Audio system control method and audio system

Abstract

The invention provides an audio system control method and an audio system. The audio system control method comprises the following steps: (a) establishing an OOB wireless communication channel between a first audio playing device and a second audio playing device; (b) when the first audio playing device prepares to play audio data, calculating a first time difference between a current time point and a first expected playing time point; (c) if the current time point is before the first expected playback time point, transmitting a preliminary notification to the second audio playback device over the OOB wireless communication channel; (d) if the second audio playback device has received the preparation notification and is ready to play the audio data, transmitting a play start notification to the first audio playback device through the OOB wireless communication channel; and (e) after the first audio playing device receives the playing starting notification, the first audio playing device and the second audio playing device start to play the audio data.

Description

TECHNICAL FIELD

[0001] The present application relates to an audio system control method and an audio system, in particular, to an audio system control method and an audio system capable of reducing audio playing delay. BACKGROUND

[0002] With the progress of technology, Bluetooth earphones become more and more popular. However, if different Bluetooth earphones in a pair of Bluetooth earphones have different performance, the earphone with higher performance will reduce its audio playing speed in order to synchronize with the earphone with lower performance while complying with Bluetooth protocol. Thus, the pair of Bluetooth earphones will have a larger delay when playing audio.

[0003] For example, BLE Audio introduces the concept of SDU (Service Data Unit) synchronization reference and presentation delay to synchronize the playing time points of different earphones in a BLE Audio network. However, this algorithm will be matched with the weakest device, which may waste the performance of the better earphones in the network. At the same time, this algorithm will configure the earphone parameters when the BLE Audio network is established, and does not support the function of dynamically adjusting the earphone parameters.

[0004] Therefore, a new audio system control method and an audio system are needed to improve this problem. SUMMARY

[0005] The purpose of the present application is to provide an audio system control method to enable different audio playing devices to synchronize in a less restricted manner.

[0006] Another purpose of the present application is to provide an audio system to enable different audio playing devices to synchronize in a less restricted manner.

[0007] Embodiments of the present application disclose an audio system control method, which is used in an audio system including a first audio playing device and a second audio playing device, comprising: (a) establishing an OOB (out of band) wireless communication channel between the first audio playing device and the second audio playing device; (b) calculating a first time difference between a current time point and a first expected playing time point when the first audio playing device receives audio data output by a sound source device and is ready to play the audio data; (c) if the current time point is before the first expected playing time point, the first audio playing device transmits a preparation notification representing that the first audio playing device is in a preparation state to the second audio playing device through the OOB wireless communication channel; (d) if the second audio playing device has received the preparation notification and receives the audio data output by the sound source device and is ready to play the audio data, the second audio playing device transmits a start playing notification to the first audio playing device through the OOB wireless communication channel to inform the first audio playing device that it can start playing; and (e) after the first audio playing device receives the start playing notification, the first audio playing device and the second audio playing device start playing the audio data.

[0008] Another embodiment of the present application discloses an audio system control method, which is used in an audio system including a plurality of audio playing devices, comprising: (a) establishing a wireless communication channel between a sound source device and the plurality of audio playing devices respectively; (b) when the plurality of audio playing devices receive first audio data output by the sound source device and are ready to play the first audio data, the plurality of audio playing devices respectively transmit a preparation notification representing that the plurality of audio playing devices are in a preparation state to the sound source device through the wireless communication channel; and (c) when the sound source device confirms that all the plurality of audio playing devices are in the preparation state, the sound source device generates a control instruction to the plurality of audio playing devices to make the plurality of audio playing devices start playing the first audio data.

[0009] A further embodiment of the present application discloses an audio system, comprising a first audio playback device and a second audio playback device. The first audio playback device establishes an OOB wireless communication channel between the first audio playback device and the second audio playback device. When the first audio playback device receives audio data outputted by an audio source device and is ready to play the audio data, the first audio playback device calculates a first time difference between a current time point and a first expected play time point. If the current time point is before the first expected play time point, the first audio playback device transmits a preparation notification representing that the first audio playback device is in a preparation state to the second audio playback device through the OOB wireless communication channel. If the second audio playback device has received the preparation notification and receives the audio data outputted by the audio source device and is ready to play the audio data, the second audio playback device transmits a start play notification to the first audio playback device through the OOB wireless communication channel to inform the first audio playback device that it can start playing. After the first audio playback device receives the start play notification, the first audio playback device and the second audio playback device start playing the audio data.

