JPH08307366A - Speech coding device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a speech coding apparatus which is inexpensive and capable of transmitting a DTMF signal with little distortion. The speech encoding circuit 21 receives a DTMF signal and a speech signal as input signals and generates a parameter indicating a level for each frequency. The DTMF detection circuit 22 determines whether the input signal is a DTMF signal or a voice signal based on the parameter. In accordance with the result of this determination, the switching circuit 12a selectively sets the parameters to the DTMF encoding circuit 2
3 and the audio encoding circuit 24.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a DTMF (Dual).
The present invention relates to a speech coding apparatus having a Tone Multi-Frequency (push button dial signal) detection circuit and having an in-band transmission function.

[0002]

2. Description of the Related Art Generally, a digital mobile communication system uses a communication line used for transmitting a digitally encoded voice signal when transmitting a DTMF signal. Such a transmission method is generally called in-band transmission.

When in-band transmission of a DTMF signal is performed, only a feature point as voice is extracted using a high compression encoder, and then the in-band transmission of the DTMF signal is performed.
When the signal is decoded and reproduced, the DTMF signal is distorted, and for example, the telephone network switch cannot recognize it as the DTMF signal. For this reason, in general, an encoder is provided separately from the speech encoder so that the DTMF signal is encoded and transmitted in-band, and the decoding side reproduces the DTMF signal from the encoded DTMF signal.

Here, referring to FIG. 5, a conventional DTMF is used.
A speech coder including a signal detection circuit will be described.

The illustrated speech coding apparatus is provided with an input terminal 11, to which digital speech data and DTMF signals are given as input signals. DTM
The F signal detection circuit 12 detects whether or not the input signal is the DTMF signal, and if the input signal is the DTMF signal,
A DTMF detection signal (for example, a high level signal) is output (for this DTMF detection circuit 12, see Japanese Patent Laid-Open No. 7-
Since it is described in detail in Japanese Patent No. 87532, the description thereof will be omitted). Then, this DTMF detection signal is given to the switching circuit 12a. Upon receiving the DTMF detection signal, the switching circuit 12a receives the input terminal 11 and the DTMF encoding circuit 13
And connect. That is, the DTMF signal is given to the DTMF encoding circuit 13. The DTMF encoding circuit 13 encodes the DTMF signal and sends it as an encoded DTMF signal.

On the other hand, in the state where the DTMF detection signal is not received, the switching circuit 12a has the input terminal 11 and the voice encoding circuit 1.
4 and are connected. That is, the digital audio data is given to the audio encoding circuit 14. The voice encoding circuit 14 encodes the digital voice data and sends it as an encoded voice signal.

The above-mentioned DTMF detection signal is output to the output selection circuit 1.
5 is also given, when receiving the DTMF detection signal,
The output selection circuit 15 selects the DTMF encoding circuit 13. On the other hand, when the DTMF detection signal is not received, the output selection circuit 15 selects the speech coding circuit 14. As a result, the coded DTMF signal and the coded audio signal are selectively output by the output selection circuit 15 and output from the output terminal 16.

[0008]

By the way, in the above speech coding circuit, it is necessary to independently detect the DTMF signal prior to speech coding. Therefore, the processing amount in the DTMF detection circuit is significantly increased, and the processing capacity of the DTMF detection circuit must be increased. That is, there is a problem that the entire speech coding apparatus becomes expensive.

An object of the present invention is to provide a speech coding apparatus which is inexpensive and can transmit a DTMF signal with little distortion.

[0010]

According to the present invention, a DTM
A voice encoding device for receiving an F signal and a voice signal as input signals, encoding the input signals and transmitting in-band,
First coding means for generating a coded DTMF signal in which a DTMF signal is coded, second coding means for generating a coded voice signal in which a voice signal is coded, and generation in accordance with an input signal The parameter indicating the level for each frequency is received, it is determined whether the input signal is a DTMF signal or a voice signal based on the parameter, and the parameter is selectively set to the first and second parameters according to the determination result. And a determining means for giving the encoding means to the encoding means.

[0011]

The DTMF detection circuit of the DTMF detection circuit receives the parameter representing the level for each frequency generated according to the input signal and determines whether the input signal is the DTMF signal or the voice signal based on the parameter. The configuration is simple, the entire speech coding apparatus can be made inexpensive,
Moreover, the DTMF signal with less distortion can be transmitted.

[0012]

EXAMPLES The present invention will be described below with reference to examples.

Referring to FIG. 1, in the speech coding apparatus shown in the figure, the same components as those of the speech coding apparatus shown in FIG. 5 are designated by the same reference numerals. The speech coding apparatus includes a first speech coding circuit 21, and the first speech coding circuit 21 is connected to the input terminal 11 and the DTMF detection circuit 22. Digital voice data or a DTMF signal is given as an input signal to the first voice encoding circuit 21 via the input terminal 11.

