[48] | Roland Tusch, Laszlo Böszörmenyi, Balázs Goldschmidt, Hermann Hellwagner, Peter Schojer, Offensive and Defensive Adaptation in Distributed Multimedia Systems, In Proceedings of ICETA 2003, 2nd International Conference on Emerging Telecommunications Technologies and Applications (F Jakab, A Cizmar, eds.), Elfa, Košice, Slovak Republic, pp. 17-19, 2003.
[bib] [abstract]
Abstract: Adaptation is usually restricted to defensive, reactive media adaptation (often called stream-level adaptation). We argue that offensive, proactive, system-level adaptation deserves not less attention. If a distributed multimedia system cares for overall, end-to-end quality of service then it should provide a meaningful combination of both. We introduce an adaptive multimedia server (ADMS) and a supporting middleware which implement offensive adaptation based on a lean, flexible architecture. The measured costs and benefits of the offensive adaptation process are presented. We introduce an intelligent video proxy (QBIX), which implements defensive adaptation. The cost/benefit measurements of QBIX are presented elsewhere \citeSchojer03. We show the benefits of the integration of QBIX in ADMS. Offensive adaptation is used to find an optimal, user-friendly configuration dynamically for ADMS, and defensive adaptation is added to take usage environment (network and terminal) constraints into account.
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[47] | Christian Timmerer, Gabriel Panis, Harald Kosch, Jörg Heuer, Hermann Hellwagner, Andreas Hutter, Coding format independent multimedia content adaptation using XML, In Proceedings of SPIE International Symposium ITCom 2003 on Internet Multimedia Managment Systems IV, Vol. 5242 (A N, ed.), SPIE Press, Orlando, pp. 92-103, 2003.
[bib] [pdf] [abstract]
Abstract: Due to the heterogeneity of the current terminal and network infrastructures, multimedia content needs to be adapted to specific capabilities of these terminals and network devices. Furthermore, user preferences and user environment characteristics must also be taken into consideration. The problem becomes even more complex by the diversity of multimedia content types and encoding formats. In order to meet this heterogeneity and to be applicable to different coding formats, the adaptation must be performed in a generic and interoperable way. As a response to this problem and in the context of MPEG-21, we present an approach which uses XML to describe the high-level structure of a multimedia resource in a generic way, i.e., how the multimedia content is organized, for instance in layers, frames, or scenes. For this purpose, a schema for XML-based bitstream syntax descriptions (generic Bitstream Syntax Descriptions or gBSDs) has been developed. A gBSD can describe the high-level structure of a multimedia resource in a coding format independent way. Adaptation of the resource is based on elementary transformation instructions formulated with respect to the gBSDs. These instructions have been separated from the gBSDs in order to use the same descriptions for different adaptations, e.g., temporal scaling, SNR scaling, or semantic adaptations. In the MPEG-21 framework, those adaptations can be steered for instance by the network characteristics and the user preferences. As a result, it becomes possible for coding format agnostic adaptation engines to transform media bitstreams and associated descriptions to meet the requirements imposed by the network conditions, device capabilities, and user preferences.
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[46] | Peter Schojer, Laszlo Böszörmenyi, Hermann Hellwagner, Bernhard Penz, Stefan Podlipnig, Architecture of a Quality Based Intelligent Proxy (QBIX) for MPEG-4 Videos, In The Twelfth International World Wide Web Conference (Gusztáv Hencsey, Bebo White, eds.), ACM, New York, USA, pp. 394-402, 2003.
[bib][url] [abstract]
Abstract: Due to the increasing availability and use of digital video data on the Web, video caching will be an important performance factor in the future WWW. We propose an architecture of a video proxy cache that integrates modern multimedia and communication standards. Especially we describe features of the MPEG-4 and MPEG-7 multimedia standards that can be helpful for a video proxy cache. QBIX supports real-time adaptation in the compressed and in the decompressed domain. It uses adaptation to improve the cache replacement strategies in the proxy, but also to realize media gateway functionality driven by the clients' terminal capabilities.
