Quantiser Control for Rate-Quality Optimisation

Abstract

In Chapter 2, real-time video compression techniques and video traffic management schemes for ATM networks were briefly reviewed. It was shown that the transmission buffering technique is widely used for traffic management as well as video rate control. In this chapter, first, algorithmic features of the buffer-based rate control technique will be investigated, which are specified in international standards. This will be followed by a review of quantisation aspects: adaptive quantisation and rate-distortion theory. The quantiser is the function which actually controls the data rate. The buffering technique is associated with the quantiser by changing the step size depending on the buffer occupancy. As a compressed video stream from an MPEG video encoder is inherently variable rate data there should be a buffer to convert the variable bit rate to constant bit rate in the CBR mode. This configuration is common to the standards, thus, the effect of improvements of this rate control technique can be generalised for any buffer-controlled quantisation scheme. Rate-distortion theory is inevitably involved since the buffer-based rate control scheme operates via the quantiser which introduces distortion. On this basis, a brief review of the rate-distortion analysis on the adaptive quantisation will be presented within the framework of the CBR mode.