Frame signal correcting method and apparatus without distortion

• US 8,738,373 B2
• Filed: 12/13/2006
• Issued: 05/27/2014
• Est. Priority Date: 08/30/2006
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Otani, Takeshi, Suzuki, Masanao
• Primary Examiner(s): Desir, Pierre-Louis
• Assistant Examiner(s): KOVACEK, DAVID M
• Application Number:
  US11/637,809
• Publication Number:
  US 20080059162A1
• Time in Patent Office: 2,722 Days
• Field of Search: 704200-218, 704224-230, 704246-250, 704/258, 704/268, 704/278, 704E19001-E19049, 704E21001-E2102, 704E11001-E11007, 381 711- 7114, 381/73.1, 381 941- 949, 381104-109
• 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 apparatus comprising:

a processor and a memory storing program code, the processor executing the program code to implement;

a first means that converts a first frame signal of a predetermined length to which a predetermined window function is performed into a frequency spectrum signal;

a second means that performs a noise suppressing to the frequency spectrum signal to generate a noise suppressed frequency spectrum signal;

a third means that converts the noise suppressed frequency spectrum signal into a second frame signal of a time domain by 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 the frame ends of the second frame signal,

a fourth means that provides a corrected frame signal before frame synthesizing by subtracting the adjusted correcting signal from the second frame signal, so that amplitudes of both or one of the frame ends of the second frame signal are made zero, wherein

the correcting signal is made by adding time domain signals each having a different frequency component, in which a frequency component of a waveform function of the added correcting signal corresponds to a low frequency component to be corrected in the second frame signal.

2. The signal processing apparatus as claimed in claim 1, 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.

3. The signal processing apparatus as claimed in claim 1, 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.

4. The signal processing apparatus 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 means includes a means decoding by converting the encoded frequency spectrum into the time domain to generate the second frame signal.

5. The signal processing apparatus 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, wherein

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.

6. The signal processing apparatus as claimed in claim 1, further comprising a means for 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.

7. A signal processing apparatus comprising:

a processor and a memory storing program code, the processor executing the program code to implement;

a first means that converts a first frame signal of a predetermined length to which a predetermined window function is performed into a frequency spectrum signal;

a second means that performs a noise suppressing to the frequency spectrum signal to generate a noise suppressed frequency spectrum signal;

a third means that converts the noise suppressed frequency spectrum signal into a second frame signal of a time domain; and

a fourth means that calculates an amplitude correction amount given by a square root of a difference between a power of a signal obtained by removing amplitudes of both or one of the frame ends of the second frame signal from the second frame signal and by a power of the noise suppressed frequency spectrum signal, and further calculates a corrected amplitude component for a low frequency component or a direct current component of the noise suppressed frequency spectrum signal by adding the amplitude correction amount to the low frequency component or the direct current component of the noise suppressed frequency spectrum signal, and converts the corrected amplitude component into a corrected frame signal of a time domain before frame synthesizing,

wherein the corrected amplitude component is utilized to generate a correcting signal is made by adding time domain signals each having a different frequency component, in which a frequency component of a waveform function of the added correcting signal corresponds to a low frequency component to be corrected in the second frame signal.

8. The signal processing apparatus as claimed in claim 7, 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.

9. The signal processing apparatus as claimed in claim 7, 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.

10. The signal processing apparatus as claimed in claim 7, 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.

11. The signal processing apparatus as claimed in claim 7, 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, wherein

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 apparatus as claimed in claim 7, 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.