Method and device for entropy encoding, decoding video signal

1. A method for decoding a video signal, the method comprising:

checking whether a coding block is divided into a plurality of transform blocks;

based on the coding block being divided into the plurality of transform blocks, determining a limited region in the coding block based on a width and a height of a transform block of the plurality of transform blocks, wherein a last non-zero transform coefficient is positioned in the limited region;

obtaining first information regarding a position of the last non-zero transform coefficient within the limited region; and

decoding the transform block based on the position of the last non-zero transform coefficient,

wherein the first information is binarized based on a truncated unary code allocated within the limited region.

2. The method of claim 1 , further comprising:

obtaining second information representing a last non-zero region, wherein the last non-zero region represents a region including the last non-zero transform coefficient in a scan order;

dividing the coding block into a plurality of sub-regions; and

determining the last non-zero region of the coding block among the plurality of sub-regions based on the second information.

3. The method of claim 2 , wherein the coding block is divided into the plurality of sub-regions based on recursively dividing the coding block into regions with lower depths based on a predetermined division method.

4. The method of claim 3 , wherein the second information includes information indicating, for each depth, a region including the last non-zero transform coefficient from among the regions with lower depths divided from the coding block.

5. The method of claim 2 ,

wherein a step of dividing of the coding block into the plurality of sub-regions comprises grouping the width of the coding block into a plurality of horizontal groups and grouping the height of the coding block into a plurality of vertical groups,

wherein the coding block is divided into the plurality of sub-regions based on the horizontal groups and the vertical groups.

6. The method of claim 5 , wherein the second information includes information on a horizontal group or a vertical group indicating the last non-zero region from among the horizontal groups or the vertical groups.

7. The method of claim 6 ,

wherein the first information is binarized based on a truncated unary code and the second information is binarized based on a fixed length code.

8. The method of claim 7 , wherein the second information is decoded based on a regular mode using a context and the first information is decoded based on a bypass mode which does not use a context.

9. The method of claim 5 , further comprising:

adaptively determining a parameter set applied to the coding block from among prestored parameter sets,

wherein the parameter set includes at least one of a parameter indicating a number of horizontal groups or vertical groups, a parameter indicating a length of code allocated to each group, or a parameter indicating a context index used for code allocated to each group.

10. The method of claim 9 , wherein the adaptively determining of a parameter set applied to the coding block comprises determining a parameter set applied to the coding block based on a probability distribution of the position of the last non-zero transform coefficient.

11. The method of claim 2 , wherein the coding block is divided into sub-regions composed of a specific number of pixels when the coding block is a non-square block,

wherein the specific number is determined depending on a ratio of the width to the height of the coding block.

12. A device for decoding a video signal, comprising:

a processor configured to

check whether a coding block is divided into a plurality of transform blocks,

based on the coding block being divided into the plurality of transform blocks, determine a limited region in the coding block based on a width and a height of a transform block of the plurality of transform blocks, wherein a last non-zero transform coefficient is positioned in the limited region,

obtain first information regarding a position of the last non-zero transform coefficient within the limited region, and

decode the transform block based on the position of the last non-zero transform coefficient,

wherein the first information is binarized based on a truncated unary code allocated within the limited region.

13. A non-transitory computer readable medium storing a bitstream causing an image decoding apparatus to perform an image decoding method, the image decoding method comprising:

checking whether a coding block is divided into a plurality of transform blocks;

based on the coding block being divided into the plurality of transform blocks, determining a limited region in the coding block based on a width and a height of a transform block of the plurality of transform blocks, wherein a last non-zero transform coefficient is positioned in the limited region;

obtaining first information regarding a position of the last non-zero transform coefficient within the limited region; and

decoding the transform block based on the position of the last non-zero transform coefficient,

wherein the first information is binarized based on a truncated unary code allocated within the limited region.