JP4798065B2 - Audio transmission system - Google Patents

Description

  The present invention relates to an audio transmission system that transmits an audio signal via a signal line.

  2. Description of the Related Art Conventionally, an audio transmission system including an audio transmission terminal device that transmits an audio signal by a packet and an audio reception terminal device that outputs audio based on the received audio signal is provided, for example, installed at the entrance of a dwelling unit. It is used in door phone systems that transmit and receive audio signals via signal lines between a door phone slave unit and a base unit installed in a dwelling unit, voice call systems that use cellular phones, PHS, and the like.

  In such an audio transmission system, a transmission error may occur due to transmission loss of a transmission line (for example, a signal line) or external noise. When a transmission error occurs, the audio signal transmitted by the audio transmission terminal device is different from the audio signal received by the audio reception terminal device, which causes abnormal sound in the audio output by the audio reception terminal device. There was a problem of mixing.

Therefore, when transmitting an audio signal from the audio transmitting terminal device to the audio receiving terminal device, for example, when transmitting the audio data obtained by encoding the audio signal by information source into a plurality of packets, Is provided with an error detection code such as cyclic redundancy check (CRC), and the voice reception terminal device performs error detection on the voice data of the packet. It has been proposed to perform a muting process that discards the audio data or replaces the audio data with data of a predetermined pattern that reduces the volume (for example, see Patent Document 1).
Japanese Patent No. 2627579

  In patent document 1, it can reduce that an abnormal sound mixes with the audio | voice which an audio | voice receiving terminal device outputs. However, since the voice input to the voice transmitting terminal device and the voice output from the voice receiving terminal device are different due to the discarding or muting processing of the voice data, the generation of abnormal noise can be suppressed as a result. The sound reproducibility in the sound transmission system may be deteriorated.

  Here, in consideration of the reproducibility of the audio signal, when an error is detected in the audio receiving terminal device, the audio signal is converted into an audio signal instead of discarding the audio signal in which the error is detected or performing a muting process. It is conceivable to cause the transmitting terminal device to transmit again. However, in this case, a process of notifying a retransmission request from the voice receiving terminal apparatus to the voice transmitting terminal apparatus and a retransmission process of the voice signal by the voice transmitting terminal apparatus are necessary. Compared to discarding and muting processing, it takes much time, so that another problem arises that the real-time property required for a voice transmission system such as a door phone system or a voice call system is lowered.

  The present invention has been made in view of the above points, and its purpose is to improve the reproducibility of sound while suppressing the generation of abnormal noise due to transmission errors, and to further suppress the deterioration of real-time characteristics. It is to provide a transmission system.

  In order to solve the above-mentioned problem, in the invention of claim 1, voice transmission comprising a voice transmitting terminal device that transmits a voice signal by a packet and a voice receiving terminal device that outputs a voice based on the received voice signal. The voice transmitting terminal device is a voice signal obtained by a voice input means for converting a received sound wave into a voice signal composed of an electrical signal. The voice signal includes a voice state including voice and a voiceless state not including voice. A discriminating unit for discriminating between the audio signal, an encoding unit that encodes the audio signal to generate audio data, a transmission unit that transmits the audio data to an audio receiving terminal device, and the audio data. When the determination result of the transmission data storage means and the determination means switches from the voiced state to the silent state, the voice data transmitted by the transmission means in the previous voiced state is transmitted again to the transmission means. Characterized in that it comprises a transmission data control means for causing.

  According to the first aspect of the present invention, the voice transmitting terminal apparatus does not always encode the voice signal obtained from the voice input means into voice data and transmits the voice data to the voice receiving terminal apparatus, but includes voice in the voice signal. Voice data is sent to the voice receiving terminal device in the voiced state, and when switching from the voiced state to the voiceless state where the voice signal does not contain voice, it was sent in the previous voiced state. Since the voice data is transmitted again to the voice receiving terminal device, the same voice data is transmitted from the voice sending terminal device to the voice receiving terminal device in the voiced state and immediately after the voiceless state. Even if a transmission error occurs, it is possible to suppress the generation of abnormal sound due to the transmission error by using the audio data that is retransmitted in the no-speech state immediately after that. Compared to the case of performing Ingu process, it can improve the reproducibility of speech, Moreover, it is possible to suppress the deterioration of the real-time.

  According to a second aspect of the invention, in the first aspect of the invention, when transmitting the voice data, the transmission means adds an error detection code for the voice data and a discrimination code indicating the discrimination result of the discrimination means to the voice data. The voice receiving terminal device receives the voice data transmitted by the sending means, the decoding means for decoding the voice data to obtain a voice signal, and the received data storage means for storing the voice data A transmission time determining means for determining whether the transmission time is in a voiced state or a silent state by using a determination code attached to the voice data for the voice data received by the receiving means; Error detection means for detecting an error with respect to the voice data received by the means using an error detection code attached to the voice data, and a voice data determined to be in a voiced state by the transmission time discrimination means. If no error is detected by the error detection means, the audio data is output to the decoding means. Thereafter, the received voice data is output until the determination result of the transmission time determination means for the received audio data is in a voiced state. When the error detection unit detects an error in the voice data determined to be in the voiced state by the transmission time determination unit without outputting the data to the decoding unit, the voice data is not output to the decoding unit, Reception data control means for waiting for reception of new audio data, and outputting the newly received audio data to the decoding means if the determination result of the transmission time determination means for the newly received audio data is in the no-voice state It is characterized by having.

