JP5080860B2 - Audio transmission system - Google Patents

Description

  The present invention relates to an audio transmission system.

  Conventionally, a voice transmission system is provided in which a communication terminal such as a plurality of interphones that transmit and receive audio signals and a control terminal that controls communication between the communication terminals are connected to each other via a signal line. (For example, refer to Patent Document 1).

In this type of voice transmission system, the control terminal sets a certain number of time slots per unit time, and assigns different time slots to each set of call terminals that communicate with each other. The division multiplexing system enables a plurality of sets of call terminals connected to a common signal line to talk independently of each other.
Japanese Patent Laid-Open No. 9-18598

  Conventionally, the number of time slots allocated to a set of call terminals in a single call is constant, so there are many time slots that are not used when the number of call terminals simultaneously calling is small. .

  The present invention has been made in view of the above reasons, and an object thereof is to provide an audio transmission system in which time slots are effectively used.

  According to the first aspect of the present invention, a plurality of voice input terminals each receiving a voice, a plurality of voice output terminals each outputting a voice inputted in each voice input terminal, and a voice input terminal An audio transmission system in which a control terminal that controls communication with an audio output terminal is connected to each other via a signal line, and each audio input terminal analogizes input audio An audio input unit that converts the signal into an output signal, an encoding unit that outputs audio data obtained by encoding the analog signal output from the audio input unit, and an audio data output from the encoding unit A modulation unit that outputs the received audio signal, a control unit that generates a control signal transmitted and received between the control terminal, and a control signal output from the control unit is transmitted to the control terminal via a signal line and modulated. The audio signal output by the And a communication unit that receives the control signal transmitted from the control terminal via the signal line and transmits the signal by time division multiplex transmission via the signal line, and each voice output terminal is connected to the control terminal. A control unit that generates a control signal transmitted and received between the control unit and the control signal output from the control unit to the control terminal unit via the signal line and the control signal and sound transmitted from the control terminal unit via the signal line The communication unit that receives the audio signal transmitted from the input terminal via the signal line, the demodulation unit that outputs the audio data obtained by demodulating the audio signal received by the communication unit, and the demodulation unit output A decoding unit that outputs an analog signal generated by decoding the audio data, and an audio output unit that converts the analog signal output by the decoding unit into audio, and the control terminal is an audio input terminal Vessel The transmission unit periodically sends a synchronization signal, which is a reference of the timing at which the transmission unit transmits the audio signal and the timing at which the audio output terminal receives the audio signal, to the signal line, and each audio input terminal and each audio output terminal A communication unit that transmits and receives control signals via a signal line, and each audio input terminal that transmits audio signals according to the control signal received by the communication unit is synchronized for transmission and reception of audio signals. A predetermined number of time slots set between the signals, and a control unit for controlling the communication unit to notify each voice input terminal unit and each voice output terminal unit of the time slot allocation. At least one of the terminal device and the audio output terminal device is provided with an operation unit that accepts an operation input for requesting start and end of transmission / reception of an audio signal, and the control unit operates the operation unit. A control signal for requesting the start of time slot assignment and a control signal for requesting the end of time slot assignment are generated and output in response to an operation input received by the cropping unit. When the number of voice input terminals to which time slots are to be allocated is smaller than the total number of time slots between synchronization signals, the control unit has one each for at least one voice input terminal. A plurality of time slots are assigned to each synchronization signal.

  According to the present invention, since a plurality of time slots are allocated to one voice input terminal per one synchronization signal, the time slots can be used effectively.

  According to a second aspect of the present invention, in each of the voice input terminals according to the first aspect of the present invention, the encoding unit can generate a plurality of types of voice data having different bit rates, and one synchronization signal The higher the number of time slots used for transmitting audio signals, the higher the bit rate audio data is generated. In each audio output terminal, the decoding unit decodes each of the plurality of types of audio data. This is possible, and is characterized in that decoding is performed assuming that the bit rate of the audio data is higher as the number of time slots to be received per synchronization signal is larger.

  According to the present invention, the time slot can be effectively used for improving the sound quality.

  According to a third aspect of the present invention, in each of the voice input terminals according to the first aspect of the present invention, when the communication units are assigned a plurality of time slots per one synchronization signal, the voice signals having the same contents are transmitted. Then, a continuous transmission operation for transmitting the number of times of the assigned time slot is performed, and in each audio output terminal, each of the decoding units receives a series of audio signals transmitted by the continuous transmission operation by the communication unit. One voice data is decoded from the series of voice signals.

  According to the present invention, the time slot can be effectively used for improving the accuracy of receiving audio data.

