Improved audio coding systems and methods using spectral component coupling and spectral component regeneration

An audio encoder discards spectral components of an input signal and uses channel coupling to reduce the information capacity requirements of an encoded signal. Channel coupling represents selected spectral components of multiple channels of signals in a composite form. An audio decoder synthesizes spectral components to replace the discarded spectral components and generates spectral components for individual channel signals from the coupled-channel signal. The encoder provides scale factors in the encoded signal that improve the efficiency of the decoder to generate output signals that substantially preserve the spectral energy of the original input signals.