Coefficient splitting structure for vector quantization bit allocation and dequantization

• US 8,630,849 B2
• Filed: 11/15/2006
• Issued: 01/14/2014
• Est. Priority Date: 11/15/2005
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Son, Chang-Yong, Oh, Eun-Mi, Sung, Ho-Sang, Lee, Kang-Eun, Choo, Ki-Hyun, Kim, Jung-Hoe
• Primary Examiner(s): PULLIAS, JESSE SCOTT
• Application Number:
  US11/911,775
• Publication Number:
  US 20080183465A1
• Time in Patent Office: 2,617 Days
• Field of Search: None
• US Class Current: 704/222
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders
• CPC Class Codes: G10L 2019/0005 Multi-stage vector quantisation

Abstract

A method and apparatus to convert a linear predictive coding (LPC) coefficient into a coefficient having order characteristics, such as a line spectrum frequency (LSF), and to vector quantize the coefficient having the order characteristics when a speech signal is encoded. The method and apparatus split the vector of the coefficient having the order characteristics into a plurality of subvectors, select a codebook in which an available bit is variably allocated to each subvector according to distribution of elements of each subvector, and quantize each subvector according to the selected codebook. The method and apparatus use normalized codebooks.

Claims

1. A method of converting a linear predictive coding (LPC) coefficient into a coefficient having order characteristics and quantizing the coefficient, the method comprising:

splitting a vector of the coefficient having the order characteristics into a plurality of subvectors;

selecting a codebook in which an available bit is allocated to each of the subvectors according to a distribution of elements of each of the subvectors; and

quantizing, performed by using at least one processor, each of the subvectors using the selected codebook and generating a codebook index of each of the subvectors,

wherein a different available bit is allocated to subvectors in each of a plurality of normalized codebooks for use in quantizing lower subvectors, according to a distribution of elements of the subvectors.

2. The method of claim 1, wherein the coefficient having the order characteristics is any one of a line spectrum frequency (LSF), a line spectral pair (LSP), immittance spectral frequencies (ISFs), and an immittance spectral pair (ISP) coefficient.

3. The method of claim 1, wherein the splitting of the vector of the coefficient comprises:

splitting the vector of the coefficient having the order characteristics into an upper subvector including anchor elements among elements that constitute the vector of the coefficient having the order characteristics and the lower subvectors, each including elements respectively interposed between the elements of the upper subvector.

4. The method of claim 3, wherein the selecting of the codebook comprises:

quantizing the upper subvector and generating a codebook index; and

selecting a codebook in which an available bit is allocated to each lower subvector according to a ratio of intervals between elements of the quantized upper subvector.

5. The method of claim 3, wherein the selecting of the codebook comprises:

quantizing the upper subvector and generating a codebook index; and

selecting a codebook in which an available bit is allocated to each lower subvector according to an existence range of a predetermined quantized element among the elements of the quantized upper subvector.

6. The method of claim 3, wherein the selecting of the codebook comprises:

quantizing the upper subvector and generating a plurality of codebook indices; and

selecting codebooks in which available bits are respectively allocated to the lower subvectors using the generated codebook indices; and

detecting a codebook index having a smallest distortion from the codebook indices using a result of the quantization.

7. The method of claim 3, wherein the codebook is normalized.

8. The method of claim 7, wherein the codebook is normalized using the elements of the upper subvector.

9. The method of claim 8, wherein the normalized codebook is obtained after a value of whichever is smaller between the elements of the upper subvector is subtracted from each codeword of each lower subvector between the elements of the upper subvector and then a result of the subtraction is divided by a value corresponding to a difference between the elements of the upper subvector.

10. The method of claim 8, wherein the quantizing of each of the subvectors comprises:

multiplying each codeword value of each lower subvector between the elements of the upper subvector by a value corresponding to the difference between the elements of the upper subvector;

and adding a value of a smaller element between the elements of the upper subvector to a result of the multiplication.

11. The method of claim 1, wherein the selecting of the codebook comprises:

selecting a group of codebooks in which a different available bit is allocated to each of the subvectors from a plurality of groups of codebooks; and

selecting a codebook from the selected group according to a bit allocated to each of the subvectors.

