An Improved Motion Estimation Algorithm Using Complex Wavelets

This paper describes some improvements to our hierarchical wavelet-based algorithm for estimating motion in digital video [1]. The algorithm uses a separable Discrete Wavelet Transform (DWT) to analyse each frame into a multiresolution pyramid of subimages. Our analysis filters are Gabor-like (complex valued), so each subband at a given level of the pyramid contains information from a distinct spatial orientation. Starting at the coarsest (most sparsely sampled) level, our algorithm produces a single field of motion estimates from the oriented subimages at that level. Accompanying each motion estimate is a directionally dependent confidence measure. The estimate field is then progressively refined by incorporating the finer level subimages, using a standard coarse-to-fine control strategy. This paper describes an iterative strategy including a new interpolation scheme which increases accuracy at a given level, and a curvature correction method which improves the propagation of estimate..