Image/video coding method based on intra prediction involving parsing of MPM index, and apparatus thereof

1. An image decoding method performed by a decoding apparatus comprising:

receiving information about an intra prediction type of a current block through a bitstream;

deriving the intra prediction type of the current block as a specific intra prediction type based on the information about the intra prediction type;

acquiring information about an intra prediction mode of the current block from the bitstream;

configuring a most probable mode (MPM) list comprising candidate intra prediction modes of the current block based on neighboring blocks of the current block;

deriving the intra prediction mode of the current block based on the MPM list and the information about the intra prediction mode;

generating a predicted block of the current block by performing intra prediction based on the specific intra prediction type and the derived intra prediction mode;

acquiring residual information from the bitstream;

generating a residual block based on the residual information; and

generating a reconstructed block configuring a reconstructed picture based on the residual block and the predicted block derived based on the specific intra prediction type and the derived intra prediction mode,

wherein for the specific intra prediction type, the intra prediction is performed based on neighboring reference samples in a specific sample line which is not adjacent to a top boundary and a left boundary of the current block,

wherein, based on the intra prediction type representing the specific intra prediction type, the information about the intra prediction mode comprises MPM index information,

wherein based on the intra prediction type representing the specific intra prediction type, the MPM index information is parsed without parsing an MPM flag information from the bitstream, and

wherein, for generating the predicted block based on the specific intra prediction type and the derived intra prediction mode, neighboring reference samples used based on a height of the current block being greater than a width of the current block are different from neighboring reference samples used based on the width of the current block being greater than the height of the current block.

2. The image decoding method of claim 1 , wherein based on the intra prediction type representing a normal intra prediction type rather than the specific intra prediction type, the information about the intra prediction mode comprises the MPM flag information and the MPM index information.

3. The image decoding method of claim 1 , wherein based on the intra prediction type representing the specific intra prediction type, a value of the MPM flag information is derived as 1 without parsing the MPM flag information from the bitstream.

4. The image decoding method of claim 2 , wherein based on the intra prediction type representing the normal intra prediction type, the MPM flag information is parsed from the bitstream, and based on a value of the MPM flag information being equal to 1, the MPM index information is parsed.

5. The image decoding method of claim 1 , wherein the specific intra prediction type comprises: a linear interpolation intra prediction (LIP) type.

6. The image decoding method of claim 5 , wherein the information about the intra prediction type comprises: a LIP flag information, and

wherein based on a value of the LIP flag information being equal to 1, the LIP type is derived as the intra prediction type of the current block.

7. The image decoding method of claim 1 , wherein based on the intra prediction type representing the specific intra prediction type, the intra prediction mode of the current block is limited to one of candidate intra prediction modes within the MPM list.

8. The image decoding method of claim 1 , wherein based on the intra prediction type representing the normal intra prediction type and a value of the MPM flag information being equal to 0,

the information about the intra prediction mode further comprises: remaining intra mode information, and the intra prediction mode of the current block is derived as one of remaining intra prediction modes other than candidate intra prediction modes within the MPM list based on the remaining intra mode information.

9. An image encoding method performed by an image encoding apparatus comprising:

determining an intra prediction type of a current block as a specific intra prediction type;

generating information about the intra prediction type of the current block;

configuring a most probable mode (MPM) list comprising candidate intra prediction modes of the current block based on neighboring blocks of the current block;

deriving an intra prediction mode of the current block based on the MPM list;

generating a predicted block of the current block by performing intra prediction based on the specific intra prediction type and the derived intra prediction mode;

generating predicted information of the current block, the predicted information comprising the information about the intra prediction type and the information about the intra prediction mode;

deriving a residual block based on the predicted block;

generating residual information based on the residual block; and

outputting a bitstream by encoding image information comprising the predicted information and the residual information,

wherein the information about the intra prediction mode is generated based on the intra prediction type,

wherein based on the intra prediction type representing the specific intra prediction type, the information about the intra prediction mode comprises: an MPM index information,

wherein for the specific intra prediction type, the intra prediction is performed based on neighboring reference samples in a specific sample line which is not adjacent to a top boundary and a left boundary of the current block,

wherein based on the intra prediction type representing the specific intra prediction type, the MPM index information is configured to be parsed without parsing an MPM flag information from the bitstream, and

wherein, for generating the predicted block based on the specific intra prediction type and the derived intra prediction mode, neighboring reference samples used based on a height of the current block being greater than a width of the current block are different from neighboring reference samples used based on the width of the current block being greater than the height of the current block.

10. The image encoding method of claim 9 , wherein based on the intra prediction type representing a normal intra prediction type rather than the specific intra prediction type, the information about the intra prediction mode comprises: the MPM flag information and the MPM index information.

11. The image encoding method of claim 9 , wherein based on the intra prediction type representing the normal intra prediction type, one or more bits for each of the MPM flag information and the MPM index information are comprised in the bitstream.

12. The image encoding method of claim 9 , wherein based on the intra prediction type representing the specific intra prediction type, the intra prediction mode of the current block is searched only among the candidate intra prediction modes within the MPM list.

13. The image encoding method of claim 9 , wherein the specific intra prediction type comprises: a linear interpolation intra prediction (LIP) type.

14. The image encoding method of claim 13 , wherein the information about the intra prediction type comprises: an LIP flag information, and

wherein based on a value of the LIP flag information being equal to 1, the LIP type is applied to the current block.

15. The image encoding method of claim 9 , wherein based on the intra prediction type representing the specific intra prediction type, a bit for the MPM flag information of the current block is not comprised in the bitstream.

16. A non-transitory computer-readable storage medium storing a bitstream generated by a method, the method comprising:

determining an intra prediction type of a current block as a specific intra prediction type;

generating information about the intra prediction type of the current block;

configuring a most probable mode (MPM) list comprising candidate intra prediction modes of the current block based on neighboring blocks of the current block;

deriving an intra prediction mode of the current block based on the MPM list;

generating a predicted block of the current block by performing intra prediction based on the specific intra prediction type and the derived intra prediction mode;

generating predicted information of the current block, the predicted information comprising the information about the intra prediction type and the information about the intra prediction mode;

deriving a residual block based on the predicted block;

generating residual information based on the residual block; and

generating the bitstream by encoding image information comprising the predicted information and the residual information,

wherein the information about the intra prediction mode is generated based on the intra prediction type,

wherein based on the intra prediction type representing the specific intra prediction type, the information about the intra prediction mode comprises: an MPM index information,

wherein for the specific intra prediction type, the intra prediction is performed based on neighboring reference samples in a specific sample line which is not adjacent to a top boundary and a left boundary of the current block,

wherein based on the intra prediction type representing the specific intra prediction type, the MPM index information is configured to be parsed without parsing an MPM flag information from the bitstream, and

wherein, for generating the predicted block based on the specific intra prediction type and the derived intra prediction mode, neighboring reference samples used based on a height of the current block being greater than a width of the current block are different from neighboring reference samples used based on the width of the current block being greater than the height of the current block.