Method and Device for Coding Transition Frames in Speech Signals

• US 20100241425A1
• Filed: 10/24/2007
• Published: 09/23/2010
• Est. Priority Date: 10/24/2006
• Status: Active Grant

• Current Assignee: VoiceAge EVS LLC (SoftBank Group Corp.)
• Original Assignee: VoiceAge Corporation
• Inventors: Salami, Redwan, Jelinek, Milan, Eksler, Vaclav
• Granted Patent: US 8,401,843 B2
• Time in Patent Office: Days
• US Class Current: 704/220
• CPC Class Codes: G10L 19/08 Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders

Abstract

There is provided a transition mode device and method for use in a predictive-type sound signal codec for producing a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in the sound signal, comprising an input for receiving a codebook index and a transition mode codebook for generating a set of codevectors independent from past excitation. The transition mode codebook is responsive to the index for generating, in the transition frame and/or frame following the transition, one of the codevectors of the set corresponding to the transition mode excitation. There is also provided an encoding device and method and a decoding device and method using the above described transition mode device and method.

Claims

1. A transition mode device for use in a predictive-type sound signal codec for producing a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in the sound signal, comprising:

an input for receiving a codebook index; and

a transition mode codebook for generating a set of codevectors independent from past excitation, the transition mode codebook being responsive to the index for generating, in the transition frame and/or frame following the transition, one of the codevectors of the set corresponding to said transition mode excitation.

2. A transition mode device as defined in claim 1, wherein the transition mode codebook comprises a fixed codebook independent from past excitation.

4. A transition mode device as defined in claim 1, wherein the transition mode codebook comprises a codebook of glottal impulse shapes.

5. A transition mode device as defined in claim 1, wherein the sound signal comprises a speech signal and wherein the transition frame is selected from the group consisting of a frame comprising a voiced onset and a frame comprising a transition between two different voiced sounds.

6. A transition mode device as defined in claim 1, wherein the transition frame and/or the frame following the transition comprise a transition frame followed by several frames.

8. A transition mode device as defined in claim 1, wherein the transition frame and/or the frame following the transition comprises at least one frame following the transition.

10. A transition mode device as defined in claim 1, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes, and wherein the transition mode codebook is used in a first part of the subframes and a predictive-type codebook of the predictive-type codec is used in a second part of the subframes.

11. A transition mode device as defined in claim 1, wherein the codebook comprises a glottal-shape codebook comprising codevectors formed of a glottal impulse shape placed at a specific position in the codevector.

12. A transition mode device as defined in claim 11, wherein the glottal-shape codebook includes a predetermined number of different shapes of glottal impulses, and wherein each shape of glottal impulse is positioned at a plurality of different positions in the codevector to form a plurality of different codevectors of the glottal-shape codebook.

13. A transition mode device as defined in claim 11, wherein the glottal-shape codebook comprises a generator of codevectors containing only one non-zero element and a shaping filter for processing the codevectors containing only one non-zero element to produce codevectors representing glottal impulse shapes centered at different positions.

16. A transition mode device as defined in claim 11, wherein the glottal-shape impulses comprises first and last samples wherein a predetermined number of the first and last samples are truncated.

3. (canceled)

7. (canceled)

9. (canceled)

14-15. -15. (canceled)

17. (canceled)

18. An encoder device for generating a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in a sound signal, comprising:

a generator of a codebook search target signal;

a transition mode codebook for generating a set of codevectors independent from past excitation, the codevectors of said set each corresponding to a respective transition mode excitation;

a searcher of the transition mode codebook for finding the codevector of said set corresponding to a transition mode excitation optimally corresponding to the codebook search target signal.

19. An encoder device as defined in claim 18, wherein the transition mode codebook comprises a fixed codebook independent from past excitation.

20. An encoder device as defined in claim 18, wherein the transition mode codebook comprises a codebook of glottal impulse shapes.

21. An encoder device as defined in claim 20, wherein the searcher applies a given criterion to every glottal impulse shape of the codebook of glottal impulse shapes and finds as the codevector optimally corresponding to the adaptive codebook search target signal the codevector of the set corresponding to a maximum value of said criterion.

