Process for updating the size of the interval in the arithmetic coding method

摘要

The present invention relates to a process for updating the size of the interval in arithmetic coding, characterised in that . a set of values A = {A[0], A[1], ..., A[r-1]} is selected and the size of the interval is held as an index Wi in this set . a single table enquiry performs an updating of the interval size and also provides the augend and the shift by performing the following operation: (Wi+1, Xi,Ri)=f"(si,Wi where the function f" is implemented through a single reference to the table, in which p(Si) and P(Si) are determined from Si; A[Wi] is determined from Wi; p(Si).A[Wi] and Ri = P(Si).A[Wi] are calculated; the shift Xi is determined which is required to represent p(Si).A[Wi].2xi in R; Wi+1 is determined such that A[Wi+1] is the best representation of p(Si).A[Wi].2wi; Wi+1,Xi and Ri are returned to. IMAGE