12. A method of de-quantizing an LPC coefficient into an LSF using a codebook index generated after an encoder converts the LPC coefficient into a vector of a coefficient having order characteristics, splits the vector of the coefficient into an upper subvector and lower subvectors, and quantizes the upper and lower subvectors, the method comprising:

de-quantizing the upper subvector using a codebook index of the upper subvector;

selecting a codebook among a plurality of codebooks, using elements of the de-quantized upper subvector;

de-quantizing, performed by using at least one processor, each of the lower subvectors using a codebook index of each of the lower subvectors included in the selected codebook; and

generating an LSF vector using the de-quantized upper subvector and the de-quantized lower subvectors,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks, according to a distribution of elements of the subvectors.

13. The method of claim 12, wherein the coefficient having the order characteristics is any one of an LSF, an LSP, ISFs, and an ISP coefficient.

14. The method of claim 12, wherein the codebook is normalized.

15. The method of claim 14, wherein the codebook is normalized using the elements of the upper subvector.

16. The method of claim 15, wherein the normalized codebook is obtained after a value of whichever is smaller between the elements of the upper subvector is subtracted from each codeword of each lower subvector between the elements of the upper subvector and then a result of the subtraction is divided by a value corresponding to a difference between the elements of the upper subvector.

17. The method of claim 16, wherein the de-quantizing of the upper subvector and the lower subvectors comprises:

multiplying each codeword value of each lower subvector between the elements of the upper subvector by a value corresponding to the difference between the elements of the upper subvector; and

adding a value of a smaller element between the elements of the upper subvector to a result of the multiplication.

18. A method of generating a codebook, the method comprising:

splitting a vector of a coefficient having order characteristics, which was converted from an LPC coefficient, into an upper subvector including of anchor elements among elements that constitute the vector of the coefficient having the order characteristics and lower subvectors, each including elements respectively interposed between the elements of the upper subvector;

classifying each of the lower subvectors by allocating an available bit to each of the lower subvectors using the upper subvector; and

generating, performed by using at least one processor, a codebook by training the upper subvector and each of the classified subvectors,

wherein a different available bit is allocated to subvectors in each of a plurality of codebooks for use in quantizing and dequantizing the lower subvectors, according to a distribution of elements of the subvectors.

19. The method of claim 18, wherein the coefficient having the order characteristics is any one of an LSF, an LSP, ISFs, and an ISP coefficient.

20. The method of claim 18, wherein the classifying of each of the lower subvectors comprises:

classifying each of the lower subvectors by allocating an available bit to each of the lower subvectors according to a ratio of intervals between elements of the upper subvector.

21. The method of claim 18, wherein the classifying of each of the lower subvectors comprises:

classifying each of the lower subvectors by allocating an available bit to each of the lower subvectors according to an existence range of a predetermined element among the elements of the upper subvector.

22. The method of claim 18, wherein, in the generating of the codebook, the upper subvector and each of the classified subvectors are trained using a Linde, Buzo and Gray (LBG) algorithm.

23. The method of claim 18, wherein, in the generating of the codebook, the codebook is normalized using the elements of the upper subvector.

24. The method of claim 23, wherein, in the generating of the codebook, the codebook is normalized after a value of whichever is smaller between the elements of the upper subvector is subtracted from each codeword of each lower subvector between the elements of the upper subvector and then a result of the subtraction is divided by a value corresponding to a difference between the elements of the upper subvector.

25. The method of claim 18, wherein a maximum vector quantization dimension is set equal to or less than four when the coefficient is a tenth coefficient, and a maximum vector quantization dimension is set equal to or less than six when the coefficient is a sixth coefficient.

26. The method of claim 18, wherein a number of the elements of the upper subvector are limited to be equal to or less than four when the coefficient is the tenth coefficient, and the number of the elements of the upper subvector are set equal to or less than six when the coefficient is the sixth coefficient.

27. The method of claim 18, wherein the upper subvector is configured such that an intra-frame correlation between the elements of the upper subvector can be highest.

28. The method of claim 18, wherein the upper subvector is configured such that the elements of the upper subvector are placed on both sides of each of the lower subvectors.

29. The method of claim 18, wherein the upper subvector is configured such that the elements of the upper subvector are non-continuous.

