[104] | Michael Sablatschan, Michael Ransburg, Hermann Hellwagner, Towards an Improved SVC-to-AVC Rewriter, In Proceedings of the Second International Conferences on Advances in Multimedia (MMEDIA 2010) (Laszlo Böszörmenyi, Dumitru Burdescu, Philip Davis, Peter Stanchev, eds.), IEEE, Los Alamitos, CA, USA, pp. 18-21, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: The Scalable Video Coding (SVC) extension of the H.264/AVC (AVC) video coding standard features spatial, quality and temporal scalability. Backwards compatibility with legacy decoding devices is maintained through an H.264/AVC compliant base layer, which represents the lowest quality of an SVC bit-stream. However, it is often desirable to also provide the higher quality layers to legacy H.264/AVC devices. This is achieved by a process commonly known as “bit-stream rewriting”, which allows for an efficient SVC to AVC conversion by exploiting the similarities of the two codecs. This paper introduces an improved version of the existing JSVM reference software rewriter (JSVM-rewriter). The improvements include a better run-time performance through parallel processing, as well as applicability in streaming scenarios. A detailed evaluation provides performance measurements for the improved rewriter and compares it to the existing JSVM-rewriter. The evaluation shows that notable performance improvements can be achieved using the presented approach. The paper concludes on how the rewriter could be further improved.
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[103] | Michael Ransburg, Mario Jonke, Hermann Hellwagner, An Evaluation of Mobile End Devices in Multimedia Streaming Scenarios, In Proceedings of the First Workshop on Mobile Multimedia Networking (IWMMN 2010) (Honggang Wang, Jinchun Xia, eds.), Springer, Heidelberg/Berlin, Germany, pp. 14, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: This paper compares handhelds based on the iPhone and Android operating systems in multimedia streaming scenarios. We simulate typical Internet network impairments, i.e. packet delay and packet loss, and evaluate their effects on the end devices. Additional evaluations include bandwidth overhead in icted by the different streaming approaches and traffic shape and fairness when both handhelds consume media simultaneously. Based on the quantitative evaluation, both approaches show weaknesses and strengths. A final qualitative discussion points out additional advantages for the streaming approach implemented in the iPhone operating system.
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[102] | Jordi Ortiz Murillo, Michael Ransburg, Eduardo Martínez Graciá, Michael Sablatschan, Antonio Gómez Skarmeta, Hermann Hellwagner, Towards User-driven Adaptation of H.264/SVC Streams, In Proceedings of the Workshop on Quality of Experience for Multimedia Content Sharing (QoEMCS 2010) (Shelley Buchinger, Rui Jorge Lopes, Satu Jumisko-Pyykkö, Hans-Jürgen Zepernick, eds.), Tampere University of Technology, Tampere, Finland, pp. 4, 2010.
[bib][url] [pdf] [abstract]
Abstract: H.264/SVC enables runtime-efficient scalability in the spatial, temporal and fidelity dimension. Existing adaptation mechanisms facilitate this to automatically adapt the H.264/ SVC stream to the current usage environment without any user interaction. This paper argues that the Quality of Experience (QoE) of the end user can be enhanced by enabling him to manually adjust the adaptation if he wishes to do so. An approach which enables this is presented and evaluated. It is shown that by facilitating this approach an increased QoE is provided compared to automatic adaptation approaches. Finally, future work indicates the next steps in order to implement this approach.
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[101] | Robert Kuschnig, Ingo Kofler, Hermann Hellwagner, An Evaluation of TCP-based Rate-control Algorithms for Adaptive Internet Streaming of H.264/SVC, In Proceedings of the First Annual ACM SIGMM Conference on Multimedia Systems (MMSys) (Wu-chi Feng, Ketan Mayer-Patel, eds.), ACM, New York, NY, USA, pp. 157-168, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: Recent work in TCP video streaming indicates that multimedia streaming via TCP provides satisfactory performance when the achievable TCP throughput is approximately twice the media bit rate. However, these conditions may not be achievable on the Internet, e.g., when the delivery path offers insufficient bandwidth or becomes congested due to competing traffic. Therefore, adaptive streaming for videos over TCP is required and a number of rate-control algorithms for video streaming have been proposed and evaluated in the literature. In this paper, we evaluate and compare three existing rate-control algorithms for TCP streaming in terms of the (PSNR) quality of the delivered video and in terms of the timeliness of delivery. The contribution of the paper is that, to the best of our knowledge, this is the first evaluation of TCP-based streaming in an Internet-like setting making use of the scalability features of the H.264/SVC video codec. Two simple bandwidth estimation algorithms and a priority-/deadline-driven approach are described to adapt the bit rates of, and transmit, the H.264/SVC video in a rate-distortion optimal manner. The results indicate that the three algorithms perform robustly in terms of video quality and timely delivery, both on under-provisioned links and in case of competing TCP flows. The priority-/deadline-driven technique is even more stable in terms of packet delays and jitter; thus, client buffers can be dimensioned more easily.