  According to the invention of claim 2, when there is an error in the voice data transmitted in the voiced state, the voice data transmitted again in the immediately silent state is not decoded without decoding the voice data. Since decoding is performed, it is possible to improve the reproducibility of the audio signal while suppressing the generation of abnormal noise due to a transmission error.

  In the present invention, since the same voice data is transmitted from the voice transmitting terminal device to the voice receiving terminal device in the voiced state and in the silent state immediately after that, while suppressing the occurrence of abnormal noise due to transmission errors In addition to the effect that the reproducibility of the sound can be improved, the effect that the deterioration of the real-time property can be suppressed is also achieved.

  As shown in FIG. 1A, the audio transmission system according to the present embodiment includes a plurality of units that transmit and receive audio signals by packets (hereinafter referred to as “audio transmission packets”) via a signal line Ls serving as a transmission path. , And a time slot TSi (i = 1, 2,..., N, which will be described later), which is connected to each terminal device 2 by a signal line Ls and stores packets for call control and voice transmission between the terminal devices 2. And a main device 1 that transmits a synchronization signal SY for defining the above. Here, a balanced line such as a pair line can be used as the signal line Ls, but the signal line Ls is not limited to this example, and one pair of an unbalanced line such as a coaxial line or an enhanced category 5 or category 6 LAN cable. Alternatively, a pair of CPEV cables may be used.

  Each terminal device 2 is given a unique identification code (ID), and each terminal device 2 can be identified by this identification code (selection of a signal taken out from the signal line Ls is possible).

  As shown in FIG. 1A, the terminal device 2 according to the present embodiment includes a microphone 20a that is a sound input unit that converts a received sound wave into a sound signal including an electric signal, and a microphone that amplifies the output of the microphone 20a. It includes an amplifier 20b, a speaker 21a that is a sound output unit that transmits sound waves (outputs sound) based on the input sound signal, and a speaker amplifier 21b that amplifies the sound signal input to the speaker 21a. . Note that since the sound signal output from the microphone 20a includes sound other than sound, it is a sound signal (acoustic signal) in a strict sense. Then, it is called an audio signal.

  In addition, the terminal device 2 transmits the audio signal obtained from the microphone 20 a to the other terminal device 2 using the audio transmission packet, and the audio transmission received from the other terminal device 2. A signal processing unit 22 having a reception processing unit 24 for extracting a voice signal from the packet for transmission, and a transmission amplifier 25a for amplifying a packet signal (hereinafter referred to as “voice transmission signal”) output from the transmission processing unit 23. And a reception amplifier 25b for amplifying the audio transmission signal input to the reception processing means 24.

  As shown in FIG. 1B, the transmission processing means 23 encodes the audio signal amplified by the microphone amplifier 20b by, for example, ADPCM (Adaptive Differential Pulse Code Modulation) encoding, that is, information source encoding (Source Information source coding means 23a, which is coding means for creating voice data by coding, transmission data storage means 23b acting as a buffer for storing voice data created by the information source coding means 23a, and transmission Created by the transmission path encoding means 23c and the transmission path encoding means 23c for generating voice transmission packets by transmission path coding (Channel Coding) to transmit the voice data stored in the data storage means 23b. For example, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature AmplitudeMo modulation means 23d for generating an audio transmission signal that is modulated by 64QAM or the like and sent to the signal line Ls. In this transmission processing means 23, the transmission line coding means 23c and the modulation means 23d use the voice data created by the information source coding means 23a as another terminal device (that is, a terminal device acting as a voice receiving terminal device). ) Constitutes a transmitting means for transmitting to 2.

  Furthermore, the transmission processing unit 23 includes a determination unit 23e that determines whether the audio signal amplified by the microphone amplifier 20b is a voiced state including sound or a non-voiced state not including sound. The transmission data control means 23f which performs a predetermined | prescribed operation | movement with the discrimination | determination result of 23e is provided.

  For example, the determination unit 23e compares the amplitude of the audio signal with a threshold for audio determination, and determines that the audio signal contains audio when the amplitude of the audio signal is equal to or greater than the threshold for audio determination. Thereafter, when the period during which the amplitude of the audio signal is less than the threshold for audio determination is continued for a predetermined period or longer, it is determined that the audio signal does not contain audio. Note that the threshold value for voice discrimination is a value for discriminating whether or not voice signals having a certain amplitude or more, for example, voices intentionally uttered by the person toward the microphone 20a are included. Therefore, the determination unit 23e considers that the sound whose amplitude is less than the sound determination threshold is not sound.

