Patent ID: 7620675

Claim:
A method of audio analysis filter bank operation of a digital signal processor, comprising the steps of: (a) receiving in the digital signal processor a block of N audio samples where N is a positive integer; (b) including said block in an array of prior samples; (c) windowing said array of samples; (d) symmetric summing said array to form an N-vector S n for n=0, 1, . . . , N−1; (e) effecting a matrix multiplication and outputting V i , wherein V i =Σ 0≦n≦N−1 M i,n S n , for i=0, 1, . . . , N−1, where the matrix elements are M i,n =COS[πn(2i+1)/N]; and wherein said matrix multiplication of step (e) includes: (i) computing z R [n] for 0≦n≦N−1 by: z R [n]=c(n) S n cos[πn/2N] where c(n)=I for all n except c(0)=1/√2; (ii) computing z 1 [n] for 0≦n≦N−1 by: z 1 [n]=S n sin[πn/2N]; (iii) computing u[n] for 0≦n≦N−1 by: u[n]=(z R [n]+z R [N−n]/2 for 1≦n≦N−1 together with u[0]=z R [0]; (iv) computing v[n] for 0≦n≦N−1 by v[n]=(z 1 [n]−z 1 [M−n])/2 for 1≦n≦N−1 together with v[0]=0; (v) computing g[n] for 0≦n≦N−1 by g[n]=u[n]+v[n]; (vi) computing G[k] as the N-point DFT of g[n]; (vii) computing V 2k =Re{G[k]}−Im{G[k]} for 0≦k≦N/2−1; and (viii) computing V 2k+1 =Re{G[N−1−k]}−Im{G[N−1−k]} for 0≦k≦N/2−1.