A new z-scanning scheme for directional spatial prediction of AVS intra coding

In traditional directional spatial prediction based video coding standards such as H.264/AVC, MPEG4 and AVS, zigzag scan is the fixed scan pattern which designed to organize quantized transform coefficients in order to bring the high-frequency components as more as possible, so that the coefficients can be encoded more efficiently using the entropy encoding. However, zigzag scan cannot efficiently organize the transform coefficients due to different residual energy distribution produced by different intra prediction. To resolve this problem, in this paper, we propose a z-scan scheme to further improve intra coding efficiency for the AVS standard. In our method, traditional zigzag scan, horizontal z-scan, and vertical z-scan are used depending on the spatial prediction directions. It is relatively easy to implement our z-scan scheme into AVS codec without changing the syntax. Experimental results demonstrate that the z-scan scheme can remarkably reduce bitrates by approximately 2.1% compared with AVS codec using zigzag scan, while the PSNR of video sequences are maintained.