US6047254A
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US
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System and method for determining a first formant analysis filter and prefiltering a speech signal for improved pitch estimation
Assignee: Saxon Innovations LLC
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Filing: 1997-10-24
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Granted: 2000-04-04
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Expires: 2017-10-24
Abstract
Abstract The present invention comprises an improved vocoder system and method for estimating the pitch of a speech signal. The speech signal comprises a stream of digitized speech samples. The speech samples are partitioned into frames. For each frame of the speech signal, an optimal order-two inverse filter is determined. The optimal order-two inverse filter is determined by computing an order-two inverse filter at various locations within the speech frame. For each order-two inverse filter an energy value is calculated which represents the proportion of energy which would remain if the speech signal were filtered with the order-two inverse filter. The order-two inverse filter which minimizes the energy proportion is chosen to be the optimal order-two inverse filter. The optimal order-two inverse filter is then used to filter the samples of the speech frame. An autocorrelation is performed on the filtered signal for a range of tine-delay values. The peaks of the autocorrelation function are analyzed to determine the pitch period.
Inventors
- 👤 Mark A. Ireton
- 👤 John G. Bartkowiak
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 16:15
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/04; G10L19/08; G10L25/00; G10L25/90; G10L19/09; G10L25/03; G10L25/06; G10L25/15
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
119 words
A method for performing pitch estimation which pre-filters speech data prior to pitch estimation, comprising: receiving a frame of speech data comprising a plurality of speech samples; determining an order-two inverse filter for said frame of speech data, wherein said determining uses said plurality of speech samples comprising said speech frame; filtering said frame of speech data using said order-two inverse filter, wherein said filtering removes first formant signal information from said frame of speech data, wherein said filtering results in a filtered speech frame; and performing pitch estimation on said filtered speech frame to estimate a pitch value for said filtered speech frame; wherein said pitch value is useable to represent the speech data in a compressed format.
Claim 2
Independent Claim
119 words
A method for performing pitch estimation which pre-filters speech data prior to pitch estimation, comprising: receiving a frame of speech data comprising a plurality of speech samples; determining an order-two inverse filter for said frame of speech data, wherein said determining uses said plurality of speech samples comprising said speech frame; filtering said frame of speech data using said order-two inverse filter, wherein said filtering removes first formant signal information from said frame of speech data, wherein said filtering results in a filtered speech frame; and performing pitch estimation on said filtered speech frame to estimate a pitch value for said filtered speech frame; wherein said pitch value is useable to represent the speech data in a compressed format.
Claim 3
Dependent Claim
84 words
The method of claim 1, wherein said determining an order-two inverse filter comprises: computing a plurality of candidate order-two inverse filters at a plurality of locations in said frame of speech data; computing an energy value for each of said candidate order-two inverse filters, wherein the energy value represents the proportion of signal energy that would be removed if the frame of speech data were filtered with the corresponding candidate order-two inverse filter; and choosing the candidate order-two inverse filter with minimum energy value.
Claim 4
Dependent Claim
34 words
The method of claim 2, wherein the computing of each of said candidate order-two inverse filters comprises analyzing a number of speech samples which span less than a full pitch period in time duration.
Claim 5
Dependent Claim
25 words
The method of claim 3, wherein said number of speech samples is determined using the pitch period estimated from a previous frame of speech data.
Claim 6
Dependent Claim
25 words
The method of claim 2, wherein the computing of each of said candidate order-two inverse filters comprises performing an order-two Linear Predictive Coding (LPC) analysis.
Claim 7
Dependent Claim
18 words
The method of claim 5, wherein said performing an order-two LPC analysis comprises applying the covariance estimation technique.
Claim 8
Dependent Claim
18 words
The method of claim 5, wherein said performing an order-two LPC analysis comprises applying the autocorrelation estimation technique.
Claim 9
Dependent Claim
18 words
The method of claim 5, wherein said performing an order-two LPC analysis comprises applying the Burg estimation technique.
Claim 10
Dependent Claim
59 words
The method of claim 2, wherein the computing of each of said candidate order two inverse filters produces a pair of filter coefficients a 1 and a 2 , wherein a pair of reflection coefficients k 1 and k 2 are calculated according to the relations ##EQU26## and wherein said energy value is calculated according to the equation ##EQU27##10.
