Audio coding device and audio coding method, audio decoding device and audio decoding method, and program

An audio coding method performed by an audio coding device, comprising:

• a first windowing step of multiplying an audio signal by a first window function;
• a second windowing step of multiplying the audio signal by a second window function having a characteristic different from a characteristic of the first window function;
• a window selecting step of selecting the first window function or the second window function as an optimum window function based on the audio signal multiplied by processing of the first windowing step and the audio signal multiplied by processing of the second windowing step;
• a coding step of coding the frequency spectrum of the audio signal multiplied by the optimum window function;
• and
• a transiting step of transmitting the frequency spectrum coded by processing of the coding step and window function information representing the optimum window function.

A program for causing a computer to perform processing including:

• a first windowing step of multiplying an audio signal by a first window function;
• a second windowing step of multiplying the audio signal by a second window function having a characteristic different from a characteristic of the first window function;
• a window selecting step of selecting the first window function or the second window function as an optimum window function based on the audio signal multiplied by processing of the first windowing step and the audio signal multiplied by processing of the second windowing step;
• a coding step of coding the frequency spectrum of the audio signal multiplied by the optimum window function;
• and
• a transmission controlling step of controlling the transmission of the frequency spectrum coded by processing of the coding step and of window function information representing the optimum window function.

An audio decoding device, comprising:

• a receiving part that receives a coded spectrum which is obtained as a result of coding a frequency spectrum of an audio signal multiplied by a first window function or a second window function having a characteristic different from a characteristic of the first window function as an optimum window function, and window function information representing the first window function or the second window function as the optimum window function;
• a decoding part that decodes the coded spectrum received by the receiving part;
• a window selecting part that selects the optimum window function from the first window function and the second window function based on the window function information received by the receiving part;
• and
• a windowing part that generates the audio signal from an audio signal of the frequency spectrum obtained as a result of decoding performed by the decoding part based on the optimum window function selected by the window selecting part.

An audio decoding method performed by an audio coding device, comprising:

• a receiving step of receiving a coded spectrum which is obtained as a result of coding a frequency spectrum of an audio signal multiplied by a first window function or a second window function having a characteristic different from a characteristic of the first window function as an optimum window function and window function information representing the first window function or the second window function as the optimum window function;
• a decoding step of decoding the coded spectrum received by processing of the receiving step;
• a window selecting step of selecting the optimum window function from the first window function and the second window function based on the window function information received by the processing of the receiving step;
• and
• a windowing step of generating the audio signal from an audio signal of the frequency spectrum obtained as a result of decoding performed by processing of the decoding step based on the optimum window function selected by processing of the window selecting step.

A program for causing a computer to perform processing including:

• a reception controlling step of controlling reception of a coded spectrum which is obtained as a result of coding a frequency spectrum of an audio signal multiplied by a first window function or a second window function having a characteristic different from a characteristic of the first window function as an optimum window function and window function information representing the first window function or the second window function as the optimum window function;
• a decoding step of decoding the coded spectrum received by processing of the reception controlling step;
• a window selecting step of selecting the optimum window function from the first window function and the second window function based on the window function information received by the processing of the reception controlling step;
• and
• a windowing step of generating the audio signal from an audio signal of the frequency spectrum obtained as a result of decoding performed by processing of the decoding step based on the optimum window function selected by processing of the window selecting step.