[0010] According to the foregoing embodiments, the synchronization of different Bluetooth earphones can not be limited by the presentation delay in the Bluetooth specification, and the problem that the performance of all Bluetooth earphones in the prior art is limited by Bluetooth earphones with lower performance can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A schematic diagram of an audio system control method according to an embodiment of the present application is shown.

[0012] Figure 2 A schematic diagram of a presentation delay is shown.

[0013] Figure 3 A schematic diagram of an audio system control method according to another embodiment of the present application is shown.

[0014] Figure 4A And Figure 4B A schematic diagram of an audio system according to an embodiment of the present application is shown. Figure 1 And Figure 2 A detailed flowchart of the operation of the audio system shown.

[0015] Figure 5 An audio system control method according to an embodiment of the present application is shown.

[0016] Figure 6 A schematic diagram of an audio system control method according to another embodiment of the present application is shown.

[0017] Figure 7 A schematic diagram of an audio system according to an embodiment of the present application is shown. Figure 6The diagram shows a detailed flowchart of how the audio system operates.

[0018] Figure 8 An audio system control method according to another embodiment of the present invention is shown. Detailed Implementation

[0019] The present invention will be described below with reference to several embodiments. It should be noted that the elements in each embodiment can be implemented by hardware (e.g., a device or circuit) or firmware (e.g., at least one program written into a microprocessor). Furthermore, the terms "first," "second," and similar descriptions in the following description are only used to define different elements, parameters, data, signals, or steps, and are not intended to limit their order. For example, the first device and the second device can be devices with the same structure but different from each other.

[0020] Figure 1 A schematic diagram of an audio system control method according to an embodiment of the present invention is shown. Figure 1 As shown, the audio system includes a first audio playback device EP_1 and a second audio playback device EP_2. The first audio playback device EP_1 and the second audio playback device EP_2 can receive audio data from the audio source device M. In this embodiment, the audio source device M is a mobile device (e.g., a mobile phone), and the first audio playback device EP_1 and the second audio playback device EP_2 are Bluetooth headphones. In this embodiment, the audio source device and the audio playback device in this invention use the Bluetooth protocol BLE Audio. However, it should be noted that the audio source device and the audio playback device in this invention can be replaced by other electronic devices and are not limited to mobile devices and wireless headphones, and can comply with other protocols.

[0021] exist Figure 1 In this embodiment, an Out-of-Band (OOB) wireless communication channel CH_O is established between the first audio playback device EP_1 and the second audio playback device EP_2. In this embodiment, the OOB wireless communication channel CH_O is a channel using non-Bluetooth technology, such as the 5G OOB channel in Wi-Fi technology. The advantage of using 5G technology is that moisture does not strongly shield or interfere with 5G. Since the main component of the human body is water, human interference is relatively significant for wireless headphones; using 5G OOB can avoid this interference.

[0022] The first audio playback device EP_1 and the second audio playback device EP_2 also establish a wireless communication channel CH_1, CH_2 with the audio source device M respectively. Since the first audio playback device EP_1 and the second audio playback device EP_2 are Bluetooth earphones, the wireless communication channels CH_1, CH_2 are wireless communication channels complying with the Bluetooth protocol. That is, in embodiments, the wireless communication channels CH_1, CH_2 can use wireless communication channels complying with a first protocol, while the OOB wireless communication channel CH_O can use wireless communication channels complying with a second protocol, the first protocol and the second protocol being different.

[0023] After the OOB wireless communication channel CH_O is established, the first audio playback device EP_1 calculates a first time difference between a current time point and a first expected playback time point when the first audio playback device EP_1 receives the audio data outputted by the audio source device M and is ready to play the audio data. If the current time point is before the first expected playback time point (i.e. it is not yet the time when the audio should be played), the first audio playback device EP_1 transmits a preparation notification representing that the first audio playback device EP_1 is in a preparation state to the second audio playback device EP_2 through the OOB wireless communication channel CH_O. In embodiments, the first audio playback device EP_1 calculates the first expected playback time point according to the current time point and a presentation delay specified in a Basic Audio Profile in the Bluetooth protocol. In this case, the first expected playback time point can also be referred to as a render point.

