Image decoding method and device using residual information in image coding system
An image decoding method, which is performed by a decoding device according to the present document, is characterized by including: a step for receiving a bitstream including residual information about the current block; a step for deriving a maximum value of the number of context-encoding bins for context syntax elements coded on the basis of context included in the residual information; a step for entropy-decoding the context syntax elements on the basis of the maximum value; a step for deriving conversion coefficients for the current block on the basis of the entropy-decoded context syntax elements; a step for deriving a residual sample for the current block on the basis of the conversion coefficients; and a step for generating a reconstructed picture on the basis of the residual sample for the current block.
1 . An image decoding method performed by a decoding apparatus, comprising:
receiving a bitstream including intra prediction mode information and residual information of a current block;
deriving a maximum number of context-coded bins for context-based coded context syntax elements included in the residual information;
entropy decoding the context syntax elements based on the maximum number;
deriving a transform coefficient for the current block based on the entropy decoded context syntax elements;
deriving a residual sample for the current block based on the transform coefficient; and
generating a prediction sample for the current block based on the intra prediction mode information;
generating a reconstructed picture based on the prediction sample and the residual sample for the current block,
wherein the context syntax elements include:
a significant coefficient flag representing whether the transform coefficient is a non-zero transform coefficient,
a parity level flag for parity of a transform coefficient level for the transform coefficient,
a first transform coefficient level flag regarding whether the transform coefficient level is greater than a first threshold, and
a second transform coefficient level flag regarding whether the transform coefficient level of a quantized transform coefficient is greater than a second threshold, and
wherein the maximum number is a maximum number for a sum of following numbers:
a number of context-coded bins of significant coefficient flags,
a number of context-coded bins of first transform coefficient level flags,
a number of context-coded bins of parity level flags, and
a number of context-coded bins of second transform coefficient level flags.
2 . An image encoding method performed by an encoding apparatus, comprising:
generating intra prediction mode information for a current block;
deriving a residual sample for the current block;
deriving a transform coefficient based on the residual sample for the current block;
deriving a maximum number of context-coded bins for context syntax elements for the transform coefficient;
entropy encoding the context syntax elements based on the maximum number; and
outputting a bitstream including the intra prediction mode information and residual information for the current block including the entropy encoded context syntax elements,
wherein the context syntax elements include:
a significant coefficient flag representing whether the transform coefficient is a non-zero transform coefficient,
a parity level flag for parity of a transform coefficient level for the transform coefficient,
a first transform coefficient level flag regarding whether the transform coefficient level is greater than a first threshold, and
a second transform coefficient level flag regarding whether the transform coefficient level of a quantized transform coefficient is greater than a second threshold, and
wherein the maximum number is a maximum number for a sum of following numbers:
a number of context-coded bins of significant coefficient flags,
a number of context-coded bins of first transform coefficient level flags,
a number of context-coded bins of parity level flags, and
a number of context-coded bins of second transform coefficient level flags.
3 . A transmission method of data for image, the method comprising:
obtaining a bitstream of image information comprising intra prediction mode information and residual information for a current block including context syntax elements; and
transmitting the data including the bitstream of the image information comprising the intra prediction mode information and the residual information,
wherein the context syntax elements are entropy encoded based on a maximum number of context-coded bins for the context syntax elements,
wherein the context syntax elements include:
a significant coefficient flag representing whether a transform coefficient for the current block is a non-zero transform coefficient,
a parity level flag for parity of a transform coefficient level for the transform coefficient,
a first transform coefficient level flag regarding whether the transform coefficient level is greater than a first threshold, and
a second transform coefficient level flag regarding whether the transform coefficient level of a quantized transform coefficient is greater than a second threshold, and
wherein the maximum number is a maximum number for a sum of following numbers:
a number of context-coded bins of significant coefficient flags,
a number of context-coded bins of first transform coefficient level flags,
a number of context-coded bins of parity level flags, and
a number of context-coded bins of second transform coefficient level flags.