Claim 11
Dependent Claim
53 words
The method of claim 1, wherein said performing pitch estimation on said filtered speech frame comprises: performing an autocorrelation on said filtered speech frame for a range of time-delay values; applying a threshold to the peaks of said autocorrelation function; and analyzing the peaks of said autocorrelation function to estimate said pitch period.
Claim 12
Dependent Claim
169 words
A vocoder which pre-filters speech data prior to pitch estimation comprising: an input for receiving a frame of speech data, wherein said frame of speech data comprises a plurality of speech samples; and at least one processor for analyzing said speech data and performing pitch estimation on said speech data; wherein said at least one processor is operable to determine an order-two inverse filter for said frame of speech data, wherein said determination uses said plurality of speech samples comprising said speech frame; wherein said at least one processor is further operable to filter said frame of speech data using said order-two inverse filter to remove first formant signal information from said frame of speech data, wherein said filtering results in a filtered speech frame; wherein said at least one processor is further operable to perform pitch estimation on said filtered speech frame to estimate a pitch value for said filtered speech frame; and wherein said pitch value is useable to represent the speech data in a compressed format.
Claim 13
Dependent Claim
169 words
A vocoder which pre-filters speech data prior to pitch estimation comprising: an input for receiving a frame of speech data, wherein said frame of speech data comprises a plurality of speech samples; and at least one processor for analyzing said speech data and performing pitch estimation on said speech data; wherein said at least one processor is operable to determine an order-two inverse filter for said frame of speech data, wherein said determination uses said plurality of speech samples comprising said speech frame; wherein said at least one processor is further operable to filter said frame of speech data using said order-two inverse filter to remove first formant signal information from said frame of speech data, wherein said filtering results in a filtered speech frame; wherein said at least one processor is further operable to perform pitch estimation on said filtered speech frame to estimate a pitch value for said filtered speech frame; and wherein said pitch value is useable to represent the speech data in a compressed format.
Claim 14
Dependent Claim
110 words
The vocoder of claim 11, wherein in performing said determination of said order-two inverse filter: the at least one processor is operable to compute a plurality of candidate order-two inverse filters at a plurality of locations in said frame of speech data; the at least one processor is operable to compute an energy value for each of said candidate order-two inverse filters, wherein the energy value represents the proportion of signal energy that would be removed if the frame of speech data were filtered with the corresponding candidate order-two inverse filter; the at least one processor is operable to choose the candidate order-two inverse filter with the minimum energy value.
Claim 15
Dependent Claim
38 words
The vocoder of claim 12, wherein in said computing of each of said candidate order-two inverse filters the at least one processor analyzes a number of speech samples which span less than a pitch period in time duration.
Claim 16
Dependent Claim
25 words
The vocoder of claim 13, wherein said number of speech samples is determined using the pitch period estimated from a previous frame of speech data.
Claim 17
Dependent Claim
30 words
The vocoder of claim 12, wherein in said computing of each of said candidate order-two inverse filters the at least one processor performs an order-two Linear Predictive Coding (LPC) analysis.
Claim 18
Dependent Claim
72 words
The vocoder of claim 12, wherein in said computing of each of said candidate order two inverse filters: the at least one processor produces a pair of filter coefficients a 1 and a 2 ; and the at least one processor calculates a pair of reflection coefficients k 1 and k 2 according to the relations ##EQU28## and the at least one processor calculates said energy value according to the equation ##EQU29##
Claim 19
Dependent Claim
77 words
The vocoder of claim 11, wherein in said performing pitch estimation on said filtered speech frame: the at least one processor is operable to perform an autocorrelation on said filtered speech frame for a range of time-delay values; the at least one processor is operable to apply a threshold to the peaks of said autocorrelation function; and the at least one processor is operable to analyze the peaks of said autocorrelation function to estimate said pitch period.
References Cited (Backward Citations)
US3787778A
Cited
US4128737A
Cited
US4301328A
Cited
US4433210A
Cited
US4544919A
Cited
US4470150A
Cited
US4680797A
Cited
US4879748A
Cited
US4890328A
Cited
US4912764A
Cited
US4820059A
Cited
US4813076A
Cited
US4817157A
Cited
US4896361A
Cited
US5018200A
Cited
US5629955A
Cited
US5414796A
Cited
US5596676A
Cited
US5577160A
Cited
US5491771A
Cited
US5567420A
Cited
US5812966A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-04-04 | 2003-10-04 | 2004-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-04-04 | 2007-10-04 | 2008-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-04-04 | 2011-10-04 | 2012-04-04 | $7700.00 | Window Closed / Lapsed |