  The transmission data control unit 23f sequentially outputs the audio data stored in the transmission data storage unit 23b to the transmission line encoding unit 23c while the determination result by the determination unit 23e is in a voiced state. When the discrimination result by 23e is switched from the voiced state to the silent state, the voice data output to the transmission path encoding unit 23c in the previous voiced state is output again to the transmission path encoding unit 23c. That is, the transmission data control unit 23f stores the voice data in the transmission data storage unit 23b for a certain period of time, so that when the determination result of the determination unit 23e switches from the voiced state to the voiceless state, the previous voiced state The voice data transmitted by the transmission means is sometimes transmitted again to the transmission means. For example, as shown in FIG. 2, the voice signal has a voiced state in the period T1, a voiceless state in the period T2, and a voiced state in the period T3. In the period T1, the audio data P1 corresponding to the audio signal obtained from the microphone 20a in the period T1 is given to the transmission path encoding unit 23c, and in the period T2, the present data immediately before the transmission data storage unit 23b is provided. Voice data P1, which is voice data transmitted in the voice state, is given to the transmission path encoding means 23c, and during the period T3, Audio data P2 corresponding to the audio signal obtained from the microphone 20a is to be given to the channel coding unit 23c during T3.

  Further, the transmission data control means 23f is adapted to give the determination result by the determination means 23e to the transmission line encoding means 23c.

  The transmission path encoding means 23c creates a voice transmission packet from the voice data given from the transmission data storage means 23b and sends it to the modulation means 23d. The voice transmission packet having the arranged data portion is created.

  The header portion is, for example, a preamble, an identification code (ID) indicating the terminal device 2 that is the transmission source, a packet type, a modulation method (a modulation method in the modulation means 23d, that is, any one of BPSK, QPSK, 16QAM, and 64QAM in this embodiment). And a data string in which a discrimination code indicating the discrimination result of the discrimination means 23e and a data length (data length of the packet) are arranged in the order of preamble, identification code, packet type, modulation scheme, discrimination code, and data length , And an error detection code for the data string arranged after the data string. On the other hand, the data part is composed of voice data and an error detection code for the voice data. In the terminal device 2 in the present embodiment, CRC is used as an error detection method, and the error detection code in each of the header part and the data part is an error detection code (CRC code) corresponding to the CRC. Although other error detection methods may be employed, it is desirable to use an error detection code with as low redundancy as possible as long as there is a demand for real-time communication.

  Here, while the discrimination result by the discrimination unit 23e is in a voiced state, the transmission line encoding unit 23c is given the audio data created by the information source encoding unit 23a (that is, current audio data). In this case, the voice transmission packet created by the transmission path coding means 23c is a code whose discrimination code indicates “voiced state”, and the voice data is the current voice data. Then, when the discrimination result by the discriminating means 23e is switched from the voiced state to the no voice state, the voice data (that is, the past voice data) transmitted in the immediately previous voiced state is given again. The voice transmission packet created by the means 23c is a code whose discrimination code indicates “no voice state”, and the voice data is past voice data.

  That is, the transmission processing unit 23 converts the audio signal obtained from the microphone 20a into audio data and transmits it when the audio signal is in a voiced state, and the microphone 20a when the audio signal is in the silent state. Instead of converting the obtained audio signal into audio data and transmitting it, an operation is performed in which the audio data transmitted in the past (in the previous voiced state) is transmitted again.

  As shown in FIG. 1C, the reception processing unit 24 demodulates the voice transmission signal amplified by the reception amplifier 25b to obtain a voice transmission packet, and the voice transmission unit obtained by the demodulation unit 24a. Transmission path decoding means 24b for extracting voice data and the like by decoding the transmission path of the packet, and received data storage means 24c acting as a buffer for storing the voice data extracted from the voice transmission packet by the transmission path decoding means 24b Information source decoding means 24d, which is decoding means for decoding the audio data stored in the received data storage means 24c into information source decoding (converting it into a sound signal in a format suitable for the speaker 21a) and outputting it to the speaker amplifier 21b. And. In this reception processing means 24, the demodulating means 24a and the transmission path decoding means 24b receive the voice data transmitted by the transmitting means of another terminal device (that is, the terminal device acting as the voice transmitting terminal device) 2. Receiving means for receiving is configured.

  Further, the reception processing unit 24 performs transmission to determine whether the transmission time is in the voiced state or the silent state based on the determination code attached to the voice data with respect to the voice data received by the receiving unit. A timing determination unit 24e, an error detection unit 24f that performs error detection on the voice data determined to be in a voiced state by the transmission timing determination unit 24e, using an error detection code attached to the voice data, and a transmission timing determination unit A reception data control unit 24g that performs a predetermined operation based on the determination result of 24e and the detection result of the error detection unit 24f.

  The transmission time determination unit 24e refers to the determination code included in the header portion of the voice transmission packet obtained by the demodulation unit 24a, and transmits the voice data included in the data portion of the voice transmission packet. It is configured to determine whether the time is a voiced state or a silent state and output the result to the reception data control means 24g.

