JP2838946B2 - Multipoint voice communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to voice communication between voice communication between terminals located at remote locations where the coding and decoding characteristics of the communicating terminals are not uniform. Things.

[0002]

2. Description of the Related Art FIG. 11 shows an example of a configuration of a conference trunk for realizing a conventional multipoint voice communication system. This figure is described in JP-A-63-191453, and the number of conference participants is three. The signals from some terminals consist of 8-bit code words and are processed with PCM signals having a sampling frequency of 8 KHz. In addition, some terminals have a sampling frequency of 16 KHz and an ADPCM (Adaptive) having a word length of up to 4 bits.
Differential PCM-Adaptive Differential PCM
−) Only the signal shall be processed.

In FIG. 11A, one first conference subscriber is provided with transcoders C11 and C1.
2 and decoding converters (trans decoders) D11, D12
Is arranged. The same applies to the first and third conference participants and the transcoders C21, C22, C31, C3.
2 and transformer decoders D21, D22, D31, D3
2 is also arranged. The transcoders C11, C21, and C31 convert the non-linearly coded 8-bit PCM word into a 14-bit linear code word. At the same time, the sampling frequency is increased to 16 KHz by interpolation and oversampling. The transcoders C12, C22, and C32 also convert the ADPCM word into a 14-bit linear code word. The sampling frequency is again 16 KHz. 16 KHz by the trans decoders D11, D21 and D31
A 14-bit long linear codeword having a sampling frequency of ??? is filtered, undersampled, and re-quantized to form a non-linearly encoded 8-bit PCM word with a sampling frequency of 8 KHz. Similarly, the trans-decoders D12, D22 and D32 eliminate the effects of the coders C12, C22 and C32, and
An ADPCM word is formed from a bit-length linear code word.
Transcoders and transdecoders are correspondingly referred to in the following sense. That is, when the trans decoder is connected downstream of the transcoder, the trans decoder is called correspondingly in the sense that it immediately matches the input signal of the transcoder.

[0004] One of the transcoders C11 or C12 is connected to the input side of the addition circuit AD via a changeover switch UE1. Similarly, each of the transcoders C2
1, one of C22 to C31, C32 is connected to the changeover switches UE2, UE3. Trans decoder D1
1, and the input side of D12 is connected to the output side of the adder circuit AD90, and the trans decoders D21, D22 and D22
The input sides of D31 and D32 are similarly connected. One output side of both transformer decoders D11 and D12 is
It is connected to the output terminal A1 via another changeover switch UA1. Then, an output signal for the first subscriber is transmitted via the changeover switch. The same holds for the trans decoders D21, D22 to D31, D32, the changeover switches UA2 to UA3, and the terminals A2 to A3, respectively.

When a conference connection is established, signals transmitted from conference participants are applied to terminals E1 to E3. For example,
The first subscriber sends the information as an ADPCM word having the above format. By a control circuit not shown in FIG. 11 , the transcoder C12 is connected to the addition circuit AD90 via the changeover switch UE1, and the transdecoder D12 is connected to the terminal A1. Similarly, for example, the information is stored in A having the same format as above.
The transcoder C22 and the transdecoder D22 are also selected for the second subscriber transmitting and receiving the DPCM signal. The third subscriber is, for example, 8KH
Assume that a non-linearly coded PCM signal consisting of an 8-bit code word with a sampling frequency of z is being processed. For the third subscriber, therefore, by the control circuit, the transcoder C31 is connected to the addition circuit AD90 and the transdecoder D31 is connected to the terminal A3. Adder circuit AD 90 forms a partial sum of the input signals.
That is, the output signal of the subscriber circuit AD, which is intended for one subscriber, is formed from the sum of the input signals of two other subscribers. In the case of the present example, the second,
The two 14-bit linear codes of the third subscriber, just applied to the adder circuit, are added and the sum is transmitted to the output for the first subscriber.

[0006] According to the configuration of FIG. 11 (b), each transport decoder and each transcoder C11~C32 D11~D
32 features are the same as FIG. 11 (a), the first adder circuit 91
And an intermediate transcoder SC1 93 and an intermediate transcoder SC2 94, respectively. Thus, each subscriber receives the sum signal of all conference subscribers that match the respective encoding scheme.