30. A method of quantizing a linear predictive coding (LPC) coefficient, comprising:

converting an LPC coefficient into a coefficient having a vector;

splitting the vector into an upper subvector and plural lower subvectors;

quantizing, performed by using at least one processor, the upper subvector to generate upper subvector codebook indices;

selecting a codebook for use with the lower subvectors from a plurality of codebooks stored in a codebook storage unit based on the upper subvector codebook indices;

quantizing the plural lower subvectors using the selected codebook;

selecting a codebook index having a smallest distortion from the upper subvector codebook indices comprising;

allocating available bits in a codebook to each of the plural lower subvectors according to a predetermined value;

generating a codebook index for the upper subvector and each of the plural lower subvectors as a bitstream; and

transmitting the bitstream,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing the lower subvectors, according to a distribution of elements of the subvectors.

31. A non-transitory computer-readable medium having embodied thereon a computer program to execute a method of converting a linear predictive coding (LPC) coefficient into a coefficient having order characteristics and quantizing the coefficient, the method comprising:

splitting a vector of the coefficient having the order characteristics into a plurality of subvectors;

selecting a codebook among a plurality of codebooks, in which an available bit is allocated to each of the subvectors according to distribution of elements of each of the subvectors; and

quantizing each of the subvectors using the selected codebook and generating a codebook index of each of the subvectors,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing lower subvectors, according to a distribution of elements of the subvectors.

32. A non-transitory computer-readable medium having embodied thereon a computer program to execute a method of de-quantizing an LPC coefficient into an LSF using a codebook index generated after an encoder converts the LPC coefficient into a vector of a coefficient having order characteristics, splits the vector of the coefficient into an upper subvector and lower subvectors, and quantizes the upper and lower subvectors, the method comprising:

de-quantizing the upper subvector using a codebook index of the upper subvector;

selecting a codebook among a plurality of codebooks, using elements of the de-quantized upper subvector;

de-quantizing each of the lower subvectors using a codebook index of each of the lower subvectors included in the selected codebook; and

generating an LSF vector using the de-quantized upper subvector and the de-quantized lower subvectors,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks for use in dequantizing the lower subvectors, according to a distribution of elements of the subvectors.

33. A non-transitory computer-readable medium having embodied thereon a computer program to execute a method of generating a codebook, the method comprising:

splitting a vector of a coefficient having order characteristics, which was converted from an LPC coefficient, into an upper subvector comprised of anchor elements among elements that constitute the vector of the coefficient having the order characteristics and lower subvectors, each comprised of elements respectively interposed between the elements of the upper subvector;

classifying each of the lower subvectors by allocating an available bit to each of the lower subvectors using the upper subvector; and

generating a codebook by training the upper subvector and each of the classified subvectors,

wherein a different available bit is allocated to subvectors in each of a plurality of codebooks for use in quantizing and dequantizing the lower subvectors, according to a distribution of elements of the subvectors.

34. A non-transitory computer-readable medium having embodied thereon a computer program to execute a method of quantizing a linear predictive coding (LPC) coefficient, comprising:

converting an LPC coefficient into a coefficient having a vector;

splitting the vector into an upper subvector and plural lower subvectors;

quantizing the upper subvector to generate upper subvector codebook indices;

selecting a codebook for use with the lower subvectors from a plurality of codebooks stored in a codebook storage unit based on the upper subvector codebook indices;

quantizing the plural lower subvectors using the selected codebook;

selecting a codebook index having a smallest distortion from the upper subvector codebook indices comprising;

allocating available bits in a codebook to each of the plural lower subvectors according to a predetermined value;

generating a codebook index for the upper subvector and each of the plural lower subvectors as a bitstream; and

transmitting the bitstream,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing the lower subvectors, according to a distribution of elements of the subvectors.

35. An apparatus to convert an LPC coefficient into a coefficient having order characteristics and to quantize the coefficient, the apparatus comprising:

a vector split unit to split a vector of the coefficient having the order characteristics into a plurality of subvectors;

a codebook storage unit to store a plurality of codebooks in which an available bit is allocated to each of the subvectors according to a distribution of elements of each of the subvectors that constitute the vector of the coefficient having the order characteristics;

a codebook selection unit to select a codebook from the codebooks stored in the codebook storage unit according to the distribution of the elements of each of the subvectors; and

a quantization unit to quantize each of the subvectors using the selected codebook and to generate a codebook index of each of the subvectors,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing the lower subvectors, according to a distribution of elements of the subvectors.

36. The apparatus of claim 35, wherein the coefficient having the order characteristics is any one of an LSF, an LSP, ISFs, and an ISP coefficient.

