Speech coding system and method including adaptive finite impulse response filter
First Claim
Patent Images
1. A spectral frequency quantizer comprising:
- a digital signal processor adapted to operate, at least in part, as a finite impulse response filter, said finite impulse response filter comprising an input for receiving line spectral frequencies, and an output for providing smoothed quantized line spectral frequencies, said finite impulse response filter characterized by the transfer function;
space="preserve" listing-type="equation">H(z)=0.5+Δ
+(0.5-Δ
)z.sup.-1 wherein Δ
is determined by the formula;
space="preserve" listing-type="equation">Δ
=min(0.5,γ
|ƒ
(n)-ƒ
(n-1)|) and wherein ƒ
(n) denotes a present input to said finite impulse response filter, and wherein ƒ
(n-1) denotes a previous input to said finite impulse response filter.
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Abstract
A speech coding system and associated method relies on a speech coder and a speech decoder. The speech coder provides speech spectrum information, including Line Spectral Frequency (LSF) information, for respective frames of speech. The LSF information is provided to the speech decoder. The speech decoder includes an LSF smoothing filter comprising an adaptive finite impulse response filter for averaging consecutive LSFs which are similar. Consecutive LSFs which are dissimilar are not averaged. The system and method causes a reduction in the shaky quality of synthesized speech without causing a corresponding decrease in the clarity of the synthesized speech.
53 Citations
1 Claim
-
1. A spectral frequency quantizer comprising:
-
a digital signal processor adapted to operate, at least in part, as a finite impulse response filter, said finite impulse response filter comprising an input for receiving line spectral frequencies, and an output for providing smoothed quantized line spectral frequencies, said finite impulse response filter characterized by the transfer function;
space="preserve" listing-type="equation">H(z)=0.5+Δ
+(0.5-Δ
)z.sup.-1wherein Δ
is determined by the formula;
space="preserve" listing-type="equation">Δ
=min(0.5,γ
|ƒ
(n)-ƒ
(n-1)|)and wherein ƒ
(n) denotes a present input to said finite impulse response filter, and wherein ƒ
(n-1) denotes a previous input to said finite impulse response filter.
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Specification
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- Resources
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Current AssigneeLockheed Martin Corporation (Martin Marietta Corporation)
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Original AssigneeLockheed Martin Corporation (Martin Marietta Corporation)
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InventorsGrabb, Mark Lewis, Zinser, Richard Louis Jr., Koch, Steven Robert, Brooksby, Glen William
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Primary Examiner(s)Hudspeth, David R.
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Assistant Examiner(s)Smits, Talivaldis Ivars
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Application NumberUS09/114,658Time in Patent Office715 DaysField of Search704/219US Class Current704/219CPC Class CodesG10L 19/06 Determination or coding of ...G10L 19/07 Line spectrum pair [LSP] vo...
