Downmixing device and method

A downmixing method comprising:

• input receiving to receive an input signal including a plurality of channels;
• matrix converting to perform a matrix operation for the input signal using a matrix D and output a plurality of signals applied with the matrix operation;
• rotation correcting to provide different phase rotations with each of at least two signals of the plurality of signals outputted by the matrix converting based on vectors of the plurality of channels when each of phases of the at least two signals is the same;
• spatial information extracting to extract spatial information from output signals of the rotation correcting;
• inverse matrix converting to perform an inverse matrix operation for the output signals of the rotation correcting and for a signal generated based on the spatial information using an inverse matrix D−1, which is an inverse of the matrix D used for the matrix converting;
• error calculating to calculate, by a computer processor, an error amount between the input signal and a result of the inverse matrix operation;
• comparing a new error amount obtained by the error calculating with an error amount in the past;
• updating the phase rotation and spatial information in the past to a new phase rotation and spatial information extracted at the spatial information extracting that correspond to the new error amount when the new error amount obtained at the comparing errors is less than the error amount in the past;
• and
• repeating the rotation correcting, the spatial information extracting, the inverse matrix converting, the error calculating, the comparing errors and the updating while changing the different phase rotations for the plurality of signals outputted by the matrix converting.