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[100] | Robert Kuschnig, Ingo Kofler, Hermann Hellwagner, Improving Internet Video Streaming Performance by Parallel TCP-Based Request-Response Streams, In Proceedings of the 7th IEEE Consumer Communications and Networking Conference (CCNC) (Sergey Balandin, Marcin Matuszewksi, Jörg Ott, eds.), IEEE, Los Alamitos, CA, USA, pp. 5, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: TCP-based video streaming encounters difficulties in unreliable networks with unanticipated packet loss. In combination with high round trip times, the effective throughput deteriorates rapidly and TCP connection resets or stalls may occur. In this paper, we propose a client-driven video transmission scheme which utilizes multiple HTTP/TCP streams. The scheme is largely insensitive to unanticipated packet loss and thereby reduces throughput fluctuations. Since it is based on HTTP, the scheme can easily be deployed in existing network infrastructures. It fosters scalability on the server side by shifting complexity from the server to the clients. Certain features of request-response schemes allow maintaining fairness, despite of using multiple HTTP streams. Making use of TCP, the scheme inherently adapts to congested network links.
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[99] | Michael Eberhard, Tibor Szkaliczki, Hermann Hellwagner, László Szobonya, Christian Timmerer, Knapsack Problem-based Piece-Picking Algorithms for Layered Content in Peer-to-Peer Networks, In Proceedings of the 2010 ACM Workshop on Advanced Video Streaming Techniques for Peer-to-Peer Networks and Social Networking (Gabriella Olmo, Christian Timmerer, Pascal Frossard, Keith Mitchell, eds.), ACM, New York, NY, USA, pp. 71-76, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: The distribution of layered content over peer-to-peer networks becomes more important today as the users are consuming the content on terminals with various display capabilities and different network connections. For single-layer content distribution, the piece-picking algorithm only needs to ensure that content pieces are downloaded in time for display. When layered content is distributed over a peer-to-peer network, the piece-picking algorithm needs to be modified to ensure that the best possible quality is displayed while all desired pieces still have to be received before their deadline expires. In this paper, the piece-picking problem for layered content is analyzed and a number of piece-picking algorithms for layered content based on the solutions for the knapsack problem are presented. Furthermore, an evaluation of these algorithms is performed and possible applications are discussed.
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[98] | Nicola Capovilla, Michael Eberhard, Silvano Mignanti, Riccardo Petrocco, Janne Vehkaperä, An Architecture for Distributing Scalable Content over Peer-to-Peer Networks, In Proceedings of the Second International Conferences on Advances in Multimedia (MMEDIA 2010) (Laszlo Böszörmenyi, Dumitru Burdescu, Philip Davis, Peter Stanchev, eds.), IEEE, Los Alamitos, CA, USA, pp. 1-6, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: Peer-to-Peer systems are nowadays a very popular solution for multimedia distribution, as they provide significant cost benefits compared with traditional server-client distribution. Additionally, the distribution of scalable content enables the consumption of the content in a quality suited for the available bandwidth and the capabilities of the end-user devices. Thus, the distribution of scalable content over Peer-to-Peer networks is a very actual research topic. This paper presents an architecture for the distribution of scalable content in a fully distributed Peer-to-Peer network. The architectural description includes how the scalable layers of the content are mapped to the pieces distributed in the Peer-to-Peer system and detailed descriptions of the producer- and consumer-site architecture of the system. The presented system is to our knowledge the first open-source Peer-to-Peer network with full Scalable Video Coding support.