A conventional multipoint voice communication system has a configuration as shown in FIG. 8, and an input signal to a multipoint conference apparatus is a non-linear PCM having an 8 kHz sampling frequency.
Word or an ADPCM word with a 16 KHz sampling frequency, the transcoders C11, C2
1, C31 and C12, C22, C32 all convert the output signal into a 14-bit linear codeword having a sampling frequency of 16 KHz. Therefore, the input terminals E1, E2. Even if all the audio signals input from E3 are signals having a sampling frequency of 8 KHz, they are expanded to 14-bit linear codewords by the conventional method, and then interpolated and oversampled to 16 bits.
It will be converted to a sampling frequency of KHz.
At least, unless each subscriber is the same coding scheme
It becomes necessary to use a plurality of adding circuits.

[0008]

In the conventional multipoint voice communication system, a decoder corresponding to the coding system of the connected subscriber terminal, an encoder, a selection switch, and a coding system are supported. Adder circuits are required, and these adder circuits require simultaneous use of adders of all coding schemes being communicated at the time of communication between terminals of different coding schemes , or higher-order codes. Change to long unified code
In other words, there is a problem that it is necessary to use an addition circuit having a large circuit scale .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a terminal device connected to a multipoint voice communication conference device is provided with an encoding device determined by a frequency band and an encoding speed of the terminal device. It is an object of the present invention to obtain a flexible and efficient voice communication apparatus by selecting an adding means depending on the case without being fixed to an adding means limited to a device and a decoder.

[0010]

[MEANS FOR SOLVING THE PROBLEMS] A multipoint system according to the present invention
The voice communication device transmits signals from three or more terminals.
Wavelength band and coding rate are detected as path determination factors.
Constant circuit and wideband decoder for decoding the transmission signal from the terminal
And the narrowband decoder, and the audio signal decoded by each of these decoders
Signal to the frequency band of the output of the other decoder.
And a band converter for converting and decoding these signals.
The input voice signal to the input side broadband voice communication path and the input side
Output to the input side voice communication path including the
Decoding means provided for each terminal having a decoding path, and input
The audio signal component from the side broadband voice communication path
Of the other terminals and add them to the received signal
A broadband addition circuit that outputs to the output side broadband communication path, and an input
The audio signal component from the side narrow-band voice communication channel
Of the other terminals and add them to the received signal
A narrow band addition circuit that outputs to the output side narrow band communication path, and a wide band
The output side wide band communication is provided with a band encoder and a narrow band encoder.
Multiple output voices including talk channel and output narrowband voice communication channel
Encode the added received signal obtained by selecting from the communication channel
Each terminal has multiple encoding paths to output to the terminal.
Encoding means, and the terminal of the terminal detected by the determination circuit.
Broadband addition times based on predetermined rules using path determination factors
Path or narrowband adder or both
Then, in accordance with the selected addition circuit, a recovery is performed for each of the terminals.
The decoding path in the encoding means and the encoding path in the encoding means.
Select, each with multiple input voice channels and multiple outputs
Selector control means for controlling connection with the side voice communication path;
With. Furthermore, each decoding means provided for each terminal
Of audio signals to be output to multiple
Converts the bell to almost the same level, provided for each band
Level adjusting means was provided. Or each terminal with 3 or more points
Factors that determine the frequency band and coding rate of the transmitted signal
And a decoding circuit to detect the signal and decode the transmission signal from the terminal
Narrowband decoder that transmits signals from terminals to multiple
A wideband decoder for decoding in several bands.
The audio signal decoded by the device corresponds to each frequency band
Multiple decoding paths to output to multiple input voice communication paths
With a decoding means provided for each terminal, the input-side audio communication
High frequency signal components in multiple frequency bands from speech channel
Is added to each terminal other than the terminal and
A high-frequency signal output to the output high-frequency voice communication path as a received signal
Calculation circuit and multiple frequency bands from the input voice communication path.
Of the low frequency component of each terminal other than the terminal concerned.
And output low-frequency sound as a reception signal to the terminal.
A low-frequency addition circuit that outputs to the communication path and an output-side high-frequency voice call
Output of the high-frequency addition circuit obtained from the path and the output-side low-frequency addition circuit
The low-band addition circuit output obtained from the output of the
And then combine the wideband encoder and the output side low
The output of the low-frequency addition circuit obtained from the low-frequency voice communication channel
And a corresponding narrowband coder
Select a signal path corresponding to the signal path of the
Encoding means provided for each terminal to obtain an encoded output,
Predetermined using the route determination factor of the terminal detected by the judgment circuit
Either the high-frequency addition circuit or the low-frequency addition circuit
Select either or both to correspond to the selected adder circuit.
A decoding path in the decoding means for each terminal;
Select the encoding path in the
Control the connection between the call path and multiple output voice call paths,
Selector control means. In addition, the decoding means
Is applied to the output of the wideband decoder based on the output of the narrowband decoder.
Output a signal divided into multiple high and low frequency bands
A narrow band decoder to replace the narrow band decoder output.
Output of the bandwidth converter to the input side voice communication path
I tried to force. Still further, the low-frequency addition circuit is
An area voice addition circuit was used.

