Audio signal processing apparatus, audio signal processing method, and program for having the method executed by computer

An audio signal processing apparatus comprising:

• a central processing unit, wherein
• the central processing unit includes:
• a time stretch/pitch shift processing unit that performs each of at least one of time stretching and pitch shifting by carrying out sine or cosine oscillation of each frequency component on the basis of a result of frequency analysis of an input audio signal and a required time stretch/pitch shift amount, and performing a synthesis process;
• and
• a phase synchronization processing unit that performs phase synchronization process for adjusting a phase of a time stretch/pitch shift signal outputted by the time stretch/pitch shift processing unit and outputs a resulting signal, wherein
• the phase synchronization processing unit includes
• a reference signal generating unit that clips a waveform of an end portion in one frame from the input audio signal once every plurality of frames and transforms the clipped waveform of the end portion on the basis of the time stretch/pitch shift amount to generate and output a reference signal for the phase synchronization process,
• a cross-fade location calculating unit that calculates cross-fade locations for the phase synchronization process in the plurality of frames, and
• a cross-fade processing unit that performs a cross-fade process on the time stretch/pitch shift signal, wherein
• the cross-fade location calculating unit searches a tail portion of a time axis waveform of the time stretch/pitch shift signal in a plurality of frames for the cross-fade locations and detects the cross-fade locations, cross-fade locations being locations at which the time axis waveform of the time stretch/pitch shift signal in the plurality of frames is similar to a waveform of the reference signal on a time axis, and
• the cross-fade processing unit performs a cross-fade process in a range of a length corresponding to the waveform of the reference signal from the cross-fade position from the time stretch/pitch shift signal to the reference signal at each of the detected cross-fade locations.

An audio signal processing apparatus comprising:

• a central processing unit, wherein
• the central processing unit includes:
• a frequency band dividing unit that divides an input audio signal into a plurality of bands;
• a plurality of time stretch/pitch shift processing units that perform at least one of time stretching and pitch shifting respectively by carrying out sine or cosine oscillation of each frequency component on the basis of a result of frequency analysis of a band-divided audio signal obtained as a result of division into the plurality of bands and a required time stretch/pitch shift amount, and performing a synthesis process;
• and
• a plurality of phase synchronization processing units that perform phase synchronization process for adjusting phases of time stretch/pitch shift signals outputted by the plurality of time stretch/pitch shift processing units, respectively,
• the audio signal processing apparatus thereby synthesizing outputs of the plurality of phase synchronization processing units and outputting a result, wherein
• each of the phase synchronization processing units includes
• a phase synchronization signal generating unit that generates a phase synchronization, and
• a cross-fade processing unit that performs a cross-fade process on the time stretch/pitch shift signal, wherein
• the phase synchronization signal generating unit evaluates a difference in phase condition between an end portion of a waveform of the time stretch/pitch shift signal in a current frame on which the time stretch/pitch shift processing is performed and a waveform of the band-divided audio signal at a location where a next frame starts, by shifting the location at which the next frame of the waveform of the band-divided audio signal starts, along a time axis, calculates a time shift amount when the difference in phase condition is evaluated as the smallest clips of a signal waveform corresponding to a predetermined wavelength from the end portion of the band-divided audio signal, and generates at least one of a phase-lead signal and a phase-lag signal which is shifted by the time shift amount from the clipped waveform of the end portion as the phase synchronization signal, and
• the cross-fade processing unit that performs a cross-fade process from the time stretch/pitch shift signal to the phase synchronization signal in a range of the predetermined wavelength at the end portion of the time stretch/pitch shift signal.