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[97] | Eugen Borcoci, Daniel Negru, Christian Timmerer, A Novel Architecture for Multimedia Distribution based on Content-Aware Networking, In Proceedings of the 3rd International Conference on Communication Theory, Reliability, and Quality of Service (CTRQ 2010) (Shingo Ata, Eugen Borcoci, Javier Del Ser Lorente, Michel Diaz, Michal Pioro, Joel Rodrigues, Zary Segall, eds.), IEEE, Los Alamitos, CA, USA, pp. 162-168, 2010.
[bib][url] [doi] [pdf] [abstract]
Abstract: This paper proposes a novel virtual Content-Aware Network (CAN) layer as a part of a full layered architecture, focused, but not limited to, on multimedia distribution with Quality of Services (QoS) assurance. The overall system is based on a flexible cooperation between providers, operators and end-users, enabling users to access the offered multimedia services in various contexts and also to become private content providers. The paper introduces the main concepts and architecture for the main virtual network layer (i.e., CAN), exposing its role and interfaces among overall system layers. This work is a part of the starting effort inside of a new European FP7 ICT research project, ALICANTE.
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[96] | Markus Waltl, Christian Timmerer, Hermann Hellwagner, A Test-Bed for Quality of Multimedia Experience Evaluation of Sensory Effects, In Proceedings of the First International Workshop on Quality of Multimedia Experience (QoMEX 2009) (Touradj Ebrahim, Khaled El-Maleh, Gokce Dane, Lina Karam, eds.), IEEE, Los Alamitos, CA, USA, pp. 145-150, 2009.
[bib][url] [doi] [pdf] [abstract]
Abstract: This paper introduces a prototype test-bed for triggering sensory effects like light, wind, or vibration when presenting audiovisual resources, e.g., a video, to users. The ISO/IEC MPEG is currently standardizing the Sensory Effect Description Language (SEDL) for describing such effects. This language is briefly described in the paper and the testbed that is destined to evaluate the quality of the multimedia experience of users is presented. It consists of a video annotation tool for sensory effects, a corresponding simulation tool, and a real test system. Initial experiments and results on determining the color of light effects from the video content are reported.
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[95] | Christian Timmerer, Jean Gelissen, Markus Waltl, Hermann Hellwagner, Interfacing with Virtual Worlds, In Proceedings of the 2009 NEM Summit (Halid Hrasnica, ed.), Eurescom – the European Institute for Research and Strategic Studies in Telecommunications – GmbH, Heidelberg, pp. 118-123, 2009.
[bib][url] [pdf] [abstract]
Abstract: Virtual worlds (often referred to as 3D3C for 3D visualization & navigation and the 3C’s of Community, Creation and Commerce) integrate existing and emerging (media) technologies (e.g. instant messaging, video, 3D, VR, AI, chat, voice, etc.) that allow for the support of existing and the development of new kinds of networked services. The emergence of virtual worlds as platforms for networked services is recognized by businesses as an important enabler as it offers the power to reshape the way companies interact with their environments (markets, customers, suppliers, creators, stakeholders, etc.) in a fashion comparable to the Internet and to allow for the development of new (breakthrough) business models, services, applications and devices. Each virtual world however has a different culture and audience making use of these specific worlds for a variety of reasons. These differences in existing Metaverses permit users to have unique experiences. In order to bridge these differences in existing and emerging Metaverses a standardized framework is required, i.e., MPEG-V Media Context and Control (ISO/IEC 23005), that will provide a lower entry level to (multiple) virtual worlds both for the provider of goods and services as well as the user. The aim of this paper is to provide an overview of MPEG-V and its intended standardization areas. Additionally, a review about MPEG-V’s most advanced part – Sensory Information – is given.
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[94] | Christian Timmerer, Johannes Jaborning, Hermann Hellwagner, A Comparison and Mapping Model, In Proceedings of the 9th Workshop on Multimedia Metadata (WMM'09) (Ralf Klamma, Romulus Grigoras, Vincent Charvillat, Harald Kosch, eds.), http://ceur-ws.org, Aachen, Germany, pp. 18, 2009.
