Gain-smoothing in wideband speech and audio signal decoder

US 7,191,123 B1
Filed: 11/17/2000
Issued: 03/13/2007
Est. Priority Date: 11/18/1999
Status: Expired due to Term

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1. A method for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said method comprising:

finding a codevector in relation to at least one first wideband signal encoding parameter of said set;

calculating a first factor representative of voicing in the wideband signal in response to at least one second wideband signal encoding parameter of said set;

calculating a second factor representative of stability of said wideband signal in response to at least one third wideband signal encoding parameter of said set;

calculating a smoothing gain based on said first and second factors; and

amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

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Abstract

The gain smoothing method and device modify the amplitude of an innovative codevector in relation to background noise present in a previously sampled wideband signal. The gain smoothing device comprises a gain smoothing calculator for calculating a smoothing gain in response to a factor representative of voicing in the sampled wideband signal, a factor representative of the stability of a set of linear prediction filter coefficients, and an innovative codebook gain. The gain smoothing device also comprises an amplifier for amplifying the innovative codevector with the smoothing gain to thereby produce a gain-smoothed innovative codevector. The function of the gain-smoothing device improves the perceived synthesized signal when background noise is present in the sampled wideband signal.

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103 Claims

1. A method for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said method comprising:
- finding a codevector in relation to at least one first wideband signal encoding parameter of said set;
  
  calculating a first factor representative of voicing in the wideband signal in response to at least one second wideband signal encoding parameter of said set;
  
  calculating a second factor representative of stability of said wideband signal in response to at least one third wideband signal encoding parameter of said set;
  
  calculating a smoothing gain based on said first and second factors; and
  
  amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- - 2. A gain-smoothed codevector producing method as claimed in claim 1, wherein:
    - finding a codevector comprises finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      the smoothing gain calculation comprises calculating the smoothing gain also in relation to an innovative codebook gain forming a fourth wideband signal encoding parameter of said set.
  - 3. A gain-smoothed codevector producing method as claimed in claim 1, wherein:
    - finding a codevector comprises finding a codevector in a codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one first wideband signal encoding parameter comprises an innovative codebook index.
  - 4. A gain-smoothed codevector producing method as claimed in claim 1, wherein:
    - finding a codevector comprises finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one second wideband signal encoding parameter comprises the following parameters;
      
      a pitch gain computed during encoding of the wideband signal;
      
      a pitch delay computed during encoding of the wideband signal;
      
      an index j of a low-pass filter selected during encoding of the wideband signal and applied to a pitch codevector computed during encoding of the wideband signal; and
      
      an innovative codebook index computed during encoding of the wideband signal.
  - 5. A gain-smoothed codevector producing method as claimed in claim 1, wherein said at least one third wideband signal encoding parameter comprises coefficients of a linear prediction filter calculated during encoding of the wideband signal.
  - 6. A gain-smoothed codevector producing method as claimed in claim 1, wherein:
    - finding a codevector comprises finding an innovative codevector in an innovative codebook in relation to an index k of said innovative codebook, said index k forming said at least one first wideband signal encoding parameter; and
      
      calculating a first factor comprises computing a voicing factor rv by means of the following relation;
      
      rv=(Ev−
      
      Ec)/(Ev+Ec)where;
      
      Ev is the energy of a scaled adaptive codevector bvT;
      
      Ec is the energy of a scaled innovative codevector gck;
      
      b is a pitch gain computed during encoding of the wideband signal;
      
      T is a pitch delay computed during encoding of the wideband signal;
      
      vT is an adaptive codebook vector at pitch delay T;
      
      g is an innovative codebook gain computed during encoding of the wideband signal;
      
      k is an index of the innovative codebook computed during encoding of the wideband signal; and
      
      ck is the innovative codevector of said innovative codebook at index k.
  - 7. A gain-smoothed codevector producing method as claimed in claim 6, wherein the voicing factor rv has a value located between −
    - 1 and 1, wherein value 1 corresponds to a pure voiced signal and value −
      
      1 corresponds to a pure unvoiced signals.
  - 8. A gain-smoothed codevector producing method as claimed in claim 7, wherein calculating a smoothing gain comprises computing a factor λ
    - using the following relation;
      
      λ
      
      =0.5(1−
      
      rv).
  - 9. A gain-smoothed codevector producing method as claimed in claim 6, wherein a factor λ
    - =0 indicates a pure voiced signal and a factor λ
      
      =1 indicates a pure unvoiced signal.
  - 10. A gain-smoothed codevector producing method as claimed in claim 1, wherein calculating a second factor comprises determining a distance measure giving a similarity between adjacent, successive linear prediction filters computed during encoding of the wideband signal.
  - 11. A gain-smoothed codevector producing method as claimed in claim 10, wherein:
    - the wideband signal is sampled prior to encoding, and is processed by frames during encoding and decoding; and
      
      determining a distance measure comprises calculating an Immitance Spectral Pair distance measure between the Immitance Spectral Pairs in a present frame n of the wideband signal and the Immitance Spectral Pairs of a past frame n−
      
