Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H1/00—Details of electrophonic musical instruments
  • G10H1/0033—Recording/reproducing or transmission of music for electrophonic musical instruments
  • G10H1/0041—Recording/reproducing or transmission of music for electrophonic musical instruments in coded form
  • G10H1/0058—Transmission between separate instruments or between individual components of a musical system
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R27/00—Public address systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2227/00—Details of public address [PA] systems covered by H04R27/00 but not provided for in any of its subgroups
  • H04R2227/003—Digital PA systems using, e.g. LAN or internet
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2420/00—Details of connection covered by H04R, not provided for in its groups
  • H04R2420/03—Connection circuits to selectively connect loudspeakers or headphones to amplifiers

Definitions

• Audio data transmission system between a master module and slave modules, via a digital communication network
• the invention relates to a system comprising a digital communication network for the transmission of data, comprising audio type data, between a master module and a plurality of slave modules, each module comprising at least one network terminal for connecting the communication network. to the module, at least one network terminal of a slave module being connected to a network terminal of another module via the communication network.
• WO-A-0065571 discloses an audio communication system for transmitting digital audio data between a plurality of audio devices, via a digital communication network to
• This document relates more particularly to a system comprising at least one musical instrument and various electronic components intended for controlling and reproducing the sounds generated by this instrument, for example in the context of a live broadcast.
• the system described in this document does not allow the use of an existing network whatever its architecture. Indeed, it implies a daisy chain connection of the various audio devices which constitute it.
• each of the devices must include a specific interface for communication with the network, which prohibits the use of an existing network comprising, for example, elements standard switching equipment without such an interface.
• the system described is, moreover, expensive and requires significant resources.
• the object of the invention is to provide a system for transmitting audio data which does not have the drawbacks of known systems.
• Such a system must, in particular, make it possible to use an existing communication network, whatever its architecture, to transmit data in a perfectly synchronous manner, with very low transmission latency.
• the master module comprises a synchronization clock and provides on its network terminal data frames comprising synchronization information, each slave module comprising clock reconstruction means, at starting from the synchronization information of the data frames received on its network terminal, and from the recognition means, synchronized by the associated clock reconstruction means, to recognize the data intended for said audit slave module, so as to ensure synchronous data transmission in the system.
• a data frame comprises at least one packet, each packet comprising a header with a descriptor of the type and number of data contained in the packet, a module comprising means for determining, from of the descriptor, if part of the package is intended for it.
• a slave module comprises means for introducing into a predetermined part of a packet data to be retransmitted on the network.
• a data frame can include control data, intended for a slave module comprising means for applying control data to an input or an output of the slave module.
• the communication network comprises modules connected in chain and / or in star.
• Figures 1 to 3 illustrate three alternative configurations of a system according to the invention.
• FIG. 4 schematically illustrates a particular embodiment of a slave module of a system according to FIGS. 1 to 3.
• Figures 5 and 6 respectively illustrate in more detail, in the form of a functional block diagram, a particular embodiment of a master module ( Figure 5) and a slave module ( Figure 6).
• FIG. 7 illustrates an alternative embodiment of a slave module according to FIG. 6.
• Figure 8 illustrates the general structure of a frame.
• FIG. 9 shows in more detail the structure of the header of a frame according to FIG. 8.
• FIG. 10 illustrates in more detail the structure of a packet of a frame according to FIG. 8.
• FIG. 11 illustrates in more detail the structure of a packet header of a packet according to FIG. 10.
• FIG. 12 illustrates an alternative embodiment of a clock reconstruction block of a slave module.
• a system according to the invention as shown in FIGS. 1 to 3, comprises a single master module 1 and a plurality of slave modules 2.
• the modules are connected to form an open chain.
• the master module 1 comprises a port constituting a first network terminal B1 connected, by means of a bidirectional communication network, preferably of the Ethernet type, to a port constituting a second network terminal B2 of a first slave module 2a. This comprises another port constituting a first network terminal B1 connected to the second network terminal B2 of a second slave module 2b.
