System for bandwidth extension of narrow-band speech

• US 8,595,001 B2
• Filed: 11/07/2011
• Issued: 11/26/2013
• Est. Priority Date: 10/04/2001
• Status: Expired due to Term

• Current Assignee: Cerence Operating Company (Cerence Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Malah, David, Cox, Richard Vandervoort
• Primary Examiner(s): Abebe, Daniel D
• Application Number:
  US13/290,464
• Publication Number:
  US 20120116769A1
• Time in Patent Office: 750 Days
• Field of Search: 704/200, 704/219, 375/245
• US Class Current: 704/219
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

A method applies a parametric approach to bandwidth extension but does not require training. The method computes narrowband linear predictive coefficients from a received narrowband speech signal, computes narrowband partial correlation coefficients using recursion, computes M_nb area coefficients from the partial correlation coefficient, and extracts M_wb area coefficients using interpolation. Wideband parcors are computed from the M_wb area coefficients and wideband LPCs are computed from the wideband parcors. The method further comprises synthesizing a wideband signal using the wideband LPCs and a wideband excitation signal, highpass filtering the synthesized wideband signal to produce a highband signal, and combining the highband signal with the original narrowband signal to generate a wideband signal.

Claims

1. A method comprising:

computing, via a processor, linear predictive coefficients from a received signal;

recursively computing partial correlation coefficients based on the linear predictive coefficients;

computing narrow area coefficients from the partial correlation coefficients;

computing wide area coefficients via interpolation of the narrow area coefficients; and

synthesizing a wideband signal using the wide area coefficients.

2. The method of claim 1, wherein the interpolation of the narrow area coefficients comprises one of a fractal interpolation scheme and a cubic spline interpolation scheme.

3. The method of claim 1, wherein the received signal is a narrowband signal.

4. The method of claim 1, wherein computing linear predictive coefficients is based on a narrowband sampling rate.

5. The method of claim 4, wherein the interpolation of the narrow area coefficients comprises changing the wide area coefficients from the narrowband sampling rate to a wideband sampling rate.

6. The method of claim 1, wherein the interpolation of the narrow area coefficients comprises use of a zero-order polynomial.

7. The method of claim 1, wherein recursively computing partial correlation coefficients comprises using Step-Down back-recursion.

8. A system comprising:

a processor; and

a computer-readable storage medium having instructions stored which, when executed by the processor, cause the processor to perform operations comprising;

computing linear predictive coefficients from a received signal;

recursively computing partial correlation coefficients based on the linear predictive coefficients;

computing narrow area coefficients from the partial correlation coefficients;

computing wide area coefficients via interpolation of the narrow area coefficients; and

synthesizing a wideband signal using the wide area coefficients.

9. The system of claim 8, wherein the interpolation of the narrow area coefficients comprises one of a fractal interpolation scheme and a cubic spline interpolation scheme.

10. The system of claim 8, wherein the received signal is a narrowband signal.

11. The system of claim 8, wherein computing linear predictive coefficients is based on a narrowband sampling rate.

12. The system of claim 11, wherein the interpolation of the narrow area coefficients comprises changing the wide area coefficients from the narrowband sampling rate to a wideband sampling rate.

13. The system of claim 8, wherein the interpolation of the narrow area coefficients comprises use of a zero-order polynomial.

14. The system of claim 8, wherein recursively computing partial correlation coefficients comprises using Step-Down back-recursion.

15. A computer-readable storage device having instructions stored which, when executed by a computing device, cause the computing device to perform operations comprising:

computing linear predictive coefficients from a received signal;

recursively computing partial correlation coefficients based on the linear predictive coefficients;

computing narrow area coefficients from the partial correlation coefficients;

computing wide area coefficients via interpolation of the narrow area coefficients; and

synthesizing a wideband signal using the wide area coefficients.

16. The computer-readable storage device of claim 15, wherein the interpolation of the narrow area coefficients comprises one of a fractal interpolation scheme and a cubic spline interpolation scheme.

17. The computer-readable storage device of claim 15, wherein the received signal is a narrowband signal.

18. The computer-readable storage device of claim 15, wherein computing linear predictive coefficients is based on a narrowband sampling rate.

19. The computer-readable storage device of claim 18, wherein the interpolation of the narrow area coefficients comprises changing the wide area coefficients from the narrowband sampling rate to a wideband sampling rate.

20. The computer-readable storage device of claim 15, wherein the interpolation of the narrow area coefficients comprises use of a zero-order polynomial.