Simplified design of low-delay oversampled NPR GDFT filterbanks

Abstract

We propose an efficient algorithm for designing theprototype filters of oversampled, near-perfect reconstruction(NPR), GDFT modulated filterbanks (FB) with arbitrary delay. Wedescribe simplified conditions for imposing NPR, posed on thefrequency response of the distortion transfer function and on thestopband attenuation of the prototype filters. Given the analysisprototype, we show that the minimization of the stopband energy ofthe synthesis prototype, subject to the simplified NPRconstraints, can be expressed as a convex optimization problem.Our algorithm consists of initialization with the prototype of anear-orthogonal FBwhich can also be designed via convexoptimizationand then successive optimization of the synthesisand analysis prototypes. We give design examples, discuss theproperties of the obtained FBs, and present synthetic echo controlexperiments. The presented results show that, for a given delay,our algorithm produces FBs with significantly better propertiesthan the near-orthogonal FBs.