• five slave modules 2a to 2e are connected in series, the first network terminal B1 of one of the slave modules being connected to the second network terminal B2 of the next slave module.
• the first network terminal B1 of the last slave module 2e is not connected to the communication network, while the second terminal B2 of the first slave module 2a of the chain is connected to the first network terminal B1 of the master module 1.
• the modules are connected in a star. All the second network terminals B2 of the slave modules 2 are connected, via the communication network, to the first network terminal B1 of the master module 1.
• six slave modules are distributed in two groups.
• the second network terminals B2 of a first group of three slave modules 2f, 2g and 2h, are respectively connected to three individual terminals of a switching element 3a. This comprises a common terminal which can be connected to each of its individual terminals and, via the communication network, to the first network terminal of the master module 1.
• the second network terminals of a second group of slave modules 2i , 2j and 2k are respectively connected to three individual terminals of a switching element 3b, comprising a common terminal connected to a fourth individual terminal of the switching element 3a. None of the first network terminals B1 of the slave modules is connected to the communication network.
• the configuration of the system illustrated in FIG. 3 is more complex and comprises both modules connected in chain and modules connected in star.
• the first network terminal B1 of the master module is connected to the common terminal of a switching element 3c. This comprises four individual terminals, respectively connected to the second network terminals of three slave modules 21, 2m and 2n, and to the common terminal of a switching element 3d.
• the slave module 21 is connected in series with two other slave modules 2o and 2p.
• the switching element 3d has three terminals individual, respectively connected to the second network terminals of three slave modules 2q, 2r and 2s.
• the slave module 2s is connected in star with three slave modules 2t, 2u and 2v, via a switching element 3e.
• the latter comprises a common terminal, connected to the first terminal B1 of the slave module 2s and three individual terminals connected respectively to the second terminals B2 of the slave modules 2t, 2u and 2v.
• the first terminals B1 of the slave modules 2m, 2n, 2p, 2q, 2 r, 2t, 2u and 2v are not connected to the communication network.
• the switching elements 3 are standard elements conventionally used in known networks, for example in networks of the Ethernet type, for making star connections.
• each slave module 2 comprises an analog audio output terminal Ba, connected to the input of a loudspeaker 4.
• certain modules (1 and 2b in FIG. 1 , 2k in Figure 2 and 2v in Figure 3) have an audio input terminal, analog or digital, connected to the output of a microphone 19.
• a slave module 2 shown diagrammatically in FIG. 4, comprises a processing circuit 5, for example with a microprocessor, connected by bidirectional links to the first and second network terminals B1 and B2 to allow its connection to the communication network.
• the processing circuit 5 is also connected, via a digital-analog converter, to the analog audio output terminal Ba of the module. he can also be connected to an analog audio input terminal via an analog-digital converter (not shown).
• Figures 5 and 6 show in more detail the functions performed respectively by the processing circuit of a master module 1 and by the processing circuit of a slave module 6.
• the signals in from a network terminal B are applied, via a first physical layer 7 to a block 8 for detecting the start of a frame, which supplies the appropriate signals to a block 9 for decomposing the frame.
• the latter is connected, via an audio output interface 10, to a digital audio output terminal B3.
• a digital audio input terminal B4 (to which a digital microphone 19 can be connected, for example) is connected, via an audio input interface 11, to a composition block of the frame 12.
• This provides signals representative of the frame to be transmitted to the network terminal B, via a block 13 for producing the start of the frame and a second physical layer 14.
• a clock 15 synchronizes the operation of the blocks 8 to 13 of the module and allows the composition block of the frame 12 to introduce synchronization ticks in each frame.
• the different blocks of the module can be formed in any known manner and will not be described in more detail.
• the master module 1 also includes a command processing module 33, connected between the frame decomposition block 9 and the audio interfaces 10 and 11.
• the master module 1 can thus apply control data, corresponding to simple control functions (amplitude, etc.) at one of its inputs or outputs.
