Enhancement of H.264/AVC for higher coding efficiency using motion estimation between reference frames

The skip mode and direct mode in H.264/AVC are very efficient and indispensable tools for coding moving objects in scenes because they do not need bits for vectors. However, in some cases, the predicted motion vectors of these modes are not accurate. Since the ratio of the skip mode and direct mode in B pictures is very high, especially in large sized sequences, it is very important to enhance the coding efficiency of these modes to develop a more efficient video coding method for HD- and over-HD-sized video contents. In this paper, a new coding mode for H.264/AVC, called advanced B skip mode, is proposed. In the process of the advanced B skip mode, the motion vector is predicted by motion estimation between reference frames. The accuracy of the vector prediction is greatly improved compared with prediction of using conventional B skip mode. Although this method requires decoder-side motion estimation, it can significantly improve the coding efficiency of video content. Experimental results of video coding with advanced B skip mode show average bit-rate reduction of 4.79% and maximum bit-rate reduction of 9.89%.