An audio signal processing apparatus comprising:

• a central processing unit, wherein
• the central processing unit includes:
• a time stretch/pitch shift processing unit that performs each of at least one of time stretching and pitch shifting by carrying out sine or cosine oscillation of each frequency component on the basis of a result of frequency analysis of an input audio signal and a required time stretch/pitch shift amount, and performing a synthesis process;
• and
• a phase synchronization processing unit that performs phase synchronization process for adjusting a phase of a time stretch/pitch shift signal outputted by the time stretch/pitch shift processing unit and outputs a resulting signal, wherein
• the phase synchronization processing unit includes
• a phase synchronization signal generating unit that generates phase synchronization signal, and
• a cross-fade processing unit that performs a cross-fade process on the time stretch/pitch shift signal, wherein
• the phase synchronization signal generating unit evaluates a difference in phase condition between an end portion of a waveform of the time stretch/pitch shift signal in a current frame on which the time stretch/pitch shift processing is performed and a waveform of the band-divided audio signal at a location where a next frame starts, by shifting the location at which the next frame of the waveform of the band-divided audio signal starts, along a time axis, calculates a time shift amount when the difference in phase condition is evaluated as the smallest clips of a signal waveform corresponding to a predetermined wavelength from the end portion of the band-divided audio signal, and generates at least one of a phase-lead signal and a phase-lag signal which is shifted by the time shift amount from the clipped waveform of the end portion as the phase synchronization signal, and
• the cross-fade processing unit that performs a cross-fade process from the time stretch/pitch shift signal to the phase synchronization signal in a range of the predetermined wavelength at the end portion of the time stretch/pitch shift signal.

An audio signal processing method comprising:

• time stretching/pitch shifting of performing each of at least one of time stretching and pitch shifting by carrying out sine or cosine oscillation of each frequency component on the basis of a result of frequency analysis of an input audio signal and a required time stretch/pitch shift amount, and performing a synthesis process;
• and
• phase synchronization processing of performing a phase synchronization process for adjusting a phase of a time stretch/pitch shift signal on which time stretch/pitch shift processing is performed, wherein
• the phase synchronization processing includes
• reference signal generating of clipping a waveform of an end portion in one frame from the input audio signal once every plurality of frames and transforming the clipped waveform of the end portion on the basis of the time stretch/pitch shift amount to generate and output a reference signal for the phase synchronization process,
• cross-fade location calculating of calculating cross-fade locations for the phase synchronization process in the plurality of frames, and
• cross-fade processing of performing a cross-fade process on the time stretch/pitch shift signal, wherein
• the cross fade location calculating includes searching a tail portion of a time axis waveform of the time stretch/pitch shift signal in a plurality of frames for the cross fade locations and detects the cross-fade locations, cross-fade locations being locations at which the time axis waveform of the time stretch/pitch shift signal in the plurality of frames is similar to a waveform of the reference signal on a time axis, and
• the cross-fade processing includes performing a cross-fade process in a range of a length corresponding to the waveform of the reference signal from the cross-fade position from the time stretch/pitch shift signal to the reference signal at each of the detected cross-fade locations.

An audio signal processing method comprising:

• time stretching/pitch shifting of performing each of at least one of time stretching and pitch shifting by carrying out sine or cosine oscillation of each frequency component on the basis of a result of frequency analysis of an input audio signal and a required time stretch/pitch shift amount, and performing a synthesis process;
• and
• phase synchronization processing of performing a phase synchronization process for adjusting a phase of a time stretch/pitch shift signal on which time stretch/pitch shift processing is performed, wherein
• the phase synchronization processing includes
• phase synchronization signal generating of generating a phase synchronization signal, and
• cross-fade processing of performing a cross-fade process on the time stretch/pitch shift signal, wherein
• the phase synchronization processing further includes
• evaluating of evaluating a difference in phase condition between a waveform of an end portion of the time stretch/pitch shift signal in a current frame on which the time stretch/pitch shift processing is performed and a waveform of the input audio signal at a location where a next frame starts, by shifting the location where the next frame of the waveform of the input audio signal starts along a time axis, and
• time shift calculating of calculating a time shift amount when the difference in phase condition is evaluated as the smallest, wherein
• the phase synchronization signal generating includes clipping a signal waveform corresponding to a predetermined wavelength at the end portion of the input audio signal, and generating one of a phase-lead signal and a phase-lag signal which is shifted by the time shift amount from the clipped waveform of the end portion as a phase synchronization signal, and
• the cross-fade processing including performing a cross-fade process from the time stretch/pitch shift signal to the phase synchronizing signal in a range of the predetermined wavelength at the end portion of the time stretch/pitch shift signal.