  The error detection means 24f performs error detection of the header part and the data part using the error detection code of the header part of the voice transmission packet obtained by the demodulation means 24a and the error detection code of the data part. Is notified to the reception data control means 24g. In the present embodiment, as described above, the error detection code corresponding to the CRC is used, so that the error detection means 24f performs error detection by CRC.

  When the error detection means 24f detects that there is an error in the header part, the reception data control means 24g does not store the voice data contained in the voice transmission packet in the reception data storage means 24c, When no error is detected in the part, based on the determination result by the transmission time determination unit 24e and the detection result of the data part by the error detection unit 24f, that is, when the transmission time is in a voiced state or a silent state Then, one of the following operations is performed depending on whether or not the audio data is incorrect.

  If no error is detected by the error detection unit 24f in the voice data determined to be in the voiced state by the transmission time determination unit 24e (the transmission time is in the voiced state and the voice data has an error), the reception data control unit 24g If not, the audio data is output from the received data storage unit 24c to the information source decoding unit 24d. In addition, thereafter, the received data control unit 24g does not output the received audio data to the information source decoding unit 24d until the determination result of the transmission time determining unit 24e for the received audio data is in a voiced state. Therefore, even if the voice data whose transmission time is in the voiceless state is obtained after outputting the voice data whose transmission time is in the voiced state to the information source decoding unit 24d, the voice data is already decoded by the information source decoding. Since the transmission time outputted to the means 24d is the retransmission data of the voice data in the voiced state, the same voice data is not outputted from the speaker 21a.

  Further, the reception data control means 24g, when the error detection means 24f detects an error in the voice data determined to be in the voiced state by the transmission time determination means 24e (the transmission time is in the voiced state and the voice data is If there is an error), the audio data is not output to the information source decoding means 24d, and the reception of new audio data is awaited.

  If the transmission time discriminating unit 24e for the newly received audio data is in the no-voice state, and the audio data is correct, the newly received audio data is received from the received data storage unit 24c as information. It outputs to the source decoding means 24d. Here, if there is an error in the voice data, the voice data causing the waiting for reception of new voice data, that is, the voice data in which the transmission time is in the voiced state and the error is detected. Then, after performing error correction such as muting processing for replacing the audio data with a specific signal pattern (for example, a mute signal pattern) or other error countermeasure processing, it is given to the information source decoding means 24d. On the other hand, if audio data whose transmission time is in the no-voice state cannot be obtained even after a predetermined time has elapsed, as described above, the error in the audio data that caused the reception of new audio data is corrected. To the information source decoding means 24d. The error countermeasure processing method as described above is well known in the art and will not be described in detail. Further, the error countermeasure processing method is not limited to the above method, and other conventionally known methods can be adopted.

  That is, the reception processing means 24 converts the audio data into an audio signal and outputs it from the speaker 21a if the transmission timing of the received audio data is in a voiced state and there is no error, and the transmission timing of the received audio data Is in a voiced state and there is an error, the voice data is not converted into a voice signal and output from the speaker 21a, but the transmission processing means 23 waits for reception of voice data to be retransmitted in a voiceless state. If voice data whose transmission time is in the silent state is obtained within the time, the voice data is converted into a voice signal and output from the speaker 21a.

  By the way, the terminal device 2 transmits / receives a control signal between the main device 1 and the control unit 26 that controls the signal processing unit 22 and the like using the CPU as a main component in addition to the above-described configuration via the signal line Ls. The control signal transmission / reception means 27, the function of transmitting the audio transmission signal output from the transmission amplifier 25a and the control signal output from the control signal transmission / reception means 27 by frequency division multiplexing (multiplexing function) and the signal line A demultiplexing means having a function (separation function) for separating the audio transmission signal and the control signal from the signal taken from Ls and outputting the audio transmission signal to the receiving amplifier 25b and the control signal to the control signal transmitting / receiving means 27, respectively; I have.

  The terminal device 2 includes a calling means (not shown) including a call button for calling another terminal device 2 and a response means (not illustrated) including a response button for responding to a call by the other terminal device 2. And a general call button (not shown) for calling all the terminal devices 2 connected to the signal line Ls. The control means 26 and the control signal transmission / reception means 27 are configured so as to be able to perform the operations described later (operations shown in FIGS. 4 and 5), and the configuration of the control means 26 and the control signal transmission / reception means 27 is conventional. Since it is well known, detailed description is omitted.

  The main device 1 includes a control unit 10 having a CPU as a main component, a control signal transmission / reception unit 11 that transmits / receives a control signal to / from the terminal device 2, and a packet that includes synchronization data (described later) supplied from the control unit 10 ( Hereinafter, a modulation unit 12 that generates a synchronization signal SY by modulating (for example, modulation by BPSK, QPSK, 16QAM, 64QAM, etc.) and a synchronization signal SY generated by the modulation unit 12 A function of frequency-division-multiplexing the control signal output from the control signal transmission / reception means 11 and sending it to the signal line Ls, and a separation for separating the control signal from the signal taken in from the signal line Ls and outputting it to the control signal transmission / reception means 11 Multiplexing means 13 is provided. The control means 10 and the control signal transmission / reception means 11 are configured so as to be able to perform the operations described later (the operations shown in FIGS. 4 and 5). Since it is well known, detailed description is omitted.

