A minimum risk quantizer for motion compensated image coding

In this paper, the problem of minimizing the quantization distortion when the source is a sequence of images is considered from a different perspective. The quantizer that is considered is part of a motion compensated image coding system. In this application, the number of levels is not fixed but varies from one block of pixels to another. The implication of this is that the calculation of the quantizer levels and threshold for each block when the distortion measure is the MSE is prohibitive from a computation standpoint. This problem is circumvented by choosing a distance criterion rather than the MSE. Additionally, the minimum distortion procedures of Max and Lloyd are not utilized. Rather, a minimum risk (minimum expected cost) procedure which employs the absolute value cost function is formulated. The procedure yields a quantizer with a lower variance error distribution.