US5195168A — Speech coder and method having spectral interpola…

Claim 1

Independent Claim 511 words

A method for reconstructing a signal that has been partitioned into successive time interval partitions, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, the method utilizing at least a codebook unit having at least a codebook memory, a synthesis unit having at least a first synthesis filter, a combiner, and a perceptual weighting unit having at least a first perceptual weighting filter, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the method comprising the steps of: (1A) utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter; (1B) utilizing the at least first synthesis filter to obtain the corresponding impulse response representation, and interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters for desired subpartitions; such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (1C) utilizing the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition to select the corresponding set of optimal excitation codevectors from the at least first codebook memory, further implementing the following steps for each desired input reference signal vector: (1C1) providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (1C2) inputting the particular excitation codevector into the corresponding interpolated synthesis filter to produce the synthesized signal vector; (1C3) subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (1C4) inputting the reconstruction error vector into the corresponding interpolated perceptual weighting unit to determine a corresponding perceptually weighted squared error; (1C5) determining and storing index of codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (1C6) repeating the steps (1C1), (1C2), (1C3), (1C4), and (1C5) for every excitation codevector in the codebook memory and implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (D) successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 2

Independent Claim 511 words

A method for reconstructing a signal that has been partitioned into successive time interval partitions, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, the method utilizing at least a codebook unit having at least a codebook memory, a synthesis unit having at least a first synthesis filter, a combiner, and a perceptual weighting unit having at least a first perceptual weighting filter, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the method comprising the steps of: (1A) utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter; (1B) utilizing the at least first synthesis filter to obtain the corresponding impulse response representation, and interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters for desired subpartitions; such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (1C) utilizing the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition to select the corresponding set of optimal excitation codevectors from the at least first codebook memory, further implementing the following steps for each desired input reference signal vector: (1C1) providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (1C2) inputting the particular excitation codevector into the corresponding interpolated synthesis filter to produce the synthesized signal vector; (1C3) subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (1C4) inputting the reconstruction error vector into the corresponding interpolated perceptual weighting unit to determine a corresponding perceptually weighted squared error; (1C5) determining and storing index of codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (1C6) repeating the steps (1C1), (1C2), (1C3), (1C4), and (1C5) for every excitation codevector in the codebook memory and implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (D) successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 3

Dependent Claim 12 words

The method of claim 1, wherein the signal is a speech waveform.

Claim 4

Dependent Claim 24 words

The method of claim 1, wherein the at least first synthesis filter is at least a first time-varying linear predictive coding synthesis filter (LPC-SF).

Claim 5

Dependent Claim 52 words

The method of claim 3, wherein the at least first LPC-SF has a transfer function substantially of a form: ##EQU22## where a i 's, for i=1,2, . . . , p represent a set of estimated prediction coefficients obtained by analyzing the corresponding time signal partition and p represents a predictor order.

Claim 6

Dependent Claim 220 words

The method of claim 4, wherein LPC-SFs (linear predictive coding synthesis filters) of an adjacent time signal partition and of a time partition immediately thereafter are substantially of a form: ##EQU23## where a i .sup.(j) 's, for i=1, 2, 3, . . . , p and j=1, 2 represent a set of prediction coefficients in an adjacent time signal partition when j=1 and of a current time signal partition immediately thereafter when j=2, respectively, p represents a predictor order such that an impulse response for the transfer function H.sup.(j) (z) is substantially of a form ##EQU24## where ∂(n) is a unit sample function, and such that the impulse response of the at least first synthesis filter at an m-th subpartition of a current time partition obtained through linear interpolation of h.sup.(1) (n) and h.sup.(2) (n) respectively, denoted below as h m (n), is substantially of a form: h.sub.m (n)=α.sub.m h.sup.(1) (n)+β.sub.m h.sup.(2) (n), where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition, thereby providing a transfer function of the interpolated synthesis filter substantially of a form: ##EQU25## wherein the perceptual weighting filter at the m-th subpartition of a current time interval signal partition has a transfer function of a form: ##EQU26## where γ is typically selected to be substantially 0.8.

Claim 7

Dependent Claim 78 words

The method of claim 5, wherein the interpolated synthesis filter is approximated by an all pole filter whose parameters are utilized in the LPC synthesis filter and in the perceptual weighting filter for interpolating subpartitions, wherein the all pole filter parameters are obtained utilizing the steps of: truncating interpolated impulse samples: estimating a first p+1 autocorrelation coefficients using the truncated interpolated impulse response samples; and converting the autocorrelation coefficients to direct form prediction coefficients using a recursion algorithm.

Claim 8

Dependent Claim 66 words

The method of claim 6, wherein the estimated autocorrelation coefficients at the m-th subpartition can be expressed as: ##EQU27## for k=0,1, . . . , p and the summation is over all available partition impulse responses, such that ##EQU28## are autocorrelation coefficients of uninterpolated impulse response of the adjacent and current partitions, and ##EQU29## and i,j=1,2 where i≠j, are cross-correlation coefficients between the uninterpolated impulse responses.

Claim 9

Dependent Claim 14 words

The method of claim 1, wherein the excitation code vectors are stored in memory.

Claim 10

Dependent Claim 36 words

The method of claim 1, wherein the perceptual weighting unit includes at least a first perceptual weighting filter having a transfer function substantially of a form: ##EQU30## where γ is typically selected to be substantially 0.8.

Claim 11

Dependent Claim 45 words

The method of claim 1, wherein determining an optimal excitation codevector from the codebook memory for each input reference vector includes signal processing every excitation codevector in the codebook memory for each input reference vector, then determining the optimal excitation codevector of those codevectors processed.

Claim 12

Dependent Claim 132 words

The method of claim 1, wherein the fast codebook search method further includes utilizing a simplified method to obtain the perceptually weighted squared error between an input signal vector and a related synthesized codevector utilizing an i-th excitation codevector, denoting this error by E i , such that: ##EQU31## where x represents an input target vector at a subpartition that is substantially equal to an input reference signal vector at a subpartition filtered by a corresponding interpolated weighting filter with a zero-input response of a corresponding interpolated weighted LPC-SF (linear predictive coding synthesis filter) subtracted from it, A i represents a dot product of the vector x and an i-th filtered codevector y i ,m at an m-th subpartition, and B i represents the squared norm of the vector y i ,m.

