1. A method of operating a video processor, comprising: receiving a first image data representing a first frame of a scene; dividing at least a central portion of the first frame into a plurality of j×k tiles, wherein each of j and k is an integer; identifying feature point candidates in the first image data; selecting a set of feature points within each specific tile based on the luminance variance σ2 of the specific tile; receiving a second image data representing a second frame of the scene; deriving feature point motion vectors between the first frame and the second frame corresponding to the identified feature; grouping the motion vectors into motion vector groups, wherein each group of motion vectors of similar motion characteristics corresponds to at least part of an object within the scene; and calculating the affine transform of each group of motion vectors, wherein the grouping motion vectors into motion vector groups is based on vector magnitude ratios and angular differences.