1. A unified loop filter for video coding of an incoming signal, comprising: a pixel determining unit which determines the type of a pixel based on context characteristics of the pixel to be filtered; a similarity transforming unit which transforms a nonlinear image filtering portion into a nonlinear similarity-ordered statistics image filtering portion for filtering a reconstructed signal from an output of an encoder or a decoder; and an integrating unit which integrates the nonlinear similarity-ordered statistics image filtering portion generated by the similarity transforming unit with a linear image filtering portion such that the reconstructed signal which is filtered by the linear image filtering portion is also filtered by the nonlinear similarity-ordered statistics image filtering portion; wherein the linear image filtering portion improves the objective quality of the reconstructed signal and the nonlinear similarity-ordered statistics image filtering portion improves the subjective quality of the reconstructed signal; and wherein the transforming of a nonlinear image filtering portion into a nonlinear similarity-ordered statistics image filtering portion comprises transforming x i , a component in a first vector, into x′ i , a component in a second vector, by a relationship 
 x′ i =[1− f ( x c ,x i )]· x c +f ( x c ,x i )· x i where f(x c ,x i ) is a similarity function for comparing x i and a reference x c .