A method for generating an upmixed multi-channel output audio signal having N output channels from a two-channel input audio signal having a left input channel and a right input channel, where N is a positive integer greater than two, comprising: calculating an inter-channel level difference ( ICLD) based on the left input channel and the right input channel; calculating an estimated panning angle from the inter-channel level difference; calculating an in-phase coefficient ( α) and an out-of-phase coefficient ( β) based on the estimated panning angle; calculating an inter-channel phase difference ( ICPD) based on the left input channel and the right input channel to determine a relative phase difference between the left input channel and right input channel that indicates whether the left input channel is in phase or out of phase with the right input channel and vice versa; calculating a first dematrixing coefficient, denoted as a; calculating a second dematrixing coefficient, denoted as b; generating each of the N output channels by mixing in a linear manner the first dematrixing coefficient times the left or right input channel and the second dematrixing coefficient times the right or left input channel; and causing each of the N output channels of the upmixed multi-channel output audio signal to be played back through speakers in a multi-channel playback environment; characterized in that the first dematrixing coefficient is calculated based on a first trigonometric function of a combination of an in-phase signal component and an out-of-phase signal component; and the second dematrixing coefficient is calculated based on a second trigonometric function of the combination of the in-phase signal component and the out-of-phase signal component; wherein the in-phase signal component is based on the inter-channel phase difference multiplied by the in-phase coefficient and the out-of-phase signal component is based on the inter-channel phase difference multiplied by the out-of-phase coefficient. calculating an inter-channel level difference ( ICLD) based on the left input channel and the right input channel; calculating an estimated panning angle from the inter-channel level difference; calculating an in-phase coefficient ( α) and an out-of-phase coefficient ( β) based on the estimated panning angle; calculating an inter-channel phase difference ( ICPD) based on the left input channel and the right input channel to determine a relative phase difference between the left input channel and right input channel that indicates whether the left input channel is in phase or out of phase with the right input channel and vice versa; calculating a first dematrixing coefficient, denoted as a; calculating a second dematrixing coefficient, denoted as b; generating each of the N output channels by mixing in a linear manner the first dematrixing coefficient times the left or right input channel and the second dematrixing coefficient times the right or left input channel; and causing each of the N output channels of the upmixed multi-channel output audio signal to be played back through speakers in a multi-channel playback environment; characterized in that the first dematrixing coefficient is calculated based on a first trigonometric function of a combination of an in-phase signal component and an out-of-phase signal component; and the second dematrixing coefficient is calculated based on a second trigonometric function of the combination of the in-phase signal component and the out-of-phase signal component; wherein the in-phase signal component is based on the inter-channel phase difference multiplied by the in-phase coefficient and the out-of-phase signal component is based on the inter-channel phase difference multiplied by the out-of-phase coefficient.