Image encoding/decoding method and device

1. A method of decoding an image, comprising:

dividing, based on a tree-based block partition, a higher coding block in the image into a plurality of coding blocks;

configuring a merge candidate list of a coding block;

deriving motion information of the coding block based on the merge candidate list and a merge candidate index; and

performing inter prediction of the coding block based on the derived motion information,

wherein the merge candidate list includes a plurality of merge candidates,

wherein, in response to a ratio of a width and a height of the coding block being less than a first threshold value and a number of samples belonging to the coding block being equal to a second threshold value, a plurality of partitions belonging to the coding block share the merge candidate list and the merge candidate index is signaled, for each of the plurality of partitions, from a bitstream, and

wherein the first and second threshold values are pre-defined in a decoding apparatus and are different from each other.

2. The method of claim 1 , wherein the plurality of merge candidates includes at least one of a spatial neighboring block or a temporal neighboring block of the coding block.

3. The method of claim 2 , wherein the coding block means a coding unit which is no longer partitioned into a smaller coding unit.

4. The method of claim 2 , wherein the tree-based block partition includes at least one of a quad-tree block partition, a binary-tree block partition or a ternary-tree block partition.

5. The method of claim 4 , wherein the first threshold value is 8.

6. The method of claim 5 , wherein the second threshold value is 64.

7. A method of encoding an image, comprising:

dividing, based on a tree-based block partition, a higher coding block in the image into a plurality of coding blocks;

configuring a merge candidate list of a coding block; and

performing inter prediction of the coding block based on motion information of the coding block, the motion information of the coding block being determined based on the merge candidate list,

wherein the merge candidate list includes a plurality of merge candidates,

wherein, in response to a ratio of a width and a height of the coding block being less than a first threshold value and a number of samples belonging to the coding block being equal to a second threshold value, a plurality of partitions belonging to the coding block share the merge candidate list and a merge candidate index is encoded, for each of the plurality of partitions, into a bitstream, and

wherein the first and second threshold values are pre-defined in an encoding apparatus and are different from each other.

8. A non-transitory computer-readable medium for storing data associated with a video signal, comprising:

a data stream stored in the non-transitory computer-readable medium, the data stream comprising a merge candidate index specifying a merge candidate in a merge candidate list of a coding block,

wherein the coding block is one of a plurality of coding blocks resulting from dividing a higher coding block based on a tree-based block partition,

wherein the merge candidate specified by the merge candidate index is used to derive motion information of the coding block,

wherein the merge candidate list includes a plurality of merge candidates,

wherein, in response to a ratio of a width and a height of the coding block being less than a first threshold value and a number of samples belonging to the coding block being equal to a second threshold value, a plurality of partitions belonging to the coding block share the merge candidate list and the merge candidate index is signaled, for each of the plurality of partitions, from the data stream, and

wherein the first and second threshold values are pre-defined and are different from each other.