US5682407A
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Voice coder for coding voice signal with code-excited linear prediction coding
Assignee: Renesas Electronics Corp
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Filing: 1996-04-01
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Granted: 1997-10-28
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Expires: 2016-04-01
Abstract
Abstract A voice coder for coding a speech signal at a low bit rate with high speech quality and improved efficiency for gain quantization according to code-excited linear prediction (CELP) coding. The voice coder has an LPC (linear prediction coding) analyzer for calculating LPC coefficients, a parameter quantizer for quantizing the LPC coefficients to output a quantized code CL, an adaptive codebook, a long-term predicting circuit for searching the adaptive codebook to determine a delay code CD and an adaptive code vector, an excitation codebook, an excitation codebook searching circuit for determining an optimum quantized code CS and an excitation vector, and a gain codebook searching circuit for outputting a gain code CG by determining quantized gains representing quantized vectors of gains of the adaptive code vector and the excitation vector. The gain codebook searching circuit has a plurality of gain codebooks each for storing quantized gains corresponding to one of searching ranges divided by predetermined ranges with respect to the value of a searching parameter, and gain codebook selector for selecting one of the gain codebooks depending on the value of the searching parameter. The gain code CG is determined by using the gain codebook selected by the gain codebook selector.
Inventors
- 👤 Keiichi Funaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 13:22
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/04; G10L19/08; G10L19/083; G10L2019/0001; G10L2019/0013
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
241 words
A voice coder comprising: speech analyzing means for analyzing a speech signal having a predetermined frame length to generate a short-term prediction code representing frequency characteristics of the speech signal; an adaptive codebook for storing adaptive code vectors; long-term predicting means for effecting long-term prediction to search for a delay code representing the periodicity of said speech signal using said short-term prediction code, and to search for an adaptive code vector corresponding to the delay code; an excitation codebook for storing excitation vectors which are quantized codes representing residual signals after the long-term prediction; excitation codebook searching means for searching said excitation codebook to determine an optimum quantized code using said short-term prediction code, and to determine an excitation vector corresponding to the optimum quantized code; and gain codebook searching means for determining a quantized gain vector representing quantized gain of said adaptive code vector and said excitation vector using said short-term prediction code; said gain codebook searching means comprising: a plurality of gain codebooks each for storing quantized gains corresponding to one of a plurality of searching ranges divided by predetermined ranges with respect to the value of a searching parameter; and gain codebook selecting means for selecting one of said gain codebooks depending on the value of the searching parameter; wherein an optimum quantized gain is searched for to determine a gain code using the gain codebook selected by said gain codebook selecting means and said short-term prediction code.
Claim 2
Dependent Claim
241 words
A voice coder comprising: speech analyzing means for analyzing a speech signal having a predetermined frame length to generate a short-term prediction code representing frequency characteristics of the speech signal; an adaptive codebook for storing adaptive code vectors; long-term predicting means for effecting long-term prediction to search for a delay code representing the periodicity of said speech signal using said short-term prediction code, and to search for an adaptive code vector corresponding to the delay code; an excitation codebook for storing excitation vectors which are quantized codes representing residual signals after the long-term prediction; excitation codebook searching means for searching said excitation codebook to determine an optimum quantized code using said short-term prediction code, and to determine an excitation vector corresponding to the optimum quantized code; and gain codebook searching means for determining a quantized gain vector representing quantized gain of said adaptive code vector and said excitation vector using said short-term prediction code; said gain codebook searching means comprising: a plurality of gain codebooks each for storing quantized gains corresponding to one of a plurality of searching ranges divided by predetermined ranges with respect to the value of a searching parameter; and gain codebook selecting means for selecting one of said gain codebooks depending on the value of the searching parameter; wherein an optimum quantized gain is searched for to determine a gain code using the gain codebook selected by said gain codebook selecting means and said short-term prediction code.
Claim 3
Dependent Claim
25 words
The voice coder according to claim 1, wherein said speech analyzing means comprises a linear predictive coding analyzer for calculating a linear predictive coding coefficient.
Claim 4
Dependent Claim
26 words
The voice coder according to claim 1, further comprising a weighting circuit for weighting said speech signal for auditory sensation based on said short-term prediction code.
Claim 5
Dependent Claim
32 words
The voice coder according to claim 1, further comprising a multiplexer for multiplexing said short-term prediction code, said delay code, said optimum quantized code and said gain code into a transmission signal.
Claim 6
Dependent Claim
17 words
The voice coder according to claim 1, wherein said searching parameter is extracted from said delay code.
Claim 7
Dependent Claim
58 words
The voice coder according to claim 5, wherein the number of said gain codebooks included in said gain codebook searching means is two and each of said gain codebooks is corresponding to one of two searching ranges divided depending on whether a code delay value corresponding to said delay code is larger or smaller than a predetermined value.
