VBR流磁盘I/O的优化调度及特定的缓冲计算

摘要

VBR compressed video can exhibit significant multiple-time-scale bit-rate variation, and this gives a challenge to the transport system, such as network and disk I/O. The optimal smoothing of VBR at present has become an important research area. To stored video, pre-buffering is the most efficient and feasible method. In terms of the basement of VBR stream smoothing schedule for gaining satiable network′s QoS, in the paper we introduce the methods of VBR stream re-smoothing schedule and buffer computing which is based on the characteristics of disk storage system access to data in elementary physic disk-block. The paper first presents a disk I/O schedule algorithm that considers one elementary physic disk-block as buffer size, than gives another disk I/O schedule algorithm whose time complexity is O(n) and buffer computing in the special situation where the access unit is not more than a value.%VBR流如视频流，由于其位率的突发性和频繁的改变，给传输系统（如网络和磁盘I/O端口）带来了巨大的挑战．VBR流的平滑调度和传输控制成为分布式多媒体应用领域内研究的热点．对于存储的视频，在连续传输中，预缓冲是平滑VBR特性非常有效和实用的方法．作者在基于为网络传输而考虑的VBR流平滑算法的基础上，讨论了考虑物理磁盘块存取特性的VBR流二次平滑调度及缓冲计算方法．首先，给出了一个在最小缓冲尺寸下的磁盘I/O调度规划算法A；然后，计算了在最大存取单元（为某种需要而设定的）不超过某一特定值时的最低缓冲需求，及在该最低缓冲需求下的一个复杂度为线性时间的磁盘I/O调度规划算法C．分析结果表明，所设计的算法能100%地利用磁盘空间．