37. The apparatus of claim 36, wherein the vector split unit splits the vector of the coefficient having the order characteristics into an upper subvector comprised of anchor elements among elements that constitute the vector of the coefficient having the order characteristics and lower subvectors, each comprised of elements respectively interposed between the elements of the upper subvector.

38. The apparatus of claim 37 wherein the codebook selection unit comprises:

a quantization unit to quantize the upper subvector and to generate a plurality of codebook indices;

a selection unit to select codebooks in which available bits are respectively allocated to the lower subvectors using the generated plurality of codebook indices; and

a detection unit to detect a codebook index having a smallest distortion from the codebook indices using the result of quantization.

39. The apparatus of claim 37, wherein the codebook storage unit stores normalized codebooks.

40. The apparatus of claim 39, wherein the codebook storage unit stores the codebooks normalized using the elements of the upper subvector.

41. The apparatus of claim 40, wherein the codebook storage unit stores the codebooks normalized after a value of whichever is smaller between the elements of the upper subvector is subtracted from each codeword of each lower subvector between the elements of the upper subvector and then a result of the subtraction is divided by a value corresponding to a difference between the elements of the upper subvector.

42. The apparatus of claim 41, wherein the quantization unit multiplies each codeword value of each lower subvector between the elements of the upper subvector by a value corresponding to the difference between the elements of the upper subvector and adds a value of a smaller element between the elements of the upper subvector to a result of the multiplication.

43. The apparatus of claim 36, wherein the codebook storage unit stores a plurality of groups of codebooks in which a different available bit is allocated to each of the subvectors, and the codebook selection unit comprises a first selection unit to select a group of codebooks from the groups of codebooks and a second selection unit to select a codebook from the selected group according to a bit allocated to each of the subvectors.

44. The apparatus of claim 35, wherein the codebook selection unit comprises:

a first quantization unit to quantize the upper subvector and to generate a codebook index; and

a selection unit to select a codebook in which an available bit is allocated to each lower subvector according to a ratio of intervals between elements of the quantized upper subvector.

45. An apparatus to de-quantize an LPC coefficient into an LSF using a codebook index generated after an encoder converts the LPC coefficient into a vector of a coefficient having order characteristics, splits the vector of the coefficient into an upper subvector and lower subvectors, and quantizes the upper subvector and the lower subvectors, the apparatus comprising:

a first de-quantization unit to de-quantize the upper subvector using a codebook index of the upper subvector;

a codebook storage unit storing a plurality of codebooks in which an available bit is allocated to each of the subvectors according to distribution of elements of each of the subvectors that constitute the vector of the coefficient having the order characteristics;

a codebook selection unit to select a codebook from the codebooks stored in the codebook storage unit using elements of the de-quantized upper subvector;

a second de-quantization unit to de-quantize each of the lower subvectors using a codebook index of each of the lower subvectors included in the selected codebook; and

a coefficient generation unit to generate an LSF vector using the de-quantized upper subvector and the de-quantized lower subvectors,

wherein a different available bit is allocated to subvectors in each of the plurality of codebooks for use in dequantizing the lower subvectors, according to a distribution of elements of the subvectors.

46. The apparatus of claim 45, wherein the coefficient having the order characteristics is any one of an LSF, an LSP, ISFs, and an ISP coefficient.

47. The apparatus of claim 45, wherein the codebook storage unit stores normalized codebooks.

48. The apparatus of claim 47, wherein the codebook storage unit stores the codebooks normalized using the elements of the upper subvector.

49. The apparatus of claim 48, wherein the codebook storage unit stores the codebooks normalized after a value of whichever is smaller between the elements of the upper subvector is subtracted from each codeword of each lower subvector between the elements of the upper subvector and then a result of the subtraction is divided by a value corresponding to a difference between the elements of the upper subvector.

50. The apparatus of claim 49, wherein the first and second de-quantization units multiply each codeword value of each lower subvector between the elements of the upper subvector by a value corresponding to the difference between the elements of the upper subvector and adds a value of a smaller element between the elements of the upper subvector to a result of the multiplication.

51. An apparatus to generate a codebook, the apparatus comprising:

a vector split unit to split a vector of a coefficient having order characteristics, which was converted from an LPC coefficient, into an upper subvector including anchor elements among elements that constitute the vector of the coefficient having the order characteristics and lower subvectors, each including elements respectively interposed between the elements of the upper subvector;

a vector classification unit to classify each of the lower subvectors by allocating an available bit to each of the lower subvectors using the upper subvector; and

a codebook generation unit to generate a codebook by training the upper subvector and each of the classified subvectors,

wherein a different available bit is allocated to subvectors in each of a plurality of codebooks for use in quantizing and dequantizing the lower subvectors, according to a distribution of elements of the subvectors.