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[45] | Gabriel Panis, Andreas Hutter, Jörg Heuer, Hermann Hellwagner, Harald Kosch, Christian Timmerer, Sylvain Devillers, Myriam Amielh, Bitstream Syntax Description: A Tool for Multimedia Resource Adaptation within MPEG-21, In Signal Processing: Image Communication, Elsevier B.V., vol. Vol. 18, Special Issue on Multimedia Adaptation, no. 8, Amsterdam, Netherlands, pp. 721-747, 2003.
[bib] [pdf] [abstract]
Abstract: In this paper, a generic method is described to allow the adaptation of different multimedia resources by a single, media resource-agnostic processor. This method is based on an XML description of the media resources bitstream syntax, which can be transformed to reflect the desired adaptation and then be used to generate an adapted version of the bitstream. Based on this concept, two complementary technologies, BSDL and gBS Schema, are presented. The two technologies provide solutions for parsing a bitstream to generate its XML description, for the generic structuring of this description, and the generation of an adapted bitstream using its transformed description. The two technologies can be used as stand-alone tools; however, a joint approach has been developed in order to harmonise the two solutions and exploit their strengths. Since BSDL has been presented in previous publications, this paper is focusing more on the gBS Schema and the joint BSDL/gBS Schema approach.
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[44] | Mathias Ohlenroth, Hermann Hellwagner, A Protocol for Adaptation-aware Multimedia Streaming, In ICME 2003 Proceedings CD-Rom (Billene Mercer, St Cantu, Ch Garza, B Stewart, eds.), NA, NA, pp. 1-4, 2003.
[bib] [pdf] [abstract]
Abstract: Multimedia streaming is becoming ever more popular. However, the Internet does not support streaming with its high bandwidth and low latency requirements very well. The problem is that QoS guarantees cannot be given. Hence, communication partners have to deal with rapidly changing connection parameters. This requires sophisticated streaming concepts that can handle these varying conditions using adaptation techniques. Adaptation methods can be dropping layers, dropping access units or transcoding the contents. But this places specific requirements on the underlying protocol. This paper identifies and discusses these requirements and analyzes how existing protocols can meet them. Unfortunately, none of the known protocols can meet all requirements. Hence, we propose a new adaptation-aware multimedia streaming protocol that can operate as required in the given Internet environment. Furthermore, we show how this protocol can be used to carry MPEG-4 audio-visual contents.
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[43] | Klaus Leopold, Hermann Hellwagner, Michael Kropfberger, QCTVA - Quality Controlled Temporal Video Adaptation, In Proc. of SPIE (A N, ed.), NA, NA, pp. 163-174, 2003.
[bib] [pdf] [abstract]
Abstract: Multimedia streaming is becoming more and more popular. Seamless video streaming in heterogeneous networks like the Internet turns out as almost impossible due to varying network conditions - streams must be adapted to the current network QoS. Temporal scalability is one of the most reasonable adaptation techniques because it is fast and easy to perform. Today's approaches simply drop frames out of a video without spending much effort on finding an intelligent dropping behavior. This usually leads to good adaptation results in terms of bandwidth consumption but also to suboptimal video quality within the given bounds. Our approach offers analysis of video streams to achieve the qualitatively best temporal scalability. For this reason, we introduce a data structure called modification lattice which represents all frame dropping combinations within a sequence of frames. On the basis of the modification lattice, qualityestimations on frame sequences can be performed. Moreover, a heuristic for fast and efficient quality computation in a modification lattice is presented. Experimental results illustrate that temporal video adaptation based on QCTVA information leads to a better video quality compared to "usual" frame dropping approaches. Furthermore, QCTVA offers frame priority lists for videos. Based on these priorities, numerous adaptation techniques can increase their overall performance when using QCTVA.
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[42] | Harald Kosch, Hermann Hellwagner, Laszlo Böszörmenyi, eds., Euro-Par 2003, Parallel Processing, Springer Verlag, Heidelberg, pp. 1320, 2003.
