Patent US6202045B1 successfully refreshed from Google Patents.
US6202045B1
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Speech coding with variable model order linear prediction
Assignee: RPX Corp
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Filing: 1998-09-30
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Granted: 2001-03-13
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Expires: 2018-09-30
Abstract
Abstract A method of coding a sampled speech signal in which the speech signal is divided into sequential frames. For each current frame, a first set of linear prediction coding (LPC) coefficients are generated, where the number of LPC coefficients depends upon the characteristics of the current frame. If the number of LPC coefficients in the first set of the current frame differs from the number in the first set of the preceding frame, then a second expanded or contracted set of LPC coefficients is generated from the first set of LPC coefficients for the preceding frame. This second set contains the same number of LPC coefficients as are present in said first set of the current frame. Respective sets of line spectral frequency (LSP) coefficients are generated for the first set of LPC coefficients of the current frame and the second set of LPC coefficients of the preceding frame. The sets of LSP coefficients are then combined to provide an encoded residual signal.
Inventors
- 👤 Pasi Ojala
- 👤 Ari Lakaniemi
- 👤 Vesa T. Ruoppila
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:34
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/002; G10L19/04; G10L19/06; G10L19/07
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
154 words
A method of coding a sampled speech signal, the method comprising dividing the speech signal into sequential frames and, for each current frame: generating a first set of linear prediction coding (LPC) coefficients which correspond to the coefficients of a linear filter and which are representative of short term redundancy in the current frame; if the number of LPC coefficients in the first set of the current frame differs from the number in the first set of the preceding frame, then generating a second expanded or contracted set of LPC coefficients from the first set of LPC coefficients generated for the preceding frame, the second set containing a number of LPC coefficients equal to the number of LPC coefficients in said first set of the current frame; and encoding the current frame using the first set of LPC coefficients of the current frame and the second set of LPC coefficients of the preceding frame.
Claim 2
Independent Claim
154 words
A method of coding a sampled speech signal, the method comprising dividing the speech signal into sequential frames and, for each current frame: generating a first set of linear prediction coding (LPC) coefficients which correspond to the coefficients of a linear filter and which are representative of short term redundancy in the current frame; if the number of LPC coefficients in the first set of the current frame differs from the number in the first set of the preceding frame, then generating a second expanded or contracted set of LPC coefficients from the first set of LPC coefficients generated for the preceding frame, the second set containing a number of LPC coefficients equal to the number of LPC coefficients in said first set of the current frame; and encoding the current frame using the first set of LPC coefficients of the current frame and the second set of LPC coefficients of the preceding frame.
Claim 3
Dependent Claim
32 words
A method according to claim 1 , wherein at least one set of expanded or contracted LPC coefficients from the first set of LPC coefficients generated for the preceding frame, are generated.
Claim 4
Dependent Claim
40 words
A method according to claim 2 , wherein a set or sets of expanded or contracted LPC coefficients from the first set of LPC coefficients generated for the preceding frame, corresponding to any available number of LPC parameters, is generated.
Claim 5
Dependent Claim
85 words
A method according to claim 1 , wherein the step of generating the first set of LPCs comprises deriving the autocorrelation function for each frame and solving the equation: a _ opt = R _ _ XX - 1 · R _ XX where a opt are the set of LPCs which minimise the squared error between the current frame x(k) and a frame {circumflex over (x)}(k) predicted using these LPCs, and R XX and R XX are the correlation matrix and correlation vector respectively.
Claim 6
Dependent Claim
28 words
A method according to claim 4 and comprising the step of obtaining an approximate solution to the matrix equation using a recursive process to approximate the LPC coefficients.
Claim 7
Dependent Claim
26 words
A method according to claim 5 and comprising solving the matrix equation using the Levinson-Durbin algorithm in which reflection coefficients are generated as an intermediate product.
Claim 8
Dependent Claim
45 words
A method according to claim 6 , wherein the second expanded or contracted set of LPC coefficients is generated by either adding zero value reflection coefficients, or removing already calculated reflection coefficients, and using the amended set of reflection coefficients to recompute the LPC coefficients.
Claim 9
Dependent Claim
43 words
A method according to claim 1 , wherein the step of encoding and quantising comprises transforming the first set of LPC coefficients of the current frame, and the second set of LPC coefficients of the preceding frame, into respective sets of transformed coefficients.
Claim 10
Dependent Claim
17 words
A method according to claim 8 , wherein said transformed coefficients are line spectral frequency (LSP) coefficients.
Claim 11
Dependent Claim
67 words
A method according to claim 8 wherein the step of encoding comprises encoding the first set of LPC coefficients of the current frame relative to the second set of LPC coefficients of the preceding frame to provide an encoded residual signal and wherein the step of encoding and quantising further comprises generating said encoded residual signal by evaluating the differences between said two sets of transformed coefficients.
Claim 12
Dependent Claim
42 words
A method according to claim 1 , wherein the step of encoding comprises encoding the first set of LPC coefficients of the current frame relative to the second set of LPC coefficients of the preceding frame to provide an encoded residual signal.