  According to a fourth aspect of the present invention, in each of the voice input terminals according to the first aspect of the present invention, the communication unit performs a continuous transmission operation of transmitting a voice signal having the same content a plurality of times in response to an instruction from the control terminal. The encoding unit can generate a plurality of types of audio data having different bit rates in accordance with instructions from the control terminal. In each audio output terminal, the decoding unit Each of the plurality of types of audio data can be decoded in response to an instruction from a device, and when a series of audio signals transmitted by the continuous transmission operation is received by the communication unit, one sequence from the series of audio signals Each voice signal includes an error detection code for detecting a transmission error, and each control unit of each voice output terminal uses the error detection code to detect a transmission error. detection In addition, the rate of occurrence of transmission errors during reception of voice signals is measured and notified to the control terminal by a control signal, and the control unit of the control terminal allocates a plurality of time slots per one synchronization signal. When the rate of occurrence of transmission errors is notified from the audio output terminal that is transmitting the audio signal from the audio input terminal to be notified, when the notified rate of occurrence of transmission errors is equal to or higher than a predetermined transmission failure threshold, The number of times that the audio signal having the same content is transmitted so that the bit rate of the audio data is lowered and the number of times that the audio signal having the same content is transmitted is increased as compared with the case where the transmission error occurrence rate is less than the transmission failure threshold. The bit rate of the voice data is instructed to the voice input terminal, respectively.

  According to the present invention, the time slot can be effectively used for improving the sound quality and the accuracy of receiving voice data in accordance with the transmission error occurrence rate.

  According to a fifth aspect of the present invention, in each of the voice input terminals according to the first aspect of the present invention, the communication unit performs a continuous transmission operation of transmitting a voice signal having the same content a plurality of times in response to an instruction from the control terminal. The encoding unit can generate a plurality of types of audio data having different bit rates in accordance with instructions from the control terminal. In each audio output terminal, the decoding unit Each of the plurality of types of audio data can be decoded in response to an instruction from a device, and when a series of audio signals transmitted by the continuous transmission operation is received by the communication unit, one sequence from the series of audio signals Audio data is decoded, and each audio input terminal and each audio output terminal has an operation unit. In each operation unit, an operation input for instructing start of transmission / reception of an audio signal; and In addition, an operation input indicating that accuracy is required for the audio data in the audio signal is also accepted, and the control unit requires that the audio data be accurate in the control signal for requesting the start of time slot assignment. The control terminal of the control terminal is a voice input terminal in which a plurality of time slots are assigned to one synchronization signal. When instructing the number of times the audio signal having the same content is transmitted and the bit rate of the audio data, the audio data is accurate at the start of time slot assignment to the audio input terminal. When the above operation input indicating that it is required is accepted, accuracy is required for the voice data at the start of time slot assignment to the voice input terminal. Than when the operation input is not accepted that is meant to be, characterized in that to increase the number of transmitting voice signals of the same content together to reduce the bit rate of the audio data.

  According to the present invention, the time slot can be effectively used for improving the sound quality and the accuracy of receiving the voice data depending on whether or not the voice data requires accuracy.

  According to a sixth aspect of the present invention, in any of the third to fifth aspects of the present invention, each audio signal includes an error detection code for detecting a transmission error, and each audio output terminal includes a decoding unit, When the voice signal transmitted by the continuous transmission operation is received by the communication unit, the first voice signal in which no transmission error is detected based on the error detection code among the series of voice signals transmitted by the continuous transmission operation Only the voice data is decoded.

  According to the present invention, the load on the audio output terminal is reduced as compared with the case where all the audio signals transmitted by the continuous transmission operation are used.

  The invention of claim 7 is the invention of any one of claims 3 to 5, wherein each audio signal includes an error detection code for detecting a transmission error, and each audio output terminal includes a decoding unit, , When the voice signal transmitted by the continuous transmission operation is received by the communication unit, all the audio signals in which no transmission error is detected based on the error detection code among the series of audio signals transmitted by the continuous transmission operation One voice data obtained from the voice data by the majority logic for each bit is decoded.

  According to the present invention, there is a possibility that a transmission error that has not been detected may be eliminated, so that the decoding unit of the audio output terminal can obtain more accurate audio data as compared with the invention of claim 6.

  According to an eighth aspect of the present invention, in each of the voice output terminals according to the sixth or seventh aspect of the present invention, the decoding unit is configured based on the error detection code in all of the voice signals transmitted by the continuous transmission operation. When a transmission error is detected, one voice data obtained by the majority logic for each bit from all the voice signals is decoded.

  According to the present invention, even when a transmission error is detected in all audio signals, the composite unit of the audio output terminal can obtain relatively accurate audio data.

  The invention of claim 9 is the decoding unit according to any one of claims 3 to 5, wherein each voice output terminal receives a voice signal transmitted by a continuous transmission operation by the communication unit. The audio data to be decoded is one audio data obtained by the majority logic for each bit from the audio data of all audio signals transmitted by the continuous transmission operation.

  According to the present invention, the more frequently the audio signal having the same content is transmitted by the continuous transmission operation, the more accurate the audio data can be obtained by the decoding unit of the audio output terminal.

  According to the first aspect of the present invention, when the control unit of the control terminal has a small number of voice input terminals that transmit voice signals with respect to the total number of time slots between the synchronization signals, at least one Since a plurality of time slots are allocated per one synchronization signal to the voice input terminal for transmission of voice signals, the time slots can be used effectively.

  According to the invention of claim 2, since the encoding unit of each voice input terminal increases the bit rate of voice data as the number of assigned time slots increases, the time slot can be effectively used to improve sound quality. Can do.

