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 vari-able
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 compar-ative
performance analysis and show how they allow to trade-off buffer require-ment,
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.
