Design Of Near Perfect-Reconstruction Cosine Modulated Filter Banks

Quadrature mirror filtering (QMF) and pseudo-quadrature mirror filtering (PQMF) are techniques that have been widely used in subband coding of speech, subband coding of images, and others. The PQMF bank is also called the cosine-modulated filter (CMF) bank. It's obtained through a cosine modulation of a prototype lowpass filter. In general, CMF is preferred to QMF in practical design because CMF can be implemented using fast DCT techniques and the number of parameters to be optimized in the CMF is much smaller than that in the QMF.This paper discusses the design of filter banks, with emphasis on design of cosine modulated filter banks. It consists of several parts as follows:Part one discusses modulated banks, cosine-modulated bank, designing filter with interpolation, and an iterative algorithm. Then an efficient design of cosine-modulated filter banks is proposed. According to this method, the number of the parameters to be optimized is greatly reduced. It is very efficiency to design the prototype filter of uniform CMF with more channels. An example is given to illustrate the method.In part two, we research the designing filter with frequency-response masking and the designing nonuniform filter banks with merging the next banks of cosine-modulated filter banks. Based on the research above, we show an algorithm to design uniform and nonuniform cosine-modulated filter banks. The method is efficient for inheriting the virtue of iterative, frequency-response masking. We also show an example.Finally we show the summary of above work and forecast of future research.