One of the Fast DSP-based inverse MDCT algorithm
Liu Ruoheng · Journal of Tsinghua University(Science and Technology) · 2000
Modified discrete cosine transform (MDCT) is widely used in audio compression, such as the MPEG audio layer III codec. For the MDCT algorithm on a fixed point digital signal processor (DSP), a butterfly operation of inverse MDCT was proposed to reduce the computational time and memory requirements. The 2 M length inverse MDCT algorithm was derived in the form of a butterfly computation with M /2 points DFT and M points windowing. This fast algorithm operating in ADSP 2181 has at least 66% less instructions and 50% less memory space then the inverse MDCT described in ISO/IEC 11172 3.