Variable Length Reconfigurable Algorithms and Architectures for DCT/IDCT Based on Modified Unfolded Cordic

Abstract: A coordinate rotation digital computer (CORDIC) based variable length reconfigurable DCT/IDCT algorithm and corresponding architecture are proposed. The proposed algorithm is easily to extend to the 2-point DCT/IDCT. Furthermore, we can easily construct the N-point DCT/IDCT with two N/2-pt DCTs/IDCTs based the proposed algorithm. The architecture based on the proposed algorithm can support several power-of-two transform sizes. To speed up the computation of DCT/IDCT without losing accuracy, we develop the modified unfolded CORDIC with the efficient carry save adder (CSA). The rotation angles of CORDIC used in proposed algorithm are arithmetic sequence. For convenience, we develop the architecture of N-point IDCT with the orthogonal property of DCT and IDCT transforms. The proposed architecture are modeled with MATLAB language and performed in DCT-based JPEG process, the experimental results show that the peak signal to noise ratio (PSNR) values of proposed architectures are higher than the existing CORDIC based architectures at both different quantization factors and different test images. Furthermore, the proposed architectures have higher regularity, modularity, computation accuracy and suitable for VLSI implementation.