Systems, methods, and apparatus for quantization of spectral envelope representation

1. A method for signal processing, said method comprising performing each of the following acts within a device that is configured to process speech signals:

encoding a first frame and a second frame of a speech signal to produce corresponding first and second vectors, wherein the first vector describes a spectral envelope of the speech signal during the first frame and the second vector describes a spectral envelope of the speech signal during the second frame;

generating a first quantized vector, said generating including quantizing a third vector that is based on the first vector;

dequantizing the first quantized vector to produce a first dequantized vector;

calculating a quantization error of the first quantized vector, wherein the quantization error indicates a difference between the first dequantized vector and one among the first and third vectors;

calculating a fourth vector, said calculating of the fourth vector including adding a scaled version of the quantization error to the second vector; and

quantizing the fourth vector,

wherein the third vector describes a spectral envelope of the speech signal during the first frame and the fourth vector describes a spectral envelope of the speech signal during the second frame.

2. The method according to claim 1 , wherein each among the first and second vectors includes a representation of a plurality of linear prediction filter coefficients.

3. The method according to claim 1 , wherein each among the first and second vectors includes a plurality of line spectral frequencies.

4. A non-transitory data storage medium having machine-executable instructions describing the method according to claim 1 .

5. The method according to claim 1 , wherein the second frame immediately follows the first frame in the speech signal.

6. The method according to claim 1 , wherein each among the first and second vectors represents an adaptively smoothed spectral envelope.

7. The method according to claim 1 , wherein said method comprises:

dequantizing the fourth vector; and

calculating an excitation signal based on the dequantized fourth vector.

8. The method according to claim 1 , wherein said speech signal is a narrowband speech signal, and

wherein said method comprises filtering a wideband speech signal to obtain the narrowband speech signal and a highband speech signal.

9. The method according to claim 1 , wherein said speech signal is a highband speech signal, and

wherein said method comprises filtering a wideband speech signal to obtain a narrowband speech signal and the highband speech signal.

10. The method according to claim 1 , wherein said speech signal is a narrowband speech signal, and

wherein said method comprises:

filtering a wideband speech signal to obtain the narrowband speech signal and a highband speech signal;

dequantizing the fourth vector;

based on the dequantized fourth vector, calculating an excitation signal for the narrowband speech signal; and

based on the excitation signal for the narrowband speech signal, deriving an excitation signal for the highband speech signal.

11. The method according to claim 1 , wherein said quantizing the fourth vector comprises performing a split vector quantization of the fourth vector.

12. The method according to claim 1 , wherein said calculating a quantization error includes calculating a difference between the first dequantized vector and the first vector.

13. The method according to claim 1 , wherein said calculating a quantization error includes calculating a difference between the first dequantized vector and the third vector.

14. The method according to claim 1 , said method including calculating the scaled version of the quantization error, said calculating comprising multiplying the quantization error by a scale factor,

wherein the scale factor is based on a distance between the first vector and the second vector.

15. The method according to claim 1 , wherein the third vector is a smoothed version of the first vector.

16. A non-transitory computer-readable medium comprising instructions which when executed by a processor cause the processor to:

encode a first frame and a second frame of a speech signal to produce corresponding first and second vectors, wherein the first vector describes a spectral envelope of the speech signal during the first frame and the second vector describes a spectral envelope of the speech signal during the second frame;

generate a first quantized vector, said generating including quantizing a third vector that is based on the first vector;

dequantize the first quantized vector to produce a first dequantized vector;

calculate a quantization error of the first quantized vector, wherein the quantization error indicates a difference between the first dequantized vector and one among the first and third vectors;

calculate a fourth vector, said calculating of the fourth vector including adding a scaled version of the quantization error to the second vector; and

quantize the fourth vector,

wherein the third vector describes a spectral envelope of the speech signal during the first frame and the fourth vector describes a spectral envelope of the speech signal during the second frame.

17. The computer-readable medium according to claim 16 , wherein the instructions that cause the processor to calculate a quantization error include instructions to calculate a difference between the first quantized vector and the third vector.

18. The computer-readable medium according to claim 16 , the instructions that cause the processor to calculate the scaled quantization error, further comprise instructions to:

multiply the quantization error by a scale factor, wherein the scale factor is based on a distance between at least a portion of the first vector and a corresponding portion of the second vector.

19. The computer-readable medium according to claim 18 , wherein each among the first and second vectors includes a plurality of line spectral frequencies.

20. The computer-readable medium according to claim 16 , wherein each among the first and second vectors includes a representation of a plurality of linear prediction filter coefficients.

21. The computer-readable medium according to claim 16 , wherein the instructions that cause the processor to calculate a quantization error include instructions to calculate a difference between the first quantized vector and the first vector.

22. An apparatus comprising:

a speech encoder configured to encode a first frame and a second frame of a speech signal to produce corresponding first and second vectors, wherein the first vector describes a spectral envelope of the speech signal during the first frame and the second vector describes a spectral envelope of the speech signal during the second frame;

a quantizer configured to quantize a third vector that is based on the first vector to generate a first quantized vector;

an inverse quantizer configured to dequantize the first quantized vector to produce a first dequantized vector;

a first adder configured to calculate a quantization error of the first quantized vector, wherein the quantization error indicates a difference between the first dequantized vector and one among the first and third vectors; and

a second adder configured to add a scaled version of the quantization error to the second vector to calculate a fourth vector,

wherein said quantizer is configured to quantize the fourth vector, and

wherein the third vector describes a spectral envelope of the speech signal during the first frame and the fourth vector describes a spectral envelope of the speech signal during the second frame.

23. The apparatus according to claim 22 , wherein said first adder is configured to calculate the quantization error based on a difference between the first quantized vector and the third vector.

