Image encoding/decoding method and device using adaptive size limiting of chroma block and bitstream transmission method

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

determining a splitting structure of a current block composed of chroma components;

determining a splitting type of the current block based on the splitting structure;

obtaining a plurality of lower-layer blocks by splitting the current block based on the splitting type; and

decoding the lower-layer blocks based on a prediction mode of the lower-layer blocks,

wherein the determining the splitting type of the current block is performed by determining the splitting type of the current block based on an available splitting type determined based on a width or height of the current block, based on the splitting structure of the current block being a dual tree structure determined regardless of a splitting type of a luma component block corresponding to the current block.

2. The image decoding method of claim 1 , wherein the splitting type of the current block is determined based on splitting information obtained from a bitstream based on the available splitting type.

3. The image decoding method of claim 1 ,

wherein the available splitting type is determined by not allowing a predetermined splitting type, based on the width or height of the current block being equal to or less than a predetermined value, and

wherein the predetermined value is determined based on the number of pixels processed per clock by the image decoding apparatus.

4. The image decoding method of claim 3 , wherein a vertical ternary splitting type is not allowed as the splitting type of the current block, based on the width of the current block is equal to or less than twice the number of pixels processed per clock by the image decoding apparatus.

5. The image decoding method of claim 1 , wherein a vertical ternary splitting type is not allowed as the splitting type of the current block, based on the width of the current block being 8.

6. The image decoding method of claim 3 , wherein a quad tree splitting type and a vertical ternary splitting type are not allowed as the splitting type of the current block, based on the width of the current block being equal to or less than the number of pixels processed per clock by the image decoding apparatus.

7. The image decoding method of claim 1 , wherein a quad tree splitting type and a vertical binary splitting type are not allowed as the splitting type of the current block, based on the width of the current block being 4.

8. The image decoding method of claim 1 , wherein, based on the image decoding apparatus performing an image processing process for a pixel set composed of 1×4 matrix per clock and the height of the current block being 8, a horizontal ternary splitting type is not allowed as the splitting type of the current block.

9. The image decoding method of claim 1 , wherein, based on the image decoding apparatus performing an image processing process for a pixel set composed of 1×4 matrix per clock and the height of the current block being 4, a quadtree splitting type and a horizontal binary splitting type are not allowed as the splitting type of the current block.

10. The image decoding method of claim 1 , wherein the width of the current block is determined based on a width and color format of the luma block corresponding to the current block.

11. The image decoding method of claim 10 , wherein the width of the current block is determined to be a value obtained by dividing the width of the luma block corresponding to the current block by a component ratio of a chroma sample and a luma sample derived based on the color format.

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

selecting a splitting structure of a current block composed of chroma components;

selecting an available splitting type of the current block based on the splitting structure; obtaining a plurality of lower-layer blocks by splitting the current block based on the available splitting type; and

encoding prediction mode information of the lower-layer blocks and splitting information of the current block based on a result of encoding the lower-layer blocks,

wherein the available splitting type of the current block is determined based on a width or height of the current block, based on the splitting structure of the current block being a dual tree structure determined regardless of a splitting type of a luma component block corresponding to the current block.

13. The image encoding method of claim 12 ,

wherein the available splitting type is determined by limiting use of a predetermined splitting type, based on the width or height of the current block being equal to or less than a predetermined value, and

wherein the predetermined value is determined depending on whether a value obtained by dividing the width or height of the current block is less than 4 according to the predetermined splitting type.

14. A non-transitory computer readable recording medium storing a bitstream generated by the image encoding method of claim 12 .