Systems and methods for performing inter prediction in video coding

1. A method of decoding video data, the method comprising:

decoding a merge subblock flag that specifies whether subblock-based inter prediction parameters for a coding unit are inferred from neighboring blocks and that determines whether a motion vector difference merge flag and a combination flag are to be decoded;

determining a value of the merge subblock flag;

decoding the motion vector difference merge flag after the value of the merge subblock flag is determined as being equal to zero and a value of a motion vector difference flag is determined as being equal to one; and

decoding the combination flag that specifies whether a combined inter-picture merge and intra-picture prediction is applied for the coding unit by using the merge subblock flag and a sequence parameter set (SPS) flag for the combined inter-picture merge and intra-picture prediction,

wherein:

the motion vector difference merge flag specifies that a prediction parameter with a motion vector difference is used, and

the motion vector difference flag specifies whether a merge mode with motion vector difference (MMVD) mode is enabled.

2. The method of claim 1 , further comprising:

decoding the combination flag that specifies whether the combined inter-picture merge and intra-picture prediction is applied for the coding unit after the value of the merge subblock flag is determined as being equal to zero and the SPS flag for the combined inter-picture merge and intra-picture prediction is determined as being equal to one.

3. A method of coding video data, the method comprising:

coding a merge subblock flag that specifies whether subblock-based inter prediction parameters for a coding unit are inferred from neighboring blocks and that determines whether a motion vector difference merge flag and a combination flag are to be coded;

determining a value of the merge subblock flag;

coding the motion vector difference merge flag after the value of the merge subblock flag is determined as being equal to zero and a value of a motion vector difference flag is determined as being equal to one; and

coding the combination flag that specifies whether a combined inter-picture merge and intra-picture prediction is applied for the coding unit by using the merge subblock flag and a sequence parameter set (SPS) flag for the combined inter-picture merge and intra-picture prediction,

wherein:

the motion vector difference merge flag specifies that a prediction parameter with a motion vector difference is used, and

the motion vector difference flag specifies whether a merge mode with motion vector difference (MMVD) mode is enabled.

4. The method of claim 3 , further comprising:

coding the combination flag that specifies whether the combined inter-picture merge and intra-picture prediction is applied for the coding unit after the value of the merge subblock flag is determined as being equal to zero and the SPS flag for the combined inter-picture merge and intra-picture prediction is determined as being equal to one.

5. A device comprising:

one or more processors; and

a storage device coupled to the one or more processors and storing computer-executable instructions which, when executed by at least one of the one or more processors, cause the device to:

decode a merge subblock flag that specifies whether subblock-based inter prediction parameters for a coding unit are inferred from neighboring blocks and that determines whether a motion vector difference merge flag and a combination flag are to be decoded;

determine a value of the merge subblock flag;

decode the motion vector difference merge flag after the value of the merge subblock flag is determined as being equal to zero and a value of a motion vector difference flag is determined as being equal to one; and

decode the combination flag that specifies whether a combined inter-picture merge and intra-picture prediction is applied for the coding unit by using the merge subblock flag and a sequence parameter set (SPS) flag for the combined inter-picture merge and intra-picture prediction,

wherein:

the motion vector difference merge flag specifies that a prediction parameter with a motion vector difference is used, and

the motion vector difference flag specifies whether a merge mode with motion vector difference (MMVD) mode is enabled.

6. The device of claim 5 , wherein computer-executable instructions, when executed by the at least one of the one or more processors, further cause the device to:

code the merge subblock flag that specifies whether the subblock-based inter prediction parameters for the coding unit are inferred from the neighboring blocks and that determines whether the motion vector difference merge flag and the combination flag are to be coded; and

code the motion vector difference merge flag after the value of the merge subblock flag is determined as being equal to zero and the value of the motion vector difference flag is determined as being equal to one; and

code the combination flag specifying whether the combined inter-picture merge and intra-picture prediction is applied for the coding unit by using the merge subblock flag and the SPS flag for the combined inter-picture merge and intra-picture prediction.

7. The device of claim 5 , wherein the computer-executable instructions, when executed by the at least one of the one or more processors, further cause the device to:

decode the combination flag that specifies whether the combined inter-picture merge and intra-picture prediction is applied for the coding unit after the value of the merge subblock flag is determined as being equal to zero and the SPS flag for the combined inter-picture merge and intra-picture prediction is determined as being equal to one.