Minimum variance multiplexing of multimedia objects

This paper addresses the problem of simultaneous transmission of multiple multimedia objects (such as images or video sequences) over a bandwidth-limited channel. The trivial strategy of partitioning in equal parts the available rate among the bitstreams is suboptimal, when the multimedia objects have different coding complexities. Exploiting object diversity allows us to allocate the bandwidth according to some optimality criteria, e.g. minimizing the average total distortion or minimizing the variance between the distortions of each object. By describing the rate-distortion characteristics of each multimedia object in terms of a simple exponential model, we provide a closed form solution for both the minimum average and the minimum variance problems. In addition, if we consider the statistical distribution of the rate-distortion model parameters, we can show that the minimum variance solution can effectively reduce the quality fluctuations among the objects, with an overall coding efficiency loss, w.r.t. the minimum average solution, of only 0.5dB on average. Some experiments, carried out on different H.264/AVC video sequences, validate our theoretical results.