Method and apparatus for processing video signal based on history based motion vector prediction

An image encoding method performed by an image encoding apparatus, the image encoding method comprising:

• configuring a merge candidate list based on a spatial neighboring block and a temporal neighboring block of a current block;
• adding a history-based motion vector predictor (HMVP) candidate included in an HMVP candidate list storing HMVP candidates of the current block to the merge candidate list;
• generating a prediction sample of the current block based on motion information of a merge candidate within the merge candidate list;
• and
• generating a merge index indicating the merge candidate used for generating the prediction sample, into a bitstream,
• wherein the HMVP candidate is added to the merge candidate list, based on a result of comparing motion information of the HMVP candidate with motion information of predetermined spatial merge candidates among merge candidates within the merge candidate list,
• the predetermined spatial merge candidates include only a left neighboring spatial merge candidate and a top neighboring spatial merge candidate of the current block, and the left and top neighboring spatial merge candidates are the first two merge candidates in the merge candidate list, and
• wherein a maximum size of the HMVP candidate list is smaller than a maximum size of the merge candidate list.

A method of transmitting a bitstream generated by an image encoding method, the image encoding method comprising:

• configuring a merge candidate list based on a spatial neighboring block and a temporal neighboring block of a current block;
• adding a history-based motion vector predictor (HMVP) candidate included in an HMVP candidate list storing HMVP candidates of the current block to the merge candidate list;
• generating a prediction sample of the current block based on motion information of a merge candidate within the merge candidate list;
• and
• generating a merge index indicating the merge candidate used for generating the prediction sample, into the bitstream,
• wherein the HMVP candidate is added to the merge candidate list, based on a result of comparing motion information of the HMVP candidate with motion information of predetermined spatial merge candidates among merge candidates within the merge candidate list,
• the predetermined spatial merge candidates include only a left neighboring spatial merge candidate and a top neighboring spatial merge candidate of the current block, and the left and top neighboring spatial merge candidates are the first two merge candidates in the merge candidate list, and
• wherein a maximum size of the HMVP candidate list is smaller than a maximum size of the merge candidate list.