[0024] Figure 2 A diagram showing the presentation delay is shown. As Figure 2 shown, in the Bluetooth protocol, the first audio playback device EP_1 and the second audio playback device EP_2 are caused to receive the audio data at a same time point, for example at an audio synchronization reference point. The audio data can be in the form of an SDU. Since the first audio playback device EP_1 and the second audio playback device EP_2 decode and perform audio processing (e.g. resampling or equalization) on the audio data after receiving the audio data, a delay time is required between the render point and the audio synchronization reference point. In the Basic Audio Profile, the presentation delay is determined according to the performance of the first audio playback device EP_1 and the second audio playback device EP_2, so that the first audio playback device EP_1 and the second audio playback device EP_2 can process the audio data and the render points are synchronized. As mentioned above, the presentation delay must be adapted to the performance of all audio playback devices, so if at least one of the audio playback devices has a lower performance, the overall presentation delay will also be set to be relatively longer, which will limit the rendering of the audio playback devices with higher performance.

[0025] Please go back to Figure 1 If the second audio playback device EP_2 has received the preparation notification representing that the first audio playback device EP_1 has entered the preparation state, and has received the audio data outputted by the audio source device M and is ready to play the audio data, a start playing notification is transmitted through the OOB wireless communication channel CH_O to notify the first audio playback device EP_1 that it can start playing. After the first audio playback device EP_1 receives the start playing notification, the first audio playback device EP_1 and the second audio playback device EP_2 start playing the audio data. Such a process can be called synchronization of the audio playback devices.

[0026] In an embodiment, the first audio playback device EP_1 starts playing the audio data if it monitors that the first time difference is less than the critical difference while waiting for the start playing notification from the other audio playback device. If the critical difference is zero, it means that the current time point has reached the first expected playing time point, then the first audio playback device EP_1 starts playing the audio data without waiting for the second audio playback device EP_2. In an embodiment, after the first audio playback device EP_1 and the second audio playback device EP_2 start playing the audio data, the first audio playback device EP_1 or the second audio playback device EP_2 keeps calculating the actual playing time point of the audio data and the second expected playing time point, and if the actual playing time point falls behind the second expected playing time point more than the critical number of times, the aforementioned synchronization step is performed again to adjust the time point when the first audio playback device EP_1 and the second audio playback device EP_2 start playing the audio data. In an embodiment, the second expected playing time point is also calculated according to the rendering delay specified in the underlying audio specification.

[0027] Figure 1 The embodiment of the present application is described with two audio playback devices, however, the concept of the present application can also be applied to more than two audio playback devices. Figure 3 A schematic diagram showing a method of controlling an audio system according to another embodiment of the present application is shown. As shown in Figure 3 The audio system further comprises at least one third audio playback device EP_a, EP_b,... EP_x in addition to the first audio playback device EP_1 and the second audio playback device EP_2. The audio playback devices can communicate with each other through the aforementioned OOB wireless communication channel CH_O. Therefore, in Figure 3 In the embodiment of the present application, each audio playback device EP_1 can transmit the preparation notification to other audio devices through the OOB wireless communication channel CH_O (such an action can also be called broadcasting). In an embodiment, the second audio playback device enters the preparation state latest among all the audio playback devices of the audio system. That is, in Figure 3In the embodiment of the present application, the audio playback device that enters the standby state latest informs other audio playback devices to start playing the audio data, and other audio playback devices do not inform other audio playback devices to start playing the audio data.

[0028] Figure 4A and Figure 4B Fig. 1 shows an audio system according to an embodiment of the present application. Figure 1 and Figure 2 Fig. 2 shows a detailed flowchart of the operation of the audio system shown in Fig. 1. Please refer to Fig. 1 together with Fig. 2 to understand the present application. Please note that Figure 4A and Figure 4B Fig. 3 shows another detailed flowchart of the operation of the audio system shown in Fig. 1. Please refer to Fig. 1 together with Fig. 3 to understand the present application. Please note that Figure 4A and Figure 4B Fig. 1 to Fig. 3 are described by taking 5G network and Bluetooth devices as examples, but are not used to limit the scope of the present application.

[0029] Figure 4A and Figure 4B comprises the following steps:

[0030] Step 401

[0031] The audio playback device starts to operate.

[0032] Step 403

[0033] It is determined whether there are other audio playback devices that can use the setting mechanism of the present application. For example, it is determined whether there are other audio playback devices that include ICs (Integrated Circuits) designed to execute the present application.

[0034] If not, the OOB wireless communication channel between the audio playback devices cannot be established, and thus step 407 is reached.

[0035] If yes, step 405 is reached.

[0036] Step 405

[0037] The 5G OOB channel between the audio playback devices is established.

[0038] Step 407

[0039] The presentation point is calculated according to the presentation delay.