      1 of the wideband signal through the following relation;
      
      $D_{s} = \sum_{i = 1}^{p - 1} {({isp}_{i}^{(n)} - {ispSUBi}^{(n - 1)})}^{2}$ where p is the order of the linear prediction filters.
  - 12. A gain-smoothed codevector producing method as claimed in claim 11, wherein calculating a second factor comprises mapping the Immitance Spectral Pair distance measure D_sto said second factor θ
    - through the following relation;
      
      θ
      
      =1.25−
      
      D_s/400000.0bounded by 0≦
      
      θ
      
      ≦
      
      1.
  - 13. A gain-smoothed codevector producing method as claimed in claim 1, wherein calculating a smoothing gain comprises calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      .
  - 14. A gain-smoothed codevector producing method as claimed in claim 13, wherein the factor S_mhas a value approaching 1 for an unvoiced and stable wideband signal, and a value approaching 0 for a pure voiced wideband signal or an unstable wideband signal.
  - 15. A gain-smoothed codevector producing method as claimed in claim 1, wherein:
    - finding a codevector comprises finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter;
      
      the wideband signal is sampled prior to encoding, and is processed by frames and subframes during encoding and decoding; and
      
      calculating a smoothing gain comprises computing an initial modified gain g₀by comparing an innovative codebook gain g computed during encoding of the wideband signal to a threshold given by the initial modified gain from the past subframe g−
      
      1 as follows;
      
      if g <
      
      g −
      
      1 then g₀= g ×
      
      1.19 bounded by g₀≦
      
      g −
      
      1 and if g ≧
      
      g −
      
      1 then g₀= g/1.19 bounded by g₀≧
      
      g −
      
      1.
  - 16. A gain-smoothed codevector producing method as claimed in claim 15, wherein calculating a smoothing gain comprises:
    - calculating a gain smoothing factor S_mbased on both the first λ and
      
      second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      ; and
      
      determining said smoothing gain through the following relation;
      
      g_s=S_m*g₀+(1−
      
      S_m)*g.

17. A method for producing a gain-smoothed codevector during decoding of an encoded signal from a set of signal encoding parameters, said signal containing stationary background noise and said method comprising:
- finding a codevector in relation to at least one first signal encoding parameter of said set;
  
  calculating at least one factor representative of stationary background noise in the signal in response to at least one second signal encoding parameter of said set;
  
  calculating a smoothing gain using a non linear operation based on said noise representative factor; and
  
  amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

18. A method for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said method comprising:
- finding a codevector in relation to at least one first wideband signal encoding parameter of said set;
  
  calculating a factor representative of voicing in the wideband signal in response to at least one second wideband signal encoding parameter of said set;
  
  calculating a smoothing gain using a non linear operation based on said voicing representative factor; and
  
  amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

19. A method for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said method comprising:
- finding a codevector in relation to at least one first wideband signal encoding parameter of said set;
  
  calculating a factor representative of stability of said wideband signal in response to at least one second wideband signal encoding parameter of said set;
  
  calculating a smoothing gain using a non linear operation based on said stability representative factor; and
  
  amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

20. A device for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said device comprising:
- a codevector finder supplied with at least one first wideband signal encoding parameter of said set, and delivering a codevector found in relation to said at least one first wideband signal encoding parameter;
  
  a voicing factor calculator supplied with at least one second wideband signal encoding parameter of said set, and delivering a first factor representative of voicing in the wideband signal in response to said at least one second wideband signal encoding parameter;
  
  a stability factor calculator supplied with at least one third wideband signal encoding parameter of said set, and delivering a second factor representative of stability of said wideband signal in response to said at least one third wideband signal encoding parameter;
  
  a smoothing gain calculator supplied with the first and second factors, and delivering a smoothing gain based on said first and second factors;
  
  and an amplifier supplied with both the found codevector and the smoothing gain, and amplifying said found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

21. A device for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said device comprising:
- means for finding a codevector in relation to at least one first wideband signal encoding parameter of said set;
  
  means for calculating a first factor representative of voicing in the wideband signal in response to at least one second wideband signal encoding parameter of said set;
  
  means for calculating a second factor representative of stability of said wideband signal in response to at least one third wideband signal encoding parameter of said set;
  
  means for calculating a smoothing gain based on said first and second factors; and
  
  means for amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.
- View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100)
- - 22. A gain-smoothed codevector producing device as claimed in claim 21, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      the smoothing gain calculating means comprises means for calculating the smoothing gain also in relation to an innovative codebook gain forming a fourth wideband signal encoding parameter of said set.
  - 23. A gain-smoothed codevector producing device as claimed in claim 21, wherein:
    - the means for finding a codevector comprises means for finding a codevector in a codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one first wideband signal encoding parameter comprises an innovative codebook index.
  - 24. A gain-smoothed codevector producing device as claimed in claim 21, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one second wideband signal encoding parameter comprises the following parameters;
      
