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A Fast MDCT Implementation

The MDCT can be calculated using FFT. The naive approach, though, requires a 2n length FFT for a length n block, because of the odd transform. There are faster approaches though [10]. The MDCT can be rewritten as an odd-time odd-frequency discrete Fourier transform (O tex2html_wrap_inline1082 DFT)


[10] presents a fast algorithm for calculating






Thus, the MDCT can be calculated using only one n/4 point FFT and some pre- and post-rotation of the sample points. The IMDCT can be calculated in a similar way. See the code for a more detailed description.

Bosse Lincoln
Sat Mar 7 16:27:43 PST 1998