JP6206756B2 - Wireless microphone system - Google Patents

Description

  The present invention relates to a wireless microphone system that transmits sound using radio waves, and in particular, transmits a sound signal to a parent device through a wireless line based on a synchronization timing established between the parent device and the parent device. The present invention relates to a wireless microphone system including a microphone.

  Wireless microphone systems that transmit radio waves using radio waves do not need to connect the microphone and the main unit (loudspeaker) with a cable, and can be flexibly adapted to the usage environment. It is used in various fields such as schools, stores and stores. In such a wireless microphone system, one configured to transmit digital audio data from a microphone to a parent device is known.

  As an example of such a system, when recording multiple audios in a studio using separate wireless microphones, the difference in transmission delay due to the transmission device that transmits each audio is eliminated. In order to achieve this, a technique is disclosed in which a transmission device stores a delay time of digital data due to internal processing and transmits delay information indicating the delay time to the reception device (Patent Document 1).

  As another example, when transmitting audio data by asynchronous transmission, the audio data sampled at a predetermined sampling period is compression-encoded, and the compressed audio data is temporarily stored, and the stored audio data is stored. A technique is disclosed in which data is sent to a predetermined transmission path, and the compression rate of compression encoding in the compression means is variably set based on the amount of audio data stored in the storage means (Patent Document 2).

  As another example, the system clock frequency of the receiving unit is set higher than that of the transmitting unit, and audio data is time-divided from the transmitting unit and included in a packet having a predetermined time length and repeatedly transmitted in units of packets. In the asynchronous digital radio communication system, a technique for delaying the reception processing time per packet of the reception unit until the underflow state of the buffer memory is resolved is disclosed (Patent Document 3).

JP 2008-258837 A JP 2002-268691 A Japanese Unexamined Patent Publication No. 2006-086779

  When time-division multiple access, which establishes synchronization between the microphone and the base unit and transmits audio signals, is applied to a wireless microphone system, the communication channel for the time-division multiple access depends on the interference status of the communication channel used. Is set dynamically. On the other hand, the audio signal transmitted from the microphone to the parent device is generally subjected to compression processing. At this time, if the compression process is executed at a fixed timing, the delay time from the voice input to the microphone to the voice reproduction by the speaker may be increased depending on the temporal relationship with the communication channel to be used. As a result, the user may feel uncomfortable in a usage environment where the sound reproduced by the parent device can be heard by the user of the microphone.

  However, the technique disclosed in Japanese Patent Laid-Open No. 2004-228561 can adjust the delay time for each audio signal when editing an audio signal input using a plurality of wireless microphones with an audio mixer or the like. As a result, the audio signal to be transmitted is limited by the transmission means having the maximum delay time.

  Further, the technique disclosed in Patent Document 2 keeps the amount of use of the buffer memory for temporarily storing the compressed audio signal constant to some extent by making the compression rate variable when performing the compression process. However, it is intended only to prevent overflow and underflow of the buffer memory when accompanying asynchronous communication, and it is not possible to reduce the audio reproduction delay itself.

  In the technique disclosed in Patent Document 3, the system clock frequency of the receiving unit is set higher than the frequency of the transmitting unit so that the buffer memory is intentionally in an underflow state. Although the reception processing time is delayed, when this configuration is introduced into a synchronous system such as time division multiple access, the delay of the reception processing extends as a result exceeding the one frame period that is the synchronization period, and the audio This leads directly to further delay in playback.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is based on the synchronization timing of a predetermined cycle established between the parent device and the parent device. In a wireless microphone system including a microphone that transmits and receives radio waves via a wireless line, a wireless microphone system capable of reducing a delay time from when a user inputs sound to the microphone until the sound starts to be played back on the parent device Is to provide.

  A wireless microphone system of the present invention is a wireless microphone system including a parent device and a microphone that transmits and receives radio waves through a wireless line based on a synchronization timing of a predetermined period established between the parent device and the microphone. Includes: an audio processing unit that generates a compressed signal by compressing an audio signal acquired for each audio capturing period set to a period equal to the predetermined period; and the compressed signal is transmitted to the master unit based on the synchronization timing. A radio unit that periodically transmits, and the audio processing unit determines a timing for starting the compression processing based on the synchronization timing.

  According to the present invention, in the microphone in which synchronization is dynamically established with the parent device by time division multiple access by the above-described configuration, based on the synchronization timing that is the timing of transmitting the compressed signal to the parent device, By determining the timing for starting the compression process of the audio signal, the compressed signal is sent to the master unit immediately after the compression process is completed. It becomes possible to shorten the delay time until the reproduction starts.

Explanatory drawing which shows the relationship between the microphone and the main | base station in the wireless microphone system which concerns on 1st Embodiment. Block configuration diagram showing the schematic configuration of the microphone in the wireless microphone system Block configuration diagram showing the microphone audio processing unit and its peripheral configuration Block configuration diagram showing the microphone radio unit and its peripheral configuration Block diagram showing the schematic configuration of the base unit in the wireless microphone system Block diagram showing the base unit audio processing unit and its peripheral configuration (A), (b), (c) is explanatory drawing explaining the frame structure of DECT. (A) is a flowchart showing the process of determining the timing of signal processing in the master unit, (b) is a flowchart showing the process of determining the timing of signal processing in the microphone. Explanatory drawing explaining the relationship between a synchronous timing, the timing which starts a compression process with a microphone, and the timing which starts a decompression process with a main | base station Explanatory drawing explaining the modification of the relationship between the timing which starts a compression process with a synchronization timing, a microphone, and the timing which starts an expansion | extension process with a main | base station. The flowchart which shows the processing content which changes a subunit | mobile_unit reception slot into a subunit | mobile_unit transmission slot in the wireless microphone system which concerns on 2nd Embodiment. Explanatory drawing explaining the relationship between a synchronous timing and the timing which starts a compression process at the time of changing a subunit | mobile_unit reception slot into a subunit | mobile_unit transmission slot in the wireless microphone system which concerns on 2nd Embodiment. In the wireless microphone system according to the second embodiment, the relationship between the synchronization timing and the timing to start the compression process when the third and fourth microphone transmission slots are further provided in addition to the first and second microphone transmission slots. Explanatory drawing to explain The flowchart which shows the processing content at the time of setting an error notification slot in the wireless microphone system which concerns on 3rd Embodiment Explanatory drawing explaining the transmission / reception state of a microphone and a main | base station when the error notification slot is set in the wireless microphone system which concerns on 3rd Embodiment. (A), (b), (c) is explanatory drawing which shows the slot structure of the control signal in the wireless microphone system which concerns on 3rd Embodiment. Explanatory drawing explaining the process which notifies error information using a control signal in the wireless microphone system which concerns on 3rd Embodiment. Explanatory drawing explaining the relationship between a synchronization timing and the timing which starts a compression process at the time of changing the transmission / reception slot in the wireless microphone system which concerns on 3rd Embodiment.

  The present invention made in order to solve the above-mentioned problems is a wireless microphone system comprising: a base unit; and a microphone that transmits and receives radio waves through a wireless line based on a synchronization timing of a predetermined period established between the base unit. The microphone includes an audio processing unit that generates a compressed signal by compressing an audio signal acquired for each audio capturing period set to a period equal to the predetermined period, and the compressed signal based on the synchronization timing. A wireless unit that periodically transmits to the base unit, and the audio processing unit determines a timing for starting the compression processing based on the synchronization timing.

  Thus, in the microphone in which synchronization is dynamically established with the parent device by time-division multiple access, the audio signal compression processing is started based on the synchronization timing that is the timing for transmitting the compressed signal to the parent device. By determining the timing, the compressed signal is sent to the master unit immediately after the compression process is completed, so the delay time from when the user inputs the sound to the microphone until the sound starts to be played on the master unit Can be shortened.

  Further, according to the present invention, the sound processing unit determines a start time of the sound capturing period based on the synchronization timing.

  As a result, the audio capturing period occurs at a constant cycle, the operation timing of the hardware is kept constant, and the capacity of the buffer memory for temporarily storing the audio signal can be reduced.

  Further, according to the present invention, the base unit and the microphone perform data transmission / reception by time division multiple access, and a frame period of the time division multiple access includes a plurality of transmission slots, and the plurality of transmission slots include Includes a first microphone transmission slot for transmitting the compressed signal from the microphone to the base unit, and the audio processing unit performs the compression processing during a transmission slot immediately before the first microphone transmission slot. The timing for starting the compression process is determined so as to be completed.

