Video-on-demand server retrieval scheduling to support scan operations

Abstract

In this paper, we present an effective storage and retrieval scheme of MPEG encoded video to support interactive scan operations such as fast-forward or fast-reverse with viewing in a disk-array-based video sever. Typically, scan operations impose additional disk bandwidth requirements due to inter-frame dependencies of MPEG encoded video. Furthermore, the unpredictable nature in terms of the occurrence and the duration makes it difficult for the server to schedule scan requests. In most conventional schemes, the changes of load caused by normal playback to scan transitions are accommodated by statically reserving some of the disk bandwidth at the expense of throughput. On the contrary, in the proposed scheme based on segment interleaving and peak data rate retrieval, the bandwidth needed for scan operations is dynamically allocated by exploiting frame prefetch effect due to variable bit rate (VBR) characteristics of MPEG video stream. The proposed retrieval scheduling scheme can support a lot of concurrent scan requests with low start-up latency while simultaneously servicing the maximum number of streams that can be supported on the server. It neither degrades the throughput nor violates continuous playback of normal playback streams in progress. The maximum number of supportable streams is rather increased due to employing a fixed-size segment that is an exact multiple of track as the retrieval unit. The effectiveness of retrieval scheduling based on dynamic disk bandwidth allocation is demonstrated through performance evaluation.