Partition, motion vector (MV) derivation of template-matching, and subblock MV derivation for subblock based MV predictor

A method of video encoding, comprising:

• determining a first collocated block in a first collocated picture based on a first displacement vector (DV) candidate of a current block in a current picture, the current block being encoded using a subblock-based temporal motion vector prediction (SbTMVP) mode, the first DV candidate corresponding to a first SbTMVP candidate;
• determining first motion information of a current template of the current block based on one or more pieces of motion information of (i) the first collocated block or (ii) at least one neighboring block of the first collocated block, the first motion information of the current template indicating one of a first reference template and a first subblock reference template in a first reference picture relative to the current template that is in the current picture;
• determining the one of the first reference template and the first subblock reference template associated with the first SbTMVP candidate in the first reference picture based on the first motion information of the current template, the first reference template and the current template having a same size, a size of the first subblock reference template being less than a size of the current template;
• and
• determining a first template matching (TM) cost based on the current template and the one of the first reference template and the first subblock reference template associated with the first SbTMVP candidate.

A method of processing visual media data, the method comprising:

• processing a bitstream of the visual media data according to a format rule, wherein
• the bitstream includes prediction information of a current block in a current picture from the bitstream, the prediction information indicating a subblock-based temporal motion vector prediction (SbTMVP) mode, and
• the format rule specifies that
• a first collocated block in a first collocated picture is determined based on a first displacement vector (DV) candidate of the current block, the first DV candidate corresponding to a first SbTMVP candidate,
• first motion information of a current template of the current block is determined based on one or more pieces of motion information of (i) the first collocated block or (ii) at least one neighboring block of the first collocated block, the first motion information of the current template indicating one of a first reference template and a first subblock reference template in a first reference picture relative to the current template that is in the current picture;
• the one of the first reference template and the first subblock reference template associated with the first SbTMVP candidate in the first reference picture is determined based on the first motion information of the current template, the first reference template and the current template having a same size, a size of the first subblock reference template being less than a size of the current template;
• and
• a first template matching (TM) cost is determined based on the current template and the one of the first reference template and the first subblock reference template associated with the first SbTMVP candidate.