US5226084A
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US
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Methods for speech quantization and error correction
Assignee: Digital Voice Systems Inc
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Filing: 1990-12-05
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Granted: 1993-07-06
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Expires: 2010-12-05
Abstract
Abstract The redundancy contained within the spectral amplitudes is reduced, and as a result the quantization of the spectral amplitudes is improved. The prediction of the spectral amplitudes of the current segment from the spectral amplitudes of the previous is adjusted to account for any change in the fundamental frequency between the two segments. The spectral amplitudes prediction residuals are divided into a fixed number of blocks each containing approximately the same number of elements. A prediction residual block average (PRBA) vector is formed; each element of the PRBA is equal to the average of the prediction residuals within one of the blocks. The PRBA vector is vector quantized, or it is transformed with a Discrete Cosine Transform (DCT) and scalar quantized. The perceived effect of bit errors is reduced by smoothing the voiced/unvoiced decisions. An estimate of the error rate is made by locally averaging the number of correctable bit errors within each segment. If the estimate of the error rate is greater than a threshold, then high energy spectral amplitudes are declared voiced.
Inventors
- 👤 John C. Hardwick
- 👤 Jae S. Lim
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:17
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/02; G10L19/032; G10L19/038; G10L19/005; G10L19/0212; G10L19/04; G10L19/08; G10L19/087; G10L21/00; G10L21/02; G10L21/0316; G10L21/0364; H; H03; H03M; H03M13/00; H03M13/35; G10L19/06; G10L19/10; G10L21/0208; G10L21/0216; G10L21/0232
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
167 words
A method of encoding a speech signal, the method comprising the steps: breaking said signal into segments, each of said segments representing one of a succession of time intervals and having a spectrum of frequencies; for each said segment, sampling said spectrum at a set of frequencies, thereby forming a set of actual spectral amplitudes, wherein the frequencies at which said spectra are sampled generally differ from one segment to the next; producing predicted spectral amplitudes for said current segment based on the spectral amplitudes for at least one previous segment, wherein said predicted spectral amplitudes for said current segment are based at least in part on interpolating the spectral amplitudes of a previous segment to estimate the spectral amplitudes in the previous segment at the frequencies of said current segment; producing prediction residuals based on a difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment; and producing an encoded speech signal based on said prediction residuals.
Claim 2
Independent Claim
167 words
A method of encoding a speech signal, the method comprising the steps: breaking said signal into segments, each of said segments representing one of a succession of time intervals and having a spectrum of frequencies; for each said segment, sampling said spectrum at a set of frequencies, thereby forming a set of actual spectral amplitudes, wherein the frequencies at which said spectra are sampled generally differ from one segment to the next; producing predicted spectral amplitudes for said current segment based on the spectral amplitudes for at least one previous segment, wherein said predicted spectral amplitudes for said current segment are based at least in part on interpolating the spectral amplitudes of a previous segment to estimate the spectral amplitudes in the previous segment at the frequencies of said current segment; producing prediction residuals based on a difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment; and producing an encoded speech signal based on said prediction residuals.
Claim 3
Dependent Claim
16 words
The method of claim 1 wherein said interpolating of spectral amplitudes is performed using linear interpolation.
Claim 4
Independent Claim
152 words
A method of encoding a speech signal, the method comprising the steps: breaking said signal into segments, each of said segments representing one of a succession of time intervals and having a spectrum of frequencies; for each said segment, sampling said spectrum at a set of frequencies, thereby forming a set of spectral amplitudes, wherein the frequencies at which said spectra are sampled generally differ from one segment to the next; producing predicted spectral amplitudes for said current segment based on the spectral amplitudes for at least one previous segment; producing prediction residuals based on a difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment; grouping said prediction residuals into a predetermined number of blocks, the number of blocks being independent of the number of said prediction residuals grouped into particular blocks; and producing an encoded speech signal based on said blocks.