  Incidentally, the synchronization packet has, for example, a header part and a data part arranged behind the header part. The header part includes, for example, a preamble, a packet type, a modulation method (a modulation method in the modulation means 12, that is, any one of BPSK, QPSK, 16QAM, and 64QAM in this embodiment), and a data length (data length of a synchronization packet). Is composed of a data sequence arranged in the order of preamble, packet type, modulation scheme, and data length, and an error detection code for the data sequence arranged after the data sequence. The data part is composed of the above-described actually empty synchronization data and the error detection code for the synchronization data.

  In the main device 1 and the terminal device 2, as shown in FIG. 3, the time when a predetermined time has elapsed from the falling edge of the synchronizing signal SY is set as the starting time point of the first time slot TS1, and until the next synchronizing signal SY rises. A plurality (n) of time slots TS1, TS2,..., TSn are arranged within a period (signal transmission period). That is, voice signals are transmitted and received between the terminal devices 2 by time division multiplexing access (TDMA). In the audio transmission system of this embodiment, n time slots TSi are arranged in the signal transmission period, so that a maximum of n / 2 terminal devices 2 can transmit and receive audio signals on a one-to-one basis. It has become.

  Next, the operation of the transmission system of the present embodiment, for example, the operation when performing a one-to-one call (individual call) between the two terminal devices 2 will be described with reference to FIG. In the following description, the terminal device 2 is represented by a terminal device A and a terminal device B in order to distinguish the two terminal devices 2 as necessary.

  First, when a call button for calling the terminal device B is operated in the terminal device A, the control means 26 of the terminal device A calls the call (call establishment) request data for calling the partner terminal device B, Control data (call request control data) including the other identification code (identification code of terminal device A) and the other party's identification code (identification code of terminal device B) are generated and output to control signal transmitting / receiving means 27 The control signal transmitting / receiving unit 27 modulates the call request control data obtained from the control unit 26 (for example, modulates by BPSK, QPSK, 16QAM, 64QAM, etc.) to generate a control signal (call request control signal), The signal is sent to the signal line Ls via the demultiplexing means 28 (arrow F1 in FIG. 4).

  When the control signal transmission / reception means 11 of the main apparatus 1 receives the call request control signal via the signal line Ls, the call request data included in the call request control signal and the identification code of the call source (request source). The identification code of the terminal device A and the identification code of the terminal device B, which is the identification code of the call destination (request destination), are sent to the control means 10, and the control means 10 uses the call identification code as the destination. Control data including the data (call request notification control data) is generated and output to the control signal transmission / reception means 11. The control signal transmission / reception means 11 modulates the call request notification control data obtained from the control means 10 to generate a control signal (call request notification control signal) and sends it to the signal line Ls via the demultiplexing means 13. (Arrow F2 in FIG. 4).

  When receiving the call request notification control signal through the signal line Ls, the control signal transmission / reception means 27 of the terminal device B sends the call request data included in the call request notification control signal to the control means 26. Then, a notification sound (ringing sound) is generated from the speaker 21a.

  When the response button is operated in the terminal device B after the notification sound (ringing sound) is sounded in this way and before a predetermined time has elapsed, the control means 26 of the terminal device B causes the calling terminal device A to Control data (acknowledgment control data) including acknowledgment data indicating that the individual call is accepted and the identification code of the terminal device B (identification code of the terminal device B) is generated and output to the control signal transmission / reception means 27 The control signal transmitting / receiving means 27 modulates the acknowledgment control data obtained from the control means 26 to generate a control signal (acknowledgment control signal), and sends it to the signal line Ls via the demultiplexing means 28 ( Arrow F3 in FIG.

  When the control signal transmission / reception means 11 of the main apparatus 1 receives the acknowledgment control signal via the signal line Ls, the acknowledgment data included in the acknowledgment control signal and the identification code of the call destination (request destination) The terminal device B identification code is sent to the control means 10, and the control means 10 uses the caller identification code (terminal device A identification code) as the destination and indicates call establishment notification indicating that acknowledgment data has been obtained from the call destination. Control data including the data (call establishment notification control data) is generated and output to the control signal transmission / reception means 11. The control signal transmission / reception means 11 modulates the call establishment notification control data obtained from the control means 10 to generate a control signal (call establishment notification control signal) and sends it to the signal line Ls via the demultiplexing means 13. (Arrow F4 in FIG. 4).

  In addition, after creating the control data (call establishment notification control data), the control means 10 assigns the time slot TSi to each of the calling terminal device A and the called terminal device B, and notifies the result. Control data (control data for time slot allocation) is generated and output to the control signal transmission / reception means 11. The control signal transmission / reception means 11 modulates the time slot allocation control data obtained from the control means 10 to generate a control signal (time slot allocation control signal) and sends it to the signal line Ls via the demultiplexing means 13. (Arrow F5 in FIG. 4).