[0040] Step 409

[0041] Is the audio data received?

[0042] If yes, the next step 411 is performed, and if not, the step 409 is remained to continue to determine whether the audio data is received.

[0043] As described above, the audio data can be in the SDU format.

[0044] Step 411

[0045] Decode the audio data.

[0046] Step 413

[0047] Process the audio data.

[0048] For example, resample or equalize the audio data.

[0049] Step 415

[0050] Is the current time the show point?

[0051] If not, go to next step 417, if yes, go to step 429.

[0052] Step 417

[0053] Is there a 5G OOB channel?

[0054] If not, go back to step 415, if yes, go to step 419.

[0055] Step 419

[0056] Are other audio playback devices in a ready state?

[0057] If not, go to step 421, if yes, go to step 429.

[0058] Step 421

[0059] Each audio playback device in turn transmits a confirmation notification over the 5G OOB channel.

[0060] Step 423

[0061] Continuously monitor the 5G OOB channel and the show point.

[0062] Step 424

[0063] Notify other audio devices to start playing the audio data.

[0064] Step 425

[0065] Is the current time the show point?

[0066] If not, go back to step 423, if yes, go to step 427.

[0067] Step 427

[0068] Has an audio playback device entered a playing state?

[0069] If yes, go to step 429, if no, go to step 423.

[0070] Step 429

[0071] Each audio playback device is in a playing state.

[0072] Step 431

[0073] Each audio playback device is in a playing state.

[0074] Steps 431 to 439 are steps for the audio playback devices to re-synchronize after the audio playback devices enter the playing state. Step 431 and step 429 can be regarded as the same step.

[0075] Step 433

[0076] Is the actual playing time point behind the performance point (one of the aforementioned second expected playing time points)?

[0077] If no, return to step 433. If yes, go to step 435.

[0078] Step 435

[0079] Count the number of times of falling behind.

[0080] Step 437

[0081] Is the number of times of falling behind greater than a critical number of times?

[0082] If yes, go to step 439. If no, return to step 435.

[0083] Step 439

[0084] Restart the synchronization process and return to step 409.

[0085] According to the aforementioned embodiments, a simplified audio system control method can be obtained, Figure 5 An audio system control method according to an embodiment of the present application is shown, which is used in an audio system (for example, the audio system shown in Figure 1 ). Figure 5 The flowchart shown includes the following steps:

[0086] Step 501

[0087] An OOB wireless communication channel (for example, OOB wireless communication channel CH_O) is established between the first audio playback device and the second audio playback device. This step can be performed by the first audio playback device.

[0088] Step 503

[0089] The first audio playback device calculates a first time difference between a current time point and a first expected playback time point when the first audio playback device receives the audio data outputted by the audio source device and is ready to play the audio data.

[0090] Step 505

[0091] If the current time point is before the first expected playback time point, the first audio playback device transmits a preparation notification representing that the first audio playback device has entered the preparation state to the second audio playback device through the OOB wireless communication channel.

[0092] Step 507

[0093] If the second audio playback device has received the preparation notification and receives the audio data outputted by the audio source device and is ready to play the audio data, the second audio playback device transmits a start playback notification to the first audio playback device through the OOB wireless communication channel to inform the first audio playback device that it can start playing.

[0094] Step 509

[0095] After the first audio playback device receives the start playback notification, the first audio playback device and the second audio playback device start playing the audio data.

[0096] In an embodiment, after the first audio playback device and the second audio playback device start playing the audio data, the first audio playback device or the second audio playback device continuously calculates an actual playback time point of the audio data and a second expected playback time point, and if the actual playback time point falls behind the second expected playback time point for more than a critical number of times, steps 503 to 509 are performed again.

[0097] In an embodiment, the audio system further comprises at least one third audio playback device (e.g. Figure 3 The third audio playback device EP_a, EP_b in the embodiment). In this case, step 507 further transmits the preparation notification to the third audio playback device, wherein the second audio playback device enters the preparation state latest among all the audio playback devices in the audio system.

[0098] In the foregoing embodiments, the OOB wireless communication channel is established among the audio playback devices. However, the synchronization of the audio playback devices can also be performed without the OOB wireless communication channel among the audio playback devices. Figure 6 A schematic diagram showing an audio system control method according to another embodiment of the present application is shown. As Figure 6As shown, the audio system includes a first audio playback device EP_1 and a second audio playback device EP_2. The first audio playback device EP_1 and the second audio playback device EP_2 can receive audio data from a source device M. In an embodiment, the source device M is a mobile device (e.g., a mobile phone), and the first audio playback device EP_1 and the second audio playback device EP_2 are Bluetooth earphones.

