Power Management for Mobile Multimedia: From Audio to Video and Games

Multimedia applications today constitute a sizeable workload that needs to be supported by a host of mobile devices ranging from cell phones, to PDAs and portable game consoles. Battery life is a major design concern for all of these devices. Whereas both - the complexity of multimedia applications and the hardware architecture of these devices - have progressed at a phenomenal rate over the last one decade, progress in the area of battery technology has been relatively stagnant. As a result, currently a lot of effort is being spent to develop high-level power management and application tuning techniques to minimize energy consumption and thereby prolong battery life. Such techniques include dynamically scaling the underlying processor's voltage and clock frequency in response to a time-varying workload, powering down certain system components when not being frequently used, and backlight scaling in LCDs with controlled image-quality degradation. Some of the application tuning techniques include selectively ignoring certain perceptually-irrelevant computations during audio decoding, and injecting metadata with workload information into video clips which can then be used to accurately estimate the decoding workload at runtime for better power management. In this tutorial, we plan to give a comprehensive overview of this area and discuss power management schemes for a broad spectrum of multimedia applications. In particular, we will talk about several power management and application tuning techniques specifically directed towards audio decoding, video processing and interactive 3-D game applications. Starting from the basics of power management for portable devices, we will discuss the necessary mathematical techniques, give high-level overviews of relevant algorithms and also present the hardware setup that is necessary to perform research and development in this area. The main objective of this tutorial will be to cover various techniques for power management for audio, video and graphics-intensive game applications running on battery-operated portable devices. In particular, we would illustrate how power management techniques differ for audio, video and game applications and would present a number of techniques for each of these classes of applications. We would also give an overview of open research problems and the challenges facing this area. Finally, we would describe some of the hardware platforms that we have been using to conduct research in this domain and give demonstrations of selected power management techniques.