• the slave module 2 represented in FIG. 6, differs from the master module 1 in FIG. 5 only by the absence of the clock 15. This is replaced by a block clock reconstruction 16 which reconstructs a clock from the synchronization information contained in the frames and detected by the frame start detection block 8.
• the frame descriptor 32 and the specific type 26, described below respectively in conjunction with FIGS. 8 and 9, must conform to a predetermined model.
• the processing circuit thus essentially has the function of synchronization, reception of frames applied to its network terminals, recognition of the data that it must transmit to its outputs, in particular to its digital audio B3 or analog Ba outputs, or that it must recover for writing in internal variables, the introduction, in frames to be transmitted over the network, of data present on its digital inputs (for example on a digital audio input B4) or of internal variables (for example in response to a read variable command).
• a slave module 2 has two network terminals B1 and B2.
• the first and second physical layers 7 and 14 are then associated with the second network terminal B2.
• Third and fourth physical layers 17 and 18, associated with the first network terminal B1 are then respectively connected to the first and to the second physical layers.
• a frame from the second network terminal B2 can be transmitted without modification to the first network terminal B1, via the physical layers 7 and 17.
• a frame from the first network terminal B1 can be transmitted without modification to the second network terminal B2, via physical layers 18 and 14
• the analog audio terminal Ba is not shown in FIGS. 5 to 7, such a terminal is preferably provided in each module, the digital-analog converter 6 being connected to the output of the digital audio output interface 10.
• An analog audio terminal can be connected by an analog-digital converter to the input of the digital audio interface input 11.
• the terminals digital audio B3 and B4, not shown in Figure 4 are also preferably provided in each module.
• the digital audio input terminal B4 makes it possible in particular, for example from a microphone 19, to supply a module with digital audio data to be transmitted in data frames over the network.
• the digital audio output terminal B3 allows a module to transmit to any digital audio equipment, which is connected to it, digital data, which is intended for it, contained in the data frames coming from the network.
• all the modules are identical, the same module being able to be configured as a master module or as a slave module.
• each system still comprises only one master module, so as to ensure synchronization, from the synchronization information transmitted in the data frames, of all the modules on the clock of the master module.
• Each module, master or slave, is associated with a unique address and a data frame comprises a preamble, a destination address, a source address, and the data to be transmitted from the module corresponding to the source address to the module corresponding to the destination address.
• the frames used conform to the frame format compatible with an Ethernet type network, so as to allow the modules to be connected by any Ethernet network in double access (“full duplex").
• the number of usable channels depends on the network bandwidth.
• the master module 1 sends data frames to the network intended either for a predetermined slave module 2 or for a group of slave modules, or for all of the slave modules. In the latter two cases, the master module 1 supplies as destination address either a group transmission address (“multicast”) or a general transmission address (“broadcast”) for transmitting data simultaneously to a group of slave modules or, respectively, to all slave modules 2.
• multicast group transmission address
• Broadcast general transmission address
• FIG. 8 The general structure of a frame is illustrated in FIG. 8. It first comprises a header 20, of the Ethernet type in the embodiment shown.
• the header 20 is followed by a frame descriptor 32, which provides a subtype, a version number, the number of packets, the length of the packets, information on the frequency of the master module and an incremental number of frame.
• the frame descriptor 32 is followed by at least one packet 21 (packet 1, packet 2, etc.) and the frame ends with a frame check sequence 22. This check can be carried out by any known means compatible with the Ethernet specifications, for example by a cyclic redundancy check.
• Each module is associated with a unique address and, as shown in FIG. 9, the header 20 of each frame includes a preamble 23, a destination address 24 and a source address 25. It also includes a specific type 26, specific to the application.
• the specific type preferably uses predetermined fields of a standard Ethernet type header, such as the length or type field ("LTF: Length or Type Field”), the type subfield ("STF : Sub Type Field ”) and the field associated with the protocol version number (" PVNF: Protocol Version Number Field ”) to define the type of protocol used.