  When the control signal transmitting / receiving unit 27 of the terminal apparatus 2 receives the time slot allocation control signal through the signal line Ls, the control signal transmitting unit 27 sends the time slot allocation control data to the control unit 26. Based on the control data, the demultiplexing means 28 is controlled. The control unit 26 activates the microphone 20a, the microphone amplifier 20b, the speaker 21a, the speaker amplifier 21b, the signal processing unit 22, the transmission amplifier 25a, the reception amplifier 25b, and the like.

  Thereafter, for example, when a voice is input to the microphone 20a of the calling terminal device A, the microphone 20a creates a voice signal based on the voice and outputs the voice signal to the microphone amplifier 20b, and the microphone amplifier 20b receives the voice signal. Amplified and output to the transmission processing means 23 of the signal processing means 22. As described above, the transmission processing unit 23 determines whether the voice signal is in a voiced state or a voiceless state. If the voice signal is in a voiced state, the voice signal is generated by encoding the voice signal output from the microphone 20a. A transmission packet is created, and the voice transmission packet is modulated to create a voice transmission signal and output to the transmission amplifier 25a. If there is no voice, the voice data is transmitted from the voice data transmitted in the previous voiced state. A packet is generated, and the audio transmission packet is modulated to generate an audio transmission signal and output to the transmission amplifier 25a. The transmission amplifier 25 a amplifies the audio transmission signal output from the transmission processing unit 23 and outputs the amplified audio transmission signal to the demultiplexing unit 28.

  When the demultiplexing means 28 receives the synchronization signal SY (arrow F6 in FIG. 4), the demultiplexing means 28 sends an audio transmission signal to the signal line Ls in accordance with a pre-assigned time slot TSi.

  On the other hand, when receiving the voice transmission signal whose transmission source is the terminal device A, the demultiplexing / multiplexing means 28 of the called terminal device B outputs the voice transmission signal to the reception amplifier 25b, and the reception amplifier 25b receives the voice transmission signal. Amplified and output to the reception processing means 24 of the signal processing means 22, and the reception processing means 24 performs the discrimination by the transmission time discrimination means 24e and the error detection by the error detection means 24f as described above. Based on the result, whether or not to decode the audio signal is determined from the received audio data. When the audio data is decoded by the information source decoding unit of the reception processing unit 24 and an audio signal is obtained, the audio signal is amplified by the speaker amplifier 21b and then input to the speaker 21a. Audio is output based on the received audio signal.

  The above-described operation is the same even when a voice signal is transmitted from the called terminal device B to the calling terminal device A, and the two terminal devices A and B use different time slots TSi. Then, voice signals are transmitted and received, whereby individual calls between the terminal devices A and B are performed.

  Next, an operation of the transmission system according to the present embodiment, for example, an operation when performing a many-to-many call (simultaneous call) between the three terminal apparatuses 2 will be described with reference to FIG. In the following description, the terminal device 2 is represented by a terminal device A, a terminal device B, and a terminal device C in order to distinguish the three terminal devices 2 as necessary.

  First, in the terminal device A, when the simultaneous call button for calling all the terminal devices 2 connected to the signal line Ls is operated, the control means 26 of the terminal device A transmits the other terminal devices B and C all at once. Control data (simultaneous call request control data) including the general call request data for calling and the identification code of the terminal device A (identification code of the terminal device A) is generated and output to the control signal transmitting / receiving means 27. The transmission / reception means 27 modulates the general call request control data obtained from the control means 26 to generate a control signal (simultaneous call request control signal), and sends it to the signal line Ls via the demultiplexing means 28 (FIG. 5 middle arrow G1).

  When the control signal transmission / reception means 11 of the main apparatus 1 receives the call request control signal via the signal line Ls, the call request data included in the call request control signal and the identification code of the call source (request source). The identification code of the terminal device A is sent to the control means 10, and the control means 10 has control data (simultaneous call request notification control data) including each of the identification codes of the call destinations as destinations, that is, the terminal device. The general call request notification control data destined for B and the general call request notification control data destined for the terminal device C are created and output to the control signal transmission / reception means 11. The control signal transmission / reception means 11 modulates each of the general call request notification control data obtained from the control means 10 to generate a control signal (general call request notification control signal), and the signal line Ls via the demultiplexing means 13. (Arrows G2 and G3 in FIG. 5).

  When the control signal transmission / reception means 27 of each of the terminal devices B and C, which are the general call destinations, receives the general call request notification control signal via the signal line Ls, it controls the call request data included in the general call request notification control signal. The control means 26 sounds a notification sound (calling sound) from the speaker 21a. When the response button is operated in the terminal devices B and C after the notification sound (ringing tone) is sounded in this way and before a predetermined time has elapsed, the control means 26 of the terminal devices B and C Create and control control data (acknowledgment control data) including acknowledgment data indicating that the individual terminal device A has been individually communicated and its own identification code (identification codes of the terminal devices B and C) The control signal transmitting / receiving unit 27 generates a control signal (acknowledgment control signal) by modulating the acknowledgment control data obtained from the control unit 26, and outputs the control signal via the demultiplexing / multiplexing unit 28. The signal is sent to the signal line Ls (arrows G4 and G5 in FIG. 5).