[bib][url] [abstract]
Abstract: Euro-Par is the annual series of international conferences dedicated to the promotion and advancement of all aspects of parallel and distributed computing. The conference normally attracts more than 300 participants coming from universities, research centres and industry.
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[41] | Laszlo Böszörmenyi, Harald Kosch, Hermann Hellwagner, Best papers of EuroPar 2003, In Parallel Processing Letters, Springer, vol. 13, no. 4, Heidelberg, Germany, pp. 509-511, 2003.
[bib] |
[40] | Laszlo Böszörmenyi, Hermann Hellwagner, Harald Kosch, Mulugeta Libsie, Stefan Podlipnig, Metadata Driven Adaptation in the ADMITS Project, In Signal Processing - Image Communication - Special Issue on Multimedia Adaptation, Elsevier, vol. Vol. 18, no. Issue 8, Oxford, United Kingdom, pp. 749-766, 2003.
[bib][url] [abstract]
Abstract: The ADMITS project (Adaptation in Distributed Multimedia IT Systems) is building an experimental distributed multimedia system for investigations into adaptation, which we consider is an increasingly important tool for multimedia systems. A number of possible adaptation entities (server, proxy, clients, routers) are being explored, different algorithms for media, component and application-level adaptations are being implemented and evaluated, and experimental data are being derived to gain insight into when, where and how to adapt, and how individual, distributed adaptation steps interoperate and interact with each other. In this paper the "adaptation-chain" of (MPEG-conforming) metadata based adaptation is described: from the creation stage at the server side, through its usage in the network (actually in a proxy), up to the consumption at the client. The metadata are used to steer the adaptation processes. MPEG-conformant metadata, the so-called variation descriptions, are introduced; an example of a complete MPEG-7 document describing temporal scaling of an MPEG-4 video is given. The meta-database designed to store the metadata is briefly discussed. We describe how the metadata can be extracted from MPEG-4 visual elementary streams and initial results from the temporal video scaling experiment are given. We further present how the metadata can be utilized by enhanced cache replacement algorithms in a proxy server in order to realize quality-based caching; experimental results using these algorithms are also given. Finally, an adaptive query and presentation interface to the meta-.
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[39] | Peter Schojer, Laszlo Böszörmenyi, Hermann Hellwagner, An Adaptive MPEG-4 Proxy Cache, In Distributed and parallel systems: cluster and grid computing. Proceedings of International Conference on Distributed and Parallel Systems (DAPSYS 02), Linz, Austria. (Péter Kascuk, Dieter Kranzlmüller, Zsolt Németh, Jens Volkert, eds.), Kluwer Academic Publishers, Boston [u. a.], pp. 149-156, 2002.
[bib] [pdf] [abstract]
Abstract: Multimedia is gaining ever more importance on the Internet. This increases the need for intelligent and efficient video caches. Typical Web proxies were not designed to efficiently support the caching of videos. A promising approach to improve caching efficiency is to adapt videos. With the availability of MPEG-4 it is possible to develop a standard compliant proxy that allows fast and efficient adaptation. We propose a modular design for an adaptive MPEG-4 video proxy that supports efficient full and partial video caching in combination with filtering options that are driven by the terminal capabilities of the client. We use the native scalability operations provided by MPEG-4 and use the emerging MPEG-7 standard to describe the scalability options for a video. The proxy parses the MPEG-7 description and decides, based on this description and the terminal capabilities of the client, which adaptation step to choose. Simple MPEG-4 audio-visual streams are supported by filter operations in the compressed domain that realize several temporal scaling algorithms and color reduction. In this paper, we will restrict ourselves to full video caching. The combination of adaptation with MPEG-4, MPEG-7 and client terminal capabilities is to the best of our knowledge unique and will increase the quality of service for end users.
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[38] | Matthias Ohlenroth, Hermann Hellwagner, RTP Packetization of MPEG-4 Elementary Streams, In ICME Proceedings (IEEE, ed.), IEEE Xplore, NA, pp. 1-4, 2002.