• the specific type 26 also specifies the frequency of the clock 15 of the master module, the number of packets 21 of the frame and the number of bytes of the frame. The number of packets 21 is preferably between 1 and 32, the number of bytes, compatible with an Ethernet network, being between 46 and 1500.
• the specific type 26 also includes a clock increment field (“MCIN : Master
• Each slave module includes, for this purpose, a counter which is incremented each time a frame is lost, that is to say when the clock incrementation field of the received frame does not include the incremented value of clock increment field of the previous frame.
• each packet 21 comprises a packet header, containing the description of the package considered, and a set of subpackets 28 (subpacket 1, subpacket 2, etc.), containing the data to be transmitted.
• the packet header 27 identifies the packet under consideration and describes the number and type of information contained in the packet. It provides a description of the data contained in the package, their characteristics and their distribution in the package. It comprises (FIG. 11) in particular a field 29, for example with 2 bits, defining the type of data contained in the packet.
• Each packet is in fact preferably dedicated to a type of data: control data, audio data, video data, any digital data.
• each frame comprises two packets, one comprising control data and the other comprising audio data.
• control data can, for example, relate to the amplitude of emission of sounds by a loudspeaker 4 connected to the slave module 2 for which they are intended. They are then transmitted by the circuit 5 of this slave module 2 to its audio output to control the speaker 4 accordingly.
• the packet header 27 also includes an identifier field 30 and a descriptor field 31.
• the identifier field defines to which module and to which input or output of a slave module, that is to say to which equipment (for example which loudspeaker 4 or which microphone 19) are used for the control data of each subpacket. It can also define the transmission frequency, different transmission frequencies can be used for the different packets.
• the descriptor field 31 specifies in particular the order of the words in the sub-packets (first word of the sub-packet first or last word of the sub-packet first), the size of the words (at least one byte)., the order of the bits in the word, the number of sub-packets and the number of words per sub-packet.
• an audio data packet can comprise 3 sub-packets of 2 words each, with 24 bits per word.
• Each slave module 2 comprises n registers, respectively associated with n inputs or outputs of the module, as well as descriptor registers defining the state and configuration of the slave module.
• a register associated with an input or an output of a module contains information (type of packet, packet identifier, number of subpacket, etc.) making it possible to identify, in a frame, the data that the module slave must select.
• each module is programmed to use the data located in certain locations of a frame to control and / or send data, audio for example, to equipment connected to a predetermined output of the module.
• a slave module can not only use data contained in a frame which it receives, but also introduce data in a frame which it received and which it retransmits on the network, either bound for another slave module, either to the master module. This is particularly the case a slave module comprising an input connected to a microphone 19 (slave modules 2b in FIG. 1, 2k in FIG. 2 and 2v in FIG. 3).
• the slave module register associated with this entry specifies in which subpacket this data must be entered.
• a slave module 2 adds data to a frame, it consequently modifies the control sequence 22 of the frame. If the modified frame is intended for the master module 1, it also modifies the source address (normally constituted by the address of the master module) to replace it with its own address.
• a slave module receiving, on one of its network terminals, a frame which is not intended for it retransmits it on the network, without modification, via its other network terminal.
• a slave module located at the end of a branch of the network that is to say whose terminal B1 is not connected to the network, can be preprogrammed either so as not to retransmit a frame received on its network terminal B2 , or, if necessary, to retransmit it, by the same network terminal B2, towards the master module or another predetermined slave module.
• the slave module 2e of FIG. 1 can be preprogrammed to send a frame to the master module 1.
• the slave module 2f of FIG. 1 can be preprogrammed to send a frame to the master module 1.
• a second mode it retransmits the frames received towards the master module 1.
• this second mode is used for all end slave modules in the case of a star configuration (modules 2f to 2k in the figure 2), this can create congestion problems on the network during the ascent of all the frames to the master module.
• an end slave module is programmed to send the frames back to another slave module.
• the slave module 2f can be programmed to return the frames to from the 2g slave module, which sends them back to the 2h slave module.