  According to the third aspect of the present invention, the communication unit of each voice input terminal performs a continuous transmission operation of transmitting a voice signal having the same content as many times as the assigned time slot. Can be effectively used to improve the accuracy of

  According to the invention of claim 4, the control unit of the control terminal receives a transmission error from a voice output terminal that receives a voice signal from a voice input terminal to which a plurality of time slots are assigned per synchronization signal. When the occurrence rate is notified, the bit rate of the audio data is higher when the notified transmission error occurrence rate is equal to or higher than a predetermined transmission failure threshold than when the transmission error occurrence rate is less than the transmission failure threshold. The number of times that the audio signal with the same content is transmitted and the bit rate of the audio data are respectively instructed to the audio input terminal so that the number of times that the audio signal with the same content is transmitted is increased. The time slot can be effectively used for improving the sound quality and the accuracy of receiving the voice data according to the transmission error occurrence rate.

  According to the fifth aspect of the present invention, the number of times that the control unit of the control terminal transmits an audio signal having the same content to the audio input terminal to which a plurality of time slots are assigned per synchronization signal. And when the operation input indicating that accuracy is required for the voice data is accepted at the start of the time slot assignment to the voice input terminal in order to instruct the bit rate of the voice data. Lowers the bit rate of the voice data than when the operation input indicating that the voice data is required to be accurate at the start of time slot assignment to the voice input terminal is not accepted. Since the number of times the same audio signal is transmitted is increased, the time slot can be improved according to whether or not the audio data is required to be accurate. It can be effectively utilized to improve the signal accuracy.

  According to the invention of claim 6, the decoding unit of the audio output terminal is the first audio signal in which no transmission error is detected based on the error detection code among the series of audio signals transmitted by the continuous transmission operation. Therefore, the load on the voice output terminal can be reduced as compared with the case where all the voice signals transmitted by the continuous transmission operation are used.

  According to the seventh aspect of the present invention, the decoding unit of the audio output terminal receives all the audio signals in which no transmission error is detected based on the error detection code among the series of audio signals transmitted by the continuous transmission operation. Since one voice data obtained by the majority logic for each bit from the voice data is decoded, there is a possibility that undetected transmission errors may be eliminated. The decoding unit of the terminal can obtain more accurate voice data.

  According to the invention of claim 8, when the decoding unit of the audio output terminal detects a transmission error based on the error detection code in all of the audio signals transmitted by the continuous transmission operation, all the above Since one voice data obtained from the voice signal by the majority logic for each bit is decoded, even if a transmission error is detected in all the voice signals, the complex part of the voice output terminal is relatively Accurate voice data can be obtained.

  According to the ninth aspect of the present invention, the audio data decoded by the decoding unit of the audio output terminal is one piece obtained by the majority logic for each bit from the audio data of all the audio signals transmitted by the continuous transmission operation. Since it is audio data, the more frequently the audio signal having the same content is transmitted by the continuous transmission operation, the more accurate the audio data can be obtained by the decoding unit of the audio output terminal.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the voice transmission system according to the present embodiment includes a plurality of call terminals 2 that transmit and receive voice signals via a signal line Ls, and communication between the call terminals 2 connected to the signal line Ls. And a control terminal 1 for controlling. As the signal line Ls, a balanced line such as a twisted pair line may be used, or an unbalanced line such as a coaxial cable may be used. Each telephone terminal 2 also serves as a voice input terminal and a voice output terminal in the claims.

  The call terminal 2 includes a microphone 20a as a voice input unit that converts voice into an electrical signal, a microphone amplifier 20b that amplifies the output of the microphone 20a, and an output of the microphone 20a that is amplified by the microphone amplifier 20b at a predetermined sampling frequency. And a transmission AD conversion unit 20c that performs A / D conversion by the PCM (Pulse Code Modulation) method with the number of quantization bits, and a codec that generates audio data by encoding (compressing) the output of the transmission AD conversion unit 20c Unit 21a, modulation / demodulation unit 21b that modulates the output of codec decoding unit 21a, transmission DA conversion unit 22a that generates audio signals by D / A conversion of the audio data modulated by modulation / demodulation unit 21b, and transmission DA conversion A transmission amplifier 22b that amplifies the audio signal output from the unit 22a and outputs the amplified audio signal to the signal line Ls. That is, the encoding / decoding unit 21a and the transmission AD conversion unit 20c constitute an encoding unit in the claims. Here, for example, BPSK (Binary Phase Shift Keying) can be used as a modulation method in the modem unit 21b.

