Forward transform processing apparatus and inverse processing apparatus for modified discrete cosine transforms, and method of performing spectral and temporal analyses including simplified forward and inverse orthogonal transform processing

摘要

A method for performing a simplified digital spectral analysis on a block of N samples representing an information signal in the time domain, in which the block of N samples is multiplied by a forward transform window to provide a block of N processed samples. The block of processed samples is digitally preprocessed to provide a block of N/4 complex numbers, which is orthogonally transformed, using digital processing equivalent of a Fast Fourier Transform, to provide a block of N/4 transformed complex numbers. The block of transformed complex numbers is then digitally post-processed to provide a block of N/2 spectral coefficients representing the information signal in the frequency domain. In a method of performing a simplified digital temporal analysis on a block of N/2 spectral coefficients representing the information signal in the frequency domain, the block of spectral coefficients is digitally pre- processed to provide a block of N/4 frequency domain complex numbers, which is orthogonally transformed into a block of N/4 time domain complex numbers by digital processing equivalent to a Fast Fourier Transform. The block of N/4 time domain complex numbers is digitally post processed to provide a block of N/2 processed time domain samples, which is re-arrayed and multiplied by an inverse transform window to provide a block of N samples representing the information signal in the time domain.