      a pitch gain computed during encoding of the wideband signal;
      
      a pitch delay computed during encoding of the wideband signal;
      
      an index j of a low-pass filter selected during encoding of the wideband signal and applied to a pitch codevector computed during encoding of the wideband signal; and
      
      an innovative codebook index computed during encoding of the wideband signal.
  - 25. A gain-smoothed codevector producing device as claimed in claim 21, wherein said at least one third wideband signal encoding parameter comprises coefficients of a linear prediction filter calculated during encoding of the wideband signal.
  - 26. A gain-smoothed codevector producing device as claimed in claim 21, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to an index k of said innovative codebook, said index k forming said at least one first wideband signal encoding parameter; and
      
      the means for calculating a first factor comprises means for computing a voicing factor rv by means of the following relation;
      
      rv=(Ev−
      
      Ec)/(Ev+Ec)where;
      
      Ev is the energy of a scaled adaptive codevector bvT;
      
      Ec is the energy of a scaled innovative codevector gck;
      
      b is a pitch gain computed during encoding of the wideband signal;
      
      T is a pitch delay computed during encoding of the wideband signal;
      
      vT is an adaptive codebook vector at pitch delay T;
      
      g is an innovative codebook gain computed during encoding of the wideband signal;
      
      k is an index of the innovative codebook computed during encoding of the wideband signal; and
      
      ck is the innovative codevector of said innovative codebook at index k.
  - 27. A gain-smoothed codevector producing device as claimed in claim 26, wherein the voicing factor rv has a value located between −
    - 1 and 1, wherein value 1 corresponds to a pure voiced signal and value −
      
      1 corresponds to a pure unvoiced signals.
  - 28. A gain-smoothed codevector producing device as claimed in claim 27, wherein the means for calculating a smoothing gain comprises means for computing a factor λ
    - using the following relation;
      
      λ
      
      =0.5(1−
      
      rv).
  - 29. A gain-smoothed codevector producing device as claimed in claim 28, wherein a factor, λ
    - =0 indicates a pure voiced signal and a factor λ
      
      =1 indicates a pure unvoiced signal.
  - 30. A gain-smoothed codevector producing device as claimed in claim 21, wherein the means for calculating a second factor comprises means for determining a distance measure giving a similarity between adjacent, successive linear prediction filters computed during encoding of the wideband signal.
  - 31. A gain-smoothed codevector producing device as claimed in claim 30, wherein:
    - the wideband signal is sampled prior to encoding, and is processed by frames during encoding and decoding; and
      
      the means for determining a distance measure comprises means for calculating an Imimitance Spectral Pair distance measure between the Immitance Spectral Pairs in a present frame n of the wideband signal and the Immitance Spectral Pairs of a past frame n−
      
      1 of the wideband signal through the following relation;
      
      $D_{s} = \sum_{i = 1}^{p - 1} {({isp}_{i}^{(n)} - {ispSUBi}^{(n - 1)})}^{2}$ where p is the order of the linear prediction filters.
  - 32. A gain-smoothed codevector producing device as claimed in claim 31, wherein the means for calculating a second factor comprises means for mapping the Immitance Spectral Pair distance measure D_sto said second factor θ
    - through the following relation;
      
      θ
      
      =1.25−
      
      D_s/400000.0bounded by 0≦
      
      θ
      
      ≦
      
      1.
  - 33. A gain-smoothed codevector producing device as claimed in claim 21, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor Sm based on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      .
  - 34. A gain-smoothed codevector producing device as claimed in claim 33, wherein the factor S_mhas a value approaching 1 for an unvoiced and stable wideband signal, and a value approaching 0 for a pure voiced wideband signal or an unstable wideband signal.
  - 35. A gain-smoothed codevector producing device as claimed in claim 21, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter;
      
      the wideband signal is sampled prior to encoding, and is processed by frames and subframes during encoding and decoding; and
      
      the means for calculating a smoothing gain comprises means for computing an initial modified gain g0, said initial modified gain computing means comprising means for comparing an innovative codebook gain g computed during encoding of the wideband signal to a threshold given by the initial modified gain from the past subframe g−
      
      1 as follows;
      
      if g <
      
      g −
      
      1 then g0 = g ×
      
      1.19 bounded by g ≦
      
      g −
      
      1 and if g ≧
      
      g −
      
      1 then g0 = g/1.19 bounded by g0 ≧
      
      g −
      
      1.
  - 36. A gain-smoothed codevector producing method as claimed in claim 35, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      , andmeans for determining said smoothing gain through the following relation;
      
      g_s=S_m*g₀+(1−
      
      S_m)*g.
  - 37. A cellular communication system for servicing a large geographical area divided into a plurality of cells, comprising:
    - mobile transmitter/receiver units;
      
      cellular base stations respectively situated in said cells;
      
      means for controlling communication between the cellular base stations;
      