22. An encoder device as defined in claim 21, wherein the searcher identifies the found codevector by means of transition mode parameters selected from the group consisting of a transition mode configuration identification, a glottal impulse shape, a position of the glottal impulse shape centre in the found codevector, a transition mode gain, a sign of the transition mode gain and a closed-loop pitch period.

23. An encoder device as defined in claim 18, wherein the sound signal comprises a speech signal and wherein the transition frame is selected from the group consisting of a frame comprising a voiced onset and a frame comprising a transition between two different voiced sounds.

24. An encoder device as defined in claim 18, wherein the transition frame and/or the frame following the transition comprise a transition frame followed by several frames.

26. An encoder device as defined in claim 18, wherein the transition frame and/or the frame following the transition comprises at least one frame following the transition.

27. An encoder device as defined in claim 18, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes, and wherein the searcher searches the transition mode codebook in a first part of the subframes and a predictive-type codebook of the encoder device in a second part of the subframes.

28. An encoder device as defined in claim 18, wherein the transition mode codebook comprises a glottal-shape codebook comprising codevectors formed of a glottal impulse shape placed at a specific position in the codevector.

29. An encoder device as defined in claim 28, wherein the glottal-shape codebook includes a predetermined number of different shapes of glottal impulses, and wherein each shape of glottal impulse is positioned at a plurality of different positions in the codevector to faun a plurality of different codevectors of the glottal-shape codebook.

30. An encoder device as defined in claim 28, wherein the glottal-shape codebook comprises a generator of codevectors containing only one non-zero element and a shaping filter for processing the codevectors containing only one non-zero element to produce codevectors representing glottal impulse shapes centered at different positions.

35. An encoder device as defined in claim 18, further comprising:

a generator of an innovation codebook search target signal;

an innovation codebook for generating a set of innovation codevectors each corresponding to a respective innovation excitation;

a searcher of the innovation codebook for finding the innovation codevector of said set corresponding to an innovation excitation optimally corresponding to the innovation codebook search target signal; and

an adder of the transition mode excitation and the innovation excitation to produce a global excitation for a sound signal synthesis filter.

36. An encoder device as defined in claim 35, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes and wherein, depending on where the glottal impulse or impulses are located in the subframes, the encoder device comprises means for encoding the subframes using at least one of the transition mode codebook, the adaptive codebook and the innovation codebook.

25. (canceled)

31-34. -34. (canceled)

37. A decoder device for generating a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in a sound signal, comprising:

an input for receiving a codebook index;

a transition mode codebook for generating a set of codevectors independent from past excitation, the transition mode codebook being responsive to the index for generating in the transition frame and/or frame following the transition one of the codevectors of the set corresponding to the transition mode excitation.

38. A decoder device as defined in claim 37, wherein the transition mode codebook comprises a fixed codebook independent from past excitation.

40. A decoder device as defined in claim 37, wherein the transition mode codebook comprises a codebook of glottal impulse shapes.

41. A decoder device as defined in claim 37, wherein the sound signal comprises a speech signal and wherein the transition frame is selected from the group consisting of a frame comprising a voiced onset and a frame comprising a transition between two different voiced sounds.

42. A decoder device as defined in claim 37, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes, and wherein the transition mode codebook is used in a first part of the subframes and the decoder device comprises a predictive-type codebook that is used in a second part of the subframes.

43. A decoder device as defined in claim 37, wherein the transition mode codebook comprises a glottal-shape codebook comprising codevectors formed of a glottal impulse shape placed at a specific position in the codevector.

44. A decoder device as defined in claim 43, wherein the glottal-shape codebook includes a predetermined number of different shapes of glottal impulses, and wherein each shape of glottal impulse is positioned at a plurality of different positions in the codevector to form a plurality of different codevectors of the glottal-shape codebook.

45. A decoder device as defined in claim 43, wherein the glottal-shape codebook comprises a generator of codevectors containing only one non-zero element and a shaping filter for processing the codevectors containing only one non-zero element to produce codevectors representing glottal impulse shapes centered at different positions.

