compare and Retrieve Video Sequences Proceedings of SPIE. Bellingham, Wash.
Silvia Pfeiffer, Rainer Lienhart, Gerald Kühne und Wolfgang Effelsberg. Springer , 1998 The MoCA Project - Movie Content Analysis Research at the University of Mannheim Informatik '98 : Informatik zwischen Bild und Sprache. Berlin, Heidelberg
Andreas Eckert, Werner Geyer und Wolfgang Effelsberg. AACE, 1997 A Distance Learning System for Higher Education Based on Telecommunications and Multimedia . Charlottesville, Va.This paper addresses the Semi-virtual Multidimensional Distance Learning System (SMDL), which is a technical, pedagogical, and organisational prototype-structure of a semi-virtual university. SDML includes both synchronous and asynchronous learning modes. During the initial stage of our project, we regularly transmitted a lecture from a specially equipped lecture room in one university to an equally equipped lecture room in another university using ATM technology. The project is evaluated with consideration to technical and pedagogical issues. A variety of technical problems could be addressed during the regular transmission of the lecture for the course of a semester. Empirical data suggested that the remote students were appreciating the new technologies, whereas the local students seemed to be somewhat sceptical. Moreover, the organisational problems in setting up a semi-virtual university seem to be vastly underestimated in comparison to the technical issues.
Wolfgang Effelsberg. Karlsruher Kongreß und Ausstellungs-GmbH, 1997 Das Projekt TeleTeaching der Universitäten Mannheim und Heidelberg . Karlsruhe
Thomas T. Fuhrmann, Christoph Kuhmünch, Gunther Schöppe, Gerald Pätzold, Dieter W. Heermann und Wolfgang Effelsberg. Deutsche Telekom AG, Technologiezentrum Darmstadt, 1997 Java Teachware - The Java Remote Control Tool and its Applications . Darmstadt
Rainer Lienhart, Christoph Kuhmünch und Wolfgang Effelsberg. Springer, 1997 Aufspüren und Erkennen von Werbung in laufenden Fernsehsendungen Mustererkennung. Berlin [u.a.]Fersehwerbung ist in vielerlei Hinsicht interessant: Werbedesigner und Psychologen interessieren sich für ihren (positiven) Einfluß auf das Kaufverhalten der Menschen; Eltern andererseits möchten ihre Kinder besser vor dem Einfluß der Werbung schützen. In diesem Artikel werden zwei Methoden zum Aufspüren und Erkennen von Werbung in laufenden Fernsehsendungen beschrieben. Die erste Methode basiert auf meßbaren, statistischen Merkmalen von Werbespots und Werbeblöcken und ermöglicht so deren schnelle Lokalisierung. Die zweite Methode basiert auf einer Werbespotdatenbank und erlaubt es, Werbespots präzise aufspüren und zu erkennen. Zuletzt wird gezeigt, wie beide Verfahren in einem selbstlernenden System integriert werden können.
Rainer Lienhart, Christoph Kuhmünch und Wolfgang Effelsberg. IEEE Computer Soc. Press, 1997 On the Detection and Recognition of Television Commercials . Los Alamitos, Calif. [u.a.]
Rainer Lienhart, Silvia Pfeiffer und Wolfgang Effelsberg. IEEE Computer Soc. Press, 1996 The MoCA Workbench: Support for Creativity in Movie Content Analysis . Los Alamitos, Calif.
Silvia Pfeiffer, Stephan Fischer und Wolfgang Effelsberg. ACM Press, 1996 Automatic Audio Content Analysis . New York, NYThis paper describes the theoretic framework and applications of automatic audio content analysis. After explaining the basic properties of audio analysis, we present a toolbox being the basis for the development of audio analysis algorithms. We also describe new applications which can be developed using the toolset, among them music indexing and retrieval as well as violence detection in the sound track of videos.
Stefan Fischer und Wolfgang Effelsberg. Chapman & Hall, 1995 Efficient Configuration of Protocol Software for Multiprocessors . London [u.a.]
