Cryptography – Communication system using cryptography – Speech scrambler detail
Reexamination Certificate
1999-08-06
2003-12-02
Barrón, Gilberto (Department: 2132)
Cryptography
Communication system using cryptography
Speech scrambler detail
C704S206000, C704S219000, C704S221000, C380S276000, C714S755000, C375S229000
Reexamination Certificate
active
06658112
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to the field of digital receivers, in particular to the decoding of speech signals and more particularly to the improvement in audio quality by the detection of channel errors.
BACKGROUND OF THE INVENTION
With the emergence of new digital cellular-type telephones into the high volume commercial marketplace, voice compression algorithms are becoming commonplace. Due to the nature of voice coders and decoders, (i.e., vocoders) channel errors typically induce unusually offensive artifacts into a decoded speech signal. This is especially true when the spectral components of the speech signal becomes corrupted.
Line spectral pairs (LSPs) are typically used in modern vocoders because of their perceptual qualities and because LSPs are typically very well behaved. These characteristics allow for efficient coding and compression of the spectral content of a speech signal before its transmission across narrow band communication channels. The spectral content of voice signals is typically slowly evolving or changing. However, when a channel error corrupts an LSP parameter, it will usually cause dramatic and excessive changes in the spectral content of the signal. As a result, high-energy chirps or squawks are provided in the decoded signal which may be very offensive sounding.
In another example where digital voice information is encrypted, the receiver's loss of cryptographic synchronization results in improperly decrypted speech signals. The speech decoder in this case typically also provides offensive high-energy chirps and squawks until cryptographic synchronization is re-established.
Accordingly, what is needed are an apparatus and method for detecting offensive spectral errors. What is also needed are a method and apparatus for correcting offensive spectral errors. What is also needed are a method and apparatus that detects and corrects offensive spectral errors which result due to channel errors or the loss of crypto-synchronization.
REFERENCES:
patent: 4805193 (1989-02-01), McLaughlin et al.
patent: 5150401 (1992-09-01), Ashby, III et al.
patent: 5187745 (1993-02-01), Yip et al.
patent: 5255339 (1993-10-01), Fette et al.
patent: 5414796 (1995-05-01), Jacobs et al.
patent: 5600754 (1997-02-01), Gardner et al.
patent: 5636231 (1997-06-01), Huang et al.
patent: 5657420 (1997-08-01), Jacobs et al.
patent: 5668879 (1997-09-01), Ibaraki et al.
patent: 5754974 (1998-05-01), Griffin et al.
patent: 5774837 (1998-06-01), Yeldener et al.
patent: 5778338 (1998-07-01), Jacobs et al.
patent: 6205130 (2001-03-01), DeJaco
patent: 6330532 (2001-12-01), Manjunath et al.
patent: 0523979 (1993-01-01), None
patent: 9813941 (1998-04-01), None
“Method for Error Recovery of Line Spectral Frequencies”, L.K. Ong et al., Electronics Letters, Stevenage, Herts., GB, vol. 29, No. 6, Mar. 18, 1993, pp. 510-512.
“Quality Enhancement of Coded and Corrupted Speeches in GSM Mobile Systems Using Residual Redundancy”, T. Hindelang et al., IEEE International Conference on Acoustics, Speech, and Signal Processing, Los Alimitos, CA, Apr. 21, 1997, p. 259-262.
Barron David L.
Kennedy Paul Lopez
Yip William Chunhung
Barrón Gilberto
General Dynamics Decision Systems, Inc.
Hunton & Williams LLP
Nobahar A.
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