47. A decoder device as defined in claim 37, further comprising:

an input for receiving an innovation codebook index;

an innovation codebook for generating a set of innovation codevectors, the innovation codebook being responsive to the innovation codebook index for generating in the transition frame and/or frame following the transition one of the innovation codevectors of the set corresponding to an innovation excitation;

an adder of the transition mode excitation and the innovation excitation to produce a global excitation for a sound signal synthesis filter.

39. (canceled)

46. (canceled)

48. A transition mode method for use in a predictive-type sound signal codec for producing a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in the sound signal, comprising:

providing a transition mode codebook for generating a set of codevectors independent from past excitation;

supplying a codebook index to the transition mode codebook; and

generating, by means of the transition mode codebook and in response to the codebook index, one of the codevectors of the set corresponding to said transition mode excitation.

49. A transition mode method as defined in claim 48, wherein the transition mode codebook comprises a fixed codebook independent from past excitation.

51. A transition mode method as defined in claim 48, wherein the transition mode codebook comprises a codebook of glottal impulse shapes.

52. A transition mode method as defined in claim 48, wherein the sound signal comprises a speech signal and said method comprises selecting the transition frame from the group consisting of a frame comprising a voiced onset and a frame comprising a transition between two different voiced sounds.

53. A transition mode method as defined in claim 48, wherein the transition frame and/or the frame following the transition comprise a transition frame followed by several frames.

55. A transition mode method as defined in claim 48, wherein the transition frame and/or the frame following the transition comprises at least one frame following the transition.

57. A transition method as defined in claim 48, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes, and said method comprises using the transition mode codebook in a first part of the subframes and a predictive-type codebook of the predictive-type codec in a second part of the subframes.

58. A transition mode method as defined in claim 48, wherein providing a transition mode codebook comprises providing a glottal-shape codebook comprising codevectors formed of a glottal impulse shape placed at a specific position in the codevector.

59. A transition mode method as defined in claim 58, wherein providing a glottal-shape codebook comprises providing a glottal-shape codebook including a predetermined number of different shapes of glottal impulses and forming in the glottal-shape codebook a plurality of different codevectors by positioning each shape of glottal impulse at a plurality of different positions in the codevector.

60. A transition mode method as defined in claim 58, comprising, in the glottal-shape codebook, generating codevectors containing only one non-zero element and processing through a shaping filter the codevectors containing only one non-zero element to produce codevectors representing glottal impulse shapes centered at different positions.

63. A transition mode method as defined in claim 58, wherein the glottal-shape impulses comprises first and last samples, said method comprising truncating a predetermined number of the first and last samples.

50. (canceled)

54. (canceled)

56. (canceled)

61-62. -62. (canceled)

64. (canceled)

65. An encoding method for generating a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in a sound signal, comprising:

generating a codebook search target signal;

providing a transition mode codebook for generating a set of codevectors independent from past excitation, the codevectors of said set each corresponding to a respective transition mode excitation;

searching the transition mode codebook for finding the codevector of said set corresponding to a transition mode excitation optimally corresponding to the codebook search target signal.

66. An encoding method as defined in claim 65, wherein providing a transition mode codebook comprises providing a fixed codebook independent from past excitation.

67. An encoding method as defined in claim 65, wherein providing a transition mode codebook comprises providing a codebook of glottal impulse shapes.

68. An encoding method as defined in claim 67, wherein searching the transition mode codebook comprises applying a given criterion to every glottal impulse shape of the codebook of glottal impulse shapes and finds as the codevector optimally corresponding to the adaptive codebook search target signal the codevector of the set corresponding to a maximum value of said criterion.

69. An encoding method as defined in claim 68, wherein searching the transition mode codebook comprises identifying the found codevector by means of transition mode parameters selected from the group consisting of a transition mode configuration identification, a glottal impulse shape, a position of the glottal impulse shape centre in the found codevector, a transition mode gain, a sign of the transition mode gain and a closed-loop pitch period.

70. An encoding method as defined in claim 65, wherein the sound signal comprises a speech signal and said method further comprises selecting the transition frame from the group consisting of a frame comprising a voiced onset and a frame comprising a transition between two different voiced sounds.

71. An encoding method as defined in claim 65, wherein the transition frame and/or the frame following the transition comprise a transition frame followed by several frames.

