Pre-And Post-Shift Filtering for Removing Blocking Effects in Downsizing Transcoding

When the high definition video is delivered via a limited bandwidth network, one solution is to reduce the spatial resolution of the bitstream. Downsizing transcoding is adopted as an efficient tool to reduce the spatial resolution of the pre-coded bitstream. Since the downsizing process and the coding process apply a low pass filter to the picture, the reconstructed video may present 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 reduce the blocking effect without introducing high computation.