Adaptive decision-feedback predictive coding of digital sources

A 1-bit adaptive decision-feedback predictive coding (ADFPC) system is derived on the assumption of `good¿¿ decisions. The predictor in the ADFPC is made adaptive by projecting the gradient, at each iteration, along the co-ordinate which exhibits the maximum absolute gradient. This gradient-seeking method requires that the stepsize only needs to be optimum with respect to a single coefficient (co-ordinate) during each iteration. A formula for calculating the stepsize at each iteration is obtained via a minimisation of the squared prediction error. Simulation results obtained in the encoding of a 1st-order autoregressive source and a monochrome image (with the analogue sources digitised by a 6-bit quantiser prior to encoding) reveal that the ADFPC is robust and exhibits good performance.