Patent ID: 7065491

Claim:
A method for an inverse-modified discrete cosine transform and overlap-add for MPEG Layer3 audio signal decoding, comprising the steps of: applying an operation of the inverse-modified discrete cosine transform and overlap-add according to equation (1) to 32 sub-band samples of a compressed audio signal, wherein the equation (1) includes an inverse-modified discrete cosine transform: x ⁡ ( i ) = ∑ k = 0 n 2 - 1 ⁢ X ⁡ ( k ) * cos ⁢ ⁢ ( i , k ) ⁢ ⁢ 0 ≤ i ≤ n 4 - 1 ⁢ ⁢ and ⁢ ⁢ n 2 ⁢ ≤ i ≤ 3 ⁢ n 4 - 1 Wherein cos ⁡ ( i , k ) = cos ⁡ ( π 2 ⁢ n ⁢ ( 2 ⁢ i + 1 + n 2 ) ⁢ ( 2 ⁢ k + 1 ) ) , for I and k=0 to n−1 and an overlap-add: Z ( i )= x ( i )*win( i,p ) ⁢ Z ⁢ ⁢ ( n 2 - 1 - i ) = - x ⁡ ( i ) * win ⁢ ⁢ ( n 2 - 1 - i , p ) ⁢ ⁢ 0 ≤ i ≤ n 4 - 1 ⁢ Z ( i )= x ( i )*win( i,p ) ⁢ Z ⁢ ⁢ ( n - 1 - i ) = x ⁡ ( i ) * win ⁢ ⁢ ( n - 1 - i , p ) ⁢ ⁢ n 2 ⁢ ≤ i ≤ 3 ⁢ n 4 - 1 , where X(k) is the sub-band sample, Z(i) is the sub-band sample after process, when a window type is 0, 1, 3, n equals 36, and when the window type is 2, n equals 12; providing a dynamic window inverse-modified discrete cosine transform (DWIMDGT) module, wherein a multiplier-adder of the dynamic window inverse-modified discrete cosine transform module processes an operation of the inverse-modified discrete cosine transform, and an operation result of the inverse-modified discrete cosine transform is stored in a register stack of the dynamic window inverse-modified discrete cosine transform module; and using the multiplier-adder to operate the overlap-add operation, and an operation result of the overlap-add is stored in a dynamic window inverse-modified discrete cosine transform buffer memory.