Method and apparatus for performing harmonic noise weighting in digital speech coders
View Patent ↗To address the need for choosing values of harmonic noise weighting (HNW) coefficient (ε p ) so that the amount of harmonic noise weighting can be optimized, a method and apparatus for performing harmonic noise weighting in digital speech coders is provided herein. During operation, received speech is analyzed to determine a pitch period. HNW coefficients are then chosen based on the pitch period, and a perceptual noise weighting filter (C(z)) is determined based on the harmonic-noise weighting (HNW) coefficients (ε p ).
1. A method for performing harmonic noise weighting in a digital speech coder, the method comprising the steps of:
receiving a speech input s(n);
determining a pitch period (D) from the speech input;
determining a harmonic noise weighting coefficient ε p based on the pitch period;
determining a perceptual noise weighting function W H (z) based on the harmonic noise weighting coefficient; and
transmitting a coded bit stream representing the speech input based on the perceptual noise weighting function.
2. The method of claim 1 wherein ε p is a decreasing function of D.
3. The method of claim 2 wherein:
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max
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where
ε max is a maximum allowable value of the harmonic noise weighting coefficient;
ε min is a minimum allowable value of the harmonic noise weighting coefficient;
D max is a maximum pitch period above which harmonic noise weighting coefficient is set to ε min ; and
Δ is the slope for the harmonic noise weighting coefficient.
4. A method for performing harmonic noise weighting in a digital speech coder, the method comprising the steps of:
receiving a speech input s(n);
determining a closed-loop pitch delay (τ) from the speech input;
determining a harmonic noise weighting coefficient ε p based on the closed-loop pitch delay;
determining a perceptual noise weighting function W H (z) based on the harmonic noise weighting coefficient; and
transmitting a coded bit stream representing the speech input based on the perceptual noise weighting function.
5. The method of claim 4 wherein ε p is a decreasing function of τ
6. The method of claim 5 wherein:
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p
(
τ
)
=
{
ɛ
min
,
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≥
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max
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min
+
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max
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Otherwise
where,
ε max is a maximum allowable value of the harmonic noise weighting coefficient;
ε min is a minimum allowable value of the harmonic noise weighting coefficient;
τ max is a maximum closed-loop pitch delay above which harmonic noise weighting coefficient is set to ε min ; and
Δ is the slope for the harmonic noise weighting coefficient.
7. An apparatus comprising:
pitch analysis circuitry having speech (s(n)) as an input and outputting a pitch period (D) based on the speech;
a harmonic noise coefficient generator receiving D from the pitch analysis circuitry and outputting a harmonic noise weighting coefficient (ε p ) based on (D); and
a perceptual error weighting filter receiving ε p from the harmonic noise coefficient generator and utilizing ε p to generate a weighted error signal e(n), wherein e(n)is based on a difference between s(n) and an estimate of s(n).
8. An apparatus comprising:
a harmonic noise coefficient generator having a closed-loop pitch delay (τ) as an input and outputting a harmonic noise weighting coefficient (ε p ) based on τ, and
a perceptual error weighting filter receiving ε p from the harmonic noise coefficient generator and utilizing ε p to generate a weighted error signal e(n),
wherein e(n) in based on a difference between s(n) and an estimate of s(n).