52. The apparatus of claim 51, wherein the coefficient having the order characteristics is any one of an LSF, an LSP, ISFs, and an ISP coefficient.

53. The apparatus of claim 51, wherein the vector classification unit classifies each of the lower subvectors by allocating an available bit to each of the lower subvectors according to a ratio of intervals between elements of the upper subvector.

54. The apparatus of claim 51, wherein the vector classification unit classifies each of the lower subvectors by allocating an available bit to each of the lower subvectors according to an existence range of a predetermined element among the elements of the upper subvector.

55. The apparatus of claim 51, wherein the codebook generation unit trains the upper subvector and each of the classified subvectors using an LBG algorithm.

56. The apparatus of claim 51, wherein the codebook generation unit normalizes the codebook using the elements of the upper subvector.

57. The apparatus of claim 56, wherein the codebook generation unit normalizes the codebook by subtracting a value of whichever is smaller between the elements of the upper subvector from each codeword of each lower subvector between the elements of the upper subvector and then dividing the result of subtraction by a value corresponding to a difference between the elements of the upper subvector.

58. The apparatus of claim 51, wherein a maximum vector quantization dimension is set equal to or less than four when the coefficient is a tenth coefficient, and the maximum vector quantization dimension is set equal to or less than six when the coefficient is a sixth coefficient.

59. The apparatus of claim 51, wherein a number of the elements of the upper subvector are limited to be equal to or less than four when the coefficient is the tenth coefficient, and the number of the elements of the upper subvector are set equal to or less than six when the coefficient is the sixth coefficient.

60. The apparatus of claim 51, wherein the upper subvector is configured such that an intra-frame correlation between the elements of the upper subvector can be highest.

61. The apparatus of claim 51, wherein the upper subvector is configured such that the elements of the upper subvector are placed on both sides of each of the lower subvectors.

62. The apparatus of claim 51, wherein the upper subvector is configured such that the elements of the upper subvector are non-continuous.

63. An apparatus to convert an LPC coefficient into a predetermined coefficient and to quantize the coefficient, the apparatus comprising:

a vector split unit to split a vector of the predetermined coefficient into subvectors;

a codebook storage unit to store a plurality of codebooks in which an available bit is allocated to each of the subvectors according to a distribution of elements of each of the subvectors;

a codebook selection unit to select a codebook from the codebooks stored in the codebook storage unit according to the distribution of the elements of each of the subvectors; and

a quantization unit to quantize each of the subvectors using the selected codebook and to generate a codebook index of each of the subvectors,

wherein a different available bit is allocated to subvectors in each of a plurality of codebooks for use in quantizing lower subvectors, according to a distribution of elements of the subvectors.

64. The apparatus of claim 63, wherein the predetermined coefficient is an LSF coefficient.

65. An apparatus to generate a codebook, the apparatus comprising:

a vector split unit to split a vector of a predetermined coefficient into an upper subvector and plural lower subvectors, each subvector comprised of elements;

a vector classification unit to classify each of the lower subvectors using the elements of the upper subvector; and

a codebook generation unit to generate a codebook by training the upper subvector and each of the classified subvectors using an LGB algorithm,

wherein a different available bit is allocated to subvectors in each of a plurality of codebooks for use in quantizing lower subvectors, according to a distribution of elements of the subvectors.

66. A method of converting an LPC coefficient into a coefficient having order characteristics and quantizing the coefficient, the method comprising:

splitting a vector of the coefficient having the order characteristics into an upper subvector and lower subvectors;

quantizing, performed by using at least one processor, the upper subvector;

selecting a codebook among a plurality of codebooks in which an available bit is allocated to each of the lower subvectors according to distribution of elements of the quantized upper subvector;

normalizing elements of the lower subvectors; and

quantizing each of the lower subvectors using the selected codebook and generating a codebook index of each of the lower subvectors,

wherein the codebook is normalized and a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing the lower subvectors, according to a distribution of elements of the subvectors.

