Image decoding apparatus, image coding apparatus, image decoding circuit, and image decoding method

An image coding apparatus which generates a coded stream, comprising:

• a generating unit configured to generate a plurality of orthogonal transform bases for use in orthogonal transform of the coded stream and identification information identifying each of the plurality of orthogonal transform bases;
• an accumulation unit configured to store the plurality of orthogonal transform bases generated by said generating unit;
• a storage unit configured to store at least one of the orthogonal transform bases stored in said accumulation unit, the at least one orthogonal transform basis being required for current orthogonal transform of a current block;
• an orthogonal transform unit configured to perform the current orthogonal transform using the at least one orthogonal transform basis stored in said storage unit and identified based on the identification information;
• and
• a transfer unit configured to transfer the at least one orthogonal transform basis identified based on the identification information from said accumulation unit to said storage unit, only when the at least one orthogonal transform basis identified based on the identification information is not yet stored in said storage unit.

An image decoding circuit which decodes a coded stream, comprising:

• a decoding unit configured to decode, from the coded stream, identification information identifying each of a plurality of orthogonal transform bases for use in inverse orthogonal transform of the coded stream;
• an accumulation unit configured to store the plurality of orthogonal transform bases for use in the inverse orthogonal transform of the coded stream;
• a storage unit configured to store at least one orthogonal transform basis which is required for current inverse orthogonal transform of a current block, out of the orthogonal transform bases stored in said accumulation unit;
• an inverse orthogonal transform unit configured to perform the current inverse orthogonal transform using the at least one orthogonal transform basis stored in said storage unit and identified based on the identification information;
• and
• a transfer control unit configured to transfer, from said accumulation unit to said storage unit, the at least one orthogonal transform basis identified based on the identification information, only when the at least one orthogonal transform basis identified based on the identification information is not yet stored in said storage unit.

An image decoding method of decoding a coded stream, comprising:

• decoding, from the coded stream, identification information identifying each of a plurality of orthogonal transform bases for use in inverse orthogonal transform of the coded stream;
• storing, in an accumulation unit, the plurality of orthogonal transform bases for use in the inverse orthogonal transform of the coded stream;
• storing, in a storage unit, at least one orthogonal transform basis which is required for current inverse orthogonal transform of a current block, out of the orthogonal transform bases stored in the accumulation unit;
• performing, using a processor, the current inverse orthogonal transform using the at least one orthogonal transform basis stored in the storage unit and identified based on the identification information;
• and
• transferring, from the accumulation unit to the storage unit, the at least one orthogonal transform basis identified based on the identification information, only when the at least one orthogonal transform basis identified based on the identification information is not yet stored in the storage unit.

An image decoding apparatus comprising:

• a decoding unit configured to decode, from a coded stream, identification information identifying each of a plurality of orthogonal transform bases for use in inverse orthogonal transform of the coded stream;
• a pre-decoding unit configured to decode the identification information in the coded stream, prior to decoding performed by said decoding unit;
• an accumulation unit configured to store the plurality of orthogonal transform bases for use in the inverse orthogonal transform of the coded stream;
• a storage unit configured to store at least one orthogonal transform basis which is required for current inverse orthogonal transform of a current block, out of the orthogonal transform bases stored in said accumulation unit;
• and
• a control unit configured to cause said storage unit to store the at least one orthogonal transform basis, based on the identification information decoded by said pre-decoding unit.