Improved algorithm for efficient computation of the forward and backward MDCT in MPEG audio coder

Britanak and Rao (see IEEE Signal Processing Lett., vol. 8, p. 48-51, Feb. 2001) recently proposed an efficient algorithm to implement the forward and backward modified discrete cosine transform (MDCT) in MPEG layer III. This algorithm employs discrete cosine transform of type II (DCT-II) and discrete sine transform of type II (DST-II) to compute the forward MDCT, and uses their inverses to compute the backward MDCT. The author presents an improved algorithm to implement the forward and backward NEXT in MPEG layer III. Notably, the proposed algorithm requires less calculation than Britanak and Rao's algorithm does. Furthermore, it employs the same module to compute both the forward and backward MDCT. Thus, when compared to the former algorithm, the proposed algorithm is implemented more easily.