KEYWORDS: Video, Video processing, Internet, Data storage, Analytical research, Information technology, Web services, Unattended ground sensors, Multimedia, Environmental monitoring
Web services such as YouTube which allow the distribution of user-produced media have recently become very
popular. YouTube-like services are different from existing traditional VoD services because the service provider
has only limited control over the creation of new content. We analyze how the content distribution in YouTube
is realized and then conduct a measurement study of YouTube traffic in a large university campus network. The
analysis of the traffic shows that: (1) No strong correlation is observed between global and local popularity; (2)
neither time scale nor user population has an impact on the local popularity distribution; (3) video clips of local
interest have a high local popularity. Using our measurement data to drive trace-driven simulations, we also
demonstrate the implications of alternative distribution infrastructures on the performance of a YouTube-like
VoD service. The results of these simulations show that client-based local caching, P2P-based distribution, and
proxy caching can reduce network traffic significantly and allow faster access to video clips.
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.
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.
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.
We have designed and are implementing a research platform, NIST Switch, for experimenting with novel approaches to routing with quality of service (QoS) guarantees in an IP environment. NIST Switch is based on commodity PC hardware running freely-available operating systems. It implements quality of service through label switching over Ethernet, using proposed extensions to RSVP and differentiated services to signal QoS requests and distributed labels. In NIST Switch, the labels applied to packets have two fundamental uses in QoS traffic management: locally, labels select the characteristics of the queuing and traffic shaping measures applied to packets. In the network, labels identify the path segments over which traffic will flow. A label-switched route then consists of a 'bundle' of these sticks and brushes, chosen so as to achieve the appropriate aggregate behavior. NIST Switch routing algorithms attempt to optimize the set of path segments used, so as to maximize the number of service requests which can be met while bounding the number of labels allocated. As an experimental platform, NIST Switch is designed to be easily altered. Each of its key components are independently configurable modules which are readily replaceable.
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.
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