Claim 13

Dependent Claim 194 words

The method of claim 11, wherein the corresponding interpolated weighted LPC-SF has a transfer function of H m (z/γ), such that: ##EQU32## where for an m-th subpartition, γ is typically selected to be 0.8, and a i ,m, for i=1,2, . . . p, such that p is a predictor order, represent the parameters of corresponding interpolated LPC-SF, the impulse response of H m (z/γ), h wm (n), is substantially equal to: h.sub.wm (n)=γ.sup.n h.sub.m (n), and where h m (n) is an impulse response of corresponding LPC-SF, utilizing a fact that h m (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated LPC-SFs, h wm (n), at each interpolating subpartition, determined in a fast codebook search as a linear interpolation of two impulse responses of related previous and current uninterpolated weighted LPC-SFs: h.sub.wm (n)=α.sub.m h.sub.w.sup.(1) (n)+β.sub.m h.sub.w.sup.(2) (n), where h w .sup.(j) (n)=γ n h.sup.(j) (n) for j=1,2 are exponentially weighted uninterpolated impulse responses of the previous, when j=1, and the current, when j=2, LPC synthesis filters, and where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 14

Dependent Claim 162 words

The method of claim 12, wherein the filtered codevector y i ,m is determined as a convolution of the i-th excitation codevector c i with the corresponding weighted impulse response h wm (n), the convolution substantially of a form: y i ,m =F wm c i , where ##EQU33## and where k represents a dimension of a codevector, further utilizing the fact that h wm (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated weighted LPC-SFs, the filtered codevector y i ,m at each interpolating subpartition may be determined as linear interpolation of two codevectors filtered by the related previous and current uninterpolated weighted LPC-SFs: y.sub.i,m =α.sub.m y.sub.i.sup.(1) +β.sub.m y.sub.i.sup.(2), and where y i .sup.(j) =F w .sup.(j) c i for j=1,2 and where matrices F w .sup.(1) and F w .sup.(2) have a same format as the matrix F wm , but with different elements h w .sup.(1) (n) and h w .sup.(2) (n), respectively.

Claim 15

Dependent Claim 84 words

The method of claim 11, wherein the squared norm B i at each interpolating subpartition is a weighted sum of a squared norm of a filtered codevector y i .sup.(1), the squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, substantially of a form: B.sub.i =α.sub.m.sup.2 ||y.sub.i.sup.(1) ||.sup.2 +β.sub.m.sup.2 ||y.sub.i.sup.(2) ||.sup.2 +2α.sub.m β.sub.m <y.sub.i.sup.(1) ·y.sub.i.sup.(2) >, where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 16

Dependent Claim 66 words

The method of claim 11, wherein determination of the dot product A i for each interpolating subpartition comprises two steps: 16A) backward filtering such that z=F t wm x wherein ##EQU34## and where k represents a dimension of a codevector; and where t represents a transpose operator; and 16B) forming a dot product such that: A.sub.i =<z·c.sub.i >, where c i is the ith excitation codevector.

Claim 17

Dependent Claim 38 words

The method of claim 1, further including, after step 1C1, multiplying the particular excitation codevector by an excitation gain factor to provide correlation with an energy of the representative electrical signal for each representative input reference signal vector.

Claim 18

Independent Claim 521 words

A method for reconstructing a speech signal pattern in a digital speech coder, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, the method utilizing at least a codebook unit having at least a codebook memory, a gain adjuster where selected, a synthesis unit having at least a first synthesis filter, a combiner, and a perceptual weighting unit having at least a first perceptual weighting filter, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the method comprising the steps of: (17A) utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter; (17B) utilizing the at least first synthesis filter to obtain the corresponding impulse response representation, and interpolating the impulse responses of each adjacent time signal partition and of a time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters for desired subpartitions; such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (17C) utilizing the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition to select the corresponding set of optimal excitation codevectors from the at least first codebook memory, further implementing the following steps for each desired input reference signal vector: (17C1) providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (17C2) inputting the particular excitation codevector into the corresponding interpolated synthesis filter to produce the synthesized signal vector; (17C3) subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (17C4) inputting the reconstruction error vector into the corresponding interpolated perceptual weighting unit to determine a corresponding perceptually weighted squared error; (17C5) determining and storing index of codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (17C6) repeating the steps (17C1), (17C2), (17C3), (17C4), and (17C5), for every excitation codevector in the codebook memory and implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (D) successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 19

Independent Claim 521 words

A method for reconstructing a speech signal pattern in a digital speech coder, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, the method utilizing at least a codebook unit having at least a codebook memory, a gain adjuster where selected, a synthesis unit having at least a first synthesis filter, a combiner, and a perceptual weighting unit having at least a first perceptual weighting filter, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the method comprising the steps of: (17A) utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter; (17B) utilizing the at least first synthesis filter to obtain the corresponding impulse response representation, and interpolating the impulse responses of each adjacent time signal partition and of a time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters for desired subpartitions; such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (17C) utilizing the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition to select the corresponding set of optimal excitation codevectors from the at least first codebook memory, further implementing the following steps for each desired input reference signal vector: (17C1) providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (17C2) inputting the particular excitation codevector into the corresponding interpolated synthesis filter to produce the synthesized signal vector; (17C3) subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (17C4) inputting the reconstruction error vector into the corresponding interpolated perceptual weighting unit to determine a corresponding perceptually weighted squared error; (17C5) determining and storing index of codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (17C6) repeating the steps (17C1), (17C2), (17C3), (17C4), and (17C5), for every excitation codevector in the codebook memory and implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (D) successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 20

Dependent Claim 12 words

The method of claim 17, wherein the signal is a speech waveform.

Claim 21

Dependent Claim 24 words

The method of claim 17, wherein the at least first synthesis filter is at least a first time-varying linear predictive coding synthesis filter (LPC-SF).

Claim 22

Dependent Claim 52 words

The method of claim 19, wherein the at least first LPC-SF has a transfer function substantially of a form: ##EQU35## where a i 's, for i=1,2, . . . , p represent a set of estimated prediction coefficients obtained by analyzing the corresponding time signal partition and p represents a predictor order.

Claim 23

Dependent Claim 77 words

The method of claim 20, wherein the interpolated synthesis filter is approximated by an all pole filter whose parameters are utilized in the LPC synthesis filter and in the perceptual weighting filter for interpolating subpartitions, wherein the all pole filter parameters are obtained utilizing the steps of: truncating interpolated impulse samples; estimating a first p+1 autocorrelation coefficients using truncated interpolated impulse response samples; and converting the autocorrelation coefficients to direct form prediction coefficients using a recursion algorithm.

Claim 24

Dependent Claim 66 words

The method of claim 21, wherein the estimated autocorrelation coefficients at the m-th subpartition can be expressed as: ##EQU36## for k=0,1, . . . , p and the summation is over all available partition impulse responses, such that ##EQU37## are autocorrelation coefficients of uninterpolated impulse response of the adjacent and current partitions, and ##EQU38## and i,j=1,2 where i≠j, are cross-correlation coefficients between the uninterpolated impulse responses.