  When the control signal transmission / reception means 11 of the main device 1 receives the acknowledgment control signal from each of the terminal devices B and C through the signal line Ls, the acknowledgment data included in the acknowledgment control signal and the general call destination ( The identification codes of the terminal devices B and C, which are the identification codes of the request destination), are sent to the control means 10, and the control means 10 affirms the identification code of the simultaneous call source (identification code of the terminal apparatus A) as the destination from the call destination Control data (call establishment notification control data) including call establishment notification data indicating that the response data has been obtained is generated and output to the control signal transmission / reception means 11. The control signal transmission / reception means 11 modulates the call establishment notification control data obtained from the control means 10 to generate a control signal (call establishment notification control signal) and sends it to the signal line Ls via the demultiplexing means 13. (Arrow G6 in FIG. 5).

  Further, after creating the control data (call establishment notification control data), the control means 10 assigns a time slot TSi to each of the terminal devices A, B, and C, and provides control data for notifying the result ( Time slot allocation control data) is generated and output to the control signal transmission / reception means 11. The control signal transmission / reception means 11 modulates the time slot allocation control data obtained from the control means 10 to generate a control signal (time slot allocation control signal) and sends it to the signal line Ls via the demultiplexing means 13. (Arrow G7 in FIG. 5).

  When the control signal transmitting / receiving unit 27 of the terminal apparatus 2 receives the time slot allocation control signal through the signal line Ls, the control signal transmitting unit 27 sends the time slot allocation control data to the control unit 26. Based on the control data, the demultiplexing means 28 is controlled. The control unit 26 activates the microphone 20a, the microphone amplifier 20b, the speaker 21a, the speaker amplifier 21b, the signal processing unit 22, the transmission amplifier 25a, the reception amplifier 25b, and the like.

  Thereafter, for example, when a voice is input to the microphone 20a of the calling terminal device A, the microphone 20a creates a voice signal based on the voice and outputs the voice signal to the microphone amplifier 20b, and the microphone amplifier 20b receives the voice signal. Amplified and output to the transmission processing means 23 of the signal processing means 22. As described above, the transmission processing unit 23 determines whether the voice signal is in a voiced state or a voiceless state. If the voice signal is in a voiced state, the voice signal is generated by encoding the voice signal output from the microphone 20a. A transmission packet is created, and the voice transmission packet is modulated to create a voice transmission signal and output to the transmission amplifier 25a. If there is no voice, the voice data is transmitted from the voice data transmitted in the previous voiced state. A packet is generated, and the audio transmission packet is modulated to generate an audio transmission signal and output to the transmission amplifier 25a. The transmission amplifier 25 a amplifies the audio transmission signal output from the transmission processing unit 23 and outputs the amplified audio transmission signal to the demultiplexing unit 28. When the demultiplexing means 28 receives the synchronization signal SY (arrow G8 in FIG. 5), the demultiplexing means 28 sends an audio transmission signal to the signal line Ls in accordance with the time slot TSi assigned in advance.

  On the other hand, when the voice transmission signal whose source is the terminal device A is received by the demultiplexing and multiplexing means 28 of each of the terminal devices B and C that are the general call destinations, the voice transmission signal is received by the reception processing means via the reception amplifier 25b. 24, the reception processing means 24 performs discrimination by the transmission time discrimination means 24e and error detection by the error detection means 24f on the received voice data as described above. It is determined whether to decode the signal. When the audio data is decoded by the information source decoding unit of the reception processing unit 24 and an audio signal is obtained, the audio signal is amplified by the speaker amplifier 21b and then input to the speaker 21a. Audio is output based on the received audio signal.

  The operation described above is the same when the terminal device B transmits an audio signal or when the terminal device C transmits an audio signal, and the three terminal devices A, B, and C are in different time slots. A voice signal is transmitted and received using TSi, whereby a simultaneous call between terminal apparatuses A, B, and C is performed.

  By the way, in the above description, when each of the terminal devices B and C receives the general call request notification control signal, the terminal device B and C sound a notification sound, and then the response button is operated, whereby the acknowledgment control signal Is transmitted to the signal line Ls, and the communication between the terminal devices A, B, and C is enabled by operating the response button. The configuration may be omitted. In the above example, each of the terminal devices B and C performs signal processing so that voice input / output can be performed for a certain period of time without sounding a notification sound when receiving the control signal for simultaneous call request notification. The means 22 and the like may be activated. The certain time is extended when the audio transmission signal is received.

  In this case, the acknowledgment shown by arrows G4 and G5 in FIG. 5 and the call establishment notification shown by arrow G6 are omitted, and after the general call request notification shown by arrows G2 and G3 is sent from the main unit 1, the arrow G7 The time slot allocation notification shown in FIG. Note that the configuration in which the operation of the response button is omitted as described above can also be adopted in the example shown in FIG. 4, and in this case, the affirmative response indicated by the arrow F3 and the call establishment notification indicated by the arrow F4 are omitted.

