Rate conversion of compressed video for matching bandwidth constraints in ATM networks

Abstract

The majority of the traffic in the future broadband networks are expected to come from video and multimedia services. Also, it is expected that most of the video services will be based on MPEG2 standard, many of them using recorded bit streams. The characteristics of the forthcoming video services demand a new level of adaptation between video sources and transmission networks, or even among different networks. This level should be capable of dealing with compressed bit streams for matching the network requirements to the coded video. A system capable of dynamically matching compressed video bit streams into asynchronous transfer mode (ATM) multiplex channels is needed and no general solution to this requirement has been devised so far. Open loop schemes such as simple requantization of the compressed bit stream or drop of higher frequency coefficients are not suitable for this task because these methods cause drift. This chapter shows that drift can lead to a significant drop in quality just after a small number of predicted frames. Hence, the chapter derives a drift free rate converter, working entirely in the frequency domain and capable of meeting ATM transmission demands.