[0011]

In the multipoint voice communication apparatus according to the present invention, the frequency band and the coding speed of the voice signal from each terminal are monitored, the coding form is selected from the result and a predetermined rule, and the corresponding addition means is provided. To be elected. Each terminal communicates with the addition means, the decoder and the encoder. In the invention of claim 2,
Since the level of the audio signal fluctuates at each transmission / reception point, after the decoding process, the level becomes relatively the same level and is input to the adding means. According to the third aspect of the present invention, the low-frequency signal addition means is not particularly provided in the multipoint voice communication apparatus, the conventional voice addition circuit of the telephone band is shared, and the low-frequency voice signal is input to the telephone band voice addition circuit. You.

[0012]

[Embodiment 1] FIG. 1 is a diagram showing an embodiment of a voice processing unit including a voice coding, decoding and voice adding unit of a multipoint voice communication apparatus using the present invention. In the figure, it is assumed that there are two types of input voice: wideband voice and narrowband voice. In the figure,
Reference numeral 5 denotes a determination circuit, and reference numeral 6 denotes a selector control unit . 11-13
Is a decoding means, which is used as a decoding circuit in the following embodiments.
You. 21 to 23 are encoding means, and in the following embodiments,
It is an encoding circuit. 31 to 33 are input side switches,
41-43 the output side switch, 71 N-1 for adding at N-1 addition system in this embodiment in wideband speech summing circuit
An adder is used. Reference numeral 72 denotes a narrow-band voice addition circuit .
In the embodiment, the N-1 adder that performs addition by the N-1 addition method is
Used. 81 the input side of the narrow-band voice channel in the actual
Signal path of the telephone band speech in施例, 82 wideband voice communication path on the input side, 83 the actual narrowband voice communication path on the output side
In the embodiment , a signal path for telephone band voice, and 84 is a broadband voice communication path on the output side . Input audio signals VI1 to V from terminal
In indicates switches SWI131 to SWIn of each channel.
The voice type codes S1 to Sn are input to the determination circuit 5. The decoding circuit 11 includes a wideband speech decoder Da1, a narrowband speech decoder Db1, and a band converter Dd.
The output of the wideband speech decoder Da1 is connected to the wideband speech communication path 82. Also, the output from the narrowband speech decoder Db1 via the band converter Dd1 is
Similarly, it is connected to the broadband voice communication path 82. The output of the narrowband decoder Db1 is connected to the narrowband voice communication path 81.
The wideband voice addition circuit 71 is provided between the wideband voice communication path 82 and the wideband voice communication path 84, and the narrowband voice addition circuit 72 is provided between the narrowband voice communication path 81 and the narrowband voice communication path 83. . The output of the wideband speech addition circuit 71 and the output of the narrowband speech addition circuit 72 are input to the encoding circuit 21, and the output of the encoding circuit 21 is the output side switch SW.
Is input to the O1 41. This output is output switch S
It is selected by WO1 41 and becomes an output signal as VO1.

Similarly, for the input signal VI2, an input side switch SWI2 32 and a decoding circuit 12 are prepared, and the output side also includes an encoding circuit 22 and an output side switch SWO2.
42 are prepared. Hereinafter, an input switch SWIn33 and a decoding circuit 13 are provided for the input audio signal VIn, and an encoding circuit 23 and an output switch S
WOn 43 is prepared. The switch SWI1 31 and the switch SWO1 41 are paired, and either the wide band side or the narrow band side is selected by the output of the selector control unit. Each decoding circuit includes a wideband decoder of Da * (* = 1 to n), a narrowband decoder of Db *, and a band converter by upsampling of Dd *. An encoding circuit paired with this is a wideband encoder of Ea *,
It comprises a narrowband encoder of b * and a band converter Ec * by downsampling.

