Variable Bit Rate LPC Filter Quantizing and Inverse Quantizing Device and Method

• US 20100023325A1
• Filed: 07/10/2009
• Published: 01/28/2010
• Est. Priority Date: 07/10/2008
• Status: Active Grant

• Current Assignee: VoiceAge Corporation
• Original Assignee: VoiceAge Corporation
• Inventors: BESSETTE, Bruno, Salami, Redwan, Gournay, Philippe
• Granted Patent: US 9,245,532 B2
• Time in Patent Office: Days
• US Class Current: 704/219
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: H03M 7/3082 Vector coding for television signals, see H04N19/94

Abstract

A device and a method for quantizing a LPC filter in the form of an input vector in a quantization domain, comprises a calculator of a first-stage approximation of the input vector, a subtractor of the first-stage approximation from the input vector to produce a residual vector, a calculator of a weighting function from the first-stage approximation, a warper of the residual vector with the weighting function, and a quantizer of the weighted residual vector to supply a quantized weighted residual vector. A device and a method for inverse quantizing of a LPC filter, comprises means for receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain and of a quantized weighted residual version of the vector, a calculator of an inverse weighting function from the first-stage approximation, an inverse quantizer of the quantized weighted residual version of the vector to produce a weighted residual vector, a multiplier of the weighted residual vector by the inverse weighting function to produce a residual vector, and an adder of the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain.

Claims

1. A device for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

means for computing a first-stage approximation of the input vector;

means for subtracting the first-stage approximation from the input vector to produce a residual vector;

means for calculating a weighting function from the first-stage approximation;

means for applying the weighting function to the residual vector; and

means for quantizing the weighted residual vector to supply a quantized weighted residual vector.

2. A device for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

a calculator of a first-stage approximation of the input vector;

a subtractor of the first-stage approximation from the input vector to produce a residual vector;

a calculator of a weighting function from the first-stage approximation;

a warper of the residual vector with the weighting function; and

a quantizer of the weighted residual vector to supply a quantized weighted residual vector.

3. An LPC filter quantizing device according to claim 2, further comprising means for converting the LPC filter in the quantization domain to form the input vector.

4. An LPC filter quantizing device according to claim 2, further comprising a multiplexer of the first-stage approximation of the input vector and the quantized weighted residual vector.

9. An LPC filter quantizing device according to claim 2, wherein the quantization domain is a line spectral frequency domain.

5. A device for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

a calculator of a first-stage approximation of the input vector;

a subtractor of the first-stage approximation from the input vector to produce a residual vector;

a calculator of a weighting function from the first-stage approximation;

a warper of the residual vector with the weighting function; and

a quantizer of the weighted residual vector to supply a quantized weighted residual vector;

wherein the calculator of the first-stage approximation is selected from the group consisting of;

an absolute quantizer of the input vector;

a quantizer of a previous LPC vector;

a quantizer of a future LPC vector; and

an interpolator of previous quantized and/or future quantized LPC vectors;

to give an estimate of the input vector.

6. A device for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

a calculator of a first-stage approximation of the input vector;

a subtractor of the first-stage approximation from the input vector to produce a residual vector;

a calculator of a weighting function from the first-stage approximation;

a warper of the residual vector with the weighting function; and

a quantizer of the weighted residual vector to supply a quantized weighted residual vector;

wherein the calculator of the weighting function calculates different weights, and the warper applies the different weights to components of the residual vector.

7. An LPC filter quantizing device according to claim 6, wherein the calculator of the weighting function uses the first-stage approximation and a scaling factor which is dependent upon a quantization mode to calculate the weights.

8. An LPC filter quantizing device according to claim 7, wherein the scaling factor has a value chosen to attain at least one of a certain average bit rate and a certain average distortion.

10. A device for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

a calculator of a first-stage approximation of the input vector;

a subtractor of the first-stage approximation from the input vector to produce a residual vector;

a calculator of a weighting function from the first-stage approximation;

a warper of the residual vector with the weighting function; and

a quantizer of the weighted residual vector to supply a quantized weighted residual vector;

wherein the quantizer of the weighted residual vector comprises a variable bit rate quantizer.

11. An LPC filter quantizing device according to claim 10, wherein the variable bit rate quantizer comprises an algebraic vector quantizer.

12. A device for inverse quantizing of a LPC filter, comprising:

means for receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

means for calculating an inverse weighting function from the first-stage approximation;

means for inverse quantizing the quantized weighted residual version of the vector to produce a weighted residual vector;

means for applying the inverse weighting function to the weighted residual vector to produce a residual vector; and

means for adding the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain.

13. A device for inverse quantizing of a LPC filter, comprising:

means for receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

a calculator of an inverse weighting function from the first-stage approximation;

an inverse quantizer of the quantized weighted residual version of the vector to produce a weighted residual vector;

a multiplier of the weighted residual vector by the inverse weighting function to produce a residual vector; and

an adder of the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain.

16. An LPC filter inverse quantizing device according to claim 13, wherein the means for receiving coded indices comprises a demultiplexer of the coded indices.

19. An LPC filter inverse quantizing device according to claim 13, wherein the quantization domain is a line spectral frequency domain.

14. A device for inverse quantizing of a LPC filter, comprising:

means for receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

a calculator of an inverse weighting function from the first-stage approximation;

an inverse quantizer of the quantized weighted residual version of the vector to produce a weighted residual vector;

a multiplier of the weighted residual vector by the inverse weighting function to produce a residual vector; and

an adder of the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain;

wherein the received coded indices include an index representative of a quantization mode.

