Method and apparatus for coding transform coefficient in video/image coding system
A video decoding method performed by a decoding apparatus according to the present document may comprise the steps of: obtaining, from a bitstream, information indicating a level value of a transform coefficient in a current block; selecting one Rice parameter look-up table for the information indicating the level value of the transform coefficient, from among a plurality of Rice parameter look-up tables; deriving a Rice parameter for the information indicating the level value of the transform coefficient on the basis of the selected Rice parameter look-up table; deriving a bin string for the information indicating the level value of the transform coefficient on the basis of the Rice parameter; and deriving the level value of the transform coefficient on the basis of the bin string.
1. A video decoding method performed by a decoding apparatus, the method comprising:
receiving a bitstream including information related to a level value of a transform coefficient in a current block;
determining an index value of a rice parameter lookup table for the information related to the level value of the transform coefficient;
deriving a rice parameter for the information related to the level value of the transform coefficient based on the rice parameter lookup table and the index value;
deriving a bin string for the information related to the level value of the transform coefficient based on the rice parameter; and
deriving the level value of the transform coefficient based on the bin string,
wherein the deriving the rice parameter comprises:
deriving a temporary rice parameter based on the index value and the rice parameter lookup table; and
deriving the rice parameter by adding an offset to the temporary rice parameter.
2. The video decoding method of claim 1 , wherein the deriving the rice parameter comprises:
deriving a modified index value based on the index value; and
deriving the rice parameter by using the modified index value and the rice parameter lookup table,
wherein the deriving the modified index value comprises deriving the modified index value based on whether a sum of level values of neighboring transform coefficients of the transform coefficient is smaller than a threshold value.
3. The video decoding method of claim 2 , wherein the deriving the modified index value comprises deriving the modified index value based on the index value and a shift value.
4. The video decoding method of claim 1 , wherein the deriving the rice parameter comprises:
deriving modified index value based on the index value and a shift value;
deriving a temporary rice parameter based on the modified index value and the rice parameter lookup table; and
deriving the rice parameter by adding an offset to the temporary rice parameter.
5. The video decoding method of claim 4 , wherein based on a specific syntax element which is coded prior to the information related to the level value of the transform coefficient, the modified index value is derived by using the shift value and the rice parameter is derived by using the offset.
6. The video decoding method of claim 5 , wherein the index value is derived based on a sum of level values of neighboring transform coefficients of the transform coefficient.
7. The video decoding method of claim 1 , wherein the information related to the level value of the transform coefficient includes a syntax element dec_abs_level representing the level value of the transform coefficient or a syntax element abs_remainder representing a remaining level value of the transform coefficient.
8. A video encoding method performed by an encoding apparatus, the method comprising:
generating information related to a level value of a transform coefficient in a current block;
determining an index value of a rice parameter lookup table for the information related to the level value of the transform coefficient;
deriving a rice parameter for the information related to the level value of the transform coefficient based on the index value and the rice parameter lookup table;
deriving a bin string for the information related to the level value of the transform coefficient based on the rice parameter; and
encoding the bin string,
wherein the deriving the rice parameter comprises:
deriving a temporary rice parameter based on the index value and the rice parameter lookup table; and
deriving the rice parameter by adding an offset to the temporary rice parameter.
9. The video encoding method of claim 8 , wherein the deriving the rice parameter comprises:
deriving a modified index value based on the index value; and
deriving the rice parameter by using the modified index value and the rice parameter lookup table,
wherein the deriving the modified index value comprises deriving the modified index value based on whether a sum of level values of neighboring transform coefficients of the transform coefficient is smaller than a threshold value.
10. The video encoding method of claim 9 , wherein the deriving the modified index value comprises deriving the modified index value based on the index value and a shift value.
11. The video encoding method of claim 8 , wherein the deriving the rice parameter comprises:
deriving modified index value based on the index value and a shift value;
deriving a temporary rice parameter based on the modified index value and the rice parameter lookup table; and
deriving the rice parameter by adding an offset to the temporary rice parameter.
12. The video encoding method of claim 11 , wherein based on a specific syntax element which is coded prior to the information related to the level value of the transform coefficient, the modified index value is derived by using the shift value and the rice parameter is derived by using the offset.
13. The video encoding method of claim 12 , wherein the index value is derived based on a sum of level values of neighboring transform coefficients of the transform coefficient.
14. The video encoding method of claim 8 , wherein the information related to the level value of the transform coefficient includes a syntax element dec_abs_level representing the level value of the transform coefficient or a syntax element abs_remainder representing a remaining level value of the transform coefficient.
15. A method for transmitting a bitstream generated by an image encoding method, the image encoding method comprising:
generating information related to a level value of a transform coefficient in a current block;
determining an index value of a rice parameter lookup table for the information related to the level value of the transform coefficient;
deriving a rice parameter for the information related to the level value of the transform coefficient based on the index value and the rice parameter lookup table;
deriving a bin string for the information related to the level value of the transform coefficient based on the rice parameter; and
generating the bitstream by encoding the bin string,
wherein the deriving the rice parameter comprises:
deriving a temporary rice parameter based on the index value and the rice parameter lookup table; and
deriving the rice parameter by adding an offset to the temporary rice parameter.