Next, the operation will be described. In the figure, it is assumed that input audio signals VI1 and VIn are wideband audio signals, and VI2 is a narrowband audio signal. Also, it is assumed that voice addition is performed in accordance with the wider band. Input audio signal VI1
The voice type code is detected by the determination circuit 5
However, as will be described in various examples in each embodiment described later,
The selector control unit 6 selects the A contact of the switch SWI1 31 according to the predetermined selection criterion . Similarly, the output side switch SWO141 to be paired also selects the A side. Accordingly, the input audio signal VI1 is input to the wideband audio addition circuit 71 via the decoder Da1. On the other hand, since the input audio signal VI2 has a narrow band, the selector control unit 6 determines whether the switch SWI2
32 and the B side of the switch SWO242 are selected. In this case, the input audio signal VI2 is input to the wideband audio addition circuit 71 via the decoder Db2 and the band converter Dd2.

Similarly, for each input signal VIn, one of the decoders is selected according to the type of the input voice and input to the wideband voice addition circuit 71. The wideband speech addition circuit 71 adds the signal inputs of the remaining N-1 points excluding the input of each point and returns the result to the coding circuit of the corresponding terminal. This is repeated for each point. The encoding circuit 21 corresponding to the input signal VI1 encodes the output of the wideband speech addition circuit 71 through the wideband encoder Ea1 and outputs it as VO1. Encoding circuit 2 corresponding to input signal VI2
In 2, the output of the wideband speech addition circuit 71 is once down-sampled via the band converter Ec2, encoded by the narrowband encoder Eb2, and output as VO2.
Similarly, the encoding circuit corresponding to each input signal operates the corresponding encoder to obtain the corresponding audio signal VOn. As described above, in this embodiment, the input signal having the wider band is selected and operated, so that only the wideband speech addition circuit is used.

Embodiment 2 FIG. FIG. 2 is a configuration diagram showing another embodiment. In FIG. 2, the decoding circuits 11a to 13a have band converters provided on both the wide band side and the narrow band side, as shown in detail in FIG. Similarly, the encoding circuit 2
1a to 23a, as shown in detail in FIG. 4, have band converters provided on both the wide band side and the narrow band side. Other components are the same as those in FIG. By making each decoding circuit and each encoding circuit have the configuration shown in FIGS. 3 and 4, even if the input signal is a signal of either a wide band or a narrow band,
A configuration in which a wideband or narrowband speech addition circuit can be used freely can be adopted. The operation of the circuit of FIG. 2 is the same as that of FIG. FIG. 3 is a configuration diagram showing details of the decoding circuit. In the figure, Dax111, D
bx112, Dcx113 and Ddx114 functions,
FIG. 5A shows the relationship between the input and output signals. Similarly ~
FIG. 5 (b) shows the relationship between the signals processed by. As described above, according to the decoding circuit of FIG. 3, a wideband linear signal and a narrowband linear signal can be arbitrarily generated for any of the narrowband input signal and the wideband input signal. FIG. 4 is a configuration diagram showing details of the encoding circuit of FIG. In the figure, E
ax11, Ebx212, Ecx213 and Edx21
FIG. 6 shows the function of No. 4 and its input / output signals.
Shows the conversion form of the signal.

Embodiment 3 FIG. Another embodiment will be described. In the configuration shown in FIG. 2, the selector control unit includes a wideband decoder and a wideband encoder for a wideband input signal, and a selector control unit for a narrowband audio input signal. Is an example in which a narrowband decoder and a narrowband encoder are selected, and a band converter is not used in the encoding circuit . At this time, the switch selection state of the selector control unit 6 of FIG. 2 and the paths of FIGS . 3 and 4 through which the audio signals of VIn and VOn pass through the decoding / encoding circuit are shown in FIG .
(A). In this case, since the band converter of the encoding circuit is not used, there is no extra distortion or delay, and a high-quality audio signal can be obtained. However, both the broadband speech addition circuit 71 and the narrowband speech addition circuit 72 are used as the speech addition circuit.

Embodiment 4 FIG. As yet another embodiment, FIG.
In the above configuration, an example will be described in which the output of the selector control unit 6 selects the band having the larger number of input audio signals of the participating conference. In this case, for example, when the number of subscribers of the narrowband audio signal is larger, the voice quality is reduced with respect to the input of the wideband audio signal, but only the narrowband audio addition circuit 72 may be used. Conversely, when there are many wideband audio signals as input audio signals, the selector control unit 6 selects the wideband audio signal side. In this case, although improvement in quality cannot be expected for a narrow-band audio input signal, only the use of the wide-band audio addition circuit 71 is sufficient as an addition circuit. In each case, the use situation of the decoding circuit and the encoding circuit is shown in FIG.
(B).

