An image decoding method for decoding a coded stream including an encoded picture, the method comprising the steps of:
- determining a motion vector of a target block to be decoded, by selecting a motion vector among motion vectors of candidate blocks including adjacent blocks adjacent to the target block to be decoded, according to coding mode information obtained from the coded stream;
- generating a prediction image by using the motion vector of the target block to be decoded and a reference picture, and
- generating a decoded image of the target block to be decoded by combining the prediction image with residual components which are decoded from the coded stream,
- wherein, in the motion vector selecting step of the motion vector determining step candidate blocks are selected among first blocks adjacent to the target
- block to be decoded in the same frame as the target block to be decoded and a second block located at the same position of the target block to be decoded in a different frame from the target block to be decoded,
- wherein, the motion vector determining step, by selecting a motion vector among motion vectors of candidate blocks including adjacent blocks adjacent to the target block to be decoded, according to coding mode information obtained from the coded stream,
- further comprising the steps of:
- excluding a block located on an upper side of the target block to be decoded in the first blocks from the candidate blocks based on a comparing process showing that the block located on the upper side of the target block to be decoded has the same motion vector as a block located on a left side of the target block in the first blocks,
- excluding a non-referenceable block in the first blocks from the candidate blocks in the case that the first blocks have a non-referenceable block, and
- adding another block or blocks to the candidate blocks, wherein the number of blocks to be added is changed based on the number of blocks that have been selected as candidate blocks,
- wherein if there are a plurality of blocks located on the left side of the target block, a motion vector of one block among the blocks located on the left side of the target block is selected as a motion vector to be a target of the comparing process before the comparing process in the motion vector determining step.