Gain shape estimation for improved tracking of high-band temporal characteristics

• US 9,620,134 B2
• Filed: 10/07/2014
• Issued: 04/11/2017
• Est. Priority Date: 10/10/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chebiyyam, Venkata Subrahmanyam Chandra Sekhar, Atti, Venkatraman S.
• Primary Examiner(s): Yang, Qian
• Application Number:
  US14/508,486
• Publication Number:
  US 20150106102A1
• Time in Patent Office: 917 Days
• CPC Class Codes: G10L 13/00 Speech synthesis; Text to speech systems
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

A method includes determining, at a speech encoder, first gain shape parameters based on a harmonically extended signal and/or based on a high-band residual signal associated with a high-band portion of an audio signal. The method also includes determining second gain shape parameters based on a synthesized high-band signal and based on the high-band portion of the audio signal. The method further includes inserting the first gain parameters and the second gain shape parameters into an encoded version of the audio signal to enable gain adjustment during reproduction of the audio signal from the encoded version of the audio signal.

Claims

1. A method comprising:

performing a first determination, at a speech encoder, of first gain shape parameters based at least in part on energy levels of a first plurality of sub-frames of a harmonically extended signal, based at least in part on energy levels of a second plurality of sub-frames of a high-band residual signal associated with a high-band portion of an audio signal, or any combination thereof;

generating a high-band excitation signal based at least in part on the first gain shape parameters;

generating a synthesized high-band signal based on the high-band excitation signal;

performing a second determination of second gain shape parameters based on the synthesized high-band signal and based on the high-band portion of the audio signal; and

inserting the first gain shape parameters and the second gain shape parameters into an encoded version of the audio signal.

2. The method of claim 1, wherein the first determination is performed at a first gain shape estimator stage, wherein the second determination is performed at a second gain shape estimator stage, and wherein the second gain shape estimator stage differs from the first gain shape estimator stage.

3. The method of claim 1, wherein the first determination, the second determination, and the inserting are performed at a device that comprises a mobile communication device.

4. The method of claim 1, wherein the first gain shape parameters are determined in a linear prediction residual domain, wherein the second gain shape parameters are determined in a linear prediction synthesis domain, and wherein the harmonically extended signal is generated from a low-band portion of the audio signal through non-linear harmonic extension.

5. The method of claim 1, further comprising:

adjusting the harmonically extended signal based on the first gain shape parameters to generate a modified harmonically extended signal;

wherein generating the high-band excitation signal is at least partially based on the modified harmonically extended signal;

performing a linear prediction synthesis operation on the high-band excitation signal to generate the synthesized high-band signal; and

adjusting the synthesized high-band signal based on the second gain shape parameters.

6. The method of claim 5, wherein the high-band excitation signal is generated based on the modified harmonically extended signal and a modulated noise signal.

7. The method of claim 1, further comprising:

sampling a low-band frame of the harmonically extended signal to generate the first plurality of sub-frames;

or

sampling a corresponding high-band frame of the high-band residual signal to generate the second plurality of sub-frames.

8. The method of claim 7, wherein adjusting the harmonically extended signal comprises scaling a particular sub-frame of the first plurality of sub-frames to approximate an energy level of a corresponding sub-frame of the second plurality of sub-frames.

9. The method of claim 7, wherein the second plurality of sub-frames includes a first number of sub-frames in response to a determination that the high-band frame is a voiced frame, and wherein the second plurality of sub-frames includes a second number of sub-frames that is less than the first number of sub-frames in response to a determination that the high-band frame is not a voiced frame.

10. The method of claim 7, wherein the first plurality of sub-frames and the second plurality of sub-frames include the same number of sub-frames for both a voiced frame and an unvoiced frame, wherein the first plurality of sub-frames and the second plurality of sub-frames include four sub-frames if a low band core sample rate is 12.8 kilohertz (kHz), and wherein the first plurality of sub-frames and the second plurality of sub-frames include five sub-frames if the low band core sample rate is 16 kHz.

11. The method of claim 1, wherein the first determination, the second determination, and the inserting are performed at a device that comprises a fixed location data unit.

12. An apparatus comprising:

a first gain shape estimator configured to determine first gain shape parameters at least in part based on energy levels of a first plurality of sub-frames of a harmonically extended signal, based at least in part on energy levels of a second plurality of sub-frames of a high-band residual signal associated with a high-band portion of an audio signal, or any combination thereof;

a high-band excitation generator configured to generate a high-band excitation signal based at least in part on the first gain shape parameters;

a linear prediction synthesizer configured to perform a linear prediction synthesis operation on the high-band excitation signal to generate a synthesized high-band signal;

a second gain shape estimator configured to determine second gain shape parameters based on the synthesized high-band signal and based on the high-band portion of the audio signal; and

circuitry configured to insert the first gain shape parameters and the second gain shape parameters into an encoded version of the audio signal.

13. The apparatus of claim 12, wherein the first gain shape parameters are determined in a linear prediction residual domain, wherein the circuitry includes a multiplexer, and wherein the harmonically extended signal is generated from a low-band portion of the audio signal through non-linear harmonic extension.

