SYSTEM, METHOD AND COMPUTER READABLE MEDIUM OF EFFICIENTLY DECODING AN AC-3 BITSTREAM BY PRECALCULATING COMPUTATIONALLY EXPENSIVE VALUES TO BE USED IN THE DECODING ALGORITHM

A method and system for providing an inverse transform for an audio compression decoding algorithm in software precalculates a plurality of identified values; each of which is computationally intensive. The method and system then performs a pre-inverse transform complex multiply utilizing a first portion of the identified values and an array of input coefficients to provide a plurality of intermediate values. Thereafter, an inverse transform complex multiply and a post inverse transform multiply are combined to provide a combined complex multiply operation. The combined complex multiply operation uses a second portion of the identified values and the intermediate values provides the inverse transform. Accordingly, through the use of the present invention, the number of instructions for implementing the inverse transform can be substantially minimized. In the prior art, the method for performing the inverse discrete cosine transform (IDCT) in the AC-3 algorithm is extremely inefficient for software decoder implementations. Through the use of the present invention, the algorithm performance on a superscalar processor as measured by issued instructions is improved by a factor on the order of 43.