US5235671A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dynamic bit allocation subband excited transform coding method and apparatus
Assignee: Verizon Laboratories Inc
•
Filing: 1990-10-15
•
Granted: 1993-08-10
•
Expires: 2010-10-15
Abstract
Abstract In an adaptive subband excited transform speech encoding system, a range of quantizers are available and are dynamically selected for each window of speech. The quantizers designated for individual subbands are determined to minimize mean squared error distortion in the recreated signal while using no more than a predetermined number of quantization bits per window of speech.
Inventors
- 👤 Baruch Mazor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 21:13
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/66; H04B1/667; G; G10; G10L; G10L19/00; G10L19/02; G10L19/0204
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
149 words
A speech coding system comprising: transform means for performing a discrete transform of a window of speech to generate a discrete transform spectrum of coefficients comprising a plurality of subbands of coefficients; envelope defining and encoding means for defining an approximate envelope of the discrete spectrum of coefficients in each of the plurality of subbands of coefficients and for encoding the defined envelope of each subband of coefficients; means for scaling each spectrum coefficient relative to the encoded defined envelope of the respective subband of coefficients; a plurality of quantizers having different bit lengths for encoding the scaled spectrum coefficients within each subband; and means for determining a quantizer from the plurality of quantizers having different bit lengths, if any, to be used to encode the scaled spectrum coefficients of each subband within each window of speech wherein the selection of available quantizers used in successive windows is variable.
Claim 2
Dependent Claim
149 words
A speech coding system comprising: transform means for performing a discrete transform of a window of speech to generate a discrete transform spectrum of coefficients comprising a plurality of subbands of coefficients; envelope defining and encoding means for defining an approximate envelope of the discrete spectrum of coefficients in each of the plurality of subbands of coefficients and for encoding the defined envelope of each subband of coefficients; means for scaling each spectrum coefficient relative to the encoded defined envelope of the respective subband of coefficients; a plurality of quantizers having different bit lengths for encoding the scaled spectrum coefficients within each subband; and means for determining a quantizer from the plurality of quantizers having different bit lengths, if any, to be used to encode the scaled spectrum coefficients of each subband within each window of speech wherein the selection of available quantizers used in successive windows is variable.
Claim 3
Dependent Claim
25 words
A speech coding system as claimed in claim 1 wherein the means for determining allocates bits to minimize quantization error for each window of speech.
Claim 4
Dependent Claim
36 words
A speech coding system as claimed in claim 1 wherein the means for determining iteratively estimates distortion and computes for each distortion estimate a bit allocation across the spectrum to allocate a predetermined number of bits.
Claim 5
Dependent Claim
65 words
A speech coding system as claimed in claim 3 wherein the means for determining computes the allocation of bits as a number of bits greater than or equal to zero which is derived from log 2 (P i /D) for each subband where P i is a power density estimate for the subband and D is a distortion error estimate for the window of speech.
Claim 6
Dependent Claim
27 words
A speech coding system as claimed in claim 4 wherein P i is estimated for each subband from the defined envelope of the respective subband of coefficients.
Claim 7
Dependent Claim
39 words
A speech coding system as claimed in claim 4 wherein the means for determining tunes the computed bit allocation toward the number of available bits by adding bits to higher energy subbands or subtracting bits from lower energy subbands.
Claim 8
Dependent Claim
27 words
A speech coding system as claimed in claim 6 wherein P i is estimated for each subband from the defined envelope of the respective subband of coefficients.
Claim 9
Dependent Claim
18 words
A speech coding system as claimed in claim 1 wherein the transform means performs a discrete Fourier transform.
Claim 10
Dependent Claim
28 words
A speech coding system as claimed in claim 1, wherein the means for determining a quantizer determines each quantizer based on the spectral envelope in the transform domain.
Claim 11
Dependent Claim
46 words
A speech coding system as claimed in claim 1, further comprising a power spectrum means for estimating spectral power density of each subband of coefficients, wherein the means for determining a quantizer determines each quantizer based upon the spectral power density of the subbands of coefficients.
Claim 12
Independent Claim
139 words
A method of coding speech comprising: performing a discrete transform of a window of speech to generate a discrete spectrum of coefficients comprising a plurality of subbands of coefficients; defining an approximate envelope of the discrete spectrum of coefficients in each of the plurality of subbands of coefficients and digitally encoding the defined envelope of each subband of coefficients; dynamically selecting a quantizer from a plurality of quantizers having different bit lengths for use with each subband of each window of speech to minimize distortion, the selection of available quantizers used in successive windows being variable and based on spectral power density of the window; scaling the coefficients within the subbands relative to the defined approximate envelopes of the subbands; and encoding each of the scaled coefficients within the subbands into a number of bits using the selected quantizer.
Claim 13
Independent Claim
139 words
A method of coding speech comprising: performing a discrete transform of a window of speech to generate a discrete spectrum of coefficients comprising a plurality of subbands of coefficients; defining an approximate envelope of the discrete spectrum of coefficients in each of the plurality of subbands of coefficients and digitally encoding the defined envelope of each subband of coefficients; dynamically selecting a quantizer from a plurality of quantizers having different bit lengths for use with each subband of each window of speech to minimize distortion, the selection of available quantizers used in successive windows being variable and based on spectral power density of the window; scaling the coefficients within the subbands relative to the defined approximate envelopes of the subbands; and encoding each of the scaled coefficients within the subbands into a number of bits using the selected quantizer.
Claim 14
Dependent Claim
21 words
A method as claimed in claim 11 wherein the quantizers are determined to minimize quantization error for each window of speech.
Claim 15
Dependent Claim
34 words
A method as claimed in claim 11 wherein the quantizers are selected iteratively estimating distortion and computing for each distortion estimate a bit allocation across the spectrum to allocate a predetermined number of bits.
Claim 16
Dependent Claim
63 words
A method as claimed in claim 13 wherein the quantizers are selected computing the allocation of bits as a number of bits greater than or equal to zero which is derived from log 2 (P i /D) for each subband where P i is a power density estimate for the subband and D is a distortion error estimate for the window of speech.
Claim 17
Dependent Claim
25 words
A method as claimed in claim 14 wherein P i is estimated for each subband from the defined envelope of the respective subband of coefficients.
Claim 18
Dependent Claim
34 words
A method as claimed in claim 14 wherein the allocation of bits is tuned toward the number of available bits by adding bits to higher energy subbands and subtracting bits from lower energy subbands.
Claim 19
Dependent Claim
25 words
A method as claimed in claim 16 wherein P i is estimated for each subband from the defined envelope of the respective subband of coefficients.
Claim 20
Dependent Claim
15 words
A method as claimed in claim 11 wherein the transform is a discrete Fourier transform.
References Cited (Backward Citations)
US4184049A
Cited
US4330689A
Cited
US4538234A
Cited
US4610022A
Cited
US4455649A
Cited
US4535472A
Cited
EP0176243A2
Cited
US4914701A
Cited
US4790016A
Cited
US4956871A
Cited
US5042069A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-08-09 | 1997-02-08 | 1997-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-08-09 | 2001-02-08 | 2001-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-08-09 | 2005-02-08 | 2005-08-10 | $7700.00 | Window Closed / Lapsed |