Method and device for encoding and decoding image signal

A method of encoding an image signal, comprising:

• receiving a picture of the image signal;
• generating residual data of a transform block in the picture, the residual data being a difference between an original block of a coding block and a prediction block of the coding block;
• dividing the transform block into a plurality of partial blocks;
• and
• encoding a coefficient of the transform block in units of the partial blocks,
• wherein encoding the coefficient of the transform block comprises:
• encoding a plurality of flags for a current coefficient,
• wherein the plurality of flags include a first flag and a second flag,
• wherein the first flag indicates whether an absolute value of the current coefficient is greater than a first value,
• wherein the second flag indicates whether the absolute value of the current coefficient is greater than a second value,
• wherein the first value and the second value are equal to or greater than 3,
• wherein the first value and the second value are different from each other,
• wherein the partial block is a square block or a non-square block having a size of N×M, and
• wherein whether the partial block is the square block or the non-square block is determined based on both a size of the transform block and a shape of the transform block.

A non-transitory computer-readable medium for storing data associated with an image signal, comprising:

• a data stream encoded by an encoding method,
• wherein the encoding method comprises:
• receiving a picture of the image signal;
• generating residual data of a transform block in the picture, the residual data being a difference between an original block of a coding block and a prediction block of the coding block;
• dividing the transform block into a plurality of partial blocks;
• and
• encoding a coefficient of the transform block in units of the partial blocks,
• wherein encoding the coefficient of the transform block comprises:
• encoding a plurality of flags for a current coefficient,
• wherein the plurality of flags include a first flag and a second flag,
• wherein the first flag indicates whether an absolute value of the current coefficient is greater than a first value,
• wherein the second flag indicates whether the absolute value of the current coefficient is greater than a second value,
• wherein the first value and the second value are equal to or greater than 3,
• wherein the first value and the second value are different from each other,
• wherein the partial block is a square block or a non-square block having a size of N×M, and
• wherein whether the partial block is the square block or the non-square block is determined based on both a size of the transform block and a shape of the transform block.