Designing file systems for digital video and audio

Abstract

We address the unique requirements of a multimedia file system such as continuous storage and retrieval of media, maintenance of synchronization between multiple media streams, and efficient manipulation of huge media objects. We present a model that relates disk and device characteristics to the recording rate, and derive storage granularity and scattering parameters that guarantee continuous access. In order for the file system to support multiple concurrent requests, we develop admission control algorithms for determining whether a new request can be accepted without violating the realtime constraints of any of the requests.We define a strand as an immutable sequence of continuously recorded media samples, and then present a multimedia rope abstraction which is a collection of individual media strands tied together by synchronization information. We devise operations for efficient manipulation of multi-stranded ropes, and develop an algorithm for maintaining the scattering parameter during editing so as to guarantee continuous playback of edited ropes.We have implemented a prototype multimedia file system, which serves as a testbed for experimenting with policies and algorithms for multimedia storage. We present our initial experiences with using the file system.