Image decoding method comprising generating prediction samples by applying determined prediction mode, and device therefor

1. An image decoding method performed by a decoding apparatus, the image decoding method comprising:

acquiring image information including inter prediction mode information and residual information through a bitstream;

generating residual samples based on the residual information;

generating prediction samples of a current block by applying a prediction mode determined based on the inter prediction mode information; and

generating reconstructed samples based on the prediction samples and the residual samples,

wherein the inter prediction mode information includes at least one of a first flag related to whether a subblock merge mode is applied, a second flag related to whether a regular merge mode is applied, a third flag related to whether a merge mode with motion vector difference (MMVD) is applied or a fourth flag related to whether a combined inter-picture merge and intra-picture prediction (CIIP) mode is applied,

wherein a parsing order of the second flag related to whether the regular merge mode is applied precedes a parsing order of the third flag related to whether the MMVD is applied and a parsing order of the fourth flag related to whether the CIIP mode is applied,

wherein based on the CIIP mode being not enabled, a partitioning prediction mode in which prediction is performed by dividing the current block into two partitions being not enabled, a value of the first flag being equal to 0 and a value of the third flag being equal to 0,

whether a maximum number of merging candidate is greater than a specific value is determined,

wherein, based on the CIP mode being not enabled, the partitioning prediction mode being not enabled, the value of the first flag being equal to 0, the value of the third flag being equal to 0 and the maximum number of merging candidate being not greater than the specific value,

merge index information indicating one of merge candidates included in a merge candidate list is not obtained, and

wherein, based on the merge index information being not obtained, a firstly-ordered merge candidate in a merge candidate list is used for generating the prediction samples.

2. The image decoding method of claim 1 , wherein

a flag enabling or disabling the partitioning prediction mode is included in a sequence parameter set (SPS) of the image information.

3. The image decoding method of claim 1 , wherein

the partitioning prediction mode is available to the current block based on a value of an enabled flag for the partitioning prediction mode being equal to 1, a slice type is equal to B, a value of the second flag being equal to 0, the value of the first flag being equal to 0, the value of the third flag being equal to 0.

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

determining an inter prediction mode of a current block and generating inter prediction mode information indicating the inter prediction mode;

generating prediction samples of the current block based on the determined prediction mode;

generating residual information based on residual samples for the current block; and

encoding image information including the inter prediction mode information and the residual information,

wherein the inter prediction mode information includes at least one of a first flag related to whether a subblock merge mode is applied, a second flag related to whether a regular merge mode is applied, a third flag related to whether a merge mode with motion vector difference (MMVD) is applied or a fourth flag related to whether a combined inter-picture merge and intra-picture prediction (CIIP) mode is applied,

wherein a parsing order of the second flag related to whether the regular merge mode is applied precedes a parsing order of the third flag related to whether the MMVD is applied and a parsing order of the fourth flag related to whether the CIIP mode is applied,

wherein based on the CIIP mode being not enabled, a partitioning prediction mode in which prediction is performed by dividing the current block into two partitions being not enabled, a value of the first flag being equal to 0 and a value of the third flag being equal to 0,

whether a maximum number of merging candidate is greater than a specific value is determined,

wherein, based on the CIP mode being not enabled, the partitioning prediction mode being not enabled, the value of the first flag being equal to 0, the value of the third flag being equal to 0 and the maximum number of merging candidate being not greater than the specific value,

merge index information indicating one of merge candidates included in a merge candidate list is not obtained, and

wherein, based on the merge index information being not obtained, a firstly-ordered merge candidate in a merge candidate list is used for generating the prediction samples.

5. The image encoding method of claim 4 , wherein

a flag enabling or disabling the partitioning prediction mode is included in a sequence parameter set (SPS) of the image information.

6. The image encoding method of claim 4 , wherein

the partitioning prediction mode is available to the current block based on a value of an enabled flag for the partitioning prediction mode being equal to 1, a slice type is equal to B, a value of the second flag being equal to 0, the value of the first flag being equal to 0, the value of the third flag being equal to 0.

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

determining an inter prediction mode of a current block and generating inter prediction mode information indicating the inter prediction mode;

generating prediction samples of the current block based on the determined prediction mode;

generating residual information based on residual samples for the current block; and

encoding image information to generate the bitstream, wherein the image information includes the inter prediction mode information and the residual information,

wherein the inter prediction mode information includes at least one of a first flag related to whether a subblock merge mode is applied, a second flag related to whether a regular merge mode is applied, a third flag related to whether a merge mode with motion vector difference (MMVD) is applied or a fourth flag related to whether a combined inter-picture merge and intra-picture prediction (CIIP) mode is applied,

wherein a parsing order of the second flag related to whether the regular merge mode is applied precedes a parsing order of the third flag related to whether the MMVD is applied and a parsing order of the fourth flag related to whether the CIIP mode is applied,

wherein based on the CIIP mode being not enabled, a partitioning prediction mode in which prediction is performed by dividing the current block into two partitions being not enabled, a value of the first flag being equal to 0 and a value of the third flag being equal to 0,

whether a maximum number of merging candidate is greater than a specific value is determined,

wherein, based on the CIIP mode being not enabled, the partitioning prediction mode being not enabled, the value of the first flag being equal to 0, the value of the third flag being equal to 0 and the maximum number of merging candidate being not greater than the specific value,

merge index information indicating one of merge candidates included in a merge candidate list is not obtained, and

wherein, based on the merge index information being not obtained a firstly-ordered merge candidate in a merge candidate list is used for generating the prediction samples.

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

obtaining a bitstream for the image, wherein the bitstream is generated based on determining an inter prediction mode of a current block and generating inter prediction mode information indicating the inter prediction mode, generating prediction samples of the current block based on the determined prediction mode, generating residual information based on residual samples for the current block, and encoding image information including the inter prediction mode information and the residual information; and

transmitting the data comprising the bitstream,

wherein the inter prediction mode information includes at least one of a first flag related to whether a subblock merge mode is applied, a second flag related to whether a regular merge mode is applied, a third flag related to whether a merge mode with motion vector difference (MMVD) is applied or a fourth flag related to whether a combined inter-picture merge and intra-picture prediction (CIIP) mode is applied,

wherein a parsing order of the second flag related to whether the regular merge mode is applied precedes a parsing order of the third flag related to whether the MMVD is applied and a parsing order of the fourth flag related to whether the CIIP mode is applied,

wherein based on the CIIP mode being not enabled, a partitioning prediction mode in which prediction is performed by dividing the current block into two partitions being not enabled, a value of the first flag being equal to 0 and a value of the third flag being equal to 0,

whether a maximum number of merging candidate is greater than a specific value is determined,

wherein, based on the CIIP mode being not enabled, the partitioning prediction mode being not enabled the value of the first flag being equal to 0, the value of the third flag being equal to 0 and the maximum number of merging candidate being not greater than the specific value,

merge index information indicating one of merge candidates included in merge candidate list is not obtained, and

wherein, based on the merge index information being not obtained, a firstly-ordered merge candidate in a merge candidate list is used for gene ting the prediction samples.