Journal Articles

  • Philip Mildner, Tonio Triebel, Stephan Kopf und Wolfgang Effelsberg. 2017 Scaling online games with NetConnectors : a peer-to-peer overlay for fast-paced massively multiplayer online games Computers in Entertainment : CIE, 15, 9, 1-21
    This article presents a peer-to-peer overlay for massively multiplayer online games with a focus on fast-paced action. More than other genres, action games like first-person shooters employ fast and dynamic game mechanics. In multiplayer environments, these properties have to be reflected by the underlying network structure. At the same time, the system should be able to support a huge amount of users in order to deliver a massive experience to the participating players. The capacity of current client/server systems limits the number of players in a game, preventing the desired massive experience. To provide both a scalable and a responsive system, we use a fully distributed peer-to-peer network with a dynamic connection scheme. By exploiting local interests in the virtual world, our system supports a huge number of users. Therefore, an area-of-interest mechanism is applied to the connection scheme. Users do not connect to all participating users, but they only establish connections to other users they are interested in. These neighbors are determined by the user's perception of the virtual world. Instead of using a purely distance-based approach, our system uses a more flexible neighbor-based approach that supports the use of multiple metrics to determine the set of interesting nodes for each user. A second kind of connection—so-called NetConnectors—utilizes the players' distribution in the virtual world to ensure overlay consistency. For the dissemination of messages, we use a publish/subscribe mechanism. This prevents inconsistencies introduced by unidirectional neighborhood relations that can occur with sender-oriented models. Further, the publish/subscribe mechanism models the users' interests more accurately. In addition to the regular sending mechanism, we implemented a Geocast algorithm that allows information distribution to arbitrary regions of the virtual world. While regular messages are always addressed to specific users, Geocasts cover certain geographical regions. Thus, Geocasts can be used to disseminate messages to all users that are located in the addressed region. Simulations show that our design performs well in terms of scalability. By keeping the amount of connections per user nearly constant, users do not get overloaded with too many connections. This also applies for crowded regions where the user density is much higher compared to an evenly populated virtual world. Another important aspect of fast-paced multiplayer games is the users' motion behavior. Different movement strategies are evaluated for their impact on network load and connection dynamics.
  • Stefan Wilk, Stephan Kopf und Wolfgang Effelsberg. 2016 Collaborative annotation of videos relying on weak consistency ACM Transactions on Multimedia Computing, Communications, and applications : TOMCCAP, 12, 9, Article 45
  • Philipp Schaber, Stephan Kopf, Sina Wetzel, Tyler Ballast, Christoph Wesch und Wolfgang Effelsberg. 2015 CamMark: Analyzing, Modeling, and Simulating Artifacts in Camcorder Copies ACM Transactions on Multimedia Computing, Communications, and applications : TOMCCAP, 11, 10, Article 42, 1-23
    To support the development of any system that includes the generation and evaluation of camcorder copies, as well as to provide a common benchmark for robustness against camcorder copies, we present a tool to simulate digital video re-acquisition using a digital video camera. By resampling each video frame, we simulate the typical artifacts occurring in a camcorder copy: geometric modifications (aspect ratio changes, cropping, perspective and lens distortion), temporal sampling artifacts (due to different frame rates, shutter speeds, rolling shutters, or playback), spatial and color subsampling (rescaling, filtering, Bayer color filter array), and processing steps (automatic gain control, automatic white balance). We also support the simulation of camera movement (e.g., a hand-held camera) and background insertion. Furthermore, we allow for an easy setup and calibration of all the simulated artifacts, using sample/reference pairs of images and videos. Specifically temporal subsampling effects are analyzed in detail to create realistic frame blending artifacts in the simulated copies. We carefully evaluated our entire camcorder simulation system and found that the models we developed describe and match the real artifacts quite well.
