Method and apparatus for encoding/decoding video using maximum size limitation of chroma transform block, and method for transmitting bitstream

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

determining a prediction mode of a current block;

generating a prediction block of the current block based on inter prediction mode information, based on the prediction mode of the current block being an inter prediction mode;

generating a residual block of the current block based on a transform block of the current block; and

reconstructing the current block based on the prediction block and the residual block of the current block,

wherein a maximum width and a maximum height of the transform block is separately determined based on a color component of the current block, and

wherein, based on the color component of the current block being a chroma component, the maximum width and the maximum height of the transform block are determined based on a maximum size of a luma transform block corresponding to the current block and a color format of the current block.

2. The image decoding method of claim 1 ,

wherein a position of a top-left sample of the transform block is determined based on a position of a top-left sample of the luma transform block and the color format of the current block.

3. The image decoding method of claim 1 ,

wherein, based on the transform block being split into a plurality of lower-layer transform blocks, a top-left position of the lower-layer transform blocks is determined based on the maximum width and the maximum height of the transform block.

4. The image decoding method of claim 1 ,

wherein the current block is a chroma block, and

wherein a plurality of lower-layer transform blocks are generated by vertically splitting the current block, based on a width of the transform block being greater than the maximum width of the transform block.

5. The image decoding method of claim 4 ,

wherein the plurality of lower-layer transform blocks include a first lower-layer block and a second lower-layer transform block,

wherein a width of the first lower-layer transform block is determined to be half the width of the transform block, and

wherein a top-left coordinate of the second lower-layer transform block is shifted from a top-left coordinate of the transform block to the right by half the width of the transform block.

6. The image decoding method of claim 1 ,

wherein the current block is a chroma block, and

wherein a plurality of lower-layer transform blocks are generated by horizontally splitting the current block, based on a height of the transform block being greater than the maximum height of the transform block.

7. The image decoding method of claim 6 ,

wherein the plurality of lower-layer transform blocks include a third lower-layer block and a fourth lower-layer transform block,

wherein a height of the third lower-layer transform block is determined to be half the height of the transform block, and

wherein a top-left coordinate of the fourth lower-layer transform block is shifted downward from a top-left coordinate of the transform block by half the height of the transform block.

8. The image decoding method of claim 1 ,

wherein a width of the transform block is determined based on the maximum width of the transform block.

9. The image decoding method of claim 8 ,

wherein a height of the transform block is determined based on the maximum height of the transform block.

10. The image decoding method of claim 1 ,

wherein, based on the color format of the current block being a format specifying that a width of a chroma block is half a width of a corresponding luma block, a maximum size of the transform block is determined to be 32×64.

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

determining a current block by splitting an image;

generating an inter prediction block of the current block;

generating a residual block of the current block based on the inter prediction block; and

encoding inter prediction mode information of the current block,

wherein the residual block is encoded based on a size of a transform block of the current block,

wherein a maximum width and a maximum height of the transform block is separately determined based on a color component of the current block, and

wherein, based on the color component of the current block being a chroma component, the maximum width and the maximum height of the transform block are determined based on a maximum size of a luma transform block corresponding to the current block and a color format of the current block.

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

determining a current block by splitting an image;

generating an inter prediction block of the current block;

generating a residual block of the current block based on the inter prediction block; and

encoding inter prediction mode information of the current block into the bitstream,

wherein the residual block is encoded based on a size of a transform block of the current block,

wherein a maximum width and a maximum height of the transform block is separately determined based on a color component of the current block, and

wherein, based on the color component of the current block being a chroma component, the maximum width and the maximum height of the transform block are determined based on a maximum size of a luma transform block corresponding to the current block and a color format of the current block.

13. A non-transitory computer-readable recording medium storing a bitstream generated by an image encoding method, the image encoding method comprising:

determining a current block by splitting an image;

generating an inter prediction block of the current block;

generating a residual block of the current block based on the inter prediction block; and

encoding inter prediction mode information of the current block into the bitstream,

wherein the residual block is encoded based on a size of a transform block of the current block,

wherein a maximum width and a maximum height of the transform block is separately determined based on a color component of the current block, and

wherein, based on the color component of the current block being a chroma component, the maximum width and the maximum height of the transform block are determined based on a maximum size of a luma transform block corresponding to the current block and a color format of the current block.