Subpixel motion estimation in DCT domain
Ut-Va Koc, Kuo Juey R. Liu · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1996
Currently existing subpixel motion estimation algorithms require interpolation of inter-pixel values. However, it is shown in this paper that, by introducing the concept of pseudo phase shifts in DCT coefficients of a moving object's intensity, subpixel displacements can be estimated on two consecutive frames in DCT domain without interpolating inter-pixel values. Specifically, under a certain condition, subpixel motion information is preserved in the DCT coefficients of a shifted signal and extraction of this subpixel motion is based upon the subpel sinusoidal orthogonal principles. Furthermore, the resulted algorithms are flexible and scalable in terms of estimation accuracy and have very low computational complexity O(N2) compared to O(N4) for full search block matching approach and its subpixel versions. Above all, motion estimation in DCT domain instead of spatial domain simplifies the conventional standard-compliant video coder, especially the heavily loaded feedback loop in the conventional design, resulting in a fully DCT-based high-throughput standard-compliant video codec. In addition, the computation of pseudo phases is local and thus a highly parallel architecture is feasible for the DCT-based algorithms. In this paper, a set of experiments on a number of video sequences demonstrate that the DCT-based subpixel motion estimation schemes provide comparable performance against the block matching approach.