Patent ID: 6917913

Claim:
In a digital filter for sub-band synthesis, a method of performing an IDCT (Inverse Discrete Cosine Transform) process that generates time domain samples (V i ) from frequency domain samples (S k ) using prestored cosine coefficients, where i and k are integer values defining columns and rows respectively of a matrix of cosine coefficients, the method comprising: prestoring the cosine coefficients C(k−1,i) and C(k−2,i) for each column of the matrix; prestoring an adjustment value cos(E(i)) for each column of the matrix; and calculating the cosine coefficients for the remaining locations in the matrix using the prestored coefficients and the prestored adjustment values in accordance with the equation C ( k,i )=2 cos( E ( i ))* C ( k− 1, i )− C ( k− 2, i ).