JPH0736486A - Speech coding device - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain natural speech when transmitting and decoding multiplexed data in which fluctuations in the harmonic frequency of speech are encoded. A fundamental frequency of an input voice signal is extracted by a fundamental frequency extractor 11, and a harmonic frequency detector 12 detects a harmonic frequency that is an integral multiple or an odd multiple of the fundamental frequency included in the input voice signal. The spectrum amplitude estimator 13 estimates the spectrum amplitudes of the fundamental frequency of the input voice signal and the harmonic frequencies of the integer multiple and the odd multiple from the harmonic frequency detector 12. The fundamental frequency extracted by the fundamental frequency extractor 11, the integer and odd multiple harmonic frequencies from the harmonic frequency detector 12, and the spectral amplitude parameter from the spectral amplitude estimator 13 are quantized by the multiplexer 14, The multiplexed multiplexed data (transmission code) is transmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speech coder used in a digital mobile radio or the like to encode fluctuations in the harmonic frequency of speech to obtain natural speech at the time of decoding.

[0002]

2. Description of the Related Art In recent years, in digital mobile radio equipment, efficient use of memory capacity in the equipment has been required. At the same time, it is required to maintain the quality of transmission voice that performs voice encoding processing and voice decoding processing.

FIG. 8 is a block diagram showing the structure of a conventional speech coding apparatus. In FIG. 8, the speech coding apparatus includes a fundamental frequency extractor 1 that extracts a fundamental frequency of an input speech signal, a harmonic amplitude calculator 2 that obtains an amplitude value of each harmonic based on the extracted fundamental frequency, It has a multiplexer 3 which quantizes the obtained fundamental frequency and the amplitude value data of each harmonic and outputs multiplexed data.

Next, the operation of this conventional configuration will be described. The fundamental frequency extractor 1 extracts the fundamental frequency (signal) from the input audio signal. The harmonic amplitude calculator 2 calculates an amplitude value of a harmonic (signal) that is an integral multiple of the basic frequency included in the extracted basic frequency signal. further,
Amplitude values at the fundamental frequency and harmonics that are integral multiples of the fundamental frequency obtained by the fundamental frequency extractor 1 and the harmonic amplitude calculator 2 are quantized and multiplexed by the multiplexer 3, and the multiplexed data (transmission code) Is output.

[0005]

In such a conventional speech coding apparatus as described above, since the harmonic frequency is always only an integral multiple of the fundamental frequency, the fundamental frequency and the harmonics of the integral multiple of the fundamental frequency. When the transmission code in which the amplitude value in (1) is multiplexed is decoded by the decoder on the receiving side, there is a drawback that it becomes unnatural speech like synthetic speech.

The present invention solves such a conventional problem, and can transmit multiplexed data (transmission code) in which fluctuations of the harmonic frequency of the voice are encoded, and when the data is decoded on the receiving side, it is natural. It is an object of the present invention to provide an excellent voicing device that can obtain various sounds.

[0007]

In order to achieve the above object, a speech coding apparatus of the present invention comprises a fundamental frequency extracting means for extracting a fundamental frequency of an input speech signal, and an integral multiple and an odd multiple of the fundamental frequency. Harmonic frequency detecting means for obtaining the harmonic frequency, spectral amplitude estimating means for estimating the spectral amplitude value of each harmonic obtained by the harmonic frequency detecting means, and harmonic frequencies that are integral multiples and odd multiples of the fundamental frequency And multiplexing means for quantizing the spectral amplitude values of the respective harmonics and outputting multiplexed data.

In this structure, the harmonic frequency detecting means includes an orthogonal transformer for obtaining the spectrum of the input voice signal,
An envelope analyzer that obtains the spectrum envelope of the input speech signal, and a harmonic classifier that divides the spectrum converted by the orthogonal transformer and the frequency of the spectrum envelope obtained by the envelope analyzer into multiple harmonic bands. , And a symmetric error minimizer that obtains a harmonic frequency for each harmonic band divided by the harmonic classifier.

[0009]

With such a configuration, the speech coding apparatus of the present invention quantizes and multiplexes the fundamental frequency, the harmonic frequencies of integer multiples and odd multiples, and the spectrum amplitude values of each harmonic. That is, the fluctuation of the harmonic frequency of the voice is encoded. Therefore, natural sound can be obtained when decoding is performed on the receiving side.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a speech coder according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a speech coding apparatus of the present invention. In FIG. 1, this speech encoding apparatus has a fundamental frequency extractor 11 for extracting a fundamental frequency of an input speech signal, and a harmonic frequency detector 12 for obtaining a harmonic frequency that is an integral multiple and an odd multiple of the fundamental frequency. is doing. Furthermore, this speech coding apparatus has a spectrum amplitude estimator 13 for estimating the spectrum amplitude value of each harmonic, and an integral multiple obtained by the fundamental frequency and harmonic frequency detector 12 obtained by the fundamental frequency extractor 11. And a multiplexor 14 which quantizes and multiplexes the harmonic frequency of an odd multiple and the spectrum amplitude value of each harmonic obtained by the spectrum amplitude estimator 13 and outputs the multiplexed data (transmission code). ing.

FIG. 2 is a block diagram showing a detailed configuration of the harmonic frequency detector 12. In FIG. 2, the harmonic frequency detector 12 includes an orthogonal transformer 15 that transforms data on the time axis into data on the frequency axis, an envelope analyzer 16 that analyzes the spectral envelope of input speech, and an input. It has a spectrum of a voice signal and a frequency classifier 17 that analyzes a frequency band for each harmonic from its envelope. Further, the harmonic frequency detector 12 includes a symmetric error minimizer 18 that finds a frequency that minimizes a symmetric error for each of the divided harmonic frequency bands, and a fluctuation calculation that calculates a difference from an integral multiple of the fundamental frequency. And a container 19.