[bib][url] [pdf] [abstract]
Abstract: Multimedia streaming becomes ever more popular. The multimedia standard MPEG-4 has been designed to support scenes of different levels of complexity and applications with low bandwidth requirements up to very high bandwidth requirements. One protocol suitable to transfer this kind of data over IP networks is the real-time transport protocol (RTP). This report describes standardized and proposed payload formats that support the transport of MPEG-4 elementary streams over RTP connections. These RTP packetization formats are compared w.r.t. their suitability for the adaptation (scaling) of the media data within the network, i.e., by advanced routers or proxy caches. This adaptation process is governed by metadata that need to be transferred and inspected in conjunction with the media streams.
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[37] | Hermann Hellwagner, Matthias Ohlenroth, VI Architecture Communication Features and Performance on the Giganet Cluster LAN, In Future Generation Computer Systems, Elsevier B.V., vol. Vol. 18, no. Issue 3, Amsterdam, Netherlands, pp. 421-433, 2002.
[bib][url] [doi] [pdf] [abstract]
Abstract: The virtual interface (VI) architecture standard was developed to satisfy the need for a high throughput, low latency communication system required for cluster computing. VI architecture aims to close the performance gap between the bandwidths and latencies provided by the communication hardware and visible to the application, respectively, by minimizing the software overhead on the critical path of the communication. This paper presents the results of a performance study of one VI architecture hardware implementation, the Giganet cLAN (cluster LAN). The focus of the study is to assess and compare the performance of different VI architecture data transfer modes and specific features that are available to higher-level communication software like MPI in order to aid the implementor to decide which VI architecture options to employ for various communication scenarios. Examples of such options include the use of send/receive vs. RDMA data transfers, polling vs. blocking to check completion of communication operations, multiple VIs, completion queues and scatter capabilities of VI architecture.
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[36] | Balázs Csizmazia, Hermann Hellwagner, The design and implementation of the A2QM3 System, In Proceedings Fourth International Workshop on Active Middleware Services (A N, ed.), IEEE Computer Society, Washington, DC, USA, pp. 19-27, 2002.
[bib] [pdf] [abstract]
Abstract: In this paper we present the design, architecture and implementation of the A2QM3 System. It provides programmers re-usable QoS-aware Control Objects to enable building a complete middleware for adaptive applications over active networks. We introduce the programming model, the system architecture, and show the parts that make this system a full-featured middleware supporting QoS-aware reliable stream-oriented communication, communication using the request/reply-based CORBA model and real-time streaming for continuous multimedia contents.
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[35] | Laszlo Böszörmenyi, Mario Döller, Hermann Hellwagner, Harald Kosch, Mulugeta Libsie, Peter Schojer, Comprehensive Treatment of Adaptation in Distributed Mulimedia Systems in the ADMITS Project, In Proceedings of the tenth ACM international conference on Multimedia (Juan Les Pins, ed.), ACM, New York, pp. 429-430, 2002.
[bib][url] [abstract]
Abstract: Adaptation is becoming an increasingly important tool for resource and media management in distributed multimedia systems. Best-effort scheduling and worst-case reservation of resources are two extreme cases, none of them well suited to cope with large-scale, dynamic multimedia systems. The middle course can be met by a system which dynamically adapts its data, resource requirements, and processing components to achieve user satisfaction. Nevertheless, there is no agreement about the questions, where, when, what and who should adapt. A number of papers have been published in recent years, where adaptation is a central issue, however, in most different interpretations and generally in a somehow limited scope; e.g.,[1, 2, 8, 9, 10, 12]. A distributed multimedia system comprises several types of components, such as media servers, meta-databases, proxies, routers, clients. Also, a large number of adaptation possibilities exist, from simple frame dropping up to virtual server systems which dynamically allocate new resources on demand. The main question is, which kind of component can be best used for what kind of adaptation. In the ADMITS project (Adaptation in Distributed Multimedia IT Systems), we are seeking for answers to exactly this basic question, and to a number of related questions.
