Methods and devices for selectively applying bi-directional optical flow and decoder-side motion vector refinement for video coding

1 . A method for video decoding, comprising:

determining, in response to a current block being eligible for both applications of Decoder-side Motion Vector Refinement (DMVR) and Bi-Directional Optical Flow (BDOF), whether a pre-defined criterion is satisfied, wherein the pre-defined criterion comprises a sum of absolute differences (SAD) or a sum of squared differences (SSD) between list 0 predicted samples and list 1 predicted samples of the current block is less than a pre-defined threshold number; and

avoiding, in response to the pre-defined criterion being satisfied, applying BDOF to a subblock in the current block;

wherein the current block being eligible for an application of BDOF satisfies pre-defined conditions at least comprising:

the current block uses bi-directional prediction with a forward reference picture and a backward reference picture;

weighted prediction is not enabled;

a size of the current block is not equal to 4×8;

the current block is not coded as symmetric Motion Vector Differences (MVD) mode;

the current block is not coded as sub-block merge mode; and

the current block is not using different weights when averaging the predicted samples from list 0 and list 1.

2 . The method of claim 1 , wherein block size information is used for the pre-defined criterion.

3 . The method of claim 1 , wherein the current block being eligible for an application of DMVR satisfies pre-defined conditions comprising at least one of the followings:

the current block is not coded as affine mode;

the current block is not coded as sub-block merge mode;

a distance between a current picture and a forward reference picture and a distance between the current picture and a backward reference picture are same;

a height of the current block is equal to or greater than 8; or

the current block is not coded as Merge mode with Motion Vector Differences (MMVD) mode.

4 . The method of claim 1 , wherein the pre-defined criterion comprises whether a regular mode is selected for the current block.

5 . The method of claim 1 , wherein the pre-defined criterion comprises whether a coded merge index of the current block possesses a pre-defined mathematical property.

6 . The method of claim 1 , wherein the pre-defined criterion comprises whether a block size of the current block possesses a pre-defined mathematical property.

7 . A computing device, comprising:

one or more processors;

a non-transitory storage coupled to the one or more processors; and

a plurality of programs and a bitstream stored in the non-transitory storage that, when the plurality of programs executed by the one or more processors, cause the computing device to perform acts comprising:

determining, in response to a current block being eligible for both applications of Decoder-side Motion Vector Refinement (DMVR) and Bi-Directional Optical Flow (BDOF), whether a pre-defined criterion is satisfied, wherein the pre-defined criterion comprises a sum of absolute differences (SAD) or a sum of squared differences (SSD) between list 0 predicted samples and list 1 predicted samples of the current block is less than a pre-defined threshold number; and

avoiding, in response to the pre-defined criterion being satisfied, applying BDOF to a subblock in the current block;

wherein the current block being eligible for an application of BDOF satisfies pre-defined conditions at least comprising:

the current block uses bi-directional prediction with a forward reference picture and a backward reference picture;

weighted prediction is not enabled;

a size of the current block is not equal to 4×8;

the current block is not coded as symmetric Motion Vector Differences (MVD) mode;

the current block is not coded as sub-block merge mode; and

the current block is not using different weights when averaging the predicted samples from list 0 and list 1.

8 . The computing device of claim 7 , wherein block size information is used for the pre-defined criterion.

9 . The computing device of claim 7 , wherein the current block being eligible for an application of DMVR satisfies pre-defined conditions comprising at least one of the followings:

the current block is not coded as affine mode;

the current block is not coded as sub-block merge mode;

a distance between a current picture and a forward reference picture and a distance between the current picture and a backward reference picture are same;

a height of the current block is equal to or greater than 8; or

the current block is not coded as Merge mode with Motion Vector Differences (MMVD) mode.

10 . The computing device of claim 7 , wherein the pre-defined criterion comprises whether a regular mode is selected for the current block.

11 . The computing device of claim 7 , wherein the pre-defined criterion comprises whether a coded merge index of the current block possesses a pre-defined mathematical property.

12 . The computing device of claim 7 , wherein the pre-defined criterion comprises whether a block size of the current block possesses a pre-defined mathematical property.

13 . A method for storing a bitstream, comprising:

performing an encoding method to generate a bitstream; and

storing the bitstream,

wherein the encoding method comprises:

determining, in response to a current block being eligible for both applications of Decoder-side Motion Vector Refinement (DMVR) and Bi-Directional Optical Flow (BDOF), whether a pre-defined criterion is satisfied, wherein the pre-defined criterion comprises a sum of absolute differences (SAD) or a sum of squared differences (SSD) between list 0 predicted samples and list 1 predicted samples of the current block is less than a pre-defined threshold number; and

avoiding, in response to the pre-defined criterion being satisfied, applying BDOF to a subblock in the current block;

wherein the current block being eligible for an application of BDOF satisfies pre-defined conditions at least comprising:

the current block uses bi-directional prediction with a forward reference picture and a backward reference picture;

weighted prediction is not enabled;

a size of the current block is not equal to 4×8;

the current block is not coded as symmetric Motion Vector Differences (MVD) mode;

the current block is not coded as sub-block merge mode; and

the current block is not using different weights when averaging the predicted samples from list 0 and list 1.

14 . The method of claim 13 , wherein block size information is used for the pre-defined criterion.

15 . The method of claim 13 , wherein the current block being eligible for an application of DMVR satisfies pre-defined conditions comprising at least one of the followings:

the current block is not coded as affine mode;

the current block is not coded as sub-block merge mode;

a distance between a current picture and a forward reference picture and a distance between the current picture and a backward reference picture are same;

a height of the current block is equal or greater than 8; or

the current block is not coded as Merge mode with Motion Vector Differences (MMVD) mode.

16 . The method of claim 13 , wherein the pre-defined criterion comprises whether a regular mode is selected for the current block.

17 . The method of claim 13 , wherein the pre-defined criterion comprises whether a coded merge index of the current block possesses a pre-defined mathematical property.