Joint signaling method for motion vector difference
A method for encoding and decoding of motion vector difference for inter-predicting a video block is provided. The method includes receiving a coded video bitstream; extracting, from the coded video bitstream, a flag indicating whether an inter-predication mode is a JOINT_NEWMV mode for a current block in a current frame, the JOINT_NEWMV mode indicating that a first delta motion vector (MV) for a first reference frame from a reference list 0 and a second delta MV for a second reference frame from a reference list 1 are jointly signaled; in response to the flag indicating that the inter-predication mode is the JOINT_NEWMV mode, extracting a joint delta motion vector (MV) for the current block, and deriving the first delta MV and the second delta MV based on the joint delta MV; and decoding the current block based on the first delta MV and the second delta MV.
1. A method for encoding an inter-predicted video block, the method comprising:
receiving, by a device comprising a memory storing instructions and a processor in communication with the memory, a video bitstream;
generating, by the device based on the video bitstream, a flag indicating whether an inter predication mode is a JOINT_NEWMV mode for a current block in a current frame, wherein the JOINT_NEWMV mode indicates that a first delta motion vector (MV) for a first reference frame from a reference list 0 and a second delta MV for a second reference frame from a reference list 1 are jointly signaled, the inter predication mode is configured as the JOINT_NEWMV mode, and a first picture order count (POC) distance between the first reference frame and the current frame being equal to a second POC distance between the second reference frame and the current frame;
in response to the flag indicating that the inter predication mode is the JOINT_NEWMV mode, creating, by the device based on the video bitstream, a joint delta MV for the current block, the first delta MV and the second delta MV being derived based on the joint delta MV; and
encoding, by the device, the current block in the current frame based on the first delta MV and the second delta MV to obtain a coded video bitstream.
2. The method according to claim 1 , wherein:
the inter predication mode is one of compound reference modes; and
a syntax element is generated based on the video bitstream to indicate the inter predication mode.
3. The method according to claim 1 , wherein:
the JOINT_NEWMV mode is jointly signaled with at least one of the following: a NEAR_NEARMV mode, a NEAR_NEWMV mode, a NEW_NEARMV mode, a NEW_NEWMV mode, and a GLOBAL_GLOBALMV mode.
4. The method according to claim 1 , further comprising:
determining, by the device, a context for indicating the inter predication mode based on at least one of the following:
a first picture order count (POC) distance between the first reference frame and the current frame,
a second POC distance between the second reference frame and the current frame, or
a direction relationship of the first reference frame and the second reference frame relative to the current frame.
5. The method according to claim 1 , further comprising:
in response to the inter predication mode being the JOINT_NEWMV mode, performing, by the device, optical flow motion refinement on the current block.
6. The method according to claim 1 , further comprising:
generating, by the device based on the video bitstream, a second flag indicating whether optical flow motion refinement is performed to the JOINT_NEWMV mode; and
in response to the second flag indicating that the optical flow motion refinement is performed to the JOINT_NEWMV mode, performing, by the device, the optical flow motion refinement on the current block.
7. The method according to claim 1 , wherein:
generating, by the device based on the video bitstream, a second flag indicating whether the JOINT_NEWMV mode is applicable to the current block.
8. The method according to claim 6 , wherein:
the second flag is signaled in a high-level syntax element comprising at least one of the following: a sequence parameter set (SPS), a video parameter set (VPS), a picture parameter set (PPS), a picture header, a tile header, a slice header, a frame header, a coding tree unit (CTU) header, or a superblock header.
9. An apparatus for encoding an inter-predicted video block, the apparatus comprising:
a memory storing instructions; and
a processor in communication with the memory, wherein, when the processor executes the instructions, the processor is configured to cause the apparatus to:
receive a video bitstream;
generate, based on the video bitstream, a flag indicating whether an inter predication mode is a JOINT_NEWMV mode for a current block in a current frame, wherein the JOINT_NEWMV mode indicates that a first delta motion vector (MV) for a first reference frame from a reference list 0 and a second delta MV for a second reference frame from a reference list 1 are jointly signaled, the inter predication mode is configured as the JOINT_NEWMV mode, and a first picture order count (POC) distance between the first reference frame and the current frame being equal to a second POC distance between the second reference frame and the current frame;
in response to the flag indicating that the inter predication mode is the JOINT_NEWMV mode, create, based on the video bitstream, a joint delta MV for the current block, the first delta MV and the second delta MV being derived based on the joint delta MV; and
encode the current block in the current frame based on the first delta MV and the second delta MV to obtain a coded video bitstream.
