Quadrature mirror filter banks and method

摘要

M-channel pseudo-quadrature-mirror-filter (QMF) banks using a prototype filter having a linear-phase spectral-factor of a 2M.sup.th band filter. The overall transfer function of the analysis filter/synthesis filter system is a delay, and the aliasing cancellation has all the significant aliasing terms canceled. Consequently, the aliasing level at the output of the pseudo-QMF banks is comparable to the stopband attenuation of the prototype filter, with the error at the output of the analysis filter/synthesis filter system approximately equal to the aliasing error at the level of the stopband attenuation. The pseudo-QMF banks have the stopband attenuation of the analysis filters and thus synthesis filters of -100 dB. The resulting reconstruction error is also on the order of -100 dB. Optimization of the pseudo-QMF banks by a quadratic-constrained least-squares formulation converges very fast as both a cost function and constraints are quadratic functions with respect to unknown parameters, providing a much higher stopband attenuation compared to previous filter banks.