Two stage inter-frame prediction using pixel- and block-wise motion compensation

This paper proposes a method to improve the prediction accuracy of motion compensation (MC) in video coding using block-wise and pixel-wise motion with little additional information. In general MC, block-wise motion vectors (MVs) are computed by block matching (BM), but these are not always suitable for motions such as local scaling and deformation. To improve the accuracy of such motions, the proposed method estimates the pixel-wise motion precisely from two decoded frames with little additional information, and extrapolates the frame to be encoded using the pixel-wise motion and an interpolation method. This is first-stage MC. In second-stage MC, the encoder adaptively chooses the extrapolated or previous frames as a reference frame for each MC block. The block-wise MVs are then computed using BM to prevent loss of accuracy. Experimental results show that the proposed method outperforms BM for local scaling and deformation motions.