RealTracer—Tools for Measuring the Performance of RealVideo on the Internet

The increase in high-bandwidth connections and high-speed computers has spurred the growth of streaming media across the Internet. While there have been a number of studies measuring the performance of traditional Internet traffic, there have not been sufficient empirical measurements ofvideo performance especially for commercial videos across the Internet. The lack of empirical workthat measures streaming video traffic may arise from the lack of effective video performance measurement tools. In this paper, we present RealTracer, a set of tools for measuring the performance of RealNetworks Video. RealTracer includes RealTracker, a customized video playe that plays RealNetworks Video from pre-selected playlist and records user-centric video performance information. RealTracer also includes RealData, a data analysis tool that helps manage,parse and analyze data captured by RealTracker. We describe the software architecture and usage ofRealTracker and the usage of RealData, both publicly available for download. To illustrate the useof RealTracer, we present some results from a study that used RealTracker to measure RealVideo performance across the Internet. Using RealData, that study made several contributions to better understanding the performance of streaming video on the Internet. Typical RealVideos have high quality, achieving an average frame rate of 10 frames per second and very smooth playout, but very few videos achieve full-motion frame rates. Overall video performance is most influenced by the bandwidth of the end-user connection to the Internet, but high-bandwidth Internet connections are pushing the video performance bottleneck closer to the server. Yubing Wang earned M.S. in Electrical Engineering from University of Science and Technology of China in 1993 and M.S. in Computer Science from WPI in 2001. He is currently working in EMC Corp. as a principal software engineer, participating in the developments of several EMC NAS products. He is also a Ph.D. candidate in Computer Science of WPI. His primary research interests include multimedia networking and distributed file system. Mark Claypool earned M.S. and Ph.D. degrees from the University of Minnesota in 1993 and 1997, respectively. Dr. Claypool joined the Computer Science department of WPI in 1997, receiving tenure and promotion to Associate Professor in 2004. He is also the Director of the Interactive Media and Game Development major at WPI, a 4-year degree in the principles of interactive applications and computer-based game development. His primary research interests include multimedia networking, congestion control, and network games.     

Empirical evaluation of the congestion responsiveness of RealPlayer video streams

Increasingly popular commercial streaming media applications over the Internet often use UDP as the underlying transmission protocol for performance reasons. Hand-in-hand with the increase in streaming media comes the impending threat of unresponsive UDP traffic, often cited as the major threat to the stability of the Internet. Unfortunately, there are few empirical studies that analyze the responsiveness, or lack of it, of commercial streaming media applications. In this work, we evaluate the responsiveness of RealNetworks’ RealVideo over UDP by measuring the performance of numerous streaming video clips selected from a variety of RealServers on the Internet, analyze the TCP-Friendliness of the UDP streams and correlate the results with network and application layer statistics. We find that most RealVideo UDP streams respond to Internet congestion by reducing the application layer encoding rate, and streams with a minimum encoding rate less than the fair share of the capacity often achieve a TCP-Friendly rate. In addition, our results suggest that a reason streaming applications choose not to use TCP is that the TCP API hides network information, such as loss rate and round-trip time, making it difficult to estimate the available capacity for effective media scaling.     

基于流媒体的音频点播技术及其应用

本文简要分析了流媒体技术及其文件格式,介绍了流媒体的制作、播放和管理的方法,并实现了一基于流媒体的网上音频点播系统。     

用VC＋＋完善RealPKayer

目前流行的媒体播放软件RealPKayer存在着一些使用不便之处。我们为了解决这些问题而采用VC＋＋6．0编制了一个小程序。该程序能够适当弥补RealPKayer的不足。同时该程序所采用的很多技巧对于我们其它程序也具有相当的参考价值。