Method and system for comfort noise generation in speech communication

• US 6,662,155 B2
• Filed: 10/02/2001
• Issued: 12/09/2003
• Est. Priority Date: 11/27/2000
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Vainio, Janne, Mikkola, Hannu, Rotola-Pukkila, Jani
• Primary Examiner(s): Chawan, Vijay
• Assistant Examiner(s): Harper, V. Paul
• Application Number:
  US09/970,091
• Publication Number:
  US 20020103643A1
• Time in Patent Office: 798 Days
• Field of Search: 714/39, 714/758, 704/277, 704/236, 704/233, 704/230, 704/229, 704/228, 704/226, 704/225, 704/220, 704/219, 704/216, 704/210, 704/205, 704/200.1, 379/406.3
• US Class Current: 704/228
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10

Abstract

A method and system for providing comfort noise in the non-speech periods in speech communication. The comfort noise is generated based on whether the background noise in the speech input is stationary or non-stationary. If the background noise is non-stationary, a random component is inserted in the comfort noise using a dithering process. If the background noise is stationary, the dithering process is not used.

Claims

1. A method of generating comfort noise in speech communication having speech periods and non-speech periods, wherein signals indicative of a speech input are provided in frames from a transmit side to a receive side for carrying out said speech communication, and the speech input has a speech component and a non-speech component, the non-speech component classifiable as stationary or non-stationary, said method comprising the steps of:

determining whether the non-speech component is stationary or non-stationary;

providing in the transmit side a further signal having a first value indicating that the non-speech component is stationary or a second value indicative of the non-speech component is non-stationary; and

providing in the receive side the comfort noise in the non-speech periods, responsive to said further signal received from the transmit side, in a manner based on whether the further signal has the first value or the second value.

2. The method of claim 1, wherein the non-speech component is a background noise in the transmit side.

3. The method of claim 1, wherein the comfort noise is provided with a random component if the further signal has the second value.

4. The method of claim 1, wherein the signals include a spectral parameter vector and an energy level estimated from a spectrum of the non-speech component, and the comfort noise is generated based on the spectral parameter vector and the energy level.

5. The method of claim 4, wherein if the further signal has the second value, a random value is inserted into elements of the spectral parameter vector prior to the comfort noise being provided.

6. The method of claim 5, wherein the random value is bounded by −

L and −

L, wherein L is a predetermined value.

9. The method of claim 4, wherein if the further signal has the second value, a first set of random values is inserted into elements of the spectral parameter vector, and a second random value is inserted into the energy level prior to the comfort noise being provided.

11. The method of claim 4, farther comprising the step of computing changes in the energy level between frames if the further signal has the first value, and wherein if the changes in the energy level exceed a predetermined value, the further signal is changed to have the second value and a random value vector is inserted into the spectral parameter vector prior to the comfort noise being provided.

12. The method of claim 4, further comprising the step of computing changes in the energy level between frames if the further signal has the first value, and wherein if the changes in the energy level exceed a predetermined value, the further signal is changed to have the second value and a random value vector is inserted into the spectral parameter vector and the energy level prior to the comfort noise being provided.

13. The method of claim 4, wherein the further signal includes a flag sent from the transmit side to the receive side for indicating whether the non-speech component is stationary or non-stationary, wherein the flag is set when the further signal has the first value and the flag is not set when the further signal has the second value.

14. The method of claim 13, wherein when the flag is not set, a random value is inserted into the spectral parameter vector prior to the comfort noise being provided.

15. The method of claim 13, further comprising the steps of:

computing changes in the energy level between frames if the further signal has the first value;

determining whether the changes in the energy level exceed a predetermined value; and

resetting the flag if the changes exceed the predetermined value.

16. The method of claim 15, wherein when the flag is not set, a random value is inserted into the spectral parameter vector prior to the comfort noise being provided.

17. The method of claim 1, wherein the signals include a plurality of spectral parameter vectors representing the non-speech components, and the determining step is carried out based on spectral distances among the spectral parameter vectors.

18. The method of claim 17, wherein the spectral distances are summed over an averaging period for providing a summed value, and wherein the non-speech component is classified as stationary if the summed value is smaller than a predetermined value and the non-speech component is classified as non-stationary if the summed value is larger or equal to the predetermined value.

19. The method of claim 17, wherein the spectral parameter vectors are linear spectral frequency (LSF) vectors.

20. The method of claim 17, wherein the spectral parameter vectors are immittance spectral frequency (ISF) vectors.

21. The method of claim 1, wherein the further signal is a binary flag, the first value is 1 and the second value is 0.

22. The method of claim 1, wherein the further signal is a binary flag, the first value is 0 and the second value is 1.

7. A method of generating comfort noise in speech communication having speech periods and non-speech periods, wherein signals indicative of a speech input are provided in frames from a transmit side to a receive side for carrying out said speech communication, and the speech input has a speech component and a non-speech component, the non-speech component classifiable as stationary or non-stationary, said method comprising the steps of:

determining whether the non-speech component is stationary or non-stationary;

providing in the transmit side a further signal having a first value indicating that the non-speech component is stationary or a second value indicating that the non-speech component is non-stationary; and

providing in the receive side the comfort noise in the non-speech periods, responsive to said further signal received from the transmit side, in a manner based on whether the further signal has the first value or the second value, wherein the signals include a spectral parameter vector and an energy level estimated from a spectrum of the non-speech component, and the comfort noise is generated based on the spectral parameter vector and the energy level, and wherein if the further signal has the second value, a random value is inserted into elements of the spectral parameter vector prior to the comfort noise being provided, and the random value is bounded by −

