Image decoding method and device thereof

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

obtaining a Block-based Delta Pulse Code Modulation (BDPCM) flag for a current block;

obtaining a BDPCM direction flag for the current block based on the BDPCM flag representing that BDPCM is applied to the current block; and

deriving a prediction sample of a target sample of the current block based on a prediction direction derived based on the BDPCM direction flag;

wherein an intra prediction mode of the prediction direction is derived based on the BDPCM direction flag as an intra prediction mode of the current block,

wherein the BDPCM direction flag represents a horizontal direction or a vertical direction as the prediction direction,

wherein based on the BDPCM being applied to the current block and the prediction direction for the current block being the vertical direction, residual information includes syntax elements for the target sample of the current block, and

wherein the syntax elements for the target sample represent a difference between a residual coefficient value of the target sample and a top residual coefficient value of the target sample.

2. The image decoding method of claim 1 , wherein based on the prediction direction being the horizontal direction, the prediction sample of the target sample is derived based on a left neighboring sample of the current block.

3. The image decoding method of claim 1 , wherein based on the prediction direction being the vertical direction, the prediction sample of the target sample is derived based on a top neighboring sample of the current block.

4. The image decoding method of claim 1 , wherein based on the prediction direction being the horizontal direction, a horizontal intra prediction mode is derived as the intra prediction mode of the current block, and

wherein based on the prediction direction being the vertical direction, a vertical intra prediction mode is derived as the intra prediction mode of the current block.

5. The image decoding method of claim 1 , wherein based on a value of the BDPCM direction flag being 0, the BDPCM direction flag represents the horizontal direction as the prediction direction,

wherein based on the value of the BDPCM direction flag being 1, the BDPCM direction flag represents the vertical direction as the prediction direction.

6. The image decoding method of claim 1 , wherein based on a value of the BDPCM flag being 1, the BDPCM direction flag represents that the BDPCM is applied to the current block and the BDPCM direction flag is present.

7. The image decoding method of claim 1 , wherein the derived intra prediction mode is used for prediction of a neighboring block of the current block.

8. An image encoding method, performed by an encoding apparatus, comprising:

deriving a prediction direction for a current block based on Block-based Delta Pulse Code Modulation (BDPCM);

deriving a prediction sample of a target sample of the current block based on the derived prediction direction;

encoding residual information of the current block; and

encoding a BDPCM flag representing that the BDPCM is applied to the current block and a BDPCM direction flag representing the prediction direction for the current block;

wherein an intra prediction mode of the prediction direction as an intra prediction mode of the current block is derived based on the BDPCM,

wherein the BDPCM direction flag represents a horizontal direction or a vertical direction as the prediction direction,

wherein based on the prediction direction for the current block being the vertical direction, the residual information includes syntax elements for the target sample of the current block, and

wherein the syntax elements for the target sample represent a difference between a residual coefficient value of the target sample and a top residual coefficient value of the target sample.

9. The image encoding method of claim 8 , wherein based on a value of the BDPCM flag being 1, the BDPCM flag represents that the BDPCM is applied to the current block and the BDPCM direction flag is present.

10. The image encoding method of claim 8 , wherein based on the prediction direction for the current block being the horizontal direction, the residual information includes syntax elements for the target sample of the current block, and

wherein the syntax elements for the target sample represent a difference between the residual coefficient value of the target sample and a left residual coefficient value of the target sample.

11. A non-transitory computer-readable storage medium storing a bitstream including the residual information, the Block-based Delta Pulse Code Modulation (BDPCM) flag, and the BDPCM direction flag encoded by the image encoding method of claim 8 .

12. A transmission method of data for image, the method comprising:

obtaining a bitstream of image information including residual information, a Block-based Delta Pulse Code Modulation (BDPCM) flag, and a BDPCM direction flag for a current block; and

transmitting the data including the bitstream of the image information including the residual information, the BDPCM flag and the BDPCM direction flag,

wherein the BDPCM flag represents that BDPCM is applied to the current block,

wherein the BDPCM direction flag represents a horizontal direction or a vertical direction as a prediction direction for the current block,

wherein an intra prediction mode of the prediction direction is derived as an intra prediction mode of the current block,

wherein based on the prediction direction for the current block being the vertical direction, the residual information includes syntax elements for a target sample of the current block, and

wherein the syntax elements for the target sample represent a difference between a residual coefficient value of the target sample and a top residual coefficient value of the target sample.