Method and system for speech quality prediction of an audio transmission system

• US 20060171543A1
• Filed: 02/26/2004
• Published: 08/03/2006
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: Koninklijke KPN NV
• Original Assignee: Koninklijke KPN NV
• Inventors: Beerends, John Gerard, Van Den Homberg, Mars Jan Christiaan
• Granted Patent: US 7,313,517 B2
• Time in Patent Office: Days
• US Class Current: 381/58
• CPC Class Codes: G10L 25/69 for evaluating synthetic or decoded voice signals

Abstract

Method and system for measuring the transmission quality of an audio transmission system (10). Preprocessing means (12) are present for preprocessing of an input signal (X) and an output signal (Y) to obtain pitch power densities (PPXwIKss(j)” 1′PYwrR.ss(fin) for the respective signals. Compensation means (13, 14) are provided for compensation of linear frequency response and time varying gain. Calculation means (13, 14) are present for calculation of loudness densities (LX(I)n, LY(fi,,) from the compensated pitch power densities, and computation means (15, 16) are provided for computation of a score (Q) indicative of the transmission quality of the system (10) from the loudness densities. The compensation means (13, 14) comprise an iterative loop having at least three calculations of compensations, each calculation comprising one of a calculation of a compensation of linear frequency response and a calculation of a local power scaling factor.

Claims

1. Method for measuring the transmission quality of an audio transmission system (10), an input signal (X) being entered into the system (10), resulting in an output signal (Y), in which both the input signal (X) and the output signal (Y) are processed, comprising:

preprocessing of the input signal (X) and output signal (Y) to obtain pitch power densities (PPX_WIRSS(f)_n, PPY_WIRSS(f)_n) for the respective signals;

compensation of linear frequency response and time varying gain to obtain compensated pitch power densities (PPX″

_WIRSS(f)_n, PPY′

_WIRSS(f)_n), in which the compensation of linear frequency response and time varying gain comprises an iterative loop having at least three calculations of compensations, each calculation comprising one of a calculation of a compensation of linear frequency response and a calculation of a local power scaling factor;

computation of a score (Q) indicative of the transmission quality of the system (10) from the compensated pitch power densities (PPX″

_WIRSS(f)_n, PPY′

_WIRSS(f)_n).

2. Method according to claim 1, in which the iterative loop comprises a calculation of a first partial linear frequency compensation and application of the first partial linear frequency compensation to the pitch power density of the input signal (PPX_WIRSS(f)_n), followed by a calculation of a local power scaling factor and application of the local power scaling factor to the pitch power density of the output signal (PPY_WIRSS(f)_n), followed by a calculation of a second partial linear frequency compensation and application of the linear frequency compensation to the partially compensated pitch power density of the input signal (PPX′

_WIRSS(f)_n).

3. Method according to claim 1, in which the iterative loop comprises a calculation of a first partial linear frequency compensation and application of the first partial linear frequency compensation to the pitch power density of the output signal (PPY_WIRSS(f)_n), followed by a calculation of a local power scaling factor and application of the local power scaling factor to the pitch power density of the input signal (PPX_WIRSS(f)_n), followed by a calculation of a second partial linear frequency compensation and application of the linear frequency compensation to the partially compensated pitch power density of the output signal (PPY′

_WIRSS(f)_n).

4. Method according to claim 2, in which the first partial linear frequency compensation is a first estimate which is lower than a linear frequency compensation required for correct evaluation of the linear distortion.

5. Method according to claim 4, in which the first partial linear frequency compensation is a frequency dependent function.

11. Software program product comprising computer executable software code, which when loaded on a processing system, allows the processing system to execute the method according to claim 1.

6. System for measuring the transmission quality of an audio transmission system (10), an input signal (X) being entered into the system (10), resulting in an output signal (Y), comprising:

preprocessing means (12) for preprocessing of the input signal (X) and output signal (Y) to obtain pitch power densities (PPX_WIRSS(f)_n, PPY_WIRSS(f)_n) for the respective signals;

compensation means (13, 14) for compensation of linear frequency response and time varying gain to obtain compensated pitch power densities (PPX″

_WIRSS(f)_n, PPY′

_WIRSS(f)_n), comprising an iterative loop having at least three calculations of compensations, each calculation comprising one of a calculation of a compensation of linear frequency response and a calculation of a local power scaling factor; and

computation means (15, 16) for computation of a score (Q) indicative of the transmission quality of the system (10) from the compensated pitch power densities densities (PPX″

_WIRSS(f)_n, PPY′

_WIRSS(f)_n).

7. System according to claim 6, in which the iterative loop comprises a calculation of a first partial linear frequency compensation and application of the first partial linear frequency compensation to the pitch power density of the input signal (PPX_WIRSS(f)_n), followed by a calculation of a local power scaling factor and application of the local power scaling factor to the pitch power density of the output signal (PPY_WIRSS(f)_n), followed by a calculation of a second partial linear frequency compensation and application of the second partial linear frequency compensation to the partially compensated pitch power density of the input signal (PPX′

_WIRSS(f)_n).

8. System according to claim 6, in which the iterative loop comprises a calculation of a first partial linear frequency compensation and application of the first partial linear frequency compensation to the pitch power density of the output signal (PPY_WIRSS(f)_n), followed by a calculation of a local power scaling factor and application of the local power scaling factor to the pitch power density of the input signal (PPX_WIRSS(f)_n), followed by a calculation of a second partial linear frequency compensation and application of the second partial linear frequency compensation to the partially compensated pitch power density of the output signal (PPY′

_WIRSS(f)_n).

9. System according to claim 7, in which the first partial linear frequency compensation is a first estimate which is lower than a linear frequency compensation required for correct evaluation of the linear distortion.

10. System according to claim 9, in which the first partial linear frequency compensation is a frequency dependent function.