Flexible sum-difference stereo coding based on time-aligned signal components

A framework for flexible and efficient coding of general stereo audio signals is proposed. Methods based on the framework can be used together with an arbitrary single channel (mono) coder to achieve seamless transition from pure parametric stereo coding to waveform approximating coding as the bitrate is increased. The idea, based on sum-difference encoding of time-aligned signal components, is presented as a general framework. An example implementation is demonstrated to have the desired convergence properties towards transparent quality.