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 system for providing an audio signal in an audio signal reception system, the system comprising:

• means for receiving a digitally compressed audio signal;
• means for decoding the digitally compressed audio signal, wherein the decoding means comprises,
• means for precalculating a plurality of identified values, wherein the identified values comprise values which are used more than once in the iteration of a performing means and a combining means;
• means for performing 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;
• and
• means for combining an inverse transform complex multiply and a post inverse transform multiply to provide a combined complex multiply operation, the combined complex multiply operation utilizing a second portion of the identified values and the plurality of intermediate values to provide the inverse transform for the array of input coefficients;
• and
• means for outputting the decoded audio signal to a speaker system.

A computer readable medium containing program instructions for providing an audio signal in an audio signal reception system, the instructions for:

• a) receiving a digitally compressed audio signal;
• b) decoding the digitally compressed audio signal, wherein the decoding comprises the instructions for,
• b1) precalculating a plurality of identified values, wherein the identified values comprise values which are used more than once in the iteration of steps b2) or b3);
• b2) performing 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;
• and
• b3) combining an inverse transform complex multiply and a post inverse transform multiply to provide a combined complex multiply operation, the combined complex multiply operation utilizing a second portion of the identified values and the plurality of intermediate values to provide the inverse transform for the array of input coefficients;
• and
• c) outputting the decoded audio signal to a speaker system.