Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Patent
1998-09-18
2000-08-15
Hudspeth, David R.
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
704224, 704225, G01L 1912, G01L 1914
Patent
active
061049921
ABSTRACT:
A multi-rate speech codec supports a plurality of encoding bit rate modes by adaptively selecting encoding bit rate modes to match communication channel restrictions. In higher bit rate encoding modes, an accurate representation of speech through CELP (code excited linear prediction) and other associated modeling parameters are generated for higher quality decoding and reproduction. The encoder applies adaptive gain reduction to optimize selection of appropriate gain contributions from the adaptive and fixed codebooks. Specifically, the encoder uses a first target signal to identify a contribution (a best code vector and a gain) from the adaptive codebook. Thereafter, a contribution from the fixed codebook is selected. The gain associated with the adaptive codebook contribution is then reduced by a factor, and the gain contribution from the fixed codebook is searched a second time, permitting fine tuning of the overall contribution. The gain reduction factor applied is adapted by considering both the encoding bit rate and a normalized correlation between the original target signal and the filtered signal from the adaptive codebook.
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Gao Yang
Su Huan-Yu
Conexant Systems Inc.
Hudspeth David R.
Lerner Martin
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