  As a result, since the compressed signal is transmitted to the base unit in the first microphone transmission slot set immediately after the compression processing is completed, in a system that performs synchronous transmission such as the DECT system, the user can send audio to the microphone. It is possible to reduce the delay time from the input until the audio starts to be played back on the master unit.

  According to the present invention, the audio processing unit starts the compression processing before the end of the audio capturing period.

  As a result, the delay time can be further shortened by executing the audio capturing and the compression processing in parallel.

  Further, according to the present invention, the frame period of the time division multiple access includes the first microphone transmission slot and a slave unit reception slot that configures one channel and transmits data from the master unit to the microphone. The base unit changes the handset reception slot to a second microphone transmission slot for transmitting the compressed signal from the microphone to the base unit in the time division multiple access frame period, and the microphone The compressed signal is transmitted using one microphone transmission slot and the second microphone transmission slot.

  Thus, by using the original slave unit reception slot as the second microphone transmission slot, two microphone transmission slots are provided in one frame period, and two synchronization timings and two voice capture periods are also provided. The delay time can be further shortened.

  In the present invention, the base unit further sets a third microphone transmission slot at an intermediate timing between the first microphone transmission slot and the second microphone transmission slot in the frame period. is there.

  Thereby, a larger number of synchronization timings are set in each frame period. As a result, the delay time can be further shortened, the operation timing of the hardware is made constant, and a stable operation is ensured.

  In the present invention, the master unit sets an error notification slot for notifying at least error information from the master unit to the microphone during the frame period.

  This makes it possible to mutually recognize the occurrence of transmission errors between the microphone and the parent device while reducing the delay time.

  In the present invention, the base unit sets a control slot for maintaining synchronization with the microphone for each frame period, and at least a part of the control slot is used as an error notification slot for notifying error information. It is intended to be used.

  As a result, the master unit can notify the microphone of the occurrence of an error without providing an independent error notification slot.

  In the present invention, the master unit further transmits a data bit field in the error notification slot.

  As a result, even if there is no vacancy in the control bit field of the control signal transmitted in the control slot, the master unit can notify the microphone of the occurrence of an error.

  In the present invention, the base unit transmits the error notification slot once in a multi-frame period composed of a plurality of the frame periods.

  This makes it possible to notify the microphone of the occurrence of an error when a transmission error occurs while normally transmitting and receiving the identification code between the microphone and the base unit to ensure pairing of both. .

  Further, according to the present invention, the master unit includes a master unit control unit that detects whether a transmission error is included in the compressed signal received from the microphone, and the master unit control unit transmits the compressed signal to the compressed signal. When it is detected that an error is included, the synchronization timing is re-established with the slave unit, and the wireless unit transmits the compressed signal based on the synchronization timing re-established with the master unit. The audio processing unit periodically transmits to the base unit, and the audio processing unit determines the timing to start the compression processing based on the reestablished synchronization timing.

  As a result, even when the slot used for transmission / reception when a transmission error occurs (that is, the synchronization timing) is changed, the compression processing start timing is dynamically changed, and the delay time can always be shortened.

  In the present invention, the base unit further includes a base unit voice processing unit that generates a voice signal by decompressing the compressed signal received from the microphone, and the base unit control unit receives the microphone from the microphone. When it is detected that a transmission error is included in the compressed signal, the master audio processing unit stops reproducing the audio signal for a period until the audio signal is generated based on the reestablished synchronization timing. It is a thing.

  As a result, when a transmission error occurs, it is possible to prevent abnormal noise from being generated from a speaker connected to or incorporated in the master unit.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram illustrating a relationship between the microphone 2 and the parent device 3 in the wireless microphone system 1 according to the first embodiment. As shown in FIG. 1, the wireless microphone system 1 includes a microphone 2, a parent device 3, and a speaker 29. The microphone 2 includes a microphone antenna 12, and the parent device 3 includes a parent device antenna 22. The microphone 2 and the parent device 3 are connected to each other via a radio line based on a synchronization timing established in a predetermined cycle. Send and receive. When the user inputs sound into the microphone 2, the sound signal is transmitted to the parent device 3 through a wireless line, and the sound is reproduced from the speaker 29 connected to the parent device 3. Note that the speaker 29 may be built in the parent device 3.

  In the first embodiment, a wireless microphone system 1 that mainly transmits and receives data according to the DECT (Digital Enhanced Cordless Telecommunications) method will be described as an example. DECT is a standard for digital cordless telephones established in 2011. It uses a frequency of 1.9 GHz (1,895,616 KHz to 1,902,528 KHz), and the communication method is TDMA-WB (time division multiple). Connection method). In DECT, communication troubles due to radio wave interference with other devices can be reduced, and 1.9 GHz, which is a frequency band to be used, does not interfere with a wireless LAN or a microwave oven. DECT is known as a method capable of communicating wideband audio data and the like, and the frequency band can be used efficiently by constantly monitoring the usage state of the frequency channel and selecting the optimum channel by the wireless microphone system 1 itself. In the first embodiment, the microphone 2 functions as a slave unit in the digital cordless telephone.

  FIG. 2 is a block configuration diagram showing a schematic configuration of the microphone 2 in the wireless microphone system 1. Hereinafter, the overall configuration of the microphone 2 will be described with reference to FIG. The microphone 2 includes a microphone control unit 10, a microphone wireless unit 11, a microphone antenna 12 connected to the microphone wireless unit 11, an operation unit 13 including a sound quality setting button as a user interface and a switch for turning on / off the power. , A display unit 14 for displaying setting contents by the operation unit 13, a storage unit 15 configured by a nonvolatile memory, a battery 16 for supplying power to each component of the microphone 2, and a dual port RAM (Random Access Memory) ) And functioning as a ring buffer, a microphone sound processing unit 18, and a microphone 19 for inputting sound.

  The microphone control unit 10 includes a CPU (Central Processing Unit) (not shown), and the CPU is configured by a ROM (Read Only Memory) or an EEPROM (registered trademark) (Electrically Erasable Programmable Read-Only Memory) storing a control program or the like. The storage unit 15 and the bus are connected. The microphone control unit 10 controls the entire microphone 2 as a control means. For example, whether or not the above-described sound quality setting button is pressed is detected by the microphone control unit 10 and the presence or absence of the pressing is recognized. Further, the microphone control unit 10 accesses the microphone wireless unit 11 and the microphone sound processing unit 18 and sets their operation timing.

  FIG. 3 is a block configuration diagram showing the microphone audio processing unit 18 and its peripheral configuration. The microphone sound processing unit 18 includes an A / D conversion unit 18a, a digital speech processor 18b, and a compression processing unit 18c. Hereinafter, signal processing up to compression processing of sound input to the microphone 19 will be described.

  The sound input to the microphone 19 is amplified to a predetermined signal level by an amplifier (not shown) to generate an analog sound signal. The analog audio signal is output to the A / D converter 18a, converted into a digital audio signal by the A / D converter 18a, and input to the digital speech processor 18b. The digital speech processor 18b performs removal, smoothing, encryption, etc. of frequency components outside the human auditory range on the digital audio signal. Of course, when music or the like is targeted as the input source of the microphone 2, the contents of the audio signal processing by the digital speech processor 18b can be changed as appropriate.

  The signal processing in the digital speech processor 18b is generally based on filtering processing by convolution operation, and may be constituted by a DSP (Digital Signal Processor) or the like specialized for these signal processing. The CPU that is not used and the digital speech processor 10c may be configured by one processor. The digital audio signal processed by the digital speech processor 18 b is temporarily stored in the memory 17.

  The digital audio signal stored in the memory 17 is output to the compression processing unit 18c. The compression processing unit 18c encodes the output of the digital speech processor 10c. The compression processing unit 18c performs a compression process on the audio signal by, for example, a CELP (Code Excited Linear Prediction coder) method, and generates a compressed signal. This compression processing is executed in synchronization with one frame period of the DECT method (generally provided at a cycle of 10 ms), and the compression processing unit 18c stores the memory for 10 ms (speech capturing period) immediately before starting the compression processing. The digital audio signal stored in the unit 17 is compressed. As described above, the one frame period and the voice capturing period are set to the same period, but the timing of starting each is shifted in time as will be described later.

  The compressed signal compressed by the compression processing unit 18 c is temporarily stored again in the memory 17 and output to the microphone radio unit 11. Here, the digital audio signal and the compressed signal before being compressed are stored in the same memory 17, but they may be provided separately.

