Noise-feedback for spectral envelope quantization

• US 8,407,046 B2
• Filed: 09/04/2009
• Issued: 03/26/2013
• Est. Priority Date: 09/06/2008
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Gao, Yang
• Primary Examiner(s): Han, Qi
• Application Number:
  US12/554,662
• Publication Number:
  US 20100063810A1
• Time in Patent Office: 1,299 Days
• Field of Search: 704/230, 704/209, 704/205, 704/201, 704/200
• US Class Current: 704/230
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components

Abstract

A method of transmitting an input audio signal is disclosed. A current spectral magnitude of the input audio signal is quantized. A quantization error of a previous spectral magnitude is fed back to influence quantization of the current spectral magnitude. The feeding back includes adaptively modifying a quantization criterion to form a modified quantization criterion. A current quantization error is minimized by using the modified quantization criterion. A quantized spectral envelope is formed based on the minimizing and the quantized spectral envelope is transmitted.

Claims

1. A method of transmitting an input audio signal, the method comprising:

quantizing a current spectral magnitude of the input audio signal;

feeding back a quantization error of a previous spectral magnitude to influence quantization of the current spectral magnitude, wherein feeding back comprises adaptively modifying a quantization criterion to form a modified quantization criterion;

minimizing a current quantization error by using the modified quantization criterion;

forming a quantized spectral envelope based on the minimizing, wherein the steps of quantizing, feeding back, minimizing and forming are performed using a hardware-based audio coder; and

transmitting the quantized spectral envelope.

2. The method of claim 1, wherein minimizing further comprises using a noise-feedback solution.

3. The method of claim 1, wherein quantizing the spectral magnitudes comprises performing a scalar quantization.

4. The method of claim 3, wherein the scalar quantization comprises a direct scalar quantization.

5. The method of claim 3, wherein the scalar quantization comprises an indirect scalar quantization.

6. The method of claim 5, wherein:

the indirect scalar quantization comprises differential coding or Huffman coding; and

the quantization is performed in a log domain or a linear domain.

7. The method of claim 1, further comprising:

setting an initial quantization error of the current spectral magnitude to be Er(i)=M_q2(i)−

M(i), where M(i) is a current reference magnitude and M_q2(i) is a current quantized magnitude; and

setting an initial quantization error of a previous magnitude as Er(i−

1)=M_q2(i−

1)−

M(i−

1), where M(i−

1) is a previous reference magnitude and M_q2(i−

1) is a previous quantized magnitude.

8. The method of claim 7, further comprising setting the current reference magnitude to be M(i)=maxVal−

log Gains(i), where maxVal is a maximum spectral magnitude and log Gains(i) is a spectral magnitude in a log domain.

9. The method of claim 7, wherein quantizing the current spectral magnitude comprises setting M_q2(i)=Index(i)·

Step, where Index(i) is a quantization index for each magnitude and Step is defined as Step=maxVal/4, where if Step>

1.2, Step=1.2, and maxVal is a maximum spectral magnitude.

10. The method of claim 1, wherein minimizing the current quantization error comprises minimizing the expression MIN{|M_q2(0)−

M(0)|}, where M(0) is a first reference magnitude and M_q2(0) is said first quantized magnitude.

11. The method of claim 1, wherein minimizing the current quantization error comprises minimizing the expression MIN{|M_q2(i)−

M(i)−

α

·

Er(i−

1)|}, where M(i) is a current reference magnitude, M_q2(i) is said current quantized magnitude, Er(i−

1) is a quantization error of a previous magnitude, and α

is a constant (0<

α

<

1) to control how much error noise is fed back from the quantization error Er(i−

1) of the previous spectral magnitude.

12. The method of claim 11, wherein an overall energy of the quantized spectral envelope is not adjusted or normalized if α

<

=0.5.

13. The method of claim 11, wherein α

is about 0.5.

14. The method of claim 1, further comprising normalizing an average magnitude of a quantized spectral envelope of the input audio signal in a time domain or a frequency domain.

15. The method of claim 1, further comprising:

receiving the quantized spectral envelope; and

forming an output audio signal based on the quantized spectral envelope.

16. The method of claim 15, further comprising driving a loudspeaker with the output audio signal.

17. The method of claim 1, wherein transmitting comprises transmitting over a voice over internet protocol (VOIP) network.

18. The method of claim 1, wherein transmitting comprises transmitting over a cellular telephone network.

19. The method of claim 1, wherein using the hardware-based audio coder comprises performing the steps of quantizing, feeding back, minimizing and forming using a processor.

20. The method of claim 1, wherein using the hardware-based audio coder comprises performing the steps of quantizing, feeding back, minimizing and forming using dedicated hardware.

21. A system for transmitting an input audio signal, the system comprising:

a transmitter comprising a hardware-based audio coder, the hardware-based audio coder configured to

quantize a current spectral magnitude of the input audio signal;

feed back a quantization error of a previous spectral magnitude to influence quantization of the current spectral magnitude, wherein feeding back comprises adaptively modifying a quantization criterion to form a modified quantization criterion;

minimize a current quantization error by using the modified quantization criterion; and

form a quantized spectral envelope based on minimizing the current quantization error.

22. The system of claim 21, wherein the system is configured to operate over a voice over internet protocol (VOIP) system.

23. The system of claim 21, wherein the system is configured to operate over a cellular telephone network.

24. The system of claim 21, further comprising a receiver, the receiver comprising an audio decoder configured to receive the quantized spectral envelope and produce an output audio signal based on the quantized spectral envelope.

25. The system of claim 21, wherein the hardware-based audio coder comprises a processor.

26. The system of claim 21, wherein the hardware-based audio coder comprises dedicated hardware.