Vector quantization method, speech encoding method and apparatus
First Claim
1. A speech signal encoding method, in which a vector quantization technique is used to select an optimum code vector from fixed-dimension code vectors stored in a codebook of fixed-dimension code vectors for a variable-dimension input vector, the speech signal encoding method comprising:
- a step for determining prediction residuals of an input speech signal to be encoded;
a step for performing sinusoidal analytic encoding of the prediction residuals of the input speech signal to produce spectral harmonics data;
a step for determining a variable-dimension input code vector from the spectral harmonics data;
a step for converting the variable-dimension input code vector into a fixed-dimension input code vector;
a fixed/variable dimension conversion step for converting a plurality of the fixed-dimension code vectors read out from the codebook of fixed-dimension code vectors into a plurality of variable-dimension code vectors;
a selection step for selecting from the codebook of fixed-dimension code vectors an optimum code vector of the plurality of variable-dimension code vectors converted in the fixed/variable dimension conversion step which minimizes an error between the variable-dimension input code vector of the spectral harmonics data of the input speech signal and a fixed dimension code vector; and
a step for outputting an encoded speech signal.
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Abstract
The code vector search for vector-quantizing a variable-dimension input vector is to be improved in precision. Via a terminal are entered a variable number of data, that is a variable-dimension vector v, representing, for example, the amplitudes of spectral components of the harmonics of speech. The variable-dimension vector v is converted by a variable/fixed dimension conversion circuit into the vector x of a fixed dimension, such as 44-dimension vector, which is sent to a selection circuit. From plural fixed-dimension vectors, such a code vector as minimizes a weighted error is selected from a codebook. The code vector of fixed dimension obtained by the codebook is converted by a fixed/variable dimension converting circuit into the same variable dimension as that of the original variable-dimension vector v. The converted variable dimension code vector is sent to a variable-dimension selection circuit for selecting from the codebook such code vector as minimizes the weighted error from the input vector v.
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Citations
16 Claims
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1. A speech signal encoding method, in which a vector quantization technique is used to select an optimum code vector from fixed-dimension code vectors stored in a codebook of fixed-dimension code vectors for a variable-dimension input vector, the speech signal encoding method comprising:
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a step for determining prediction residuals of an input speech signal to be encoded; a step for performing sinusoidal analytic encoding of the prediction residuals of the input speech signal to produce spectral harmonics data; a step for determining a variable-dimension input code vector from the spectral harmonics data; a step for converting the variable-dimension input code vector into a fixed-dimension input code vector; a fixed/variable dimension conversion step for converting a plurality of the fixed-dimension code vectors read out from the codebook of fixed-dimension code vectors into a plurality of variable-dimension code vectors; a selection step for selecting from the codebook of fixed-dimension code vectors an optimum code vector of the plurality of variable-dimension code vectors converted in the fixed/variable dimension conversion step which minimizes an error between the variable-dimension input code vector of the spectral harmonics data of the input speech signal and a fixed dimension code vector; and a step for outputting an encoded speech signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A speech signal encoding method in which an input speech signal is divided on a time axis in terms of pre-set encoding units and encoded in terms of the pre-set encoding units, the method comprising:
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a step of finding spectral components of harmonics of the input speech signal by sinusoidal analysis of a signal derived from the input speech signal; and a step of vector quantizing encoding-unit-based spectral components of the harmonics as a variable-dimension input vector to be encoded, the vector quantizing step including a fixed/variable dimension conversion step for converting a fixed-dimension code vector read out from a codebook into a variable-dimension code vector; and a selection step for selecting from the codebook a variable-dimension code vector converted in the fixed/variable dimension conversion step which minimizes an error from a fixed-dimension input vector. - View Dependent Claims (10, 11, 12)
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13. A speech signal encoding apparatus for encoding an input speech signal, which is divided on a time axis in terms of pre-set encoding units, according to the pre-set encoding units, comprising:
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a prediction encoding circuit for finding short-term prediction residuals of the input speech signal; a sinusoidal analytic encoding circuit for processing the short-term prediction residuals with sinusoidal analytic encoding; a vector quantization circuit for performing vector quantization of spectral components of harmonics of the input speech signal as a variable-dimension input vector wherein the vector quantization circuit includes a fixed/variable dimension conversion circuit for converting a fixed-dimension code vector read out from a codebook into a variable-dimension code vector and a selection circuit for selecting from the codebook a variable-dimension code vector which minimizes an error from a fixed-dimension input vector; and a terminal for outputting an encoded speech signal. - View Dependent Claims (14, 15, 16)
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Specification