An adaptive differential pulse code modulation (DPCM) algorithm is presented that determines, for each window, the best causal nonsymmetric half-plane region of support (ROS) in addition to the best prediction coefficients. First, a recursive algorithm is developed that determines the best (in the sense of minimizing the mean-square error) first-, second-, and third-order ROS from the covariance measurements. A procedure for determining the order of the ROS that maximizes the compression ratio, which is based on the window size as well as the covariance measurement, is then developed.>