Claim 25

Dependent Claim 215 words

The method of claim 17, wherein the LPC-SFs of a adjacent time signal partition and of a time partition immediately thereafter are substantially of a form: ##EQU39## where a i .sup.(j) 's, for i=1, 2, 3, . . . , p and j=1,2 represent a set of prediction coefficients in an adjacent time signal partition when j=1 and of a current time signal partition immediately thereafter when j=2, respectively, p represents a predictor order such that an impulse response for the transfer function H.sup.(j) (z) is substantially of a form ##EQU40## where ∂(n) is a unit sample function, and such that the impulse response of the at least first synthesis filter at an m-th subpartition of a current time partition obtained through linear interpolation of h.sup.(1) (n) and h.sup.(2) (n) respectively, denoted below as h m (n), is substantially of a form: h.sub.m (n)=α.sub.m h.sup.(1) (n)+β.sub.m h.sup.(2) (n), where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition, thereby providing a transfer function of the interpolated synthesis filter substantially of a form: ##EQU41## wherein the perceptual weighting filter at the m-th subpartition of a current time interval signal partition has a transfer function of the form: ##EQU42## where γ is typically selected to be substantially 0.8.

Claim 26

Dependent Claim 14 words

The method of claim 17, wherein the excitation code vectors are stored in memory.

Claim 27

Dependent Claim 36 words

The method of claim 17, wherein the perceptual weighting unit includes at least a first perceptual weighting filter having a transfer function substantially of a form: ##EQU43## where γ is typically selected to be substantially 0.8.

Claim 28

Dependent Claim 45 words

The method of claim 17, wherein determining an optimal excitation codevector from the codebook memory for each input reference vector includes signal processing every excitation codevector in the codebook memory for each input reference vector, then determining the optimal excitation codevector of those codevectors processed.

Claim 29

Dependent Claim 127 words

The method of claim 17, wherein the fast codebook search method further includes utilizing a simplified method to obtain the perceptually weighted squared error between an input signal vector and a related synthesized codevector utilizing an i-th excitation codevector, denoting this error by E i , such that: ##EQU44## where x represents an input target vector at a subpartition that is substantially equal to an input reference signal vector at a subpartition filtered by a corresponding interpolated weighting filter with a zero-input response of a corresponding interpolated weighted LPC-SF subtracted from it, A i represents a dot product of the vector x and an i-th filtered codevector y i ,m at an m-th subpartition, and B i represents the squared norm of the vector y i ,m.

Claim 30

Dependent Claim 194 words

The method of claim 27, wherein the corresponding interpolated weighted LPC-SF has a transfer function of H m (z/γ), such that: ##EQU45## where for an m-th subpartition, γ is typically selected to be 0.8, and a i ,m, for i=1,2, . . . p, such that p is a predictor order, represent the parameters of corresponding interpolated LPC-SF, the impulse response of H m (z/γ), h wm (n), is substantially equal to: h.sub.wm (n)=γ.sup.n h.sub.m (n), and where h m (n) is an impulse response of corresponding LPC-SF, utilizing a fact that h m (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated LPC-SFs, h wm (n), at each interpolating subpartition, determined in a fast codebook search as a linear interpolation of two impulse responses of related previous and current uninterpolated weighted LPC-SFs: h.sub.wm (n)=α.sub.m h.sub.w.sup.(1) (n)+β.sub.m h.sub.w.sup.(2) (n), where h w .sup.(j) (n)=γ n h.sup.(j) (n) for j=1,2 are exponentially weighted uninterpolated impulse responses of the previous, when j=1, and the current, when j=2, LPC synthesis filters, and where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 31

Dependent Claim 162 words

The method of claim 27, wherein the filtered codevector y i ,m is determined as a convolution of the i-th excitation codevector c i with the corresponding weighted impulse response h wm (n), the convolution substantially of a form: y i ,m =F wm c i , where ##EQU46## and where k represents a dimension of a codevector, further utilizing the fact that h wm (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated weighted LPC-SFs, the filtered codevector y i ,m at each interpolating subpartition may be determined as linear interpolation of two codevectors filtered by the related previous and current uninterpolated weighted LPC-SFs: y.sub.i,m =α.sub.m y.sub.i.sup.(1) +β.sub.m y.sub.i.sup.(2), and where y i .sup.(j) =F w .sup.(j) c i for j=1,2 and where matrices F w .sup.(1) and F w .sup.(2) have a same format as the matrix F wm , but with different elements h w .sup.(1) (n) and h w .sup.(2) (n), respectively.

Claim 32

Dependent Claim 85 words

The method of claim 27, wherein the squared norm B i at each interpolating subpartition is a weighted sum of a squared norm of a filtered codevector y i .sup.(1), a squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, substantially being of a form: B.sub.i =α.sub.m.sup.2 ||y.sub.i.sup.(1) ||.sup.2 +β.sub.m.sup.2 ||y.sub.i.sup.(2) ||.sup.2 +2α.sub.m β.sub.m <y.sub.i.sup.(1) ·y.sub.i.sup.(2) >, where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 33

Dependent Claim 66 words

The method of claim 27, wherein determination of the dot product A i for each interpolating subpartition comprises two steps: 32A) backward filtering such that z=F t wm x wherein ##EQU47## and where k represents a dimension of a codevector; and where t represents a transpose operator; and 32B) forming a dot product such that: A.sub.i =<z·c.sub.i >, where c i is the ith excitation codevector.

Claim 34

Dependent Claim 38 words

The method of claim 17, further including, after step 17C1, multiplying the particular excitation codevector by an excitation gain factor to provide correlation with an energy of the representative electrical signal for each representative input reference signal vector.

Claim 35

Independent Claim 588 words

A device for reconstructing a signal, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the device comprising at least: (33A) a first synthesis unit, responsive to the at least first representative electrical signal for each representative input reference signal, for utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter and the impulse response of this synthesis filter, and for interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters to at least a first perceptual weighting unit for desired subpartitions such that the at least first perceptual weighting unit provides at least a first perceptually weighted squared error and such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (33B) a codebook unit, responsive to the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition, for selecting the corresponding set of optimal excitation codevectors from the at least first codebook memory for each desired input reference signal vector, further comprising at least: (33B1) a codebook memory, for providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (33B2) an interpolated synthesis filter having a transfer function, responsive to the particular excitation codevector for producing a synthesized signal vector; (33B3) a combiner, responsive to the synthesized signal vector and to the input reference signal vector related thereto, for subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (33B4) an interpolated perceptual weighting unit, responsive to the corresponding reconstruction error vector and to the interpolated synthesis filter transfer function, for determining a corresponding perceptually weighted squared error; (33B5) a selector, responsive to the corresponding perceptually weighted squared error for determining and storing an index of a codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (33B6) repetition means, responsive to the number of excitation codevectors in the codebook memory, for repeating the steps (33B1), (33B2), (33B3), (33B4), and (33B5) for every excitation codevector in the codebook memory and for implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (33C) codebook unit control means, responsive to the set of optimal excitation codevectors for successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 36