  FIG. 4 is a block configuration diagram showing the microphone radio unit 11 and its peripheral configuration. The microphone radio unit 11 includes a frame processing unit 11a, an amplifier module 11b, and a modulation / demodulation unit 11c. Hereinafter, signal processing until the compressed signal stored in the memory 17 is transmitted from the microphone radio unit 11 will be described.

  The microphone 2 transmits the compressed signal generated by the microphone audio processing unit 18 to the parent device 3 and receives a control signal from the parent device 3. From this viewpoint, the microphone 2 is bidirectional with the parent device 3. Send and receive data. Since data is transmitted and received in both directions, the microphone radio unit 11 and the base unit radio unit 21 in the base unit 3 have a common configuration.

  The frame processing unit 11a includes a TDD / TDMA (Time Division Duplex / Time Division Multiple Access) processor (not shown). The TDD / TDMA processor divides a periodically provided frame into units called slots to enable a plurality of communications at the same frequency (time division multiple access). Thus, since the same frequency is shared and data is transmitted and received in a very short time, it is possible to make it appear as if transmission and reception are being executed substantially simultaneously. Furthermore, in TDMA, by using together FDMA (Frequency Division Multiple Access) which divides | segments a frequency band, many channels can be ensured and frequency interference can be avoided. In this way, the frame processing unit 11a periodically switches between transmission (Tx) and reception (Rx) within a short time. The structure of the DECT frame will be described later.

  The microphone control unit 10 controls the frame processing unit 11 a to set a transmission timing at which the microphone 2 transmits a compressed signal to the parent device 3. As described above, the base unit radio unit 21 of the base unit 3 has the same configuration as the microphone radio unit 11, and the base unit 3 also has the reception timing set at the same timing as the microphone 2, and the microphone 2. The compressed signal transmitted from is received.

  Hereinafter, the timing at which the microphone 2 starts transmitting the compressed signal to the parent device 3 (also the timing at which the parent device 3 starts receiving the compressed signal transmitted from the microphone 2) is referred to as “synchronization timing”. As will be described later, in the DECT system, data is transmitted and received in units of slots, and one slot for transmitting and receiving a compressed signal constitutes a channel with another pair of slots. In the following description, the timing at which other slots are generated is also included in the “synchronization timing”. That is, “synchronization timing” means “timing for generating slots used for transmission / reception”.

  The frame processing unit 11a is provided with a synchronization control unit 11d. The synchronization control unit 11d establishes the synchronization timing by matching the transmission timing of the microphone 2 and the reception timing of the parent device 3. For example, at the beginning of power-on, the microphone 2 autonomously performs a reception operation at a predetermined timing, and at that time, the synchronization control unit 11d determines that the synchronization request of the master unit 3 (how much is shifted from the timing of the slot to be synchronized). The control signal including the relative value of the data as data is continuously transmitted over a plurality of frame periods), the transmission timing of the compressed signal is determined so as to correct the shift, and the frame processing unit 11a performs the correction. Depending on the transmitted timing, arbitration of signal processing hardware is performed. The base unit 3 scans each channel in advance and selects a slot with low interference, and then makes a synchronization request. Thereby, a slot in which the microphone 2 identifies the base unit 3 and transmits a compressed signal is determined. Synchronization timing is established.

  The frame processing unit 11a includes a D / A converter and an A / D converter (not shown). The frame processing unit 11a converts the compressed signal input via the memory 17 into an analog signal by a D / A converter and outputs the analog signal to the amplifier module 11b. On the other hand, the frame processing unit 11a is input from the parent device 3 via a wireless line. The analog signal (received signal) amplified by the amplifier module 11b is converted into a digital signal by an A / D converter. As described above, an analog signal interface including the amplifier module 11b is configured between the frame processing unit 11a and the modulation / demodulation unit 11c.

  In the modulation / demodulation unit 11c, the transmission signal (analog signal) output from the amplifier module 11b is emitted from the microphone antenna 12 via a transmission circuit (not shown), and the reception signal (analog signal) received by the microphone antenna 12 is shown in the figure. Output to the amplifier module 11b via the receiving circuit.

  FIG. 5 is a block configuration diagram showing a schematic configuration of base unit 3 in wireless microphone system 1. Hereinafter, the overall configuration of base unit 3 will be described with reference to FIG.

  The base unit 3 includes a base unit control unit 20, a base unit radio unit 21, a base unit antenna 22 connected to the base unit radio unit 21, an operation unit 23 including a volume and power switch as a user interface, It comprises a display unit 24 for displaying setting contents by the operation unit 23, a storage unit 25 configured by a non-volatile memory, a power source 26 for supplying power to each component of the base unit 3, and a dual port RAM. A memory 27 that functions as a ring buffer, a master audio processing unit 28, a speaker 29 that reproduces audio, and an external interface unit 30 are included.

  Master unit 3 is connected to a telephone line (not shown) by external interface unit 30 and exchanges audio signals with other devices via the telephone line. The base unit 3 receives the audio signal from the microphone 2 via the wireless line, and thus the microphone 2 can transmit the audio signal to the telephone line via the base unit 3. Note that the external interface unit 30 may be connected to a network such as the Internet, and in this case, an audio signal can be distributed via the network.

  The base unit control unit 20 has the same configuration as the microphone control unit 10 (see FIG. 2) described above, and is coupled to the storage unit 25 formed of a nonvolatile memory by a bus or the like. The base unit control unit 20 controls the entire base unit 3 as control means, and the operation content input via the operation unit 23 is detected by the base unit control unit 20. Further, the base unit control unit 20 accesses the base unit radio unit 21 and the base unit voice processing unit 28 and sets their operation timing. In addition, base unit control unit 20 detects a transmission error of the compressed signal transmitted from microphone 2. Specifically, when the base unit radio unit 21 (see FIG. 4) receives the compressed signal transmitted from the microphone 2, an error detection field (a CRC2 field 54 (see FIG. 7) described later) is referred to. The presence or absence of a transmission error is detected.

  FIG. 6 is a block configuration diagram showing the base unit voice processing unit 28 and its peripheral configuration. The base unit voice processing unit 28 includes an expansion processing unit 28a, a digital speech processor 28b, and a D / A conversion unit 28c. Hereinafter, signal processing until the compressed signal received from the microphone 2 is reproduced by the speaker 29 will be described. Here, it is assumed that the compressed signal has already been stored in the memory 27 via the base unit radio unit 21.

  The compressed signal stored in the memory 27 is output to the decompression processing unit 28a, and the decompression processing unit 28a decompresses (decodes) the compressed signal received in slot units and stored in the memory 27 into a digital audio signal. This decompression process is executed in synchronization with one frame period of the DECT method, and the decompression processing unit 28a outputs a digital audio signal to be reproduced by the parent device 3 during 10 ms (audio reproduction period) immediately after the decompression process is executed. Generate. As described above, the one frame period and the audio reproduction period are set to the same cycle, but the timing of starting each is shifted in time as will be described later.

  The digital audio signal expanded by the expansion processing unit 28a is temporarily stored again in the memory 27 and output to the digital speech processor 28b. Here, the compressed signal before decompression and the digital audio signal after decompression are stored in the same memory 27, but they may be provided separately.

  The digital speech processor 28b performs processing for emphasizing a specific voice frequency (restoration of the frequency component removed by the filter processing of the digital speech processor 18b of the microphone 2) or encrypting the digital voice signal for the expanded digital voice signal. If so, decryption or the like is performed. The digital speech processor 28b outputs a digital audio signal to the D / A converter 28c.

  The digital audio signal is input to the D / A converter 28c and converted into an analog audio signal. The analog audio signal is amplified by an amplifier (not shown) and reproduced by a speaker 29.

  As described above, the basic configuration and function of the base radio unit 21 are substantially the same as those of the microphone radio unit 11 described with reference to FIG. Therefore, detailed description of these in the base unit 3 is omitted.

  FIGS. 7A, 7B, and 7C are explanatory diagrams illustrating the DECT frame configuration. As shown in FIG. 7 (a), the DECT method generally includes 24 slots (12 slots for the uplink and 12 slots for the downlink) in one frame period of a 10 ms period. Normally, the slots S0 to S11 are from the main unit 3 to the microphone 2 (hereinafter, the microphone 2 may be referred to as “slave unit 2” when explaining the DECT slot configuration and data transmission / reception sequence). The slots S12 to S23 are used for communication from the slave unit 2 to the master unit 3. That is, in this example, when viewed from the handset 2 side, S0 to S11 are handset receiving slots 61, and S12 to S23 are handset sending slots 60, respectively. In communication between the master unit 3 and the slave unit 2, slots having a positional relationship of 5 ms apart (slot S0 and slot S12, slot S1 and slot S13) are used in combination (pair slot). One channel is configured.

