High band excitation signal generation

Patent metadata

Field	Value
Publication number	US-10297263-B2
Application number	US-201715611706-A
Country	US
Kind code	B2
Filing date	Jun 1, 2017
Priority date	Apr 30, 2014
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A method includes extracting a voicing classification parameter of an audio signal and determining a filter coefficient of a low pass filter based on the voicing classification parameter. The method also includes filtering a low-band portion of the audio signal to generate a low-band audio signal and controlling an amplitude of a temporal envelope of the low-band audio signal based on the filter coefficient. The method also includes modulating a white noise signal based on the amplitude of the temporal envelope to generate a modulated white noise signal and scaling the modulated white noise signal based on a noise gain to generate a scaled modulated white noise signal. The method also includes mixing a scaled version of the low-band audio signal with the scaled modulated white noise signal to generate a high-band excitation signal that is used to generate a decoded version of the audio signal.

First claim

What is claimed is:

1. A method comprising:
extracting, at a decoder, a voicing classification parameter of an audio signal;
determining a filter coefficient of a low pass filter based on the voicing classification parameter, the filter coefficient having:
a first value if the voicing classification parameter indicates that the audio signal is a strongly voiced signal;
a second value if the voicing classification parameter indicates that the audio signal is a weakly voiced signal, the second value lower than the first value;
a third value if the voicing classification parameter indicates that the audio signal is a weakly unvoiced signal, the third value lower than the second value; or
a fourth value if the voicing classification parameter indicates that the audio signal is a strongly unvoiced signal, the fourth value lower than the third value;

filtering a low-band portion of the audio signal to generate a low-band audio signal;
controlling an amplitude of a temporal envelope of the low-band audio signal based on the filter coefficient of the low pass filter;
modulating a white noise signal based on the amplitude of the temporal envelope to generate a modulated white noise signal;
scaling the modulated white noise signal based on a noise gain to generate a scaled modulated white noise signal;
mixing a scaled version of the low-band audio signal with the scaled modulated white noise signal to generate a high-band excitation signal;
generating a decoded version of the audio signal based on the high-band excitation signal; and
providing the decoded version of the audio signal to a device that includes a speaker.

2. The method of claim 1 , wherein controlling the amplitude of the temporal envelope comprises:
applying the low pass filter to the low-band audio signal to generate a filtered low-band audio signal; and
controlling the amplitude of the temporal envelope to match an amplitude of the filtered low-band audio signal, wherein the amplitude of the filtered low-band audio signal matches an amplitude of the low-band audio signal if the amplitude of the filtered low-band audio signal is less than a cut-off frequency associated with the filter coefficient.

3. The method of claim 1 , wherein the noise gain is based on a ratio of harmonic energy to noise energy in a high-band portion of the audio signal.

4. The method of claim 1 , wherein the low-band audio signal comprises a low-band excitation signal or a harmonically extended low-band excitation signal.

5. The method of claim 1 , further comprising generating a synthesized high-band signal based on the high-band excitation signal.

6. The method of claim 5 , further comprising generating a synthesized low-band signal based on the low-band portion of the audio signal.

7. The method of claim 6 , wherein generating the decoded version of the audio signal includes combining the synthesized high-band signal and the synthesized low-band signal to generate the decoded version of the audio signal.

8. The method of claim 1 , wherein the decoder is integrated into a base station.

9. The method of claim 1 , wherein the decoder is integrated into a mobile device.

10. The method of claim 1 , wherein the low-band audio signal includes fewer than a threshold number of pulses, and wherein mixing the sealed version of the low-band audio signal with the scaled modulated white noise signal to generate the high-band excitation signal reduces or eliminates one or more artifacts in the decoded version of the audio signal associated with the low-band audio signal.

11. An apparatus comprising:
a voicing classifier configured to extract a voicing classification parameter of an audio signal;
an envelope adjuster configured to:
determine a filter coefficient of a low pass filter based on the voicing classification parameter, the filter coefficient having:
a first value if the voicing classification parameter indicates that the audio signal is a strongly voiced signal;
a second value if the voicing classification parameter indicates that the audio signal is a weakly voiced signal, the second value lower than the first value;
a third value if the voicing classification parameter indicates that the audio signal is a weakly unvoiced signal, the third value lower than the second value; or
a fourth value if the voicing classification parameter indicates that the audio signal is a strongly unvoiced signal, the fourth value lower than the third value; and

control an amplitude of a temporal envelope of a low-band audio signal based on the filter coefficient of the low pass filter, wherein a low-band portion of the audio signal is filtered to generate the low-band audio signal;

a modulator configured to modulate a white noise signal based on the amplitude of the temporal envelope to generate a modulated white noise signal;
a multiplier configured to scale the modulated white noise signal based on a noise gain to generate a scaled modulated white noise signal;
an adder configured to mix a scaled version of the low-band audio signal with the scaled modulated white noise signal to generate a high-band excitation signal; and
circuitry configured to generate a decoded version of the audio signal based on the high-band excitation signal and further configured to provide the decoded version of the audio signal to a device that includes a speaker.

12. The apparatus of claim 11 , wherein the envelope adjuster is further configured to:
apply the low pass filter to the low-band audio signal to generate a filtered low-band audio signal; and
control the amplitude of the temporal envelope to match an amplitude of the filtered low-band audio signal, wherein the amplitude of the filtered low-band audio signal matches an amplitude of the low-band audio signal if the amplitude of the filtered low-band audio signal is less than a cut-off frequency associated with the filter coefficient.

13. The apparatus of claim 11 , wherein the noise gain is based on a ratio of harmonic energy to noise energy in a high-band portion of the audio signal.

14. The apparatus of claim 11 , wherein the low-band audio signal comprises a low-band excitation signal or a harmonically extended low-band excitation signal.

15. The apparatus of claim 11 , further comprising a low-band synthesizer configured to generate a synthesized high-band signal based on the high-band excitation signal.

16. The apparatus of claim 15 , further comprising a high-band synthesizer configured to generate a synthesized low-band signal based on the low-band portion of the audio signal.

17. The apparatus of claim 16 , wherein the circuitry includes a multiplexer configured to combine the synthesized high-band signal and the synthesized low-band signal to generate the decoded version of the audio signal.

18. The apparatus of claim 11 , wherein the voicing classifier, the envelope adjuster, the modulator, the multiplier, and the adder are integrated into a base station.

19. The apparatus of claim 11 , wherein the voicing classifier, the envelope adjuster, the modulator, the multiplier, and the adder are integrated into a mobile device.

20. A non-transitory computer-readable medium comprising instructions that, when executed by a processor within a decoder, cause the processor to perform operations comprising:
extracting a voicing classification parameter of an audio signal;
determining a filter coefficient of a low pass filter based on the voicing classification parameter, the filter coefficient having:
a first value if the voicing class

Assignees

• Qualcomm Inc

Inventors

• Ramadas Pravin Kumar
• Sinder Daniel J
• Villette Stephane Pierre
• Rajendran Vivek

Classifications

• G10L19/08 Primary

  Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters · CPC title

• G10L19/24 Primary

  Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding · CPC title

• G10L21/0208

  Noise filtering · CPC title