Video decoding method using simplified residual data coding in video coding system, and apparatus therefor

1. An image decoding method, performed by a decoding apparatus, the method comprising:

obtaining residual information of a current block;

deriving residual samples of the current block based on the residual information; and

generating a reconstructed picture based on the residual samples,

wherein the obtaining the residual information comprises:

obtaining syntax elements for a first transform coefficient to an n-th transform coefficient of the current block; and

obtaining syntax elements for an n+1th transform coefficient to a last transform coefficient of the current block,

wherein a number of context-coded syntax elements for the first transform coefficient to the n-th transform coefficient is equal to a maximum number of context coded bins of the current block,

wherein the syntax elements for the first transform coefficient to the n-th transform coefficient are syntax elements according to a first residual data coding structure of Transform Skip Residual Coding (TSRC),

wherein the syntax elements for the n+1th transform coefficient to the last transform coefficient are syntax elements according to a second residual data coding structure of the TSRC, and

wherein the syntax elements according to the second residual data coding structure include coefficient level information and a sign flag for a transform coefficient.

2. The image decoding method of claim 1 , wherein the current block is a transform skip block,

wherein a transform skip flag representing whether transform is applied to the current block is obtained, and

wherein a value of the transform skip flag for the current block is 1.

3. The image decoding method of claim 1 , wherein the deriving the residual samples includes:

deriving transform coefficients of the current block based on the syntax elements according to the first residual data coding structure and the syntax elements according to the second residual data coding structure; and

deriving the residual samples based on the transform coefficients.

4. The image decoding method of claim 1 , wherein the context-coded syntax elements among the syntax elements according to the first residual data coding structure includes a significant coefficient flag for whether a transform coefficient is a non-zero transform coefficient, a sign flag for a sign for the transform coefficient, a first coefficient level flag for whether a coefficient level of the transform coefficient is greater than a first threshold value, and a parity level flag for a parity of the coefficient level for the transform coefficient.

5. The image decoding method of claim 1 , wherein the maximum number of the context-coded bins of the current block is derived based on a width and a height of the current block.

6. The image decoding method of claim 1 , wherein the n+1th transform coefficient to the last transform coefficient are derived based on the syntax elements according to the second residual data coding structure.

7. The image decoding method of claim 6 , wherein a coefficient level of the transform coefficient is derived as a value represented by the coefficient level information for the transform coefficient, and a sign of the transform coefficient is derived as a sign indicated by the sign flag.

8. The image decoding method of claim 1 , wherein the context-coded bins for the current block are all used as bins of the context-coded syntax elements for the first transform coefficient to the n-th transform coefficient.

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

deriving residual samples for a current block;

generating residual information for the residual samples; and

encoding image information including the residual information,

wherein the generating the residual information comprises:

deriving transform coefficients for the current block based on the residual samples;

generating syntax elements for a first transform coefficient to an n-th transform coefficient of the current block; and

generating syntax elements for an n+1th transform coefficient to a last transform coefficient of the current block,

wherein a number of context-coded syntax elements for the first transform coefficient to the n-th transform coefficient is equal to a maximum number of context coded bins of the current block,

wherein the syntax elements for the first transform coefficient to the n-th transform coefficient are syntax elements according to a first residual data coding structure of Transform Skip Residual Coding (TSRC),

wherein the syntax elements for the n+1th transform coefficient to the last transform coefficient are syntax elements according to a second residual data coding structure of the TSRC, and

wherein the syntax elements according to the second residual data coding structure include coefficient level information and a sign flag for a transform coefficient.

10. The image encoding method of claim 9 , wherein the maximum number of the context-coded bins of the current block is derived based on a width and a height of the current block.

11. The image encoding method of claim 9 , wherein the current block is a transform skip block,

wherein the image information includes a transform skip flag representing whether transform is applied to the current block, and

wherein a value of the transform skip flag for the current block is 1.

12. The image encoding method of claim 9 , wherein the context-coded bins for the current block are all used as bins of the context-coded syntax elements for the first transform coefficient to the n-th transform coefficient.

13. The image encoding method of claim 9 , wherein the context-coded syntax elements among the syntax elements according to the first residual data coding structure includes a significant coefficient flag for whether a transform coefficient is a non-zero transform coefficient, a sign flag for a sign for the transform coefficient, a first coefficient level flag for whether a coefficient level of the transform coefficient is greater than a first threshold value, and a parity level flag for a parity of the coefficient level for the transform coefficient.

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

deriving residual samples for a current block;

generating residual information for the residual samples;

encoding image information including the residual information; and

generating the bitstream including the image information,

wherein the generating the residual information comprises:

deriving transform coefficients for the current block based on the residual samples;

generating syntax elements for a first transform coefficient to an n-th transform coefficient of the current block; and

generating syntax elements for an n+1th transform coefficient to a last transform coefficient of the current block,

wherein a number of context-coded syntax elements for the first transform coefficient to the n-th transform coefficient is equal to a maximum number of context coded bins of the current block,

wherein the syntax elements for the first transform coefficient to the n-th transform coefficient are syntax elements according to a first residual data coding structure of Transform Skip Residual Coding (TSRC),

wherein the syntax elements for the n+1th transform coefficient to the last transform coefficient are syntax elements according to a second residual data coding structure of the TSRC, and

wherein the syntax elements according to the second residual data coding structure include coefficient level information and a sign flag for a transform coefficient.

15. The computer-readable storage medium of claim 14 , wherein the maximum number of the context-coded bins of the current block is derived based on a width and a height of the current block.