Voice coder system

Assignee: NEC Corp

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Filing: 1994-01-21

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Granted: —

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Expires: 2014-01-21

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Abstract

Abstract A voice coder system capable of coding at low bit rates under 4.8 kb/s with high speech quality. Speech signals are divided into frames and further divided into subframes. A spectral parameter calculator part (200) calculates spectral parameters representing spectral feature of the speech signals in at least one subframe and a spectral parameter quantization part (210) quantizes the spectral parameters of at least one subframe preselected by using a plurality of stages of quantization code books (211) to obtain quantized spectral parameters. A mode classifier part (245) classifies the speech signals in the frame into a plurality of modes by calculating predetermined feature amounts of the speech signals and a weighting part (230) weights perceptual weights to the speech signals by using the spectral parameters obtained in the spectral parameter calculator part to obtain weighted signals. An adaptive code book part (300) obtains pitch parameters representing pitch periods of the speech signals in a predetermined mode by using the mode classification in the mode classifier part, the spectral parameters obtained in the spectral parameter calculator part, the quantized spectral parameters obtained in the spectral parameter quantization part and the weighted signals and a excitation quantization part (350) searches a plurality of stages of excitation code books and a gain code book (355) by using the spectral parameters, the quantized spectral parameters, the weighted signals and the pitch parameters to obtain quantized excitation signals of the speech signals.

Inventors

👤 Kazunori C/O Nec Corporation Ozawa

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-11-02 21:54

CPC Classifications

G; G10; G10L; G10L19/00; G10L19/04; G10L19/08; G10L19/083; G10L19/06; G10L19/07; G10L19/12; G10L19/16; G10L19/18; G10L2019/0001; G10L2019/0002; G10L2019/0004; G10L2019/0005

Claims Analysis

Total Claims: 5

Claim 1

Independent Claim 224 words

A voice coder system, comprising: spectral parameter calculator means for dividing input speech signals into frames and further dividing the speech signals into a plurality of subframes at every predetermined timing, and calculating spectral parameters representing spectral feature of the speech signals in at least one subframe; spectral parameter quantization means for quantizing the spectral parameters of at least one subframe preselected by using a plurality stages of quantization code books to obtain quantized spectral parameters; mode classifier means for classifying the speech signals in the frame into a plurality of mode by calculating predetermined feature amounts of the speech signals; weighting means for weighting perceptual weights to the speech signals depending on the spectral parameters obtained in the spectral parameter calculator means to obtain weighted signals; adaptive code book means for obtaining pitch parameters representing pitches of the speech signals corresponding to the modes depending on the mode classification in the mode classifier means, the spectral parameters obtained in the spectral parameter calculator means, the quantized spectral parameters obtained in the spectral parameter quantization means and the weighted signals; and excitation quantization means for searching a plurality of stages of excitation code books and a gain code book depending on the spectral parameters, the quantized spectral parameters, the weighted signals and the pitch parameters to obtain quantized excitation signals of the speech signals.

Claim 2

Dependent Claim 53 words

The voice coder system as claimed in claim 1, wherein the mode classifier means includes means for calculating pitch prediction distortions of the subframes from the weighted signals obtained in the weighting means and means for executing the mode classification by using a cumulative value of the pitch prediction distortions throughout the frame.

Claim 3

Dependent Claim 42 words

The voice coder system as claimed in claim 1 or 2, wherein the spectral parameter quantization means includes means for switching the quantization code books depending on the mode classification result in the mode classifier means when the spectral parameters are quantized.

Claim 4

Dependent Claim 48 words

The voice coder system as claimed in any of claims 1 to 3, wherein the excitation quantization means includes means for switching the excitation code books and the gain code book depending on the mode classification result in the mode classifier means when the excitation signals are quantized.

Claim 5

Dependent Claim 39 words

The voice coder system as claimed in any of claims 1 to 4, wherein in the excitation quantization means, at least one stage of the excitation code books includes at least one code book having a predetermined decimation rate.

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