Design of nearly perfect non uniform QMF filter banks

A method to design nonuniform QMF (quadrature-modulation filter) filter banks is presented. The method is based on polyphase quadrature filter techniques, and extends previous works on uniform QMF filter bands. The theory of operation is presented, showing that the original signal decomposed into unequally spaced subbands can be reconstructed with negligible distortion. A computationally efficient implementation is proposed, and some examples are discussed, exhibiting interesting characteristics of the method. It can be applied to speech and high-quality sound coding