Embodiment 5 FIG. When the input audio signals are all broadband audio signals or all narrowband audio signals, FIG.
Alternatively, audio processing can be realized by any of the circuits in FIG. In this case, no band converter is used, and only one of the wide-band sound addition circuit 71 and the narrow-band sound addition circuit 72 may be used for the sound addition circuit corresponding to the input / output sound signal. In this case, the switch selection in FIG.
The operation path of the audio signal in FIGS. 3 and 4 is set as shown in FIG.

Embodiment 6 FIG. Further, in the configuration shown in FIG. 2, a method in which the meeting organizer selects as a selection criterion for the output of the selector control unit 6 may be adopted. FIG. 8B shows details of the switch selection and the setting of the operation path of the signal passing through the decoding circuit and the encoding circuit in this case. When the circuit of FIG. 2 is used, in each of the above-described embodiments, the decoding circuit and the encoding circuit need only be the same component for each audio signal, and the effect of sharing parts is great.

Embodiment 7 FIG. FIG. 9 is a block diagram showing an embodiment of the second aspect of the present invention. In the figure, reference numerals 91 and 92 are level adjustment circuits. Other components are the same as those in FIG. Next, the operation will be described. The input audio signals from each terminal have different amplitude levels due to the usage state of the equipment in each terminal, transmission loss, and the like. After these input signals are once linearized by the decoding circuit, the level adjustment circuit 91 for wideband speech and the level adjustment circuit 92 for narrowband speech
Is adjusted to a certain level, and is input to the wideband speech addition circuit 71 or the narrowband speech addition circuit 72, respectively. Subsequent operations are the same as those described with reference to FIG. By doing so, the input audio signals from each terminal are at the same level, and the influence of the fluctuation at each point is suppressed.

Embodiment 8 FIG. FIG. 10 is a block diagram for explaining an embodiment of the third aspect of the present invention. FIG. 10 shows a linear code form of wideband speech as CCIPTREC. G. FIG. Although the circuit configuration is based on the addition method of multipoint communication recommended in H.722 and converted into a linear code for each band in a wide band and a low band and N-1 addition is performed separately, actually, an audio band is used. Since the voice adding circuit and the telephone band voice adding circuit are not used at the same time, the low band audio band voice adding circuit can be shared by the telephone band voice adding circuit 73. Thereby, the device can be simplified and the circuit can be downsized.

[0023]

According to the present invention, there is provided a multipoint voice communication apparatus comprising: a determination circuit for determining a frequency band and a coding rate of a voice signal transmitted from each terminal; a decoder and a band converter for each terminal; Encoder, band converter, and selector control means
And a wideband addition circuit and a narrowband addition circuit.
Even if each terminal has a different frequency band,
Small size of hardware, high efficiency using few adder circuits
There is an effect that a voice communication device can be realized. In addition , there is an effect that high-quality voice communication can be performed as needed, and a highly efficient voice communication device can be constructed using a small number of voice addition circuits. Further, according to the second aspect of the present invention, there is an effect that a level difference caused by the environment of each transmitting end is eliminated and a voice communication device having no level difference can be realized. According to the third aspect of the present invention, since the voice signal adding circuit of the telephone band is shared as the low-frequency adding circuit, the size of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a multipoint voice communication device according to an embodiment of the present invention.

FIG. 2 is another configuration diagram of a multipoint voice communication device according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a decoding circuit of FIG. 2;

FIG. 4 is a configuration diagram of an encoding circuit of FIG. 2;

5 is a diagram illustrating processing and input / output of each element of the decoding circuit in FIG. 3;

FIG. 6 is a diagram illustrating processing and input / output of each element of the encoding circuit of FIG. 4;

FIG. 7 is a diagram illustrating switch settings and signal paths in a third embodiment and a fourth embodiment.

FIG. 8 is a diagram illustrating switch settings and signal paths in the fifth and sixth embodiments.

FIG. 9 is a configuration diagram including a circuit that performs level adjustment between respective points, which is an example of the invention of claim 2;

FIG. 10 is a block diagram showing one embodiment of the third invention.

FIG. 11 is a configuration diagram showing an embodiment of a conventional multipoint voice communication device.

