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

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

• deriving a current residual coefficient in a current sub-block of a current block;
• deriving a context index increment for a sign flag of the current residual coefficient;
• encoding the sign flag based on the context index increment;
• and
• generating a bitstream including the sign flag,
• wherein it is determined whether the current block is a transform skip block, and
• based on the current block being the transform skip block, sign flags of residual coefficients of the current block including the current residual coefficient are context-based encoded,
• wherein the context index increment for the sign flag is derived based on a sign level of a residual coefficient prior to the current residual coefficient in the current sub-block,
• wherein a value of the context index increment is determined as 0, based on the current residual coefficient being a first residual coefficient in scan order in the current sub-block.

A non-transitory computer-readable storage medium storing instructions which, when executed, cause a method to be performed, the method comprising:

• deriving a current residual coefficient in a current sub-block of a current block;
• deriving a context index increment for a sign flag of the current residual coefficient;
• encoding the sign flag based on the context index increment;
• and
• generating the bitstream including the sign flag,
• wherein it is determined whether the current block is a transform skip block, and
• based on the current block being the transform skip block, sign flags of residual coefficients of the current block including the current residual coefficient are context-based encoded,
• wherein the context index increment for the sign flag is derived based on a sign level of a residual coefficient prior to the current residual coefficient in the current sub-block,
• wherein a value of the context index increment is determined as 0, based on the current residual coefficient being a first residual coefficient in scan order in the current sub-block.

A transmission method of data for image, the method comprising:

• obtaining a bitstream of image information including sign flag of a current residual coefficient in a current sub-block of a current block;
• and
• transmitting the data including the bitstream of the image information including the sign flag,
• wherein it is determined whether the current block is a transform skip block, and
• based on the current block being the transform skip block, sign flags of residual coefficients of the current block including the current residual coefficient are context-based encoded,
• wherein the sign flag is generated by deriving the current residual coefficient in the current sub-block of the current block, deriving a context index increment for the sign flag of the current residual coefficient, and encoding the sign flag based on the context index increment,
• wherein the context index increment for the sign flag is derived based on a sign level of a residual coefficient prior to the current residual coefficient in the current sub-block,
• wherein a value of the context index increment is determined as 0, based on the current residual coefficient being a first residual coefficient in scan order in the current sub-block.

A decoding apparatus comprising a processor and a digital storing medium storing instructions, wherein the instructions, when executed, cause the decoding apparatus to perform:

• receiving residual information for a current block;
• deriving a context index increment for a sign flag of a current residual coefficient in a current sub-block of the current block;
• decoding the sign flag based on the context index increment;
• deriving the current residual coefficient based on the sign flag;
• deriving a residual sample based on the current residual coefficient;
• and
• generating a reconstructed picture based on the residual sample,
• wherein it is determined whether the current block is a transform skip block, and
• based on the current block being the transform skip block, sign flags of residual coefficients of the current block including the current residual coefficient are context-based decoded,
• wherein the context index increment for the sign flag is derived based on a sign level of a residual coefficient prior to the current residual coefficient in the current sub-block,
• wherein a value of the context index increment is derived as 0, based on the current residual coefficient being a first residual coefficient in scan order in the current sub-block.

An encoding apparatus comprising a processor and a digital storing medium storing instructions, wherein the instructions, when executed, cause the encoding apparatus to perform:

• deriving a current residual coefficient in a current sub-block of a current block;
• deriving a context index increment for a sign flag of the current residual coefficient;
• encoding the sign flag based on the context index increment;
• and
• generating a bitstream including the sign flag,
• wherein it is determined whether the current block is a transform skip block, and
• based on the current block being the transform skip block, sign flags of residual coefficients of the current block including the current residual coefficient are context-based encoded,
• wherein the context index increment for the sign flag is derived based on a sign level of a residual coefficient prior to the current residual coefficient in the current sub-block,
• wherein a value of the context index increment is determined as 0, based on the current residual coefficient being a first residual coefficient in scan order in the current sub-block.