Method and apparatus for deriving intra-prediction mode

1 . A method of decoding an image, the method comprising:

determining whether to perform intra-inter combination prediction for a current block based on a flag signaled from a bitstream; and

obtaining, in response to determining to perform the intra-inter combination prediction, a prediction block of the current block by performing the intra-inter combination prediction,

wherein the prediction block is obtained by weighted summing an intra prediction value of the intra-inter combination prediction and an inter prediction value of the intra-inter combination prediction,

wherein the intra prediction value of the intra-inter combination prediction is obtained using an intra prediction mode of the intra-inter combination prediction,

wherein the intra prediction mode is fixed to only a planar mode, not a directional prediction mode or direct current (DC) mode,

wherein, in response to a height of the current block being greater than or equal to 4, a width of the current block being greater than or equal to 4, and a value of an index of a reference sample line being 0, a prediction sample filtering for the intra prediction is determined to be applied, and

wherein, in response to the prediction sample filtering for the intra prediction value being determined to be applied, the intra prediction value is a filtered intra prediction value obtained by applying the prediction sample filtering to a value obtained using the intra prediction mode.

2 . The method of claim 1 ,

wherein the index with a value of 0 specifies a first reference sample line adjacent to the current block,

wherein the index with a value of 1 specifies a second reference sample line adjacent to the first reference sample line, and

wherein the index with a value of 2 specifies a third reference sample line adjacent to the second reference sample line.

3 . The method of claim 1 ,

wherein a type of the prediction sample filtering is determined based on the intra prediction mode among a plurality of filters.

4 . The method of claim 3 ,

wherein the plurality of filters includes a 2-tap filter and a 3-tap filter.

5 . The method of claim 4 ,

wherein, in response to the intra prediction mode being a planar mode, the type of the prediction sample filtering is determined as the 3-tap filter.

6 . A method of encoding an image, the method comprising:

determining whether to perform intra-inter combination prediction for a current block; and

obtaining, in response to determining to perform the intra-inter combination prediction, a prediction block of the current block by performing the intra-inter combination prediction,

wherein a flag indicates whether to perform the intra-inter combination prediction is encoded into a bitstream,

wherein the prediction block is obtained by weighted summing an intra prediction value of the intra-inter combination prediction and an inter prediction value of the intra-inter combination prediction,

wherein the intra prediction value of the intra-inter combination prediction is obtained using an intra prediction mode of the intra-inter combination prediction,

wherein the intra prediction mode is fixed to only a planar mode, not a directional prediction mode or direct current (DC) mode,

wherein, in response to a height of the current block being greater than or equal to 4, a width of the current block being greater than or equal to 4, and a value of an index of a reference sample line being 0, a prediction sample filtering for the intra prediction is determined to be applied, and

wherein, in response to the prediction sample filtering for the intra prediction value being determined to be applied, the intra prediction value is a filtered intra prediction value obtained by applying the prediction sample filtering to a value obtained using the intra prediction mode.

7 . A method of transmitting a bitstream, the method comprising:

determining whether to perform intra-inter combination prediction for a current block;

obtaining, in response to determining to perform the intra-inter combination prediction, a prediction block of the current block by performing the intra-inter combination prediction; and

transmitting the bitstream generated based on the prediction block,

wherein a flag indicates whether to perform the intra-inter combination prediction is encoded into the bitstream,

wherein the prediction block is obtained by weighted summing an intra prediction value of the intra-inter combination prediction and an inter prediction value of the intra-inter combination prediction,

wherein the intra prediction value of the intra-inter combination prediction is obtained using an intra prediction mode of the intra-inter combination prediction,

wherein the intra prediction mode is fixed to only a planar mode, not a directional prediction mode or direct current (DC) mode,

wherein, in response to a height of the current block being greater than or equal to 4, a width of the current block being greater than or equal to 4, and a value of an index of a reference sample line being 0, a prediction sample filtering for the intra prediction is determined to be applied, and

wherein, in response to the prediction sample filtering for the intra prediction value being determined to be applied, the intra prediction value is a filtered intra prediction value obtained by applying the prediction sample filtering to a value obtained using the intra prediction mode.