Independent Claim 588 words

A device for reconstructing a signal, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the device comprising at least: (33A) a first synthesis unit, responsive to the at least first representative electrical signal for each representative input reference signal, for utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter and the impulse response of this synthesis filter, and for interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters to at least a first perceptual weighting unit for desired subpartitions such that the at least first perceptual weighting unit provides at least a first perceptually weighted squared error and such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (33B) a codebook unit, responsive to the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition, for selecting the corresponding set of optimal excitation codevectors from the at least first codebook memory for each desired input reference signal vector, further comprising at least: (33B1) a codebook memory, for providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (33B2) an interpolated synthesis filter having a transfer function, responsive to the particular excitation codevector for producing a synthesized signal vector; (33B3) a combiner, responsive to the synthesized signal vector and to the input reference signal vector related thereto, for subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (33B4) an interpolated perceptual weighting unit, responsive to the corresponding reconstruction error vector and to the interpolated synthesis filter transfer function, for determining a corresponding perceptually weighted squared error; (33B5) a selector, responsive to the corresponding perceptually weighted squared error for determining and storing an index of a codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (33B6) repetition means, responsive to the number of excitation codevectors in the codebook memory, for repeating the steps (33B1), (33B2), (33B3), (33B4), and (33B5) for every excitation codevector in the codebook memory and for implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (33C) codebook unit control means, responsive to the set of optimal excitation codevectors for successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 37

Dependent Claim 12 words

The device of claim 33, wherein the signal is a speech waveform.

Claim 38

Dependent Claim 24 words

The device of claim 33, wherein the at least first synthesis filter is at least a first time-varying linear predictive coding synthesis filter (LPC-SF).

Claim 39

Dependent Claim 52 words

The device of claim 35, wherein the at least first LPC-SF has a transfer function substantially of a form: ##EQU48## where a i 's, for i=1,2, . . . , p represent a set of estimated prediction coefficients obtained by analyzing the corresponding time signal partition and p represents a predictor order.

Claim 40

Dependent Claim 215 words

The device of claim 33, wherein the LPC-SFs of a adjacent time signal partition and of a time partition immediately thereafter are substantially of a form: ##EQU49## where a i .sup.(j) 's, for i=1, 2, 3, . . . , p and j=1,2 represent a set of prediction coefficients in a adjacent time signal partition when j=1 and of a current time signal partition immediately thereafter when j=2, respectively, p represents a predictor order such that an impulse response for the transfer function H.sup.(j) (z) is substantially of a form ##EQU50## where ∂(n) is a unit sample function, and such that the impulse response of the at least first synthesis filter at an m-th subpartition of a current time partition obtained through linear interpolation of h.sup.(1) (n) and h.sup.(2) (n) respectively, denoted below as h m (n), is substantially of a form: h.sub.m (n)=α.sub.m h.sup.(1) (n)+β.sub.m h.sup.(2) (n), where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition, thereby providing a transfer function of the interpolated synthesis filter substantially of a form: ##EQU51## wherein the perceptual weighting filter at the m-th subpartition of a current time interval signal partition has a transfer function of the form: ##EQU52## where γ is typically selected to be substantially 0.8.

Claim 41

Dependent Claim 95 words

The device of claim 37, wherein the interpolated synthesis filter is approximated by an all pole filter whose parameters are utilized in the LPC synthesis filter and in the perceptual weighting filter for interpolating subpartitions, wherein the all pole filter parameters are obtained utilizing at least: estimating means, responsive to interpolated impulse response samples, for truncating interpolated impulse samples and estimating a first p+1 autocorrelation coefficients using truncated interpolated impulse response samples; and converting means, responsive to the estimated autocorrelation coefficients, for converting the autocorrelation coefficients to direct form prediction coefficients using a recursion algorithm.

Claim 42

Dependent Claim 66 words

The device of claim 38, wherein the estimated autocorrelation coefficients at the m-th subpartition can be expressed as: ##EQU53## for k=0,1, . . . , p and the summation is over all available partition impulse responses, such that ##EQU54## are autocorrelation coefficients of uninterpolated impulse response of the adjacent and current partitions, and ##EQU55## and i,j=1,2 where i≠j, are cross-correlation coefficients between the uninterpolated impulse responses.

Claim 43

Dependent Claim 14 words

The device of claim 33, wherein the excitation code vectors are stored in memory.

Claim 44

Dependent Claim 36 words

The device of claim 33, wherein the perceptual weighting unit includes at least a first perceptual weighting filter having a transfer function substantially of a form: ##EQU56## where γ is typically selected to be substantially 0.8.

Claim 45

Dependent Claim 45 words

The device of claim 33, wherein determining an optimal excitation codevector from the codebook memory for each input reference vector includes signal processing every excitation codevector in the codebook memory for each input reference vector, then determining the optimal excitation codevector of those codevectors processed.

Claim 46

Dependent Claim 127 words

The device of claim 33, wherein the fast codebook search device further includes utilizing a simplified method to obtain the perceptually weighted squared error between an input signal vector and a related synthesized codevector utilizing an i-th excitation codevector, denoting this error by E i , such that: ##EQU57## where x represents an input target vector at a subpartition that is substantially equal to an input reference signal vector at a subpartition filtered by a corresponding interpolated weighting filter with a zero-input response of a corresponding interpolated weighted LPC-SF subtracted from it, A i represents a dot product of the vector x and an i-th filtered codevector y i ,m at an m-th subpartition, and B i represents the squared norm of the vector y i ,m.

