Image decoding method and device therefor
A method by which a decoding device decodes an image, according to the present document, comprises the steps of: acquiring image information; and generating a reconstruction picture on the basis of the image information.
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining image information; and
generating a reconstructed picture based on the image information,
wherein the obtaining the image information comprises:
obtaining prediction information and residual information for a chroma component of a current coding unit; and
obtaining Coding Unit (CU) chroma Quantization Parameter (QP) offset related information for the current coding unit based on a tree type and a size of the current coding unit,
wherein the CU chroma QP offset related information includes a CU chroma QP offset flag and a CU chroma QP offset index for the current coding unit, and
wherein, based on at least one of a width and a height of the current coding unit being greater than 64 and the tree type not being a dual tree luma, the CU chroma QP offset related information is obtained.
2. An image encoding method, performed by an encoding apparatus, comprising:
deriving prediction samples and residual samples for a chroma component of a current coding unit;
generating a reconstructed picture based on the prediction samples and the residual samples; and
encoding image information,
wherein the encoding the image information comprises:
generating prediction information for the current coding unit;
deriving a chroma Quantization Parameter (QP) for the current coding unit;
deriving transform coefficients for the current coding unit chroma block-by quantizing the residual samples based on the chroma QP;
generating residual information for the transform coefficients;
generating Coding Unit (CU) chroma QP offset related information for the chroma QP based on a tree type and a size of the current coding unit; and
encoding image information including the CU chroma QP offset related information, the prediction information, and the residual information,
wherein the CU chroma QP offset related information includes a CU chroma QP offset flag and a CU chroma QP offset index for the current coding unit, and
wherein, based on at least one of a width and a height of the current coding unit being greater than 64 and the tree type not being a dual tree luma, the CU chroma QP offset related information is signaled.
3. A non-transitory computer-readable storage medium storing a bitstream generated by a method, the method comprising:
deriving prediction samples and residual samples for a chroma component of a current coding unit;
generating a reconstructed picture based on the prediction samples and the residual samples;
encoding image information; and
generating the bitstream including the image information,
wherein the encoding the image information comprises:
generating prediction information for the current coding unit;
deriving a chroma Quantization Parameter (QP) for the current coding unit;
deriving transform coefficients for the current coding unit by quantizing the residual samples based on the chroma QP;
generating residual information for the transform coefficients;
generating Coding Unit (CU) chroma QP offset related information for the chroma QP based on a tree type and a size of the current coding unit; and
encoding image information including the CU chroma QP offset related information, the prediction information, and the residual information,
wherein the CU chroma QP offset related information includes a CU chroma QP offset flag and a CU chroma QP offset index for the current coding unit, and
wherein, based on at least one of a width and a height of the current coding unit being greater than 64 and the tree type not being a dual tree luma, the CU chroma QP offset related information is signaled.
4. A transmission method of data for image, the method comprising:
obtaining a bitstream of image information including Coding Unit (CU) chroma Quantization Parameter (QP) offset related information, prediction information and residual information for a chroma component of a current coding unit; and
transmitting the data including the bitstream of the image information including the CU chroma QP offset related information, the prediction information, and the residual information,
wherein prediction samples for the current coding unit are derived based on the prediction information,
wherein residual samples for the current coding unit are derived based on the residual information,
wherein the CU chroma QP offset related information for a chroma QP for the current coding unit is generated based on a tree type and a size of the current coding unit chroma block,
wherein the CU chroma QP offset related information includes a CU chroma QP offset flag and a CU chroma QP offset index for the current coding unit, and
wherein, based on at least one of a width and a height of the current coding unit being greater than 64 and the tree type not being a dual tree luma, the CU chroma QP offset related information is signaled.