Encoding and decoding methods and corresponding devices

A coding method for encoding a block of an image comprising:

• determining a split mode for said block in a set of split modes, wherein said set of split modes comprises at least one split mode for asymmetrically splitting said block into the at least two sub-blocks;
• splitting said block into at least two sub-blocks responsive to said split mode;
• encoding each of the at least two sub-blocks, wherein determining said split mode comprises:
• determining and encoding a first syntax element (btSplitOrientation) specifying whether said block is split vertically or horizontally;
• determining and encoding a second syntax element (horAsymmetricSplitFlag, verAsymmetricSplitFlag) specifying whether said block is split symmetrically or asymmetrically;
• and
• determining and encoding a split mode syntax element (vertical_asymmetric_type/horizontal_asymmetric_type) in the case where said second syntax element specifies that said block is split asymmetrically.

A decoding device comprising one or more processors configured to:

• determine a split mode for said block in a set of split modes, wherein said set of split modes comprises at least one split mode for asymmetrically splitting said block into the at least two sub-blocks;
• split said block into at least two sub-blocks responsive to said split mode;
• decode each of the at least two sub-blocks, wherein determining said split mode comprises:
• decoding a first syntax element (btSplitOrientation) specifying whether said block is split vertically or horizontally;
• decoding a second syntax element (horAsymmetricSplitFlag, verAsymmetricSplitFlag) specifying whether said block is split symmetrically or asymmetrically;
• and
• decoding a split mode syntax element (vertical_asymmetric_type/horizontal_asymmetric_type) in the case where said second syntax element specifies that said block is split asymmetrically.

A coding device comprising one or more processors configured to:

• determine a split mode for said block in a set of split modes, wherein said set of split modes comprises at least one split mode for asymmetrically splitting said block into the at least two sub-blocks;
• split said block into at least two sub-blocks responsive to said split mode;
• encode each of the at least two sub-blocks, wherein determining a split mode comprises:
• determining and encoding a first syntax element (btSplitOrientation) specifying whether said block is split vertically or horizontally;
• determining and encoding a second syntax element (horAsymmetricSplitFlag, verAsymmetricSplitFlag) specifying whether said block is split symmetrically or asymmetrically;
• and
• determining and encoding a split mode syntax element (vertical_asymmetric_type/horizontal_asymmetric_type) in the case where said second syntax element specifies that said block is split asymmetrically.