Method and apparatus for coding an information signal using pitch delay contour adjustment

• US 20070027680A1
• Filed: 07/27/2005
• Published: 02/01/2007
• Est. Priority Date: 07/27/2005
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Inventors: Mittal, Udar, Ashley, James
• Granted Patent: US 9,058,812 B2
• Time in Patent Office: Days
• US Class Current: 704/207
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 21/00 Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility G10L19/00 takes precedence
• CPC Class Codes: G10L 21/06 Transformation of speech into a non-audible representation, e.g. speech visualisation or speech processing for tactile aids G10L15/26 takes precedence

Abstract

In a speech encoder/decoder a pitch delay contour endpoint modifier is employed to shift the endpoints of a pitch delay interpolation curve up or down. Parficularly, the endpoints of the pitch delay interpolation curve are shifted based on a variation and/or a standard deviation in pitch delay.

Claims

1. A method of operating a speech encoder, the method comprising the steps of:

estimating a pitch delay based on an input signal;

estimating a variation in pitch delay based on the pitch delay estimate;

determining an adaptive step size value based on the variation in pitch delay; and

generating an encoded pitch parameter based on the adaptive step size.

2. The method of claim 1 wherein the step of estimating the pitch delay based on the input signal comprises the step of estimating the pitch delay based on either a speech or an audio signal.

3. The method of claim 1 wherein the step of estimating the variation in pitch delay comprises the step of estimating a variation and/or standard deviation in pitch delay.

4. The method of claim 1 wherein the step of determining the adaptive step size comprises the step of determining the adaptive step size δ

m), where δ

m) may be expressed as;

5. The method of claim 4 wherein α

(σ

_τ

)=min(Å

σ

_τ

+B, α

_max) where A and B are predetermined values, σ

₉₆, represents the standard deviation in τ

, and α

_max is a maximum allowable value of α

(σ

_τ

).

6. The method of claim 1 wherein the step of generating an encoded pitch parameter based on the adaptive step size comprises the step of determining a delay adjust value Δ

_adj where

Δ

_adj(i)=(i−

M/2). δ

(m), i∈

{0, 1, . . . , M−

1}

and where M is the number of candidate pitch delay adjustment indices, δ

(m) is the adaptive step-size, and i ∈

{0, 1, . . . , M−

1} is the encoded pitch parameter.

7. The method of claim 6 wherein the delay adjust value Δ

_adj is used to shift the endpoints of the pitch delay interpolation curve up or down according to the expression;

d′

(m′

,j)=d(m′

,j)+Δ

_adj(i)

where d(m′

, j) is a subframe delay interpolation endpoint matrix.

8. The method of claim 1 wherein the step of generating an encoded pitch parameter based on the adaptive step size comprises the step of evaluating a distortion criteria.

9. The method of claim 8 wherein the step of evaluating the distortion criteria comprises the step of evaluating one of the set of the minimization of a mean squared error parameter, the minimization of an accumulated shift parameter, and the maximization of a normalized cross correlation parameter.

10. A method of operating a speech decoder, the method comprising the steps of:

receiving a first pitch delay parameter;

estimating a variation in pitch delay based on the first pitch delay parameter;

determining an adaptive step size based on the variation in pitch delay; and

generating a second pitch delay parameter based on the adaptive step size.

11. The method of claim 10 wherein the step of estimating the variation in pitch delay comprises the step of estimating a variation and/or standard deviation in pitch delay.

12. The method of claim 10 wherein the step of determining the adaptive step size comprises the step of determining the adaptive step size δ

(m), where δ

(m) may be expressed as;

13. The method of claim 12 wherein α

(σ

_τ

)=min(Aσ

_τ

+B, α

_max) where A and B are predetermined, σ

_τ

represents the standard deviation in τ

, and α

_max is a maximum allowable value of α

(σ

_τ

).

14. The method of claim 10 wherein the step of generating the second pitch delay parameter based on the adaptive step size comprises the step of determining a delay adjust value Δ

_adj where

Δ

_adj(i)=(i−

M/2). δ

(m), i∈

{0, 1, . . . , M−

1}

and where M is the number of candidate pitch delay adjustment indices, and δ

(m) is the adaptive step-size.

15. The method of claim 14 wherein the delay adjust value Δ

_adj is used to shift the endpoints of the pitch delay interpolation curve up or down according to the expression;

d′

(m′

,j)=d(m′

,j)+Δ

_adj(i)

where d(m′

, j) is a subframe delay interpolation endpoint matrix, and d′

(m′

,j) is the second pitch delay parameter.

16. An apparatus comprising:

a variability estimator estimating a variation in pitch delay;

a coefficient generator determining an adaptive step size based on the variation in pitch delay; and

modification circuitry modifying a pitch parameter based on the adaptive step size.

17. The apparatus of claim 16 wherein the modification circuitry modifies endpoints of a pitch delay interpolation curve up or down based on the adaptive step size.

18. The apparatus of claim 16 wherein the pitch delay is based either a speech or an audio signal.

19. The apparatus of claim 16 wherein the variation in pitch delay comprises a variation and/or standard deviation in pitch delay.

20. The apparatus of claim 16 wherein the adaptive step size is computed as