Storage and retrieval methods to support fully interactive playout in a disk-array-based video server

Abstract

One of the most important challenges in a videoon-demand (VOD) system is to support interactive browsing functions such as “fast forward” and “fast backward.” Typically, these functions impose additional resource requirements on the VOD system in terms of storage space, retrieval throughput, network bandwidth, etc. Moreover, prevalent video compression techniques such as MPEG impose additional constraints on the process since they introduce interframe dependencies. In this paper, we devise methods to support variable rate browsing for MPEG-like video streams and minimize the additional resources required. Specifically, we consider the storage and retrieval for video data in a diskarray-based video server and address the issue of distributing the retrieval requests across the disks evenly. The overall approach proposed in this paper for interactive browsing is composed of (1) a storage method, (2) sampling and placement methods, and (3) a playout method, in which the sampling and placement methods are two alternatives for video-segment selection. The segment-sampling scheme supports browsing at any desired speed while balancing the load on the disk array, as well as minimizing the variation on the number of video segments skipped between samplings. In contrast, the segment-placement scheme supports completely uniform segment sampling across the disk array for some specific speed-up rates. Several theoretical properties for the problem studied are derived. Finally, we describe experimental results on the visual effect of the proposed frame-skipping approach.