[0099] In Figure 6 an embodiment, the first audio playback device EP_1 and the second audio playback device EP_2 do not establish an OOB wireless communication channel CH_O between each other as Figure 1 usual. Instead, the first audio playback device EP_1 and the second audio playback device EP_2 establish wireless communication channels CH_1, CH_2 with the source device M, respectively. In an embodiment, the wireless communication channels CH_1, CH_2 are 5G OOB channels. If the first audio playback device EP_1 and the second audio playback device EP_2 are Bluetooth devices, the wireless communication channels CH_1, CH_2 can also be wireless communication channels conforming to the Bluetooth protocol. Figure 6 In an embodiment, the playback actions of the first audio playback device EP_1 and the second audio playback device EP_2 are controlled by the source device M. In detail, when the first audio playback device EP_1 and the second audio playback device EP_2 receive the first audio data output by the source device M and are ready to play the first audio data, the first audio playback device EP_1 and the second audio playback device EP_2 respectively transmit a ready notification to the source device M through the wireless communication channels CH_1, CH_2. When the source device M confirms that all the audio playback devices are in the ready state, the source device M generates a control instruction to the audio playback devices to start playing the first audio data.

[0100] In an embodiment, the source device M collects a plurality of actual play times at which the first audio playback device EP_1 and the second audio playback device EP_2 actually play the second audio data after the first audio playback device EP_1 and the second audio playback device EP_2 start playing the audio data, and calculates a time difference of the plurality of actual play times. If the largest time difference is greater than a critical difference, the synchronization of the audio playback devices is performed again.

[0101] Figure 7 A detailed flowchart of the operation of the audio system shown in Figure 6 Fig. 1 is shown. Please note that Figure 7 5G networks and Bluetooth devices are used as examples, but are not intended to limit the scope of the present application.

[0102] Figure 7 includes the following steps:

[0103] Step 701

[0104] The sound source device started operating.

[0105] Step 703

[0106] Confirm whether other audio playback devices can use the setting mechanism of this invention. For example, confirm whether other audio playback devices include an IC designed to execute this invention.

[0107] If not, the mechanism of this invention cannot be used between the sound source device and the audio playback device, and therefore execution can be stopped.

[0108] If yes, proceed to step 705.

[0109] Step 705

[0110] Establish a 5G OOB channel between the audio source device and the audio playback device.

[0111] Step 707

[0112] Have all audio playback devices sent a readiness notification?

[0113] If yes, proceed to step 709; otherwise, stay at step 707 and continue waiting.

[0114] Step 709

[0115] The audio source device generates control commands to the audio playback device via the 5G OOB channel, causing the audio playback device to start playing audio data.

[0116] Step 711

[0117] The audio source device collects multiple actual playback times of the second audio data actually played by the audio playback device.

[0118] Step 713

[0119] Is the largest of the time differences greater than the critical difference?

[0120] If yes, proceed to step 715; otherwise, return to step 711.

[0121] Step 715

[0122] Perform synchronization of the audio playback device again.

[0123] according to Figure 6 and Figure 7 An example flowchart of the audio system control method provided by the present invention can be obtained. Figure 8 An embodiment of the present invention is shown. Figure 6 The diagram shown is a summary flowchart of the operation of an audio system, which is used in an audio system that includes multiple audio playback devices (e.g.,Figure 6 the audio system shown. Figure 8 The flowchart shown includes the following steps:

[0124] Step 801

[0125] A wireless communication channel (e.g. wireless communication channel CH_1, CH_2) is established between the audio source device and the audio playback device, respectively.

[0126] Step 803

[0127] When the audio playback device receives the first audio data outputted by the audio source device and is ready to play the first audio data, the audio playback device transmits a standby notification to the audio source device through the wireless communication channel, respectively, that the audio playback device is in a standby state.

[0128] Step 805

[0129] When the audio source device confirms that all the audio playback devices are in the standby state, the audio source device generates a control instruction to the audio playback devices to start playing the first audio data.

[0130] In an embodiment, after the audio playback device starts playing the audio data, the actual playing time of the audio playback device actually playing the second audio data is collected, and the time difference between the actual playing times is calculated. If the largest time difference is greater than a critical difference, the step 803 and the step 805 are executed again, i.e. the synchronization of the audio playback devices is performed again.

