US5327520A — Method of use of voice message coder/decoder

Claim 1

Independent Claim 132 words

A method of processing a sequence of input samples comprising gain adjusting each of a plurality of codevectors in a backward adaptive gain controller to produce corresponding gain-adjusted codevectors, each of said codevectors being identified by a corresponding index, filtering each of said gain-adjusted codevectors in a synthesis filter characterized by a plurality of filter parameters to generate candidate codevectors, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, comparing said sequence of input samples with each of said candidate codevectors to determine, for said sequence of input samples, a candidate codevector substantially approximating said sequence of input samples, and outputting (i) the index for the candidate codevector, and (ii) the parameters of said long term synthesis filter.

Claim 2

Independent Claim 132 words

A method of processing a sequence of input samples comprising gain adjusting each of a plurality of codevectors in a backward adaptive gain controller to produce corresponding gain-adjusted codevectors, each of said codevectors being identified by a corresponding index, filtering each of said gain-adjusted codevectors in a synthesis filter characterized by a plurality of filter parameters to generate candidate codevectors, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, comparing said sequence of input samples with each of said candidate codevectors to determine, for said sequence of input samples, a candidate codevector substantially approximating said sequence of input samples, and outputting (i) the index for the candidate codevector, and (ii) the parameters of said long term synthesis filter.

Claim 3

Dependent Claim 64 words

The method of claim 1 wherein said synthesis filter comprises a long-term filter component and a short-term filter component, each of said filter components being characterized by a respective plurality of filter parameters, and wherein adjusting the parameters of said synthesis filter comprises adjusting the parameters of each of said filter components based on a linear predictive analysis of said sequence of input samples.

Claim 4

Dependent Claim 108 words

The method of claim 2 wherein said sequence of input samples is a current sequence of input samples in a plurality of consecutive sequences of input samples, said plurality of sequences of input samples including at least one sequence of input samples preceding the current sequence of input samples, and said linear predictive analysis of said input samples comprises grouping the plurality of consecutive sequences of input samples into a frame of input samples, each of said sequences of input samples thereby comprising a sub-frame, determining a set of Nth order predictor coefficients corresponding to said frame of input samples wherein N is the number of predictor coefficients.

Claim 5

Dependent Claim 44 words

The method of claim 3, wherein said determining said set of Nth order predictor coefficients, comprises performing an autocorrelation analysis of said frame of input samples to generate a set of autocorrelation coefficients, and recursively forming said predictor coefficients based on said autocorrelation coefficients.

Claim 6

Dependent Claim 77 words

The method of claim 3, further comprising weighting said frame of input samples to form a weighted frame of input samples prior to determining said Nth order predictor coefficients, and wherein said determining said set of Nth order predictor coefficients, comprises performing an autocorrelation analysis of said weighted frame of input samples to generate an ordered set of autocorrelation coefficients, and performing a Levinson-Durbin recursion based on said autocorrelation coefficients to determine said set of predictor coefficients.

Claim 7

Dependent Claim 22 words

The method of claim 5, further comprising modifying said autocorrelation coefficients to reflect the addition of a small amount of white noise.

Claim 8

Dependent Claim 20 words

The method of claim 6, wherein said modifying comprises changing the first of said autocorrelation coefficients by a small factor.

Claim 9

Dependent Claim 28 words

The method of claim 7, further comprising the step of modifying the bandwidth of the set of predictor coefficients, thereby expanding the spectral peaks of said synthesis filter.

Claim 10

Dependent Claim 44 words

The method of claim 3, further comprising recursively converting said set of predictor coefficients into a set of reflection coefficients according to ##EQU25## where, k m is the m-th reflection coefficient and a i .sup.(m) is the i-th coefficient of the m-th order predictor.

Claim 11

Dependent Claim 69 words

The method of claim 9 wherein each of said frames comprises S sub-frames and said method further comprises weighting said frame of input samples, thereby forming weighted input samples, prior to determining said Nth order predictor coefficients, and determining predictor coefficients for each weighted sub-frame of input samples based on an interpolation of predictor coefficients determined for a current frame and the predictor coefficients for the immediately preceding frame.

