Adaptive cycle extension in multimedia document retrieval

Abstract

Cycle based disk scheduling approach is widely used to satisfy the timing constraints of the multimedia data retrieval. While cycle based disk scheduling for multimedia data retrieval provides effective way of exploiting the disk bandwidth, it is possible that ongoing streams get exposed to jitter when the cycle is extended due to commencement of new session. In this article, we present the novel idea of avoiding temporal insufficiency of data blocks, jitter, which occurs due to the commencement of new session. We propose that sufficient amount of data blocks be available on memory such that the ongoing session can survive the cycle extension. This technique is called "pre-buffering". We examine two different approaches in pre-buffering: (i) loads all required data blocks prior to starting retrieval and (ii) incrementally accumulates the data blocks in each cycle. We develop an elaborate model to determine the appropriate amount of data blocks necessary to survive the cycle extension and to compute startup latency involved in loading these data blocks. The simulation result shows that limiting the disk bandwidth utilization to 60% can greatly improve the startup latency as well as the buffer requirement for individual streams. The algorithm proposed in this work can be effectively incorporated into modem streaming server design.