Claim 47

Dependent Claim 194 words

The device of claim 43, wherein the corresponding interpolated weighted LPC-SF has a transfer function of H m (z/γ), such that: ##EQU58## where for an m-th subpartition, γ is typically selected to be 0.8, and a i ,m, for i=1,2, . . . p, such that p is a predictor order, represent the parameters of corresponding interpolated LPC-SF, the impulse response of H m (z/γ), h wm (n), is substantially equal to: h.sub.wm (n)=γ.sup.n h.sub.m (n), and where h m (n) is an impulse response of corresponding LPC-SF, utilizing a fact that h m (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated LPC-SFs, h wm (n), at each interpolating subpartition, determined in a fast codebook search as a linear interpolation of two impulse responses of related previous and current uninterpolated weighted LPC-SFs: h.sub.wm (n)=α.sub.m h.sub.w.sup.(1) (n)+β.sub.m h.sub.w.sup.(2) (n), where h w .sup.(j) (n)=γ n h.sup.(j) (n) for j=1,2 are exponentially weighted uninterpolated impulse responses of the previous, when j=1, and the current, when j=2, LPC synthesis filters, and where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 48

Dependent Claim 159 words

The device of claim 43, wherein the filtered codevector y i ,m is determined as a convolution of the i-th excitation codevector c i with the corresponding weighted impulse response h wm (n), the convolution being: y i ,m =F wm c i , where ##EQU59## and where k represents a dimension of a codevector, further utilizing the fact that h wm (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated weighted LPC-SFs, the filtered codevector y i ,m at each interpolating subpartition may be determined as linear interpolation of two codevectors filtered by the related previous and current uninterpolated weighted LPC-SFs: y.sub.i,m =α.sub.m y.sub.i.sup.(1) +β.sub.m y.sub.i.sup.(2), and where y i .sup.(j) =F w .sup.(j) c i for j=1,2 and where matrices F w .sup.(1) and F w .sup.(2) have a same format as the matrix F wm , but with different elements h w .sup.(1) (n) and h w .sup.(2) (n), respectively.

Claim 49

Dependent Claim 121 words

The device of claim 43, further including a second determiner, responsive to the squared norm of a filtered codevector y i .sup.(1), the squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, for determining the squared norm B i at each interpolating subpartition, a weighted sum of a squared norm of a filtered codevector y i .sup.(1), a squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, substantially being of a form: B.sub.i =α.sub.m.sup.2 ||y.sub.i.sup.(1) ||.sup.2 +β.sub.m.sup.2 ||y.sub.i.sup.(2) ||.sup.2 +2α.sub.m β.sub.m <y.sub.i.sup.(1) ·y.sub.i.sup.(2) >, where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 50

Dependent Claim 104 words

The device of claim 43, further including a first determiner for determination of the dot product A i for each interpolating subpartition comprising at least: 48A) a backward filter, responsive to an input vector x and to the matrix F wm , wherein ##EQU60## and where k represents a dimension of a codevector, for determining a vector z such that z=F.sup.t.sub.wm x; and where t represents a transpose operator; and 48B) a dot product determiner, responsive to the vector z and to the m-th excitation codevector, for forming a dot product such that: A.sub.i =<z·c.sub.i >, where c i is the ith excitation codevector.

Claim 51

Dependent Claim 50 words

The device of claim 33, further including a gain adjuster, responsive to the particular excitation codevector, for multiplying the particular excitation codevector (provided by the codebook memory) by an excitation gain factor to provide correlation with an energy of the representative electrical signal for each representative input reference signal vector.

Claim 52

Independent Claim 594 words

A device for reconstructing a speech signal in a digital speech coder, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the device comprising at least: (49A) a first synthesis unit, responsive to the at least first representative electrical signal for each representative input reference signal, for utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter and the impulse response of this synthesis filter, and for interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters to at least a first perceptual weighting unit for desired subpartitions such that the at least first perceptual weighting unit provides at least a first perceptually weighted squared error and such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (49B) a codebook unit, responsive to the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition, for selecting the corresponding set of optimal excitation codevectors from the at least first codebook memory for each desired input reference signal vector, further comprising at least: (49B1) a codebook memory, for providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (49B2) an interpolated synthesis filter having a transfer function, responsive to the particular excitation codevector for producing a synthesized signal vector; (49B3) a combiner, responsive to the synthesized signal vector and to the input reference signal vector related thereto, for subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (49B4) an interpolated perceptual weighting unit, responsive to the corresponding reconstruction error vector and to the interpolated synthesis filter transfer function, for determining a corresponding perceptually weighted squared error; (49B5) a selector, responsive to the corresponding perceptually weighted squared error for determining and storing an index of a codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (49B6) repetition means, responsive to the number of excitation codevectors in the codebook memory, for repeating the steps (49B1), (49B2), (49B3), (49B4), and (49B5) for every excitation codevector in the codebook memory and for implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (D) codebook unit control means, responsive to the set of optimal excitation codevectors for successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 53

Independent Claim 594 words

A device for reconstructing a speech signal in a digital speech coder, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the device comprising at least: (49A) a first synthesis unit, responsive to the at least first representative electrical signal for each representative input reference signal, for utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter and the impulse response of this synthesis filter, and for interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters to provide a corresponding set of interpolated perceptual weighting filters to at least a first perceptual weighting unit for desired subpartitions such that the at least first perceptual weighting unit provides at least a first perceptually weighted squared error and such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (49B) a codebook unit, responsive to the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition, for selecting the corresponding set of optimal excitation codevectors from the at least first codebook memory for each desired input reference signal vector, further comprising at least: (49B1) a codebook memory, for providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (49B2) an interpolated synthesis filter having a transfer function, responsive to the particular excitation codevector for producing a synthesized signal vector; (49B3) a combiner, responsive to the synthesized signal vector and to the input reference signal vector related thereto, for subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (49B4) an interpolated perceptual weighting unit, responsive to the corresponding reconstruction error vector and to the interpolated synthesis filter transfer function, for determining a corresponding perceptually weighted squared error; (49B5) a selector, responsive to the corresponding perceptually weighted squared error for determining and storing an index of a codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (49B6) repetition means, responsive to the number of excitation codevectors in the codebook memory, for repeating the steps (49B1), (49B2), (49B3), (49B4), and (49B5) for every excitation codevector in the codebook memory and for implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (D) codebook unit control means, responsive to the set of optimal excitation codevectors for successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 54

Dependent Claim 24 words

The device of claim 49, wherein the at least first synthesis filter is at least a first time-varying linear predictive coding synthesis filter (LPC-SF).

Claim 55

Dependent Claim 52 words

The device of claim 50, wherein the at least first LPC-SF has a transfer function substantially of a form: ##EQU61## where a i 's, for i=1,2, . . . , p represent a set of estimated prediction coefficients obtained by analyzing the corresponding time signal partition and p represents a predictor order.

Claim 56

Dependent Claim 216 words

The device of claim 50, wherein the LPC-SFs of an adjacent time signal partition and of a time partition immediately thereafter are substantially of a form: ##EQU62## where a i .sup.(j) 's, for i=1, 2, 3, . . . , p and j=1, 2 represent a set of prediction coefficients in an adjacent time signal partition when j=1 and of a current time signal partition immediately thereafter when j=2, respectively, p represents a predictor order such that an impulse response for the transfer function H.sup.(j) (z) is substantially of a form ##EQU63## where ∂(n) is a unit sample function, and such that the impulse response of the at least first synthesis filter at an m-th subpartition of a current time partition obtained through linear interpolation of h.sup.(1) (n) and h.sup.(2) (n) respectively, denoted below as h m (n), is substantially of a form: h.sub.m (n)=α.sub.m h.sup.(1) (n)+β.sub.m h.sup.(2) (n), where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition, thereby providing a transfer function of the interpolated synthesis filter substantially of a form: ##EQU64## wherein the perceptual weighting filter at the m-th subpartition of a current time interval signal partition has a transfer function of the form: ##EQU65## where γ is typically selected to be substantially 0.8.