• the frames intended for the slave module 2k thus pass successively from the master module 1 to the switching element 3a, to the slave module 2f, to the switching element 3a, to the slave module 2g, to the switching element 3a, to the module slave 2h, switching element 3a, switching element 3b, slave module 2i, switching element 3b, slave module 2j, switching element 3b and slave module 2k.
• the latter can then send them back to the master module 1 via the switching elements 3b then 3a.
• the switching elements must then be programmed accordingly.
• the switching element 3c (FIG. 3), for example, recognizes the destination addresses in the frames which reach it from the master module 1. If the destination address corresponds to the address of one of the slave modules 21, 2o or 2p, it transmits the frame to the slave module 21. On the other hand, if the destination address corresponds to the address of one of the slave modules 2s, 2t, 2u or 2v, it transmits the frame to the switching element 3d, which transmits it to the slave module 2s.
• the switching element 3c is also programmed to recognize the destination address corresponding to the 2m slave module in the frames, whether these come from the master module 1 or from the slave module 2p (via the slave modules 2o and 21 ). Thus, the 2p slave module can be programmed to send the frames back to the 2m slave module.
• the slave modules can read the data contained in a frame and, possibly, enter data in a predetermined location of the frame, but they cannot in any way case create a new frame.
• the network is a two-way communication network, preferably of the Ethernet type.
• the clock 15 preferably has a frequency corresponding to the sampling frequencies conventionally used on the Ethernet network, namely 32KHz, 44.1 KHz, 48kHz, 88.2KHz or 96KHz. It can also have a frequency corresponding to a submultiple of these frequencies. In this case, several data samples are transmitted in each subpacket. For example, for the transmission of audio data sampled at 48KHz, a clock at 12KHz can be used by transmitting 4 samples per subpacket.
• the clock 15 can also have a frequency which is not a submultiple of the data sampling frequency.
• a clock at 48KHz can be used while transmitting audio data sampled at 44.1KKz, with one or zero samples per subpacket.
• the clock reconstruction block 16 can consist of any suitable circuit. It conventionally includes a phase locked loop (“Phase Lock Loop”, PLL) intended to slave the output Fout frequency of block 16 to the input frequency End of the synchronization tops coming from the data frames applied to block 8 for detection of start of associated frame.
• PLL Phase Lock Loop
• the jitter possibly present in the frequency signals applied to the input of the phase locked loop is found in the output frequency signals of the loop.
• a digital jitter filter 34 is preferably arranged upstream of the phase locked loop 35, as shown in FIG. 12.
• the filter 34 is a recursive digital filter, low pass type, at least first order.
• the frequency signals Fin applied to it are filtered and the filter 34 supplies signals F'in, applied to the input of the phase locked loop 35, in which the jitter is eliminated or, at least reduced.
• the phase-locked loop 35 conventionally comprises a phase comparison circuit 36 in series with a low-pass filter 37 and a voltage-controlled oscillator (VCO) 38.
• the phase comparison circuit 36 has a first input, connected to the output of the digital jitter filter 34, and a second input, connected to the output of the oscillator 38 via a divider 39. It thus receives, as input, the signals F'in and Fout / N, N being a predetermined integer.
• the communication network can also be constituted by a serial link or by a carrier current network.
• the first network terminal B1 of the master module 1 can, in fact, be connected, by the carrier network, to the second terminals network B2 of all slave modules 2: terminal B1 of master module 1 is connected to terminal B2 of a slave module, itself connected to terminal B2 of another slave module, in turn connected to terminal B2 of the following slave module, etc.
• the master module 1 comprises a second network terminal B2, connected to all the first network terminals B1 of the slave modules. In this case, the master module indicates which slave can speak.
• the master and slave modules each have only one network terminal B (FIGS. 5 and 6), the network terminal of the master module being connected by carrier current to the network terminals of all the slave modules. Communication then takes place by time division, under the control of the master module, which indicates to each slave module the time interval reserved for it.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Small-Scale Networks (AREA)

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