Patent ID: 6580379
Filing Date: 2003-06-17
Classification: H03M

Abstract:
A method of arithmetically decoding an arithmetically encoded information signal into an output information signal comprising a serial sequence of n-bit symbols, where n is an integer and n=1, the method being adapted to produce a first and a second sequential output symbols of the output information signal in a decoding cycle, and comprising the steps of:(a) receiving the arithmetically encoded information signal, (b) retrieving from finite-size first and second registers values for an A and a C parameter respectively, the A parameter having a relationship with a size of a value interval, the C parameter having a relationship with a boundary of the interval, (c) generating a first probability value for a first symbol to be produced, the first probability value indicating the probability that the first symbol has a least probable value, and generating a second probability value for a second symbol to be produced, the second probability value indicating the probability that the second symbol has the least probable value, (d) deriving the first symbol in response to the first probability value, and in response to the values for A and C retrieved from the first and the second registers, respectively, (e) updating the A parameter so as to obtain an updated A parameter, (f) updating the value for A retrieved from the first register to a value for a temporary A parameter, for the case when the first symbol produced from decoding has a most probable value, (g) deriving a temporary C parameter from the C parameter retrieved from the second register, (h) deriving the second symbol in response to the second probability value, and in response to the values of the temporary A parameter and the temporary C parameter, (i) outputting both the first and the second symbol when the first symbol has the most probable value or outputting the first symbol only if the first symbol has the least probable value, (j) deriving new A and C parameters, (k) storing the new A and C parameter in the first and second register, respectively.