Video encoding/decoding method and device using segmentation limitation for chroma block, and method for transmitting bitstream

1. An image decoding method performed by an image decoding apparatus, the image decoding method comprising:

obtaining information on splitting of a current block;

splitting the current block based on the information on splitting of the current block; and

decoding the current block,

wherein, based on the current block being a chroma block and a width of the current block being equal to 8, vertical ternary splitting is not allowed for the current block regardless of a height of a block being derived from the current block by the vertical ternary splitting.

2. The image decoding method of claim 1 ,

wherein, based on the current block being a chroma block and the width of the current block being equal to 4, vertical binary splitting is not allowed for the current block,

and wherein the vertical binary splitting is a method for splitting such that sides along a horizontal direction are made shorter.

3. The image decoding method of claim 1 , wherein the current block is a chroma block split into a dual tree splitting structure.

4. The image decoding method of claim 1 ,

wherein the current block is a chroma block, and

wherein the width or height of the current block is derived based on a width or height of a corresponding luma block and a color format.

5. The image decoding method of claim 4 , wherein the width or height of the current block is derived as a value obtained by dividing the width or height of the corresponding luma block by a component ratio between a chroma sample and a luma sample, the component ratio being derived based on the color format.

6. The image decoding method of claim 1 , wherein, based on predetermined splitting being not allowed for the current block, the information on splitting of the current block is determined as a value specifying splitting other than the predetermined splitting.

7. The image decoding method of claim 6 ,

wherein the information on splitting of the current block includes splitting type information specifying ternary splitting or binary splitting,

wherein, based on vertical ternary splitting and horizontal ternary splitting being not allowed for the current block, the splitting type information is determined as a value specifying binary splitting, and

wherein, based on vertical binary splitting and horizontal binary splitting being not allowed for the current block, the splitting type information is determined as a value specifying ternary splitting.

8. The image decoding method of claim 6 ,

wherein the information on splitting of the current block includes splitting direction information specifying vertical splitting or horizontal splitting,

wherein, based on vertical binary splitting and vertical ternary splitting being not allowed for the current block and horizontal binary splitting or horizontal ternary splitting being allowed, the splitting direction information is determined as a value specifying horizontal splitting, and

wherein, based on horizontal binary splitting and horizontal ternary splitting being not allowed for the current block and vertical binary splitting or vertical ternary splitting being allowed, the splitting direction information is determined as a value specifying vertical splitting.

9. The image decoding method of claim 1 , further comprising:

based on the current block being a chroma block predicted in an intra block copy (IBC) mode,

splitting a luma block corresponding to the current block into luma subblocks each having a predetermined size;

obtaining motion information of the luma subblocks;

deriving motion information of subblocks in the current block corresponding to the luma subblocks based on the motion information of the luma subblocks; and

performing IBC prediction on the current block based on the derived motion information,

wherein the predetermined size of each of the luma subblocks is 8×8.

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

splitting a current block based on whether predetermined splitting is allowed for the current block;

encoding information on splitting of the current block; and

encoding the current block,

wherein, based on the current block being a chroma block and a width of the current block being equal to 8, vertical ternary splitting is not allowed for the current block regardless of a height of a block being derived from the current block by the vertical ternary splitting.

11. A non-transitory computer-readable recording medium storing a bitstream generated by the image encoding method of claim 10 .

12. A method of transmitting a bitstream generated by an image encoding method, the image encoding method comprising:

splitting a current block based on whether predetermined splitting is allowed for the current block;

encoding information on splitting of the current block into the bitstream; and

encoding the current block into the bitstream,

wherein, based on the current block being a chroma block and a width of the current block being equal to 8, vertical ternary splitting is not allowed for the current block regardless of a height of a block being derived from the current block by the vertical ternary splitting.