  In the DECT method, the number of channels per carrier in the time division multiple access method is allowed to be 6, 7, 8, 9, 10, 11 or 12, and is used by the parent device 3 and the child device 2. The number of channels is determined when establishing the synchronization timing described above.

  At least one slot (for example, slot S0) among the 12 slots (slave unit reception slot 61) in which transmission from the base unit 3 to the handset 2 is performed is a control slot for sending a control signal. The control signal is always (periodically) transmitted from the parent device 3 in one slot in the frame. When an idle slot (for example, slot S0) is used as a control slot in preparation for the occurrence of radio wave interference during control communication from the master unit 3 to the slave unit 2, the slots S1 to S1 are used. For the slot S11, it is detected whether or not the slot is being used by another device (that is, the presence or absence of interference). If radio interference or the like actually occurs in the slot S0, the control slot may be moved to the slot S1. . In conjunction with this, a response slot for the control slot (slot used for response to the control slot; used when data is transmitted from the slave unit 2 to the master unit 3) is set in the slot S13.

  Further, apart from the control slot, a slot for transmitting and receiving an audio signal or the like between the parent device 3 and the child device 2 is determined, thereby establishing the “synchronization timing” described above. Which slot is used as a control slot or a slot for transmitting / receiving an audio signal or the like is dynamically determined according to a radio wave condition or the like when the parent device 3 and the child device 2 perform transmission / reception.

  As shown in FIG. 7B, each slot is defined with a width of 416.67 μs (= 10 ms / 24), and in each slot, a synchronization signal field 50, a control bit field 51, a CRC1 field 52, and a data bit A field 53 and a CRC2 field 54 are defined.

  The synchronization signal field 50 includes fixed data composed of a data string for bit synchronization and a data string for slot synchronization. In the CRC1 field 52, a CRC (Cyclic Redundancy Check) code calculated based on the data string of the control bit field 51 is written, and a transmission error in the control bit field 51 is detected. Similarly, the CRC2 field 54 detects a transmission error in the data bit field 53.

  As shown in FIG. 7C, the control bit field 51 includes a header 51a and a message area 51b. The message area 51b is a field for passing a control signal from the parent device 3 to the child device 2, and exchanges a control signal necessary at the time of outgoing / incoming call and waiting. Specifically, the control signal includes identification information (so-called ID), device capability, communication quality, call setup / disconnection, retransmission control signal when a transmission error is detected, and new information when changing a slot used for transmission / reception. It is possible to add information about the slot used for the.

  On the other hand, the data bit field 53 is a field for storing packets such as an audio signal and an image signal. In the wireless microphone system 1, when a compressed signal is transmitted from the child device 2 to the parent device 3, a bit string of the compressed signal is written in the data bit field 53.

  FIG. 8A is a flowchart showing a process of determining the timing of signal processing in the base unit 3, and FIG. 8B is a flowchart showing a process of determining the timing of signal processing in the microphone 2. Hereinafter, the process of signal processing in the wireless microphone system 1 of the first embodiment will be described with reference to FIGS.

  Since the base unit 3 and the microphone 2 operate in cooperation with each other due to the nature of the DECT method, the processes in FIGS. 8A and 8B proceed simultaneously. Hereinafter, description will be made on the assumption that the processes of the base unit 3 and the microphone 2 proceed simultaneously. When the power of the parent device 3 is turned on, the parent device 3 confirms whether voice communication is started (ST801). Specifically, base unit 3 continuously transmits the above-described synchronization request at a predetermined cycle (for example, 2 seconds) for at least a longer period than the initial reception cycle of handset 2. When the microphone 2 returns a response to this synchronization request, it is determined that voice communication has started. When base unit 3 determines that voice communication has started (Yes in ST801), it determines whether a slot to be used for transmission / reception has been determined (ST802). If voice communication is not started, the process returns to ST801.

  Whether or not voice communication is started is confirmed also in the microphone 2 (ST811). Specifically, the microphone 2 determines that the voice communication has been started when the synchronization request transmitted from the parent device 3 is detected. If it is determined that voice communication is started (Yes in ST811), microphone 2 determines whether a slot to be used for transmission / reception has been determined (ST812). When voice communication is not started (No in ST811), the process returns to ST811.

  As described above, base unit 3 (base unit radio unit 21 (see FIG. 5)) selects a slot (channel) that is determined to be less affected by interference or the like. Then, the synchronization request transmitted by the base unit radio unit 21 includes time difference information relative to the selected slot. The microphone radio unit 11 (see FIG. 2) receives a signal from the base unit 3 at a predetermined cycle (initial reception cycle, for example, 0.5 seconds) after power-on, and acquires time difference information included in the synchronization request. . Based on this time difference information, the microphone radio unit 11 determines a slot that the microphone 2 uses for transmission / reception with the parent device 3, that is, determines “timing for generating a slot used for transmission / reception”. Specifically, the time difference information included in the synchronization request transmitted from the base unit radio unit 21 to the microphone 2 is converted into an A / D converter (see FIG. 4) provided in the frame processing unit 11a (see FIG. 4) of the microphone radio unit 11. The microphone wireless unit 11 determines the synchronization timing by adding the numerical data of the time difference information to the timing at which the time difference information is actually received. The microphone wireless unit 11 notifies the parent device 3 that transmission / reception is performed in the slot selected by the parent device 3.

  That is, the microphone radio unit 11 determines that the slot to be used is determined when the slot for transmitting and receiving is determined based on the time difference information in ST812. In ST802, base station radio section 21 determines that the slot to be used has been determined when notifying that transmission / reception is performed in the slot selected by base station radio section 21. When the slot to be used is not determined (No in ST802 and ST812), the base unit 3 returns to ST802, and the microphone 2 returns to ST812.

  When the use slot is determined (Yes in ST802), base unit radio section 21 notifies base unit control section 20 of the timing for generating the use slot for transmission / reception (ST803). The base radio unit 21 designates a slot to be used for transmission and reception, and the synchronization timing is known information.

  On the other hand, when the use slot is determined (Yes in ST812), microphone radio section 11 notifies synchronization timing to microphone control section 10 (ST813). The synchronization timing is transferred to the microphone control unit 10 and stored in the storage unit 15 (see FIG. 2).

  Next, base unit radio section 21 notifies base unit voice processing section 28 of the synchronization timing (ST804). Since the synchronization timing is passed to the parent device control unit 20 as described above, the parent device control unit 20 may set the synchronization timing in the parent device voice processing unit 28. The notification of the synchronization timing corresponds to the path indicated by the broken line in FIG.

  On the other hand, the microphone radio unit 11 notifies the microphone audio processing unit 18 of the synchronization timing (ST814). Since the synchronization timing is passed to the microphone control unit 10 as described above, the microphone control unit 10 may set the synchronization timing. The notification of the synchronization timing corresponds to the path indicated by a broken line in FIG.

  Next, base audio processing unit 28 determines the start timing of the expansion processing in expansion processing unit 28a (see FIG. 6) based on the notified synchronization timing (ST805). Alternatively, the playback timing of the audio expansion signal may be determined only once after the slot to be used is determined, and thereafter, the expansion timing start timing may be determined based on the synchronization timing. Moreover, the microphone sound processing unit 18 determines the start timing of the compression processing in the compression processing unit 18c (see FIG. 3) based on the notified synchronization timing (ST815). The microphone audio processing unit 18 may also determine the reproduction timing of the audio expansion signal only once after determining the slot to be used, and thereafter determine the expansion processing start timing based on the synchronization timing.

  FIG. 9 is an explanatory diagram for explaining the relationship between the synchronization timing, the timing at which the compression process is started by the microphone 2, and the timing at which the expansion process is started by the parent device 3. In FIG. 9, only the slot number is displayed in the slot configuration, but as described above, it is described as slot S0. Also, in FIG. 9, for the sake of simplicity of explanation, the control slot and the slot responding thereto are not shown (the same applies to FIGS. 10, 12, 13, 15, and 18). .

