1. A method of deriving at least one motion vectors of a bi-predictive block in a current picture from a motion vector of a co-located block in a first reference picture, comprising: selecting a list 0 motion vector of the co-located block in the first reference picture as the motion vector for deriving the at least one motion vector of the bi-predictive block regardless of whether the co-located block has a list 1 motion vector if the co-located block has the list 0 motion vector, the first reference picture being a type of reference picture permitted to be located temporally before or after the current picture; selecting the list 1 motion vector of the co-located block in the first reference picture if the co-located block only has the list 1 motion vector; scaling the selected motion vector based on temporal distance between the current picture and a second reference picture referred by the co-located block in the first reference picture; and deriving at least one motion vector of the bi-predictive block based on the scaled motion vector.