Temporal based subblock type motion vector predictor

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

• determining an initial temporal motion vector predictor (TMVP) of a first subblock in a current block in a current picture based on a subblock in a forward reference picture of the current picture and a subblock in a backward reference picture of the current picture, the subblock in the forward reference picture and the subblock in the backward reference picture being matched based on a subblock-based frame-rate up conversion (FRUC) mode, the first subblock being one of a plurality of subblocks in the current block, the current block being encoded in the subblock-based FRUC mode;
• determining, based on the initial TMVP of the first subblock in the plurality of subblocks in the current block and a motion vector offset (MVO), a TMVP of the first subblock in the plurality of subblocks in the current block;
• encoding, in a video bitstream, the first subblock in the current block based on the TMVP of the first subblock in the current block;
• and
• encoding, in the video bitstream, a syntax element indicating that the current block is encoded in the subblock-based FRUC mode.

A method of processing video data, comprising:

• processing a video bitstream of the video data according to a format rule, wherein
• the video bitstream includes a syntax element indicating that a current block in a current picture including a plurality of subblocks is coded in a subblock-based frame-rate up conversion (FRUC) mode;
• and
• the format rule specifies that
• a corresponding block of the current block is determined based on an offset vector, the offset vector indicating an offset between the current block and the corresponding block in the current picture;
• a temporal motion vector predictor (TMVP) of a first subblock in the corresponding block is determined based on a subblock in a forward reference picture of the current picture and a subblock in a backward reference picture of the current picture, the subblock in the forward reference picture and the subblock in the backward reference picture being matched using the subblock-based FRUC mode;
• and
• a TMVP of a subblock in the plurality of subblocks in the current block is determined based on the TMVP of the first subblock in the corresponding block.