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[34] | Matthias Ohlenroth, Hermann Hellwagner, Quality Adaptation Options of MPEG-4 Video Streams, Technical report, Institute of Information Technology (ITEC), Klagenfurt University, no. TR/ITEC/01/1.03., Klagenfurt, Austria, pp. 20, 2001.
[bib] |
[33] | Harald Kosch, Laszlo Böszörmenyi, Hermann Hellwagner, Modeling Quality Adaptation Capabilities of Audio-Visual Data, In Proceedings of the 12th International Conference on Database and Expert Systems Application - DEXA 2001, Munich, Germany, September 3-5, 2001 (HC Mayr, J Lazansky, G Quichmayr, P Vogel, eds.), Springer Verlag, Berlin [u. a.], pp. 744-753, 2001.
[bib] |
[32] | Hermann Hellwagner, Erich Kargl, A Cluster-Based QoS Testbed for Multimedia Communications, In SCI 2001 Proceedings of the 5th World Multi-Conference on Systemics, Cybernetics and Informatics, Volume XV, IEEE CS, July 2001 (N Callaos, W Badawy, S Bozinovski, eds.), IEEE, --, pp. 362-367, 2001.
[bib] [pdf] [abstract]
Abstract: This paper presents an inexpensive cluster-based QoS networking testbed that can be employed to \emulate" different networks for multimedia communication ex-periments. Such a network can be built using standard PC and Ethernet hardware and open-source software components, e.g., IP routing and traÆc control avail- able in recent Linux kernels as well as a Differentiated Services package built atop these building blocks. The testbed can exibly be configured to model various link bandwidths as well as IP routers capable of classifying, queuing (with various disciplines), forward-ing and/or dropping packets and shaping traÆc. The QoS components and facilities of the testbed are in-troduced and initial performance analysis experiments and results are reported. A simple video streaming application under QoS control is presented to show the usefulness of the testbed.
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[31] | Laszlo Böszörmenyi, Hermann Hellwagner, Harald Kosch, Multimedia Technologies for E-Buisness Systems and Process, In Elektronische Geschäftsprozesse: Grundlagen, Sicherheitsaspekte, Realisierungen, Anwendungen. Tagungsband zur gemeinsamen Arbeitskonferenz GI/VOI/BITKOM/OCG/TeleTrusT (Patrick Horster, ed.), it Verlag, Höhenkirchen, pp. 471-481, 2001.
[bib] |
[30] | Christian Weiß, Hermann Hellwagner, Linda Stals, Ulrich Rüde, Data Locality Optimizations to Improve The Efficiency of Multigrid Methods, In Concepts of Numerical Software, NA, NA, pp. 1-10, 2000.
[bib] [pdf] [abstract]
Abstract: Current superscalar microprocessors are able to operate at a peak performance of up to 1 GFlop/sec. However, current main memory technology does not provide the data needed fast enough to keep the CPU busy. To minimize idle times of the CPU, caches are used to speed up accesses to frequently used data. To exploit caches, the software must be aware of them and reuse data in the cache before it is being replaced. Unfortunately, all conventional multigrid codes are not cache-aware and hence exploit less than 10 percent of the peak performance of cache based machines. Our studies with linear PDEs with constant coefficients show that it is possible to speed up the execution of our multigrid method by a large factor and hence solve a Poisson’s equation with one million unknowns in less than 3 seconds. The optimized reuse of data in the cache allows us to exploit 30 percent of the peak performance of the CPU, in contrast to mgd9v for instance, which achieves less than 5 percent on the same machine. To achieve this, we used several techniques like loop unrolling and loop fusion to better exploit the memory hierarchy and the superscalar CPU. We study the effects of these techniques on the runtime performance in detail. We also study several tools which guide the optimizations and help to restructure the code.