Stephan Fischer, Rainer Lienhart und Wolfgang Effelsberg. ACM Press, 1995 Automatic Recognition of Film Genres . New York, NY
Ralf Keller, Wolfgang Effelsberg und Bernd Lamparter. Springer, 1994 Performance Bottlenecks in Digital Movie Systems Lecture Notes in Computer Science. Berlin [u.a.]
Ralf Keller, Stefan Fischer und Wolfgang Effelsberg. IEEE Computer Soc. Press, 1994 Implementing Movie Control, Access and Management - From a Formal Description to a Working Multimedia System . Los Alamitos, Calif. [u.a.]
Bernd Lamparter und Wolfgang Effelsberg. Springer, 1994 Extended Color Cell Compression - A Runtime-efficient Compression Scheme for Software Video Lecture Notes in Computer Science. Berlin [u.a.]
Ralf Keller und Wolfgang Effelsberg. ACM Press, 1993 MCAM: An Application Layer Protocol for Movie Control, Access and Management . New York, NY
Thomas Meyer-Boudnik, Wolfgang Effelsberg und Ralf Steinmetz. IEEE Computer Soc. Press, 1993 A Taxonomy on Multimedia-Synchronization . Los Alamitos, Calif. [u.a.]
Bernd Hofmann und Wolfgang Effelsberg. Springer, 1992 Generating Parallel Code from Estelle Specifications . Berlin [u.a.]
Bernd Hofmann, Wolfgang Effelsberg, Theo Held und Heinz König. IEEE, 1992 On the Parallel Implementation of OSI Protocols . [New York, NY]
Bernd Lamparter und Wolfgang Effelsberg. Springer, 1992 XMOVIE: Transmission and Presentation of Digital Movies under X Lecture Notes in Computer Science. Berlin [u.a.]
Bernd Lamparter und Wolfgang Effelsberg. Springer, 1991 XMOVIE : Digitale Filmübertragung und Darstellung unter X-Windows . Heidelberg [u.a.]
Martin Strecker, Udo Bär, Wolfgang Effelsberg und Willi Stoll. North-Holland, 1991 Presentation Layer Conformance Testing with TTCN . Amsterdam
Stefan Pappe, Winfried Lamersdorf und Wolfgang Effelsberg. Springer , 1988 Specification and Implementation of a Standard for Remote Database Access Lecture Notes in Computer Science. Berlin [u.a.]
Winfried Lamersdorf, Henning Eckhardt und Wolfgang Effelsberg. IEEE Computer Soc. Press, 1987 Database Programming for Distributed Office Systems Lecture Notes in Computer Science. Washington, DC
Stefan Pappe, Wolfgang Effelsberg und Winfried Lamersdorf. Springer, 1987 Database Access in Open Systems Lecture Notes in Computer Science. Berlin [u.a.]
Stefan Pappe, H.-L. Heil, Wolfgang Effelsberg und Winfried Lamersdorf. Springer, 1987 Datenbankzugriff in offenen Rechnernetzen Informatik-Fachberichte : IFB. Berlin [u.a.]
Wolfgang Effelsberg und Winfried Lamersdorf. Teubner, 1985 Strukturierung von Büroaktivitäten Berichte des German Chapter of the ACM. Stuttgart
Michael V. Mannino und Wolfgang Effelsberg. IEEE Computer Soc. Press, 1984 Matching Techniques in Global Schema Design . Silver Spring, Md.
Michael V. Mannino, Benn R. Konsynski und Wolfgang Effelsberg. ACM Press, 1983 Requirements Specification in Global Schema Design . Baltimore, Md.
Wolfgang Effelsberg, Theo Härder, Andreas Reuter und Jörg Schultze-Bohl. Springer, 1981 Leistungsanalyse von Datenbanksystemen - Messmethoden und Messumgebung Informatik-Fachberichte : IFB. Berlin [u.a.]
Wolfgang Effelsberg, Theo Härder und Andreas Reuter. Heyden, 1980 Measurement and Evaluation of Techniques for Implementing COSETS - A Case Study . London [u.a.]
Wolfgang Effelsberg, Theo Härder und Andreas Reuter. Springer , 1979 Leistungsanalyse von Datenbanksystemen durch Messung, analytische Modelle und Simulation Informatik-Fachberichte : IFB. Berlin [u.a.]

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