Image decoding method for chroma quantization parameter data and apparatus therefor

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

• deriving prediction samples for chroma components based on inter prediction or intra prediction;
• deriving residual samples for the chroma components based on the prediction samples;
• generating a flag representing whether one chroma quantization parameter table is applied or not;
• generating chroma quantization parameter data for the chroma components based on the flag;
• and
• encoding prediction information for the chroma components, residual information for the chroma components, the chroma quantization parameter data and the flag,
• wherein the flag equal to 0 represents that a first chroma quantization parameter table for a Cb component, a second chroma quantization parameter table for a Cr component, and a third chroma quantization parameter table for a joint CbCr component are signaled.

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

• deriving prediction samples for chroma components based on inter prediction or intra prediction;
• deriving residual samples for the chroma components based on the prediction samples;
• generating a flag representing whether one chroma quantization parameter table is applied or not;
• generating chroma quantization parameter data for the chroma components based on the flag;
• encoding prediction information for the chroma components, residual information for the chroma components, the chroma quantization parameter data and the flag;
• and
• generating the bitstream including the prediction information, the residual information, the chroma quantization parameter data, and the flag,
• wherein the flag equal to 0 represents that a first chroma quantization parameter table for a Cb component, a second chroma quantization parameter table for a Cr component, and a third chroma quantization parameter table for a joint CbCr component are signaled.

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

• obtaining a bitstream of image information including prediction information and residual information for chroma components, a flag, and chroma quantization parameter data for the chroma components;
• and
• transmitting the data including the bitstream of the image information including the prediction information, the residual information, the flag and the chroma quantization parameter data,
• wherein the prediction information is information for prediction samples for the chroma components, and the prediction samples for the chroma components is derived based on inter prediction or intra prediction,
• wherein the residual information is information for residual samples for the chroma components, and the residual samples for the chroma components is derived based on the prediction samples,
• wherein the flag represents whether one chroma quantization parameter table is applied or not,
• wherein the chroma quantization parameter data is generated based on the flag, and
• wherein the flag equal to 0 represents that a first chroma quantization parameter table for a Cb component, a second chroma quantization parameter table for a Cr component, and a third chroma quantization parameter table for a joint CbCr component are signaled.