Several types of Content Distribution Networks are being deployed over the Internet today, based on different architectures to meet their requirements (e.g., scalability, efficiency and resiliency). Peer-to-Peer (P2P) based Content Distribution Networks are promising approaches that have several advantages. Structured P2P networks, for instance, take a proactive approach and provide efficient routing mechanisms. Nevertheless, their maintenance can increase considerably in highly dynamic P2P environments. In order to address this issue, a two-tier architecture that combines a structured overlay network with a clustering mechanism is suggested in a hybrid scheme. In this paper, we examine several sampling algorithms utilized in the aforementioned hybrid network that collect local information in order to apply a selective join procedure. The algorithms are based mostly on random walks inside the overlay network. The aim of the selective join procedure is to provide a well balanced and stable overlay infrastructure that can easily overcome the unreliable behavior of the autonomous peers that constitute the network. The sampling algorithms are evaluated using simulation experiments where several properties related to the graph structure are revealed.
The rapid increase of multimedia traffic has to be accounted for when designing IP networks. A key characteristic of multimedia traffic is that it has strict Quality of Service (QoS) requirements in a heterogeneous manner. In such a setting, scheduling by service curves is a useful method as it allows for assigning each flow exactly the service it requires. When hosting heterogeneous multimedia traffic, the utilization of packet-switched networks can be increased by using bandwidth/delay decoupled scheduling disciplines. It has been shown in previous work how optimal network service curves are obtained with them. A basic result from Network Calculus is that the network service curve is obtained by the min--plus convolution of the node service curves. We state a theorem on the min--plus convolution in this work, which simplifies the computation of the min--plus convolution of service curves. The theorem follows from the continuous ΓΔ-transform, which we develop. With this theorem, we derive the optimal service curves for the nodes along a path. Further, we show how the admission control can be improved when networks are designed based on service curves. Considering one node, reallocating the service curves leads to admitting more flows. Then we point out scenarios where sub-optimal allocation of service curves in a node can increase the number of admitted flows to the network.
The key results are accompanied by numerical examples. On a broader scale, this paper advances the research in analytically modeling packet-switched networks by pointing out novel properties and a new application of Network Calculus.
In this paper we present polishing, a novel technique to maximize the playback utility of a streamed layer-encoded video. Polishing reduces the amount of layer variations in a cached layer-encoded video before streaming it to a client if this increases the quality of the video. Polishing can also be used as a cache replacement strategy for removing the parts of layer-encoded videos on a cache that harm the quality least. This paper presents optimal algorithms for both applications and simulation results.
KEYWORDS: Video, Internet, Control systems, OSLO, Multimedia, Local area networks, Computing systems, Network architectures, Video coding, Computer programming
This paper investigates an architecture and implementation for the use of a TCP-friendly protocol in a scalable video distribution system for hierarchically encoded layered video. The design supports a variety of heterogeneous clients, because recent developments have shown that access network and client capabilities differ widely in today's Internet. The distribution system presented here consists of videos servers, proxy caches and clients that make use of a TCP-friendly rate control (TFRC) to perform congestion controlled streaming of layer encoded video. The data transfer protocol of the system is RTP compliant, yet it integrates protocol elements for congestion control with protocols elements for retransmission that is necessary for lossless transfer of contents into proxy caches. The control protocol RTSP is used to negotiate capabilities, such as support for congestion control or retransmission.
By tests performed with our experimental platform in a lab test and over the Internet, we show that congestion controlled streaming of layer encoded video through proxy caches is a valid means of supporting heterogeneous clients. We show that filtering of layers depending on a TFRC-controlled permissible bandwidth allows the preferred delivery of the most relevant layers to end-systems while additional layers can be delivered to the cache server. We experiment with uncontrolled delivery from the proxy cache to the client as well, which may result in random loss and bandwidth waste but also a higher goodput, and compare these two approaches.
We present an analysis of a new technique for the authentication of ID cardholders, based on the integration of a biometrics-based authentication system with digital watermarks. The chosen biometric authentication method is the dynamic signature verification of the ID cardholder, while we use a specific integrity watermark technique we developed, called Hologram Watermark, to embed and retrieve the off-line data onto an ID card. We take advantage of the fact, that two static biometric features (images of the user's face and signature) are already integral part of ID cards for manual verification and extent the stored biometric information by embedding on-line handwriting features of the signature as holographic watermarks in the overall image information of an ID card. Manipulation of any of the image information can be detected and will further disallow biometric verification of the forger. The Hologram Watermark technique produces content-related data using computer-generated hologram coding techniques. These data are embedded with watermarking techniques into the personal data printed on an ID card. The content-related data in this specific application are the dynamic features of the cardholder's signature. The main goal of this paper is to analyze the suitability of dynamic signature verification in combination with the Hologram Watermark technique, to facilitate automated user authentication based on information transparently embedded in ID cards.