Claim 13
Independent Claim
127 words
A method of decoding a sampled speech signal which contains encoded linear prediction coding (LPC) coefficients for each frame of the signal, the method comprising, for each current frame: decoding the encoded signal to determine the number of LPC coefficients encoded for the current frame; where the number of LPC coefficients in a set of LPC coefficients obtained for the preceding frame differs from the number of LPC coefficients encoded for the current frame, expanding or contracting said set of LPC coefficients of the preceding frame to provide a second set of LPC coefficients; and combining said second set of LPC coefficients of the preceding frame with LPC coefficient data for the current frame to provide at least one set of LPC coefficients for the current frame.
Claim 14
Independent Claim
127 words
A method of decoding a sampled speech signal which contains encoded linear prediction coding (LPC) coefficients for each frame of the signal, the method comprising, for each current frame: decoding the encoded signal to determine the number of LPC coefficients encoded for the current frame; where the number of LPC coefficients in a set of LPC coefficients obtained for the preceding frame differs from the number of LPC coefficients encoded for the current frame, expanding or contracting said set of LPC coefficients of the preceding frame to provide a second set of LPC coefficients; and combining said second set of LPC coefficients of the preceding frame with LPC coefficient data for the current frame to provide at least one set of LPC coefficients for the current frame.
Claim 15
Dependent Claim
24 words
A method according to claim 12 , wherein at least one set of expanded or contracted LPC coefficients of the preceding frame are generated.
Claim 16
Dependent Claim
32 words
A method according to claim 13 , wherein a set or sets of expanded or contracted LPC a coefficient of the preceding frame, corresponding to each available LPC model order, is generated.
Claim 17
Dependent Claim
55 words
A method according to claim 12 , wherein the encoded signal contains a set of encoded residual signal, the method further comprising decoding the encoded signal to recover the residual signal and combining the residual signal with the second set of LPC coefficients of the preceding frame to provide LPC coefficients for the current frame.
Claim 18
Dependent Claim
39 words
A method according to claim 12 and comprising combining the set of LPC coefficients obtained for the current frame, and the second set obtained for the preceding frame, to provide sets of LPC coefficients for subframes of each frame.
Claim 19
Dependent Claim
24 words
A method according to claim 16 , wherein the sets of coefficients are combined by interpolation or by interpolating LSP coefficients or reflection coefficients.
Claim 20
Dependent Claim
163 words
Computer means arranged and programmed to carry out the method of coding a sampled speech signal, wherein the speech signals are divided into sequential frames and, for each current frame: a first set of linear prediction coding (LPC) coefficients which correspond to the coefficients of a linear filter and which are representative of short term redundancy in the current frame is generated; if the number of LPC coefficients in the first set of the current frame differs from the number in the first set of the preceding frame, a second expanded or contracted set of LPC coefficients is generated from the first set of LPC coefficients generated for the preceding frame, the second set containing a number of LPC coefficients equal to the number of LPC coefficients in said first set of the current frame; and the current frame is encoded using the first set of LPC coefficients of the current frame and the second set of LPC coefficients of the preceding frame.
Claim 21
Dependent Claim
163 words
Computer means arranged and programmed to carry out the method of coding a sampled speech signal, wherein the speech signals are divided into sequential frames and, for each current frame: a first set of linear prediction coding (LPC) coefficients which correspond to the coefficients of a linear filter and which are representative of short term redundancy in the current frame is generated; if the number of LPC coefficients in the first set of the current frame differs from the number in the first set of the preceding frame, a second expanded or contracted set of LPC coefficients is generated from the first set of LPC coefficients generated for the preceding frame, the second set containing a number of LPC coefficients equal to the number of LPC coefficients in said first set of the current frame; and the current frame is encoded using the first set of LPC coefficients of the current frame and the second set of LPC coefficients of the preceding frame.
Claim 22
Dependent Claim
19 words
A base station of a cellular telephone network comprising computer means ( 65 ) according to claim 18 .
Claim 23
Dependent Claim
14 words
A mobile telephone comprising computer means ( 64 ) according to claim 18 .
Claim 24
Dependent Claim
136 words
Computer means arranged and programmed to carry out the method of decoding a sampled speech signal which contains encoded linear prediction coding (LPC) coefficients for each frame of the signal, wherein for each current frame: the encoded signal is decoded to determine the number of LPC coefficients encoded for the current frame; where the number of LPC coefficients in a set of LPC coefficients obtained for the preceding frame differs from the number of LPC coefficients encoded for the current frame, said set of LPC coefficients of the preceding frame is expanded or contracted to provide a second set of LPC coefficients; and said second set of LPC coefficients of the preceding frame is combined with LPC coefficient data for the current frame to provide at least one set of LPC coefficients for the current frame.
Claim 25
Dependent Claim
136 words
Computer means arranged and programmed to carry out the method of decoding a sampled speech signal which contains encoded linear prediction coding (LPC) coefficients for each frame of the signal, wherein for each current frame: the encoded signal is decoded to determine the number of LPC coefficients encoded for the current frame; where the number of LPC coefficients in a set of LPC coefficients obtained for the preceding frame differs from the number of LPC coefficients encoded for the current frame, said set of LPC coefficients of the preceding frame is expanded or contracted to provide a second set of LPC coefficients; and said second set of LPC coefficients of the preceding frame is combined with LPC coefficient data for the current frame to provide at least one set of LPC coefficients for the current frame.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-03-12 | 2004-09-11 | 2005-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-03-12 | 2008-09-11 | 2009-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-03-12 | 2012-09-11 | 2013-03-13 | $7700.00 | Window Closed / Lapsed |