[Explanation of symbols]

 Reference Signs List 5 judgment circuit 6 selector control section 11-13, 11a-13a decoding circuit 21-23, 21a-23a encoding circuit 31-33 voice communication device input stage switch 41-43 voice communication device output stage switch 71 wideband voice addition circuit 72 Narrowband speech addition circuit 111 Broadband speech decoder 112 Narrowband speech decoder 113 Band converter by downsampling 114 Bandconverter by upsampling 211 Wideband speech coder 212 Narrowband speech coder 213 Band converter by downsampling 214 Up Band converter by sampling

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04M 3/56

Claims (5)

(57) [Claims] 1. The frequency of a transmission signal from each of three or more terminals.
Judgment to detect several bands and coding speed as path determination factors
Circuit, a wideband decoder for decoding a transmission signal from the terminal, and a narrowband
Area decoder and the audio signal decoded by each decoder
Band that converts one to the frequency band of the other decoder output
A sound signal that has been decoded and band-converted.
The input-side broadband voice communication path and the input-side narrowband voice communication path.
It has multiple decoding paths to output to the input side voice communication path.
A decoding means provided for each terminal; and a speech signal component from the input-side broadband speech communication path.
For each terminal other than the terminal, add
Wide-band addition circuit that outputs the signal to the output-side broadband communication path
And the voice signal component from the input side narrowband voice communication path
For each terminal other than the terminal, add
Narrow-band addition circuit that outputs to the output side narrow-band communication path as a signal
And a wideband encoder and a narrowband encoder, wherein the output side
Multiple outputs, including broadband and egress narrowband voice
The received signal after addition obtained by selecting from the
An end that has multiple encoding paths for encoding and outputting to the terminal side
Using the encoding means provided for each terminal and the route determination factor of the terminal detected by the determination circuit.
The wideband addition circuit or the narrowband based on a predetermined rule.
Select one or both of the band adders and select
Corresponding to the adder circuit, the decoding means
And the encoding path in the encoding means.
Select each of the plurality of input voice communication paths and the plurality of
Control to control the connection to the output side voice communication path
Means for multipoint voice communication
Place. 2. A decoding system comprising: a plurality of decoding means provided for each terminal;
Level of the audio signal output to the voice communication path on the input side of the
Level adjustment provided for each band to convert to almost the same level
2. The multipoint according to claim 1, further comprising adjusting means.
Inter-voice communication device. 3. The frequency of a transmission signal from each of three or more terminals.
Judgment to detect several bands and coding speed as path determination factors
A circuit, a narrowband decoder for decoding a transmission signal from the terminal,
Decodes the transmission signal from the terminal into multiple frequency bands
And a wideband decoder for converting the sound decoded by each of the decoders.
Multiple input sides corresponding to voice signals for each frequency band
Each terminal has multiple decoding paths to output to the voice communication path
Provided decoding means, and a high frequency band in a plurality of frequency bands from the input side voice communication path.
Add the signal component of the frequency to each terminal other than the relevant terminal
Output side high-frequency voice communication path
High-frequency addition circuit to output to the low-frequency in a plurality of frequency bands from the input voice communication path
Add the signal component of the frequency to each terminal other than the relevant terminal
Output low-frequency voice communication path
And a high-frequency addition circuit obtained from the output-side high-frequency voice communication path.
The low-frequency range obtained from the output and the output of the output-side low-frequency addition circuit.
After encoding the output of the addition circuit for each band, the wide band to be synthesized
Obtained from the encoder and the output low-frequency voice communication path
A narrow-band encoder for encoding the output of the low-frequency addition circuit.
Corresponding to the signal path of each corresponding decoding means.
Select a signal path to obtain encoded output to the terminal, for each terminal
Using the encoding means provided in the terminal and the route determination factor of the terminal detected by the determination circuit.
Based on a predetermined rule, the high-frequency addition circuit or the low-frequency
Select one or both of the adder circuits and
Corresponding to the arithmetic circuit,
Select the decoding path and the encoding path in the encoding means
And the plurality of input voice communication paths and the plurality of
Selector control means for controlling the connection with the output side voice communication path
A multipoint voice communication device comprising: a step; 4. A decoding means based on the output of the narrowband decoder.
High and low frequency bands corresponding to the output of the wideband decoder
Equipped with a wideband band converter that outputs the divided signal
Ete, instead of the narrowband decoder output, variable band to wide-band
The output of the switch is output to the input side voice communication path.
DOO multipoint voice communications apparatus according to claim 3, wherein. 5. The low-frequency addition circuit is a telephone band voice addition circuit.
5. The method according to claim 3, wherein
Or the multipoint voice communication device according to the above.