Noise-Feedback for Spectral Envelope Quantization

• US 20100063810A1
• Filed: 09/04/2009
• Published: 03/11/2010
• 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
• Granted Patent: US 8,407,046 B2
• Time in Patent Office: Days
• 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; 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 first 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 a 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 a 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. A system for transmitting an input audio signal, the system comprising:

a transmitter comprising an audio coder, the 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.

20. The system of claim 19, wherein the system is configured to operate over a voice over internet protocol (VOIP) system.

21. The system of claim 19, wherein the system is configured to operate over a cellular telephone network.

22. The system of claim 19, 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.