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 four integer pels adjacent to said nearest integer pel including a first adjacent integer pel immediately left of said nearest integer pel, a second adjacent integer pel immediately right of said nearest integer pel, a third adjacent integer pel immediately above said nearest integer pel and a fourth adjacent integer pel immediately below said nearest integer pel, calculating said measure of similarity of said nearest integer pel and each of said four adjacent integer pels, 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 four adjacent integer pels, wherein said quadratic model of said similarity measure versus pel location is: 
 S ( p )= C 1 x 2 +C 2 x+C 3 y 2 +C 4 y+C 5 where: x and y are spatial coordinate of said pel location; and S(p) is the measure of similarity; and C 1 , C 2 , C 3 , C 4 and C 5 are respective coefficients of the quadratic model of said similarity measure; and said step of calculating coefficients of a quadratic model of said similarity measure versus pel location includes: C 1 = S ⁡ ( p 1 ) - 2 ⁢ ⁢ S ⁡ ( p 2 ) - S ⁡ ( p 3 ) 2 C 2 = S ⁡ ( p 3 ) - S ⁡ ( p 1 ) 2 C 3 = S ⁡ ( p 4 ) - 2 ⁢ ⁢ S ⁡ ( p 2 ) - S ⁡ ( p 5 ) 2 C 4 = S ⁡ ( p 5 ) - S ⁡ ( p 4 ) 2 C 5 = S ⁡ ( p 2 ) where: S(p 1 ) is said similarity measure of said first adjacent integer pel; S(p 2 ) is said similarity measure of said nearest integer pel; S(p 3 ) is said similarity measure of said second adjacent integer pel; S(p 4 ) is said similarity measure of said third adjacent integer pel; and S(p 5 ) is said similarity measure of said fourth adjacent integer pel, and estimating said measure of similarity for said motion vector including a fractional pel using said calculated coefficients of said quadratic model.