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[29] | Hermann Hellwagner, Klaus Leopold, Ralf Schlatterbeck, Carsten Weich, Performance Tuning of Parallel Real-Time Voice Communication Software, In Proceedings Distributed and Parallel Systems (Peter Kascuk, Gabriele Kotsis, eds.), Kluwer Academic Publishers, Norwell, MA, USA, pp. 57-60, 2000.
[bib] [pdf] [abstract]
Abstract: This paper describes an unconventional way to apply a performance analysis tool for parallel programs (Vampir) to understand and tune the performance of the real-time voice and data communication software running on top of Frequentis’ V4 switch. The execution schedule of the strictly time-triggered V4 switching software is computed off-line; analyzing the schedule to identify e.g. performance bottlenecks used to be a complex and time-consuming process. We present our approach to transform the V4 software schedule’s information into Vampir trace files and use this tool’s facilities to provide a visualization of the schedule. A case study illustrates the benefits of this approach.
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[28] | Hermann Hellwagner, Markus Lachowitz, Matthias Ohlenroth, Exploring the Performance of VI Architecture Communication Features in the Giganet Cluster LAN, In Proceedings International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA´2000), June 26, 2000, Las Vegas, Vol. 5 (Hamid R Arabnia, ed.), CSREA Press, [Athens, Ga.], pp. 2615-2621, 2000.
[bib] [doi] [pdf] [abstract]
Abstract: The Virtual Interface (VI) Architecture standard was developed to satisfy the need for a high-throughput, low-latency communication system required for cluster computing. This paper presents the results of a performance study of one VI Architecture hardware implementation, the Giganet cLAN (Cluster LAN). The focus of the study is to assess and compare the performance of different VI Architecture data transfer modes and specific features that are available to higher-level communication software like MPI, in order to aid the implementor to decide which VI Architecture options to employ for various communication scenarios. Examples of such options include the use of send/receive vs. RDMA data transfers, polling vs. blocking to check completion of communication operations, multiple VIs, completion queues, and scatter capabilities of VI Architecture.
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[27] | Hermann Hellwagner, Ivan Zoraja, Vaidy Sunderam, SCIPVM: Parallel Distributed Computing on SCI Workstation Clusters, In Concurrency: Practice and Experience, N, A, vol. Vol 11, no. No 3, N, A, pp. 121-138, 1999.
[bib] [pdf] [abstract]
Abstract: Workstation and PC clusters interconnected by SCI (Scalable Coherent Interface) are very promising technologies for high performance cluster computing. Using commercial SBus to SCI interface cards and early system software and drivers, a two-workstation cluster has been constructed for initial testing and evaluation. The PVM system has been adapted to operate on this cluster using raw device access to the SCI interconnect, and preliminary communications performance tests have been carried out. Our preliminary results indicate that communications throughput in the range of 3.5 MBytes/s, and latencies Research supported by the Applied Mathematical Sciences program, Office of Basic Energy Sciences, U. S. Department of Energy, under Grant No. DE-FG05-91ER25105, the National Science Foundation, under Award Nos. ASC-9527186 and ASC-9214149, and the German Science Foundation SFB342. of 620 ¯s can be achieved on SCI clusters. These figures are significantly better (by a factor of 3 to 4) ...
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[26] | Hermann Hellwagner, Alexander Reinefeld, SCI: Scalable Coherent Interface, Springer Verlag, Berlin [u a ], pp. 490, 1999.
[bib] [abstract]
Abstract: Architecture and Software for High-Performance Compute Clusters.
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[25] | Martin Schulz, Hermann Hellwagner, Global Virtual Memory based on SCI-DSM, In Proceedings of SCI-Europe ´98 (A N, ed.), N, A, N, A, pp. 59-67, 1998.
[bib] |
[24] | Martin Schulz, Hermann Hellwagner, Extending NT Virtual Memory by SCI-based Hardware DSM, In Proceedings of 2nd USENIX Windows NT Symposium (A N, ed.), USENIX Association, Seattle, WA, USA, pp. -, 1998.
[bib] |