Probability adaptation for arithmetic coders

摘要

Apparatus and method for adapting the estimated probability of either the less likely or more likely outcome (event) of a binary decision in a sequence of binary decisions involves the up-dating of the estimated probability in response to the renormalization of an augend A. The augend A changes value with each binary decision, the size of the change depending on which of the binary events has occurred as input. Re-normalization of A occurs when the A value becomes less than a prescribed minimum value AMIN. According to the invention, there may be differing contexts in which binary decisions may occur, each context having a corresponding estimated probability value which is up-dated with binary decisions in the respective context. Also according to the invention, there may be one or more possible next values for an estimated probability in response to a given binary decision event. The selection of one of multiple possible next values in response to a given binary decision event is preferably determined based on a renormalization correlation count.