      a bidirectional wireless communication sub-system between each mobile unit situated in one cell and the cellular base station of said one cell, said bidirectional wireless communication sub-system comprising in both the mobile unit and the cellular base station (a) a transmitter including a decoder for encoding a wideband signal and means for transmitting the encoded wideband signal, and (b) a receiver including means for receiving a transmitted encoded wideband signal and a decoder for decoding the received encoded wideband signal;
      
      wherein said decoder comprises means responsive to a set of wideband signal encoding parameters for decoding the received encoded wideband signal, and wherein said wideband signal decoding means comprises a device as recited in claim 21, for producing a gain-smoothed codevector during decoding of the encoded wideband signal from said set of wideband signal encoding parameters.
  - 38. The cellular communication system of claim 37, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      the smoothing gain calculating means comprises means for calculating the smoothing gain also in relation to an innovative codebook gain forming a fourth wideband signal encoding parameter of said set.
  - 39. The cellular communication system of claim 37, wherein:
    - the means for finding a codevector comprises means for finding a codevector in a codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one first wideband signal encoding parameter comprises an innovative codebook index.
  - 40. The cellular communication system of claim 37, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one second wideband signal encoding parameter comprises the following parameters;
      
      a pitch gain computed during encoding of the wideband signal;
      
      a pitch delay computed during encoding of the wideband signal;
      
      an index j of a low-pass filter selected during encoding of the wideband signal and applied to a pitch codevector computed during encoding of the wideband signal; and
      
      an innovative codebook index computed during encoding of the wideband signal.
  - 41. The cellular communication system of claim 37, wherein said at least one third wideband signal encoding parameter comprises coefficients of a linear prediction filter calculated during encoding of the wideband signal.
  - 42. The cellular communication system of claim 37, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to an index k of said innovative codebook, said index k forming said at least one first wideband signal encoding parameter; and
      
      the means for calculating a first factor comprises means for computing a voicing factor rv by means of the following relation;
      
      rv=(Ev−
      
      Ec)/(Ev+Ec)where;
      
      Ev is the energy of a scaled adaptive codevector bvT;
      
      Ec is the energy of a scaled innovative codevector gck;
      
      b is a pitch gain computed during encoding of the wideband signal;
      
      T is a pitch delay computed during encoding of the wideband signal;
      
      vT is an adaptive codebook vector at pitch delay T;
      
      g is an innovative codebook gain computed during encoding of the wideband signal;
      
      k is an index of the innovative codebook computed during encoding of the wideband signal; and
      
      ck is the innovative codevector of said innovative codebook at index k.
  - 43. The cellular communication system of claim 42, wherein the voicing factor rv has a value located between −
    - 1 and 1, wherein value 1 corresponds to a pure voiced signal and value −
      
      1 corresponds to a pure unvoiced signals.
  - 44. The cellular communication system of claim 43, wherein the means for calculating a smoothing gain comprises means for computing a factor λ
    - using the following relation;
      
      λ
      
      =0.5(1−
      
      rv).
  - 45. The cellular communication system of claim 44, wherein a factor λ
    - =0 indicates a pure voiced signal and a factor λ
      
      =1 indicates a pure unvoiced signal.
  - 46. The cellular communication system of claim 37, wherein the means for calculating a second factor comprises means for determining a distance measure giving a similarity between adjacent, successive linear prediction filters computed during encoding of the wideband signal.
  - 47. The cellular communication system of claim 46, wherein:
    - the wideband signal is sampled prior to encoding, and is processed by. frames during encoding and decoding; and
      
      the means for determining a distance measure comprises means for calculating an Immitance Spectral Pair distance measure between the Immitance Spectral Pairs in a present frame n of the wideband signal and the Immitance Spectral Pairs of a past frame n−
      
      1 of the wideband signal through the following relation;
      
      $D_{s} = \sum_{i = 1}^{p - 1} {({isp}_{i}^{(n)} - {ispSUBi}^{(n - 1)})}^{2}$ where p is the order of the linear prediction filters.
  - 48. The cellular Communication system of claim 47, wherein the means for calculating a second factor comprises means for mapping the Immitance Spectral Pair distance measure D_sto said second factor θ
    - through the following relation;
      
      θ
      
      =1.25−
      
      D_s/400000.0bounded by 0≦
      
      θ
      
      ≦
      
      1.
  - 49. The cellular communication system of claim 37, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      .
  - 50. The cellular communication system of claim 49, wherein the factor S_mhas a value approaching 1 for an unvoiced and stable wideband signal, and a value approaching 0 for a pure voiced wideband signal or an unstable wideband signal.
  - 51. The cellular communication system of claim 37, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter;
      
      the wideband signal is sampled prior to encoding, and is processed by frames and subframes during encoding and decoding; and
      
      the means for calculating a smoothing gain comprises means for computing an initial modified gain g0, said initial modified gain computing means comprising means for comparing an innovative codebook gain g computed during encoding of the wideband signal to a threshold given by the initial modified gain from the past subframe g−
      
