DCT-based subpixel motion estimation

Inter-pixel interpolation is required for most subpixel motion estimation schemes but it undesirably increases the overall complexity and data flow and deteriorates the estimation accuracy. We develop DCT-based techniques to estimate subpel motion at different desired levels of accuracy in the DCT domain without interpolation by establishing subpel sinusoidal orthogonal principles and showing that subpixel motion information is preserved in the DCT of a shifted signal under some conditions in the form of pseudo phases. Though applicable to other areas, the resulting algorithms from these techniques for video coding are flexible and scalable with very low complexity O(N²) compared to O(N⁴) for block matching methods. Importantly, DCT-based methods enable simplification of the heavily loaded feedback loop of conventional hybrid video coder design, resulting in a high-throughput, low-complexity fully DCT-based coder. Finally, simulation results show a comparable performance of the proposed algorithms with block matching methods