Granted Patent B2

US 8,190,426 · App. 11/948,137 · Granted May 29, 2012

Abstract

Claims (66)

1. A method of processing an audio signal, comprising:

converting the audio signal from a continuous domain to a frequency domain and obtaining sub-band short-time spectra for a predetermined number of sub-bands of the audio signal;

delaying at least one of the sub-band short-time spectra to obtain a predetermined number of time-delayed sub-band short-time spectra for at least one of the predetermined number of sub-bands; and

filtering the sub-band short-time spectrum and the time-delayed sub-band shorttime spectra to obtain a refined sub-band short-time spectrum for the at least one of the predetermined number of sub-bands.

2. The method of claim 1 , where converting comprises:

windowing the audio signal to a windowed signal; and

discrete Fourier transforming the windowed signal to the sub-band short-time spectra.

3. The method of claim 2 , where windowing comprises a Hann window function, a Hamming window function, or a Gaussian window function.

4. The method of claim 1 , where filtering comprises selecting a portion of the sub-band short-time spectrum and time-delayed sub-band short-time spectra through a finite impulse response.

5. The method of claim 1 , where filtering comprises multiplying filtering coefficients of a refinement matrix with the sub-band short-time spectrum and the time delayed sub-band short-time spectra.

6. A method of processing an audio signal, comprising:

converting the audio signal from a continuous domain to a frequency domain and obtaining sub-band short-time spectra for a predetermined number of sub-bands of the audio signal;

delaying at least one of the sub-band short-time spectra to obtain a predetermined number of time-delayed sub-band short-time spectra for at least one of the predetermined number of sub-bands;

selecting neighbored sub-bands of the sub-band short-time spectra;

filtering, for each pair of neighbored sub-bands, the sub-band short-time spectrum and the time-delayed sub-band short-time spectra to obtain a first filtered spectrum and a second filtered spectrum; and

adding the first and second filtered spectra to obtain a refined sub-band short-time spectrum for each pair of neighbored sub-bands.

7. The method of claim 6 , where filtering for each pair of neighbored sub-bands comprises multiplying filtering coefficients of a refinement matrix with the sub-band short-time spectrum and the time-delayed sub-band short-time spectra.

8. The method of claim 6 , where converting comprises:

windowing the audio signal to a windowed signal; and

discrete Fourier transforming the windowed signal to the sub-band short-time spectra.

9. The method of claim 8 , where windowing comprises a Hann window function, a Hamming window function, or a Gaussian window function.

10. The method of claim 6 , where filtering for each pair of neighbored sub-bands comprises selecting a portion of the sub-band short-time spectrum and time-delayed subband short-time spectra through a finite impulse response.

11. A method of processing an audio signal, comprising:

determining a degree of stationarity of the audio signal;

filtering the audio signal to obtain filtered sub-band short-time spectra, if the degree of stationarity is below a predetermined threshold;

if the degree of stationarity is equal to or greater than the predetermined threshold:

converting the audio signal from a continuous domain to a frequency domain and obtaining sub-band short-time spectra for a predetermined number of subbands of the audio signal;

delaying at least one of the sub-band short-time spectra to obtain a predetermined number of time-delayed sub-band short-time spectra for at least one of the predetermined number of sub-bands;

filtering the sub-band short-time spectrum and the time-delayed sub-band short-time spectra to obtain a refined sub-band short-time spectrum for the at least one of the predetermined number of sub-bands; and

filtering the refined sub-band short-time spectrum to obtain the filtered sub-band short-time spectra;

converting the filtered sub-band short-time spectra from the frequency domain to the continuous domain and obtaining an intermediate audio signal; and

synthesizing the intermediate audio signal to obtain an output audio signal.

12. The method of claim 11 , where the output audio signal comprises a noise reduced signal or an echo reduced signal.

13. The method of claim 11 , where converting the filtered sub-band short-time spectra comprises inverse Fourier transforming the filtered sub-band short-time spectra to the intermediate audio signal.

14. The method of claim 11 , where converting the audio signal comprises:

windowing the audio signal to a windowed signal; and

discrete Fourier transforming the windowed signal to the sub-band short-time spectra.

15. The method of claim 11 , where filtering the sub-band short-time spectrum and the time-delayed sub-band short-time spectra comprises selecting a portion of the sub-band short-time spectrum and time-delayed sub-band short-time spectra through a finite impulse response.

16. A method of processing an audio signal, comprising:

converting the audio signal from a continuous domain to a frequency domain and obtaining sub-band short-time spectra for a predetermined number of sub-bands of the audio signal;

delaying at least one of the sub-band short-time spectra to obtain a predetermined number of time-delayed sub-band short-time spectra for at least one of the predetermined number of sub-bands;

filtering the sub-band short-time spectrum and the time-delayed sub-band shorttime spectra to obtain a refined sub-band short-time spectrum for the at least one of the predetermined number of sub-bands;

determining a short-time spectrogram of the refined sub-band short-time spectrum; and

estimating a pitch of the audio signal, based on the short-time spectrogram.

17. A system for processing an audio signal comprising:

transformation logic comprising a processor that converts the audio signal from a continuous domain to a frequency domain and generates sub-band short-time spectra for a predetermined number of sub-bands of the audio signal;

delay logic that time shifts at least one of the sub-band short-time spectra to obtain a predetermined number of time-delayed sub-band short-time spectra for at least one of the predetermined number of sub-bands; and

refinement logic that filters the sub-band short-time spectrum and the time delayed sub-band short-time spectra to obtain a refined sub-band short-time spectrum for the at least one of the predetermined number of sub-bands.

18. The system of claim 17 , where the transformation logic comprises:

windowing logic that selects portions of the audio signal to a windowed signal; and

conversion logic that discrete Fourier transforms the windowed signal to the subband short-time spectra.

19. The system of claim 18 , where the windowing logic comprises a Hann window function, a Hamming window function, or a Gaussian window function.

20. The system of claim 17 , where the refinement logic comprises a finite impulse response filter.

21. The system of claim 17 , where the refinement logic comprises a first multiplication logic that multiplies filtering coefficients of a refinement matrix with the sub-band short-time spectrum and the time-delayed sub-band short-time spectra.

22. The system of claim 17 , further comprising:

interpolation logic that filters the sub-band short-time spectrum and the time delayed sub-band short-time spectra for each pair of selected neighbored sub-bands to obtain a first filtered spectrum and a second filtered spectrum; and

an adder that sums the first and second filtered spectra to obtain an additional sub-band short-time spectrum for each pair of the selected neighbored sub-bands.

23. The system of claim 22 , where the interpolation logic comprises a second multiplication circuit that multiplies filtering coefficients of a refinement matrix with the sub-band short-time spectrum and the time-delayed sub-band short-time spectra.

24. The system of claim 17 , further comprising:

change analysis logic that determines a degree of stationarity of the audio signal;

sub-threshold stationarity logic that filters the audio signal to obtain filtered subband short-time spectra, if the degree of stationarity is below a predetermined threshold;

super-threshold stationarity logic that filters the refined sub-band short-time spectrum to obtain the filtered sub-band short-time spectra, if the degree of stationarity is equal to or greater than the predetermined threshold; and

inverse conversion logic that transforms the filtered sub-band short-time spectra from the frequency domain to the continuous domain to obtain an output audio signal, the output audio signal comprising a noise reduced signal or an echo reduced signal.

25. The system of claim 17 , further comprising:

frequency analysis logic that determines a short-time spectrogram of the refined sub-band short-time spectrum; and

sound analysis logic that estimates a pitch of the audio signal, based on the short-time spectrogram.

Assignments (10)