Matrix decoder with constant-power pairwise panning

A method for upmixing a two-channel input audio signal having a first input channel and a second input channel into an upmixed multi-channel output audio signal having greater than two channels, comprising:

• calculating an inter-channel level difference between the first input channel and the second input channel;
• calculating an inter-channel phase difference between the first input channel and the second input channel;
• calculating an in-phase coefficient and an out-of-phase coefficient based on the inter-channel level difference;
• calculating a first dematrixing coefficient based on the in-phase coefficient and the out-of-phase coefficient;
• calculating a second dematrixing coefficient based on the in-phase coefficient and the out-of-phase coefficient;
• multiplying the first input channel by the first dematrixing coefficient to generate a first sub-signal and the second input channel by the second dematrixing coefficient to generate a second sub-signal;
• mixing the first sub-signal and the second sub-signal to generate the upmixed multi-channel output audio signal for playback;
• and
• outputting the upmixed multi-channel output audio signal for playback through one or more playback devices.