Encoder, decoder, encoding method, and decoding method

A decoder, comprising:

• circuitry;
• and
• memory, wherein
• the circuitry, using the memory:
• stores, in a storage region, a probability parameter for entropy decoding of a first current slice included in a first picture, the probability parameter becoming available when decoding of a final coding unit (CU) of the first current slice is completed;
• and
• initializes, with reference to the probability parameter stored in the storage region, a probability parameter for entropy decoding of a second current slice included in a second picture when decoding of a leading CU of the second current slice starts, and
• the first picture is a reference picture referred to when the second current slice is decoded, and the first current slice includes a CU located at a same position as a position of the leading CU of the second current slice.

An encoding method, comprising:

• storing, in a storage region, a probability parameter for entropy encoding of a first current slice included in a first picture, the probability parameter becoming available when encoding of a final coding unit (CU) of the first current slice is completed;
• and
• initializing, with reference to the probability parameter stored in the storage region, a probability parameter for entropy encoding of a second current slice included in a second picture when encoding of a leading CU of the second current slice starts, wherein
• the first picture is a reference picture referred to when the second current slice is encoded, and the first current slice includes a CU located at a same position as a position of the leading CU of the second current slice.

A decoding method, comprising:

• storing, in a storage region, a probability parameter for entropy decoding of a first current slice included in a first picture, the probability parameter becoming available when decoding of a final coding unit (CU) of the first current slice is completed;
• and
• initializing, with reference to the probability parameter stored in the storage region, a probability parameter for entropy decoding of a second current slice included in a second picture when decoding of a leading CU of the second current slice starts, wherein
• the first picture is a reference picture referred to when the second current slice is decoded, and the first current slice includes a CU located at a same position as a position of the leading CU of the second current slice.