Efficient motion estimation utilizing quadrature filters

This contribution introduces a computationally-efficient scheme for phase-based motion estimation. The local phase for consecutive dyadic scales and six different directions is retrieved through a complex-valued subband decomposition. It is obtained by a successive use of a recursive Hilbert transformer and recursive power-complementary half-band filter pairs. The so-called approximately linear-phase recursive half-band filter proposed by Renfors and Saramäki is used as a start-up filter for generating both the Hilbert transformer and the half-band filter pairs. Experiments with synthetic image sequences demonstrate that by properly designing the start-up filter, the proposed technique provides, with a considerably reduced number of computations, a performance similar to that in a recently introduced method.