Fast decomposition of filterbanks for the state-of-the-art audio coding
This letter derives fast decomposition for the quadrature mirror filterbanks (QMFs) of the low power spectral band replication (SBR) tools in the MPEG high efficiency advanced audio coding (HE AAC) decoder. In contrast with the standard method where computation-intensive matrix operations are employed in the QMF, the proposed method decomposes the matrix operations into conventional discrete cosine transform of type II and III (DCT-II and DCT-III) and simple permutations for easy implementation. The computational complexity can be also reduced effectively by using fast algorithms for DCT.