Patent ID: 7630500

Claim:
A method of processing a pair of input signals L(t) and R(t) representing left and right channels of a stereo audio signal, characterized by a predetermined spectral balance and predetermined spatial balance to form subband signals representative of N output channel signals o 1 (t), o 2 (t), . . . , o n (t), wherein N>2 and t is time, the output channel signals to be reproduced over spatially separated loudspeakers, said method comprising: generating a first subband signal representation of the signal L(t), said first subband signal representation containing a plurality of first subband frequency sample components L k (t) where k is an integer ranging from 1 to M; generating a second subband signal representation of the signal R(t), said second subband signal representation containing a plurality of second subband frequency sample components R k (t); and combining said frequency sample components of the input signals L(t) and R(t) according to an output construction rule o j,k (t)=f(L k (t),R k (t)) for k=1, 2, . . . , M and j=1, 2, . . . , N to provide the output subband signal representation for each of said plurality of output channel signals, each of said output subband signal representations containing a plurality of output subband signal components o j,k (t), wherein o j,k (t) represents the k th subband output signal component of the j th output channel signal, wherein the output construction rule establishes the following relationship for at least some of the subband signal components L k (t) and R k (t) and output subband signal components o j,k (t)  L k ⁡ ( t )  +  R k ⁡ ( t )  = ∑ j = 1 N ⁢ ⁢  o j , k ⁡ ( t )  and reproducing the N output channel signals with N output speakers while preserving said predetermined spectral balance and said predetermined spatial balance of said input signals.