Energy reduction is critical to increase the mobility and battery life for today?s pervasive portable computing systems. At the same time, energy reduction must be subject to the real-time constraints and quality of service (QoS) requirements for multimedia applications running on many of these systems. This paper presents a novel run-time scheduling approach to reduce the system-wide energy consumption for such systems. In this paper, the multimedia applications are modeled using a popular weakly hard realtime model, i.e., the (m, k)-model. Our experimental results show that, by judiciously scheduling the real-time tasks and shutting down the processor and/or peripheral devices, our approach can lead to significant energy savings while guaranteeing the (m, k)-firm deadlines at the same time.