| 摘要 |
<p>The present invention provides a method and apparatus for performing an inverse modified discrete cosine transform (IMDCT) on at least one block of spectral coefficients representing an information signal in the frequency domain. The IMDCT provides an IMDCT output including at least one block of processed samples in the time domain. The new and novel method of the present invention includes converting spectral coefficients in the block of spectral coefficients to provide a block of frequency domain processed complex samples and processing the block of frequency domain processed complex samples into the block of processed samples in the time domain. Further, the converting spectral coefficients into the frequency domain processed complex samples includes regrouping the spectral coefficients into an even data sequence and an odd data sequence of spectral coefficients, and continuing to regroup the even data sequence and odd data sequence of spectral coefficients until each data sequence includes only two spectral coefficients. Butterfly computations are also performed. The performing of the butterfly computations includes performing at least one complex multiplication and at least one complex addition, and limiting the number of complex multiplications of the butterfly computations by a factor of two by calculating a first set of exponential components, betaN/2,n,1, for n=0, 1, . . . , N/8, and setting a second set of exponential components, betaN/2,n+N/8,1, equal to betaN/2,n,1, for n=0, 1, . . . , N/8.</p> |
