Through the above wireless multi-channel audio transmission method, each subset channel audio receiving device can receive one group of subset channel audio data from the wireless multi-channel audio transmission device. The communication process has characteristics of wide transmission bandwidth, low transmission delay and strong transmission reliability.

FIG. 4 is a schematic block diagram of a wireless multi-channel audio transmission device 40 according to one embodiment of the present invention. Referring to FIG. 4, the wireless multi-channel audio transmission device 40 is configured for transmitting N channels of audio data to M subset channel audio receiving devices. The wireless multi-channel audio transmission device 40 comprises an audio processing and storage unit 41, a baseband and protocol processing unit 42 and M transmission modules.

The audio processing and storage unit 41 is configured to divide the N channels of audio data into M groups of subset channel audio data. Each group of subset channel audio data comprises at least one channel of audio data. The baseband and protocol processing unit 42 is configured to transmit the M groups of subset channel audio data to the M subset channel audio receiving devices in parallel through the M transmission modules. Each of the transmission modules adopts a different transmitting frequency at the same time.

The baseband and protocol processing unit 42 is further configured to change the transmission modules used for transmitting each group of subset channel audio data according to a preset changing rule. Each transmission module comprises a radio frequency (RF) unit and an antenna. In one embodiment, each transmission module in FIG. 4 comprises a BLE radio frequency (RF) unit and an antenna connected with corresponding BLE RF unit.

In one embodiment, the audio processing and storage unit 41 is further configured to group the N channels of audio data into the M groups of subset channel audio data according to channel information of the audio data received by each subset channel audio receiving device, wherein one subset channel audio receiving device receives one group of subset channel audio data correspondingly.

In one embodiment, the preset changing rule comprises: each group of subset channel audio data is transmitted through the M transmission modules alternately.

In another embodiment, the preset changing rule comprises: when each group of subset channel audio data is repeatedly transmitted within one transmission time period, different transmission modules are used for transmission at least one time. When one group of subset channel audio data comprises at least two channels of audio data, the transmission module transmits the at least two channels of audio data serially in time division multiplexing mode. When the wireless multi-channel audio transmission method is used in the BLE audio communication, the baseband and protocol processing unit 42 is further configured to establish a group of connected isochronous stream CIS links with each subset channel audio receiving device respectively to transmit one group of subset channel audio data, wherein the group of CIS links comprises at least one CIS link and one CIS link is configured to transmit one channel of audio data; or establish a group of broadcast isochronous stream BIS links with each subset channel audio receiving device respectively to transmit one group of subset channel audio data, wherein the group of BIS links comprises at least one BIS, and one BIS link is configured to transmit one channel of audio data.

In one embodiment, the audio processing and storage unit 41 is configured to encode the N channels of audio data according to a Bluetooth low power communication protocol to generate N channels of mono audio data or audio service data units. The baseband and protocol processing unit 42 is configured to package the N channels of mono audio data or audio service data units into N channels of protocol data units respectively according to a CIS protocol or a BIS protocol, and group the N channels of protocol data units into the M groups of subset channel audio data according to channel information of the audio data received by each subset channel audio receiving device.

The M groups of subset channel audio data are respectively transmitted to corresponding subset channel audio receiving device through the M transmission modules in parallel. The audio processing and storage unit 41 may also be configured to collect and store multi-channel audio data and perform relevant audio processing. The baseband and protocol processing unit 42 is configured to transmit the M groups of subset channel audio data to the M BLE RF units. For one channel of protocol data units transmitted through the CIS link or the BIS link with a sequence number X, the BLE RF unit and the antenna with a sequence number R is used in a subevent with a sequence number S of an isochronous channel event with a sequence number E, wherein R=(X+E+S) mod M, R, X, E and S are all natural numbers. The BLE radio frequency unit modulates the input PDU into a radio frequency signal and sends the radio frequency signal to corresponding subset channel audio receiving device through the connected antenna.

