Research On Scheduling Algorithm Of Multimedia System

With the development of multimedia coding technology, a lot of multimedia applications with the characteristic of stream are popular. These applications need to be processed in the restricted time, for example, sound and picture can not stop in the video conference system. And It is different with traditional real-time applications, missing frames occasionally will not cause the severe result in the kind of applications which just demand the probabilistic success of the data process finished in the restricted time. So we call the kind of application soft real-time application.Multimedia stream applications need the real-time support from the storage, transmission and CPU(Center Processing Unit) scheduling in the multimedia system. And CPU is one of the important resources in the system. A good CPU task scheduling algorithm can offer low deadline missing percent of the tasks and high CPU utilization,which are key factors for real-time multimedia application. Due to traditional way of time-sharing scheduling can not satisfy the real-time demand of multimedia application, the real-time scheduling algorithm for multimedia stream was paid special attention.In the past research, major scheduling ways are pessimistic and optimistic idea which are based on traditional periodic model, periodic multiframe task model and heuristic scheduling. But there are some problems such as not having exact scheduling conditions or low CPU utilization.For solving the above problems, the multimedia stream task is called irregular periodic task. According to the notion,the irregular periodic model is presented to transform it to a periodic task and a bursting task. The task set is scheduled in the way, that is periodic task scheduled by RM(Rate Monotonic) and bursting task by sporadic server. The way not only offer the hard real-time guarantee for the periodic task ,but also keep the missing deadline percent of the bursting task low to satisfy the soft real-time demand so that guarantee multimedia stream task real-time.At the same time,the system can allow more tasks to enter and improve the CPU resource utilization.