In contrast to classical assumptions in Video on Demand (VoD) research, the main requirements for VoD in the Internet are adaptiveness, support of heterogeneity, and last not least high scalability. Hierarchically layered video encoding is particularly well suited to deal with adaptiveness and heterogeneity support for video streaming. A distributed caching architecture is key to a scalable VoD solution in the Internet. Thus, the combination of caching and layered video streaming is promising for an Internet VoD system, yet, requires thoughts about some new issues and challenges, e.g., how to keep layered transmissions TCP-friendly. In this paper, we investigate one particular of these issues: how can a TCP-friendly transmission exploit its fair share of network resources taking into account that the constrained granularity of layer encoded video inhibits an exact adaptation to actual transmission rates. We present a new technique that makes use of retransmissions of missing segments for a cached layered video to claim the fair share within a TCP-friendly session. Based on simulative experiments the potential and applicability of the technique, which we also call fair share claiming is shown. Moreover, a design for the integration of fair share claiming in streaming applications which are supported by caching is devised.
Protecting the media of the future - securing the future of the media is an essential task for our new century. Security is defined by security measures, e.g. confidentiality, integrity, authenticity, and non-repudiation. Most of these measures are using watermarking techniques and cryptographic mechanisms like cipher systems, digital signature schemes, and authentication protocols. The security of these mechanisms is mainly based on the authenticity of specific data like keys and attributes - both data must be dedicated to its owner in an authentic manner. Otherwise, the authenticity of data and of owners can not be guaranteed and subsequently, the security can not be assured. Therefore in our paper we want to focus on data and entity (owner) authentication. We introduce a general framework to protect media data by combining different existing techniques: cryptographic, watermarking and biometric approaches. As an example we describe general concepts for a content-fragile watermarking approach for digital images and a generic approach for biometric authentication.
KEYWORDS: Biometrics, Digital watermarking, Feature extraction, Databases, Tablets, Visualization, Multimedia, Statistical analysis, Data storage, Personal digital assistants
One major application domain for digital watermarks is copyright protection. Besides the design of watermarking algorithms, technologies for copyright holder identification have to be investigated. To ensure authenticity of an individual person, a wide number of biometric procedures exist. We define and describe new biometric watermarks, which denote the application of biometric reference data of individuals within digital watermarks to identify and verify ownership. Amongst the two classes of physiological and senso-motoric biometric schemes, the later appears more appropriate for biometric watermarks, as only these provide implicit expressions of intention. As such, we choose on-line handwriting as an appropriate base technology for our three new scenarios in biometric watermarking. In the first approach, embedding keys are being generated from biometric reference data, which requires stable and robust features and leads to rather complex keys. To overcome the complexity boundaries, the second approach develops a biometric reference hash, allowing key look-ups in key certifying servers. Although this proceeding leads to less complex keys, it still requires stable features. The third approach describes the embedding of biometric reference data within a watermark, allowing owner verification by more variant features, but limitations apply due to capacity of watermarking systems and also protection of the reference data is required. While most handwriting-based verification systems are limited to signature contexts, we discuss two additional context types for user authentication: passphrases and sketches.
Audio and video watermarking enable the copyright protection with owner or customer authentication and the detection of media manipulations. The available watermarking technology concentrates on single media like audio or video. But the typical multimedia stream consists of both video and audio data. Our goal is to provide a solution with robust and fragile aspects to guarantee authentication and integrity by using watermarks in combination with content information. We show two solutions for the protection of audio and video data with a combined robust and fragile watermarking approach. The first solution is to insert a time code into the data: We embed a signal as a watermark to detect gaps or changes in the flow of time. The basic idea uses numbers increasing by one. If in the verification process the next number is smaller than the last one or the step is greater than one, the time flow has been changed. This is realized without the combination of video and audio data. But we can synchronize the two data streams. A time signal is only valid if the combination of audio and video signals satisfy a certain attribute. To keep the basic example: if we embed an increasing a number in the audio and a decreasing number in the video, we could test if the combination of both always equals zero. The second solution is more complex: We use watermarks to embed information in each media about the content of the other media. With the help of speech recognition technology it is possible to embed the spoken text, the content, of an audio file in the video. With an algorithm previously developed in [1] we extract video content representation which is embedded in the audio stream. In our paper we present the problem of copyright protection and integrity checks for combined video and audio data. We show our two solutions and discuss our results.
