In one embodiment, the method includes selecting a list 0 motion vector of the co-located block in a first reference picture as the motion vector if the co-located block has the list 0 motion vector and a list 1 motion vector. The first reference picture is a type of reference picture permitted to be located temporally before or after the current picture. The method further includes 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, and deriving at least one motion vector of the bi-predictive block by applying a bit operation to the selected motion vector.