Deterministic admission control strategies in video servers with variable bit rate streams

Abstract

Video servers are a key component in multimedia systems. Due to the real-time requirements and high resource demand of digital media, a video server must restrict the number of simultaneously serviced media streams. We consider the admission control problem in video servers for the retrieval of media data from secondary storage. Admission control decides whether or not a new request can be accepted without affecting the service given to the already admitted streams. Traditional retrieval methods, such as cyclic retrieval of variable size data segments or retrieval at the stream's mean bit rate, either cannot profit from smoothing media traffic over larger intervals or suffer from excessive buffer demand and latency. We introduce, for the first time, retrieval techniques for variable bit rate data that are non-buffer-conserving in nature and cover all traditional methods as special cases. For all the schemes, we carry out a comparative performance analysis and show how they allow to trade-off buffer requirement, disk I/O efficiency, and latency. All the schemes considered support the full set of VCR operations such as fast forward, pause, or fast reverse.