73. An encoding method as defined in claim 65, wherein the transition frame and/or the frame following the transition comprises at least one frame following the transition.

74. An encoding method as defined in claim 65, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes, and wherein searching the transition mode codebook comprises searching the transition mode codebook in a first part of the subframes and searching a predictive-type codebook of the encoder device in a second part of the subframes.

75. An encoding method as defined in claim 65, wherein providing a transition mode codebook comprises providing a glottal-shape codebook comprising codevectors formed of a glottal impulse shape placed at a specific position in the codevector.

76. An encoding method as defined in claim 75, wherein providing a glottal-shape codebook comprises providing a glottal-shape codebook including a predetermined number of different shapes of glottal impulses, and forming a plurality of different codevectors of the glottal-shape codebook by positioning each shape of glottal impulse at a plurality of different positions in the codevector.

77. An encoding method as defined in claim 75, wherein generating in the glottal-shape codebook a set of codevectors independent from past excitation comprises generating codevectors containing only one non-zero element and processing through a shaping filter the codevectors containing only one non-zero element to produce codevectors representing glottal impulse shapes centered at different positions.

82. An encoding method as defined in claim 65, further comprising:

generating an innovation codebook search target signal;

providing an innovation codebook for generating a set of innovation codevectors each corresponding to a respective innovation excitation;

searching the innovation codebook for finding the innovation codevector of said set corresponding to an innovation excitation optimally corresponding to the innovation codebook search target signal; and

adding the transition mode excitation and the innovation excitation to produce a global excitation for a sound signal synthesis filter.

83. An encoding method as defined in claim 82, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes and wherein, depending on where the glottal impulse or impulses are located in the subframes, the encoding method comprises encoding the subframes using at least one of the transition mode codebook, the adaptive codebook and the innovation codebook.

72. (canceled)

78-81. -81. (canceled)

84. A decoding method for generating a transition mode excitation replacing an adaptive codebook excitation in a transition frame and/or a frame following the transition in a sound signal, comprising:

receiving a codebook index;

supplying the codebook index to a transition mode codebook for generating a set of codevectors independent from past excitation; and

generating, by means of the transition mode codebook and in response to the codebook index, one of the codevectors of the set corresponding to the transition mode excitation.

85. A decoding method as defined in claim 84, wherein the transition mode codebook comprises a fixed codebook independent from past excitation.

87. A decoding method as defined in claim 84, comprising providing as the transition mode codebook a codebook of glottal impulse shapes.

88. A decoding method as defined in claim 84, wherein the sound signal comprises a speech signal and wherein said method comprises selecting the transition frame from the group consisting of a frame comprising a voiced onset and a frame comprising a transition between two different voiced sounds.

89. A decoding method as defined in claim 84, wherein the transition frame and/or the frame following the transition each comprise a plurality of subframes, and wherein said method comprises using the transition mode codebook in a first part of the subframes and a predictive-type codebook in a second part of the subframes.

90. A decoding method as defined in claim 84, comprising providing as the transition mode codebook a glottal-shape codebook comprising codevectors formed of a glottal impulse shape placed at a specific position in the codevector.

91. A decoding method as defined in claim 90, wherein the glottal-shape codebook includes a predetermined number of different shapes of glottal impulses, and wherein said method comprises forming a plurality of different codevectors of the glottal-shape codebook by positioning each shape of glottal impulse at a plurality of different positions in the codevector.

92. A decoding method as defined in claim 90, wherein codevectors of the set are generated by the glottal-shape codebook by generating codevectors containing only one non-zero element and processing through a shaping filter the codevectors containing only one non-zero element to produce codevectors representing glottal impulse shapes centered at different positions.

94. A decoding method as defined in claim 84, further comprising:

providing an innovation codebook for generating a set of innovation codevectors;

supplying an innovation codebook index to the innovation codebook;

generating, by means of the innovation codebook and in response to the innovation codebook index, one of the innovation codevectors of the set corresponding to an innovation excitation; and

adding the transition mode excitation and the innovation excitation to produce a global excitation for a sound signal synthesis filter.

86. (canceled)

93. (canceled)