Using Speed Diagrams for Symbolic Quality Management

We present a quality management method for multimedia applications. The method takes as input an application software composed of actions. The execution times of actions are unknown increasing junctions of quality level parameters. The method allows the construction of a quality manager which computes adequate action quality levels so as to meet QoS requirements for a given platform. These include deadlines for the actions as well as quality maximization and smoothness. We extend and improve results of a previous paper by focusing on the reduction of overhead due to quality management. We propose a symbolic quality management method using speed diagrams, a representation of the system´s dynamics. Instead of numerically computing a quality level for each action, the quality manager changes action quality levels based on the knowledge of constraints characterizing control relaxation regions. These are sets of states in which quality management for a given number of steps can be relaxed without degrading quality. We provide experimental results for quality management of an MPEG encoder, in particular performance benchmarks for both numeric and symbolic quality management.