  In the audio transmission system of the present embodiment described above, the terminal device 2 acting as an audio transmission terminal device always encodes an audio signal obtained from the microphone 20a as an audio input means into audio data, and receives the audio reception terminal device. The voice data is transmitted to the other terminal device 2 in the voiced state where the voice is included in the voice signal, and is not transmitted to the voice signal from the voiced state. When switching is performed in a silent state that is not included, the voice data transmitted in the previous voiced state is transmitted to the other terminal device 2 again.

  That is, according to the voice transmission system of the present embodiment, the terminal device 2 acting as a voice transmitting terminal device is transferred from the terminal device 2 acting as a voice receiving terminal device in a voiced state and in a voiceless state immediately thereafter. Since the same voice data is transmitted, even if a transmission error occurs and an error is detected in the voice data received in the voiced state, the voice data transmitted again in the voiceless state immediately after that is used (for example, When there is an error in the voice data transmitted in the voiced state as in the voice transmission system according to the present embodiment, the voice data transmitted again in the immediately silent state without decoding the voice data. ) Can suppress the generation of abnormal noise due to transmission errors, and can improve the reproducibility of audio compared to the case of discarding audio data or performing muting processing. In addition, since the voice signal does not include voice and the voice signal is retransmitted from the voice terminal transmitting apparatus to the voice terminal receiving apparatus in a no-voice state that is not worth transmitting in real time, the real time The decline in sex can be suppressed.

  By the way, in the terminal device 2 in the present embodiment, since the signal processing unit 22 includes the transmission processing unit 23 and the reception processing unit 24, the audio signal to be output based on the audio input from the microphone 20a is output as audio. A function as a voice transmission terminal device that converts data into a voice transmission packet and a voice reception terminal that outputs voice to the speaker 21a based on a voice signal obtained from voice data included in the received voice transmission packet It has both functions as a device. The configuration of the terminal device 2 is not limited to the above configuration, and may have only a function as a voice transmission terminal device, or only a function as a voice reception terminal device. In short, in addition to the terminal device 2 having a function as a voice transmitting terminal device among the terminal devices 2 connected by the signal line Ls, the voice receiving terminal device It is only necessary that the terminal device 2 having a function exists.

(A) is a block diagram of an audio transmission system according to an embodiment of the present invention, (b) is a block diagram of transmission processing means, and (c) is a block diagram of reception processing means. It is operation | movement explanatory drawing in the same as the above. It is a time chart of a synchronous signal and time slot in the same as the above. It is operation | movement explanatory drawing in the same as the above. It is operation | movement explanatory drawing in the same as the above.

Explanation of symbols

2 Terminal device (voice transmitting terminal device, voice receiving terminal device)
20a Microphone (voice input means)
23a Information source encoding means (encoding means)
23b Transmission data storage means 23c Transmission path encoding means 23d Modulation means 23e Determination means 23f Transmission data control means 24c Reception data storage means 24d Information source decoding means (decoding means)
24e Transmission time discriminating means 24f Error detecting means 24g Received data control means

Claims (2)

An audio transmission system comprising an audio transmitting terminal device that transmits an audio signal by a packet and an audio receiving terminal device that outputs audio based on the received audio signal,
The voice transmitting terminal device determines whether the voice signal obtained from the voice input means for converting the received sound wave into a voice signal composed of an electrical signal is a voiced state including voice or a voiceless state not including voice. Discriminating means for discriminating, encoding means for encoding the audio signal to create audio data, transmitting means for transmitting the audio data to an audio receiving terminal device, and transmission data storage means for storing the audio data And a transmission data control means for causing the transmission means to retransmit the voice data transmitted by the transmission means in the previous voiced state when the discrimination result of the discrimination means is switched from the voiced state to the no voice state. Voice transmission system. When transmitting the audio data, the transmission means transmits the audio data with an error detection code for the audio data and a determination code indicating the determination result of the determination means,
The voice receiving terminal device includes: a receiving unit that receives the audio data transmitted by the transmitting unit; a decoding unit that decodes the audio data to obtain an audio signal; a received data storage unit that stores the audio data; and a receiving unit Transmission time determination means for determining whether the transmission time is in a voiced state or in a voiceless state with respect to the received voice data by a determination code attached to the voice data, and the voice received by the receiving means An error detection means for detecting an error with respect to the data by an error detection code attached to the voice data, and an error detection means to detect no error in the voice data determined to be in a voiced state by the transmission time determination means The audio data is output to the decoding means. Thereafter, the received audio data is received until the determination result of the transmission time determining means for the received audio data is in the voiced state. If the error detection unit detects an error in the voice data determined by the transmission time determination unit as being in a voiced state without outputting the voice data to the decoding unit, Reception data control means for waiting for reception of new audio data, and outputting the newly received audio data to the decoding means if the determination result of the transmission time determination means for the newly received audio data is in the no-voice state The voice transmission system according to claim 1, further comprising:

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