Adaptive deblocking filtering scheme for intra-coded slices in H.264/AVC

H.264/AVC applies an adaptive in-loop deblocking filter in order to remove blocking artifacts. The deblocking filter is adaptively controlled by using the boundary strength (BS) parameter. Although the filter achieves advantages in reducing blocking artifacts, there are two problems we should consider to improve the filtering performance. The first problem is that the filter applies just a strong and the strongest filter to filter intra coded blocks. The strong filter can remove blocking artifacts at smooth regions; however, it removes detail or sharpness of pictures at complex regions. The second problem is that H.264/AVC does not pay attention in removing corner outliers which appear when an edge of an object crosses a corner of a block. Therefore, corner outliers clearly appear and reduce the subjective quality of reconstructed pictures. In this paper, we propose an adaptive deblocking filter scheme which removes corner outliers, and which utilizes the intra prediction information of intra coded blocks to adaptively select the BS. Experimental results show that our proposed filter significantly enhances the subjective quality by removing blocking artifacts at smooth regions while maintaining details or sharpness at complex regions. In addition, the objective quality is improved, resulting in PSNR gains of up to 0.16 dB.