Claim 12

Dependent Claim 88 words

The method of claim 10 wherein S=4, so that each of said frames comprises four sub-frames of input samples, said weighting is in accordance with a shaped weighting window function centered on the fourth of said sequences of input samples, and said interpolation is performed in accordance with ##EQU26## where k m and k m are the m-th quantized reflection coefficients of the previous frame and the current frame, respectively, and k m (j) is the interpolated m-th reflection coefficient for the j-th weighted sequence of input samples.

Claim 13

Dependent Claim 62 words

The method of claim 9, comprising the further step of quantizing said set of reflection coefficients by comparing each of said reflection coefficients with indexed elements of threshold values identifying quantizer cell boundaries, thereby to determine an index identifying a quantizer cell, and based on the index identified for each reflection coefficient, assigning a quantizer output value corresponding to a quantizer cell.

Claim 14

Dependent Claim 29 words

The method of claim 12, wherein each of said threshold values is an inverse transform value of a quantizer cell boundary value from a transform domain range of values.

Claim 15

Dependent Claim 53 words

The method of claim 12, wherein said indexed elements of threshold values are stored in an ordered table of threshold values, with each threshold value having a uniquely associated index, and said comparing to determine an index value comprises searching of values in said table to find a value meeting a predetermined criterion.

Claim 16

Dependent Claim 24 words

The method of claim 14, wherein said searching comprises a binary tree search of said table based on the value of said reflection coefficients.

Claim 17

Dependent Claim 61 words

The method of claim 2, wherein said adjusting of the parameters of said long-term filter further comprises extracting a pitch lag parameter based on said linear predictive analysis of each of said sequences of input samples, and wherein said outputting parameters of said synthesis filter comprises outputting a coded representation of said pitch lag parameter for each sequence of input samples.

Claim 18

Dependent Claim 88 words

The method of claim 2, wherein said adjusting of the parameter of said long-term filter further comprises grouping a plurality of consecutive sequences of input samples into a frame of input samples, each of said sequences of input samples thereby comprising a sub-frame extracting a pitch lag parameter for each subframe based on said linear predictive analyses of said subframe, and wherein said outputting parameters of said synthesis filter comprises outputting a coded representation of said pitch lag parameter and said pitch predictor tap weights for each subframe.

Claim 19

Dependent Claim 78 words

The method of claim 17, wherein said extracting of a pitch lag parameter comprises generating a set of signals representing LPC residuals for the current subframe of input samples, forming a cross correlation, for each of a range of lag values, based on said LPC residuals for the current frame and the LPC residuals for a plurality of prior subframes, selecting a pitch lag parameter based on the lag value of said cross correlation having the largest value.

Claim 20

Dependent Claim 44 words

The method of claim 18, wherein said LPC residuals for said current subframe and for said prior subframes are time decimated prior to said cross correlation, and said method further comprises adjusting said selected value of said lag parameter to reflect the time decimation.

Claim 21

Dependent Claim 62 words

The method of claim 17, wherein said plurality of tap weights comprises three tap weights, said long-term filter component has a transfer function given by ##EQU27## said storing one or more pitch tap vectors corresponding to each possible set of quantized tap weights comprises storing a vector given by y=[2b.sub.1, 2b.sub.2, 2b.sub.3, -2b.sub.1 b.sub.2, -2b.sub.2 b.sub.3, -2b.sub.3 b.sub.1, -b.sub.1.sup.2, -b.sub.2.sup.2, -b.sub.3.sup.2 ].sup.T.

Claim 22

Dependent Claim 112 words

The method of claim 1 wherein said sequence of input samples is a current sequence of input samples in a plurality of consecutive sequences of input samples, said plurality of consecutive sequences of input samples having at least one sequence of input samples preceding said current sequence of input samples, said synthesis filter comprising memory, said memory storing a residual signal reflecting codevector information corresponding to said at least part of at least one sequence of input samples preceding said current sequence of input samples, said residual signal giving rise to a contribution to said candidate codevectors, the method further comprising removing said contribution to said candidate codevectors prior to said comparing.

Claim 23

Dependent Claim 22 words

The method of claim 1, wherein said comparing comprises perceptually weighting said input samples and said candidate codevectors prior to said comparing.

