Pitch emphasis apparatus, method and program for the same

A pitch emphasis apparatus that obtains an output signal having little unnaturalness to listeners by executing pitch enhancement processing on each of time segments of an input signal, the input signal being an audio signal obtained by decoding a code obtained by encoding, the apparatus comprising:

• a pitch enhancing unit that carries out the following as the pitch enhancement processing:
• obtaining an output signal for each of times n in each of the time segments, the output signal being a signal including a signal obtained by adding (1) a signal obtained by multiplying the signal of a time n−T0, further in the past than a time n by a number of samples T0 corresponding to a pitch period of the time segment, a pitch gain σ0 of the time segment, and a value that becomes smaller as the flatness of a spectral envelope of the time segment becomes higher, to (2) the signal of the time n.

A pitch emphasis method that obtains an output signal by having little unnaturalness to listeners executing pitch enhancement processing on each of time segments of an input signal, the input signal being an audio signal obtained by decoding a code obtained by encoding, the method comprising:

• a pitch enhancing step of carrying out the following as the pitch enhancement processing:
• obtaining an output signal for each of times n in each of the time segments, the output signal being a signal including a signal obtained by adding (1) a signal obtained by multiplying the signal of a time n−T0, further in the past than a time n by a number of samples T0 corresponding to a pitch period of the time segment, a pitch gain σ0 of the time segment, and a value that becomes smaller as the flatness of a spectral envelope of the time segment becomes higher, to (2) the signal of the time n.