A variety of robust non-perceptual watermarking methods have been proposed to solve the illegal copying and proof of ownership problems. Although a number of broad claims have been made in the field of robustness of various digital watermarking methods. It is still difficult to handle combined or non-linear geometric transformations. In this paper we propose the SSP approach. We use a correlation based watermark pattern approach in the spatial domain which operates on image inherent properties when selecting the marking positions: self spanning patterns (SSP). Each watermark pattern which represents one information bit of the whole watermark string is spanned over four image inherent properties like image edges or corners. These four points specify a polygon over which the watermark pattern is spanned using a polygon filling algorithm. After transformations we search for our points based on the image characteristics. Then we span our pattern over the points and check if there was a one or a zero embedded. Continuing that for all pattern positions we can build the whole watermark string. The advantage of the SSPs is that transformations need not be recognized, the marking positions and our pattern shape can be automatically found.
Internet video-on-demand (VoD) today streams videos directly from server to clients, because re-distribution is not established yet. Intranet solutions exist but are typically managed centrally. Caching may overcome these management needs, however existing web caching strategies are not applicable because they work in different conditions. We propose movie distribution by means of caching, and study the feasibility from the service providers' point of view. We introduce the combination of our reliable multicast protocol LCRTP for caching hierarchies combined with our enhancement to the patching technique for bandwidth friendly True VoD, not depending on network resource guarantees.
One major problem of using multimedia material in lecturing is the trade-off between actuality of the content and quality of the presentations. A frequent need for content refreshment exists, but high quality presentations can not be authored by the individual teacher alone at the required rate. Several past and current projects have had the goal of developing so-called learning archives, a variation of digital libraries. On demand, these deliver material with limited structure to students. For lecturing, these systems provide just as insufficient service as the unreliable WWW. Based on our system HyNoDe [HYN97] we address these issues in our distributed media server built of 'medianodes.' We add content management that addresses teachers' needs and provide guaranteed service for connected as well as disconnected operation of their presentation systems. Medianode aims at a scenario for non-real-time, shared creation and modification of presentations and presentation elements. It provides user authentication, administrative roles and authorization mechanisms. It requires an understanding of consistency, versioning and alternative content tailored to lecturing. To allow for predictable presentation quality, medianode provides application level QoS supporting alternative media and alternative presentations. Viable presentation tracks are dynamically generated based on user requests, user profiles and hardware profiles. For machines that are removed from the system according to a schedule, the systems guarantees availability of consistent, complete tracks of selected presentations at disconnect time. In this paper we present the scope of the medianode project and afterwards its architecture, following the realization steps.
In this paper we describe music retrieval in ICOR, a project of Darmstadt TU. It is the goal of ICOR to find new interfaces to support applications of music video and music CDs. Although the project consists of audio and video analysis we concentrate on a description of the audio algorithms in this paper. We describe our MPEG-7 like data structure to store meta information for music pieces and explain which algorithms we use to analyze the content of music pieces automatically. We currently use an applause detection to distinguish live music from studio recordings, a genre classifier to distinguish pieces with beats form classical music, and a singer recognition.
In this paper, we address the problem of choosing appropriate features to describe the content of still pictures or video sequences, including audio. As the computational analysis of these features is often time- consuming, it is useful to identify a minimal set allowing for an automatic classification of some class or genre. Further, it can be shown that deleting the coherence of the features characterizing some class, is not suitable to guarantee an optimal classification result. The central question of the paper is thus, which features should be selected, and how they should be weighted to optimize a classification problem.
Many video and audio sessions are transmitted via the Multicast Backbone (MBone) medium day by day. The Integrated Services architecture of the Internet will make it now possible to transmit and receive these sessions in a 'guaranteed' quality of service. To allow this in heterogeneous networks, consisting of, e.g. Ethernet and ATM, an interaction between the QoS architectures of the Internet and ATM is necessary. However, they are very different, so mapping them is a difficult task. In this paper, the implementation of an interaction approach for the QoS architectures developed for the Internet and for ATM, and the extension of the MBone VCR for recording and playing back MBone sessions in a higher quality, is described. This system allows the QoS supported recording and off-line playback of MBone session in heterogeneous IP/ATM networks.
Today's interactive television systems are using proprietary communication protocols and interchange formats. To provide inter-operability at the application level the next generation of interactive television system will be based on standardized communication protocols, monomedia and multimedia formats. This paper presents the Globally Accessible Services (GLASS) system which is a prototype interactive television system based on the Multimedia and Hypermedia Expert Group (MHEG) standard. After a brief introduction to MHEG as the multimedia interchange format between application server and set-top box in interactive television systems, the GLASS clients and servers are described, and an example scenario for navigation in the GLASS system is provided.
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