视频服务器比例服务策略的改进

THE IMPROVEMENT ON PROPORTIONAL SERVICING POLICY IN VIDEO SERVER

本文对ＶＯＤ视频服务器中同时为多个点播用户服务的比例服务策略进行了改进，比例服务策略在一个服务循环中，每路视频流所回取的数据块数与该流的播放帧率成正比．当用该算法算出的回取块数不为整数时，利用交替改变读取数据块数的方法，对连续的服务循环中所读出的各条流的数据块数分别进行细调，以获得同时为尽量多点播用户提供服务，同时也使所需的缓冲器大小以及新允许服务的视频流的起动时迟较小．通过增强比例服务算法的动态适应性，可透明地实现点播用户数的增减（即不影响在点播视频的连续播放），有效地实现允许控制．

The paper makes some improvements on proportional servicing policy that is used in video on demand video server.Proportional servicing policy is a video servicing method with which the video stream data blocks retrieved in a servicing round are proportional to the playback rate of the video stream. When the block number calculated in proportional servicing policy is not a integer number, it uses a staggered toggling technique in which successive block numbers of retrieved video data are fine tuned individually to achieve the servicing of an optimal number of subscribers simultaneously. The improved algorithm is also powerful enough to make the buffer size that is asked and the start up time of a new admitted stream least. By arising the dynamic adaptability of proportional algorithm, the adding or deleting subscriber requests dynamically in a transparent manner is permitted (i.e. without causing discontinuity in the retrieval of any of the existing subscribers) and an efficient admit control is realized.