Post-processing technique based on POCS for visual enhancement in HDTV images

We propose a post-processing technique based on the theory of projection on convex sets (POCS) to reduce the blocking artifacts in HDTV decoded images. In the block discrete cosine transform (BDCT) of HDTV, the image is divided into a grid of non-overlapped 8×8 blocks, and then each block is coded separately. A block which is located one pixel apart from the grid of BDCT will include the boundary of the original 8×8 block. If the blocking artifact is introduced along the block boundary, this block will have different frequency characteristics from that of the original block. Thus, a comparison of the frequency characteristics of these two overlapping blocks can detect the undesired high-frequency components mainly caused by the blocking artifact. By eliminating these undesired high-frequency components adaptively, a robust smoothing projection operator can be obtained. Simulation results with real image sequences indicate that the proposed method performs better than conventional algorithms