Techniques for efficient stream of layered video in heterogeneous client environments

Abstract

Universal multimedia access (UMA) refers to accessing multimedia content over a wide range of client terminals and network capacities. Scalable coding is a very popular technique to enable UMA for video. Overhead introduced by the scalable coding approach limits the number of layers that can be stored for each video. Therefore some clients may be served the closest available quality than the best-fit quality. This is a major drawback of scalable coding from the end-user perspective. We propose to employ transcoding to tailor content exactly to the client's best-fit quality when the required layer is not stored. Inserting a transcoder in the server-client path introduces new challenges in deciding the layering structure (number of layers, bandwidth per layer) of a video. The optimal layering structure should be decided based on factors like total I/O bandwidth penalty incurred due to layering and transcoding effort required to service the "non-layered" versions. The solution to this problem is further complicated by practical issues like diverse popularity of video objects and resource availability. Another issue that we address in this paper is reducing WAN bandwidth penalty incurred due to transport and coding overhead inherent to scalable coding. This particular problem applies to all schemes that use layered encoding to broadcast video. We map the above mentioned problems onto a 0-1 multiple choice knapsack structure and propose an algorithm to find a near-optimal solution. The uniqueness of our approach not only lies in the streaming model but also in the integrated manner in which we address a variety of issues put forth by layered coding.