IMAGE DECODING METHOD AND APPARATUS USING INTRA PREDICTION IN IMAGE CODING SYSTEM

1 . A decoding apparatus for image decoding, the decoding apparatus comprising:

a memory; and

at least one processor connected to the memory, the at least one processor configured to:

obtain image information for a current block;

derive an intra-prediction type for a current block among intra-prediction types based on the image information;

construct an intra-prediction mode candidate list of the current block by performing an intra-prediction mode candidate list construction process;

select an intra-prediction mode of the current block based on the intra-prediction mode candidate list after constructing the intra-prediction mode candidate list,

wherein the intra-prediction mode includes an intra planar mode, an intra DC mode or at least one intra angular mode; and

generate prediction samples of the current block based on the intra-prediction type and the intra-prediction mode,

wherein the intra-prediction types include a first intra-prediction type, a second intra-prediction type and a third intra-prediction type,

wherein, based on the intra-prediction type being the first intra-prediction type, the prediction samples are generated based on a first reference line which is a reference line adjacent to upper boundary or left boundary of the current block,

based on the intra-prediction type being the second intra-prediction type, the prediction samples are generated based on a second reference line not adjacent to the current block, and

based on the intra-prediction type being the third intra-prediction type, the prediction samples are generated based on intra sub partitions (ISP),

wherein,

a first intra-prediction mode candidate list for the first intra-prediction type using the first reference line;

a second intra-prediction mode candidate list for the second intra-prediction-type using the second reference line; and

a third intra-prediction mode candidate list for the third intra-prediction type to which the ISP is applied;

are identical,

wherein the image information includes intra luma reference index information specifying an intra prediction reference line index,

wherein, based on the intra luma reference index information having a value of 1, the second reference line is a reference line which is one sample away from the upper boundary or the left boundary of the current block,

wherein, based on the intra luma reference index information having a value of 0, the image information includes a flag for the ISP, and

wherein the flag for the ISP specifies whether the current block is partitioned.

2 . An encoding apparatus for image encoding, the encoding apparatus comprising:

a memory; and

at least one processor connected to the memory, the at least one processor configured to:

derive an intra-prediction type for a current block among intra-prediction types;

construct an intra-prediction mode candidate list of the current block by performing an intra-prediction mode candidate list construction process;

select an intra-prediction mode of the current block based on the intra-prediction mode candidate list after constructing the intra-prediction mode candidate list,

wherein the intra-prediction mode includes an intra planar mode, an intra DC mode or at least one intra angular mode;

generate prediction samples of the current block based on the intra-prediction type and the intra-prediction mode; and

encode image information including image information for the current block,

wherein the intra-prediction types include a first intra-prediction type, a second intra-prediction type and a third intra-prediction type,

wherein, based on the intra-prediction type being the first intra-prediction type, the prediction samples are generated based on a first reference line which is a reference line adjacent to upper boundary or left boundary of the current block,

based on the intra-prediction type being the second intra-prediction type, the prediction samples are generated based on a second reference line not adjacent to the current block, and

based on the intra-prediction type being the third intra-prediction type, the prediction samples are generated based on intra sub partitions (ISP),

wherein,

a first intra-prediction mode candidate list for the first intra-prediction type using the first reference line;

a second intra-prediction mode candidate list for the second intra-prediction-type using the second reference line; and

a third intra-prediction mode candidate list for the third intra-prediction type to which the ISP is applied;

are identical,

wherein the image information includes intra luma reference index information specifying an intra prediction reference line index,

wherein, based on the intra luma reference index information having a value of 1, the second reference line is a reference line which is one sample away from the upper boundary or the left boundary of the current block,

wherein, based on the intra luma reference index information having a value of 0, the image information includes a flag for the ISP, and

wherein the flag for the ISP specifies whether the current block is partitioned.

3 . An apparatus for storing data for an image, the apparatus comprising:

at least one processor configured to obtain a bitstream for the image, wherein the bitstream is generated based on deriving an intra-prediction type for a current block among intra-prediction types, constructing an intra-prediction mode candidate list of the current block by performing an intra-prediction mode candidate list construction process, selecting an intra-prediction mode of the current block based on the intra-prediction mode candidate list after constructing the intra-prediction mode candidate list, wherein the intra-prediction mode includes an intra planar mode, an intra DC mode or at least one intra angular mode, generating prediction samples of the current block based on the intra-prediction type and the intra-prediction mode, and encoding image information including image information for the current block,

a storage medium configured to store the bitstream,

wherein the intra-prediction types include a first intra-prediction type, a second intra-prediction type and a third intra-prediction type,

wherein, based on the intra-prediction type being the first intra-prediction type, the prediction samples are generated based on a first reference line which is a reference line adjacent to upper boundary or left boundary of the current block,

based on the intra-prediction type being the second intra-prediction type, the prediction samples are generated based on a second reference line not adjacent to the current block, and

based on the intra-prediction type being the third intra-prediction type, the prediction samples are generated based on intra sub partitions (ISP),

wherein,

a first intra-prediction mode candidate list for the first intra-prediction type using the first reference line;

a second intra-prediction mode candidate list for the second intra-prediction-type using the second reference line; and

a third intra-prediction mode candidate list for the third intra-prediction type to which the ISP is applied;

are identical,

wherein the image information includes intra luma reference index information specifying an intra prediction reference line index,

wherein, based on the intra luma reference index information having a value of 1, the second reference line is a reference line which is one sample away from the upper boundary or the left boundary of the current block,

wherein, based on the intra luma reference index information having a value of 0, the image information includes a flag for the ISP, and

wherein the flag for the ISP specifies whether the current block is partitioned.