Encoder, decoder, encoding method, and decoding method

An encoding method for encoding a current block in a picture, the encoding method comprising:

• splitting the current block into a first sub block, a second sub block, and a third sub block in a first direction, the second sub block being located between the first sub block and the third sub block;
• prohibiting splitting the second sub block into two partitions in the first direction;
• and
• encoding the first sub block, the second sub block, and the third sub block.

A decoder that decodes a current block in an encoded picture, the decoder comprising:

• circuitry;
• and
• memory, wherein
• using the memory, the circuitry:
• splits the current block into a first sub block, a second sub block, and a third sub block in a first direction, the second sub block being located between the first sub block and the third sub block;
• prohibits splitting the second sub block into two partitions in the first direction;
• and
• decodes the first sub block, the second sub block, and the third sub block.

A decoding method for decoding a current block in an encoded picture, the decoding method comprising:

• splitting the current block into a first sub block, a second sub block, and a third sub block in a first direction, the second sub block being located between the first sub block and the third sub block;
• prohibiting splitting the second sub block into two partitions in the first direction;
• and
• decoding the first sub block, the second sub block, and the third sub block.