L and −

L. wherein L is a predetermined value, and wherein the predetermined value is substantially equal to 100+0.8i Hz.

8. A method of generating comfort noise in speech communication having speech periods and non-speech periods, wherein signals indicative of a speech input are provided in frames from a transmit side to a receive side for carrying out said speech communication, and the speech input has a speech component and a non-speech component. the non-speech component classifiable as stationary or non-stationary, said method comprising the steps of:

determining whether the non-speech component is stationary or non-stationary;

providing in the transmit side a further signal having a first value indicating that the non-speech component is stationary or a second value indicating that the non-speech component is non-stationary; and

providing in the receive side the comfort noise in the non-speech periods, responsive to said further signal received from the transmit side, in a manner based on whether the further signal has the first value or the second value, wherein the signals include a spectral parameter vector and an energy level estimated from a spectrum of the non-speech component, and the comfort noise is generated based on the spectral parameter vector and the energy level and if the further signal has the second value, a random value is inserted into elements of the spectral parameter vector prior to the comfort noise being provided, and wherein the random value is bounded by −

L and L, wherein L is a value increasing with the elements representing higher frequencies.

10. A method of generating comfort noise in speech communication having speech periods and non-speech periods, wherein signals indicative of a speech input are provided in frames from a transmit side to a receive side for carrying out said speech communication, and the speech input has a speech component and a non-speech component, the non-speech component classifiable as stationary or non-stationary, said method comprising the steps of:

determining whether the non-speech component is stationary or non-stationary;

providing in the transmit side a further signal having a first value indicating that the non-speech component is stationary or a second value indicating that the non-speech component is non-stationary; and

providing in the receive side the comfort noise in the non-speech periods, responsive to said further signal received from the transmit side, in a manner based on whether the further signal has the first value or the second value, wherein the signals include a spectral parameter vector and an energy level estimated from a spectrum of the non-speech component, and the comfort noise is generated based on the spectral parameter vector and the energy level, and if the further signal has the second value, a first set of random values is inserted into elements of the spectral parameter vector, and a second random value is inserted into the energy level prior to the comfort noise being provided, and wherein the second random value is bounded by −

75 and 75.

23. A system for generating comfort noise in speech communication in a communication network having a transmit side for providing speech related parameters indicative of a speech input, and a receive side for reconstructing the speech input based on the speech related parameters, wherein the speech communication has speech periods and non-speech periods and the speech input has a speech component and a non-speech component, the non-speech component classifiable as stationary and non-stationary, and wherein the comfort noise is provided in the non-speech periods, said system comprising:

means, located on the transmit side, for determining whether the non-speech component is stationary or non-stationary for providing a signal having a first value indicative of the non-speech component being stationary or a second value indicative of the non-speech component being non-stationary; and

means, located on the receive side, responsive to the signal, for inserting a random component in the comfort noise only if the signal has the second value.

24. A speech coder for use in speech communication having an encoder for providing speech parameters indicative of a speech input, and a decoder, responsive to the provided speech parameters, for reconstructing the speech input based on the speech parameters, wherein the speech communication has speech periods and non-speech periods and the speech input has a speech component and a non-speech component, the non-speech component classifiable as stationary or non-stationary, and wherein

the encoder comprises a spectral analysis module, responsive to the speech input, for providing a spectral parameter vector and energy parameter indicative of the non-speech component of the speech input, and

the decoder comprises means for providing a comfort noise in the non-speech periods to replace the non-speech component based on the spectral parameter vector and energy parameter, said speech coder comprising:

a noise detector module, located in the encoder, responsive to the spectral parameter vector and energy parameter, for determining whether the non-speech component is stationary or non-stationary and providing a signal having a first value indicative of the non-speech component being stationary and a second value indicative of the non-speech component being non-stationary; and

a dithering module, located in the decoder, responsive to the signal, for inserting a random component in elements of the spectral parameter vector and energy parameter for modifying the comfort noise only if the non-speech component is non-stationary.

25. A method of providing comfort noise in speech communication having speech periods and non-speech periods, wherein signals indicative of a speech input are provided from a transmit side to a receive side for carrying out said speech communication, and wherein the speech input has a speech component and a non-speech component, the non-speech component classifiable as stationary or non-stationary, and the comfort noise is provided in the non-speech periods, said method comprising the steps of:

determining in the transmit side whether the non-speech component is stationary or non-stationary;

providing in transmit side a further signal indicative of said determining; and

modifying the comfort noise in the receive side, responsive to the further signal received from the transmit side, if the non-speech component is non-stationary based on the further signal.