Fast half-pixel motion estimation based on a directional search and a linear model

As many fast integer-pixel motion estimation algorithms have become available, an integer-pixel motion vector can be found by examining less than 10 search points. Meanwhile, 8 half-pixel positions around the integer-pixel motion vector are to be examined for half-pixel motion estimation. Hence, it becomes more meaningful to reduce the computational complexity of half-pixel motion estimation. In this paper, we propose a fast half-pixel motion estimation algorithm, by combining a directional search and linear modeling of SAD curve. The proposed algorithm reduces the number of search points to 2.21 in average, while the image quality of reconstructed sequences in terms of PSNR is similar to existing fast half-pixel motion estimation algorithms. In addition, by adjusting a user-defined parameter, the proposed algorithm can significantly reduce the number of search points to 0.34 on average with a slight PSNR degradation.