An integrated multimedia file system supports the storage and retrieval of multiple data types. In this paper, we first discuss various design methodologies for building integrated file systems and examine their tradeoffs. We argue that, to efficiently support the storage and retrieval of heterogeneous data types, an integrated file system should enable the coexistence of multiple data type specific techniques. We then describe the design of Symphony--an integrated file system that achieves this objective. Some of the novel features of Symphony include: a QoS-aware disk scheduling algorithm; support for data type specific placement, failure recovery, and caching policies; and support for assigning data type specific structure to files. We discuss the prototype implementation of Symphony, and present results of our preliminary experimental evaluation. Keywords: Multimedia file systems, multimedia operating systems, integrated file systems 1. INTRODUCTION Recent advances in compression...

A multimedia file system supports diverse application classes that access data with heterogeneous characteristics. In this paper, we describe our experiences in the design and implementation of the Symphony multimedia file system. We first discuss various methodologies for designing multimedia file systems and examine their tradeoffs. We examine the design requirements for such file systems and argue that, to efficiently manage the heterogeneity in application requirements and data characteristics, a multimedia file system should enable the coexistence of multiple data type-specific and application-specific techniques. We describe the architecture and novel features of Symphony and then demonstrate their efficacy through an experimental evaluation. Our results show that Symphony yields a factor of 1.9 improvement in text response time over conventional disk scheduling algorithms, while continuing to meet the real-time requirements of video clients. Finally, we reflect upon the lessons learned from the Symphony project.

Abstract: Video streaming over wireless networks is challenging due to node mobility and high channel error rate. In this paper, we propose a multi-source video streaming (MUVIS) system to support high quality video streaming service over IEEE 802.11-based wireless networks. We begin by collocating a streaming proxy with the wireless access point to help leverage both the media server and peers in the WLAN. By tracking the peer mobility patterns and performing content discovery among peers, we construct a multisource sender group and stream video using a rate-distortion optimized scheme. We formulate such a multi-source streaming scenario as a combinatorial packet scheduling problem and introduce the concept of asynchronous clocks to decouple the problem into three steps. First, we decide the membership of the multi-source sender group based on the mobility pattern tracking, available video content in each peer and the bandwidth each peer allocates to the multi-source streaming service. Then we select one sender from the sender group in each optimization instance using asynchronous clocks. Finally, we apply the point-to-point rate-distortion optimization framework between the selected sender-receiver pair. In addition, we implement two different caching strategies, simple caching simple fetching (SCSF) and distortion minimized smart caching (DMSC), in the proxy to investigate the effect of caching on the streaming performance. To design more realistic simulation models, we use the empirical results from corporate wireless networks to generate node mobility. Simulation results show that our proposed multi-source streaming scheme has better performance than the traditional server-only streaming scheme and that proxy-based caching can potentially improve video streaming performance. Index Terms: Caching strategies, multi-source video streaming, rate-distortion optimized packet scheduling. I.