14. The apparatus of claim 12, further comprising:

an antenna; and

a receiver coupled to the antenna and configured to receive the audio signal.

15. The apparatus of claim 14, further comprising a processor coupled to the first gain shape estimator, the second gain shape estimator, the circuitry, and the receiver, wherein the processor is integrated into a mobile communication device.

16. The apparatus of claim 14, further comprising a processor coupled to the first gain shape estimator, the second gain shape estimator, the circuitry, and the receiver, wherein the processor is integrated into a fixed location data unit.

17. The apparatus of claim 12, further comprising a first gain shape adjuster configured to adjust the harmonically extended signal based on the first gain shape parameters to generate a modified harmonically extended signal, wherein the first gain shape estimator is further configured to:

sample a low-band frame of the harmonically extended signal to generate the first plurality of sub-frames;

or

sample a corresponding high-band frame of the high-band residual signal to generate the second plurality of sub-frames.

18. The apparatus of claim 17, wherein the first plurality of sub-frames includes a first number of sub-frames in response to a determination that the high-band frame is a voiced frame, and wherein the first plurality of sub-frames includes a second number of sub-frames that is less than the first number of sub-frames in response to a determination that the high-band frame is not a voiced frame.

19. The apparatus of claim 17, wherein the first plurality of sub-frames includes sixteen sub-frames in response to a determination that the high-band frame is a voiced frame.

20. The apparatus of claim 17, wherein the high-band excitation generator is configured to generate the high-band excitation signal based on the modified harmonically extended signal and a modulated noise signal.

21. The apparatus of claim. 12, further comprising:

a first gain shape adjuster configured to adjust the harmonically extended signal based on a low-band frame of the harmonically extended signal; and

a second gain shape adjuster configured to adjust the synthesized high-band signal based on the second gain shape parameters.

22. A method comprising:

receiving, at a speech decoder, an encoded audio signal from a speech encoder, wherein the encoded audio signal comprises;

first gain shape parameters based on a first determination, the first determination based at least in part on energy levels of a first plurality of sub-frames of a first harmonically extended signal generated at the speech encoder, based at least in part on energy levels of a second plurality of sub-frames of a high-band residual signal generated at the speech encoder, or any combination thereof; and

second gain shape parameters based on a second determination, the second determination based on a first synthesized high-band signal generated at the speech encoder and based on a high-band portion of an audio signal, wherein the synthesized high-band signal is based on a first high-band excitation signal that is based at least in part on the first gain shape parameters; and

reproducing the audio signal from the encoded audio signal based on the first gain shape parameters and based on the second gain shape parameters.

23. The method of claim 22, wherein reproducing the audio signal at the speech decoder comprises:

generating a second harmonically extended signal based on non-linearly extending a low-band excitation of the encoded audio signal;

adjusting the second harmonically extended signal based on the first gain shape parameters to obtain a modified second harmonically extended signal;

generating a second high-band excitation signal based on the modified second harmonically extended signal;

performing a linear prediction synthesis operation on the second high-band excitation signal to generate a second synthesized high-band signal; and

adjusting the second synthesized high-band signal based on the second gain shape parameters.

24. The method of claim 22, wherein the receiving and the reproducing are performed at a device that comprises a mobile communication device.

25. The method of claim 22, wherein the receiving and the reproducing are performed at a device that comprises a fixed location data unit.

26. A system including a speech decoder, the speech decoder configured to:

receive an encoded audio signal from a speech encoder, wherein the encoded audio signal comprises;

first gain shape parameters based on a first determination, the first determination based at least in part on energy levels of a first plurality of sub-frames of a first harmonically extended signal generated at the speech encoder, based at least in part on energy levels of a second plurality of sub-frames of a high-band residual signal generated at the speech encoder, or any combination thereof; and

second gain shape parameters based on a second determination, the second determination based on a first synthesized high-band signal generated at the speech encoder and based on a high-band portion of an audio signal, wherein the first synthesized high-band signal is based on a first high-band excitation signal that is based at least in part on the first gain shape parameters; and

reproduce the audio signal from the encoded audio signal based on the first gain shape parameters and based on the second gain shape parameters.

27. The system of claim 26, further comprising:

an antenna; and

a receiver coupled to the antenna and configured to receive the encoded audio signal.

28. The system of claim 27, further comprising a processor coupled to the receiver, wherein the processor and the receiver are integrated into a mobile communication device.

29. The system of claim 27, further comprising a processor coupled to the receiver, wherein the processor and the receiver are integrated into a fixed location data unit.

30. The system of claim 26, comprising:

a non-linear excitation generator configured to generate a second harmonically extended signal based on a low-band excitation of the encoded audio signal;

a first gain shape adjuster configured to adjust the second harmonically extended signal based on the first gain shape parameters to obtain a second modified harmonically extended signal; and

a high-band excitation generator configured to generate a second high-band excitation signal based on the modified second harmonically extended signal.