Claim 24

Dependent Claim 112 words

The method of claim 22 wherein said sequence of input samples is a current sequence of input samples in a plurality of consecutive sequences of input samples, said plurality of consecutive sequences of input samples havinq at least one sequence of input samples preceding said current sequence of input samples, said synthesis filter comprising memory, said memory storinq a residual signal reflecting codevector information corresponding to said at least part of at least one sequence of input samples preceding said current sequence of input samples, said residual signal giving rise to a contribution to said candidate codevectors, the method further comprising removing said contribution to said candidate codevectors prior to said comparing.

Claim 25

Dependent Claim 52 words

The method of claim 1 wherein said plurality of codevectors comprises M/2 linearly independent codevectors, where M is the number of codevectors that are gain adjusted, said comparing comprises comparing M codevectors, said M codevectors being based on said M/2 linearly independent codevectors and each of two sign values for said codevectors.

Claim 26

Dependent Claim 35 words

The method of claim 1, wherein said backward adaptive gain controller is adaptively adjusted by the further step of passing gain information relating to said codevector corresponding to said outputted index through said gain controller.

Claim 27

Dependent Claim 13 words

The method of claim 1 further comprising storing said outputted index and parameters.

Claim 28

Dependent Claim 17 words

The method of claim 1 further comprising transmitting said outputted index and parameters to a communications medium.

Claim 29

Dependent Claim 102 words

The method of claim 1 for processing a set of additional sequences of input samples, the set of additional sequences of input samples being subsequent to the sequence of input samples previously processed, the method comprising: (a) adjusting the parameters of the synthesis filter in response to a previous sequence of input samples; (b) repeating the steps of gain adjusting, filtering, comparing, and outputting for a next sequence of input samples from the set of additional sequences of input samples; and (c) repeating steps (a) and (b) until each sequence in the set of additional sequences of input samples has been processed.

Claim 30

Dependent Claim 27 words

The method of claim 1 wherein the step of comparing further comprises determining the candidate codevector having the minimum difference relative to the sequence of input samples.

Claim 31

Independent Claim 148 words

A method of processing a sequence of input samples comprising: (a) gain adjusting the sequence of input samples in a backward adaptive gain controller to produce a gain-adjusted sequence of input samples; (b) filtering each of a plurality of codevectors in a synthesis filter characterized by a plurality of filter parameters to generate a plurality of candidate codevectors, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, each of the plurality of codevectors having an index associated therewith; (c) comparing the plurality of candidate codevectors with the gain-adjusted sequence of input samples to determine a candidate codevector substantially approximating the gain-adjusted sequence of input samples; and (d) outputting (i) the index associated with the candidate codevector substantially approximating the gain-adjusted sequence of input samples; and (ii) the parameters of said long term synthesis filter.

Claim 32

Independent Claim 148 words

A method of processing a sequence of input samples comprising: (a) gain adjusting the sequence of input samples in a backward adaptive gain controller to produce a gain-adjusted sequence of input samples; (b) filtering each of a plurality of codevectors in a synthesis filter characterized by a plurality of filter parameters to generate a plurality of candidate codevectors, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, each of the plurality of codevectors having an index associated therewith; (c) comparing the plurality of candidate codevectors with the gain-adjusted sequence of input samples to determine a candidate codevector substantially approximating the gain-adjusted sequence of input samples; and (d) outputting (i) the index associated with the candidate codevector substantially approximating the gain-adjusted sequence of input samples; and (ii) the parameters of said long term synthesis filter.

Claim 33

Dependent Claim 98 words

The method of claim 30 for processing a set of additional sequences of input samples, the set of additional sequences of input samples being subsequent to the sequence of input samples previously processed, the method comprising: (a) adjusting the parameters of the synthesis filter in response to a previous sequence of input samples; (b) repeating steps (a) through (d) for a next sequence of input samples from the set of additional sequences of input samples; and (c) repeating steps (a) and (b) until each additional sequence in the set of additional sequences of input samples has been processed.

Claim 34

Dependent Claim 68 words

The method of claim 31 wherein adjusting the parameters of the synthesis filter comprises adjusting parameters of the long term filter comprising: (a) grouping a plurality of consecutive sequences of input samples into a frame of input samples, each of the sequences of input samples thereby comprising a sub-frame; and (b) extracting a pitch lag parameter for each sub-frame based on the linear predictive analysis of the sub-frame.

Claim 35

Dependent Claim 26 words

The method of claim 32 wherein outputting the parameters of the synthesis filter comprises outputting a coded representation of the pitch lag parameter for each sub-frame.

