| 摘要 |
<p>A forward transform processing method for performing a modified discrete cosine transform. A block of N time domain input samples is multiplied by a forward transform window to provide a block of N processed samples which is transformed into a block of N/2 spectral coefficients by preprocessing the block of N processed samples to provide a block of N/4 complex numbers, transforming the block of N/4 complex numbers by the equivalent of a Fast Fourier Transform into a block of N/4 transformed complex numbers that is then post-processed to provide an output block of N/2 spectral coefficients in the frequency domain. The corresponding apparatus embodies the method just described. An inverse transform method for performing an inverse modified discrete cosine transform. A block of N/2 spectral coefficients is pre-processed to provide a block of N/4 frequency domain complex numbers, which is transformed into a block of N/4 time domain complex numbers by processing equivalent to a Fast Fourier Transform. The block of N/4 time domain complex numbers is post processed to provide a block of N/2 processed samples in the time domain, which is re-arrayed and multiplied by an inverse transform window to provide an output block of N samples in the time domain. The apparatus embodies the method just described. <IMAGE></p> |
