US5884010A
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Linear prediction coefficient generation during frame erasure or packet loss
Assignee: Evonik Goldschmidt GmbH
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Filing: 1995-02-16
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Granted: 1999-03-16
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Expires: 2015-02-16
Abstract
Abstract A speech coding system robust to frame erasure (or packet loss) is described. Illustrative embodiments are directed to a modified version of CCITT standard G.728. In the event of frame erasure, vectors of an excitation signal are synthesized based on previously stored excitation signal vectors generated during non-erased frames. Specifically, the decoder generates and stores samples of a first excitation signal in a memory, and then, in response to a signal indicating a frame erasure, the decoder synthesizes a second excitation signal based on the previously stored samples. In particular, the second excitation is synthesized by correlating a first subset of the stored samples with a second subset thereof, identifying a set of stored excitation signal samples based on the correlation, and synthesizing the second excitation signal based on the identified samples. Finally, the decoder then filters the second excitation signal to synthesize a signal reflecting human speech.
Inventors
- 👤 Juin-Hwey Chen
- 👤 Craig Robert Watkins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 02:33
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/04; G10L19/08; G10L19/005; G10L19/12; G10L19/06; G10L2019/0001; G10L2019/0012
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
193 words
A method of synthesizing a signal reflecting human speech, the method for use by a decoder which experiences an erasure of input bits, the decoder including a first excitation signal generator responsive to said input bits and a synthesis filter responsive to an excitation signal, the method comprising the steps of: storing, in a memory, samples of a first excitation signal generated by said first excitation signal generator; responsive to a signal indicating the erasure of input bits, synthesizing a second excitation signal based on previously stored samples of the first excitation signal; and filtering said second excitation signal to synthesize said signal reflecting human speech; wherein the step of synthesizing a second excitation signal includes the steps of: correlating a first subset of samples stored in said memory with a second subset of samples stored in said memory, at least one of said samples in said second subset being earlier in said memory than any sample in said first subset; identifying a set of stored excitation signal samples based on said correlation of said first and second subsets; forming said second excitation signal based on said identified set of excitation signal samples.
Claim 2
Independent Claim
193 words
A method of synthesizing a signal reflecting human speech, the method for use by a decoder which experiences an erasure of input bits, the decoder including a first excitation signal generator responsive to said input bits and a synthesis filter responsive to an excitation signal, the method comprising the steps of: storing, in a memory, samples of a first excitation signal generated by said first excitation signal generator; responsive to a signal indicating the erasure of input bits, synthesizing a second excitation signal based on previously stored samples of the first excitation signal; and filtering said second excitation signal to synthesize said signal reflecting human speech; wherein the step of synthesizing a second excitation signal includes the steps of: correlating a first subset of samples stored in said memory with a second subset of samples stored in said memory, at least one of said samples in said second subset being earlier in said memory than any sample in said first subset; identifying a set of stored excitation signal samples based on said correlation of said first and second subsets; forming said second excitation signal based on said identified set of excitation signal samples.
Claim 3
Dependent Claim
33 words
The method of claim 1 wherein the step of forming said second excitation signal comprises copying said identified set of stored excitation signal samples for use as samples of said second excitation signal.
Claim 4
Dependent Claim
19 words
The method of claim 1 wherein said identified set of stored excitation signal samples comprises five consecutive stored samples.
Claim 5
Dependent Claim
20 words
The method of claim 1 further comprising the step of storing samples of said second excitation signal in said memory.
Claim 6
Dependent Claim
19 words
The method of claim 1 further comprising the step of determining whether erased input bits likely represent non-voiced speech.
Claim 7
Dependent Claim
50 words
The method of claim 1 wherein: the step of correlating comprises determining a time lag value between first and second subsets of samples corresponding to a maximum correlation; and the step of identifying a set of stored excitation signal samples comprises identifying said samples based on said time lag value.
Claim 8
Dependent Claim
48 words
The method of claim 6 further comprising the steps of: in accordance with a test, determining whether erased input bits likely represent a signal of very low periodicity; and if erased input bits are determined to represent a signal of very low periodicity, modifying said time lag value.
Claim 9
Dependent Claim
21 words
The method of claim 7 wherein said test comprises comparing a weight of a signal tap pitch predicator to a threshold.
Claim 10
Dependent Claim
16 words
The method of claim 7 wherein said test comprises comparing the maximum correlation to a threshold.
Claim 11
Dependent Claim
20 words
The method of claim 7 wherein the step of modifying said time lag value comprises incrementing said time lag value.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2002-03-15 | 2002-09-14 | 2003-03-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-03-15 | 2006-09-14 | 2007-03-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-03-15 | 2010-09-14 | 2011-03-16 | $7700.00 | Window Closed / Lapsed |