Method for changing speed and pitch of speech and speech synthesis system
This application relates to a method of synthesizing a speech of which a speed and a pitch are changed. In one aspect, the method includes a spectrogram may be generated by performing a short-time Fourier transformation on a first speech signal based on a first hop length and a first window length, and speech signals of sections having a second window length at the interval of a second hop length from the spectrogram. A ratio between the first hop length and the second hop length may be set to be equal to the value of a playback rate and a ratio between the first window length and the second window length may be set to be equal to the value of a pitch change rate, thereby generating a second speech signal of which the speed and the pitch are changed.
1. A method comprising:
setting sections having a first window length based on a first hop length in a first speech signal;
generating spectrograms by performing a short-time Fourier transformation on the sections;
determining a playback rate and a pitch change rate to change a speed and a pitch of the first speech signal, respectively;
generating speech signals of sections having a second window length based on a second hop length from the spectrograms; and
generating a second speech signal of which a speed and a pitch are changed on the speech signals of the sections,
wherein a ratio between the first hop length and the second hop length is set to be equal to a value of the playback rate, and wherein a ratio between the first window length and the second window length is set to be equal to a value of the pitch change rate.
2. The method of claim 1 , wherein a value of the second hop length corresponds to a preset value, and wherein the first hop length is set to be equal to a value obtained by multiplying the second hop length by the playback rate.
3. The method of claim 1 , wherein a value of the first window length corresponds to a preset value, and wherein the second window length is set to be equal to a value obtained by dividing the first window length by the pitch change rate.
4. The method of claim 1 , wherein the generating of the speech signals of the sections having the second window length comprises:
estimating phase information by repeatedly performing a short-time Fourier transformation and an inverse short-time Fourier transformation on the spectrograms; and
generating speech signals of the sections having the second window length based on the second hop length based on the phase information.