Blocking artifact reduction method based on non-iterative POCS in the DCT domain

The post-processing method based on projections onto convex sets (POCS) has demonstrated good performance for blocking artifact reduction. However the iterative procedure in POCS requires a lot of computations, and would be infeasible for practical post-processing applications with real-time constraints. In this paper, we propose non-iterative post-processing method based on POCS in DCT domain for complexity reduction. In DCT domain POCS (D-POCS), the low-pass filtering (LPF) is performed in the DCT domain to remove the inverse DCT and forward DCT modules from POCS. Through the investigation of LPF in iterative POCS, we define kth order LPF which is equivalent to the LPF with k iterations. By combining DCT domain filtering and the kth order LPF concept, we define kth order DCT domain LPF. Simulation results show that the proposed D-POCS without iteration gives very close PSNR and subjective quality performance compared to the conventional POCS with iterations, while it requires much less computational complexity. If we take into account typical sparseness in DCT coefficients, the D-POCS method gives tremendous complexity reduction. Hence the proposed D-POCS would be an attractive method for practical real-time post-processing applications.