FIG. 2 is a schematic diagram of a wireless multi-channel audio transmission system according to one embodiment of the present invention. Referring to FIG. 2, the wireless multi-channel audio transmission system comprises a wireless multi-channel audio transmission device and M subset channel audio receiving devices. The wireless multi-channel audio transmission device is configured to divide the N channels of audio data into M groups of subset channel audio data; and transmit the M groups of subset channel audio data to the M subset channel audio receiving devices in parallel according to the wireless multi-channel audio transmission method 100 shown in FIG. 3.

The M subset channel audio receiving devices are configured to receive the M groups of subset channel audio data from the wireless multichannel audio transmission device according to the wireless multi-channel audio transmission method 300 shown in FIG. 3. The subset channel audio receiving device m receives K_mchannels of audio data, (N>K_m≥1). That is, each subset channel audio receiving device receives at least one channel of audio data. The sum of the channels of all the subset channel audio receiving devices is equal to N, namely Σ_m=1^MK_m=N.

In one embodiment, each subset channel audio receiving device comprises at least one mono audio receiving device, and/or at least one multi-channel audio receiving device. Specifically, each subset channel audio receiving device may comprise at least one mono channel audio receiving device, may also comprise one multi-channel audio receiving device, and may also comprise a plurality of mono audio receiving devices and/or a plurality of multi-channel audio receiving devices.

Other technical details and working principles of the wireless multi-channel audio transmission system provided according to one embodiment of the present invention may be implemented with reference to the foregoing embodiments, which s are not described herein again. A working principle of the wireless multi-channel audio transmission method and system will be described by taking the BLE audio two-channel TWS (true wireless stereo) earphone pair as an example of the subset channel audio receiving device. In this example, when the TWS earphone pair is used as the subset channel audio receiving device, the wireless multi-channel audio transmission device can be a smart phone, a smart TV, a smart speaker or other audio transmission devices.

The TWS earphone pair comprises two subset channel audio receiving devices. Each subset channel audio receiving device is a mono audio receiving device, and corresponds to a left channel earphone or a right channel earphone. Each subset channel audio receiving device receives one channel corresponding to the left channel or the right channel. A CIS link or BIS link is established between the wireless multi-channel audio transmission device and one of the left and right channel earphones of the TWS earphone pair. Each CIS link or BIS link uses a different channel to ensure that the two CIS links or BIS links do not interfere with each other. An existing BLE channel selection algorithm of time-division multiplexing can be used to determine the channels of the CIS links or the BIS links to ensure sufficient frequency isolation.

Referring to FIG. 4, when M=2, the wireless multi-channel audio transmission device 40 comprises two BLE radio frequency units and two antennas. The CIS or BIS link is established between the wireless multi-channel audio transmission device and one of the left channel earphone and the right channel earphone of the TWS earphone pair. The audio processing and storage unit 41 of the wireless multi-channel audio transmission device 40 collects, processes and saves the two-channel audio data, and adopts a low-complexity communication codec (LC3) according to the BLE Audio communication protocol to encode the two-channel audio data into two channels of mono audio data or audio service data packets (SDU), respectively. The baseband and protocol processing storage unit 42 saves and executes the BLE communication protocol, CIG or BIG protocol, and encapsulates the two channels of mono audio data or audio service data packets (SDU) into protocol data units (PDU) according to the CIS or BIS protocol, and transmits them to two different BLE RF units in parallel. The BLE radio frequency units modulate the corresponding PDUs into radio frequency signal and send it to the left channel earphone and the right channel earphone of the TWS earphone pair through corresponding antennas.

FIG. 5A is a schematic diagram of a CIG time slot structure of the wireless multi-channel audio system. FIG. 5b is a schematic diagram of a BIG time slot structure of the wireless multi-channel audio system. As shown in FIGS. 5a and 5b, it is the CIG or BIG time slot structure between the BLE Audio transmission device and the TWS earphone pair. The CIG established between the BLE Audio transmission device and the TWS earphone pair in FIG. 5a comprises two CIS links, i.e. CIS0 and CIS1. The BIG established between the BLE Audio transmission device and the TWS earphone pair in FIG. 5b comprises two BIS links, i.e. BIS0 and BIS1. In one isochronous interval, each CIS link or each BIS link contains 4 subevents, i.e. subevent 0, subevent 1, subevent 2 and subevent 3. The subevents of the CIS0 link and the CIS1 link are performed alternately in a time-division multiplexing manner. The subevents of the BIS0 link and the BIS1 link are performed alternately in a time-division multiplexing manner.