      1 as follows;
      
      if g <
      
      g −
      
      1 then g0 = g ×
      
      1.19 bounded by g0 ≦
      
      g −
      
      1 and if g ≧
      
      g −
      
      1 then g0 = g/1.19 bounded by g0 ≧
      
      g −
      
      1.
  - 52. The cellular communication system of claim 51, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      , andmeans for determining said smoothing gain through the following relation;
      
      g_s=S_m*g₀+(1−
      
      S_m)*g.
  - 53. A cellular network element comprising (a) a transmitter including an encoder for encoding a wideband signal and means for transmitting the encoded wideband signal, and (b) a receiver including means for receiving a transmitted encoded wideband signal and a decoder for decoding the received encoded wideband signal;
    - wherein said decoder comprises means responsive to a set of wideband signal encoding parameters for decoding the received encoded wideband signal, and wherein said wideband signal decoding means comprises a device as recited in claim 21, for producing a gain-smoothed codevector during decoding of the encoded wideband signal from said set of wideband signal encoding parameters.
  - 54. A cellular network element as claimed in claim 53, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      the smoothing gain calculating means comprises means for calculating the smoothing gain also in relation to an innovative codebook gain forming a fourth wideband signal encoding parameter of said set.
  - 55. A cellular network element as claimed in claim 53, wherein:
    - the means for finding a codevector comprises means for finding a codevector in a codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one first wideband signal encoding parameter comprises an innovative codebook index.
  - 56. A cellular network element as claimed in claim 53, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one second wideband signal encoding parameter comprises the following parameters;
      
      a pitch gain computed during encoding of the wideband signal;
      
      a pitch delay computed during encoding of the wideband signal;
      
      an index j of a low-pass filter selected during encoding of the wideband signal and applied to a pitch codevector computed during encoding of the wideband signal; and
      
      an innovative codebook index computed during encoding of the wideband signal.
  - 57. A cellular network element as claimed in claim 53, wherein said at least one third wideband signal encoding parameter comprises coefficients of a linear prediction filter calculated during encoding of the wideband signal.
  - 58. A cellular network element as claimed in claim 53, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to an index k of said innovative codebook, said index k forming said at least one first wideband signal encoding parameter; and
      
      the means for calculating a first factor comprises means for computing a voicing factor rv by means of the following relation;
      
      rv(Ev−
      
      Ec)/(Ev+Ec)where;
      
      Ev is the energy of a scaled adaptive codevector bvT;
      
      Ec is the energy of a scaled innovative codevector gck;
      
      b is a pitch gain computed during encoding of the wideband signal;
      
      T is a pitch delay computed during encoding of the wideband signal;
      
      vT is an adaptive codebook vector at pitch delay T;
      
      g is an innovative codebook gain computed during encoding of the wideband signal;
      
      k is an index of the innovative codebook computed during encoding of the wideband signal; and
      
      ck is the innovative codevector of said innovative codebook at index k.
  - 59. A cellular network element as claimed in claim 58, wherein the voicing factor rv has a value located between −
    - 1 and 1, wherein value 1 corresponds to a pure voiced signal and value −
      
      1 corresponds to a pure unvoiced signals.
  - 60. A cellular network element as claimed in claim 59, wherein the means for calculating a smoothing gain comprises means for computing a factor λ
    - using the following relation;
      
      λ
      
      =0.5(1−
      
      rv).
  - 61. A cellular network element as claimed in claim 60, wherein a factor λ
    - =0 indicates a pure voiced signal and a factor λ
      
      =1 indicates a pure unvoiced signal.
  - 62. A cellular network element as claimed in claim 53, wherein the means for calculating a second factor comprises means for determining a distance measure giving a similarity between adjacent, successive linear prediction filters computed during encoding of the wideband signal.
  - 63. A cellular network element as claimed in claim 62, wherein:
    - the wideband signal is sampled prior to encoding, and is processed by frames during encoding and decoding; and
      
      the means for determining a distance measure comprises means for calculating an Immitance Spectral Pair distance measure between the Immitance Spectral Pairs in a present frame n of the wideband signal and the Immitance Spectral Pairs of a past frame n−
      
      1 of the wideband signal through the following relation;
      
      $D_{s} = \sum_{i = 1}^{p - 1} {({isp}_{i}^{(n)} - {ispSUBi}^{(n - 1)})}^{2}$ where p is the order of the linear prediction filters.
  - 64. A cellular network element as claimed in claim 63, wherein the means for calculating a second factor comprises means for mapping the Immitance Spectral Pair distance measure D_sto said second factor θ
    - through the following relation;
      
      θ
      
      =1.25−
      
      D_s/400000.0bounded by 0≦
      
      θ
      
      ≦
      
      1.
  - 65. A cellular network element as claimed in claim 53, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      .
  - 66. A cellular network element as claimed in claim 65, wherein the factor S_mhas a value approaching 1 for an unvoiced and stable wideband signal, and a value approaching 0 for a pure voiced wideband signal or an unstable wideband signal.
  - 67. A cellular network element as claimed in claim 53, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter;
      
      the wideband signal is sampled prior to encoding, and is processed by frames and subframes during encoding and decoding; and
      
      the means for calculating a smoothing gain comprises means for computing an initial modified gain g0, said initial modified gain computing means comprising means for comparing an innovative codebook gain g computed during encoding of the wideband signal to a threshold given by the initial modified gain from the past subframe g−
      
