Video decoding method using residual information in video coding system, and apparatus thereof
A video decoding method performed by a decoding apparatus according to the present document comprises the steps of: receiving a bit stream including residual information of a current block; deriving a specific number of the number of context encoding bins for context syntax elements for a current sub-block of the current block; decoding the context syntax elements for the current sub-block included in the residual information on the basis of the specific number; deriving transform coefficients for the current sub-block on the basis of the decoded context syntax elements; deriving residual samples for the current block on the basis of the transform coefficients; and generating a reconstructed picture on the basis of the residual samples.
1. An image decoding method comprising:
receiving a bitstream comprising residual information;
deriving transform coefficients for a current block of an image based on the residual information, comprising:
determining a maximum value for a number of context-coded bins for context syntax elements for the current block;
decoding the context syntax elements for the current block comprised in the residual information based on the maximum value; and
deriving transform coefficients for the current block based on the decoded context syntax elements;
deriving residual samples for the current block based on the transform coefficients; and
generating a reconstructed image based on the residual samples for the current block,
wherein, when a total number of context-coded bins for context syntax elements of transform coefficient 0 to transform coefficient n of the current block reaches the maximum value, a bypass syntax element for transform coefficient n+1 comprised in the residual information is decoded, and
wherein the bypass syntax element comprises abs_remainder for a remaining absolute value of a transform coefficient level coded at a predetermined scanning position.
2. The image decoding method of claim 1 , wherein the maximum value is set based on a size of the current block.
3. The image decoding method of claim 1 , wherein a value of transform coefficient n+1 is derived based on a value of the bypass syntax element.
4. The image decoding method of claim 1 , wherein, when a transform skip is applied to the current block, one or more of
(i) a significant coefficient flag relating to whether a transform coefficient is a non-zero transform coefficient,
(ii) a sign flag relating to a sign of the transform coefficient,
(iii) a transform coefficient level flag relating to whether a transform coefficient level is greater than a threshold value, or
(iv) a parity level flag relating to a parity of the transform coefficient level of the transform coefficient,
are decoded based on a context model until the maximum value is reached.
5. An image encoding method comprising:
deriving residual samples for a current block;
deriving transform coefficients in the current block based on the residual samples; and
encoding residual information comprising information on the transform coefficients,
wherein the encoding of the residual information comprises:
deriving a maximum value for a number of context-coded bins for context syntax elements for the current block;
encoding the context syntax elements based on the maximum value; and
generating a bitstream comprising residual information on the current block comprising the encoded context syntax elements,
wherein, when a total number of context-coded bins for context syntax elements of transform coefficient 0 to transform coefficient n of the current block reaches the maximum value, a bypass syntax element for transform coefficient n+1 comprised in the residual information is encoded, and
wherein the bypass syntax element comprises abs_remainder for a remaining absolute value of a transform coefficient level coded at a predetermined scanning position.
6. The image encoding method of claim 5 , wherein the maximum value is set based on a size of the current block.
7. The image encoding method of claim 5 , wherein a value of transform coefficient n+1 is derived based on a value of the bypass syntax element.
8. The image encoding method of claim 5 , wherein, when a transform skip is applied to the current block, one or more of
(i) a significant coefficient flag relating to whether a transform coefficient is a non-zero transform coefficient,
(ii) a sign flag relating to a sign of the transform coefficient,
(iii) a transform coefficient level flag relating to whether a transform coefficient level is greater than a threshold value, or
(iv) a parity level flag relating to a parity of the transform coefficient level of the transform coefficient,
are encoded based on a context model until the maximum value is reached.
9. An apparatus for decoding an image, the apparatus comprising:
one or more processors that are configured to perform operations comprising:
receiving a bitstream comprising residual information;
deriving transform coefficients for a current block of an image based on the residual information, comprising:
determining a maximum value for a number of context-coded bins for context syntax elements for the current block;
decoding the context syntax elements for the current block comprised in the residual information based on the maximum value; and
deriving transform coefficients for the current block based on the decoded context syntax elements;
deriving residual samples for the current block based on the transform coefficients; and
generating a reconstructed image based on the residual samples for the current block,
wherein, when a total number of context-coded bins for context syntax elements of transform coefficient 0 to transform coefficient n of the current block reaches the maximum value, a bypass syntax element for transform coefficient n+1 comprised in the residual information is decoded, and
wherein the bypass syntax element comprises abs remainder for a remaining absolute value of a transform coefficient level coded at a predetermined scanning position.
10. The apparatus of claim 9 , wherein the maximum value is set based on a size of the current block.
11. The apparatus of claim 9 , wherein a value of transform coefficient n+1 is derived based on a value of the bypass syntax element.
12. The apparatus of claim 9 , wherein, when a transform skip is applied to the current block, one or more of
(i) a significant coefficient flag relating to whether a transform coefficient is a non-zero transform coefficient,
(ii) a sign flag relating to a sign of the transform coefficient,
(iii) a transform coefficient level flag relating to whether a transform coefficient level is greater than a threshold value, or
(iv) a parity level flag relating to a parity of the transform coefficient level of the transform coefficient,
are decoded based on a context model until the maximum value is reached.