10. The apparatus according to claim 9 , wherein:
the inter predication mode is one of compound reference modes; and
a syntax element is generated based on the video bitstream to indicate the inter predication mode.
11. The apparatus according to claim 9 , wherein:
the JOINT_NEWMV mode is jointly signaled with at least one of the following: a NEAR_NEARMV mode, a NEAR_NEWMV mode, a NEW_NEARMV mode, a NEW_NEWMV mode, and a GLOBAL_GLOBALMV mode.
12. The apparatus according to claim 9 , wherein, when the processor executes the instructions, the processor is configured to further cause the apparatus to:
determine a context for indicating the inter predication mode based on at least one of the following:
a first picture order count (POC) distance between the first reference frame and the current frame,
a second POC distance between the second reference frame and the current frame, or
a direction relationship of the first reference frame and the second reference frame relative to the current frame.
13. The apparatus according to claim 9 , wherein, when the processor executes the instructions, the processor is configured to further cause the apparatus to:
in response to the inter predication mode being the JOINT_NEWMV mode, perform optical flow motion refinement on the current block.
14. The apparatus according to claim 9 , wherein, when the processor executes the instructions, the processor is configured to further cause the apparatus to:
generate, based on the video bitstream, a second flag indicating whether optical flow motion refinement is performed to the JOINT_NEWMV mode; and
in response to the second flag indicating that the optical flow motion refinement is performed to the JOINT_NEWMV mode, perform the optical flow motion refinement on the current block.
15. The apparatus according to claim 9 , wherein:
generate, based on the video bitstream, a second flag indicating whether the JOINT_NEWMV mode is applicable to the current block.
16. A non-transitory computer readable storage medium storing instructions, wherein, when the instructions are executed by a processor, the instructions are configured to cause the processor to:
receive a video bitstream;
generate, based on the video bitstream, a flag indicating whether an inter predication mode is a JOINT_NEWMV mode for a current block in a current frame, wherein the JOINT_NEWMV mode indicates that a first delta motion vector (MV) for a first reference frame from a reference list 0 and a second delta MV for a second reference frame from a reference list 1 are jointly signaled, the inter predication mode is configured as the JOINT_NEWMV mode, and a first picture order count (POC) distance between the first reference frame and the current frame being equal to a second POC distance between the second reference frame and the current frame;
in response to the flag indicating that the inter predication mode is the JOINT_NEWMV mode, create, based on the video bitstream, a joint delta MV for the current block, the first delta MV and the second delta MV being derived based on the joint delta MV; and
encode the current block in the current frame based on the first delta MV and the second delta MV to obtain a coded video bitstream.
17. The non-transitory computer readable storage medium according to claim 16 , wherein:
the inter predication mode is one of compound reference modes; and
a syntax element is generated based on the video bitstream to indicate the inter predication mode.
18. The non-transitory computer readable storage medium according to claim 16 , wherein:
the JOINT_NEWMV mode is jointly signaled with at least one of the following: a NEAR_NEARMV mode, a NEAR_NEWMV mode, a NEW_NEARMV mode, a NEW_NEWMV mode, and a GLOBAL_GLOBALMV mode.
19. The non-transitory computer readable storage medium according to claim 16 , wherein, when the instructions are executed by a processor, the instructions are configured to further cause the processor to:
determine a context for indicating the inter predication mode based on at least one of the following:
a first picture order count (POC) distance between the first reference frame and the current frame,
a second POC distance between the second reference frame and the current frame, or
a direction relationship of the first reference frame and the second reference frame relative to the current frame.
20. The non-transitory computer readable storage medium according to claim 16 , wherein, when the instructions are executed by a processor, the instructions are configured to further cause the processor to:
in response to the inter predication mode being the JOINT_NEWMV mode, perform optical flow motion refinement on the current block.