Motion estimation using quad-tree phase correlation

We propose a quad-tree scheme for obtaining subpixel estimates of interframe motion in the frequency domain. Our scheme is based on phase correlation and uses key features of the phase correlation surface to control the partition of a parent block to four children quadrants. The partition criterion is applied iteratively until a target number of motion vectors or a target level of motion compensated prediction error is achieved or, ultimately, if no more than a single motion component per block can be identified. Our results show that our scheme provides a better level of adaptation to scene contents and outperforms fixed block size phase correlation in terms of total motion compensated prediction error for the same number of motion vectors and also in terms of number of motion vectors for the same level of motion compensated prediction error.