Adaptive Motion Vector Resolution Scheme for Enhanced Video Coding

In the state-of-the-art H.265/HEVC video coding standard, the motion vector is always fixed to be 1/4-pixel resolution for the entire video sequence regardless of the different video contents, which is not efficient for prediction coding. In this paper, we propose a frame level adaptive motion vector resolution selection scheme based on a rate-distortion model in terms of motion vector resolution. In the proposed rate-distortion model, the relationship between the distortion and the motion vector resolution is approximated with a linear model. And a rate model of motion vector is built, which reflects the relationship between the coding bits of motion vector and its value. With the proposed rate-distortion model, an optimal motion vector resolution minimizing the total rate-distortion cost will be selected for each frame. Experimental results show that the proposed scheme can achieve 1.5%, 1.3% and 2.5% BD-rate gain on average for Random Access, Lowdelay-B and Lowdelay-P configurations without complexity increment.