Method and apparatus for separating sound-source signal and method and device for detecting pitch
In a sound-source signal separating method, a target sound-source signal in an input audio signal is enhanced, the input audio signal being from a mixture of acoustic signals from a plurality of sound sources picked up by a plurality of sound pickup devices. The pitch of the target sound-source signal in the input audio signal is detected, and the target sound-source signal is separated from the input audio signal based on the detected pitch and the enhanced sound-source signal.
1. A sound-source signal separating apparatus, comprising:
a sound-source signal enhancing unit operable to enhance a target sound-source signal in an input audio signal to produce an enhanced sound-source signal, the input audio signal including a mixture of acoustic signals from a plurality of sound sources picked up by a plurality of sound pickup devices;
a signal processor processing non-steady waveform signals only at a high frequency region in the enhanced sound-source signal by removing random portions from the non-steady waveform signals;
a pitch detector operable to detect a pitch of the target sound-source signal in the input audio signal; and
a sound-source signal separating unit operable to process signals at a middle and a lower frequency regions of the enhanced sound-source signal by separating the target sound-source signal from the input audio signal based on the detected pitch and the received middle and lower frequency signals of the enhanced sound-source signal,
where information detected by the pitch detector is used to control only the sound-source signal separating unit, and not the signal processor.
2. The sound-source signal separating apparatus according to claim 1 , wherein the sound-source signal separating unit comprises:
a filter for separating the target sound-source signal from a signal output from the sound-source signal enhancing unit; and
a filter coefficient output unit operable to output a filter coefficient of the filter based on information detected by the pitch detector.
3. The sound-source signal separating apparatus according to claim 2 , wherein the filter coefficient features a frequency characteristic of the filter which causes a frequency component to pass through the filter, the frequency component having a frequency which is an integer multiple of the frequency of the pitch of the target sound-source signal.
4. The sound-source signal separating apparatus according to claim 3 , wherein the filter coefficient output unit comprises a memory storing filter coefficients corresponding to a plurality of pitches, the filter coefficient output unit reading and outputting a filter coefficient from the memory corresponding to the pitch of the target sound-source signal.
5. The sound-source signal separating apparatus according to claim 2 , further comprising:
a high-frequency region processing unit operable to process a portion of the output signal in a consonant band; and
a filter bank operable to extract the portion of the output signal in the consonant band from the sound-source signal enhancing unit and to transfer the portion of the output signal in the consonant band to the high-frequency region processing unit, to extract a portion of the output signal in a band other than the consonant band from the sound-source signal enhancing unit and to transfer the portion of the output sound-source signal in the band other than the consonant band to the filter, and to extract a portion of the output signal in a vowel band from the sound-source signal enhancing unit and to transfer the portion of the output signal in the vowel band to the pitch detector.
6. The sound-source signal separating apparatus according to claim 2 , wherein the plurality of sound pickup devices comprise a left stereomicrophone and a right stereomicrophone.
7. The sound-source signal separating apparatus according to claim 2 , wherein the sound-source signal enhancing unit corrects the acoustic signals from the plurality of sound pickup devices with a time difference between sound propagation delays, each sound propagation delay being measured from a target sound source to each of the plurality of sound pickup devices, and adds the corrected acoustic signals from the plurality of sound pickup devices in order to enhance the acoustic signal from only the target sound source.
8. The sound-source signal separating apparatus according to claim 2 , wherein the pitch detector detects the pitch of the target sound-source signal using two wavelengths of the pitch of the target sound-source signal as a unit of detection.
9. The sound-source signal separating apparatus according to claim 1 , wherein the sound-source signal separating unit comprises:
a fundamental waveform producing unit operable to produce a fundamental waveform based on information detected by the pitch detector using a steady portion of a signal output from the sound-source signal enhancing unit, the steady portion having at least about the same pitch consecutively repeated throughout; and
a fundamental waveform substituting unit operable to substitute a repetition of the fundamental waveform produced by the fundamental waveform producing unit for at least a portion of a signal based on the input audio signal.
10. The sound-source signal separating apparatus according to claim 9 , wherein the pitch detector detects the pitch of the target sound-source signal using two wavelengths of the pitch of the target sound-source signal as a unit of detection.
11. The sound-source signal separating apparatus according to claim 9 , wherein the plurality of sound pickup devices comprise a left stereomicrophone and a right stereomicrophone.
12. The sound-source signal separating apparatus according to claim 9 , wherein the sound-source signal enhancing unit corrects the acoustic signals from the plurality of sound pickup devices with a time difference between sound propagation delays, each sound propagation delay being measured from a target sound source to each of the plurality of sound pickup devices, and adds the corrected acoustic signals from the plurality of sound pickup devices in order to enhance the acoustic signal from only the target sound source.
13. The sound-source signal separating apparatus according to claim 9 , wherein the fundamental waveform producing unit averages the target sound-source signal in a steady portion of the target sound-source signal having at least about the same pitch consecutively repeated throughout using two wavelengths of the pitch of the target sound-source signal as a unit of detection.
14. A sound-source signal separating method, comprising:
enhancing a target sound-source signal in an input audio signal to produce an enhanced sound-source signal, the input audio signal including a mixture of acoustic signals from a plurality of sound sources picked up by a plurality of sound pickup devices;
processing non-steady waveform signals only at a high frequency region in the enhanced sound-source signal by removing random portions from the non-steady waveform signals;
detecting a pitch of the target sound-source signal in the input audio signal; and
separating the target sound-source signal from the input audio signal based on the detected pitch and the signals at a middle and a lower frequency regions of the enhanced sound-source signal,
where information from the detected pitch is used to control only separating the target sound-source signal, not processing at a high frequency region in the enhanced sound-source signal.