Claim 57

Dependent Claim 95 words

The device of claim 52, wherein the interpolated synthesis filter is approximated by an all pole filter whose parameters are utilized in the LPC synthesis filter and in the perceptual weighting filter for interpolating subpartitions, wherein the all pole filter parameters are obtained utilizing at least: estimating means, responsive to interpolated impulse response samples, for truncating interpolated impulse samples and estimating a first p+1 autocorrelation coefficients using truncated interpolated impulse response samples; and converting means, responsive to the estimated autocorrelation coefficients, for converting the autocorrelation coefficients to direct form prediction coefficients using a recursion algorithm.

Claim 58

Dependent Claim 66 words

The device of claim 53, wherein the estimated autocorrelation coefficients at the m-th subpartition can be expressed as: ##EQU66## for k=0,1, . . . , p and the summation is over all available partition impulse responses, such that ##EQU67## are autocorrelation coefficients of uninterpolated impulse response of the adjacent and current partitions, and ##EQU68## and i,j=1,2 where i≠j, are cross-correlation coefficients between the uninterpolated impulse responses.

Claim 59

Dependent Claim 14 words

The device of claim 49, wherein the excitation code vectors are stored in memory.

Claim 60

Dependent Claim 36 words

The device of claim 49, wherein the perceptual weighting unit includes at least a first perceptual weighting filter having a transfer function substantially of a form: ##EQU69## where γ is typically selected to be substantially 0.8.

Claim 61

Dependent Claim 45 words

The device of claim 49, wherein determining an optimal excitation codevector from the codebook memory for each input reference vector includes signal processing every excitation codevector in the codebook memory for each input reference vector, then determining the optimal excitation codevector of those codevectors processed.

Claim 62

Dependent Claim 131 words

The device of claim 49, wherein the fast codebook search device further includes codebook unit means for utilizing a simplified method to obtain the perceptually weighted squared error between an input signal vector and a related synthesized codevector utilizing an i-th excitation codevector, denoting this error by E i , such that: ##EQU70## where x represents an input target vector at a subpartition that is substantially equal to an input reference signal vector at a subpartition filtered by a corresponding interpolated weighting filter with a zero-input response of a corresponding interpolated weighted LPC-SF subtracted from it, A i represents a dot product of the vector x and an i-th filtered codevector y i ,m at an m-th subpartition, and B i represents the squared norm of the vector y i ,m.

Claim 63

Dependent Claim 194 words

The device of claim 58, wherein the corresponding interpolated weighted LPC-SF has a transfer function of H m (z/γ), such that: ##EQU71## where for an m-th subpartition, γ is typically selected to be 0.8, and a i ,m, for i=1,2, . . . p, such that p is a predictor order, represent the parameters of corresponding interpolated LPC-SF, the impulse response of H m (z/γ), h wm (n), is substantially equal to: h.sub.wm (n)=γ.sup.n h.sub.m (n), and where h m (n) is an impulse response of corresponding LPC-SF, utilizing a fact that h m (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated LPC-SFs, h wm (n), at each interpolating subpartition, determined in a fast codebook search as a linear interpolation of two impulse responses of related previous and current uninterpolated weighted LPC-SFs: h.sub.wm (n)=α.sub.m h.sub.w.sup.(1) (n)+β.sub.m h.sub.w.sup.(2) (n), where h w .sup.(j) (n)=γ n h.sup.(j) (n) for j=1,2 are exponentially weighted uninterpolated impulse responses of the previous, when j=1, and the current, when j=2, LPC synthesis filters, and where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 64

Dependent Claim 162 words

The device of claim 58, wherein the filtered codevector y i ,m is determined as a convolution of the i-th excitation codevector c i with the corresponding weighted impulse response h wm (n), the convolution substantially of a form: y i ,m =F wm c i , where ##STR3## and where k represents a dimension of a codevector, further utilizing the fact that h wm (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated weighted LPC-SFs, the filtered codevector y i ,m at each interpolating subpartition may be determined as linear interpolation of two codevectors filtered by the related previous and current uninterpolated weighted LPC-SFs: y.sub.i,m =α.sub.m y.sub.i.sup.(1) +β.sub.m y.sub.i.sup.(2), and where y i .sup.(j) =F w .sup.(j) c i for j=1,2 and where matrices F w .sup.(1) and F w .sup.(2) have a same format as the matrix F wm , but with different elements h w .sup.(1) (n) and h w .sup.(2) (n), respectively.

Claim 65

Dependent Claim 122 words

The device of claim 58, further including a second determiner, responsive to the squared norm of a filtered codevector y i .sup.(1), the squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, for determining the squared norm B i at each interpolating subpartition, a weighted sum of a squared norm of a filtered codevector y i .sup.(1), the weighted squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, substantially being of a form: B.sub.i =α.sub.m.sup.2 ||y.sub.i.sup.(1) ||.sup.2 +β.sub.m.sup.2 ||y.sub.i.sup.(2) ||.sup.2 +2α.sub.m β.sub.m <y.sub.i.sup.(1) ·y.sub.i.sup.(2) >, where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 66

Dependent Claim 105 words

The device of claim 58, further including a first determiner for determination of the dot product A i for each interpolating subpartition comprising at least: 63A) a backward filter, responsive to an input vector x and to the matrix F wm wherein ##STR4## and where k represents a dimension of a codevector, for determining a vector z such that z=F t wm x; and where t represents a transpose operator; and 63B) a dot product determiner, responsive to the vector z and to the m-th excitation codevector, for forming a dot product such that: A.sub.i =<z·c.sub.i >, where c i is the ith excitation codevector.

Claim 67

Dependent Claim 50 words

The device of claim 49, further including a gain adjuster, responsive to the particular excitation codevector provided by the codebook memory, for multiplying the particular excitation codevector by an excitation gain factor to provide correlation with an energy of the representative electrical signal for each representative input reference signal vector.

