A sound reproduction system has been developed, for converting signals on two input channels into surround signals on five or seven output channels and vice-versa. A decoder is included in the sound reproduction system which enhances the correlated component of the input signals in the desired direction...http://www.google.com/patents/US7386132?utm_source=gb-gplus-sharePatent US7386132 - 5-2-5 matrix encoder and decoder system
