Motion vector prediction for video coding

A decoding apparatus, comprising:

• one or more processors;
• and
• a non-transitory computer-readable medium storing program code that, when executed by the one or more processors, causes the one or more processors to perform operations comprising:
• parsing a bitstream of a video to obtain a syntax element, wherein the syntax element comprises at least an index of candidate motion information for a current block of the video and a list index indicating to construct a list of motion information of the current block based on candidate motion information obtained through block-based prediction or candidate motion information obtained through subblock-based prediction;
• constructing, based on the list index, the list of motion information for the current block, wherein the list of motion information is a first list of motion information which is a block-based candidate motion information list of the current block, or a second list of motion information which is a subblock-based candidate motion information list of one or more subblocks of the current block, wherein the block-based candidate motion information list includes at least one of motion information of a spatially neighboring coded block of the current block or motion information of a temporally neighboring coded block of the current block, and the subblock-based candidate motion information list includes a candidate motion information that is constructed in a motion model based affine model merge mode (AMM), in a complex merge mode, in an advanced temporal motion vector prediction (ATMVP), or in a combination of one or more of the AMM, the complex merge mode or the ATMVP, wherein a first feature value of the list index indicates to construct the first list for the current block, and a second feature value of the list index indicates to construct the second list for the current block;
• determining motion information from the constructed list of motion information for the current block based on the index of the candidate motion information;
• and
• generating predicted samples for the current block based on the motion information,
• wherein the list of motion information is the second list of motion information and constructing the second list of motion information comprises:
• determining a collocated reference picture of the current block;
• splitting the current block into M*N subblocks, M being different from N;
• for each subblock of the M*N subblocks,
• obtaining motion information of a center point location sample of a subblock unit that corresponds to the subblock and that is in the collocated reference picture, and
• converting the motion information of the center point location sample into motion information of the subblock through scaling;
• and
• obtaining the second list of motion information based on the motion information of the M*N subblocks.

An encoding method, comprising:

• constructing a first list of motion information for a current block in a video, wherein the first list of motion information is a block-based candidate motion information list of the current block, wherein the block-based candidate motion information list includes at least one of motion information of a spatially neighboring coded block of the current block or motion information of a temporally neighboring coded block of the current block;
• constructing a second list of motion information for the current block, wherein the second list of motion information is a subblock-based candidate motion information list of one or more subblocks of the current block, wherein the subblock-based candidate motion information list includes a candidate motion information that is constructed in a motion model based affine model merge mode (AMM), in a complex merge mode, in an advanced temporal motion vector prediction (ATMVP), or in a combination of one or more of the AMM, the complex merge mode or the ATMVP;
• determining candidate motion information for the current block from the first list of motion information and the second list of motion information;
• obtaining an identifier that is used to determine a candidate motion information list for the current block, the candidate motion information list comprising the candidate motion information for the current block, wherein the identifier indicates to construct the candidate motion information list for the current block based on candidate motion information obtained through block-based prediction or candidate motion information obtained through subblock-based prediction;
• obtaining an index of the candidate motion information in the candidate motion information list, wherein an inter prediction mode used for the current block is a merge mode, and when the identifier is a first feature value, the candidate motion information list is the first list, or when the identifier is a second feature value, the candidate motion information list is the second list;
• generating predicted samples for the current block based on the candidate motion information;
• and
• encoding the identifier and the index into a bitstream of the video,
• wherein the list of motion information is the second list of motion information and constructing the second list of motion information comprises:
• determining a collocated reference picture of the current block;
• splitting the current block into M*N subblocks, M being different from N;
• for each subblock of the M*N subblocks,
• obtaining motion information of a center point location sample of a subblock unit that corresponds to the subblock and that is in the collocated reference picture, and
• converting the motion information of the center point location sample into motion information of the subblock through scaling;
• and
• obtaining the second list of motion information based on the motion information of the M*N subblocks.

An encoding apparatus, comprising:

• one or more processors;
• and
• a non-transitory computer-readable medium storing program code that, when executed by the one or more processors, causes the one or more processors to perform operations comprising:
• constructing a first list of motion information for a current block in a video, wherein the first list of motion information is a block-based candidate motion information list of the current block, wherein the block-based candidate motion information list includes at least one of motion information of a spatially neighboring coded block of the current block or motion information of a temporally neighboring coded block of the current block;
• constructing a second list of motion information for the current block, wherein the second list of motion information is a subblock-based candidate motion information list of one or more subblocks of the current block, wherein the subblock-based candidate motion information list includes a candidate motion information that is constructed in a motion model based affine model merge mode (AMM), in a complex merge mode, in an advanced temporal motion vector prediction (ATMVP), or in a combination of one or more of the AMM, the complex merge mode or the ATMVP;
• obtaining an identifier that is used to determine a candidate motion information list for the current block, the candidate motion information list comprising candidate motion information of the current block, wherein the identifier indicates to construct the candidate motion information list for the current block based on candidate motion information obtained through block-based prediction or candidate motion information obtained through subblock-based prediction;
• obtaining an index of the candidate motion information in the candidate motion information list, wherein an inter prediction mode used for the current block is a merge mode, and when the identifier is a first feature value, the candidate motion information list is the first list, or when the identifier is a second feature value, the candidate motion information list is the second list;
• determining the candidate motion information of the current block from the first list of motion information and the second list of motion information;
• generating predicted samples for the current block based on the candidate motion information;
• and
• encoding the identifier and the index into a bitstream of the video,
• wherein the list of motion information is the second list of motion information and constructing the second list of motion information comprises:
• determining a collocated reference picture of the current block,
• splitting the current block into M*N subblocks, M being different from N;
• for each subblock of the M*N subblocks,
• obtaining motion information of a center point location sample of a subblock unit that corresponds to the subblock and that is in the collocated reference picture, and
• converting the motion information of the center point location sample into motion information of the subblock through scaling;
• and
• obtaining the second list of motion information based on the motion information of the M*N subblocks.