  Further, the call terminal 2 includes a reception amplifier 23b that amplifies the voice signal received from the signal line Ls, and a reception AD conversion unit 23a that performs A / D conversion on the voice signal amplified by the reception amplifier 23b. Further, the modulation / demodulation unit 21b generates audio data by demodulating the audio signal AD-converted by the reception AD conversion unit 23a, and the codec decoding unit 21a decodes the audio data generated by the modulation / demodulation unit 21b. Further, the call terminal 2 includes a reception DA conversion unit 24c that generates an analog signal by D / A converting the voice data decoded by the codec decoding unit 21a, and an analog signal output by the reception DA conversion unit 24c. And a speaker 24a as an audio output unit for converting the analog signal amplified by the speaker amplifier 24b into audio. That is, the codec decoding unit 21a and the reception DA conversion unit 24c constitute a decoding unit in the claims. Further, the transmission AD conversion unit 20c and the reception DA conversion unit 24c are connected to the codec decoding unit 21a via the voice switch VS. The voice switch VS compares the volume of the audio data output from the transmission AD conversion unit 20c with the volume of the audio data input to the reception DA conversion unit 24c, and transmits from the transmission AD conversion unit 20c to the codec decoding unit 21a. And one of the paths from the codec decoding unit 21a to the reception DA converter 24c is turned on and the other is turned off. As a result, the incoming call and the outgoing call are automatically switched, so a hands-free call is possible.

  Also, the operation unit 25 that receives an operation input, the control signal transmission / reception unit 26 that transmits / receives a control signal to / from the control terminal 1, and the operation input received by the operation unit 25 or the control signal transmission / reception unit 26 And a control unit 27 that controls each unit in accordance with the control signal. That is, the control signal transmitting / receiving unit 26 and the control unit 27 constitute a control unit in the claims. The control signal is transmitted after being multiplexed with the audio signal by frequency division. The call terminal 2 is connected to the signal line Ls, and the control signal output from the control signal transmitting / receiving unit 26 is transmitted from the transmission amplifier 22b. The audio signal is multiplexed and transmitted, and the audio signal and the control signal are separated from the electric signal received from the signal line Ls, and the audio signal is input to the reception amplifier 23b, and the control signal is transmitted to the control signal transmission / reception unit 26. The demultiplexing / multiplexing unit 28 is provided. That is, the transmission D / A conversion unit 22a, the transmission amplifier 22b, the reception amplifier 23b, the reception A / D conversion unit 23a, and the demultiplexing unit 28 constitute a communication unit in the claims.

  Here, as shown in FIG. 2, the codec / decoder 21a attaches a header to the front of the audio data to be output to the modem 21b, generates an error detection code from the audio data, and adds it to the audio data. That is, each audio signal is obtained by modulating data composed of a header, audio data, and an error detection code. The header includes information such as an identification code (ID) indicating a transmission source, an encoding method of audio data, and a sequence number that is a serial number assigned to each audio signal. As the error detection code, for example, a CRC (Cyclic Redundancy Check) code can be used.

  The control terminal 1 includes a control unit 10, a control signal transmission / reception unit 11 that is controlled by the control unit 10 and transmits / receives a control signal to / from the call terminal 2, and a start / start of a time slot in which an audio signal is to be transmitted / received. The modulation unit 12 that modulates the synchronization signal SY output from the control unit 10 as a reference for the end timing, and the control signal and the synchronization signal SY that are connected to the signal line Ls are multiplexed and transmitted to the signal line Ls and the signal line Ls. And a demultiplexing unit 13 that separates the control signal from the electrical signal received from the signal and inputs the control signal to the control signal transmitting / receiving unit 11. That is, the control unit 10 and the control signal transmission / reception unit 11 constitute a control unit in the claims, and the modulation unit 12 and the demultiplexing unit 13 constitute a communication unit in the claims. The synchronization signal SY indicates a time slot to be used for transmitting a voice signal for each of the call terminals 2 that make a call.

  As shown in FIG. 3, one audio signal is transmitted within one of the time slots TS1 to TSn set between the synchronization signals SY. The length of time (hereinafter referred to as “frame”) from the start of one synchronization signal SY to the start of the next synchronization signal is, for example, 8 msec, and the number of time slots in one frame is all For example, there are 15 frames in common.

  Next, transmission / reception of audio signals in the present embodiment will be described. In the following, there are two units of a call terminal 2 (hereinafter referred to as “call terminal A”) and a call terminal 2 (hereinafter referred to as “call terminal B”) as a call destination. An operation when a call is performed between the call terminals 2 will be described.

  First, when an operation input instructing the start of a call with the call terminal B is received at the operation unit 25 of the call terminal A, the control unit 27 of the call terminal A controls the control signal transmitting / receiving unit 26 to A call request, which is a control signal for requesting establishment of a call with the terminal B, is generated and transmitted to the control terminal 1 via the demultiplexing unit 28 and the signal line Ls as shown in FIG. This call request includes the identification code of the calling terminal A and the identification code of the calling terminal B.

  In the control terminal 1, when a call request is received by the control signal transmission / reception unit 11 via the demultiplexing / multiplexing unit 13, the control unit 10 controls the control signal transmission / reception unit 11 to indicate that there has been a call request. A call notification as a signal is transmitted to the call terminal B as a call destination via the demultiplexing unit 13 and the signal line Ls.

