Patent ID: 8195316

Claim:
An audio apparatus comprising: An input unit for inputting stereo signals in which surround-sound signals are mixed in accordance with a predetermined algorithm and encoding information specifying encoded contents of the algorithm; a surround-sound signal generator for generating left-side surround-sound signals and right-side surround-sound signals by decorrelating left-side signals and right-side signals contained in the stereo signals; and a controller for controlling the decorrelation performed by the surround-sound signal generator based on the encoding information; wherein the surround-sound signal generator comprises a first surround-sound signal generator for generating the left-side surround-sound signals by extracting components that are highly correlated with right-side signals in the left-side signals of the stereo signals and subtracting the extracted components from the left-side signals, and a second surround-sound signal generator for generating the right-side surround-sound signals by extracting components that are highly correlated with left-side signals in the right-side signals of the stereo signals and subtracting the extracted components from the right-side signals; wherein the controller controls the highly-correlated-component extraction performed by the first and second surround-sound signal generators, based on the encoding information; wherein the first surround-sound signal generator updates a filter coefficient of an adaptive filter by using an adaptive algorithm to extract the components that are highly correlated with the left-side signals in the right-side signals, and the second surround-sound signal generator updates a filter coefficient of an adaptive filter by using an adaptive algorithm to extract the components that are highly correlated with the right-side signals in the left-side signals, and wherein the controller changes a value of a step-size parameter for determining an adaptation speed of the filter coefficients of the adaptive filters in the first and second surround-sound signal generators, based on the encoding information.