  In FIG. 9, the synchronization timing is established through the processes of ST801 to ST802 (base unit 3) and ST811 to ST812 (microphone 2) described with reference to FIG. 8, and ST803 to ST805 (base unit 3). Through the steps ST813 to ST815 (microphone 2), the base unit audio processing unit 28 determines the timing for starting the decompression of the compressed data, and the microphone audio processing unit 18 determines the timing for starting the compression of the digital audio data. It is assumed that

  In FIG. 9, “slave unit transmission slot 60” shown in the slot configuration is a slot that can be used when the microphone 2 transmits a compressed signal to the base unit 3, and “slave unit reception slot 61” is It means a slot that can be used when the microphone 2 receives a control signal or the like from the parent device 3. As shown in FIG. 9, the microphone 2 and the parent device 3 are synchronized at the synchronization timings TS1 and TS2, and the microphone 2 uses the slot S16 (first microphone transmission slot) starting from the synchronization timing TS1. The compressed signal is transmitted to the base unit 3. The “audio compression frame” means a period during which a digital audio signal to be subjected to compression processing is captured, and is set to a period of 10 ms, which is equal to the period of the synchronization timing TS1.

  As described above, in the microphone sound processing unit 18, the timing at which the compression processing unit 18c (see FIG. 3) starts the compression processing is determined based on the synchronization timing (here, TS1). The time required for the compression process is proportional to the number of operations performed by the compression algorithm. In CELP, since the frame length, compression rate, and bit rate are known according to the sound quality setting, the number of operations is also known, and the processing time can be calculated in advance. Therefore, if the synchronization timing TS1 is determined, the timing for starting the compression processing (compression processing start timing TC1) based on the synchronization timing TS1 is set immediately before the start of the slot (slot S16) for transmitting the compressed signal (ie, the synchronization timing TS1). Can be set to In relation to the slot configuration, the compression processing start timing TC1 is determined such that the completion (end) of the compression processing is in the slot S15 period immediately before the slot S16 starting from the synchronization timing TS1. In this way, since the compressed signal is transmitted to the base unit 3 at the synchronous timing TS1 set immediately after the compression process is completed, the user can use the microphone in a system that performs synchronous transmission such as the DECT method. It is possible to reduce the delay time from when the sound is input to 2 until the sound starts to be played back by the master unit 3.

  The compression processing unit 18c (see FIG. 3) executes the compression process immediately after taking the digital audio signal into the memory 17 (see FIG. 3) in the audio compression frame. The end TVG2 substantially coincides with the compression processing start timing TC1, and as a result, the start TVG1 of the audio compression frame is also determined based on the synchronization timing. As a result, audio compression frames are generated at a constant cycle, the operation timing of the hardware is kept constant, and the capacity of the memory 17 functioning as a buffer memory for temporarily storing audio signals can be reduced. .

  The user of the wireless microphone system 1 can select the quality of the audio signal by operating the operation unit 13 (see FIG. 2). When the user designates high sound quality, the number of samplings in the audio compression frame increases, so the compression processing start timing TC1 is set earlier. Conversely, when the user designates a low sound quality, the number of samplings in the audio compression frame decreases, so the compression processing start timing TC1 is set later. By changing the timing at which the compression processing unit 18c starts the compression process according to the sound quality setting, the effect of reducing the delay time is maintained even if the sound quality setting is changed. Further, with the change of the compression processing start timing TC1, the position on the time axis of the audio compression frame period (TVG1 to TVG2) is shifted back and forth.

  The compressed signal is transmitted to the parent device 3 using the slot S16 starting from the synchronization timing TS1. That is, the timing at which the base unit 3 starts to receive the compressed signal is also the synchronization timing TS1. When reception of the compressed signal is completed, base unit 3 starts expansion processing by expansion processing unit 28a (see FIG. 6) at expansion processing start timing TE1 and converts it into a digital audio signal. The decompression process is also proportional to the number of samplings, and the time required for the decompression can be calculated in advance, and immediately after executing the decompression process, the sound is reproduced by the above-mentioned master audio processing unit 28. Playback is seamless.

  “Audio decompression frame” shown in FIG. 9 means a period for reproducing the decompressed digital audio signal. The expansion processing start timing TE1 is also the end of the slot S16, and as described with reference to FIG. 7, the length of one slot period is already known (416.67 μs), so that the expansion processing by the expansion processing unit 28a is also synchronized. It is started based on the timing TS1. Audio decompression frames are generated at regular intervals (here, 10 ms), the hardware operation timing can be kept constant, and the capacity of the memory 27 functioning as a buffer memory for temporarily storing audio signals can be reduced. It becomes.

  In the sequence shown in FIG. 9, after the user inputs sound into the microphone 2, the sound compression frame + compression processing time + transmission (reception) time + expansion from when the sound is started to be reproduced by the parent device 3 Although the processing time is delayed, the compressed signal is transmitted to the parent device 3 immediately after the compression processing. Therefore, the time from when the user inputs the sound to the microphone 2 until the sound starts to be reproduced by the parent device 3. The delay time is minimized.

  Further, the microphone 2 receives the error information transmitted from the parent device 3 using the slot S4 starting from the synchronization timing TS2. In this error information, in addition to notification when an error (determined using the CRC2 field 54 shown in FIG. 7) is detected in the compressed signal received by the base unit 3 from the microphone 2, the radio wave condition is deteriorated. When a slot to be used is changed, information on a slot number to be newly used is included.

  FIG. 10 is an explanatory diagram for explaining a modification of the relationship between the synchronization timing, the timing at which the compression process is started by the microphone 2, and the timing at which the expansion process is started by the parent device 3. Also in the modified example, in the microphone sound processing unit 18, the timing at which the compression processing unit 18c (see FIG. 3) starts the compression processing is determined based on the synchronization timing TS1, and the completion (end) of the compression processing determines the synchronization timing TS1. The compression processing start timing TC1 is determined so as to be in the slot S15 period immediately before the starting slot S16.

  In the modification, an algorithm that performs sequential processing such as ADPCM is assumed as a compression method. In this case, as shown in the drawing, the compression process can be started from the compression process start timing TC1 set before the final TVG2 of the audio compression frame. The end of the compression process is made to coincide with the end TVG2 of the audio compression frame. As described above, since the memory 17 of the microphone 2 has a dual port configuration, the microphone audio processing unit 18 writes the output of the digital speech processor 18b into the memory 17, and at the same time, the compression processing unit 18c performs the memory 17 (both shown in FIG. 3), that is, the voice capturing and the compression processing can be executed in parallel.

  In the modification, the base unit voice processing unit 28 (see FIG. 6) of the base unit 3 starts the decompression process of the compressed signal transmitted at the synchronization timing TS1 from the decompression process start timing TE1 and immediately in the speech decompression frame. Start audio playback. Also in the main unit 3, since the memory 27 has a dual port configuration, writing to and reading from the memory 27 can be performed in parallel as in the case of the microphone 2. As described above, in the sequence of the modification shown in FIG. 10, the delay time that occurs from when the user inputs audio to the microphone 2 until the audio starts to be reproduced by the parent device 3 is theoretically the audio compression frame + transmission. (Reception) time + decompression processing time, and the delay time can be further shortened.

  The configuration of the modified example is particularly useful when a compression process executed by the microphone 2 and an expansion process executed by the parent device 3 require a relatively long time. In the modified example, since the time required for compression processing and decompression processing does not need to exceed one frame period in theory, it is not necessary to increase the speed of these processes, reduce the operating clock, reduce power consumption, Hardware resources and the like can be reduced in cost.

(Second Embodiment)
In the first embodiment, as described with reference to FIG. 9, the “slave unit transmission slot 60” is a slot that can be used when the microphone 2 transmits a compressed signal to the base unit 3. The slot 61 ”is a slot that can be used when the microphone 2 receives error information or the like from the parent device 3. In the second embodiment, the slave unit reception slot 61 is changed to the slave unit transmission slot 60 for use. In the DECT system, it is possible to change the slot attributes in this way.

  FIG. 11 is a flowchart showing the processing contents for changing the slave unit reception slot 61 to the slave unit transmission slot 60 in the wireless microphone system 1 according to the second embodiment. Hereinafter, in FIG. 11, processing in the microphone 2 will be described for the sake of simplicity. However, as described with reference to FIG. 8 in the first embodiment, the microphone 2 and the parent device 3 actually cooperate with each other. Is proceeding.

  In FIG. 11, the determination as to whether or not voice communication has been started (ST1101) and the determination as to whether or not the slot to be used for transmission / reception has been determined (ST1102) is the same as ST811 and ST812 described above, respectively. Omitted. By ST1102, the slot used for transmission / reception between microphone 2 and base unit 3 is determined, that is, the synchronization timing is determined. By establishing synchronization, the microphone 2 and the parent device 3 can transmit and receive data to and from each other.