  • Benjamin Guthier, Stephan Kopf, Matthias Wichtlhuber und Wolfgang Effelsberg. 2014 Parallel Implementation of a Real-Time High Dynamic Range Video System Integrated Computer-Aided Engineering : ICAE, 21, 63, 189-202
  • Max Lehn, Tonio Triebel, Robert Rehner, Benjamin Guthier, Stephan Kopf, Alejandro Buchmann und Wolfgang Effelsberg. 2014 On Synthetic Workloads for Multiplayer Online Games: A Methodology for Generating Representative Shooter Game Workloads Multimedia Systems, 20, 53, 609-620
  • Benjamin Guthier, Stephan Kopf und Wolfgang Effelsberg. 2013 Algorithms for a Real-Time HDR Video System Pattern Recognition Letters, 34, 9, 25 -33
  • Daniel Schön, Melanie Klinger, Stephan Kopf und Wolfgang Effelsberg. 2012 MobileQuiz - A Lecture Survey Tool using Smartphones and QR Tags International Journal of Digital Information and Wireless Communications : IJDIWC, 2, 10, 231-244
  • Stephan Kopf, Thomas Haenselmann, Johannes Kiess, Benjamin Guthier und Wolfgang Effelsberg. 2011 Algorithms for video retargeting Multimedia Tools and Applications, 51, 19, 819-861
  • Colin Atkinson, Philipp Bostan, Thomas Butter und Wolfgang Effelsberg. 2009 A Privacy-Maintaining Framework for Context-Sensitive Service Discovery Services International Journal on Advances in Internet Technology, 2, 2, 15-28
  • Thomas Haenselmann, Marcel Busse, Stephan Kopf, Thomas King und Wolfgang Effelsberg. 2009 Multi perspective panoramic imaging Image and Vision Computing, 27, 3, 391-401
  • Stephan Kopf und Wolfgang Effelsberg. 2009 Mobile cinema: canonical processes for video adaptation Multimedia Systems, 14, 2, 369-375
  • Fleming Lampi, Hendrik Lemelson, Stephan Kopf und Wolfgang Effelsberg. 2009 A Question Managing Suite for Automatic Lecture Recording Interactive Technology and Smart Education : ITSE, 6, 7, 108-118
  • Marcel Busse, Thomas Haenselmann und Wolfgang Effelsberg. 2008 Energy-efficient forwarding in wireless sensor networks Pervasive and Mobile Computing, 4, 3, 3-32
  • Thomas Haenselmann, Marcel Busse, Thomas King und Wolfgang Effelsberg. 2008 Unequal Weighting for Improved Positioning in GPS-less Sensor Networks EURASIP Journal on Advances in Signal Processing, 2008, 3, Art. ID 281635
  • Fleming Lampi, Stephan Kopf, Manuel Benz und Wolfgang Effelsberg. 2008 A Virtual Camera Team for Lecture Recording IEEE MultiMedia, 15, 4, 58-61
  • Thomas Haenselmann, Thomas King, Marcel Busse, Wolfgang Effelsberg und Markus Fuchs. 2007 Skriptbasierte drahtlose Gebäudeautomation mit Sensornetzen Praxis der Informationsverarbeitung und Kommunikation : PIK, , 1, 163-169
  • Stephan Kopf und Wolfgang Effelsberg. 2007 New Teaching and Learning Technologies for Interactive Lectures Advanced Technology for Learning, 4, 2, 60 - 67
  • Matthias Transier, Holger Füßler, Jörg Widmer, Martin Mauve und Wolfgang Effelsberg. 2007 A Hierarchical Approach to Position-Based Multicast for Mobile Ad-hoc Networks Wireless Networks : WN, 13, 4, 447-460
  • Karoly Farkas, Oliver Wellnitz, Matthias Dick, Xiaoyuan Gu, Marcel Busse, Wolfgang Effelsberg, Yacine Rebahi, Dorgham Sisalem, Dan Grigoras und Kyriakos Stefanidis. 2006 Real-time Service Provisioning for Mobile and Wireless Networks Computer Communications, 25, 2, 540-550
  • Holger Füßler, Marc Torrent-Moreno, Hannes Hartenstein, Matthias Transier, Roland Krüger und Wolfgang Effelsberg. 2006 Studying vehicle movements on highways and their impact on ad-hoc connectivity Mobile Computing and Communications Review : : MC2R, 10, 2, 26-27
  • Thomas King, Thomas Haenselmann, Stephan Kopf und Wolfgang Effelsberg. 2006 Positionierung mit Wireless-LAN und Bluetooth Praxis der Informationsverarbeitung und Kommunikation : PIK, 29, 4, 9-17
  • Martin Mauve, Jürgen Vogel, Volker Hilt und Wolfgang Effelsberg. 2004 Local-lag and Timewarp : Providing Consistency for Replicated Continuous Applications IEEE Transactions on Multimedia, 6, 2, 47-57
    In this paper we investigate how consistency can be established for replicated applications changing their state in reaction to user-initiated operations as well as the passing of time. Typical examples of these applications are networked computer games and distributed virtual environments. We give a formal definition of the terms consistency and correctness for this application class. Based on these definitions, it is shown that an important tradeoff relationship exists between the responsiveness of the application and the appearance of short-term inconsistencies. We propose to exploit the knowledge of this tradeoff by voluntarily decreasing the responsiveness of the application in order to eliminate short-term inconsistencies. This concept is called local-lag. Furthermore, a timewarp scheme is presented that complements local-lag by guaranteeing consistency and correctness for replicated continuous applications. The computational complexity of the timewarp algorithm is determined in theory and practice by examining a simple networked computer game. The timewarp scheme is then compared to the well-known dead-reckoning approach. It is shown that the choice between both schemes is application-dependent.