      1 as follows;
      
      if g <
      
      g −
      
      1 then g0 = g ×
      
      1.19 bounded by g0 ≦
      
      g −
      
      1 and if g ≧
      
      g −
      
      1 then g0 = g/1.19 bounded by g0 ≧
      
      g −
      
      1.
  - 68. A cellular network element as claimed in claim 67, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      , andmeans for determining said smoothing gain through the following relation;
      
      g_s=S_m*g₀+(1−
      
      S_m)*g.
  - 69. A cellular mobile transmitter/receiver unit comprising (a) a transmitter including an encoder for encoding a wideband signal and means for transmitting the encoded wideband signal, and (b) a receiver including means for receiving a transmitted encoded wideband signal and a decoder for decoding the received encoded wideband signal;
    - wherein said decoder comprises means responsive to a set of wideband signal encoding parameters for decoding the received encoded wideband signal, and wherein said wideband signal decoding means comprises a device as recited in claim 21, for producing a gain smoothed codevector during decoding of the encoded wideband signal from said set of wideband signal encoding parameters.
  - 70. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      the smoothing gain calculating means comprises means for calculating the smoothing gain also in relation to an innovative codebook gain forming a fourth wideband signal encoding parameter of said set.
  - 71. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein:
    - the means for finding a codevector comprises means for finding a codevector in a codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one first wideband signal encoding parameter comprises an innovative codebook index.
  - 72. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one second wideband signal encoding parameter comprises the following parameters;
      
      a pitch gain computed during encoding of the wideband signal;
      
      a pitch delay computed during encoding of the wideband signal;
      
      an index j of a low-pass filter selected during encoding of the wideband signal and applied to a pitch codevector computed during encoding of the wideband signal; and
      
      an innovative codebook index computed during encoding of the wideband signal.
  - 73. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein said at least one third wideband signal encoding parameter comprises coefficients of a linear prediction filter calculated during encoding of the wideband signal.
  - 74. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to an index k of said innovative codebook, said index k forming said at least one first wideband signal encoding parameter; and
      
      the means for calculating a first factor comprises means for computing a voicing factor rv by means of the following relation;
      
      rv=(Ev−
      
      Ec)/(Ev+Ec)where;
      
      Ev is the energy of a scaled adaptive codevector bvT;
      
      Ec is the energy of a scaled innovative codevector gck;
      
      b is a pitch gain computed during encoding of the wideband signal;
      
      T is a pitch delay computed during encoding of the wideband signal;
      
      vT is an adaptive codebook vector at pitch delay T;
      
      g is an innovative codebook gain computed during encoding of the wideband signal;
      
      k is an index of the innovative codebook computed during encoding of the wideband signal; and
      
      ck is the innovative codevector of said innovative codebook at index k.
  - 75. A cellular mobile transmitter/receiver unit as claimed in claim 74, wherein the voicing factor rv has a value located between −
    - 1 and 1, wherein value 1 corresponds to a pure voiced signal and value −
      
      1 corresponds to a pure unvoiced signals.
  - 76. A cellular mobile transmitter/receiver unit as claimed in claim 75, wherein the means for calculating a smoothing gain comprises means for computing a factor λ
    - using the following relation;
      
      λ
      
      =0.5(1−
      
      rv).
  - 77. A cellular mobile transmitter/receiver unit as claimed in claim 76, wherein a factor λ
    - =0 indicates a pure voiced signal and a factor λ
      
      =1 indicates a pure unvoiced signal.
  - 78. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein the means for calculating a second factor comprises means for determining a distance measure giving a similarity between adjacent, successive linear prediction filters computed during encoding of the wideband signal.
  - 79. A cellular mobile transmitter/receiver unit as claimed in claim 78, wherein:
    - the wideband signal is sampled prior to encoding, and is processed by frames during encoding and decoding; and
      
      the means for determining a distance measure comprises means for calculating an Immitance Spectral Pair distance measure between the Immitance Spectral Pairs in a present frame n of the wideband signal and the Immitance Spectral Pairs of a past frame n−
      
      1 of the wideband signal through the following relation;
      
      $D_{s} = \sum_{i = 1}^{p - 1} {({isp}_{i}^{(n)} - {ispSUBi}^{(n - 1)})}^{2}$ where p is the order of the linear prediction filters.
  - 80. A cellular mobile transmitter/receiver unit as claimed in claim 79, wherein the means for calculating a second factor comprises means for mapping the Immitance Spectral Pair distance measure Ds to said second factor θ
    - through the following relation;
      
