Image decoding device, image decoding method, and program

An image decoding method comprising:

• applying geometric block partitioning merge to a target block divided in a rectangular shape,
• wherein the applying includes:
• specifying whether or not the geometric block partitioning merge is applied;
• specifying a geometric block partitioning pattern and further performing geometric block partitioning on the target block divided in the rectangular shape by using the specified geometric block partitioning pattern;
• and
• constructing a merge list for the target block subjected to the geometric block partitioning and decoding motion information, wherein
• in the specifying whether or not the geometric block partitioning merge is applied, a determination condition for specifying whether or not the geometric block partitioning merge is applicable is added in a condition for determination of whether or not decoding of a regular merge flag that specifies whether or not the regular merge is applied is necessary, and
• the determination condition for applying the geometric block partitioning merge includes a determination condition based on an upper limit of a height of the target block and an upper limit of a width of the target block.

A program stored on a non-transitory computer-readable medium for causing a computer to function as an image decoding device, wherein

• the image decoding device includes a merge unit configured to apply geometric block partitioning merge to a target block divided in a rectangular shape,
• the merge unit includes:
• a merge mode specifying unit configured to specify whether or not the geometric block partitioning merge is applied;
• a geometric block partitioning unit configured to specify a geometric block partitioning pattern and further perform geometric block partitioning on the target block divided in the rectangular shape by using the specified geometric block partitioning pattern;
• and
• a merge list construction unit configured to construct a merge list for the target block subjected to the geometric block partitioning and decode motion information,
• the merge mode specifying unit is configured to add a determination condition for specifying whether or not the geometric block partitioning merge is applicable in a condition for determination of whether or not decoding of a regular merge flag that specifies whether or not the regular merge is applied is necessary, and
• the determination condition for applying the geometric block partitioning merge includes a determination condition based on an upper limit of a height of the target block and an upper limit of a width of the target block.