[bib][url] [pdf] [abstract]
Abstract: Nowadays, mobile devices have implemented several transmission technologies which enable access to the Internet and increase the bit rate for data exchange. Despite modern mobile processors and high-resolution displays, mobile devices will never reach the stage of a powerful notebook or desktop system (for example, due to the fact of battery powered CPUs or just concerning the smallsized displays). Due to these limitations, the deliverable content for these devices should be adapted based on their capabilities including a variety of aspects (e.g., from terminal to network characteristics). These capabilities should be described in an interoperable way. In practice, however, there are many standards available and a common mapping model between these standards is not in place. Therefore, in this paper we describe such a mapping model and its implementation aspects. In particular, we focus on the whole delivery context (i.e., terminal capabilities, network characteristics, user preferences, etc.) and investigated the two most prominent state-of-the-art description schemes, namely User Agent Profile (UAProf) and Usage Environment Description (UED).
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[93] | Bernhard Reiterer, Cyril Concolato, Hermann Hellwagner, Natural-Language-based Conversion of Images to Mobile Multimedia Experiences, In Proceedings of 1st International ICST Conference on User Centric Media - UCMedia 2009 (Patros Daras, Imrich Chlamtac, eds.), Springer, Berlin, Heidelberg, New York, pp. 4 - CD, 2009.
[bib][url] [abstract]
Abstract: We describe an approach for viewing any large, detail-rich picture on a small display by generating a video from the image, as taken by a virtual camera moving across it at varying distance. Our main innovation is the ability to build the virtual camera's motion from a textual description of a picture, e.g., a museum caption, so that relevance and ordering of image regions are determined by co-analyzing image annotations and natural language text. Furthermore, our system arranges the resulting presentation such that it is synchronized with an audio track generated from the text by use of a text-to-speech system.
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[92] | Bernhard Reiterer, Hermann Hellwagner, Animated Picture Presentation Steered by Natural Language, In Proceedings International InterMedia Summer School 2009 (Magnenat-Thalmann Nadia, Han Seunghyun, Potopsaltou Dimitris, eds.), MIRALab at University of Geneva, Geneva, pp. 24-32, 2009.
[bib][url] [abstract]
Abstract: In this paper, we present an approach for presenting large, feature-rich pictures on small displays by generating an animation and subsequently a video from the image, as it could be taken by a virtual camera moving across the image. Our main innovation is the ability to build the virtual camera's motion upon a textual description of a picture, as from a museum caption, so that relevance and ordering of image regions is determined by co-analyzing image annotations and text. Furthermore, our system can arrange the resulting presentation in a way that it is synchronized with an audio track generated from the text by use of a text-to-speech system.
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[91] | Bernhard Reiterer, Janine Lachner, Andreas Lorenz, Andreas Zimmermann, Hermann Hellwagner, Research Directions Toward User-centric Multimedia, In Advances in Semantic Media Adaptation and Personalization (Marios C Angelides, Phivos Mylonas, Manolis Wallace, eds.), Auerbach Publications, Boca Raton (Florida), pp. 21-42, 2009.
[bib][url] [doi] [abstract]
Abstract: Currently, much research aims at coping with the shortcomings in multimedia consumption that may exist in a user's current context, e.g., due to the absence of appropriate devices at many locations, a lack of capabilities of mobile devices, restricted access to content, or non-personalized user interfaces. Recently, solutions to specific problems have been emerging, e.g., wireless access to multimedia repositories over standardized interfaces; however, due to usability restrictions the user has to spend much effort to or is even incapable of fulfilling his/her demands. The vision of user-centric multimedia places the user in the center of multimedia services to support his/her multimedia consumption intelligently, dealing with the aforementioned issues while minimizing required work. Essential features of such a vision are comprehensive context awareness, personalized user interfaces, and multimedia content adaptation. These aspects are addressed in this paper as major challenges toward a user-centric multimedia framework.
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[90] | Ingo Kofler, Robert Kuschnig, Hermann Hellwagner, Improving IPTV Services by H.264/SVC Adaptation and Traffic Control, In Proceedings of the IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB) (Pablo Angueira, Ulrich Reimers, eds.), IEEE, Los Alamitos, CA, USA, pp. 1-6, 2009.
