1. A method comprising: determining a set of macroblocks of a first video picture having corresponding x-y coordinates and motion vectors, the set of macroblocks including a first macroblock and a second macroblock, the first macroblock having a first x-coordinate and a first y-coordinate, the second macroblock having a second x-coordinate and a second y-coordinate; determining a transfer function that models a motion vector for each corresponding macroblock of the set of macroblocks based on the x-y coordinate of the corresponding macroblock, wherein determining the transfer function includes determining a first coefficient of the transfer function corresponding to the x-coordinates of the set of macroblocks; determining a second coefficient of the transfer function corresponding to the y-coordinates of the set of macroblocks; determining a first candidate motion vector for the first macroblock based upon the transfer function, wherein determining the first candidate motion vector includes multiplying the first coefficient by the first x-coordinate and multiplying the second coefficient by the first y-coordinate; first motion vector search based on the first candidate motion vector to determine a first motion vector of a third macroblock of a second video picture, wherein the first video picture has a different resolution than the second video picture; determining a second candidate motion vector for the second macroblock based upon the transfer function, wherein determining the second candidate motion vector includes multiplying the first coefficient by the second x-coordinate and multiplying the second coefficient by the second y-coordinate; implementing a first motion vector search based on the second candidate motion vector to determine a second motion vector of a fourth macroblock of the second video picture.