Image encoding/decoding method and device, and method for transmitting bitstream
An image encoding/decoding method and apparatus are provided. An image decoding method according to the present disclosure may include determining whether a prediction mode of a current block is an intra prediction mode based on information on the prediction mode of the current block, determining whether intra sub-partitions (ISP) is available for the current block, when the prediction mode of the current block is an intra prediction mode, decoding an ISP application indicator indicating whether to apply ISP to the current block, when ISP is available for the current block, and generating a prediction block for the current block by applying ISP to the current block, upon determining that ISP applies to the current block based on the ISP application indicator.
1. An image decoding method performed by an image decoding apparatus, the image decoding method comprising:
determining a prediction mode of a current block based on prediction mode information of the current block;
determining whether intra sub-partitions (ISP) is available for the current block based on the prediction mode of the current block being an intra prediction mode;
decoding ISP mode information for the current block, based on the ISP being available for the current block; and
generating a prediction sample for the current block based on the ISP mode information,
wherein the ISP mode information includes information on an ISP split direction,
wherein it is determined that the ISP is available for the current block based on both a width and a height of a luma component block of the current block being equal to or less than a predetermined threshold.
2. The image decoding method of claim 1 , wherein the predetermined threshold is a maximum transform size.
3. The image decoding method of claim 1 , wherein the generating the prediction sample for the current block based on the ISP mode information comprises:
generating a prediction sample for a luma component block by applying the ISP to the luma component block of the current block;
determining whether to apply the ISP to a chroma component block of the current block; and
generating a prediction sample for the chroma component block by applying the ISP to the chroma component block, upon determining that the ISP applies to the chroma component block of the current block.
4. The image decoding method of claim 3 , wherein the determining whether to apply the ISP to the chroma component block of the current block is performed based on at least one of a size of the chroma component block or a chroma format of the current block.
5. The image decoding method of claim 4 , wherein, when the chroma format of the current block is 4:2:2 or 4:4:4 and at least one of a width or height of the chroma component block is greater than a maximum transform size, it is determined that the ISP applies to the chroma component block of the current block.
6. The image decoding method of claim 3 , wherein, when the ISP applies to the chroma component block, a split direction and a number of sub-partitions for the chroma component block are determined based on a split direction and a number of sub-partitions for the luma component block.
7. The image decoding method of claim 6 , wherein the split direction and the number of sub-partitions for the chroma component block are equal to the split direction and the number of sub-partitions for the luma component block, respectively.
8. The image decoding method of claim 1 , wherein the generating the prediction sample for the current block based on the ISP mode information comprises:
generating a prediction sample for a luma component block by applying the ISP to the luma component block of the current block; and
generating a prediction sample for a chroma component block by applying the ISP to the chroma component block of the current block.
9. The image decoding method of claim 8 , wherein a split direction and a number of sub-partitions for the chroma component block are determined based on a split direction and a number of sub-partitions for the luma component block.
10. The image decoding method of claim 9 , wherein the split direction and the number of sub-partitions for the chroma component block are equal to the split direction and (the number of sub-partitions/2) of the luma component block, respectively.
11. An image encoding method performed by an image encoding apparatus, the image encoding method comprising:
determining a prediction mode of a current block;
determining whether intra sub-partitions (ISP) is available for the current block based on the prediction mode of the current block being an intra prediction mode;
determining whether to apply the ISP to the current block, based on the ISP being available for the current block;
generating a prediction sample for the current block by applying the ISP to the current block, based on the ISP being determined to be applied to the current block; and
encoding prediction mode information of the current block and ISP mode information,
wherein the ISP mode information includes information on an ISP split direction, and
wherein it is determined that the ISP is available for the current block based on both a width and a height of a luma component block of the current block being equal to or less than a predetermined threshold.
12. A non-transitory computer-readable medium storing a bitstream generated by an image encoding method, the image encoding method comprising:
determining a prediction mode of a current block;
determining whether intra sub-partitions (ISP) is available for the current block based on the prediction mode of the current block being an intra prediction mode;
determining whether to apply the ISP to the current block, based on the ISP being available for the current block;
generating a prediction sample for the current block by applying the ISP to the current block, based on the ISP being determined to be applied to the current block; and
encoding prediction mode information of the current block and ISP mode information,
wherein the ISP mode information includes information on an ISP split direction, and
wherein it is determined that the ISP is available for the current block based on both a width and a height of a luma component block of the current block being equal to or less than a predetermined threshold.