Signal processing method and apparatus

• US 20080059162A1
• Filed: 12/13/2006
• Published: 03/06/2008
• Est. Priority Date: 08/30/2006
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Suzuki, Masanao, Otani, Takeshi
• Granted Patent: US 8,738,373 B2
• Time in Patent Office: Days
• US Class Current: 704/226
• CPC Class Codes: G10L 21/0208 Noise filtering

Abstract

In a signal processing method and apparatus, a predetermined correcting signal having a same frame length as a second frame signal in which predetermined processing is performed to a frequency spectrum of a first frame signal of a frame length to which a predetermined window function is performed and is converted into a time domain is adjusted so that amplitudes of both ends of the correcting signal become equal to amplitudes of both or one of frame ends of the second frame signal, and a corrected frame signal is obtained by subtracting an adjusted correcting signal from the second frame signal.

Claims

1. A signal processing method comprising:

a first step of performing predetermined processing to a frequency spectrum of a first frame signal of a predetermined length to which a predetermined window function is performed, to be converted into a time domain to generate a second frame signal; and

a second step of adjusting a predetermined correcting signal having a same frame length as the second frame signal so that amplitudes of both ends of the correcting signal substantially become equal to amplitudes of both or one of frame ends of the second frame signal, and of correcting the second frame signal by subtracting the adjusted correcting signal from the second frame signal.

2. The signal processing method as claimed in claim 1, wherein an amplitude component of the correcting signal includes only a low frequency component.

3. The signal processing method as claimed in claim 1, wherein an amplitude component of the correcting signal includes only a direct current component.

7. The signal processing method as claimed in claim 1, wherein the first step includes a step of converting the first frame signal into a frequency domain to generate a first frequency spectrum,

a step of generating a second frequency spectrum in which the predetermined processing is performed to the first frequency spectrum, and

a step of converting the second frequency spectrum into the time domain to generate the second frame signal.

8. The signal processing method as claimed in claim 1, wherein the predetermined processing of the first step estimates a noise spectrum from an amplitude component of the frequency spectrum of the first frame signal, and suppresses noise within an amplitude component of the frequency spectrum of the first frame signal based on the noise spectrum.

9. The signal processing method as claimed in claim 1, wherein the predetermined processing of the first step comprises calculating a suppression coefficient for suppressing an echo by comparing an amplitude component of a frequency spectrum of a reference frame signal to which the predetermined window function is performed with the amplitude component of the frequency spectrum of the first frame signal, and multiplying the amplitude component of the frequency spectrum of the first frame signal by the suppression coefficient.

10. The signal processing method as claimed in claim 1, wherein the first frame signal comprises a voice signal or an acoustic signal to which the predetermined window function is performed, the predetermined processing comprises encoding for the frequency spectrum of the first frame signal, and the first step includes a step of decoding by converting the encoded frequency spectrum into the time domain to generate the second frame signal.

11. The signal processing method as claimed in claim 1, wherein the first frame signal comprises a phonemic piece corresponding to one phonetic character string of a plurality of phonetic character strings generated by analyzing an arbitrary character string, the phonemic piece being extracted from a voice dictionary in which all phonetic character strings estimated and phonetic pieces corresponding thereto are recorded and to which the predetermined window function is performed,

a frame signal adjacent to the first frame signal with a partial overlap with each other comprises a phonemic piece corresponding to another phonetic character string of the phonetic character strings, the phonemic piece being extracted from the voice dictionary and to which the predetermined window function is performed, and

the predetermined processing comprises determining a connection order of the phonemic pieces from a length and a pitch generated from the phonetic character strings, calculating an amplitude correction coefficient for mutually connecting the frequency spectrums of the phonetic pieces smoothly based on the connection order, and multiplying the amplitude component of the frequency spectrum of each phonemic piece by each amplitude correction coefficient.

12. The signal processing method as claimed in claim 1, further comprising a step of adding overlap portions of a frame signal obtained by correcting a present frame signal, and a frame signal obtained by correcting a frame signal immediately before the present frame signal, where the frame signal and the adjacent frame signal partially overlap with each other.

4. A signal processing method comprising:

a first step of performing predetermined processing to a frequency spectrum of a first frame signal of a predetermined length to which a predetermined window function is performed, to be converted into a time domain to generate a second frame signal;

a second step of inputting the frequency spectrum to which the predetermined processing is performed and the second frame signal, and of correcting an amplitude component of the frequency spectrum to which the predetermined processing is performed so that amplitudes of both or one of frame ends of the second frame signal substantially become null; and

a third step of converting the corrected frequency spectrum into a time domain.

5. The signal processing method as claimed in claim 4, wherein the second step comprises correcting an amplitude component corresponding to a low frequency bandwidth of the frequency spectrum to which the predetermined processing is performed.

