Radix-3 Algorithm for the Fast Computation of Forward and Inverse MDCT

The modified discrete cosine transform (MDCT) and the inverse MDCT (IMDCT) are two of the most computationally intensive operations in layer III of MPEG audio coding standard. In this letter, we present a radix-3 algorithm for efficiently computing the MDCT and the corresponding IMDCT of a sequence with length N=2times3
^m
. Comparison of the computational complexity with some known algorithms shows that the proposed approach reduces significantly the number of arithmetic operations