Calculates the forward discrete cosine transform (DCT) of all calling vector elements in-place. If vector Length is a power of 2, the function uses an efficient algorithm that is significantly faster than the direct computation of DCT. For different lengths this function uses the direct formulas given below; however, the symmetry of cosine function is taken into account, which allows to perform about half of the multiplication operations in the formulas. In the following definition of DCT, N=Vec.Length and V is the calling vector: 

IDCT, IDCT, FFT

DCT Method