67. A method of de-quantizing an LPC coefficient into an LSF using a codebook index generated after an encoder converts the LPC coefficient into a vector of a coefficient having order characteristics, splits the vector of the coefficient into an upper subvector and lower subvectors, and quantizes the upper and lower subvectors, the method comprising:

de-quantizing, performed by using at least one processor, the upper subvector using a codebook index of the upper subvector;

selecting a normalized and pre-stored codebook among a plurality of normalized and pre-stored codebooks using elements of the de-quantized upper subvector;

de-quantizing each of the lower subvectors using a codebook index of each of the lower subvectors included in the selected codebook;

de-normalizing each of the de-quantized lower subvectors; and

generating an LSF vector using the de-quantized upper subvector and the de-normalized lower subvectors,

wherein a different available bit is allocated to subvectors in each of the plurality of normalized and pre-stored codebooks for use in de-quantizing the lower subvectors, according to a distribution of elements of the subvectors.

68. An apparatus for converting an LPC coefficient into a coefficient having order characteristics and quantizing the coefficient, the apparatus comprising:

a vector split unit splitting a vector of the coefficient having the order characteristics into an upper subvector and lower subvectors;

a first quantization unit quantizing the upper subvector;

a codebook storage unit storing a plurality of codebooks in which an available bit is allocated to each of the lower subvectors according to distribution of elements of the quantized upper subvector;

a codebook selection unit selecting a codebook from the plurality of codebooks stored in the codebook storage unit according to the distribution of the elements of the upper subvector;

a normalization unit normalizing elements of the lower subvectors; and

a second quantization unit quantizing each of the lower subvectors using the selected codebook and generating a codebook index of each of the lower subvectors,

wherein the codebooks are normalized and a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing the lower subvectors, according to a distribution of elements of the subvectors.

69. An apparatus for de-quantizing an LPC coefficient into an LSF using a codebook index generated after an encoder converts the LPC coefficient into a vector of a coefficient having order characteristics, splits the vector of the coefficient into an upper subvector and lower subvectors, and quantizes the upper and lower subvectors, the apparatus comprising:

a first de-quantization unit de-quantizing the upper subvector using a codebook index of the upper subvector;

a codebook storage unit storing a plurality of codebooks in which an available bit is allocated to each of the subvectors according to distribution of elements of each of the subvectors that constitute the vector of the coefficient having the order characteristics;

a codebook selection unit selecting a codebook from the plurality of codebooks stored in the codebook storage unit using elements of the de-quantized upper subvector;

a second de-quantization unit de-quantizing each of the lower subvectors using a codebook index of each of the lower subvectors included in the selected codebook;

a de-normalization unit de-normalizing each of the de-quantized lower subvectors; and

a coefficient generation unit generating an LSF vector using the de-quantized upper subvector and the de-normalized lower subvectors,

wherein the codebook is normalized and a different available bit is allocated to subvectors in each of the plurality of codebooks for use in quantizing the lower subvectors, according to a distribution of elements of the subvectors.

70. A non-transitory computer-readable recording medium on which a program for executing a method is recorded, the method comprising:

splitting a vector of a coefficient having order characteristics, which was converted from an LPC coefficient, into an upper subvector and lower subvectors;

quantizing the upper subvector;

selecting a normalized codebook among a plurality of normalized codebooks, in which an available bit is allocated to each of the lower subvectors according to distribution of elements of the quantized upper subvector;

normalizing elements of the lower subvectors; and

quantizing each of the lower subvectors using the selected codebook and generating a codebook index of each of the lower subvectors,

wherein a different available bit is allocated to the subvectors in each of the plurality of normalized codebooks, according to a distribution of elements of the subvectors.

71. A non-transitory computer-readable recording medium on which a program for executing a method is recorded, the method comprising:

de-quantizing an upper subvector using a codebook index of the upper subvector in a bitstream generated after an encoder converts an LPC coefficient into a vector of a coefficient having order characteristics, splits the vector of the coefficient into the upper subvector and lower subvectors, and quantizes the upper and lower subvectors;

selecting a normalized and pre-stored codebook among a plurality of normalized and pre-stored codebooks, using elements of the de-quantized upper subvector;

de-quantizing each of the lower subvectors using a codebook index of each of the lower subvectors included in the selected codebook;

de-normalizing each of the de-quantized lower subvectors; and

generating an LSF vector using the de-quantized upper subvector and the de-normalized lower subvectors,

wherein a different available bit is allocated to the subvectors in each of the plurality of normalized and pre-stored codebooks, according to a distribution of elements of the subvectors.