Practical Real-Time Approaches for Scheduling VBR Video in a Client-Server Computing Environment

Scheduling of multiple variable-bit-rate (VBR) video packet streams at the server is one of the most crucial issues in the design of a enterprise video-on-demand (VoD) system. Scheduling is important to guarantee the requested QoS levels while maximizing the utilization of the resources. But the scheduling problem is difficult due to the inherent varying resource requirements of the video streams. Although much work on smoothing and scheduling algorithms has been done, these previous techniques, which usually require the knowledge of future frame sizes and are of a high time complexity, are not suitable because in the video application environment envisioned in our study, real-time response from the server is required. In this paper, we propose and evaluate four real-time approaches using real MPEG data. Our results reveal that the proposed real-time techniques introduce only a slight jitter effect on the video display. Furthermore, time-division-based algorithms are superior to rate-based ones.published_or_final_versio

Scheduling of Early Quantum Tasks

An Early Quantum Task (EQT) is a Quantum EDF task that has shrunk its first period into one quantum time slot. Its purpose is to be executed as soon as possible, without causing deadline overflow of other tasks. We will derive the conditions under which an EQT can be admitted and can have an immediate start. The advantage of scheduling EQTs is shown by its use in a buffered multi-media server. The EQT is associated with a multimedia stream and it will use its first invocation to fill the buffer, such that a client can start receiving data immediately