Claim 36

Dependent Claim 20 words

The method of claim 30 wherein adjusting the parameters of the synthesis filter is based upon a linear predictive analysis.

Claim 37

Dependent Claim 62 words

The method of claim 34 wherein the linear predictive analysis comprises: (a) grouping a plurality of consecutive sequences of input samples into a frame of input samples; (b) performing an autocorrelation analysis of the frame of input samples to generate a set of autocorrelation coefficients; and (c) determining a set of Nth order predictor coefficients based on the set of autocorrelation coefficients.

Claim 38

Dependent Claim 27 words

The method of claim 30 wherein the step of comparing further comprises determining the candidate codevector having the minimum difference relative to the sequence of input samples.

Claim 39

Independent Claim 150 words

A method of processing a first signal by utilizing a set of second signals, the method comprising: (a) in a backward adaptive gain controller, producing a gain-adjusted first signal and a gain-adjusted set of second signals; (b) filtering the gain-adjusted set of second signals in a synthesis filter characterized by a plurality of filter parameters to generate a filtered set of second signals, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, each signal in the filtered set of second signals having an index associated therewith; (c) comparing each signal in the filtered set of second signals with the gain-adjusted first signal to determine a filtered second signal substantially approximating the gain-adjusted first signal; and (d) outputting (i) the index associated with the filtered second signal; and (ii) the parameters of said long term synthesis filter.

Claim 40

Independent Claim 150 words

A method of processing a first signal by utilizing a set of second signals, the method comprising: (a) in a backward adaptive gain controller, producing a gain-adjusted first signal and a gain-adjusted set of second signals; (b) filtering the gain-adjusted set of second signals in a synthesis filter characterized by a plurality of filter parameters to generate a filtered set of second signals, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, each signal in the filtered set of second signals having an index associated therewith; (c) comparing each signal in the filtered set of second signals with the gain-adjusted first signal to determine a filtered second signal substantially approximating the gain-adjusted first signal; and (d) outputting (i) the index associated with the filtered second signal; and (ii) the parameters of said long term synthesis filter.

Claim 41

Dependent Claim 20 words

The method of claim 32 wherein the step of producing a gain-adjusted first signal comprises leaving the first signal unchanged.

Claim 42

Dependent Claim 24 words

The method of claim 32 wherein the step of producing a gain-adjusted set of second signals comprises leaving the set of second signals unchanged.

Claim 43

Dependent Claim 88 words

The method of claim 32 for processing a set of additional first signals, the set of additional first signals being subsequent to the first signal previously processed, the method comprising: (a) adjusting the parameters of the synthesis filter in response to a previous first signal; (b) repeating steps (a) through (d) of claim 36 for a next first signal from the set of additional first signals; and (c) repeating steps (a) and (b) until each additional first signal in the set of additional first signals has been processed.

Claim 44

Dependent Claim 20 words

The method of claim 40 wherein adjusting the parameters of the synthesis filter is based upon a linear predictive analysis.

Claim 45

Dependent Claim 60 words

The method of claim 41 wherein the linear predictive analysis comprises: (a) grouping a plurality of consecutive first signals into a frame of input samples; (b) performing an autocorrelation analysis of the frame of first signals to generate a set of autocorrelation coefficients; and (c) determining a set of Nth order predictor coefficients based on the set of autocorrelation coefficients.

Claim 46

Dependent Claim 64 words

The method of claim 40 wherein adjusting the parameters of the synthesis filter comprises adjusting parameters of the long term filter comprising: (a) grouping a plurality of consecutive first signals into a frame of input samples, each of the first signals thereby comprising a sub-frame; and (b) extracting a pitch lag parameter for each sub-frame based on the linear predictive analysis of the sub-frame.

Claim 47

Dependent Claim 26 words

The method of claim 43 wherein outputting the parameters of the synthesis filter comprises outputting a coded representation of the pitch lag parameter for each sub-frame.

Claim 48

Dependent Claim 33 words

The method of claim 32 wherein the step of comparing further comprises determining a filtered second signal in the filtered set of second signals having the minimum difference relative to the first signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-07-04	1998-01-03	1998-07-05	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-07-04	2002-01-03	2002-07-05	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-07-04	2006-01-03	2006-07-05	$7700.00	Window Closed / Lapsed

Method of use of voice message coder/decoder

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