Image encoding/decoding method and device, and method for transmitting bitstream

An image decoding apparatus comprising:

• a memory;
• and
• at least one processor,
• wherein the at least one processor is configured to:
• determine a prediction mode of a current block based on prediction mode information of the current block;
• determine 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;
• decode ISP mode information for the current block, based on the ISP being available for the current block;
• and
• generate a prediction sample for the current block based on the ISP mode information,
• wherein the ISP mode information includes whether the current block is partitioned into sub-partitions.

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 whether the current block is partitioned into sub-partitions.