Content-based adaptation of streamed multimedia

Most adaptive delivery mechanisms for streaming multimedia content do not explicitly consider user-perceived quality when making adaptations. We show that an Optimal Adaptation Trajectory (OAT) through the set of possible encodings exists, and that it indicates how to adapt encoding quality in response to changes in network conditions in order to maximize user-perceived quality. The OAT is related to the characteristics of the content, in terms of spatial and temporal complexity. We describe an objective method to automatically determine the OAT in response to the time-varying characteristics of the content. The OAT can be used with any transmission adaptation policy. We demonstrate content-based adaptation using the OAT in a practical system, and show how this form of adaptation can result in differing adaptation behaviour.