6. The signal processing method as claimed in claim 4, wherein the second step comprises correcting only an amplitude corresponding to a direct current component of the frequency spectrum to which the predetermined processing is performed.

25. The signal processing method as claimed in claim 4, wherein the first step includes a step of converting the first frame signal into a frequency domain to generate a first frequency spectrum,

a step of generating a second frequency spectrum in which the predetermined processing is performed to the first frequency spectrum, and

a step of converting the second frequency spectrum into the time domain to generate the second frame signal.

26. The signal processing method as claimed in claim 4, wherein the predetermined processing of the first step estimates a noise spectrum from an amplitude component of the frequency spectrum of the first frame signal, and suppresses noise within an amplitude component of the frequency spectrum of the first frame signal based on the noise spectrum.

27. The signal processing method as claimed in claim 4, wherein the predetermined processing of the first step comprises calculating a suppression coefficient for suppressing an echo by comparing an amplitude component of a frequency spectrum of a reference frame signal to which the predetermined window function is performed with the amplitude component of the frequency spectrum of the first frame signal, and multiplying the amplitude component of the frequency spectrum of the first frame signal by the suppression coefficient.

28. The signal processing method as claimed in claim 4, wherein the first frame signal comprises a voice signal or an acoustic signal to which the predetermined window function is performed, the predetermined processing comprises encoding for the frequency spectrum of the first frame signal, and the first step includes a step of decoding by converting the encoded frequency spectrum into the time domain to generate the second frame signal.

29. The signal processing method as claimed in claim 4, wherein the first frame signal comprises a phonemic piece corresponding to one phonetic character string of a plurality of phonetic character strings generated by analyzing an arbitrary character string, the phonemic piece being extracted from a voice dictionary in which all phonetic character strings estimated and phonetic pieces corresponding thereto are recorded and to which the predetermined window function is performed,

a frame signal adjacent to the first frame signal with a partial overlap with each other comprises a phonemic piece corresponding to another phonetic character string of the phonetic character strings, the phonemic piece being extracted from the voice dictionary and to which the predetermined window function is performed, and

the predetermined processing comprises determining a connection order of the phonemic pieces from a length and a pitch generated from the phonetic character strings, calculating an amplitude correction coefficient for mutually connecting the frequency spectrums of the phonetic pieces smoothly based on the connection order, and multiplying the amplitude component of the frequency spectrum of each phonemic piece by each amplitude correction coefficient.

30. The signal processing method as claimed in claim 4, further comprising a step of adding overlap portions of a frame signal obtained by correcting a present frame signal, and a frame signal obtained by correcting a frame signal immediately before the present frame signal, where the frame signal and the adjacent frame signal partially overlap with each other.

13. A signal processing apparatus comprising:

a first means performing predetermined processing to a frequency spectrum of a first frame signal of a predetermined length to which a predetermined window function is performed, to be converted into a time domain to generate a second frame signal; and

a second means adjusting a predetermined correcting signal having a same frame length as the second frame signal so that amplitudes of both ends of the correcting signal substantially become equal to amplitudes of both or one of frame ends of the second frame signal, and correcting the second frame signal by subtracting the adjusted correcting signal from the second frame signal.

14. The signal processing apparatus as claimed in claim 13, wherein an amplitude component of the correcting signal includes only a low frequency component.

15. The signal processing apparatus as claimed in claim 13, wherein an amplitude component of the correcting signal includes only a direct current component.

19. The signal processing apparatus as claimed in claim 13, wherein the first means includes a means converting the first frame signal into a frequency domain to generate a first frequency spectrum,

a means generating a second frequency spectrum in which the predetermined processing is performed to the first frequency spectrum, and

a means converting the second frequency spectrum into the time domain to generate the second frame signal.

20. The signal processing apparatus as claimed in claim 13, wherein the predetermined processing of the first means estimates a noise spectrum from an amplitude component of the frequency spectrum of the first frame signal, and suppresses noise within an amplitude component of the frequency spectrum of the first frame signal based on the noise spectrum.

21. The signal processing apparatus as claimed in claim 13, wherein the predetermined processing of the first means comprises calculating a suppression coefficient for suppressing an echo by comparing an amplitude component of a frequency spectrum of a reference frame signal to which the predetermined window function is performed with the amplitude component of the frequency spectrum of the first frame signal, and multiplying the amplitude component of the frequency spectrum of the first frame signal by the suppression coefficient.

22. The signal processing apparatus as claimed in claim 13, wherein the first frame signal comprises a voice signal or an acoustic signal to which the predetermined window function is performed, the predetermined processing comprises encoding for the frequency spectrum of the first frame signal, and the first means includes a means decoding by converting the encoded frequency spectrum into the time domain to generate the second frame signal.

