Patent ID: 7643556

Claim:
A method of deriving a motion vector of a bi-predictive block based on scaling a motion vector of a co-located block in a reference picture performed by a moving picture coding system, the method comprising: selecting, by the moving picture coding system, a list 0 motion vector of the co-located image block in a first reference picture for the bi-predictive image block as a motion vector for deriving motion vectors of the bi-predictive image block regardless of whether the co-located image block has a list 1 motion vector if the co-located image block has the list 0 motion vector; scaling, by the moving picture coding system, the selected motion vector of the co-located block in the reference picture based on a temporal distance between a current picture including the bi-predictive block and the reference picture referred by the co-located image block; deriving, by the moving picture coding system, the motion vector of the bi-predictive block based on the scaled motion vector of the co-located block.