Encoding method, decoding method, and method of transmitting a bitstream

A method, comprising:

• decoding an image block of a bitstream, the decoding including:
• determining whether or not a ternary split process of splitting a block into three sub blocks in a first direction parallel to a first longer side of the block is allowed by comparing a size of a second shorter side of the block to a minimum threshold value;
• responsive to the ternary split process being allowed, parsing, from a bitstream, a split direction parameter indicative of a splitting direction;
• splitting the block into a plurality of sub blocks in a direction indicated by the split direction parameter;
• and
• decoding the plurality of sub blocks,
• wherein the minimum threshold value corresponds to a minimum size supported in a transform process.

A method of transmitting a bitstream, the bitstream including:

• a split direction parameter indicative of a splitting direction;
• and syntax information configured to cause a computer to decode an image block, the decoding the image block including:
• determining whether or not a ternary split process of splitting the block into three sub blocks in a first direction parallel to a first longer side of the block is allowed by comparing a size of a second shorter side of the block to a minimum threshold value;
• responsive to the ternary split process being allowed, parsing, from the bitstream, the split direction parameter indicative of the splitting direction;
• splitting the block into a plurality of sub blocks in a direction indicated by the split direction parameter;
• and
• decoding the plurality of sub blocks,
• wherein the minimum threshold value corresponds to a minimum size supported in a transform process.