1. A method for compressing motion vectors of an unsynchronized picture belonging to a current layer in a video encoder based on a multilayer having at least the current layer and a lower layer, the method comprising: selecting a base picture for the unsynchronized picture; generating a predicted motion vector of the unsynchronized picture of the current layer from a motion vector of the base picture; subtracting the predicted motion vector from a motion vector of the unsynchronized picture; and encoding a result of subtracting, wherein the unsynchronized picture does not have a corresponding lower layer picture at a same temporal position.