GPM-based image coding method and device

1 . An image decoding method performed by a decoding apparatus,

the image decoding method comprising:

obtaining information related to a geometric partitioning mode (GPM) for a current block from a bitstream;

deriving partitions of the current block based on partition index information in the information related to the GPM, wherein the partitions include a first geometric partition and a second geometric partition;

deriving first prediction samples for the first geometric partition;

deriving second prediction samples for the second geometric partition;

generating prediction samples for the current block based on the first prediction samples and the second prediction samples; and

generating reconstructed samples based on the prediction samples for the current block,

wherein the information related to the GPM includes first enabled flag information related to whether a GPM is enabled and second enabled flag information related to whether the GPM based on an intra prediction is enabled, and

wherein based on a maximum number of merge candidates being equal to 1, the first enabled flag information is included in the information related to the GPM.

2 . The method of claim 1 , wherein based on a value of the first enabled flag information being equal to 1, the second enabled flag information is included in the information related to the GPM.

3 . The method of claim 1 , wherein based on a value of the first enabled flag information being equal to 1 and the maximum number of the merge candidates being greater than or equal to 2, the second enabled flag information is included in the information related to the GPM.

4 . The method of claim 3 , wherein based on the second enabled flag information not being included in the information related to the GPM,

a value of the second enabled flag information is derived as equal to 1 based on the maximum number of the merge candidates being less than 2, and the value of the first enabled flag information being equal to 1, and

the value of the second enabled flag information is derived as equal to 0 based on the maximum number of the merge candidates not being less than 2, and the value of the first enabled flag information being not equal to 1.

5 . The method of claim 1 , wherein based on the first enabled flag information and a maximum number of merge candidates, information related to a maximum number of GPM merge candidates is included in the information related to the GPM.

6 . The method of claim 5 , wherein a value of the information related to the maximum number of the GPM merge candidates has range of greater than or equal to 0 and less than or equal to (the maximum number of the merge candidates−(2−a value of the second enabled flag information)).

7 . The method of claim 6 , wherein based on a first case that a value of the first enabled flag information is equal to 1 and the maximum number of the merge candidates is greater than or equal to 3, the maximum number of the GPM merge mode candidates is derived as equal to (the maximum number of the merge candidates−the value of the information related to the maximum number of the GPM merge candidates),

wherein based on a second case that the value of the first enabled flag information is equal to 1 and the maximum number of the merge candidates is equal to 2, the maximum number of GPM merge mode candidates is derived as equal to 2,

wherein based on a third case that the value of the second enabled flag information is equal to 1 and the maximum number of the merge candidates is equal to 1, the maximum number of the GPM merge mode candidates is derived as equal to 1, and

wherein based on a case other than the first case, the second case and the third case, the maximum number of the GPM merge mode candidates is derived as equal to 0.

8 . The method of claim 6 , wherein based on a first case that a value of the first enabled flag information is equal to 1 and the maximum number of the merge candidates is greater than or equal to (3−the value of the second enabled flag information), the maximum number of the GPM merge mode candidates is derived as equal to (the maximum number of the merge candidates−the value of information related to the maximum number of the GPM merge candidates),

wherein based on a second case that the value of the first enabled flag information is equal to 1 and the maximum number of the merge candidates is (2−the value of the second enabled flag information), the maximum number of the GPM merge mode candidates is derived as equal to (2−the value of the second enabled flag information), and

wherein based on a case other than the first case and the second case, the maximum number of the GPM merge mode candidates is derived as equal to 0.

9 . The method of claim 5 , wherein based on a value of the first enabled flag information being equal to 1 and the maximum number of the merge candidates being greater than or equal to 3, the information related to the maximum number of the GPM merge candidates is included in the information related to the GPM.

10 . The method of claim 5 , wherein based on a value of the first enabled flag information being equal to 1 and the maximum number of the merge candidates being greater than or equal to (3−a value of the second enabled flag information), the information related to the maximum number of the GPM merge candidates may be included in information related to GPM.

11 . The method of claim 9 , wherein based on the value of the first enabled flag information being equal to 1 and a maximum number of GPM merge candidates being greater than or equal to 2, the second enabled flag information is included in the information related to the GPM.

12 . An image encoding method performed by an encoding apparatus, the image encoding method comprising:

deriving partitions for applying geometric partitioning mode (GPM) for a current block, wherein the partitions include a first geometric partition and a second geometric partition;

deriving first prediction samples for the first geometric partition;

deriving second prediction samples for the second geometric partition;

generating prediction samples for the current block based on the first prediction samples and the second prediction samples;

generating information related to the GPM for the current block; and

encoding image information including the information related to the GPM,

wherein the information related to the GPM includes first enabled flag information related to whether the GPM is enabled and second enabled flag information related to whether the GPM based on an intra prediction is enabled, and

wherein based on a maximum number of merge candidates being greater than or equal to 1, the first enabled flag information is included in the information related to the GPM.

13 . A transmission method of data for an image, the transmission method comprising:

obtaining a bitstream, wherein the bitstream is generated based on deriving partitions for applying geometric partitioning mode (GPM) for a current block, wherein the partitions include a first geometric partition and a second geometric partition, deriving first prediction samples for the first geometric partition, deriving second prediction samples for the second geometric partition, generating prediction samples for the current block based on the first prediction samples and the second prediction samples, generating information related to the GPM for the current block and generating the bitstream by encoding image information including the information related to the GPM; and

transmitting the data comprising the bitstream,

wherein the information related to the GPM includes first enabled flag information related to whether the GPM is enabled and second enabled flag information related to whether the GPM based on an intra prediction is enabled, and

wherein based on a maximum number of merge candidates being equal to 1, the first enabled flag information is included in the information related to the GPM.