1. A decoding method of a decoding device, comprising: obtaining, by the decoding device, a motion vector difference for a current block in a current picture from an input bitstream; obtaining, by the decoding device, a motion vector of a neighboring block of the current block, wherein the neighboring block is in the current picture and wherein the motion vector of the neighboring block is used to decode the neighboring block according to a reference picture of the neighboring block; interpolating, by the decoding device, the motion vector of the neighboring block of the current block based on a distance between the reference picture of the neighboring block and the current picture and a distance between a reference picture of the current block and the current picture to generate an interpolated motion vector, wherein the refrence picture of the neighboring block is different from the reference picture of the current block; predicting, by the decoding device, a motion vector of the current block based on the interpolated motion vector to generate a predicted motion vector; and adding, by the decoding device, the predicted motion vector and the motion vector difference to generate the motion vector of the current block.