Claim 8
Dependent Claim
32 words
The voice coder according to claim 5, further comprising a multiplexer for multiplexing said short-term prediction code, said delay code, said optimum quantized code and said gain code into a transmission signal.
Claim 9
Dependent Claim
49 words
The voice coder according to claim 1, wherein said searching parameter is extracted from an energy quantized code representing a quantized energy of said speech signal, said gain codebook searching means comprising energy quantizing means for quantizing the energy of said speech signal to generate said energy quantized code.
Claim 10
Dependent Claim
26 words
The voice coder according to claim 8, wherein said speech signal whose energy is to be quantized is a signal which is weighted for auditory sensation.
Claim 11
Dependent Claim
59 words
The voice coder according to claim 8, wherein the number of said gain codebooks included in said gain codebook searching means is two and each of said gain codebooks is corresponding to one of two searching ranges divided depending on whether a coded energy value corresponding to said energy quantized code is larger or smaller than a predetermined value.
Claim 12
Dependent Claim
36 words
The voice coder according to claim 8, further comprising a multiplexer for multiplexing said short-term prediction code, said delay code, said optimum quantized code, said gain code and said energy quantized code into a transmission signal.
Claim 13
Dependent Claim
53 words
The voice coder according to claim 1, wherein said searching parameter is extracted from an energy quantized code representing a quantized energy of said speech signal and said delay code, said gain codebook searching means comprising energy quantizing means for quantizing the energy of said speech signal to generate said energy quantized code.
Claim 14
Dependent Claim
80 words
The voice coder according to claim 12, wherein the number of said gain codebooks included in said gain codebook searching means is two and each of said gain codebooks is corresponding to one of two searching ranges divided depending on whether a coded energy value corresponding to said energy quantized code is larger or smaller than a first predetermined value and whether a code delay value corresponding to said delay code is larger or smaller than a second predetermined value.
Claim 15
Dependent Claim
36 words
The voice coder according to claim 12, further comprising a multiplexer for multiplexing said short-term prediction code, said delay code, said optimum quantized code, said gain code, and said energy quantized code into a transmission signal.
Claim 16
Dependent Claim
136 words
A voice coding system comprising said voice coder according to claim 4 and a voice decoder for decoding said transmission code, said transmission code containing said searching parameter; said voice decoder comprising a demultiplexer for extracting at least said searching parameter from said transmission code, and gain calculating means for calculating gains of the adaptive code vector and the excitation vector; said gain calculating means comprising a plurality of decoding gain codebooks which are identical to the gain codebooks in said gain codebook searching means, second gain codebook selecting means for selecting one of said decoding gain codebooks depending on the value of said searching parameter, and gain decoding means for decoding the gains of the adaptive code vector and the excitation vector using the decoding gain codebook selected by said second gain codebook selecting means.
Claim 17
Dependent Claim
130 words
A voice coding system comprising said voice coder according to claim 7 and a voice decoder for decoding said transmission code, said voice decoder comprising a demultiplexer for extracting at least said delay code and said gain code from said transmission code, and gain calculating means for calculating gains of the adaptive code vector and the excitation vector; said gain calculating means comprising a plurality of decoding gain codebooks which are identical to the gain codebooks in said gain codebook searching means, second gain codebook selecting means for selecting one of said decoding gain codebooks depending on said delay code, and gain decoding means for decoding the gains of the adaptive code vector and the excitation vector using the decoding gain codebook selected by said second gain codebook selecting means.
Claim 18
Dependent Claim
132 words
A voice coding system comprising said voice coder according to claim 11 and a voice decoder for decoding said transmission code, said voice decoder comprising a demultiplexer for extracting at least said gain code and said energy quantized code from said transmission code, and gain calculating means for calculating gains of the adaptive code vector and the excitation vector; said gain calculating means comprising a plurality of decoding gain codebooks which are identical to the gain codebooks in said gain codebook searching means, second gain codebook selecting means for selecting one of said decoding gain codebooks depending on said energy quantized code, and gain decoding means for decoding the gains of the adaptive code vector and the excitation vector using the decoding gain codebook selected by said second gain codebook selecting means.
Claim 19
Dependent Claim
139 words
A voice coding system comprising said voice coder according to claim 14 and a voice decoder for decoding said transmission code, said voice decoder comprising a demultiplexer for extracting at least said energy quantized code, said delay code, and said gain code from said transmission code, and gain calculating means for calculating gains of the adaptive code vector and the excitation vector; said gain calculating means comprising a plurality of decoding gain codebooks which are identical to the gain codebooks in said gain codebook searching means, second gain codebook selecting means for selecting one of said decoding gain codebooks depending on said energy quantized code and said delay code, and gain decoding means for decoding the gains of the adaptive code vector and the excitation vector using the decoding gain codebook selected by said second gain codebook selecting means.
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