Pre- and Post-Shift Filtering for Blocking Removing in Downsizing Transcoding

When high-quality video is delivered via a bandwidth-limited network, one solution is to reduce the spatial resolution of the bitstream before transmission. Downsizing transcoding is adopted as an efficient tool to reduce the spatial resolution of the precoded bitstream. Since the downsizing process and the coding process both apply a low-pass filtering operation on the picture, the reconstructed video may result in serious blocking artifact. In this paper, pre- and post-shift filters are considered in the transcoding process. The block boundary is shifted between the downsizing process and the coding process. This reduces the blocking effect in downsizing transcoding. Experimental results show that the proposed scheme can efficiently remove the blocking effect without introducing high computation.