23. The signal processing apparatus as claimed in claim 13, wherein the first frame signal comprises a phonemic piece corresponding to one phonetic character string of a plurality of phonetic character strings generated by analyzing an arbitrary character string, the phonemic piece being extracted from a voice dictionary in which all phonetic character strings estimated and phonetic pieces corresponding thereto are recorded and to which the predetermined window function is performed,

a frame signal adjacent to the first frame signal with a partial overlap with each other comprises a phonemic piece corresponding to another phonetic character string of the phonetic character strings, the phonemic piece being extracted from the voice dictionary and to which the predetermined window function is performed, and

the predetermined processing comprises determining a connection order of the phonemic pieces from a length and a pitch generated from the phonetic character strings, calculating an amplitude correction coefficient for mutually connecting the frequency spectrums of the phonetic pieces smoothly based on the connection order, and multiplying the amplitude component of the frequency spectrum of each phonemic piece by each amplitude correction coefficient.

24. The signal processing apparatus as claimed in claim 13, further comprising a means adding overlap portions of a frame signal obtained by correcting a present frame signal, and a frame signal obtained by correcting a frame signal immediately before the present frame signal, where the frame signal and the adjacent frame signal partially overlap with each other.

16. A signal processing apparatus comprising:

a first means performing predetermined processing to a frequency spectrum of a first frame signal of a predetermined length to which a predetermined window function is performed, to be converted into a time domain to generate a second frame signal;

a second means inputting the frequency spectrum to which the predetermined processing is performed and the second frame signal, and correcting an amplitude component of the frequency spectrum to which the predetermined processing is performed so that amplitudes of both or one of frame ends of the second frame signal substantially become null; and

a third means converting the corrected frequency spectrum into a time domain.

17. The signal processing apparatus as claimed in claim 16, wherein the second means comprises correcting an amplitude component corresponding to a low frequency bandwidth of the frequency spectrum to which the predetermined processing is performed.

18. The signal processing apparatus as claimed in claim 16, wherein the second means comprises correcting only an amplitude corresponding to a direct current component of the frequency spectrum to which the predetermined processing is performed.

31. The signal processing apparatus as claimed in claim 16, wherein the first means includes a means converting the first frame signal into a frequency domain to generate a first frequency spectrum,

a means generating a second frequency spectrum in which the predetermined processing is performed to the first frequency spectrum, and

a means converting the second frequency spectrum into the time domain to generate the second frame signal.

32. The signal processing apparatus as claimed in claim 16, wherein the predetermined processing of the first means estimates a noise spectrum from an amplitude component of the frequency spectrum of the first frame signal, and suppresses noise within an amplitude component of the frequency spectrum of the first frame signal based on the noise spectrum.

33. The signal processing apparatus as claimed in claim 16, wherein the predetermined processing of the first means comprises calculating a suppression coefficient for suppressing an echo by comparing an amplitude component of a frequency spectrum of a reference frame signal to which the predetermined window function is performed with the amplitude component of the frequency spectrum of the first frame signal, and multiplying the amplitude component of the frequency spectrum of the first frame signal by the suppression coefficient.

34. The signal processing apparatus as claimed in claim 16, wherein the first frame signal comprises a voice signal or an acoustic signal to which the predetermined window function is performed, the predetermined processing comprises encoding for the frequency spectrum of the first frame signal, and the first means includes a means decoding by converting the encoded frequency spectrum into the time domain to generate the second frame signal.

35. The signal processing apparatus as claimed in claim 16, wherein the first frame signal comprises a phonemic piece corresponding to one phonetic character string of a plurality of phonetic character strings generated by analyzing an arbitrary character string, the phonemic piece being extracted from a voice dictionary in which all phonetic character strings estimated and phonetic pieces corresponding thereto are recorded and to which the predetermined window function is performed,

a frame signal adjacent to the first frame signal with a partial overlap with each other comprises a phonemic piece corresponding to another phonetic character string of the phonetic character strings, the phonemic piece being extracted from the voice dictionary and to which the predetermined window function is performed, and

the predetermined processing comprises determining a connection order of the phonemic pieces from a length and a pitch generated from the phonetic character strings, calculating an amplitude correction coefficient for mutually connecting the frequency spectrums of the phonetic pieces smoothly based on the connection order, and multiplying the amplitude component of the frequency spectrum of each phonemic piece by each amplitude correction coefficient.

36. The signal processing apparatus as claimed in claim 16, further comprising a means adding overlap portions of a frame signal obtained by correcting a present frame signal, and a frame signal obtained by correcting a frame signal immediately before the present frame signal, where the frame signal and the adjacent frame signal partially overlap with each other.