      θ
      
      =1.25−
      
      D_s/400000.0bounded by 0≦
      
      θ
      
      ≦
      
      1.
  - 81. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      .
  - 82. A cellular mobile transmitter/receiver unit as claimed in claim 81, wherein the factor S_mhas a value approaching 1 for an unvoiced and stable wideband signal, and a value approaching 0 for a pure voiced wideband signal or an unstable wideband signal.
  - 83. A cellular mobile transmitter/receiver unit as claimed in claim 69, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter;
      
      the wideband signal is sampled prior to encoding, and is processed by frames and subframes during encoding and decoding; and
      
      the means for calculating a smoothing gain comprises means for computing an initial modified gain g0, said initial modified gain computing means comprising means for comparing an innovative codebook gain g computed during encoding of the wideband signal to a threshold given by the initial modified gain from the past subframe g−
      
      1 as follows;
      
      if g <
      
      g −
      
      1 then g0 = g ×
      
      1.19 bounded by g0 ≦
      
      g −
      
      1 and if g ≧
      
      g −
      
      1 then g0 = g/1.19 bounded by g0 ≧
      
      g −
      
      1.
  - 84. A cellular mobile transmitter/receiver unit as claimed in claim 83, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor Sm based on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      , andmeans for determining said smoothing gain through the following relation;
      
      g_s=S_m*g₀+(1−
      
      S_m)*g.
  - 85. In a cellular communication system for servicing a large geographical area divided into a plurality of cells, comprising:
    - mobile transmitter/receiver units;
      
      cellular base stations respectively situated in said cells; and
      
      means for controlling communication between the cellular base stations;
      
      a bidirectional wireless communication sub-system between each mobile unit situated in one cell and the cellular base station of said one cell, said bidirectional wireless communication sub-system comprising in both the mobile unit and the cellular base station (a) a transmitter including an encoder for encoding a wideband signal and means for transmitting the encoded wideband signal, and (b) a receiver including means for receiving a transmitted encoded wideband signal and a decoder for decoding the received encoded wideband signal;
      
      wherein said decoder comprises means responsive to a set of wideband signal encoding parameters for decoding the received encoded wideband signal, and wherein said wideband signal decoding means comprises a device as recited in claim 21, for producing a gain-smoothed codevector during decoding of the encoded wideband signal from said set of wideband signal encoding parameters.
  - 86. The bidirectional wireless communication sub-system of claim 85, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      the smoothing gain calculating means comprises means for calculating the smoothing gain also in relation to an innovative codebook gain forming a fourth wideband signal encoding parameter of said set.
  - 87. A bidirectional wireless communication sub-system as claimed in claim 85, wherein:
    - the means for finding a codevector comprises means for finding a codevector in a codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one first wideband signal encoding parameter comprises an innovative codebook index.
  - 88. A bidirectional wireless communication sub-system as claimed in claim 85, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter; and
      
      said at least one second wideband signal encoding parameter comprises the following parameters;
      
      a pitch gain computed during encoding of the wideband signal;
      
      a pitch delay computed during encoding of the wideband signal;
      
      an index j of a low-pass filter selected during encoding of the wideband signal and applied to a pitch codevector computed during encoding of the wideband signal; and
      
      an innovative codebook index computed during encoding of the wideband signal.
  - 89. A bidirectional wireless communication sub-system as claimed in claim 85, wherein said at least one third wideband signal encoding parameter comprises coefficients of a linear prediction filter calculated during encoding of the wideband signal.
  - 90. A bidirectional wireless communication sub-system as claimed in claim 85, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to an index k of said innovative codebook, said index k forming said at least one first wideband signal encoding parameter; and
      
      the means for calculating a first factor comprises means for computing a voicing factor rv by means of the following relation;
      
      rv=(Ev−
      
      Ec)/(Ev+Ec)where;
      
      Ev is the energy of a scaled adaptive codevector bvT;
      
      Ec is the energy of a scaled innovative codevector gck;
      
      b is a pitch gain computed during encoding of the wideband signal;
      
      T is a pitch delay computed during encoding of the wideband signal;
      
      vT is an adaptive codebook vector at pitch delay T;
      
      g is an innovative codebook gain computed during encoding of the wideband signal;
      
      k is an index of the innovative codebook computed during encoding of the wideband signal; and
      
      ck is the innovative codevector of said innovative codebook at index k.
  - 91. A bidirectional wireless communication sub-system as claimed in claim 90, wherein the voicing factor rv has a value located between −
    - 1 and 1, wherein value 1 corresponds to a pure voiced signal and value −
      
      1 corresponds to a pure unvoiced signals.
  - 92. A bidirectional wireless communication sub-system as claimed in claim 91, wherein the means for calculating a smoothing gain comprises means for computing a factor λ
    - using the following relation;
      
      λ
      
      =0.5(1−
      
      rv).
  - 93. A bidirectional wireless communication sub-system as claimed in claim 92, wherein a factor λ
    - =0 indicates a pure voiced signal and a factor λ
      
