Methods and apparatus for post-processing of speech signals
A method for post-processing of speech signals includes using a pitch correction filter, a pitch weight parameter adjustor, and a first pitch enhancement filter to process the input signal into a first output signal; summing both the input signal and the first output signal as a second output signal; and using a second pitch enhancement filter to process the second output signal. Furthermore, another method for post-processing of speech signals includes using a second pitch enhancement filter to process the input signal into a second output signal; using a pitch correction filter, a pitch weight parameter adjustor, and a first pitch enhancement filter to process the second output signal into a first output signal; and summing both the second output signal and the first output signal as a final output signal. The two methods can simultaneously realize pitch emphasis and enhancement with low computation complexity.
1. A method for post-processing of an input signal, comprising:
using a pitch correction filter, a pitch weight parameter adjustor, and a first pitch enhancement filter to process the input signal into a first output signal;
summing both the input signal and the first output signal as a second output signal; and
using a second pitch enhancement filter to process the second output signal.
2. The method of claim 1 , wherein the pitch correction filter is configured to modify gains of individual harmonics in frequency domain, and wherein the pitch correction filter includes an all-pass filter having a transfer function of H 0 (z)=1 or a comb filter having a transfer function of H 0 (z)=1+az −T , where T and a are a pitch period and a total gain modification factor, respectively.
3. The method of claim 1 , wherein the pitch weight parameter is a fixed empirical parameter.
4. The method of claim 1 , wherein both the first and second pitch enhancement filters include a long-term filter having a transfer function of: H LT (z)=λ+ηz −T .
5. The method of claim 4 , wherein the long-term filter has a transfer function of H PE (z)=(1−α)+αz −T , where α is a parameter related to pitch amplification, and T is a pitch parameter corresponding to a signal of a current frame.
6. The method of claim 1 , wherein the pitch correction filter, the pitch weight parameter adjustor, and the first pitch enhancement filter are arranged in a random order.
7. The method of claim 1 , wherein the input signal includes either a decoded speech signal or a decoded excitation signal.
8. A method for post-processing of an input signal, comprising:
using a second pitch enhancement filter to process the input signal into a second output signal;
using a pitch correction filter, a pitch weight parameter adjustor, and a first pitch enhancement filter to process the second output signal into a first output signal; and
summing both the second output signal and the first output signal as a final output signal.
9. The method of claim 8 , wherein the pitch correction filter is configured to modify gains of individual harmonics in frequency domain, and wherein the pitch correction filter includes an all-pass filter having a transfer function of H 0 (z)=1 or a comb filter having a transfer function of H 0 (z)=1+az −T , where T and a are a pitch period and a total gain modification factor, respectively.
10. The method of claim 8 , wherein the pitch weight parameter is a fixed empirical parameter.
11. The method of claim 8 , wherein both the first and second pitch enhancement filters include a long-term filter having a transfer function of: H LT (z)=λ+ηz −T .
12. The method of claim 11 , wherein the long-term filter has a transfer function of H PE (z)=(1−α)+αz −T , where α is a parameter related to pitch amplification, and T is a pitch parameter corresponding to a signal of a current frame.
13. The method of claim 8 , wherein the pitch correction filter, the pitch weight parameter adjustor, and the first pitch enhancement filter are arranged in a random order.
14. The method of claim 8 , wherein the input signal includes either a decoded speech signal or a decoded excitation signal.
15. An apparatus for post-processing of an input signal, comprising:
a pitch correction filter, a pitch weight parameter adjustor, and a first pitch enhancement filter coupled to one another and configured to process the input signal into a first output signal;
a summing device configured to sum both the input signal and the first output signal as a second output signal; and
a second pitch enhancement filter coupled to the summing device and configured to process the second output signal.
16. The apparatus of claim 15 , wherein the pitch correction filter is configured to modify gains of individual harmonics in frequency domain, and wherein the pitch correction filter includes an all-pass filter having a transfer function as H 0 (z)=1 or a comb filter having a transfer function as H 0 (z)=1+az −T , where T and a are a pitch period and a total gain modification factor, respectively.
17. The apparatus of claim 15 , wherein the pitch weight parameter is a fixed empirical parameter.
18. The apparatus of claim 15 , wherein both the first and second pitch enhancement filters include a long-term filter having a transfer function of H LT (z)=λ+ηz −T .
19. The apparatus of claim 18 , wherein the long-term filter has a transfer function of H PE (z)=(1−α)+αz −T , where α is a parameter related to pitch amplification, and T is a pitch parameter corresponding to a signal of a current frame.
20. The apparatus of claim 15 , wherein the pitch correction filter, the pitch weight parameter adjustor, and the first pitch enhancement filter are arranged in a random order.