15. An LPC filter inverse quantizing device according to claim 14, wherein the first-stage approximation of the vector representative of the LPC filter in the quantization domain is determined based on the received quantization mode from the group consisting of:

an inverse absolute quantizer;

an inverse quantizer of a previous LPC vector;

an inverse quantizer of a future LPC vector; and

an interpolator of previous inverse quantized and/or future inverse quantized LPC vectors.

17. A device for inverse quantizing of a LPC filter, comprising:

means for receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

a calculator of an inverse weighting function from the first-stage approximation;

an inverse quantizer of the quantized weighted residual version of the vector to produce a weighted residual vector;

a multiplier of the weighted residual vector by the inverse weighting function to produce a residual vector; and

an adder of the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain;

wherein the inverse quantizer of the quantized weighted residual version of the vector comprises a variable bit rate inverse quantizer.

18. An LPC filter inverse quantizing device according to claim 17, wherein the variable bit rate inverse quantizer comprises an inverse algebraic vector quantizer.

20. A method for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

computing a first-stage approximation of the input vector;

subtracting the first-stage approximation from the input vector to produce a residual vector;

calculating a weighting function from the first-stage approximation;

applying the weighting function to the residual vector; and

quantizing the weighted residual vector to supply a quantized weighted residual vector.

21. An LPC filter quantizing method according to claim 20, further comprising converting the LPC filter in the quantization domain to form the input vector.

22. An LPC filter quantizing method according to claim 20, further comprising multiplexing the first-stage approximation of the input vector and the quantized weighted residual vector.

27. An LPC filter quantizing method according to claim 20, wherein the quantization domain is a line spectral frequency domain.

29. An LPC filter quantizing method according to claim 20, wherein using the variable bit rate quantizer comprises using an algebraic vector quantizer.

23. A method for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

computing a first-stage approximation of the input vector;

subtracting the first-stage approximation from the input vector to produce a residual vector;

calculating a weighting function from the first-stage approximation;

applying the weighting function to the residual vector; and

quantizing the weighted residual vector to supply a quantized weighted residual vector;

wherein computing the first-stage approximation is selected from the group consisting of;

absolute quantizing of the input vector;

quantizing of a previous LPC vector;

quantizing of a future LPC vector; and

interpolating of previous quantized and/or future quantized LPC vectors;

to give an estimate of the input vector.

24. A method for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

computing a first-stage approximation of the input vector;

subtracting the first-stage approximation from the input vector to produce a residual vector;

calculating a weighting function from the first-stage approximation;

applying the weighting function to the residual vector; and

quantizing the weighted residual vector to supply a quantized weighted residual vector;

wherein calculating a weighting function comprises calculating different weights, and applying the weighting function comprises applying the different weights to components of the residual vector.

25. An LPC filter quantizing method according to claim 24, wherein calculating different weights comprises using the first-stage approximation and a scaling factor which is dependent upon a quantization mode.

26. An LPC filter quantizing method according to claim 25, wherein the scaling factor has a value chosen to attain at least one of a certain average bit rate and a certain average distortion.

28. A method for quantizing a LPC filter in the form of an input vector in a quantization domain, comprising:

computing a first-stage approximation of the input vector;

subtracting the first-stage approximation from the input vector to produce a residual vector;

calculating a weighting function from the first-stage approximation;

applying the weighting function to the residual vector; and

quantizing the weighted residual vector to supply a quantized weighted residual vector;

wherein quantizing the weighted residual vector comprises using a variable bit rate quantizer.

30. A method for inverse quantizing of a LPC filter, comprising:

receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

calculating an inverse weighting function from the first-stage approximation;

inverse quantizing the quantized weighted residual version of the vector to produce a weighted residual vector;

applying the inverse weighting function to the weighted residual vector to produce a residual vector; and

adding the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain.

33. An LPC filter inverse quantizing method according to claim 30, wherein receiving the coded indices comprises demultiplexing the coded indices.

36. An LPC filter inverse quantizing method according to claim 30, wherein applying the inverse weighting function to the weighted residual vector comprises multiplying the weighted residual vector by the inverse weighting function.

37. An LPC filter inverse quantizing device according to claim 30, wherein the quantization domain is a line spectral frequency domain.

31. A method for inverse quantizing of a LPC filter, comprising:

receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

calculating an inverse weighting function from the first-stage approximation;

inverse quantizing the quantized weighted residual version of the vector to produce a weighted residual vector;

applying the inverse weighting function to the weighted residual vector to produce a residual vector; and

adding the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain;

wherein the received coded indices include an index representative of a quantization mode.

32. An LPC filter inverse quantizing method according to claim 31, wherein the first-stage approximation of the vector representative of the LPC filter in the quantization domain is determined based on the received quantization mode from the group consisting of:

inverse absolute quantizing;

inverse quantizing of a previous LPC vector;

inverse quantizing of a future LPC vector; and

interpolating of previous inverse quantized and/or future inverse quantized LPC vectors.

34. A method for inverse quantizing of a LPC filter, comprising:

receiving coded indices representative of a first-stage approximation of a vector representative of the LPC filter in a quantization domain, and a quantized weighted residual version of the vector;

calculating an inverse weighting function from the first-stage approximation;

inverse quantizing the quantized weighted residual version of the vector to produce a weighted residual vector;

applying the inverse weighting function to the weighted residual vector to produce a residual vector; and

adding the first-stage approximation with the residual vector to produce the vector representative of the LPC filter in the quantization domain;

wherein inverse quantizing the quantized weighted residual version of the vector comprises variable bit rate inverse quantizing the quantized weighted residual version of the vector.

35. An LPC filter inverse quantizing method according to claim 34, wherein variable bit rate inverse quantizing the quantized weighted residual version of the vector comprises inverse algebraic vector quantizing the quantized weighted residual version of the vector.