The Research On Scheduling Algorithm Of Video-on-Demand System

VOD is one of the key technologies in multimedia applications. The problem of effective resource use stands out in large VOD system. The great capacity of data transmission makes network I/O and disk I/O bandwidth the bottlenecks in VOD system. Aimed at these two bottlenecks, the VOD stream scheduling algorithm focus on how to satisfy request as many as possible in the restrict of limited server resource.In the paper, one kind of VOD scheduling algorithms, the patching scheduling algorithm, has been studied. The grouped periodic patching scheduling algorithm is put forward based on it. The main contributions of this new algorithm are as follows. First, grouped the patch streams of every period according to the arrival time. The frequency of patch stream is restricted with the method of batching and it makes the patch stream well-regulated. Second, the period of multicast stream is adjusted to the change of the request rate and the group time is adjusted to the change of the available bandwidth. Third, we merged the last group of request into the coming sharing stream so as to reduce the patch stream number much more. As the simulation experiment showed, the grouped periodic patching scheduling algorithm can sharply reduce bandwidth expense of the server in the same condition. And patch stream number in one period is much less than that of traditional periodic patching algorithm obviously. Secondly, the algorithm of user interactive control in the condition of multicast is studied and the method of user interactive control is realized. As the disk capacity of personal computer becoming larger and larger, we suggest reduce the resource expense on jump-backward operation by making full use of the client disk buffer. To resolve the difficulty of speeding play and speeding back play in VOD system, a new method is put forward in this paper.In the end of this paper, we designed and realized a simple VOD system. The grouped periodic patching algorithm has been applied in this system, and a simple VOD server and a real-time network player are realized. In this system, we resolved the problem of large delay in RTP packing by a simple and effective method and designed an effective rate control scheme in the VOD realization.