[0131] According to the foregoing embodiments, the synchronization of different Bluetooth earphones can not be limited to the presentation delay in the Bluetooth specification, and the problem that the performance of all Bluetooth earphones in the prior art is limited by Bluetooth earphones with lower performance can be improved.

[0132] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be covered by the present application.

[0133]

Symbol Description

[0134] CH_O OOB wireless communication channel

[0135] CH_1, CH_2 wireless communication channel

[0136] EP_1 first audio playback device

[0137] EP_2 second audio playback device

[0138] EP_a, EP_b, EP_x third audio playback device

[0139] M audio source device

Claims

1. An audio system control method, used in an audio system including a first audio playback device and a second audio playback device, comprising: (a) Establish an out-of-band wireless communication channel between the first audio playback device and the second audio playback device; (b) When the first audio playback device receives the audio data output by the audio source device and is ready to play the audio data, it calculates the first time difference between the current time point and the first expected playback time point; (c) If the current time point is before the first expected playback time point, the first audio playback device transmits a preparation notification representing that the first audio playback device is in a ready state to the second audio playback device through the out-of-band wireless communication channel. (d) If the second audio playback device has received the preparation notification, and has received the audio data output by the audio source device and is ready to play the audio data, then it transmits a start playback notification to the first audio playback device through the out-of-band wireless communication channel to notify the first audio playback device that it can start playback; and (e) After receiving the start playback notification, the first audio playback device and the second audio playback device begin playing the audio data.

2. The audio system control method as described in claim 1, wherein the out-of-band wireless communication channel is a 5G out-of-band channel.

3. The audio system control method as claimed in claim 1, wherein the first audio playback device and the second audio playback device are Bluetooth devices, and step (b) is to calculate the first expected playback time based on the current time and the presentation delay specified in the basic audio specification.

4. The audio system control method as claimed in claim 1, wherein the audio system further includes at least one third audio playback device in addition to the first audio playback device and the second audio playback device, and step (c) further transmits the preparation notification to the third audio playback device, wherein the second audio playback device is the last among all the audio playback devices in the audio system to enter the preparation state.

5. The audio system control method as described in claim 1, wherein if the first audio playback device detects that the first time difference is less than a critical difference while waiting for the start playback notification, the first audio playback device starts playing the audio data.

6. The audio system control method as claimed in claim 1, wherein after the first audio playback device and the second audio playback device start playing the audio data, the first audio playback device or the second audio playback device continuously calculates the actual playback time point and the second expected playback time point of the audio data, and if the number of times the actual playback time point lags behind the second expected playback time point is greater than a critical number, then step (b), step (c), step (d) and step (e) are executed again.

7. An audio system control method, used in an audio system including multiple audio playback devices, comprising: (a) Establish wireless communication channels between the audio source device and the plurality of audio playback devices respectively; (b) When the plurality of audio playback devices receive the first audio data output by the audio source device and are ready to play the first audio data, the plurality of audio playback devices respectively transmit a ready notification that the plurality of audio playback devices are in a ready state to the audio source device through the wireless communication channel. as well as (c) When the audio source device confirms that all of the plurality of audio playback devices are in the ready state, it generates a control command to the plurality of audio playback devices to cause the plurality of audio playback devices to start playing the first audio data.

8. The audio system control method as described in claim 7, wherein the wireless communication channel is a 5G out-of-band channel.

9. The audio system control method as described in claim 7, wherein after the plurality of audio playback devices start playing the audio data, a plurality of actual playback times of the plurality of audio playback devices actually playing the second audio data are collected, and the time difference of the plurality of actual playback times is calculated. If the largest of the time differences is greater than the critical difference, then step (b) and step (c) are executed again.

10. An audio system, comprising: First audio playback device; as well as Second audio playback device; The first audio playback device establishes an out-of-band wireless communication channel between itself and the second audio playback device; When the first audio playback device receives the audio data output by the audio source device and is ready to play the audio data, it calculates the first time difference between the current time point and the first expected playback time point. If the current time point is before the first expected playback time point, the first audio playback device will transmit a preparation notification indicating that the first audio playback device is in a ready state to the second audio playback device through the out-of-band wireless communication channel. If the second audio playback device has received the preparation notification, and has received the audio data output by the audio source device and is ready to play the audio data, then it transmits a start playback notification to the first audio playback device through the out-of-band wireless communication channel to notify the first audio playback device that it can start playback; and After receiving the start playback notification, the first audio playback device and the second audio playback device begin playing the audio data.

Images