A Unified Fast Algorithm for Cosine Modulated Filter Banks in Current Audio Coding Standards

Current audio coding standards, such as MPEG-I layers 1-3, MPEG-II layers 1-4, MPEG-IV, and AC-3, have adopted for compression various forms of the cosine modulated filter banks (CMFBs). It is demonstrated that all modulated cosine transforms can be divided into two modules-the permutation and discrete cosine transform. The derived discrete cosine transforms are either type II, type III, or type IV. A fast computing algorithm is proposed that will compute all three types of transforms uniformly. The new fast algorithm has good features with regard to regularity, complexity, and general applicability.