ORTHOGONAL TRANSFORMER, ORTHOGONAL TRANSFORM METHOD, COMPUTER PROGRAM FOR ORTHOGONAL TRANSFORM, AND AUDIO DECODER

摘要

PROBLEM TO BE SOLVED: To provide an orthogonal transformer which is capable of reducing the computational complexity for transform from a signal in a frequency domain to a signal in a time-frequency domain.SOLUTION: An orthogonal transformer (16, 16') includes: an inverse exponential transform unit 22 which computes one of real components and imaginary components of quadrature mirror filter coefficients included in a first sub-section of a plurality of sub-sections into which a coefficient array including a plurality of quadrature mirror filter coefficients is divided so that values of basis functions are symmetrical, by multiply and accumulation of the basis function corresponding to the first sub-section and respective modified discrete cosine transform coefficients and computes the other of real components and imaginary components of quadrature mirror filter coefficients included in the first sub-section, and real components and imaginary components of quadrature mirror filter coefficients included in another sub-section by butterfly computation using computed values computed by the multiply and accumulation; and a coefficient adjustment unit 23 which computes each quadrature mirror filter coefficient by combining its real component and imaginary component.