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

1. A method of processing video signals based on history based motion vector prediction, comprising:

configuring a merge candidate list based on a neighboring block to a current block, the merge candidate list including spatial merge candidates and a temporal merge candidate, the spatial merge candidates selected among a left neighboring block (A1), a bottom-left neighboring block (A0), a top-right neighboring block (B0), a top neighboring block (B1), and a top-left neighboring block (B2);

adding one or more history based merge candidates of the current block from a history based motion vector predictor candidate list to the merge candidate list based on that a number of merge candidates included in the merge candidate list is smaller than a first predetermined number;

adding a zero motion vector to the merge candidate list based on that the number of merge candidates included in the merge candidate list is smaller than a second predetermined number;

obtaining a merge index indicating a merge candidate used for inter prediction of the current block in the merge candidate list;

generating a prediction sample of the current block based on motion information of the merge candidate indicated by the merge index; and

updating the history based motion vector predictor candidate list based on the motion information,

wherein the step of adding the one or more history based merge candidates of the current block to the merge candidate comprises:

determining whether a specific spatial merge candidate included in the merge candidate list and at least one of a predetermined number of history based merge candidates included in the history based motion vector predictor candidate list have same motion information; and

adding the at least one of the history based merge candidates to the merge candidate list when it is determined that the specific spatial merge candidate and the at least one of the predetermined number of history based merge candidates have different motion information, and

wherein the specific spatial merge candidate is only a spatial candidate corresponding to the left neighboring block (A1) or the top neighboring block (B1), and the predetermined number is 2.

2. The method of claim 1 , wherein a size of the history based motion vector predictor candidate list is defined as 5 based on that a maximum number of the merge candidates in the merge candidate list is 6.

3. The method of claim 1 , wherein the history based motion vector predictor candidate list is defined to have a size same as a value obtained by subtracting one from a maximum number of the merge candidates in the merge candidate list.

4. A method of encoding video signals by an apparatus, comprising:

configuring a merge candidate list based on a neighboring block to a current block, the merge candidate list including spatial merge candidates and a temporal merge candidate, the spatial merge candidates selected among a left neighboring block (A1), a bottom-left neighboring block (A0), a top-right neighboring block (B0), a top neighboring block (B1), and a top-left neighboring block (B2);

adding one or more history based merge candidates of the current block from a history based motion vector predictor candidate list to the merge candidate list when a number of merge candidates included in the merge candidate list is smaller than a first predetermined number;

adding a zero motion vector to the merge candidate list when the number of merge candidates included in the merge candidate list is smaller than a second predetermined number;

generating a prediction sample of the current block according to an inter prediction method based on motion information of one of the merge candidates included in the merge candidate list;

generating a residual sample of the current block based on the prediction sample of the current block;

updating the history based motion vector predictor candidate list based on the motion information; and

generating a merge index indicating the one in the merge candidate list;

wherein the step of adding the one or more history based merge candidates of the current block to the merge candidate comprises:

determining whether a specific spatial merge candidate included in the merge candidate list and at least one of a predetermined number of history based merge candidates included in the history based motion vector predictor candidate list have same motion information; and

adding the at least of the history based merge candidate to the merge candidate list when it is determined that, the specific spatial merge candidate and the at least one of the predetermined number of history based merge candidates have different motion information, and

wherein the specific spatial merge candidate is only a spatial candidate corresponding to the left neighboring block (A1) or the top neighboring block (B1), and the predetermined number is 2.

5. A transmission method of a bitstream, comprising:

obtaining the bitstream, the bitstream generated by

configuring a merge candidate list based on a neighboring block to a current block, the merge candidate list including spatial merge candidates and a temporal merge candidate, the spatial merge candidates selected among a left neighboring block (A1), a bottom-left neighboring block (A0), a top-right neighboring block (B0), a top neighboring block (B1), and a top-left neighboring block (B2);

adding one or more history based merge candidates of the current block from a history based motion vector predictor candidate list to the merge candidate list when a number of merge candidates included in the merge candidate list is smaller than a first predetermined number;

adding a zero motion vector to the merge candidate list when the number of merge candidates included in the merge candidate list is smaller than a second predetermined number;

generating a prediction sample of the current block according to an inter prediction method based on motion information of one of the merge candidates included in the merge candidate list;

generating a residual sample of the current block based on the prediction sample of the current block;

updating the history based motion vector predictor candidate list based on the motion information; and

generating a merge index indicating the one in the merge candidate list; and

transmitting the bitstream,

wherein the step of adding the one or more history based merge candidates of the current block to the merge candidate comprises:

determining a specific spatial merge candidate included in the merge candidate list and at least one of a predetermined number of history based merge candidates included in the history based motion vector predictor candidate list have same motion information; and

adding the at least one of the history based merge candidate to the merge candidate list when it is determined that the specific spatial merge candidate and the at least one of the predetermined number of history based merge candidates have different motion information, and

wherein the specific spatial merge candidate is only a spatial candidate corresponding to the left neighboring block (A1) or the top neighboring block (B1), and the predetermined number is 2.