Claim 68

Independent Claim 890 words

A system for reconstructing a speech signal in a digital speech coder, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the system comprising at least: (64A) a first synthesis unit, responsive to the at least first representative electrical signal for each representative input reference signal, for utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter and the impulse response of this synthesis filter, and having a first synthesis filter, the at least first synthesis filter being at least a first time-varying linear predictive coding synthesis filter (LPC-SF) wherein the at least first LPC-SF has a transfer function substantially of a form: ##EQU72## where a i 's, for i=1,2, . . . , p represent a set of estimated prediction coefficients obtained by analyzing the corresponding time signal partition and p represents a predictor order, responsive to the set of uninterpolated parameters, for obtaining the corresponding impulse response representation, and interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter, wherein the LPC-SFs of a adjacent time signal partition and of a time partition immediately thereafter are substantially of a form: ##EQU73## where a i .sup.(j) 's, for i=1, 2, 3, . . . , p and j=1, 2 represent a set of prediction coefficients in an adjacent time signal partition when j=1 and of a current time signal partition immediately thereafter when j=2, respectively, p represents a predictor order such that an impulse response for the transfer function H.sup.(j) (z) is substantially of a form ##EQU74## where ∂(n) is a unit sample function, and such that the impulse response of the at least first synthesis filter at an m-th subpartition of a current time partition obtained through linear interpolation of h.sup.(1) (n) and h.sup.(2) (n) respectively, denoted below as h m (n), is substantially of a form: h.sub.m (n)=α.sub.m h.sup.(1) (n)+β.sub.m h.sup.(2) (n), where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition, thereby providing a transfer function of an interpolated synthesis filter substantially of a form: ##EQU75## wherein the perceptual weighting filter at the m-th subpartition of a current time interval signal partition has a transfer function of the form: ##EQU76## where γ is typically selected to be substantially 0.8, to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters, to provide a corresponding set of interpolated perceptual weighting filters to at least a first perceptual weighting unit for desired subpartitions such that the at least first perceptual weighting unit provides at least a first perceptually weighted squared error and such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (64B) a codebook unit, responsive to the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition, for selecting the corresponding set of optimal excitation codevectors from the at least first codebook memory for each desired input reference signal vector, further comprising at least: (64B1) a first codebook memory, for providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (64B2) an interpolated synthesis filter having a transfer function, responsive to the particular excitation codevector for producing a synthesized signal vector; (64B3) a combiner, responsive to the synthesized signal vector and to the input reference signal vector related thereto, for subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (64B4) an interpolated perceptual weighting unit, responsive to the corresponding reconstruction error vector and to the interpolated synthesis filter transfer function, for determining a corresponding perceptually weighted squared error; (64B5) a selector, responsive to the corresponding perceptually weighted squared error for determining and storing an index of a codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (64B6) repetition means, responsive to the number of excitation codevectors in the codebook memory, for repeating the steps (64B1), (64B2), (64B3), (64B4), and (64B5) for every excitation codevector in the codebook memory and for implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (C) codebook unit control means, responsive to the set of optimal excitation codevectors for successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 69

Independent Claim 890 words

A system for reconstructing a speech signal in a digital speech coder, the signal being partitioned into successive time intervals, each time interval signal partition having a representative input reference signal with a set of vectors, and having at least a first representative electrical signal for each representative input reference signal of each time interval signal partition, for utilizing the electrical signals of the representative input reference signals to at least generate a related set of synthesized signal vectors for reconstructing the signal, the system comprising at least: (64A) a first synthesis unit, responsive to the at least first representative electrical signal for each representative input reference signal, for utilizing the at least first representative electrical signal for each representative input reference signal for a time signal partition to obtain a set of uninterpolated parameters for the at least first synthesis filter and the impulse response of this synthesis filter, and having a first synthesis filter, the at least first synthesis filter being at least a first time-varying linear predictive coding synthesis filter (LPC-SF) wherein the at least first LPC-SF has a transfer function substantially of a form: ##EQU72## where a i 's, for i=1,2, . . . , p represent a set of estimated prediction coefficients obtained by analyzing the corresponding time signal partition and p represents a predictor order, responsive to the set of uninterpolated parameters, for obtaining the corresponding impulse response representation, and interpolating the impulse responses of each adjacent time signal partition and of a current time signal partition immediately thereafter, wherein the LPC-SFs of a adjacent time signal partition and of a time partition immediately thereafter are substantially of a form: ##EQU73## where a i .sup.(j) 's, for i=1, 2, 3, . . . , p and j=1, 2 represent a set of prediction coefficients in an adjacent time signal partition when j=1 and of a current time signal partition immediately thereafter when j=2, respectively, p represents a predictor order such that an impulse response for the transfer function H.sup.(j) (z) is substantially of a form ##EQU74## where ∂(n) is a unit sample function, and such that the impulse response of the at least first synthesis filter at an m-th subpartition of a current time partition obtained through linear interpolation of h.sup.(1) (n) and h.sup.(2) (n) respectively, denoted below as h m (n), is substantially of a form: h.sub.m (n)=α.sub.m h.sup.(1) (n)+β.sub.m h.sup.(2) (n), where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition, thereby providing a transfer function of an interpolated synthesis filter substantially of a form: ##EQU75## wherein the perceptual weighting filter at the m-th subpartition of a current time interval signal partition has a transfer function of the form: ##EQU76## where γ is typically selected to be substantially 0.8, to provide a set of interpolated synthesis filters for desired subpartitions; and utilizing the interpolated synthesis filters, to provide a corresponding set of interpolated perceptual weighting filters to at least a first perceptual weighting unit for desired subpartitions such that the at least first perceptual weighting unit provides at least a first perceptually weighted squared error and such that smooth transitions of the synthesis filter and the perceptual weighting filter between each pair of adjacent partitions are obtained; (64B) a codebook unit, responsive to the set of input reference signal vectors, the related set of interpolated synthesis filters and the related set of interpolated perceptual weighting filters for the current time signal partition, for selecting the corresponding set of optimal excitation codevectors from the at least first codebook memory for each desired input reference signal vector, further comprising at least: (64B1) a first codebook memory, for providing a particular excitation codevector which is associated with a particular index from the at least first codebook memory, the codebook memory having a set of excitation codevectors stored therein responsive to the representative input vectors; (64B2) an interpolated synthesis filter having a transfer function, responsive to the particular excitation codevector for producing a synthesized signal vector; (64B3) a combiner, responsive to the synthesized signal vector and to the input reference signal vector related thereto, for subtracting the synthesized signal vector from the input reference signal vector related thereto to obtain a corresponding reconstruction error vector; (64B4) an interpolated perceptual weighting unit, responsive to the corresponding reconstruction error vector and to the interpolated synthesis filter transfer function, for determining a corresponding perceptually weighted squared error; (64B5) a selector, responsive to the corresponding perceptually weighted squared error for determining and storing an index of a codevector having the perceptually weighted squared error smaller than all other errors produced by other codevectors; (64B6) repetition means, responsive to the number of excitation codevectors in the codebook memory, for repeating the steps (64B1), (64B2), (64B3), (64B4), and (64B5) for every excitation codevector in the codebook memory and for implementing these steps utilizing a fast codebook search method, to determine an optimal excitation codevector for producing the minimum weighted squared error among all excitation codevectors for the related input reference signal vector; and (C) codebook unit control means, responsive to the set of optimal excitation codevectors for successively inputting the set of optimal excitation codevectors into the corresponding set of interpolated synthesis filters to produce the related set of synthesized signal vectors for the given input reference signal for reconstructing the input signal.

