Image decoding method using BDPCM and apparatus thereof

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

• determining whether Block-based Delta Pulse Code Modulation (BDPCM) is enabled for a chroma block and a luma block;
• generating a BDPCM enabled flag indicating whether the BDPCM is enabled for both the chroma block and the luma block based on a result of the determination;
• generating a BDPCM luma flag indicating whether the BDPCM is applied to a current luma block;
• determining an intra prediction mode of the current luma block;
• generating a BDPCM luma direction flag indicating the intra prediction mode of the current luma block;
• deriving prediction samples of the current luma block based on the intra prediction mode of the current luma block;
• determining an intra prediction mode of a current chroma block;
• deriving prediction samples of the current chroma block based on the intra prediction mode of the current chroma block;
• deriving residual samples of the current luma block based on the prediction samples of the current luma block;
• deriving residual samples of the current chroma block based on the prediction samples of the current chroma block;
• and
• encoding image information including the BDPCM enabled flag and the BDPCM related information,
• wherein whether the BDPCM is enabled for the luma block is determined identically to whether the BDPCM is enabled for the chroma block depending on a value of the BDPCM enabled flag,
• wherein the value of the BDPCM enabled flag being equal to 0 represents that the BDPCM is not enabled for both the luma block and the chroma block, and the value of the BDPCM enabled flag being equal to 1 represents that the BDPCM is enabled for both the luma block and the chroma block,
• wherein, in response to a case where the BDPCM is applied to the current chroma block, residual coefficients are derived by performing a quantization on the residual samples of the current chroma block and a transform is not applied to the current chroma block,
• wherein the image information includes residual information for the residual coefficients,
• wherein, in response to a case where a value of the BDPCM enabled flag is 1, a BDPCM chroma flag indicating whether the BDPCM is applied to the current chroma block and a BDPCM chroma direction flag indicating a prediction direction of the current chroma block are not signaled,
• wherein a value of the BDPCM chroma flag is derived from the BDPCM luma flag and a value of the BDPCM chroma direction flag is derived from the BDPCM luma direction flag,
• wherein, in response to the value of the BDPCM chroma direction flag being derived as 0, the intra prediction mode of the current chroma block is determined as a horizontal intra prediction mode, and
• wherein, in response to the value of the BDPCM chroma direction flag being derived as 1, the intra prediction mode of the current chroma block is determined as a vertical intra prediction mode.

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

• determining whether Block-based Delta Pulse Code Modulation (BDPCM) is enabled for a chroma block and a luma block;
• generating a BDPCM enabled flag indicating whether the BDPCM is enabled for both the chroma block and the luma block based on a result of the determination;
• generating a BDPCM luma flag indicating whether the BDPCM is applied to a current luma block;
• determining an intra prediction mode of the current luma block;
• generating a BDPCM luma direction flag indicating the intra prediction mode of the current luma block;
• deriving prediction samples of the current luma block based on the intra prediction mode of the current luma block;
• determining an intra prediction mode of a current chroma block;
• deriving prediction samples of the current chroma block based on the intra prediction mode of the current chroma block;
• deriving residual samples of the current luma block based on the prediction samples of the current luma block;
• deriving residual samples of the current chroma block based on the prediction samples of the current chroma block;
• and
• encoding image information including the BDPCM enabled flag and the BDPCM related information;
• and
• generating the bitstream including the image information,
• wherein whether the BDPCM is enabled for the luma block is determined identically to whether the BDPCM is enabled for the chroma block depending on a value of the BDPCM enabled flag,
• wherein the value of the BDPCM enabled flag being equal to 0 represents that the BDPCM is not enabled for both the luma block and the chroma block, and the value of the BDPCM enabled flag being equal to 1 represents that the BDPCM is enabled for both the luma block and the chroma block,
• wherein, in response to a case where the BDPCM is applied to the current chroma block, residual coefficients are derived by performing a quantization on the residual samples of the current chroma block and a transform is not applied to the current chroma block,
• wherein the image information includes residual information for the residual coefficients,
• wherein, in response to a case where a value of the BDPCM enabled flag is 1, a BDPCM chroma flag indicating whether the BDPCM is applied to the current chroma block and a BDPCM chroma direction flag indicating a prediction direction of the current chroma block are not signaled,
• wherein a value of the BDPCM chroma flag is derived from the BDPCM luma flag and a value of the BDPCM chroma direction flag is derived from the BDPCM luma direction flag,
• wherein, in response to the value of the BDPCM chroma direction flag being derived as 0, the intra prediction mode of the current chroma block is determined as a horizontal intra prediction mode, and
• wherein, in response to the value of the BDPCM chroma direction flag being derived as 1, the intra prediction mode of the current chroma block is determined as a vertical intra prediction mode.

A transmission method of data for an image, the method comprising:

• obtaining a bitstream of image information including a Block-based Delta Pulse Code Modulation (BDPCM) enabled flag, a BDPCM luma flag indicating whether the BDPCM is applied to a current luma block and a BDPCM luma direction flag indicating the intra prediction mode of the current luma block, wherein the bitstream is generated by determining an intra prediction mode of the current luma block, deriving prediction samples of the current luma block based on the intra prediction mode of the current luma block, determining an intra prediction mode of a current chroma block, deriving prediction samples of the current chroma block based on the intra prediction mode of the current chroma block, deriving residual samples of the current luma block based on the prediction samples of the current luma block and deriving residual samples of the current chroma block based on the prediction samples of the current chroma block;
• and
• transmitting the data including the bitstream of the image information including the BDPCM enabled flag, the BDPCM luma flag and the BDPCM luma direction flag,
• wherein whether BDPCM is enabled for a chroma block and a luma block is determined and the BDPCM enabled flag indicating whether the BDPCM is enabled for both the chroma block and the luma block is generated based on a result of the determination,
• wherein whether the BDPCM is enabled for the luma block is determined identically to whether the BDPCM is enabled for the chroma block depending on a value of the BDPCM enabled flag,
• wherein the value of the BDPCM enabled flag being equal to 0 represents that the BDPCM is not enabled for both the luma block and the chroma block, and the value of the BDPCM enabled flag being equal to 1 represents that the BDPCM is enabled for both the luma block and the chroma block,
• wherein, in response to a case where the BDPCM is applied to the current chroma block, residual coefficients are derived by performing a quantization on the residual samples of the current chroma block and a transform is not applied to the current chroma block,
• wherein the image information includes residual information for the residual coefficients,
• wherein, in response to a case where a value of the BDPCM enabled flag is 1, a BDPCM chroma flag indicating whether the BDPCM is applied to the current chroma block and a BDPCM chroma direction flag indicating a prediction direction of the current chroma block are not signaled,
• wherein a value of the BDPCM chroma flag is derived from the BDPCM luma flag and a value of the BDPCM chroma direction flag is derived from the BDPCM luma direction flag,
• wherein, in response to the value of the BDPCM chroma direction flag being derived as 0, the intra prediction mode of the current chroma block is determined as a horizontal intra prediction mode, and
• wherein, in response to the value of the BDPCM chroma direction flag being derived as 1, the intra prediction mode of the current chroma block is determined as a vertical intra prediction mode.