A Fast Algorithm for Conversion from DCT Blocks to Integer Cosine Transform Blocks

Variants of the discrete cosine transform (DCT) have been selected for different image/video compression standards, and fast conversion algorithms between these transforms are needed. In this paper, conversion between an 8×8 DCT block, used in MPEG-2, and its corresponding 4×4 integer DCT blocks, used in H.264, is studied. By investigating the structure of the two transform kernels, a DCT decomposition scheme is adopted in development of the fast conversion algorithm. Analysis of the performance of this conversion scheme shows that the proposed scheme provides over 45% computation savings on multiplications, as compared to an existing scheme, while maintaining high fidelity in terms of PSNR.