  As described above, the base unit radio unit 21 (see FIG. 5) of the base unit 3 periodically transmits error information and the like to the microphone 2, and the base unit 3 includes the slave unit reception slot in the error information. A command for changing 61 to the slave unit transmission slot 60 is added and transmitted to the microphone 2. This command can be written in the data bit field 53 (see FIG. 7) described above. Receiving this command, the microphone radio unit 11 (see FIG. 4) sends the contents of the data bit field 53 to the microphone control unit 10 (see FIG. 4), and the microphone control unit 10 extracts the command from the data bit field 53. The microphone control unit 10 controls the frame processing unit 11a (see FIG. 4) according to the command to change the slot used as the slave unit reception slot 61 to the slave unit transmission slot 60 (second microphone transmission slot). (ST1103).

  As a result, the microphone 2 can transmit the compressed signal to the base unit 3 using the second microphone transmission slot in addition to the first microphone transmission slot used previously. That is, in the second embodiment, the slot that transmitted error information and the like from the master unit 3 to the microphone 2 before issuing the command is used as the second microphone transmission slot.

  Thereafter, the microphone radio unit 11 notifies the microphone control unit 10 of the synchronization timing (ST1104). In the second embodiment, the synchronization timing is notified for two of the first microphone transmission slot and the second microphone transmission slot. The synchronization timing is transferred to the microphone control unit 10 and stored in the storage unit 15 (see FIG. 2 for both).

  Further, the microphone radio unit 11 notifies the microphone audio processing unit 18 of the synchronization timing (ST1105), and the microphone audio processing unit 18 performs compression in the compression processing unit 18c (see FIG. 3) based on the notified synchronization timing. The processing start timing is determined (ST1106). In the second embodiment, the start timing of the compression process is determined for each of the first microphone transmission slot and the second microphone transmission slot.

  FIG. 12 is an explanatory diagram for explaining the relationship between the synchronization timing and the timing to start the compression process when the handset reception slot 61 is changed to the handset transmission slot 60 in the wireless microphone system 1 according to the second embodiment. It is. As described with reference to FIG. 11, in the second embodiment, the original slave unit reception slot 61 is changed to the slave unit transmission slot 60. Each of the two slave unit transmission slots is provided with a period of 5 ms.

  In FIG. 12, slot S16 corresponds to the first microphone transmission slot and corresponds to the synchronization timing TS1. The slot S4 corresponds to the second microphone transmission slot and corresponds to the synchronization timing TS2. Also in the second embodiment, the compression processing start timing is determined based on the synchronization timing. That is, based on the synchronization timing TS1, the compression processing start timing TC1 for the digital audio signal to be transmitted in the first microphone transmission slot (slot S16) (the audio compression frame that is the capture period is the period from TVG1 to TVG2) is determined. Based on the synchronization timing TS2, the compression processing start timing TC2 for the digital audio signal to be transmitted in the second microphone transmission slot (slot S4) (the audio compression frame is a period from TVG2 to TVG3) is determined.

  The compression processing start timing TC1 is determined so that the compression processing is completed during the slot S15 immediately before the slot S16 starting from the synchronization timing TS1, and the compression processing start timing TC2 is set to the slot S4 starting from the synchronization timing TS2. It is determined so that the compression process is completed during the slot S3 immediately before. Further, the start time (TVG1, TVG2,...) Of the audio compression frame is determined based on the synchronization timing TS1.

  The compressed signals transmitted from the microphone 2 to the master unit 3 in the slots S16 and S4 are expanded in the master unit 3 at the expansion process start timings TE1 and TE2, respectively.

  In the second embodiment, by using the original slave unit reception slot 61 as the slave unit transmission slot 60, two slave unit transmission slots 60 are provided in one frame period (10 ms), and the audio compression frame, compression Each of the processing, transmission (reception), decompression processing, and voice decompression frame is executed at a cycle of 5 ms. As a result, the delay time is halved by about half compared to the first embodiment. In the second embodiment, as described with reference to FIG. 10, the delay time is further reduced by executing the audio capturing and the compression process in parallel.

  FIG. 13 shows the synchronization timing and compression processing when the wireless microphone system 1 according to the second embodiment further includes third and fourth microphone transmission slots in addition to the first and second microphone transmission slots. It is explanatory drawing explaining the relationship with a timing. FIG. 13 shows a modification of the second embodiment.

  In this modification, in addition to the slot S16 of the child device transmission slot 60 and the slot S4 of the original child device reception slot 61, the slot S22 of the child device transmission slot 60 and the slot S10 of the original child device reception slot 61 are This is used as a slot for transmitting a compressed signal from the microphone 2 to the base unit 3. Here, the slot S22 corresponds to a third microphone transmission slot, and the slot S10 corresponds to a fourth microphone transmission slot. Thus, in the modification, four microphone transmission slots are set in one frame period (10 ms).

  Also in the modified example, the compression processing start timings TC1 to TC4 are determined based on the synchronization timings TS1 to TS4, and the compression signal is transmitted from the microphone 2 to the parent device 3 based on the synchronization timings TS1 to TS4. When the signal is received, the voice expansion process is started at the timings TE1 to TE4.

  In the modification, the start of the third microphone transmission slot (slot S22) is the synchronization timing TS3, and the synchronization timing TS3 is the start of the first microphone transmission slot (slot S16) (synchronization timing TS1) and the second microphone transmission slot ( The timing is set to an intermediate timing from the start (synchronization timing TS2) of the slot S4). That is, here, the synchronization timing TS3 is provided with a time interval of 2.5 ms with respect to both the synchronization timings TS1 and TS2. That is, each of the audio compression frame, compression processing, transmission (reception), expansion processing, and audio expansion frame is executed at a cycle of 2.5 ms. That is, four transmission timings are set for each frame period. As a result, the delay time is further shortened compared to the second embodiment.

  When a new microphone transmission slot is provided, the start (synchronization timing) of each microphone transmission slot is performed at a constant period, so that the microphone control unit 10, the microphone radio unit 11, and the microphone sound processing unit 18 in the microphone 2 ( 2) and the base unit control unit 20, the base unit radio unit 21, and the base unit voice processing unit 28 (see FIG. 5) of the base unit 3, the operation timing of the hardware is made constant and stable. Operation is ensured.

(Third embodiment)
As described above, in the second embodiment and its modification, the original slave unit reception slot 61 is diverted to the slave unit transmission slot 60. For this reason, even when a transmission error is detected in the compressed signal transmitted from the microphone 2 in the base unit 3, such as when the wireless microphone system 1 is used in an environment where the radio wave condition is unstable, error information is notified to the microphone 2. It is assumed that it is impossible.

  FIG. 14 is a flowchart showing the processing contents when an error notification slot is set in the wireless microphone system 1 according to the third embodiment. In the third embodiment, in addition to the plurality of microphone transmission slots described in the second embodiment (see FIGS. 12 and 13), a new error notification slot for notifying error information from the parent device 3 to the microphone 2 is provided. ing. In FIG. 14, the processing in the microphone 2 will be described for the sake of simplicity. However, as described with reference to FIG. 8 in the first embodiment, the microphone 2 and the parent device 3 actually cooperate with each other. We are proceeding with the process.

  In FIG. 14, the determination as to whether or not voice communication has been started (ST1401) and the determination as to whether or not a slot to be used for transmission / reception has been determined (ST1402) are equivalent to ST811 and ST812 described above, respectively. Omitted. By ST1402, a slot used for transmission / reception between microphone 2 and base unit 3 is determined, that is, a synchronization timing is determined. By establishing synchronization, the microphone 2 and the parent device 3 can transmit and receive data to and from each other.

  As described above, the base unit radio unit 21 (see FIG. 5) of the base unit 3 periodically transmits a control signal to the microphone 2 using the control slot. A command for changing the machine reception slot 61 to the child machine transmission slot 60 and a command for designating a slot used as an error notification slot are added to the microphone 2 and transmitted. In accordance with the command, microphone control unit 10 (see FIG. 2) changes the slot used as slave unit reception slot 61 to slave unit transmission slot 60 (ST1403).

  Furthermore, microphone control unit 10 controls microphone radio unit 11 according to the command to establish a transmission / reception slot (error notification slot) for error notification (ST1404). When base unit 3 detects that there is a transmission error in the compressed signal received from microphone 2, it notifies microphone 2 using the error notification slot. On the other hand, when microphone 2 detects that there is a transmission error in the control signal transmitted from base unit 3 or the information contained in the error notification slot, it notifies base unit 3 using the error notification slot (ST1405).

