CORRECTING DISCRETE COSINE TRANSFORMATION, INVERSE TRANSFORMING METHOD AND ITS DEVICE

摘要

PURPOSE:To provide a high-speed calculating method and its device for efficiently performing the calculation of MDCT in the case of compressing audio signals. CONSTITUTION:This device is provided with a first intermediate data generating part 1 for providing first intermediate data x2(n) (O<=n<=M-1) from the combination of specified two points in input sample data x(n) (0<=n<=2M-1) of two M points, a second intermediate data generating part 2 for providing M/2 pieces of second intermediate data z(n) (0<=n<=M/2-1) by dividing the intermediate data x2(n) into the first half and the latter half, an FTT executing part 3 for providing M/2 pieces of Fourier coefficients Z(k) (0<=k<=M/2-1) by performing high-speed Fourier transformation to the second intermediate data z(n) and an extension part 4 for providing the even-numbered spectrum and odd-numbered spectrum of the input data x(n) from the output Z(k) of the FFT executing means.