History-based motion vector prediction

A method of video decoding for a decoder, the method comprising:

• acquiring coded information of a current picture from a coded video bitstream, the current picture being segmented into a plurality of units, each unit being divided into a plurality of blocks, the plurality of blocks in each unit being arranged as a first grid, and the plurality of units being arranged as a second grid in the current picture;
• decoding, for one of the units, a current block of the plurality of blocks from the coded information using an entry from a history motion vector prediction (HMVP) buffer;
• updating the HMVP buffer with a motion vector of the decoded current block;
• determining whether the current block is a first block of a first unit of a current row of the second grid and whether a previously decoded block is a last block of a preceding row of the second grid;
• and
• when the current block is determined to be the first block of the first unit of the current row and the previously decoded block is determined to be the last block in the preceding row, resetting the HMVP buffer and copying contents of a row buffer into the HMVP buffer before the current block is decoded.

A method of video encoding for an encoder, the method comprising:

• acquiring a current picture, the current picture being segmented into a plurality of units, each unit being divided into a plurality of blocks, the plurality of blocks in each unit being arranged as a first grid, and the plurality of units being arranged as a second grid in the current picture;
• encoding, for one of the units, a current block of the plurality of blocks in a bitstream using an entry from a history motion vector prediction (HMVP) buffer;
• updating the HMVP buffer with a motion vector of the encoded current block;
• determining whether the current block is a first block of a first unit of a current row of the second grid and whether a previously encoded block is a last block of a preceding row of the second grid;
• and
• when the current block is determined to be the first block of the first unit of the current row and the previously encoded block is determined to be the last block in the preceding row, resetting the HMVP buffer and copying contents of a row buffer into the HMVP buffer before the current block is encoded.

A non-transitory computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to perform a method of encoding a bitstream, the method comprising:

• acquiring a current picture, the current picture being segmented into a plurality of units, each unit being divided into a plurality of blocks, the plurality of blocks in each unit being arranged as a first grid, and the plurality of units being arranged as a second grid in the current picture;
• encoding, for one of the units, a current block of the plurality of blocks in the bitstream using an entry from a history motion vector prediction (HMVP) buffer;
• updating the HMVP buffer with a motion vector of the encoded current block;
• determining whether the current block is a first block of a first unit of a current row of the second grid and whether a previously encoded block is a last block of a preceding row of the second grid;
• when the current block is determined to be the first block of the first unit of the current row and the previously encoded block is determined to be the last block in the preceding row, resetting the HMVP buffer and copying contents of a row buffer into the HMVP buffer before the current block is encoded;
• and
• transmitting the encoded bitstream.