Claim 5
Independent Claim
152 words
A method of encoding a speech signal, the method comprising the steps: breaking said signal into segments, each of said segments representing one of a succession of time intervals and having a spectrum of frequencies; for each said segment, sampling said spectrum at a set of frequencies, thereby forming a set of spectral amplitudes, wherein the frequencies at which said spectra are sampled generally differ from one segment to the next; producing predicted spectral amplitudes for said current segment based on the spectral amplitudes for at least one previous segment; producing prediction residuals based on a difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment; grouping said prediction residuals into a predetermined number of blocks, the number of blocks being independent of the number of said prediction residuals grouped into particular blocks; and producing an encoded speech signal based on said blocks.
Claim 6
Dependent Claim
45 words
The method of claim 3 wherein said predicted spectral amplitudes for said current segment are based at lest in part on interpolating the spectral amplitudes of a previous segment to estimate the spectral amplitudes in the previous segment at the frequencies of said current segment.
Claim 7
Independent Claim
156 words
A method of encoding a speech signal, the method comprising the steps: breaking said signal into segments, each of said segments representing one of a succession of time intervals and having a spectrum of frequencies; for each said segment, sampling said spectrum at a set of frequencies, thereby forming a set of spectral amplitudes, wherein the frequencies at which the spectra are sampled generally differ from one segment to the next; producing predicted spectral amplitudes for said current segment based on the spectral amplitudes for at least one previous segment; producing prediction residuals based on a difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment; grouping said prediction residuals into blocks; forming a prediction residual block average (PRBA) vector, each value of said PRBA vector being an average of the prediction residuals of a corresponding block; and producing an encoded speech signal based on said PRBA.
Claim 8
Independent Claim
156 words
A method of encoding a speech signal, the method comprising the steps: breaking said signal into segments, each of said segments representing one of a succession of time intervals and having a spectrum of frequencies; for each said segment, sampling said spectrum at a set of frequencies, thereby forming a set of spectral amplitudes, wherein the frequencies at which the spectra are sampled generally differ from one segment to the next; producing predicted spectral amplitudes for said current segment based on the spectral amplitudes for at least one previous segment; producing prediction residuals based on a difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment; grouping said prediction residuals into blocks; forming a prediction residual block average (PRBA) vector, each value of said PRBA vector being an average of the prediction residuals of a corresponding block; and producing an encoded speech signal based on said PRBA.
Claim 9
Dependent Claim
30 words
The method of claim 5 wherein said blocks are of a predetermined number, the number of blocks being independent of the number of said prediction residuals grouped into particular blocks.
Claim 10
Dependent Claim
45 words
The method of claim 6 wherein the predicted spectral amplitudes for said current segment are based at least in part on interpolating the spectral amplitudes of a previous segment to estimate the spectral amplitudes in the previous segment at the frequencies of said current segment.
Claim 11
Dependent Claim
33 words
The method of claim 5, 6 or 7 wherein said average is computed by adding the prediction residuals within the block and dividing by the number of prediction residuals grouped into that block.
Claim 12
Dependent Claim
38 words
The method of claim 8 wherein said average is obtained by computing the coefficients of a Discrete Cosine Transform (DCT) of the prediction residuals within a block and using the fist coefficient of the DCT as said average.
Claim 13
Dependent Claim
31 words
The method of claim 5, 6 or 7 wherein encoding said PRBA vector comprises performing a linear transform on the PRBA vector producing transform coefficients and scalar quantizing said transform coefficients.
Claim 14
Dependent Claim
14 words
The method of claim 10 wherein said linear transform comprises a Discrete Cosine Transform.
Claim 15
Dependent Claim
19 words
The method of claim 5, 6 or 7 wherein encoding said PRBA vector comprises vector quantizing said PRBA vector.
Claim 16
Independent Claim
59 words
The method of claims 5, 6 or 7 wherein encoding said PRBA vector is performed using a method comprising the steps of: determining an average of said PRBA vector; quantizing said average using scalar quantization; and vector quantizing said PRBA vector using a codebook consisting of code vectors, each of said code vectors having a mean equal to zero.
Claim 17
Dependent Claim
16 words
The method of claim 3, 6 or 7 wherein said predetermined number is equal to six.