  In the call terminal B, when the call notification is received by the control signal transmitting / receiving unit 26 via the demultiplexing / multiplexing unit 28, the control unit 27 of the call terminal B drives the speaker 24a via the codec decoding unit 21a. Then, a ringing sound is generated, and the operation unit 25 shifts to a calling state in which an operation input instructing the start of a call is received. Then, when the operation input for instructing the start of the call is received by the operation unit 25 in the calling state, the control unit 27 of the call terminal B ends the calling state and controls the control signal transmission / reception unit 26 to control the call. An acknowledgment notice, which is a control signal indicating that the start has been acknowledged, is transmitted to the control terminal 1 via the demultiplexer 13 and the signal line Ls.

  In the control terminal 1, when the acknowledgment notification is received by the control signal transmission / reception unit 11 via the demultiplexing / multiplexing unit 13, the control unit 10 controls the control signal transmission / reception unit 11, and the call source included in the call request The call terminal A is caused to transmit a notification of establishment, which is a control signal indicating the establishment of a call, via the demultiplexing unit 13 and the signal line Ls. At this time, if no call terminal 2 is making a call, transmission of the synchronization signal SY is started. Calling terminal A receives a notification of establishment, and calling terminal B transmits a notification of approval, and also monitors the synchronization signal SY and uses the time slot notified in the synchronization signal SY to transmit a voice signal. The call operation to send / receive is started.

  When an operation input for instructing the end of the call is given to the operation unit 25 in any of the call terminals A and B during the call operation, the control unit 27 of the call terminal 2 controls the control signal generation unit 26. An end request which is a control signal for notifying the end of the call is generated and transmitted to the control terminal 1 via the demultiplexing unit 28 and the signal line Ls. In the control terminal 1, when the end request is received by the control signal transmission / reception unit 11 via the signal line Ls and the demultiplexing / multiplexing unit 13, the control unit 10 transmits the termination terminals A and B that transmitted the end request and Termination notification which is a control signal for ending assignment of time slots to the call terminals A and B that have been in communication with the call terminals A and B and controlling the control signal transmitting / receiving unit 11 to notify the end of the call Are transmitted to the call terminals A and B via the demultiplexing unit 13 and the signal line Ls, respectively. In the call terminals A and B in which the end notification is received by the control signal transmission / reception unit 26 via the signal line Ls and the demultiplexing / multiplexing unit 28, the operations of the codec decoding unit 21a and the modem unit 21b are stopped respectively. Exit.

  Here, the control unit 10 of the control terminal device 1 is a call terminal device that is continuing a call with twice the number of acknowledgment notifications received within a predetermined period (for example, the period of the immediately preceding frame) for each frame. And the total number of call terminals 2 that transmit voice signals, the number of timeslots in one frame divided by the total number of two, and less than or equal to the obtained number of one, two, and four The most number of time slots are assigned to each call terminal 2 that transmits a voice signal, and this is notified to each call terminal 2 by a synchronization signal SY. In addition, when a time slot is allocated by the above method and an unused time slot is generated, a larger number of call terminals 2 than the other call terminals 2 are selected with respect to some call terminals 2 selected by an appropriate method. You may make it allocate a time slot.

  For each frame, the control unit 27 of each call terminal 2 uses the bit rate of the audio data as the bit rate corresponding to the number of time slots assigned to the audio signal transmission source, The codec 21a is controlled so that the analog signal is generated. Specifically, for example, if the number of time slots is four, the bit rate of audio data is set to 128 kbps (that is, the bit rate at which the size of audio data is 128 kb per second of audio), and the number of time slots is two. If so, the bit rate of the audio data is set to 64 kbps by compression according to μ-law, and if the number of time slots is 1, the bit rate of the audio data is compressed by ADPCM (Adaptive Differential Pulse Code Modulation) method Is the least 32 kbps. The bit rate may be determined by each call terminal 2 or may be determined by the control terminal 1 and each call terminal 2 that starts a call or each time slot number is changed. It is good also as a structure instruct | indicated with respect to the telephone terminal 2 by a control signal, respectively.

  According to the above configuration, when the number of call terminals 2 that make a call is smaller than the total number of time slots in one frame, each call terminal 2 is assigned a plurality of time slots, and Since the call terminal 2 to which a plurality of time slots are assigned has a low compression rate (high bit rate) of audio data, the sound quality during a call can be improved. That is, the time slot can be effectively used for improving the sound quality.

(Embodiment 2)
Since the basic configuration of the present embodiment is the same as that of the first embodiment, description and illustration of common portions are omitted.

  In the present embodiment, instead of changing the bit rate (compression rate) of the voice data, each call terminal 2 repeatedly transmits the same voice signal as many times as the number of assigned time slots (continuous transmission). Send) is different. Unlike the first embodiment in which the number of time slots assigned to the call terminal 2 is any one of 1, 2, and 4, in this embodiment, the number of time slots assigned to the call terminal 2 has various integer values. It can take.

  Then, in the call terminal 2 that has received the continuously sent voice signal, one piece of voice data is obtained from the continuously sent voice signal.

  As a specific method for obtaining one piece of voice data from the voice signal transmitted continuously by the call terminal 2, for example, the control unit 27 receives the voice signal (the voice signal from the call terminal 2 of the call partner). When there are a plurality of time slots assigned to (transmission), that is, when audio signals are continuously transmitted, each time an audio signal is received, an error detection code in the received audio signal and the audio signal It compares with the error detection code generated from the voice data in it, and when it does not match (that is, when a transmission error is detected), it discards the voice signal and transmits it among the continuously sent voice signals Only audio signals for which no error has been detected are decoded. In this case, if no transmission error is detected in one audio signal, all subsequent audio signals having the same contents are discarded, compared with the case where all the continuously transmitted audio signals are stored. The burden can be reduced.

  Alternatively, the audio data is stored for all the audio signals for which no transmission error is detected, and after the reception of the continuous audio signal is completed, the audio data of all the audio signals for which no transmission error is detected is stored. One voice data may be obtained by a majority logic for each bit. For example, if the first 5 bits of the audio data stored for 3 times are 11100, 11010, 11001, the 1st and 2nd bits each match with 1 in each case, and the 3rd to 5th bits each have 0 as 1 As a result of adopting 0 because of the larger number, the first 5 bits of the obtained audio data are 11000. For example, all the bits having the same number of 1 and 0 are set to 0, for example. If the majority logic for each bit is used as described above, there is a possibility that a transmission error that has not been detected by the error detection code may be corrected compared to the case where only one voice signal in which no transmission error has been detected is used. Thus, more accurate audio data can be obtained.

  Further, the control unit 27 stores all the audio data of the continuously transmitted audio signal, and when a transmission error is detected in all of the continuously transmitted audio signals, the majority logic for each bit is stored for all the stored audio data. Thus, one piece of audio data may be obtained.

  Alternatively, the control unit 27 stores the demodulated data for all of the continuously transmitted audio signals, and for all bits of the demodulated data, the header, the audio data, and the error detection code, by the majority logic for each bit, One piece of data may be obtained.

  According to the above configuration, the time slot can be effectively used for accurate audio data reception.

(Embodiment 3)
Since the basic configuration of the present embodiment is the same as that of the first embodiment, description and illustration of common portions are omitted.

  In the present embodiment, the change in the bit rate of the audio data as in the first embodiment and the change in the number of continuous transmissions as in the second embodiment are combined according to the state of transmission / reception of the audio signal.

  More specifically, the control unit 27 of each call terminal 2 to which a plurality of time slots are assigned, for each received voice signal, an error detection code in the received voice signal, and in the voice signal Are compared with error detection codes generated from the audio data, and the control signal transmitting / receiving unit 26 is controlled when reception of all the audio signals for each frame is completed. Of these, the error notification, which is a control signal for notifying the number of voice signals in which the two error detection codes are different from each other (that is, a transmission error is detected), is transmitted to the control terminal 1.

  When the error notification is received by the control signal transmission / reception unit 11 via the signal line Ls and the demultiplexing / multiplexing unit 13, the control terminal 1 transmits / receives an audio signal to / from the call terminal 2 that has transmitted the error notification. An operation instruction, which is a control signal for instructing a combination of the number of times of continuous transmission according to the error notification and the bit rate of the voice data, is transmitted to the calling terminal 2 that is performing the operation.

  In each call terminal 2 that has received the operation instruction, the control unit 27 controls the codec decoding unit 21a so that the bit rate and the number of continuous transmissions of the voice data are values according to the operation instruction.

  Specifically, for example, when the number of time slots allocated to the target call terminal 2 is 2, in the operation instruction, the number of transmission errors detected in the error notification may be 0. For example, if the bit rate of the audio data is set to 64 kbps and an operation mode in which the continuous transmission operation is not performed is instructed, and the number of transmission error detections indicated in the error notification is one or more, the bit rate of the audio data is reduced to 32 kbps. As a result, an operation mode for performing a continuous transmission operation with the continuous transmission count set to 2 is instructed.

  Further, when the number of time slots allocated to the target call terminal 2 is four, if the number of transmission errors detected in the error notification is one or less in the operation instruction, the voice If an operation mode in which a continuous transmission operation is not performed with the data bit rate set to 128 kbps is instructed and the number of transmission error detections indicated in the error notification is 2, the audio data bit rate is set to 64 kbps and the number of continuous transmissions is 2 If the operation mode in which the continuous transmission operation is performed is instructed and the number of transmission error detections indicated in the error notification is 3 times or more, the bit rate of the voice data is set to the minimum 32 kbps and the number of continuous transmissions is 4 times. An operation mode for performing the continuous transmission operation is instructed. In the above example, the transmission failure thresholds in the claims are 0.5 and 0.75.

  According to the above configuration, the time slot can be effectively used for improving the sound quality when the noise is low, and the time slot can be effectively used for accurate audio data reception when the noise is high.

(Embodiment 4)
Since the basic configuration of the present embodiment is the same as that of the third embodiment, description and illustration of common portions are omitted.

  In this embodiment, when the number of assigned time slots is 2 or more, which operation mode is selected is input to the operation unit 25 of the call terminal A on the call side at the start of the call. The point determined accordingly is different from the third embodiment.

  Specifically, in each call terminal 2, an operation input indicating that the call is an important call requiring accuracy of voice data can be performed on the operation unit 25. Then, at the start of the call, whether or not the operation input has been made is indicated in the call request. When a plurality of time slots are allocated, the control terminal device 1 is as low as possible (that is, has a high compression ratio) and continues as much as possible when the operation input is made at the start of a call. While an operation mode with a large number of transmissions is instructed, an operation mode with a bit rate as high as possible (that is, with a low compression rate) is instructed when the operation input is not made at the start of a call.

  According to the above configuration, the time slot can be used effectively for improving sound quality when accuracy is not required for audio data, and the time slot is effective for receiving accurate audio data when accuracy is required for audio data. Can be used.

  In each of the first to fourth embodiments, a time slot dedicated to communication between the control terminal device 1 and the communication terminal device 2 is provided instead of a configuration in which the control signal is transmitted and received at a frequency different from that of the voice signal. For example, control signals may be transmitted and received between the control terminal 1 and the call terminal 2 by a known technique such as polling using a slot. If this configuration is adopted, the demultiplexing units 13 and 28 are not required in the control terminal 1 and the call terminal 2 respectively.

  In each of the first to fourth embodiments, one call terminal 2 may be integrated with the control terminal 1 so that the control terminal 1 can be used as a call terminal. In this case, the configuration and operation of the control terminal 1 to operate as a call terminal are the same as those of the other call terminals 2 except that transmission / reception of control signals to / from the control terminal 1 is not necessary. Since it is the same, detailed description is abbreviate | omitted.

  Furthermore, in each of the first to fourth embodiments, a voice input terminal dedicated for transmission that does not have a configuration for voice output, such as the speaker 24a, or a voice reception that does not have a configuration for voice input, such as the microphone 20a. A dedicated audio output terminal may be provided.

It is a block diagram which shows schematic structure common to each embodiment of this invention. It is explanatory drawing which shows the structure of the audio | voice signal in the same as the above. It is explanatory drawing which shows the relationship between the synchronizing signal and time slot same as the above. It is explanatory drawing which shows an example of an operation | movement same as the above.

Explanation of symbols

1 Control terminal 2 Call terminal (voice input terminal and voice output terminal in claims)
DESCRIPTION OF SYMBOLS 10 Control part 11 Control signal transmission / reception part 12 Modulation part 13 Demultiplexing part 20a Microphone (voice input part in a claim)
21a Coder / Decoder 21b Modulator / Demodulator 22a Transmit D / A Converter 22b Transmit Amplifier 23a Receive A / D Converter 23b Receive Amplifier 24a Speaker (Audio Output Unit in Claims)
26 control signal transmission / reception unit 27 control unit 28 demultiplexing unit Ls signal line SY synchronization signal TS1 to TSn time slot

Claims (9)

A plurality of voice input terminals each receiving voice input, a plurality of voice output terminals each outputting voice input in the voice input terminal, and between the voice input terminal and the voice output terminal And a control terminal that controls communication in a voice transmission system connected to each other via a signal line,
Each voice input terminal includes a voice input unit that converts the input voice into an analog signal and outputs it, and a coding unit that outputs voice data obtained by encoding the analog signal output from the voice input unit And a modulation unit that outputs a voice signal obtained by modulating the voice data output from the encoding unit, a control unit that generates a control signal transmitted and received between the control terminals, and a control unit that outputs The control signal is transmitted to the control terminal via the signal line, and the audio signal output from the modulation unit is transmitted by time division multiplex transmission via the signal line, and the control signal transmitted from the control terminal via the signal line is transmitted. A communication unit for receiving,
Each audio output terminal includes a control unit that generates a control signal transmitted to and received from the control terminal, and transmits the control signal output from the control unit to the control terminal via a signal line. A communication unit that receives the control signal transmitted from the transmitter via the signal line and the voice signal transmitted from the voice input terminal via the signal line, and the demodulated voice signal received by the communication unit. A demodulator for outputting the audio data, a decoder for outputting an analog signal generated by decoding the audio data output by the demodulator, and an audio output for converting the analog signal output by the decoder to audio And
The control terminal periodically sends a synchronization signal to the signal line as a reference for the timing at which the communication unit of the voice input terminal transmits the voice signal and the timing at which the voice output terminal receives the voice signal. A communication unit that transmits and receives a control signal between the input terminal and each voice output terminal via a signal line, and each voice input terminal that transmits a voice signal according to the control signal received by the communication unit On the other hand, a predetermined number of time slots are set between the synchronization signals for transmission and reception of audio signals, and the communication unit is controlled to notify each audio input terminal and each audio output terminal of the time slot allocation. And a control unit
At least one of the voice input terminal and the voice output terminal is provided with an operation unit for accepting an operation input for requesting start and end of transmission / reception of an audio signal, and an operation accepted by the control unit by the operation unit A control signal for requesting the start of time slot assignment and a control signal for requesting the end of time slot assignment according to input are generated and output, respectively.
When the number of voice input terminals to which time slots are to be allocated is smaller than the total number of time slots between synchronization signals, the control unit of the control terminal is provided for at least one voice input terminal. A voice transmission system, wherein a plurality of time slots are assigned to each synchronization signal. In each voice input terminal,
The encoding unit can generate a plurality of types of audio data having different bit rates, and the higher the number of time slots used for transmitting audio signals per synchronization signal, the higher the bit rate audio data. Generate
In each audio output terminal,
The decoding unit can decode each of the plurality of types of audio data, and decodes the higher the bit rate of the audio data as the number of time slots to be received per one synchronization signal increases. The voice transmission system according to claim 1. In each voice input terminal,
When the communication unit is assigned a plurality of time slots per one synchronization signal, the communication unit performs a continuous transmission operation of transmitting the audio signal having the same content as many times as the assigned time slot,
In each audio output terminal,
2. The decoding unit according to claim 1, wherein when the series of audio signals transmitted by the continuous transmission operation is received by the communication unit, the decoding unit decodes one piece of audio data from the series of audio signals. Audio transmission system. In each voice input terminal,
The communication unit is capable of continuous transmission operation that transmits the same content audio signal multiple times in response to an instruction from the control terminal.
The encoding unit can generate a plurality of types of audio data having different bit rates in response to an instruction from the control terminal,
In each audio output terminal,
The decoding unit can decode each of the plurality of types of audio data according to an instruction from the control terminal, and when the series of audio signals transmitted by the continuous transmission operation is received by the communication unit, the series One voice data is decoded from the voice signal of
Each voice signal includes an error detection code for detecting transmission errors,
The control unit of each voice output terminal respectively detects a transmission error using an error detection code, measures the occurrence rate of a transmission error when receiving a voice signal, and notifies the control terminal by a control signal,
When the control unit of the control terminal is notified of the rate of occurrence of transmission errors from a voice output terminal that is transmitting a voice signal from a voice input terminal that is assigned a plurality of time slots per synchronization signal. When the reported transmission error occurrence rate is equal to or higher than the predetermined transmission failure threshold, the bit rate of the audio data is made lower and the same content than the case where the transmission error occurrence rate is less than the transmission failure threshold. The number of times of transmitting an audio signal having the same content and the bit rate of audio data are respectively instructed to the audio input terminal so as to increase the number of times of transmitting the audio signal. The voice transmission system described. In each voice input terminal,
The communication unit is capable of continuous transmission operation that transmits the same content audio signal multiple times in response to an instruction from the control terminal.
The encoding unit can generate a plurality of types of audio data having different bit rates in response to an instruction from the control terminal,
In each audio output terminal,
The decoding unit can decode each of the plurality of types of audio data according to an instruction from the control terminal, and when the series of audio signals transmitted by the continuous transmission operation is received by the communication unit, the series 1 audio data is decoded from the audio signal of
In each voice input terminal and each voice output terminal having an operation unit,
The operation unit also accepts an operation input indicating that accuracy of audio data is required in the audio signal as well as an operation input instructing start of transmission / reception of the audio signal,
The control unit notifies the control terminal whether or not the operation input indicating that accuracy is required for the audio data is received in the control signal for requesting the start of time slot allocation,
The control unit of the control terminal determines the number of times that the audio signal having the same content is transmitted to the audio input terminal to which a plurality of time slots are assigned per synchronization signal and the bit rate of the audio data. When instructing, when the operation input indicating that accuracy is required for voice data is accepted at the start of assignment of a time slot to the voice input terminal, the voice input terminal The audio data bit rate is lowered and the audio signal with the same content is transmitted compared to the case where the above operation input indicating that the audio data is required to be accurate at the start of time slot assignment to 2. The voice transmission system according to claim 1, wherein the number of times of transmission is increased.   Each audio signal includes an error detection code for detecting a transmission error. In each audio output terminal, each decoding unit receives the audio signal transmitted by the continuous transmission operation when the communication unit receives the signal. 6. Only the voice data of the first voice signal in which no transmission error is detected based on the error detection code among a series of voice signals transmitted by the continuous transmission operation is decoded. The voice transmission system according to any one of the above.   Each audio signal includes an error detection code for detecting a transmission error. In each audio output terminal, each decoding unit receives the audio signal transmitted by the continuous transmission operation when the communication unit receives the signal. One voice data obtained by the majority logic for each bit from the voice data of all voice signals in which no transmission error is detected based on the error detection code among a series of voice signals transmitted by the continuous transmission operation The audio transmission system according to any one of claims 3 to 5, wherein decoding is performed.   In each audio output terminal, the decoding unit, when a transmission error is detected based on the error detection code in all the audio signals transmitted by the continuous transmission operation, bit by bit from all the audio signals. 8. The voice transmission system according to claim 6, wherein one voice data obtained by the majority logic is decoded.   In each audio output terminal, when the audio signal transmitted by the continuous transmission operation is received by the communication unit, the audio data decoded by the decoding unit is all the audio signals transmitted by the continuous operation. 6. The voice transmission system according to claim 3, wherein the voice transmission system is one voice data obtained from the voice data by a majority logic for each bit.

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