Proxies are emerging as an important way to reduce user-perceived latency and network resource requirements in the Internet. While relaying traffic between servers and clients, a proxy can cache resources in the hope of satisfying future client requests directly at the proxy. However, existing techniques for caching text and images are not appropriate for the rapidly growing number of continuous media streams. In addition, high latency and loss rates in the Internet make it difficult to stream audio and video without introducing a large playback delay. To address these problems, we propose that, instead of caching entire audio or video streams (which may be quite large), the proxy should store a prefix consisting of the initial frames of each clip. Upon receiving a request for the stream, the proxy immediately initiates transmission to the client, while simultaneously requesting the remaining frames from the server. In addition to hiding the latency between the server and the proxy, st...

The efficient distribution of stored information has become a major concern in the Internet which has increasingly become a vehicle for the transport of stored video. Because of the highly heterogeneous access to the Internet, researchers and engineers have argued for layered encoded video. In this paper, we investigate delivering layered encoded video using caches. Based on the stochastic knapsack theory, we develop a model for the layered video caching problem. We propose heuristics to determine which videos and which layers in the videos should be cached in order to maximize the revenue from the streaming service. We evaluate the performance of our heuristics through extensive numerical experiments. We find that, for typical scenarios, the revenue increases nearly logarithmically with the cache size and linearly with the link bandwidth that connects the cache to the origin servers. We also consider service models with request queuing and negotiations about the delivered stream quality and find that both extensions provide only small revenue increases.

Proxy caching has been used to speed up web browsing and reduce networking costs. In this paper we study the extension of proxy caching techniques to streaming video applications. A trivial extension consists of storing complete video sequences in the cache. However this may not be applicable in situations where the video objects are very large and proxy cache space is limited. We will show that the approaches proposed in this paper (referred to as selective caching), where only a few frames are cached, can also contribute to significant improvements in the overall performance. In particular we will discuss two network environments for streaming video, namely, Quality-of-Service (QoS) networks and best-effort networks (Internet). For QoS networks, the video caching goal is to reduce the network bandwidth costs; for best-effort networks, the goal is to increase the robustness of continuous playback against poor network conditions (such as congestion, delay and loss). Two different selective caching algorithms (SCQ and SCB) are proposed, one for each network scenario, to increase the relevant overall performance metric in each cases, while requiring only a fraction of the video stream to be cached. The main contribution of our work is to provide algorithms that are efficient even when the buffer memory available at the client is limited. These algorithms are also scalable so that when changes in the environment occur it is possible, with low complexity, to modify the allocation of cache space to different video sequences.

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ideo delivery from a server to a client across a network is an important component of many multimedia applications. While delivering a video stream across a resource constrained network, loss of frames may be unavoidable. Under such circumstances, it is desirable to find a server transmission schedule that can efficiently utilize the network resources while maximizing the perceived quality-of-service (QoS) at the client. To address this issue, in this paper we introduce the notion of selective frame discard at the server and formulate the optimal selective frame discard problem using a QoS-based cost function. Given network bandwidth and client buffer constraints, we develop an OðN log NÞ algorithm to find the minimum number of frames that must be discarded in order to meet these constraints. The correctness of the algorithm is also formally established. We present a dynamic programming based algorithm for solving the problem of optimal selective frame discard. Since the computational complexity of the optimal algorithm is prohibitively high in general, we also develop several efficient heuristic algorithms for selective frame discard. These algorithms are evaluated using JPEG and MPEG video traces.

Bandwidth smoothing techniques for stored video perform end-end workahead transmission of frames from the video source into the destination client video playback buffer in advance of their display times, and are very effective in reducing the bursty transmission bandwidth requirements of compressed, stored video. This paper addresses online bandwidth smoothing for a growing number of streaming video applications such as newscasts, sportscasts and distance learning, where many clients may be willing to tolerate a playback delay of a few seconds in exchange for a smaller bandwidth requirement. The smoothing can be performed at either the end-point source of the videocast or at special smoothing server(s) (e.g., proxies or gateways) within the network. A key difference with smoothing stored video at the source is that, in the online situation, the smoothing server has limited knowledge of frame sizes and access to only a segment of the video at a time. This is either because the feed is live or because it is streaming past the server. We derive an online smoothing model which incorporates playback delay, client and server buffer sizes, server processing capacity, and frame-size prediction techniques. Our model can accomodate an arbitrary arrival process. Using techniques for smoothing stored video at the source as a starting point, we develop an online, window-based smoothing algorithm for these delay-tolerant applications. Extensive experiments with MPEG-1 and M-JPEG