Next, the operation of the configuration of this embodiment will be described. In FIG. 1, the fundamental frequency of the input audio signal is extracted by the fundamental frequency extractor 11. Further, the harmonic frequency detector 12 detects harmonic frequencies that are integer multiples and odd multiples of the fundamental frequency included in the input audio signal. A spectrum amplitude estimator 13 estimates the spectrum amplitudes of the fundamental frequency of the input voice signal and the harmonic frequencies of the integer multiple and the odd multiple from the harmonic frequency detector 12. The fundamental frequency extracted by the fundamental frequency extractor 11 and the integer and odd multiple harmonic frequencies from the fundamental frequency and harmonic frequency detector 12 and the spectral amplitude parameters from the spectral amplitude estimator 13 are quantized by the multiplexer 14. The multiplexed data (transmission code) that has been multiplexed is transmitted.

Next, the operation of the harmonic frequency detector 12 will be described. 3 is a spectrum diagram obtained by the orthogonal converter 15 in the harmonic frequency detector 12, and FIG. 4 is a spectrum envelope diagram obtained by the envelope analyzer 16 in the harmonic frequency detector 12. FIG. 5 is a diagram in which the frequency classifier 17 in the harmonic frequency detector 12 divides the frequency band for each harmonic in the spectrum curve. FIG. 6 shows the symmetric error minimizer 18 in the harmonic frequency detector 12. FIG. 4 is a diagram for explaining detection of a harmonic frequency that minimizes a symmetry error. Further, FIG. 7 is a diagram for explaining the operation of the symmetric error minimizer 18 in the harmonic frequency detector 12.

First, an orthogonal transformer 15 is used to convert an input voice signal.
Gives the spectrum shown in FIG. Further, the envelope analyzer 16 obtains the spectral envelope shown in FIG. In the frequency classifier 17, the two spectrum curves of the spectrum obtained by the orthogonal transformer 15 and the spectrum envelope obtained by the envelope analyzer 16 are divided into frequency bands 1 and 2 for each harmonic as shown in FIG. , 3, 4, 5, 6, ...

This frequency band 1, 2, 3, 4, 5, 6 ...
The symmetry error minimizer 18 detects the harmonic frequency that minimizes the symmetry error. The symmetric error obtained here is an error that occurs when the spectrum is folded back around a certain frequency as shown by the shaded portion in FIG. The harmonic frequency indicated by the points in FIG. 7 that minimizes the symmetry error detected by the symmetry error minimizer 18 and the deviation detector from the integral multiple of the fundamental frequency from the fundamental frequency extractor 11 in FIG. 1 are detected. It is detected at 19 and supplied to the multiplexer 14. Multiplexer 1
From 4, the multiplexed data (transmission code) in which the fluctuation of the harmonic frequency in the input audio signal is encoded is transmitted.

As described above, according to the present embodiment, it is possible to send multiplexed data (transmission code) in which the fluctuation of the harmonic frequency in the input audio signal is encoded. Therefore, natural sound can be obtained when the decoding is performed on the receiving side.

[0018]

As is apparent from the above description, the speech coding apparatus of the present invention quantizes and multiplexes the fundamental frequency and the harmonic frequencies of integer multiples and odd multiples and the spectrum amplitude values of the respective harmonics. ing. That is, since the fluctuation of the harmonic frequency of the voice is encoded, there is an effect that a natural voice can be obtained when the voice is decoded on the receiving side.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration in an embodiment of a speech encoding apparatus of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a harmonic frequency detector in FIG.

FIG. 3 is a spectrum diagram obtained by the orthogonal transformer in FIG.

4 is a spectrum envelope diagram obtained by the envelope analyzer in FIG. 2;

5 is an explanatory diagram in which the frequency band is divided for each harmonic in the spectrum curve by the frequency classifier in FIG.

6 is an explanatory diagram for explaining detection of a harmonic frequency that minimizes a symmetric error by the symmetric error minimizer in FIG. 2.

FIG. 7 is an explanatory diagram for explaining the operation of the symmetric error minimizer in FIG.

FIG. 8 is a block diagram showing the configuration of a conventional speech encoding device.

[Explanation of symbols]

 11 Fundamental Frequency Extractor 12 Harmonic Frequency Detector 13 Spectral Amplitude Estimator 14 Multiplexer 15 Orthogonal Transformer 16 Envelope Analyzer 17 Frequency Classifier 18 Symmetric Error Minimizer 19 Fluctuation Calculator

Claims (2)

[Claims] 1. A fundamental frequency extracting means for extracting a fundamental frequency of an input audio signal, a harmonic frequency detecting means for obtaining a harmonic frequency which is an integral multiple and an odd multiple of the fundamental frequency, and a harmonic frequency detecting means. Spectral amplitude estimation means for estimating the spectral amplitude value of each of the harmonics obtained,
A speech coding apparatus comprising: the fundamental frequency, an integer multiple and an odd multiple harmonic frequency, and multiplexing means for quantizing and multiplexing the spectrum amplitude value of each harmonic to output multiplexed data. 2. The harmonic frequency detecting means includes an orthogonal transformer for obtaining a spectrum of an input voice signal, an envelope analyzer for obtaining a spectrum envelope of the input voice signal, and a spectrum and an envelope transformed by the orthogonal transformer. Harmonic classifier that divides the frequency of the spectrum envelope obtained by the line analyzer into multiple harmonic bands, and finds the harmonic frequency for each harmonic band divided by the above harmonic classifier. The speech coding apparatus according to claim 1, further comprising: