Patent ID: 8693697

Claim:
An encoder for use in a surround sound system wherein at least four audio input signals (FL, FR, RL, RR) representing an original sound field are encoded into two channel signals (L, R) and said encoded two channel signals are decoded into at least four audio output signals (FL′, FR′, RL′, RR′) corresponding to said four audio input signals, said encoder including: matrix structure connected to receive said four audio input signals for encoding said four input signals into two channel (L and R) output signals, said matrix structure being responsive to said four input signals for producing L and R output signals as follows: L =FL+ k FR+ j RL+ jk RR R =FR+ k FL− j RR− jk RL wherein k denotes a transformation or matrix constant having a value approximately 0.207 and j denotes a 90 degree phase shift.