  When the frequency of occurrence of transmission errors exceeds a predetermined frequency, base unit 3 transmits a control signal including a command for changing the microphone transmission slot. When the transmission of the control signal itself includes a transmission error, the control signal is repeatedly transmitted from the parent device 3 until the slot change is negotiated between the microphone 2 and the parent device 3. When microphone 2 normally receives the command, microphone 2 changes the microphone transmission slot used for transmitting the compressed signal (ST1406).

  FIG. 15 is an explanatory diagram for explaining a transmission / reception situation between the microphone 2 and the parent device 3 when an error notification slot is set in the wireless microphone system 1 according to the third embodiment. FIG. 15 shows a state in which an error notification slot is added in a situation where the slave unit reception slot 61 described with reference to FIG. 12 is changed to the slave unit transmission slot 60.

  In FIG. 15, a slot S16 starting from the synchronization timing TS1 is a first microphone transmission slot for transmitting a compressed signal from the microphone 2 to the parent device 3, and a slot S4 starting from the synchronization timing TS2 is also sent from the microphone 2 to the parent device. 3 is a second microphone transmission slot for transmitting a compressed signal to 3. The slot S18 starting from the timing TS10 is a first error notification slot for transmitting error information from the microphone 2 to the parent device 3, and the slot S16 starting from the timing TS20 is an error from the parent device 3 to the microphone 2. This is a second error notification slot for transmitting information. The first error notification slot and the second error notification slot are provided 5 ms apart from each other and constitute one error notification channel. In this error notification channel, error information is transmitted from the microphone 2 to the parent device 3 in the child device transmission slot 60 in accordance with the principle of the DECT method, and error information is transmitted from the parent device 3 to the microphone 2 in the original child device reception slot 61. Is done.

  As described above, when the slave unit reception slot 61 is changed to the slave unit transmission slot 60, an error notification slot (channel) is added so that the user inputs voice to the microphone 2 and then the master unit 3 While shortening the delay time until the sound starts to be reproduced, it is possible to mutually recognize the occurrence of transmission errors between the microphone 2 and the parent device 3.

  Hereinafter, the timing for setting the error notification channel will be described with reference to FIG. In FIG. 13, TS1, TS2, TS3, and TS4 are used as synchronization timings, respectively, as microphone transmission slots for transmitting a compressed signal from the microphone 2 to the base unit 3. However, if the number of microphone transmission slots is increased from this state, TSX1 ( Add four synchronization timings of slot S13, TSX2 (start of slot S19), TSX3 (start of slot S1), and TSX4 (start of slot S7) (ie, out of a total of 24 slots, time In other words, eight slots provided at equal intervals can be used as microphone transmission slots. That is, if the start of the slot S0 is determined as the synchronization timing, the slot S [3 × n] (n = 0 to 7) can be set as the microphone transmission slot.

  Theoretically, all 24 slots can be used as microphone transmission slots, but error notification is difficult, and there are no frequency switching destinations for 12 slots (since there is only one available timing). , System trouble occurs. For this reason, in the embodiment, eight microphone transmission slots are set. Then, an error notification slot is set in a slot other than the slot S [3 × n] (n = 0 to 7), that is, a slot that is unlikely to start synchronization timing is selected and set as an error notification slot. It is preferable.

  Actually, the beginning of the error notification slot shown in FIG. 15 (TS10 and TS20) is “other than the slot S [3 × n] (n = 0 to 7) when the beginning of the slot S0 is determined as the synchronization timing. This meets the requirement that the slot is used as an error notification slot. In this way, an error notification slot can be added without affecting the hardware configuration.

  FIGS. 16A, 16B, and 16C are explanatory views showing a slot configuration of a control signal in the wireless microphone system 1 according to the third embodiment, and FIG. 17 is a wireless microphone system 1 according to the third embodiment. FIG. 3 is an explanatory diagram illustrating a process of notifying error information using a control signal. Hereinafter, notification of error information using a control signal will be described with reference to FIG. In FIG. 16, the CRC1 field 52 and the CRC2 field 54 for detecting transmission errors shown in FIG. 7 are omitted.

  As described above, in the wireless microphone system 1, the control signal is transmitted from the parent device 3 to the microphone 2 once per frame period (here, 10 ms). In the DECT system, an identification code for identifying a transmission / reception pair and call control information are usually written in the control bit field 51. This identification code or the like is defined as 40 bits for the base unit 3 and 36 bits for other than the base unit. That is, in the control signal, the message area 51b is used as an area for writing an identification code, and the data bit field 53 is used to transmit other information. However, other information can be written in the control bit field 51 instead of the identification code or the like.

  As shown in FIG. 16A, the control signal transmitted from the parent device 3 to the microphone 2 is composed of a synchronization signal field 50 and a control bit field 51. As shown in FIG. 16B, the control signal transmitted from the microphone 2 to the parent device 3 is composed of a synchronization signal field 50, a control bit field 51, and a data bit field 53. When the microphone 2 detects a transmission error, the microphone 2 writes a predetermined flag in the control bit field 51 and transmits it to the master unit 3. The microphone 2 writes a compressed signal obtained by compressing the digital audio signal in the data bit field 53 and transmits it to the parent device 3.

  The control signal transmitted to the microphone 2 by the base unit 3 can be expanded as shown in FIG. 16C. The base unit 3 adds a data bit field 53 to the normal control signal configuration. It is possible to transmit to the microphone 2.

  Also in FIG. 17, the original slave unit reception slot 61 is used as a slave unit transmission slot 60, and the slots S16 and S4 are microphone transmission slots. In the DECT system, a control signal is transmitted from the parent device 3 to the microphone 2 at a rate of once per frame period (10 ms). In FIG. 17, the control signal is transmitted from the original slave device receiving slot 61 to the microphone in the slot S11. 2 is received. When the base unit 3 detects a transmission error for the compressed signal transmitted from the microphone 2, the base unit 3 expands the control signal field as shown in FIG. 16C and writes the error information in the added data bit field 53. An error occurrence is notified to the microphone 2. As a result, even if there is no empty control bit field 51 (see FIG. 16) of the control signal transmitted in the control slot, the base unit 3 notifies the microphone 2 of the occurrence of a transmission error or a new slot number to be used. It becomes possible to do. Alternatively, error information or the like may be written in the control bit field 51 instead of the identification code to notify the microphone 2 of the occurrence of the error.

  That is, base unit 3 sets a control slot that maintains synchronization with microphone 2 for each frame period, and uses a part of the control slot as an error notification slot for notifying at least error information. As a result, the base unit 3 can notify the microphone 2 of the occurrence of an error without providing an independent error notification slot.

  In the DECT method, a plurality of frames can be combined to form a multiframe. The multiframe period is 160 ms, and the control signal including the error information described above may be transmitted once in each multiframe period. As a result, normally, when a transmission error occurs while transmitting and receiving the identification code between the microphone 2 and the base unit 3 to ensure the pairing of both, the microphone 2 can be notified of the occurrence of the error. it can.

  FIG. 18 is an explanatory diagram illustrating the relationship between the synchronization timing and the timing to start the compression process when the transmission / reception slot is changed in the wireless microphone system 1 according to the third embodiment. FIG. 18 shows a process of changing a slot by the above-described processing of ST1406 when the radio wave condition deteriorates. In FIG. 18, the number of channels = 6 (the number of slots = 12) is set to simplify the description.

  As described above, in the DECT method, the number of channels can be changed. Here, slot S0 to slot S5 are set as slave unit transmission slots 60, and slot S6 to slot S11 are set as slave unit reception slots 61. Of the slave unit reception slots 61, the slot S10 is used as an error notification slot for performing error notification from the master unit 3 to the microphone 2. As described above, the control signal to which the data bit field 53 (see FIG. 16) is added may be transmitted using the slot S10 as a control slot.

  Initially, transmission of the compressed signal from the microphone 2 to the parent device 3 is performed using a slot S4 (microphone transmission slot) starting from the synchronization timings TS1 and TS2. The compression processing start timings TC1 and TC2 are set so that the compression processing is completed before the synchronization timings TS1 and TS2. Master device 3 detects a transmission error of the compressed signal transmitted from microphone 2, and in FIG. 18, error notification is sent from master device 3 to microphone 2 in an error notification slot (slot S10) starting from timing TSX. Has been done. In the error notification, the generation timing of the transmission / reception slot newly designated by the base unit 3 is added. Here, the microphone 2 instructs the base unit 3 to change the microphone transmission slot from the slot S4 to the slot S2 (slot change command). ) Has been made.