  • Roy Pea, Michael Mills, Joseph Rosen, Kenneth Dauber, Wolfgang Effelsberg und Eric Hoffert. 2004 The DIVER Project : Interactive Digital Video Repurposing IEEE MultiMedia, 11, 2, 54-61
  • Jürgen Vogel, Martin Mauve, Volker Hilt und Wolfgang Effelsberg. 2003 Late Join Algorithms for Distributed Interactive Applications Multimedia systems / Association for Computing Machinery, 9, 2, 327-336
    Distributed interactive applications such as shared whiteboards and multiplayer games often support dynamic groups where users may join and leave at any time. A participant joining an ongoing session has missed the data that have previously been exchanged by the other session members. It is therefore necessary to initialize the application instance of the latecomer with the current state. In this paper, we propose a late join algorithm for distributed interactive applications that provides such an initialization of applications. The algorithm is scalable and robust and can be easily adapted to the needs of different applications by means of late join policies. The behavior of the late join algorithm and the impact of design alternatives are investigated in detail by means of an extensive simulation study. This study also shows that an improper handling of the late join problem can cause very high application and network load.
  • Martin Mauve, Hannes Hartenstein, Holger Füßler, Jörg Widmer und Wolfgang Effelsberg. 2002 Positionsbasiertes Routing für die Kommunikation zwischen Fahrzeugen Informationstechnik und technische Informatik : it + ti, 44, 2, 278-286
    In the near future communication between vehicles by means of wireless technology will enhance both safety and comfort of the passengers. One main challenge in realizing this communication will be the routing of messages from one sender to one or more receivers. In this paper we propose a position-based ad-hoc routing protocol which solves this problem. In this protocol all vehicles work together, thus no pre-established infrastructure is required. As a consequence, the resulting network is inexpensive and robust. In order to prove the viability of the approach, a simulation study was performed using the ns-2 network simulator. As a basis for this study realistic car movement patterns were used. The study shows that even over large distances requiring message forwarding by multiple vehicles, high success rates for the delivery of messages are achieved.
  • Martin Mauve, Volker Hilt, Christoph Kuhmünch und Wolfgang Effelsberg. 2001 RTP/I - Toward a Common Application Level Protocol for Distributed Interactive Media IEEE Transactions on Multimedia, 3, 2, 152-161
  • Silvia Pfeiffer, Rainer Lienhart und Wolfgang Effelsberg. 2001 Scene Determination Based on Video and Audio Features Multimedia Tools and Applications, 15, 4, 59-81
  • 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.