      =1 indicates a pure unvoiced signal.
  - 94. A bidirectional wireless communication sub-system as claimed in claim 85, wherein the means for calculating a second factor comprises means for determining a distance measure giving a similarity between adjacent, successive linear prediction filters computed during encoding of the wideband signal.
  - 95. A bidirectional wireless communication sub-system as claimed in claim 94, wherein:
    - the wideband signal is sampled prior to encoding, and is processed by frames during encoding and decoding; and
      
      the means for determining a distance measure comprises means for calculating an Immitance Spectral Pair distance measure between the Immitance Spectral Pairs in a present frame n of the wideband signal and the Immitance Spectral Pairs of a past frame n−
      
      1 of the wideband signal through the following relation;
      
      $D_{s} = \sum_{i = 1}^{p - 1} {({isp}_{i}^{(n)} - {ispSUBi}^{(n - 1)})}^{2}$ where p is the order of the linear prediction filters.
  - 96. A bidirectional wireless communication sub-system as claimed in claim 95, wherein the means for calculating a second factor comprises means for mapping the Immitance Spectral Pair distance measure Ds to said second factor θ
    - through the following relation;
      
      θ
      
      =1.25−
      
      D_s/400000.0bounded by 0≦
      
      θ
      
      ≦
      
      1.
  - 97. A bidirectional wireless communication sub-system as claimed in claim 85, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor S_mbased on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      .
  - 98. A bidirectional wireless communication sub-system as claimed in claim 97, wherein the factor Sm has a value approaching 1 for an unvoiced and stable wideband signal, and a value approaching 0 for a pure voiced wideband signal or an unstable wideband signal.
  - 99. A bidirectional wireless communication sub-system as claimed in claim 85, wherein:
    - the means for finding a codevector comprises means for finding an innovative codevector in an innovative codebook in relation to said at least one first wideband signal encoding parameter;
      
      the wideband signal is sampled prior to encoding, and is processed by frames and subframes during encoding and decoding; and
      
      the means for calculating a smoothing gain comprises means for computing an initial modified gain g0, said initial modified gain computing means comprising means for comparing an innovative codebook gain g computed during encoding of the wideband signal to a threshold given by the initial modified gain from the past subframe g−
      
      1 as follows;
      
      if g <
      
      g −
      
      1 then g0 = g ×
      
      1.19 bounded by g ≦
      
      g −
      
      1 and if g ≧
      
      g −
      
      1 then g0 = g/1.19 bounded by g0 ≧
      
      g −
      
      1.
  - 100. A bidirectional wireless communication sub-system as claimed in claim 99, wherein the means for calculating a smoothing gain comprises means for calculating a gain smoothing factor Sm based on both the first λ
    - and second θ
      
      factors through the following relation;
      
      S_m=λ
      
      θ
      
      , andmeans for determining said smoothing gain through the following relation;
      
      g_s=S_m*g₀+(1−
      
      S_m)*g.

101. A device for producing a gain-smoothed codevector during decoding of an encoded signal from a set of signal encoding parameters, said signal containing stationary background noise and said device comprising:
- means for finding a codevector in relation to at least one first signal encoding parameter of said set;
  
  means for calculating at least one factor representative of stationary background noise in the signal in response to at least one second wideband signal encoding parameter of said set;
  
  means for calculating a smoothing gain using a non linear operation based on said noise representative factor; and
  
  means for amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

102. A device for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said device comprising:
- means for finding a codevector in relation to at least one first wideband signal encoding parameter of said set;
  
  means for calculating a factor representative of voicing in the wideband signal in response to at least one second wideband signal encoding parameter of said set;
  
  means for calculating a smoothing gain using a non linear operation based on said voicing representative factor; and
  
  means for amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

103. A device for producing a gain-smoothed codevector during decoding of an encoded wideband signal from a set of wideband signal encoding parameters, said device comprising:
- means for finding a codevector in relation to at least one first wideband signal encoding parameter of said set;
  
  means for calculating a factor representative of stability of said wideband signal in response to at least one second wideband signal encoding parameter of said set;
  
  means for calculating a smoothing gain using a non linear operation based on said stability representative factor; and
  
  means for amplifying the found codevector with said smoothing gain to thereby produce said gain-smoothed codevector.

Specification

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Litigation Data

Current Assignee
Saint Lawrence Communications LLC (Acacia Research Corporation)
Original Assignee
VoiceAge Corporation
Inventors
Lefebvre, Roch, Bessette, Bruno, Salami, Redwan
Primary Examiner(s)
Hudspeth, David
Assistant Examiner(s)
Sked, Matthew J

Application Number

US10/129,945
Time in Patent Office

2,307 Days
Field of Search

None
US Class Current

704/225
CPC Class Codes

G10L 19/083 the excitation function bei...

G10L 2019/0012 Smoothing of parameters of ...

Gain-smoothing in wideband speech and audio signal decoder

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6 Assignments

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Abstract

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103 Claims

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Gain-smoothing in wideband speech and audio signal decoder

First Claim

6 Assignments

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Litigations

0 Petitions

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Accused Products

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Abstract

99 Citations

103 Claims

Specification

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