Abstract

A unified architecture for implementing the modified cosine transforms of various cosine modulated filter banks in audio compression standards comprises a permutation module and a transform computing module. A modified cosine transform is computed by a pre-permutation followed by a discrete cosine transform and an inverse modified cosine transform is computed by a discrete cosine transform followed by a post-permutation. The discrete cosine transform computed in the unified architecture is selected from the group of type-II, type-III and type-IV cosine transforms. The computation of an N point discrete cosine transform is decomposed into a permutation-add stage, a sub-transform stage for computing two N/2 point discrete cosine transforms selected from the same group, and a combination stage. The architecture results in good regularity and general applicability as well as reduces complexity.

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