Matrix-based intra prediction device and method

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

receiving residual information;

receiving second flag information related to whether matrix-based intra prediction (MIP) is used for a current block based on first flag information related to whether the MIP is enabled;

receiving MIP mode information based on the second flag information;

generating intra prediction samples for the current block based on the MIP mode information;

deriving residual samples based on the residual information; and

generating reconstructed samples for the current block based on the intra prediction samples and the residual samples,

wherein the MIP mode information is index information related to an MIP matrix for the current block,

wherein the MIP matrix is derived based on a size of the current block and the index information,

wherein the intra prediction samples is generated based on the MIP matrix,

wherein a syntax element bin string for the MIP mode information is binarized by a truncated binarization method,

wherein a maximum length of the syntax element bin string is set to different three values based on the size of the current block, and

wherein based on a width and a height of the current block being 4, the maximum length has a largest value.

2. The image decoding method of claim 1 , wherein the generating of the intra prediction samples comprises:

deriving reduced boundary samples by downsampling reference samples adjacent to the current block;

deriving reduced prediction samples based on a multiplication operation of the reduced boundary samples and the MIP matrix; and

generating the intra prediction samples for the current block by upsampling the reduced prediction samples.

3. The image decoding method of claim 2 , wherein the reduced boundary samples are downsampled by averaging the reference samples, and

wherein the intra prediction samples are upsampled by linear interpolation of the reduced prediction samples.

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

deriving whether matrix-based intra prediction (MIP) is applied to a current block;

deriving intra prediction samples for the current block based on determining that the MIP is applied to the current block;

deriving residual samples for the current block based on the intra prediction samples;

generating residual information based on the residual samples; and

generating a bitstream by encoding the residual information and information on the MIP,

wherein the information on the MIP comprises first flag information related to whether the MIP is enabled, second flag information related to whether the MIP is applied to the current block and MIP mode information which is index information related to an MIP matrix for the current block,

wherein the MIP matrix is derived based on a size of the current block and the index information,

wherein the intra prediction samples is derived based on the MIP matrix,

wherein a syntax element bin string for the MIP mode information is binarized by a truncated binarization method,

wherein a maximum length of the syntax element bin string is set to different three values based on the size of the current block, and

wherein based on a width and a height of the current block being 4, the maximum length has a largest value.

5. The image encoding method of claim 4 , wherein the generating of the intra prediction samples comprises:

deriving reduced boundary samples by downsampling reference samples adjacent to the current block;

deriving reduced prediction samples based on a multiplication operation of the reduced boundary samples and an MIP matrix; and

generating the intra prediction samples for the current block by upsampling the reduced prediction samples.

6. The image encoding method of claim 5 , wherein the reduced boundary samples are downsampled by averaging the reference samples, and

wherein the intra prediction samples are upsampled by linear interpolation of the reduced prediction samples.

7. A non-transitory computer-readable digital storage medium that stores a bitstream generated by the image encoding method of claim 4 .

8. A transmitting method of data for an image, the method comprising:

obtaining a bitstream for the image, wherein the bitstream is generated based on deriving whether matrix-based intra prediction (MIP) is applied to a current block, deriving intra prediction samples for the current block based on determining that the MIP is applied to the current block, deriving residual samples for the current block based on the intra prediction samples, generating residual information based on the residual samples, and generating a bitstream by encoding the residual information and information on the MIP; and

transmitting the data comprising the bitstream,

wherein the information on the MIP comprises first flag information related to whether the MIP is enabled, second flag information related to whether the MIP is applied to the current block and MIP mode information which is index information related to an MIP matrix for the current block,

wherein the MIP matrix is derived based on a size of the current block and the index information,

wherein the intra prediction samples is derived based on the MIP matrix,

wherein a syntax element bin string for the MIP mode information is binarized by a truncated binarization method,

wherein a maximum length of the syntax element bin string is set to different three values based on the size of the current block, and

wherein based on a width and a height of the current block being 4, the maximum length has a largest value.