Image encoding and decoding method and device for limiting partition condition of chroma block, and method for transmitting bitstream

An apparatus for image encoding, the apparatus comprising:

• a memory;
• and
• at least one processor connected to the memory, the at least one processor configured to:
• determine whether a predetermined splitting type is allowed for a first block;
• determine a splitting type for the first block based on whether the predetermined splitting type is allowed for the first block;
• obtain a second block by splitting the first block based on the determined splitting type;
• generate prediction samples by performing prediction for the second block based on prediction information;
• and
• encode the second block based on the generated prediction samples,
• wherein, based on a tree structure of the first block being a dual tree structure and a width of a chroma block derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is not allowed for the first block regardless of a height of the chroma block, and
• wherein, based on a tree structure of the first block being a dual tree structure and a height of a chroma block with a width greater than 4 derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is allowed for the first block.

An apparatus for transmitting data for an image, the apparatus comprising:

• at least one processor configured to obtain a bitstream;
• and
• a transmitter configured to transmit the bitstream, wherein the bitstream is generated by an image encoding method, the image encoding method comprises:
• determining whether a predetermined splitting type is allowed for a first block;
• determining a splitting type for the first block based on whether the predetermined splitting type is allowed for the first block;
• obtaining a second block by splitting the first block based on the determined splitting type;
• generating prediction samples by performing prediction for the second block based on prediction information;
• encoding the second block based on the generated prediction samples into a bitstream;
• and
• transmitting the data comprising the bitstream,
• wherein, based on a tree structure of the first block being a dual tree structure and a width of a chroma block derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is not allowed for the first block regardless of a height of the chroma block, and
• wherein, based on a tree structure of the first block being a dual tree structure and a height of a chroma block with a width greater than 4 derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is allowed for the first block.