Video decoding method and apparatus, and video encoding method and apparatus

A video encoding method comprising:

• generating information about an intra prediction mode of a top-left sample in a current chroma block;
• obtaining an intra prediction mode of a sample at a bottom-right location in a current luma block corresponding to the current chroma block, wherein the current luma block is split into at least two lower luma blocks including a lower luma block comprising the sample at the bottom-right location;
• determining an intra prediction mode of the top-left sample of the current chroma block using the intra prediction mode of the sample at the bottom-right location and the information;
• and
• generating a bitstream comprising the information about the intra prediction mode of the top-left sample in the current chroma block by performing intra prediction on the current chroma block using the intra prediction mode of the top-left sample of the current chroma block,
• wherein the sample at the bottom-right location is a sample at a location of ½ of a width of the current luma block in a right direction from a location of a top-left sample in the current luma block and ½ of a height of the current luma block in a lower direction from the location of the top-left sample in the current luma block, and
• wherein the current chroma block is one among a plurality of blocks split from an upper chroma block.

A non-transitory computer-readable medium for recording a bitstream, the bitstream comprising:

• information about an intra prediction mode of a top-left sample in a current chroma block;
• wherein the information about the intra prediction mode of the top-left sample in the current chroma block is obtained by:
• generating the information about the intra prediction mode of the top-left sample in the current chroma block;
• obtaining an intra prediction mode of a sample at a bottom-right location in a current luma block corresponding to the current chroma block, wherein the current luma block is split into at least two lower luma blocks including a lower luma block comprising the sample at the bottom-right location;
• determining an intra prediction mode of the top-left sample of the current chroma block using the intra prediction mode of the sample at the bottom-right location and the information;
• and
• generating a bitstream comprising the information about the intra prediction mode of the top-left sample in the current chroma block by performing intra prediction on the current chroma block using the intra prediction mode of the top-left sample of the current chroma block,
• wherein the sample at the bottom-right location is a sample at a location of ½ of a width of the current luma block in a right direction from a location of a top-left sample in the current luma block and ½ of a height of the current luma block in a lower direction from the location of the top-left sample in the current luma block, and
• wherein the current chroma block is one among a plurality of blocks split from an upper chroma block.