1 Yima : Design and Evaluation of a Streaming Media System for Residential Broadband Services Roger Zimmermann, Kun Fu, Cyrus Shahabi, Didi Yao, Hong Zhu Abstract—We describe and evaluate the implementation of a streaming media system called Yima, which consists of a scal- able continuous media server and client components. We report on the real-life experiences that we gained from streaming near NTSC quality video and audio to residential locations within a metropolitan area. We investigated the feasibility of such stream- ing services with current broadbandtechnology. We describe our experimental setup and the results, which indicate that streaming applications, such as movie-on-demand, are not only technically feasible but also may be economically viable in the near future. Keywords— Multimedia delivery, distributed architecture, scalability, variable bit rate media, video servers I. INTRODUCTION OST currently deployed networks, such as the Inter- net and corporate Intranets, are based on IP. Further- more, isochronous media types, such as video and audio, are becoming ubiquitous and need to be disseminated via these IP networks. Yima is a complete end-to-end sys- tem that addresses the issues of (a) storing and retrieving isochronous media types, (b) delivering such media types with their real-time constraints intact, and (c) rendering the media at the client location. Yima relys on commod- ity off-the-shelf (COTS) hardware components, such as standard personal computers, to provide a cost-effective solution. It is designed to support a wide range of media delivery bit rates from several hundred Kb/s (e.g., MPEG- 4) to more than 20 Mb/s (e.g., HDTV streams compressed with MPEG-2). Many of todays isochronous media streams are com- pressed at variable bit rates (VBR), for example accord- ing to the MPEG-4 industry standard. Yima supports the streaming of VBR media via a simple yet flexible flow con- trol paradigm. With this mechanism, the sender (server) does neither need to know about the compression scheme that is used for a specific stream, nor does it need to under- stand the details of a stream’s file format. Therefore, new In ancient Iranian religion, Yima is the first man, the progenitor of the human race, and son of the sun. The authors are with the Integrated Media Systems Center, 3740 McClintock Avenue, Suite 131, Los Angeles, CA 90089- 2561. E-mails: [rzimmerm, kfu, cshahabi, didiyao, zhu]@usc.edu. This research has been funded in part by NSF grants EEC-9529152 (IMSC ERC) and ITR-0082826, and unrestricted cash/equipment gifts from IBM, Intel and SUN. streamable media types, such as real-time haptic informa- tion [1], can easily be added. This study presents an evaluation of Yima for video-on- demand type applications (e.g., distance learning, movie- on-demand) via currently available broadband connections to residential homes. There have been a number of reports of trials and deployments of video-on-demand services. However, little to no information is available about the ar- chitectural details and performance tradeoffs for these sys- tems. For this study we have setup a client-server testbed that employs industry standards such as MPEG-4, ADSL (asynchronous digital subscriber line), RTP (real-time pro- tocol [2]) and RTSP (real-time streaming protocol) over IP to evaluate the feasibility and performance of near NTSC quality video delivery to the home. Fig. 1 illustrates the experimental setup. Section II introduces the Yima system architecture while Section III discusses the performance evaluation. Sec- tion IV contains our conclusions. II. SYSTEM ARCHITECTURE An important component of delivering isochronous mul- timedia over IP networks to end users and applications is the careful design of a multimedia storage server. The task of such a server is twofold: (1) to efficiently store the data and (2) to schedule the retrieval and delivery of the data precisely before it is transmitted over the network. A. Data Placement and Scheduling Magnetic disk drives have established themselves as the storage device of choice for CM servers because of their high performance and moderate cost. To achieve the high bandwidth and massive storage required for multi-user CM servers, disk drives are commonly combined into disk ar- rays to achieve many simultaneous I/O requests [3]. To efficiently store each individual multimedia object and to aggregate the bandwidth of multiple disks without requir- ing data replication, an object is commonly striped into equi-sized blocks: [4], [5]. Both, the display time of a block and its transfer time from the disk are a function of the display requirements of an object and the transfer rate of the disk, respectively. The display requirements of multimedia objects encoded with many of the popular compression algorithms, e.g., MPEG-4, vary