Video sequence processing

In an apparatus for motion vector assignment partial filters are applied to two or more regions 402-409 of pixel-to-pixel dissimilarity values between a plurality of video frames in a sequence. Outputs of the partial filters are combined to estimate motion between the plurality of video frames. The partial filters may take a maximum or a mean of the pixel difference values in the regions. The regions may define line segments or octants arranged radially around a pixel 401 for which the motion is to be determined. The outputs may be combined by a non-linear operation, for example taking the minimum from diametrically opposed regions. The apparatus may be used during motion searching and the filtering may assess how well-matched pixels in regions near a pixel are to regions near a point indicated by a candidate motion vector.