There is provided a method and apparatus for encoding and decoding motion
vectors. Motion vectors are encoded through the steps of: (a) predicting
motion vectors of a type identical to that of a present block and
obtaining predictive motion vectors with respect to neighbor blocks
having motion vectors of a type different from that of the present block
among a plurality of neighbor blocks adjacent to the present block; (b)
calculating a representative value of the motion vectors of the type
identical to that of the present block from the motion vectors of the
neighbor blocks and the predictive motion vectors; (c) calculating a
difference value between the calculated representative value and the
motion vector of the present block; and (d) encoding the calculated
difference value. The motion vectors can be more efficiently encoded even
when they refer to different reference pictures.