Video decoding method using residual information in video coding system, and apparatus thereof

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

• deriving residual samples for a current block;
• deriving transform coefficients in a current block based on the residual samples;
• deriving a specific number for a number of context-coded bins for context syntax elements for the current block;
• encoding the context syntax elements based on the specific number;
• and
• generating a bitstream comprising residual information on the current block comprising the encoded context syntax elements,
• wherein, based on a transform skip being applied to the current block, a significant coefficient flag relating to whether a transform coefficient is a non-zero transform coefficient, a sign flag relating to a sign of the transform coefficient, a first transform coefficient level flag relating to whether a transform coefficient level is greater than a first threshold, a parity level flag relating to a parity of the transform coefficient level of the transform coefficient, and a second transform coefficient level flag relating to whether the transform coefficient level of the transform coefficient is greater than a second threshold are encoded based on a context model until the specific number is reached, and
• 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 specific number, signaling of context syntax elements for transform coefficient n+1 of the current block is omitted, and a bypass syntax element for transform coefficient n+1 comprised in the residual information is encoded.

A non-transitory computer-readable digital storage medium that stores a bitstream comprising residual information generated by a method, the method comprising:

• deriving residual samples for a current block;
• deriving transform coefficients in a current block based on the residual samples;
• deriving a specific number for a number of context-coded bins for context syntax elements for the current block;
• encoding the context syntax elements based on the specific number;
• and
• generating the bitstream comprising the residual information on the current block comprising the encoded context syntax elements,
• wherein, based on a transform skip being applied to the current block, a significant coefficient flag relating to whether a transform coefficient is a non-zero transform coefficient, a sign flag relating to a sign of the transform coefficient, a first transform coefficient level flag relating to whether a transform coefficient level is greater than a first threshold, a parity level flag relating to a parity of the transform coefficient level of the transform coefficient, and a second transform coefficient level flag relating to whether the transform coefficient level of the transform coefficient is greater than a second threshold are encoded based on a context model until the specific number is reached, and
• 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 specific number, signaling of context syntax elements for transform coefficient n+1 of the current block is omitted, and a bypass syntax element for transform coefficient n+1 comprised in the residual information is encoded.