A Priority Selected Cache Algorithm for Video Relay in Streaming Applications

摘要

With the popularization of Internet, many users can obtain various multimedia services through heterogeneous Internet. Among these services, video streaming application is the most challenging. Because of time constraint and variable bit rate (VBR) property of a video, the problem of streaming high quality video is insufficient external WAN bandwidth. Therefore, it is difficult to expand high quality video streaming services. To solve this problem, we proposed a novel video cache algorithm, called the Optimal Cache (OC) algorithm, for a relay video proxy. By caching portions of a video in a relay video proxy closed to clients, the video playback quality can be guaranteed and the problem of insufficient WAN bandwidth across Internet is eliminated. However, data packets are often lost while streaming video data across Internet, which downgrades video playback quality and even halts the video playback. In this paper, we refine the OC algorithm and propose a novel Priority Selected Cache (PSC) algorithm to select maximum high priority video data for caching in a relay video proxy. The PSC algorithm reduces the decoding errors caused by packet loss, improves error recovery, and provides QoS-guaranteed video playback. On the basis of experiment results with testing several benchmark videos, we show that the PSC algorithm caches at least 15% more high priority video data in a relay video proxy than conventional OC algorithm. Additionally, the PSC algorithm uses minimum storage in a relay video proxy and reduces the maximum bandwidth requirement in the WAN (as does the OC algorithm) subject to QoS-guaranteed video playback.