Claim 18
Dependent Claim
39 words
The method of claim 14 wherein the difference between the number of sampled frequencies grouped into the highest frequency block and the number of sampled frequencies grouped into the lowest frequency block is less than or equal to one.
Claim 19
Dependent Claim
35 words
The method of claim 3, 6 or 7 wherein the number of prediction residuals grouped into a lower frequency block is not larger than the number of prediction residuals grouped into a higher frequency block.
Claim 20
Dependent Claim
45 words
The method of claim 1, 3, or 5 wherein said difference between the actual spectral amplitudes for said current segment and the predicted spectral amplitudes for said current segment is formed by subtracting a fraction of the predicted spectral amplitudes from the actual spectral amplitudes.
Claim 21
Dependent Claim
20 words
The method of claim 1, 3 or 5 wherein the spectral amplitudes are obtained using a Multiband Excitation speech model.
Claim 22
Dependent Claim
18 words
The method of claim 1, 3 or 5 wherein the spectral amplitudes are obtained using sinusoidal transform coding.
Claim 23
Dependent Claim
30 words
The method of claim 1, 3 or 5 wherein only spectral amplitudes from the most recent previous segment are used in forming the predicted spectral amplitudes of said current segment.
Claim 24
Dependent Claim
30 words
The method of claim 1, 3 or 5 wherein said spectrum comprises a fundamental frequency and said set of frequencies for a given segment are multiples of said fundamental frequency.
Claim 25
Independent Claim
82 words
A method of synthesizing speech from a received bit stream, said bit stream representing speech segments and having bit errors, the method comprising the steps of: estimating a bit error rate for each speech segment; for each said speech segment, deciding whether to decode said speech segment as a voided or an unvoiced speech segment; smoothing the voice/unvoiced decisions based on the estimate of the bit error rate for said speech segment; and synthesizing a speech signal using said smoothed voiced/unvoiced decisions.
Claim 26
Independent Claim
82 words
A method of synthesizing speech from a received bit stream, said bit stream representing speech segments and having bit errors, the method comprising the steps of: estimating a bit error rate for each speech segment; for each said speech segment, deciding whether to decode said speech segment as a voided or an unvoiced speech segment; smoothing the voice/unvoiced decisions based on the estimate of the bit error rate for said speech segment; and synthesizing a speech signal using said smoothed voiced/unvoiced decisions.
Claim 27
Independent Claim
89 words
A method of synthesizing speech from a received bit stream, said bit stream representing frequency bands of speech segments and having bit errors, the method comprising the steps of: estimating a bit error rate for each speech segment; for each frequency band of each said speech segment, deciding whether to decode the frequency band of said speech segment as voiced or unvoiced; smoothing the voiced/unvoiced decisions based on the estimated of the bit error rate for said speech segment; and synthesizing a speech signal using said method voiced/unvoiced decisions.
Claim 28
Independent Claim
89 words
A method of synthesizing speech from a received bit stream, said bit stream representing frequency bands of speech segments and having bit errors, the method comprising the steps of: estimating a bit error rate for each speech segment; for each frequency band of each said speech segment, deciding whether to decode the frequency band of said speech segment as voiced or unvoiced; smoothing the voiced/unvoiced decisions based on the estimated of the bit error rate for said speech segment; and synthesizing a speech signal using said method voiced/unvoiced decisions.
Claim 29
Independent Claim
56 words
The method of claims 22 or 23 wherein the smoothing step comprises the steps of: comparing the estimate of the bit error rate of said speech segment with a first predetermined threshold; declaring all high energy spectral amplitudes voiced when said bit error rate is above said first threshold; and leaving all other voiced/unvoiced decisions unaffected.
Claim 30
Dependent Claim
67 words
The method of claim 24 wherein said high energy spectral amplitudes are determined by a method comprising the steps of: for each said speech segment, computing a second threshold which depends on the estimate of the bit error rate for said segment; comparing each spectral amplitude with said second threshold; and determining the spectral amplitude to be high energy if it is greater than said second threshold.
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| 3.5 Years (Year 4) | 1996-07-05 | 1997-01-04 | 1997-07-06 | $2000.00 | Window Closed / Lapsed |
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