Meeting CPU constraints by delaying playout of multimedia tasks

Multimedia applications today constitute a significant fraction of the workload running on portable devices such as mobile phones, PDAs and MP3 players. However, the processors in such devices are usually not powerful enough to support multiple concurrently executing multimedia tasks. In this context, different processor scheduling algorithms have attracted a lot of attention. This paper attempts to address the CPU constraint problem from a different perspective. It is based on the observation that by increasing the playout delay of a multimedia task, the minimum processor frequency required to run the task decreases. This is due to the high data-dependent variability in the execution requirements of multimedia tasks. We also present a framework, using which it is possible to compute the minimum processor frequency corresponding to any playout delay. Given a set of concurrently executing multimedia tasks, using our framework it is possible to compute the playout delays for each of these tasks, such that the sum of their corresponding processor cycle requirements do not exceed the maximum frequency supported by the processor.