Post processing algorithm for reduction of blocking artifact in HDTV

In this paper, we propose a new post-processing method to reduce the blocking artifacts in digital high definition television (HDTV) decoded images. This algorithm performs the deblocking operation in two modes that are determined by number of edge pixels around the block boundary. The number of edge pixels is calculated by applying Sobel edge filter. An appropriate filtering operation is performed for each mode in both the horizontal and vertical directions. First, when the mode is associated with a smooth region, a strong filtering operation is applied because flat region are more sensitive to human visual system. In the second mode, adaptive filter that is based on the frequency information around the block boundaries is applied. Artifacts are reduced without introducing undesired distortion while preserving the original edge of image. Although the proposed approach is simple and operates on spatial domain, experimental results show that it improves both the subjective and objective quality of coded images with various features.