FIG. 6a is a schematic diagram of a CIG time slot structure of the wireless multi-channel audio system according to one embodiment of the present invention. FIG. 6b is a schematic diagram of a BIG time slot structure of the wireless multi-channel audio system according to another embodiment of the present invention. FIGS. 6a and 6b shows the CIG time slot structure and the BIG time slot structure between the wireless multi-channel audio transmission device and the TWS earphone pair respectively. The wireless multi-channel audio transmission device is connected with the TWS earphone pair through the CIG or the BIG. The CIG in FIG. 6a comprises two CIS links, i.e. CIS0 and CIS1. The BIG in FIG. 6b comprises two BIS links, i.e. BIS0 and BIS1. In one equal time interval, each CIS link or each BIS link comprises 4 subevents, i.e. subevent 0, subevent 1, subevent 2 and subevent 3. The subevents of the CIS0 link and the CIS1 link are performed in parallel and alternately through two different channels, two different BLE RF units and two different antennas. The subevents of the BIS0 link and the BIS1 link are performed in parallel and alternately through two different channels, two different BLE RF units and two different antennas.

As shown in FIGS. 6a and 6b, a subevent 0 of an event 0 of the CIS0 link is performed by the BLE RF unit 0 and the antenna 0, a subevent 0 of an event 0 of the CIS1 link is performed by the BLE RF unit 1 and the antenna 1, a subevent 1 of the event 0 of the CIS0 link is performed by the BLE RF unit 1 and the antenna 1, and a subevent 1 of the event 0 of the CIS0 link is performed by the BLE RF unit 0 and the antenna 0. Compared with a time division multiplexing method shown in FIGS. 5a and 5b, the method shown in FIGS. 6a and 6b can improve the reliability of wireless transmission through the spatial diversity obtained by two antennas, and reduce the transmission delay by half through frequency division multiplexing, or, perform more subevents, that is, more retransmissions, in more times within one isochronous interval, thereby improving wireless transmission performance or wireless transmission reliability. For example, a wireless multi-channel 5.1 surround sound audio system is used as an example to describe the working principle of the wireless multi-channel audio system. The wireless multi-channel audio transmission device of the wireless multi-channel audio system is a smart TV or smart main speaker, and the subset channel audio receiving devices of the wireless multi-channel audio system are BLE Audio wireless speakers.

In the wireless multi-channel 5.1 surround sound audio system, there are 6-channel speakers in total. A center speaker (Center) and a subwoofer are usually smart TVs or smart main speakers, and the other 4-channel speakers are BLE audio wireless speakers, including a front left speaker, a front right speaker, a left surround speaker and a right surround speaker. If the existing time-division multiplexing BLE Audio technology is used, a CIG including four CIS links needs to be established between the smart TV or smart main speaker and the BLE Audio wireless speakers. LC3 encoding is adopted for audio. An encoding rate of each channel is 96 kbps, an encoding frame length is 10 ms, a size of an audio service data unit SDU is 120 bytes, and the isochronous interval is 10 ms. Using BLE 2 Mbps transmission rate, an air time occupied by an encrypted audio protocol data unit (PDU) is 540 us, an Inter Frame Space (T_IFS) is 150 us, an air time occupied by an acknowledgment packet (ACK) is 44 us, and a Minimum Subevent Space (T_MSS) is 150 us. Therefore, the time occupied by each subevent is 884 us (540+150+44+150). In order to ensure the basic reliability of wireless transmission, each CIS link needs to contain at least three sub-events. Then, 4 CIS links require a total of 12 sub-events, that is, 10.608 ms, which exceeds the maximum time that the isochronous interval (10 ms) can provide. Therefore, the existing time-division multiplexing BLE Audio technology cannot solve the above-mentioned requirements of the wireless multi-channel 5.1 surround sound audio system.