24. The apparatus according to claim 22 , said apparatus including a multiplier configured to calculating the scaled quantization error based on a product of the quantization error and a scale factor,

wherein said apparatus includes logic configured to calculate the scale factor based on a distance between at least a portion of the first vector and a corresponding portion of the second vector.

25. The apparatus according to claim 24 , wherein each among the first and second vectors includes a plurality of line spectral frequencies.

26. The apparatus according to claim 22 , wherein each among the first and second vectors includes a representation of a plurality of linear prediction filter coefficients.

27. The apparatus according to claim 22 , wherein each among the first and second vectors includes a plurality of line spectral frequencies.

28. The apparatus according to claim 22 , said apparatus comprising a device for wireless communications.

29. The apparatus according to claim 22 , said apparatus comprising a device configured to transmit a plurality of packets compliant with a version of the Internet Protocol, wherein the plurality of packets describes the first quantized vector.

30. The apparatus according to claim 22 , wherein the second frame immediately follows the first frame in the speech signal.

31. The apparatus according to claim 22 , wherein each among the first and second vectors represents an adaptively smoothed spectral envelope.

32. The apparatus according to claim 22 , wherein said apparatus comprises:

an inverse quantizer configured to dequantize the fourth vector; and

a whitening filter configured to calculate an excitation signal based on the dequantized fourth vector.

33. The apparatus according to claim 22 , wherein said speech signal is a narrowband speech signal, and

wherein said apparatus comprises a filter bank configured to filter a wideband speech signal to obtain the narrowband speech signal and a highband speech signal.

34. The apparatus according to claim 22 , wherein said speech signal is a highband speech signal, and

wherein said apparatus comprises a filter bank configured to filter a wideband speech signal to obtain a narrowband speech signal and the highband speech signal.

35. The apparatus according to claim 22 , wherein said speech signal is a narrowband speech signal, and

wherein said apparatus comprises:

a filter bank configured to filter a wideband speech signal to obtain the narrowband speech signal and a highband speech signal;

an inverse quantizer configured to dequantize the fourth vector;

a whitening filter configured to calculate an excitation signal for the narrowband speech signal based on the dequantized fourth vector; and

a highband encoder configured to derive an excitation signal for the highband speech signal based on the excitation signal for the narrowband speech signal.

36. The apparatus according to claim 22 , wherein said quantizer is configured to quantize the fourth vector by performing a split vector quantization of the fourth vector.

37. The apparatus according to claim 22 , wherein said first adder is configured to calculate the quantization error based on a difference between the first quantized vector and the third vector.

38. The apparatus according to claim 22 , wherein the third vector is a smoothed version of the first vector.

39. An apparatus comprising:

means for encoding a first frame and a second frame of a speech signal to produce corresponding first and second vectors, wherein the first vector describes a spectral envelope of the speech signal during the first frame and the second vector describes a spectral envelope of the speech signal during the second frame;

means for generating a first quantized vector, said generating including quantizing a third vector that is based on the first vector;

means for dequantizing the first quantized vector to produce a first dequantized vector;

means for calculating a quantization error of the first quantized vector, wherein the quantization error indicates a difference between the first dequantized vector and one among the first and third vectors;

means for calculating a fourth vector, said calculating of the fourth vector including adding a scaled version of the quantization error to the second vector; and

means for quantizing the fourth vector,

wherein the third vector describes a spectral envelope of the speech signal during the first frame and the fourth vector describes a spectral envelope of the speech signal during the second frame.

40. The apparatus according to claim 39 , wherein said means for calculating a quantization error is configured to calculate the quantization error based on a difference between the first quantized vector and the third vector.

41. The apparatus according to claim 39 , said apparatus including means for calculating the scaled quantization error, said calculating comprising multiplying the quantization error by a scale factor,

wherein said apparatus comprises logic configured to calculate the scale factor based on a distance between at least a portion of the first vector and a corresponding portion of the second vector.

42. The apparatus according to claim 41 , wherein each among the first and second vectors includes a plurality of line spectral frequencies.

43. The apparatus according to claim 39 , said apparatus comprising a device for wireless communications.

44. The apparatus according to claim 39 , wherein the second frame immediately follows the first frame in the speech signal.

45. The apparatus according to claim 39 , wherein each among the first and second vectors represents an adaptively smoothed spectral envelope.

46. The apparatus according to claim 39 , wherein said apparatus comprises:

means for dequantizing the fourth vector; and

means for calculating an excitation signal based on the dequantized fourth vector.

47. The apparatus according to claim 39 , wherein said speech signal is a narrowband speech signal, and

wherein said apparatus comprises means for filtering a wideband speech signal to obtain the narrowband speech signal and a highband speech signal.

48. The apparatus according to claim 39 , wherein said speech signal is a highband speech signal, and

wherein said apparatus comprises means for filtering a wideband speech signal to obtain a narrowband speech signal and the highband speech signal.

49. The apparatus according to claim 39 , wherein said speech signal is a narrowband speech signal, and

wherein said apparatus comprises:

means for filtering a wideband speech signal to obtain the narrowband speech signal and a highband speech signal;

means for dequantizing the fourth vector;

means for calculating an excitation signal for the narrowband speech signal based on the dequantized fourth vector; and

means for deriving an excitation signal for the highband speech signal based on the excitation signal for the narrowband speech signal.

50. The apparatus according to claim 39 , wherein said means for generating a first quantized vector is configured to quantize the fourth vector by performing a split vector quantization of the fourth vector.

51. The apparatus according to claim 39 , wherein said means for calculating a quantization error is configured to calculate the quantization error based on a difference between the first quantized vector and the third vector.