Referring also to FIG. 2, the first speech coding circuit 21 includes a speech power extraction circuit 21a, a speech power normalization circuit 21b, and a Fourier transform circuit 21c. The audio power extraction circuit 21a extracts the audio power from the input signal and supplies it as the audio power signal to the audio power normalization circuit 21b. Voice power normalization circuit 21b
Then, the audio power signal is normalized and a normalized signal is output. The normalized signal is the Fourier transform circuit 21c.
Fourier transformed by the parameter (frequency level signal)
Is given to the DTMF detection circuit 22.

The DTMF detection circuit 22 is a tone selection circuit 2
2a and level determination circuit 22b. The tone selection circuit 22a obtains the frequency power corresponding to each tone based on the parameter and selects the tone having the highest power in each of the high group and the low group as the high group selected tone and the low group selected tone. The level determination circuit 22b determines the levels of the high group selection tone and the low group selection tone, and determines whether or not the input signal is the DTMF signal based on the determination result (see FIG. 3 for voice and DTMF signals). Shows frequency characteristics). When the determination result is the DTMF signal, the DTMF detection circuit 22 outputs the DTMF detection signal. The DTMF detection signal is sent to the switching circuit 1
Given to 2a.

Upon receiving the DTMF detection signal, the switching circuit 1
2a connects the first speech encoding circuit 21 and the DTMF encoding circuit 23. That is, the parameter of the DTMF signal is given to the DTMF encoding circuit 23. D
The TMF encoding circuit 13 outputs the encoded DTMF signal according to the parameter of the DTMF signal.

On the other hand, in the state where the DTMF detection signal is not received, the switching circuit 12a is connected to the first speech coding circuit 21 and the second speech coding circuit 21.
Connected to the voice encoding circuit 24. That is, the parameter of the digital voice data is the second voice encoding circuit 24.
Will be given to.

Here, also referring to FIG. 4, the second speech encoding circuit 24 includes first and second arithmetic circuits 24a and 24a.
b, a quantization coding circuit 24c, and a multiplexing circuit 24d. When the parameters of the digital voice data are received, the first arithmetic circuit 24a obtains the side information. Then, the second arithmetic circuit 24b obtains the bit allocation and the quantization step as the quantization information based on the side information and gives it to the quantization coding circuit 24c. The quantization coding circuit 24c quantizes and codes the digital audio data based on the quantized information and outputs it as coded audio data. The multiplexing circuit 24d multiplexes the side information and the encoded voice data and outputs the multiplexed voice data as multiplexed voice data.
That is, in this embodiment, the second speech coding circuit 23 uses adaptive transform coding (Adaptive Transform).
rm Coding).

The above-mentioned DTMF detection signal is output to the output selection circuit 1.
5 is also given, when receiving the DTMF detection signal,
The output selection circuit 15 selects the DTMF encoding circuit 23. On the other hand, when the DTMF detection signal is not received, the output selection circuit 15 selects the second speech coding circuit 24.
As a result, the coded DTMF signal and the multiplexed voice data described above are selectively output by the output selection circuit 15 and output from the output terminal 16.

[0020]

As described above, according to the present invention, the parameter indicating the level for each frequency generated according to the input signal is received, and the input signal is changed to the DTM based on this parameter.
Since it is determined whether the signal is the F signal or the voice signal, the configuration of the DTMF detection circuit is simplified, and there is an effect that the entire voice encoding device can be made inexpensive, and further, distortion is small. There is an effect that the DTMF signal can be transmitted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a speech coding apparatus according to the present invention.

2 is a block diagram showing in detail a first encoding circuit and a DTMF detection circuit shown in FIG. 1. FIG.

FIG. 3 is a diagram showing frequency characteristics of voice and DTMF signals.

FIG. 4 is a block diagram showing in detail an example of a second encoding circuit shown in FIG.

FIG. 5 is a block diagram showing a conventional speech encoding device.

[Explanation of symbols]

 11 input terminal 12,22 DTMF detection circuit 13,23 DTMF coding circuit 14,21,24 speech coding circuit 15 output selection circuit 16 output terminal

Claims (3)

[Claims] 1. A voice coder for receiving a DTMF signal and a voice signal as input signals and encoding the input signals for in-band transmission, wherein the DTMF signal is encoded to generate a coded DTMF signal. 1 encoding means,
Second encoding means for generating an encoded audio signal in which the audio signal is encoded, and a parameter representing a level for each frequency generated according to the input signal, and receiving the input signal based on the parameter A determining unit that determines whether the signal is the DTMF signal or the audio signal and selectively applies the parameter to the first and second encoding units according to the determination result. Audio coding device. 2. The speech coding apparatus according to claim 1, wherein the determining means obtains the frequency power corresponding to each tone based on the parameter and has the highest power in each of the high group and the low group. A tone selection circuit that selects a tone as a high group selection tone and a low group selection tone,
The levels of the high group selection tone and the low group selection tone are determined, and the input signal is the DTM based on the determination result.
And a level determination circuit for determining whether or not the signal is an F signal. 3. The speech coding apparatus according to claim 3, wherein the determining means further selectively sets the parameter to the first and second encodings in accordance with the determination made by the level determining circuit. A speech coding apparatus, characterized in that it is provided with a switching circuit for giving the means.