[bib][url] [doi] [abstract]
Abstract: This paper presents a novel approach that combines both in-network, application-layer adaptation and network-layer traffic control of scalable video streams based on the H.264/SVC standard. In the IPTV/VoD scenario considered, an intercepting RTSP/RTP proxy performs admission control of the requested video, based on the signaled scalability information, and decides whether the content can be streamed without changes or in an adapted version. The proxy configures the network layer appropriately in order to separate the video stream from besteffort traffic on the same link. Rather than performing fixed bandwidth allocation, our proxy approach uses the Hierarchical Token Bucket (HTB) queuing discipline to allow for borrowing bandwidth between traffic classes. In that setting, two different allocation policies are introduced. The Hard Reservation Policy (HRP) performs admission control and adaptation on the video streams and does not modify video bandwidth allocation after admission. In contrast, the Flexible Borrowing Policy (FBP) restricts the admission control to the base layer of the SVC stream. The packets carrying MGS enhancement layer data are marked with priorities by the proxy and are handled at the network layer by a priority-based queuing mechanism. Both a qualitative comparison and an experimental evaluation of the two policies are given.
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[89] | Ingo Kofler, Robert Kuschnig, Hermann Hellwagner, In-Network Real-Time Adaptation of Scalable Video Content on a WiFi-ne Router, In Proceedings of the 6th IEEE Consumer Communications and Networking Conference (CCNC) (Simon Gibbs, Alan Messer, eds.), IEEE, Los Alamitos, CA, USA, pp. 2, 2009.
[bib] [doi] [pdf] [abstract]
Abstract: One of the most active research topics in the field of video signal processing is scalable video coding (SVC). The recently published extension of the H.264/AVC video coding standard introduces scalability features by employing a layered encoding of the video stream. In our work we investigated the usage of this scalable extension of H.264/AVC for in-network multimedia adaptation. We developed an RTSP/RTP-based proxy which exploits the layered encoding of the video and can perform real-time video adaptation on an inexpensive off-the-shelf WiFi router. This is achieved by applying a stateful, packet-based adaptation approach that keeps the computational costs at a minimum. With that approach it is possible to simultaneously adapt multiple video streams to varying network conditions or to the capabilities of the consumers' end-devices. In our demonstration we show the streaming of two scalable video streams from a server to a client and the in-network adaptation of the video at the WiFi router. The adaptation can be controlled interactively in the temporal, spatial and SNR domains.
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[88] | Alois Ferscha, Hermann Hellwagner, Christa Neuper, Wolfgang Pree, Zukunft der Informatik, In Informatik macht Zukunft - Zukunft macht Informatik (Gerhard Chroust, Hans-Peter Moessenboeck, eds.), Oesterreichische Computer Gesellschaft, Wien, pp. 48-51, 2009.
[bib] |
[87] | Michael Eberhard, Christian Timmerer, Hermann Hellwagner, A Layered Piece-Picking Algorithm for Peer-to-Peer Networks, In STreaming Day ’09 Proceedings (Marko Raggio, Fabrizio Rovati, eds.), NA, NA, pp. n.a., 2009.
[bib] [abstract]
Abstract: The streaming of multimedia content over Peer-to-Peer (P2P) networks is nowadays a well appreciated concept, as it helps distributing content to a great number of users and additionally reduces the server costs for providing the content. As the users of P2P networks often have different bandwidth connections and terminals, the same content is usually provided in different qualities. Although such a provision of the same content in different qualities helps to satisfy all users, it makes the sharing process less efficient. Users that are interested in the content in a specific quality can only exchange pieces with those users that are interested in the same content and the same quality. Thus, layered video coding, which provides different qualities within one bitstream, is especially well suited for P2P distribution. If the layered content is provided once in the best quality, all peers interested in this content can at least exchange the base layer, plus the enhancement layers they are interested in with those peers that have them available.
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[86] | Christian Timmerer, Michael Ransburg, Ingo Kofler, Hermann Hellwagner, Pedro Souto, Maria Andrade, Pedro Carvalho, Helder Castro, Mamadou Sidibe, Ahmed Mehaoua, Li Fang, Adam Lindsay, Michael Mackay, Artur Lugmayr, Bernhard Feiten, An Integrated Management Supervisor for End-to-End Management of Heterogeneous Contents, Networks, and Terminals enabling Quality of Service, In Proceedings of the 2nd European Symposium on Mobile Media Delivery (EUMOB) (Tapio Frantti, Jyrki Huusko, eds.), ACM, New York, NY, USA, pp. 6, 2008.
[bib] [pdf] [abstract]
Abstract: End-to-end support for Quality of Service (QoS) has been broadly discussed in the literature. Many technologies have been proposed, each focusing on specific aspects for providing QoS guarantees to the end user. However, the integrated management of the end-to-end chain preserving QoS in heterogeneous environments is still a significant issue and insufficiently addressed to date. In this paper we propose an integrated management supervisor that takes into account the requirements from all stakeholders along the multimedia content delivery chain and provides an end-to-end management solution enabling QoS to the end user. This architecture and the subsystems that can be distributed along the end-to-end chain are detailed in this paper.
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[85] | Christian Timmerer, Maria Teresa Andrade, Pedro Carvalho, Davide Rogai, Giovanni Cordara, The Semantics of MPEG-21 Digital Items Revisited, In Proceedings of ACM Multimedia 2008 2nd International Workshop on the Many Faces of Multimedia Semantics (Farshad Fotouhi, William I Grosky, Peter Stanchev, eds.), ACM, New York, USA, pp. 17-23, 2008.
[bib] [doi] [pdf] [abstract]
Abstract: The MPEG-21 standard forms a comprehensive multimedia framework covering the entire multimedia distribution chain. In particular, it provides a flexible approach to represent, process, and transact complex multimedia objects which are referred to as Digital Items (DIs). DIs can be quite generic, independent of the application domain, and can encompass a diversity of media resources and metadata. This flexibility has an impact on the level of interoperability between systems and applications, since not all the functionality needs to be implemented. Furthermore, additional semantic rules may be implemented through the processing of the Digital Item which is possibly driven by proprietary metadata. This jeopardizes interoperability and consequently raises barriers to the successful achievement of augmented and transparent use of multimedia resources. In this context, we have investigated and evaluated the interoperability at the semantic level of Digital Items throughout the automated production, delivery and consumption of complex multimedia resources in heterogeneous environments. This paper describes the studies conducted, the experiments performed, and the conclusions reached towards that goal.
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[84] | Michael Ransburg, Hubert Gressl, Hermann Hellwagner, Efficient Transformation of MPEG-21 Metadata for Codec-agnostic Adaptation in Real-time Streaming Scenarios, In 2008 Ninth International Workshop on Image Analysis for Multimedia Interactive Services (Hermann Hellwagner, Christian Timmerer, eds.), IEEE, Los Alamitos, CA, USA, pp. 143-146, 2008.
[bib][url] [pdf] [abstract]
Abstract: Scalable media contents, such as the new MPEG-4 Scalable Video Codec enable to easily retrieve different qualities of the media content by simply disregarding certain media segments. The MPEG-21-based codec-agnostic adaptation approach supports this concept by introducing an XMLbased Bitstream Syntax Description (BSD) which describes the different segments of a media content. Based on this BSD, an adaptation node can intelligently adapt any scalable media (i.e., remove specific media segments) without the need for codec-specific knowledge. The adaptation approach consists of 1) transforming this BSD and 2) adapting the media based on the transformed BSD. In this paper, we focus on the BSD transformation step and evaluate different mechanisms w.r.t. their transformation efficiency given several application scenarios. In particular, we compare the traditional stylesheet-based mechanisms with a novel mechanism based on regular expressions. We discuss both mechanisms in terms of their expressiveness, and propose how to actually employ regular expressions for codec-agnostic adaptation. Finally, we quantitatively evaluate these mechanisms in different adaptation scenarios, which vary in the size and number of required BSD units
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[83] | Michael Ransburg, Christian Timmerer, Hermann Hellwagner, Dynamic and Distributed Multimedia Content Adaptation based on the MPEG-21 Multimedia Framework, In Multimedia Semantics: The role of Metadata (Mathias Lux, Michael Granitzer, Marc Spaniol, eds.), Springer, Berlin, Heidelberg, New York, pp. 3-24, 2008.
[bib] [doi] [abstract]
Abstract: Today, there are many technologies in place to establish an infrastructure for the delivery and consumption of multimedia content. In practice, however, several elements of such an infrastructure are often stand-alone systems and a big picture of how these elements relate to each other or even fit together is not available. Therefore, MPEG-21 aims to provide an open framework for interoperable multimedia delivery and consumption. This requirement for interoperability results in a great diversity of XML-based metadata, which describes the media data on semantic or syntactic levels, in order to make it more accessible to the user. This metadata can be of considerable size, which leads to problems in streaming scenarios. Other than media data, XML metadata has no concept of samples, thus inhibiting streamed (and timed) processing, which is natural for media data. In order to address the challenges and requirements resulting from this situation, the concept of streaming instructions is introduced. These streaming instructions facilitate the fragmentation of content-related metadata, the association of media and metadata fragments with each other, and the synchronized streaming and processing of those fragments. Based on these capabilities, a dynamic and distributed multimedia content adaptation framework can be built.
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[82] | Markus Quaritsch, Emil Stojanovski, Christian Bettstetter, Gerhard Friedrich, Hermann Hellwagner, Bernhard Rinner, Michael Hofbaur, Mubarak Shah, Collaborative Microdrones: Applications and Research Challenges, In Proceedings of the Second International Conference on Autonomic Computing and Communication Systems (ACM, ed.), ACM Press, New York, NY, USA, pp. 7, 2008.
[bib][url] [pdf] [abstract]
Abstract: Microdrones are small-scale unmanned aerial vehicles (UAVs) carrying payloads such as cameras and sensors. Such microdrones enable us to obtain a bird's eye view of the environment which is helpful in many applications such as environmental monitoring, surveillance or disaster management. This position paper reports on our recently launched project \collaborative microdrones" where we are developing a system for aerial imaging based on cooperating, wireless networked microdrones that can be used in disaster management applications. Several microdrones will y in formation over the area of interest and deliver sensor data which is fused, analyzed and delivered to the user in real-time. In this paper we brie y discuss applications for UAVs, present related projects, introduce our research focus and report on preliminary results.
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[81] | Martin Prangl, Ingo Kofler, Hermann Hellwagner, Towards QoS Improvements of TCP-based Media Delivery, In Proceedings of the 4th International Conference on Networking and Services (ICNS) (Jun Bi, Kim Chin, Cosmin Dini, Leo Lehmann, David C Pheanis, eds.), IEEE, Los Alamitos, CA, USA, pp. 188-193, 2008.
[bib] [doi] [pdf] [abstract]
Abstract: The amount of audiovisual data available on the Internet and thus of multimedia communication over today's networks is increasing at a rapid pace. Despite the availability of specific media transport protocols like RTP, most content providers make use of the well-established and reliable TCP protocol to deliver audiovisual content over the Internet. The reason is that TCP-based data delivery in general is much less complicated for the clients to be served and over today's networks traversed (including proxies and firewalls), than making use of UDP-based RTP connections. However, in case of network bandwidth fluctuations and packet losses, TCP-based media delivery may lead to annoying jerky playback at the client side, due to retransmissions and late arrival of media data. This papers deals with TCP-based perceptual QoS improvement mechanisms for increasing the media experience for the consumer under unstable network conditions. Our approach is based on media content adaptation (transcoding) to fit the actual network bandwidth continuously monitored by the sender. The proposed mechanisms are applied at the application level at the server side, leaving the existing TCP implementation untouched and therefore enabling transparent use of existing media players. An evaluation of a realistic use case is presented which underlines the efficency of our approach.
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[80] | Martin Prangl, Ingo Kofler, Hermann Hellwagner, An MPEG-21-driven Utility-based Multimedia Adaptation Decision Taking Web Service, In Proceedings of the 1st International Conference on Ambient Media and Systems (Ambi-sys) (Roger M Whitaker, Ben Liang, eds.), ICST, Brussels, Belgium, pp. 8, 2008.
[bib] [pdf] [abstract]
Abstract: Supporting transparent delivery and convenient use of multimedia content across a wide range of networks and devices is still a challenging task within the multimedia research community; Universal Multimedia Access (UMA) is a vision that has been pursued for quite some time. In multimedia frameworks, content adaptation is the core concept to make progress toward this goal. Most media adaptation engines targeting UMA scale the content w.r.t. terminal capabilities and network resource constraints and do not sufficiently consider end user preferences or even the utility of the adapted content for the user. Based on our previous work and the support of the MPEG-21 framework, we present a transparent solution to provide a content utility-aware adaptation decision for such utility-unaware multimedia frameworks. The idea is to outsource the challenging utility-aware adaptation decision taking task, which takes many factors into consideration and leads to a complex optimization problem. A realistic use case is adopted to show how related external multimedia frameworks can easily integrate and use our proposed adaptation decision taking Web Service.
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