1. A method of video coding comprising: determining a measure of similarity between a prior frame and a current frame offset for a current macroblock by a motion vector having a fractional pel including determining a nearest integer pel of said fractional pel, calculating said measure of similarity for said nearest integer pel, determining at least one integer pel adjacent to said nearest integer pel, calculating said measure of similarity for each of said at least one adjacent integer pel, calculating coefficients of a quadratic model of said similarity measure versus pel location using said calculated measure of similarity of said nearest integer pel and said at least four adjacent integer pels, and estimating said measure of similarity for said motion vector including a fractional pel using said calculated coefficients of said quadratic model.