Method and device for processing video signal

1. A method of decoding a video, the method comprising:

generating a candidate list including a plurality of intra prediction mode candidates;

determining, based on the candidate list, an intra prediction mode of a current block;

deriving reference samples of the current block; and

obtaining prediction samples of the current block based on the intra prediction mode and the reference samples,

wherein when the intra prediction mode of the current block is determined as a bi-directional intra prediction mode, a prediction sample is derived by using a plurality of reference samples,

wherein the bi-directional intra prediction mode is defined as an independent intra prediction mode that has an index different from DC, Planar and directional prediction modes,

wherein under the bi-directional intra prediction mode, the prediction sample is derived by using one of a plurality of derivation methods, the plurality of derivation methods comprising a first derivation method and a second derivation method,

wherein, under the first derivation method, the plurality of reference samples includes a right reference sample which adjoins a right boundary of the current block, and

wherein, under the second derivation method, the plurality of reference samples includes a left reference sample and a top reference sample but does not include the right reference sample which adjoins the right boundary of the current block.

2. The method of claim 1 , wherein a selection of one among the plurality of derivation methods is based on whether reconstruction samples included in a right neighboring block are available or not.

3. The method of claim 2 , wherein the first derivation method is selectable when the reconstruction samples included in the right neighboring block are available, and the second derivation method is selectable when the reconstruction samples in the right neighboring block are not available.

4. The method of claim 1 , wherein, under the first derivation method, the prediction sample is obtained based on a first value obtained based on a weighted sum of the right reference sample and the left reference sample, and

wherein, under the second derivation method, the prediction sample is obtained based on a second value obtained based on a weighted sum of the left reference sample and the top reference sample.

5. The method of claim 4 , wherein, under the first derivation method, weights applied to the right reference sample and the left reference sample is determined based on a position of the prediction sample.

6. A method of encoding a video, the method comprising:

generating a candidate list including a plurality of intra prediction mode candidates;

determining, based on the candidate list, an intra prediction mode of a current block;

deriving reference samples of the current block; and

obtaining prediction samples of the current block based on the intra prediction mode and the reference samples,

wherein when the intra prediction mode of the current block is determined as a bi-directional intra prediction mode, a prediction sample is derived by using a plurality of reference samples,

wherein the bi-directional intra prediction mode is defined as an independent intra prediction mode that has an index different from DC, Planar and directional prediction modes,

wherein under the bi-directional intra prediction mode, the prediction sample is derived by using one of a plurality of derivation methods, the plurality of derivation methods comprising a first derivation method and a second derivation method,

wherein, under the first derivation method, the plurality of reference samples includes a right reference sample which adjoins a right boundary of the current block, and

wherein, under the second derivation method, the plurality of reference samples includes a left reference sample and a top reference sample but does not include the right reference sample which adjoins the right boundary of the current block.

7. The method of claim 6 , wherein a selection of one among the plurality of derivation methods is based on whether reconstruction samples included in a right neighboring block are available or not.

8. The method of claim 7 , wherein the first derivation method is selectable when the reconstruction samples included in the right neighboring block are available, and the second derivation method is selectable when the reconstruction samples in the right neighboring block are not available.

9. The method of claim 8 , wherein, under the first derivation method, the prediction sample is obtained based on a first value obtained based on a weighted sum of the right reference sample and the left reference sample, and

wherein, under the second derivation method, the prediction sample is obtained based on a second value obtained based on a weighted sum of the left reference sample and the top reference sample.

10. A non-transitory computer-readable medium for storing data associated with a video signal, comprising:

a data stream stored in the non-transitory computer-readable medium, the data stream being encoded by an encoding method which comprising:

generating a candidate list including a plurality of intra prediction mode candidates;

determining, based on the candidate list, an intra prediction mode of a current block;

deriving reference samples of the current block; and

obtaining prediction samples of the current block based on the intra prediction mode and the reference samples,

wherein when the intra prediction mode of the current block is determined as a bi-directional intra prediction mode, a prediction sample is derived by using a plurality of reference samples,

wherein the bi-directional intra prediction mode is defined as an independent intra prediction mode that has an index different from DC, Planar and directional prediction modes,

wherein under the bi-directional intra prediction mode, the prediction sample is derived by using one of a plurality of derivation methods, the plurality of derivation methods comprising a first derivation method and a second derivation method,

wherein, under the first derivation method, the plurality of reference samples includes a right reference sample which adjoins a right boundary of the current block, and

wherein, under the second derivation method, the plurality of reference samples includes a left reference sample and a top reference sample but does not include the right reference sample which adjoins the right boundary of the current block.