Fast implementation of MPEG audio coder using recursive formula with fast discrete cosine transforms

For cosine-modulated multirate subband filtering, we propose two implementation algorithms to reduce the computational complexity. First, we develop a recursive algorithm to further decrease the computation of polyphase subband filtering suggested by Nussbaumer and Vetterli (1984). Since the cosine modulation can be implemented by the discrete cosine transform (DCT), we combine both fast decimation-in-time (DIT) and decimation-in-frequency (DIF) DCT methods to further reduce the computation. Consequently, the recursive formula with the mixed fast-DCT method requires about 13.2% of the multiplications and 41.6% of the additions recommended by the ISO Std. ISO-IEC JTCI/SC2/WGI1.