Image decoding method and device using residual information in image coding system
An image decoding method includes receiving residual information including first size related information for a first residual coefficient and second size related information for a second residual coefficient, setting a Rice parameter of the first size related information and the second size related information as a specific value, deriving available binary values based on the Rice parameter, deriving binary values of the first size related information and the second size related information by decoding the first size related information and the second size related information, deriving values of the first size related information and the second size related information by comparing the binary values and the available binary values, deriving the first residual coefficient and the second residual coefficient based on the values, and reconstructing a current picture based on the first residual coefficient and the second residual coefficient.
1. A method for image decoding performed by a decoding apparatus, the method comprising:
receiving residual information including first size related information for a first residual coefficient and second size related information for a second residual coefficient of a current block;
setting a Rice parameter of the first size related information and the second size related information as a specific value;
deriving available binary values for the first size related information and the second size related information based on the Rice parameter;
deriving a binary value of the first size related information and a binary value of the second size related information by decoding the first size related information and the second size related information;
deriving values of the first size related information and the second size related information by comparing the binary values and the available binary values;
deriving the first residual coefficient and the second residual coefficient based on the values of the first size related information and the second size related information; and
reconstructing a current picture based on the first residual coefficient and the second residual coefficient.
2. The method of claim 1 , wherein the residual information includes a transform skip flag for the current block,
wherein the transform skip flag represents whether to apply transform of residual coefficients, and
wherein the Rice parameter is set based on the transform skip flag.
3. The method of claim 2 , wherein when a value of the transform skip flag is 1, wherein the Rice parameter of the first size related information and the second size related information is set to the specific value.
4. The method of claim 1 , wherein the specific value is 1.
5. The method of claim 1 , wherein the specific value is one of 2, 3, 4 and 5.
6. The method of claim 1 , wherein the Rice parameter is set based on a size of the current block.
7. The method of claim 6 , wherein when a size of the current block is less than a specific size, wherein the Rice parameter is set to 0, and
when the size of the current block is greater than or equal to the specific size, wherein the Rice parameter for residual coefficients of the current block is set to 1.
8. The method of claim 6 , wherein when a sample number of the current block is less than 256, wherein the Rice parameter is set to 1, and
when a sample number of the current block is greater than or equal to 256, wherein the Rice parameter is set to 2.
9. The method of claim 1 , wherein the Rice parameter is set based on a ratio between a width and a height of the current block.
10. The method of claim 9 , when the ratio between the width and the height of the current block is greater than 2 and less than ½, wherein the Rice parameter is set to 0, and
when the ratio between the width and the height of the current block is ½ or more and 2 or less, wherein the Rice parameter is set to 1.
11. A method for image encoding performed by an encoding apparatus, the method comprising:
deriving a first residual coefficient and a second residual coefficient of a current block;
setting a Rice parameter for the first residual coefficient and the second residual coefficient as a specific value;
deriving binary values for first size related information for the first residual coefficient and second size related information for the second residual coefficient based on the Rice parameter; and
generating residual information including the first size related information and the second size related information by encoding the binary values for the first size related information and the second size related information.
12. The method of claim 11 , wherein the residual information includes a transform skip flag for the current block,
wherein the transform skip flag represents whether to apply transform of residual coefficients, and
wherein the Rice parameter is set based on the transform skip flag.
13. The method of claim 12 , wherein when a value of the transform skip flag is 1, the Rice parameter of the first size related information and the second size related information is set to the specific value.
14. The method of claim 11 , wherein the specific value is 1.
15. The method of claim 11 , wherein the specific value is one of 2, 3, 4 and 5.