Method and apparatus for inter prediction encoding and decoding

A method of encoding an image, the method comprising:

• constructing a first candidate list of a current block in the image, the first candidate list including a plurality of merge candidates;
• generating a first prediction block of the current block by performing inter prediction based on one of the plurality of merge candidates included in the first candidate list;
• generating a second prediction block of the current block based on a pre-defined intra prediction mode in an encoding apparatus, the pre-defined intra prediction mode being representative of a Planar mode;
• and
• generating a final prediction block of the current block based on a weighted sum of the first prediction block and the second prediction block,
• wherein a merge index specifying the one of the plurality of merge candidates included in the first candidate list is encoded into a bitstream,
• wherein a weight for the weighted sum is determined based on a prediction mode of a neighboring block of the current block,
• wherein the first candidate list includes a merge candidate having motion information of a previously encoded block,
• wherein the merge candidate having the motion information of the previously encoded block is derived from a second candidate list, and
• wherein the second candidate list is constructed based on motion information of previously decoded blocks.

A non-transitory computer-readable storage medium for storing a bitstream generated by an image encoding method, the image encoding method comprising:

• constructing a first candidate list of a current block in the image, the first candidate list including a plurality of merge candidates;
• generating a first prediction block of the current block by performing inter prediction based on one of the plurality of merge candidates included in the first candidate list;
• generating a second prediction block of the current block based on a pre-defined intra prediction mode in an encoding apparatus, the pre-defined intra prediction mode being representative of a Planar mode;
• and
• generating a final prediction block of the current block based on a weighted sum of the first prediction block and the second prediction block,
• wherein a merge index specifying the one of the plurality of merge candidates included in the first candidate list is encoded into the bitstream,
• wherein a weight for the weighted sum is determined based on a prediction mode of a neighboring block of the current block,
• wherein the first candidate list includes a merge candidate having motion information of a previously decoded block,
• wherein the merge candidate having the motion information of the previously encoded block is derived from a second candidate list, and
• wherein the second candidate list is constructed based on motion information of N previously encoded blocks.