Claim 70

Dependent Claim 97 words

The system of claim 64, wherein the synthesis filter is approximated by an all pole synthesis filter that is utilized to provide parameters for interpolating subpartitions in the LPC-SF filter and in the perceptual weighting filter, wherein the all pole synthesis filter parameters are obtained utilizing at least: estimating means, responsive to interpolated impulse response samples, for truncating interpolated impulse samples and estimating a first p+1 autocorrelation coefficients using truncated interpolated impulse response samples; and converting means, responsive to the estimated autocorrelation coefficients, for converting the autocorrelation coefficients to direct form prediction coefficients using a recursion algorithm.

Claim 71

Dependent Claim 66 words

The system of claim 65, wherein the estimated autocorrelation coefficients at the m-th subpartition can be expressed as: ##EQU77## for k=0,1, . . . , p and the summation is over all available partition impulse responses, such that ##EQU78## are autocorrelation coefficients of uninterpolated impulse response of the adjacent and current partitions, and ##EQU79## and i,j=1,2 where i≠j, are cross-correlation coefficients between the uninterpolated impulse responses.

Claim 72

Dependent Claim 14 words

The system of claim 64, wherein the excitation code vectors are stored in memory.

Claim 73

Dependent Claim 36 words

The system of claim 64, wherein the perceptual weighting unit includes at least a first perceptual weighting filter having a transfer function substantially of a form: ##EQU80## where γ is typically selected to be substantially 0.8.

Claim 74

Dependent Claim 45 words

The system of claim 64, wherein determining an optimal excitation codevector from the codebook memory for each input reference vector includes signal processing every excitation codevector in the codebook memory for each input reference vector, then determining the optimal excitation codevector of those codevectors processed.

Claim 75

Dependent Claim 127 words

The system of claim 64, wherein the fast codebook search system further includes utilizing a simplified method to obtain the perceptually weighted squared error between an input signal vector and a related synthesized codevector utilizing an i-th excitation codevector, denoting this error by E i , such that: ##EQU81## where x represents an input target vector at a subpartition that is substantially equal to an input reference signal vector at a subpartition filtered by a corresponding interpolated weighting filter with a zero-input response of a corresponding interpolated weighted LPC-SF subtracted from it, A i represents a dot product of the vector x and an i-th filtered codevector y i ,m at an m-th subpartition, and B i represents the squared norm of the vector y i ,m.

Claim 76

Dependent Claim 194 words

The system of claim 70, wherein the corresponding interpolated weighted LPC-SF has a transfer function of H m (z/γ), such that: ##EQU82## where for an m-th subpartition, γ is typically selected to be 0.8, and a i ,m, for i=1,2, . . . p, such that p is a predictor order, represent the parameters of corresponding interpolated LPC-SF, the impulse response of H m (z/γ), h wm (n), is substantially equal to: h.sub.wm (n)=γ.sup.n h.sub.m (n), and where h m (n) is an impulse response of corresponding LPC-SF, utilizing a fact that h m (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated LPC-SFs, h wm (n), at each interpolating subpartition, determined in a fast codebook search as a linear interpolation of two impulse responses of related previous and current uninterpolated weighted LPC-SFs: h.sub.wm (n)=α.sub.m h.sub.w.sup.(1) (n)+β.sub.m h.sub.w.sup.(2) (n), where h w .sup.(j) (n)=γ n h.sup.(j) (n) for j=1,2 are exponentially weighted uninterpolated impulse responses of the previous, when j=1, and the current, when j=2, LPC synthesis filters, and where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 77

Dependent Claim 162 words

The system of claim 70, wherein the filtered codevector y i ,m is determined as a convolution of the i-th excitation codevector c i with the corresponding weighted impulse response h wm (n), the convolution substantially of a form: y i ,m =F wm c i , where ##STR5## and where k represents a dimension of a codevector, further utilizing the fact that h wm (n) is a linear interpolation of the impulse responses of related previous and current uninterpolated weighted LPC-SFs, the filtered codevector y i ,m at each interpolating subpartition may be determined as linear interpolation of two codevectors filtered by the related previous and current uninterpolated weighted LPC-SFs: y.sub.i,m =α.sub.m y.sub.i.sup.(1) +β.sub.m y.sub.i.sup.(2), and where y i .sup.(j) =F w .sup.(j) c i for j=1,2 and where matrices F w .sup.(1) and F w .sup.(2) have a same format as the matrix F wm , but with different elements h w .sup.(1) (n) and h w .sup.(2) (n), respectively.

Claim 78

Dependent Claim 120 words

The system of claim 70, further including a second determiner, responsive to the squared norm of a filtered codevector y i .sup.(1), the squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, for determining the squared norm B i at each interpolating subpartition, a weighted sum of a squared norm of a filtered codevector y i .sup.(1), the squared norm of the filtered codevector y i .sup.(2), and a dot product of those two filtered codevectors, substantially of a form: B.sub.i =α.sub.m.sup.2 ||y.sub.i.sup.(1) ||.sup.2 +β.sub.m.sup.2 ||y.sub.i.sup.(2) ||.sup.2 +2α.sub.m β.sub.m <y.sub.i.sup.(1) ·y.sub.i.sup.(2) >, where β m =1-α m and 0<α m <1, where a different α m is utilized for each subpartition.

Claim 79

Dependent Claim 106 words

The system of claim 70, further including a first determiner for determination of the dot product A i for each interpolating subpartition comprising at least: 75A) a backward filter, responsive to an input vector x and to the matrix F wm , wherein ##STR6## and where k represents a dimension of a codevector, for determining a vector z such that z=F t wm x; and where t represents a transpose operator; and 75B) a dot product determiner, responsive to the vector z and to the m-th excitation codevector, for forming a dot product such that: A.sub.i =<z·c.sub.i >, where c i is the ith excitation codevector.

Claim 80

Dependent Claim 50 words

The system of claim 64, further including a gain adjuster, responsive to the particular excitation codevector provided by the codebook memory, for multiplying the particular excitation codevector by an excitation gain factor to provide correlation with an energy of the representative electrical signal for each representative input reference signal vector.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1996-03-15	1996-09-14	1997-03-16	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2000-03-15	2000-09-14	2001-03-16	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2004-03-15	2004-09-14	2005-03-16	$7700.00	Window Closed / Lapsed

Speech coder and method having spectral interpolation and fast codebook search

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