Method and apparatus for selectively encoding/decoding syntax elements, and apparatus and method for image encoding/decoding using same

A video decoding method using an inter-prediction, the method comprising:

• determining a motion vector of a current block to be decoded in a current picture;
• predicting pixels in the current block using the motion vector of the current block;
• extracting quantized transform coefficients by decoding a bitstream;
• reconstructing residual signals by inversely quantizing and then inversely transforming the quantized transform coefficients;
• and
• adding the predicted pixels and the reconstructed residual signals which correspond to the predicted pixels,
• wherein the determination of the motion vector of the current block comprises:
• obtaining a flag by decoding the bitstream, the flag indicating one among a plurality of modes for determining the motion vector of the current block;
• and
• when the flag indicates a first mode among the plurality of modes, performing a process comprising:
• deriving a set of candidate motion vectors from motion vectors of a plurality of neighboring blocks of the current block,
• selecting a candidate motion vector from the set of candidate motion vectors,
• determining the selected candidate motion vector to be a predicted motion vector of the current block, and
• reconstructing the motion vector of the current block by adding the predicted motion vector of the current block to a differential vector decoded from the bitstream.