Abstract—Due to the high bandwidth requirement and rate vari-ability of compressed video, delivering video across wide area net-works (WANs) is a challenging issue. Proxy servers have been used to reduce network congestion and improve client access time on the Internet by caching passing data. In this paper, we investigate ways to store or stage partial video in proxy servers to reduce the net-work bandwidth requirement over WAN. A client needs to access a portion of the video from a proxy server over a local area network (LAN) and the rest from a central server across a WAN. Therefore, client buffer requirement and video synchronization are to be con-sidered. We study the tradeoffs between client buffer, storage re-quirement on the proxy server, and bandwidth requirement over WAN. Given a video delivery rate for the WAN, we propose several frame staging selection algorithms to determine the video frames to be stored in the proxy server. A scheme called chunk algorithm, which partitions a video into different segments (chunks of frames) with alternating chunks stored in the proxy server, is shown to offer the best tradeoff. We also investigate an efficient way to uti-lize client buffer when the combination of video streams from WAN and LAN is considered. Index Terms—Video proxy server, video streaming. I.

A feedback-based Internet video transmission scheme based on the ITU-T H.263+ is presented. The proposed system is capable of continually accommodating its stream size and managing the packet loss recovery in response to network condition changes. It consists of multiple components: TCP-friendly end-to-end congestion control and available bandwidth estimation, encoding frame-rate control and delay-based smoothing at the sender, media-aware packetization and packet loss recovery tied with congestion control, and quality recovery tools such as motion-compensated frame interpolation at the receiver. These components are designed to meet the low computational complexity requirement so that the whole system can operate in real-time. Among these, the video-aware congestion control known as receiver-based congestion control mechanism (RCCM), the variable frame-rate H.263+ encoding, and fast motion-compensated frame interpolation (FMCI) components are key features. Through a seamless integration, it is demonstrated that network adaptivity is enhanced enough to mitigate the packet loss and bandwidth fluctuation, resulting in a more smooth video experience at the receiver. Keywords Internet video streaming, TCP-friendliness, end-to-end congestion control, variable frame-rate encoding, and frame interpolation post-processing. 1 Corresponding author (Tel: 213-740-0157, Fax: 213-740-4651, E-mail: jongwon@sipi.usc.edu) * JongWon Kim, Young-Gook Kim, and C.-C. Jay Kuo are with the Integrated Media Systems Center and Department of Electrical Engineering-Systems, University of Southern California, Los Angeles, CA 90089-2564, USA. (E-mail: {jongwon,younggoo,cckuo}@sipi.usc.edu) 2 HwangJun Song is currently with the Software Engineering Department of Sejong University, Seoul, KOREA....

Layered multicast is a promising technique for broadcasting adaptive-quality TV video to heterogeneous receivers. While several layered multicast approaches have been proposed, prior work has identified several problems including significant and persistent instability in video quality, arbitrary unfairness with other sessions, low access link utilization due to conservative bandwidth allocation, and problems with receiver synchronization. In this paper we propose a new layered multicast scheme, where we exploit a simple, coarse-grained, two-tier loss differentiation architecture to achieve stable and fair bandwidth allocation for viewers. Despite the simplicity of our loss differentiation model, we show that it achieves most of the benefits of complex and costly priority dropping schemes. In addition, our protocol is receiver-driven and thus retains the incentives to limit bandwidth usage that are not present in existing priority dropping schemes. Keywords--- multicast, layered video,...

Traffic smoothing for delivery of online VBR media streams is one of the most important problems in designing multimedia systems. Given available client buffer and a window-sliding size, conventional approaches try to reduce bandwidth allocated in each window. However, they can not lead to the minimization of bandwidth allocated for transmitting entire stream. Although a window-sliding approach was introduced to further reduce the bandwidth allocated recently [21], it was computational costly. In this paper, an effective and efficient online traffic-smoothing scheme is proposed. Different from the conventional static window-sliding approaches, our approach dynamically decides the suitable window-sliding size to online smooth the bursty traffic. Then, an aggressive workahead scheme is applied in transmitting entire stream. By examining different media streams, our approach has small bandwidth, high bandwidth utilization and small computation cost. Considering the online transmission of a Star War movie, our approach result is 13 % less for the bandwidth and 4% less for the network idle rate than SLWIN(1). Comparing the number of window sliding, our approach is 75 % less than SLWIN(1). The relations between the characteristic of input traffic and the behavior of obtained scheduling results are discussed. Finally, an extension of the proposed approach to resolve the latency and quality tolerance applications is also introduced. I.