Abstract: In a system 100, such as a video-on-demand-server, a reader 180 reads data from a storage medium 110 and stores the read data in buffers 125. The data is supplied from the buffers 125 to users 130 for consumption in the form of a plurality of data streams. The data streams may be fixed rate or variable rate with an identical maximum consumption rate of R.sub.max data elements per second. The reader 180 is controlled by a scheduler 170. The scheduler 170 divides a predetermined period of t.sub.cycle seconds, wherein for each active data stream at least R.sub.max *t.sub.cycle data elements can be read from the storage medium, into n successive time intervals, each of t.sub.interval seconds. For each data stream a corresponding buffer 125 is reserved for storing at least R.sub.max *(n+1)*t.sub.interval data elements. The data is read from the storage medium 110 by repeatedly sweeping the storage medium 110 for a group of data streams.

Abstract: Compressed digitally encoded video signals are transmitted over an asynchronous transfer mode network with varying grades of service dependent on bitrate requirements for a desired picture quality and the currently available network capacity. To maximize transmission quality and minimize cost, the grade of service requested from the network is changeable in response to scene changes.

Abstract: A system, such as for example, a video server in a multimedia system, delivers data to a number of users, each of which may have a variable consumption rate. The system reads data blocks from the storage medium in successive sweeps and places the data in user buffers. The system in accordance with the invention reads, for a given user, one block of data from the storage medium no more than every other sweep, so that the duration of a sweep is shorter. Thus, whether a user needs data is checked more frequently and fewer data need be stored in the buffer of the user. As a result, the size of the buffer may be smaller.

Abstract: A method and a system for the interleaving of real-time files so as to form an interleaved combination for storage or transmission. They can be used for a multimedia application in which real-time files containing audio and/or video information are combined so as to form a real-time file for use by the application. The invention utilizes a structure in which the real-time files are stored in dependence on their period in conformity with a given space-saving criterion. Subsequently, on the basis of the structure, an interleaved combination is formed in which the number of empty positions in the combination is limited.