  The microphone sound processing unit 18 (see FIG. 3) sets NTS3 that is the start of the slot S2 as a new synchronization timing in accordance with the slot change command, and the compression processing unit 18c (see FIG. 3) based on the synchronization timing NTS3. The compression processing start timing NTC1 is determined, and the start periods NTVG1, NTVG2,. The compressed signal is transmitted to the parent device 3 in the microphone transmission slot (slot S2) starting from NTS3, which is a new synchronization timing (that is, reestablished synchronization timing), and the parent device 3 starts from timing NTE1. Start the decompression process. As a result, even if the slot used for transmission / reception when a transmission error occurs (that is, the synchronization timing) is changed, the compression processing start timing is dynamically changed, and the delay time can always be shortened.

  Here, since the base unit control unit 20 (see FIG. 6) detects that there is a transmission error in the compressed signal received at the synchronization timing TS1, it is decompressed immediately after receiving this and detecting the transmission error. After the processing start timing TE1, the audio reproduction can be stopped (or attenuated) by controlling the master audio processing unit 28. In this mute period, after establishing resynchronization, the start NTVG1 of the audio compression frame is determined based on the new synchronization timing NTS3, and the base unit audio processing unit 28 completes the expansion process starting from the timing NTE2. (Second mute period). That is, when the base unit control unit 20 detects that the compressed signal received from the microphone 2 includes a transmission error, the base unit audio processing unit 28 generates a digital audio signal based on the reestablished synchronization timing. During this period, the reproduction of the audio signal is stopped. As a result, when a transmission error occurs, it is possible to prevent abnormal noise from being generated from the speaker 29 (see FIGS. 1 and 5) connected to or incorporated in the parent device 3.

  Since the transmission error transmitted to the microphone 2 in the error notification slot starting from the timing TSX is based on the transmission error detected by the parent device 3 in the microphone transmission slot (slot S4) starting from the synchronization timing TS1, TVG1 The audio signal captured in the audio compression frames of TVG2 to TVG3 has a high possibility of causing a transmission error even if it is transmitted to the parent device 3. Accordingly, the microphone sound processing unit 18 (see FIG. 3) may generate a mute signal by executing a mute process at the compression process start timing TC2. Here, the mute signal may be generated by performing a compression process using the digital audio signal captured in the audio compression frames of TVG1 to TVG2 to TVG3 as NULL data, and is previously stored in the memory 17 (see FIG. 3). A data area may be provided and generated by switching the DMA (Direct Memory Access) source address when data is transferred to the compression processing unit 18c (see FIG. 3).

  Thus, a mute signal is transmitted to the parent device 3 in the microphone transmission slot (slot S4) starting from the synchronization timing TS2. Receiving this, the base unit 3 executes the decompression process at the decompression process start timing TE2. Since the expanded digital audio signal is silent, the audio reproduction from the speaker 29 (see FIG. 6) of the main unit 3 is stopped (muted). This mute period (first mute period) is continued until the extension process starting from the timing NTE2 is completed in the parent audio processing unit 28, as in the second mute period described above. Of course, as described above, since the second mute period is provided in the parent device control unit 20, the mute audio processing unit 18 may not generate a mute signal.

  As described above, the wireless microphone system 1 according to the present invention has been described in detail based on specific embodiments. However, these embodiments are merely examples, and the present invention is not limited to these embodiments. For example, in each embodiment, the wireless microphone system 1 using the DECT method has been described. However, the present invention can be applied not only to the DECT method but also to, for example, a PHS (Personal Handy-phone System) and an spHS (Super PHS). In each embodiment, the microphone 2 and the parent device 3 are described in a one-to-one correspondence. However, a plurality of microphones 2 may be used. The wireless microphone system 1 according to the present invention transmits an audio signal in one direction from the microphone 2 to the parent device 3, but both the audio signal is transmitted from the parent device 3 to the microphone 2. You may comprise the wireless microphone system 1 (what is called an intercom system) which transmits / receives in the direction. The present invention can also be applied to a cordless telephone system. Note that all the components shown in the above-described embodiments are not necessarily essential, and can be appropriately selected as long as they do not depart from the scope of the present invention.

  The wireless microphone system according to the present invention has a delay time from when a user inputs sound to the microphone to when the sound starts to be played back by the parent device when transmitting the audio signal from the microphone to the parent device. Since it can be shortened, it can be suitably used in a wireless microphone system that sets a synchronization timing such as DECT, PHS, and sPHS and transmits / receives an audio signal, a cordless telephone system, and the like.

1 Wireless microphone system 2 Microphone (slave unit)
3 Master unit 10 Microphone control unit 11 Microphone radio unit (radio unit)
11a Frame processing unit 11d Synchronization control unit 17 Memory 18 Microphone audio processing unit (audio processing unit)
18c Compression processing unit 20 Base unit control unit 21 Base unit radio unit 27 Memory 28 Base unit voice processing unit 28a Decompression processing unit 50 Synchronization field 51 Control bit field 53 Data bit field 60 Slave unit transmission slot 61 Slave unit reception slot

Claims (12)

A wireless microphone system comprising a base unit and a microphone that transmits and receives radio waves via a wireless line based on a synchronization timing of a predetermined period established between the base unit,
The base unit and the microphone perform transmission / reception of data by time division multiple access, and a frame period of the time division multiple access includes a plurality of transmission slots. Includes a dynamically determined first microphone transmission slot that transmits a compressed signal to the base unit,
The synchronization timing is the beginning of the first microphone transmission slot;
The microphone is
An audio processing unit that compresses an audio signal acquired every audio capturing period set to a period equal to the predetermined period and generates the compressed signal;
A wireless unit that periodically transmits the compressed signal to the base unit based on the synchronization timing;
The audio processing unit determines a timing for starting the compression processing based on the synchronization timing.   The wireless microphone system according to claim 1, wherein the voice processing unit determines a start time of the voice capturing period based on the synchronization timing. Pre Symbol audio processing unit during the transmission slot immediately before the first microphone transmission slot, claim 1, characterized in that to determine the timing for starting the compression process so that the compression process is completed or The wireless microphone system according to claim 2.   The wireless sound system according to claim 3, wherein the sound processing unit starts the compression processing before the end of the sound capturing period. The frame period of the time division multiple access includes a slave unit reception slot that configures one channel with the first microphone transmission slot and transmits data from the master unit to the microphone,
The master unit is the frame period of the time division multiple-based connection, the slave machine receives a slot, and change from the microphone to the second microphone transmission slot for transmitting the compressed signal to the base unit,
The wireless microphone system according to claim 3 or 4, wherein the microphone transmits the compressed signal using the first microphone transmission slot and the second microphone transmission slot.   The base unit further sets a third microphone transmission slot at an intermediate timing between the first microphone transmission slot and the second microphone transmission slot in the frame period. Wireless microphone system.   7. The wireless microphone system according to claim 5, wherein the base unit sets an error notification slot for notifying at least error information from the base unit to the microphone during the frame period.   The base unit sets a control slot for maintaining synchronization with the microphone every frame period, and uses a part of the control slot as an error notification slot for notifying at least error information. The wireless microphone according to claim 5 or 6.   The wireless microphone system according to claim 8, wherein the base unit further transmits a data bit field in the error notification slot.   The wireless microphone according to any one of claims 7 to 9, wherein the base unit transmits the error notification slot once in a multi-frame period including a plurality of the frame periods. system. The parent device includes a parent device control unit that detects whether or not a transmission error is included in the compressed signal received from the microphone,
When detecting that the compressed signal includes a transmission error, the base unit control unit re-establishes the synchronization timing with the microphone ,
The wireless unit periodically transmits the compressed signal to the base unit based on the synchronization timing reestablished with the base unit,
5. The wireless microphone system according to claim 1, wherein the audio processing unit determines a timing to start the compression processing based on the reestablished synchronization timing. 6. . The base unit further includes a base unit voice processing unit that generates a voice signal by decompressing the compressed signal received from the microphone,
When the base unit control unit detects that the compressed signal received from the microphone includes a transmission error, the base unit audio processing unit generates the audio signal based on the reestablished synchronization timing. The wireless microphone system according to claim 11, wherein the reproduction of the audio signal is stopped for a period of time until the start.

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