  • Wolfgang Effelsberg. 1998 Music in Multimedia Systems : Guest Editor's Introduction IEEE MultiMedia, 5, 2, 16
  • Wolfgang Effelsberg und Christoph Hornung. 1998 Lehren und Lernen im Internet Informationstechnik und technische Informatik : it + ti, 40, 2, 16-22
  • Michael V. Mannino, Shamkant B. Navathe und Wolfgang Effelsberg. 1998 A Rule-Based Approach for Merging Generalization Hierarchies Information Systems : IS, 13, 2, 257-272
  • Rainer Lienhart, Silvia Pfeiffer und Wolfgang Effelsberg. 1997 Video Abstracting Communications of the ACM, 40, 2, 55-62
  • Reinhard Gotzhein, Jan Bredereke, Wolfgang Effelsberg, Stefan Fischer, Thomas Held und Hartmut König. 1996 Improving the Efficiency of Automated Protocol Implementation Using Estelle Computer Communications, 19, 2, 1226-1235
  • Reinhard Gotzhein, Jan Bredereke, Wolfgang Effelsberg, Stefan Fischer, Thomas Held und Hartmut König. 1996 Improving the Efficiency of Automated Protocol Implementations Using Estelle Computer Communications, 19, 2, 1226-1235
  • Silvia Pfeiffer, Rainer Lienhart, Stephan Fischer und Wolfgang Effelsberg. 1996 Abstracting Digital Movies Automatically Journal of Visual Communication and Image Representation, 7, 3, 345-353
    Large video on demand databases consisting of thousands of digital movies are not easy to handle: the user must have an attractive means to retrieve his movie of choice. For analog video, movie trailers are produced to allow a quick preview and perhaps stimulate possible buyers. This paper presents techniques to automatically produce such movie abstracts of digtial videos.
  • Wolfgang Effelsberg. 1995 Das Projekt TeleTeaching der Universitäten Heidelberg und Mannheim Praxis der Informationsverarbeitung und Kommunikation : PIK, 18, 2, 205-208
  • Ralf Keller und Wolfgang Effelsberg. 1995 Effiziente Verarbeitung von multimedialen Datenströmen in Window-Systemen Informationstechnik und technische Informatik : it + ti, 37, 3, 11-17
  • Ralf Keller, Wolfgang Effelsberg und Bernd Lamparter. 1995 Xmovie: Architecture and Implementation of a Distributed Movie System ACM Transactions on Office Information Systems : TOIS, 13, 4, 471-495
  • Thomas Meyer-Boudnik und Wolfgang Effelsberg. 1995 MHEG Explained IEEE MultiMedia, 2, 2, 26-38
  • Hartmut König, Wolfgang Effelsberg und Reinhard Gotzhein. 1993 Ableitung parallel ausführbarer Protokollimplementierungen Praxis der Informationsverarbeitung und Kommunikation : PIK, 16, 2, 193-202
  • Ralf Keller, Bernd Lamparter und Wolfgang Effelsberg. 1992 Erweiterung von X für digitale Filme Praxis der Informationsverarbeitung und Kommunikation : PIK, 15, 4, 196-204
  • Bernd Lamparter, Wolfgang Effelsberg und Norman Michl. 1992 MTP: A Movie Transmission Protocol for Multimedia Applications Computer Communication Review, 22, 3, 71-72
  • Wolfgang Effelsberg. 1990 Hochgeschwindigkeitsnetze Praxis der Informationsverarbeitung und Kommunikation : PIK, , 1, 184-190
  • Wolfgang Effelsberg. 1987 Datenbankzugriff in Rechnernetzen Informationstechnik : it, 29, 2, 140-153
  • Albert Fleischmann, Seung-Tae Chin und Wolfgang Effelsberg. 1987 Specification and Implementation of an ISO Session Layer IBM Systems Journal, 26, 2, 255-275
  • Wolfgang Effelsberg und Albert Fleischmann. 1986 Das ISO-Referenzmodell für offene Systeme und seine sieben Schichten Informatik-Spektrum, 9, 2, 280-299
  • Wolfgang Effelsberg und Theo Härder. 1984 Principles of Database Buffer Management ACM Transactions on Database Systems : TODS, 9, 4, 560-595
  • Wolfgang Effelsberg und Mary E. S. Loomis. 1984 Logical, Internal and Physical Reference Behavior in CODASYL Database Systems ACM Transactions on Database Systems : TODS, 9, 2, 187-213
  • Wolfgang Effelsberg und Michael V. Mannino. 1984 Attribute Equivalence in Global Schema Design for Heterogeneous Distributed Databases Information Systems : IS, 9, 3, 237-240
  • Wolfgang Effelsberg. 1983 Fixing Pges in a Database Buffer SIGMOD record / Association for Computing Machinery, Special Interest Group on Management of Data, 13, 2, 52-59
  • Wolfgang Effelsberg, Theo Härder und Andreas Reuter. 1980 An Experiment in Learning DBTG Database Administration Information Systems : IS, 5, 2, 137-148
  • Wolfgang Effelsberg. 1979 Messung und Auswertung des Seitenreferenzverhaltens von Datenbanksystemen Angewandte Informatik, 21, 2, 434-440