Digital conference system and audio clock synchronization method thereof

Abstract

The application provides a digital conference system and an audio clock synchronization method thereof. The synchronization method comprises the following steps: a conference host sends a plurality of audio data packets to a conference unit and records the sending time of each audio data packet; at least one audio data packet, except the first audio data packet, is attached with a reference timestamp, which is the sending time of any reference audio data packet before the audio data packet; the conference unit receives the plurality of audio data packets and records the receiving time of each audio data packet; when receiving each audio data packet attached with the reference timestamp, the conference unit calculates the time difference between the reference timestamp and the receiving time of the reference audio data packet; the conference unit acquires the network delay between the conference host and the conference unit, calculates the difference between the time difference and the network delay, and takes the difference as the clock deviation between the conference host and the conference unit, so as to correct the audio clock of the conference unit according to the clock deviation and realize the audio clock synchronization between the conference host and the conference unit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of audio processing technology, in particular to a digital conference system and an audio clock synchronization method thereof. BACKGROUND

[0002] The digital conference system comprises a conference host and a plurality of conference units communicatively connected to the conference host, and the conference host and each conference unit can transmit audio data to each other. The audio data is data generated by an audio codec according to an audio sampling signal.

[0003] In the related art, the audio clock of the audio codec of the conference host is generated by the crystal oscillator of the conference host, and the audio clock of the audio codec of the conference unit is generated by the crystal oscillator of the conference unit. Since there is an error between the crystal oscillator of the conference host and the crystal oscillator of the conference unit, the audio clocks of the conference host and the conference units are not synchronized, which causes the audio data transmitted between the conference host and the conference units to have an unstable delay and a phase deviation, affecting the audio amplification effect. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the prior art. To this end, the present application provides a digital conference system and an audio clock synchronization method thereof, which can synchronize the audio clocks of the conference host and the conference units in the digital conference system, solve the problem of unstable delay and phase deviation of the audio data transmitted between the conference host and the conference units, and improve the audio amplification effect during use of the digital conference system.

[0005] To achieve the above-mentioned purpose, in one aspect, the present application provides an audio clock synchronization method applied to a digital conference system, the digital conference system comprising a conference host and a plurality of conference units communicatively connected to the conference host, the audio clock synchronization method comprising:

[0006] The conference host sequentially sends a plurality of audio data packets to at least one conference unit and records the sending time of each audio data packet, wherein when sending an audio data packet other than the first audio data packet, the conference host appends a reference timestamp in at least one audio data packet, the reference timestamp being the sending time of a reference audio data packet, and the reference audio data packet being any one of the audio data packets sent by the conference host before the audio data packet where the reference timestamp is located;

[0007] The conference unit receives the audio data packets sent by the conference host, and records the receiving time of each audio data packet. When receiving each audio data packet with the reference timestamp, the conference unit calculates the time difference between the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet; and

[0008] The conference unit acquires the network delay between the conference host and the conference unit, calculates the difference between the time difference and the network delay, and takes the difference as the clock deviation between the conference host and the conference unit, so as to correct the audio clock of the conference unit according to the clock deviation, and realize the synchronization of the audio clock of the conference unit with the audio clock of the conference host.

[0009] In another aspect, the application further provides a digital conference system, which comprises a conference host and a plurality of conference units connected to the conference host in communication;

[0010] The conference host is configured to send a plurality of audio data packets to at least one conference unit in sequence, and record the sending time of each audio data packet. The conference host is further configured to add a reference timestamp to at least one audio data packet other than the first audio data packet in the audio data packets sent by the conference host, wherein the reference timestamp is the sending time of a reference audio data packet, and the reference audio data packet is any one of the audio data packets sent by the conference host and located before the audio data packet with the reference timestamp.

[0011] The conference unit is configured to receive the audio data packets sent by the conference host, and record the receiving time of each audio data packet. When receiving each audio data packet with the reference timestamp, the conference unit calculates the time difference between the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet. The conference unit is further configured to acquire the network delay between the conference host and the conference unit, calculate the difference between the time difference and the network delay, and take the difference as the clock deviation between the conference host and the conference unit, so as to correct the audio clock of the conference unit according to the clock deviation, and realize the synchronization of the audio clock of the conference unit with the audio clock of the conference host.

[0012] The application provides an audio clock synchronization method, which is applied to a digital conference system composed of a conference host and a plurality of conference units.

[0013] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following embodiments are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0015] Figure 1 Fig. 1 is a schematic diagram of a digital conference system according to an embodiment of the present application.

[0016] Figure 2 Fig. 2 is a flowchart of an audio clock synchronization method according to an embodiment of the present application.

[0017] Figure 3 Fig. 3 is a flowchart of a conference host sending an audio data packet.

[0018] Figure 4 Fig. 4 is a flowchart of a conference unit receiving an audio data packet.

[0019] Figure 5 Fig. 5 is a structural block diagram of a conference host according to an embodiment of the present application.

[0020] Figure 6 is a structural block diagram of a conference unit provided by one embodiment of the present application.

[0021] Legend:

[0022] 1 - digital conference system; 10 - conference host; 11 - first processing module; 111 - first local clock module; 12 - first clock signal generation module; 13 - first clock signal calibration module; 131 - first comparator; 132 - first counter; 14 - first audio transceiver module; 15 - first audio codec; 16 - first conversion module; 17 - digital processor; 20 - conference unit; 21 - second processing module; 211 - second local clock module; 212 - third comparator; 22 - second clock signal generation module; 23 - second clock signal calibration module; 231 - second comparator; 232 - second counter; 24 - second audio transceiver module; 25 - second audio codec; 26 - second conversion module. DETAILED DESCRIPTION

[0023] Embodiments of the present application are described in detail below with reference to the attached drawings, which show by way of example, embodiments in which like numerals indicate like elements throughout the several figures. The embodiments described below are exemplary only and are not to be construed as limiting the present application.

[0024] Please refer to Figures 1 to 6 The present application provides an audio clock synchronization method applied to a digital conference system 1, which can realize audio clock synchronization between a conference host 10 and a conference unit 20 in the digital conference system 1, thereby solving the problems of non-fixed delay and phase deviation of audio data transmitted between the conference host 10 and the conference unit 20, and improving the audio amplification effect during use of the digital conference system 1.

[0025] Specifically, please refer to Figure 1The digital conference system 1 comprises a conference host 10 and a plurality of conference units 20 connected to the conference host 10. Optionally, in one possible implementation, the plurality of conference units 20 are connected to the conference host 10 in a hand-in-hand manner through one or more communication cables (not limited to Ethernet cables); in another possible implementation, the plurality of conference units 20 can also be connected to the conference host 10 in a star connection manner through one or more communication cables; in yet another possible implementation, the plurality of conference units 20 can also be connected to the conference host 10 in a ring connection manner through one or more communication cables. In other words, in the embodiments of the present application, the plurality of conference units 20 can be connected to the conference host 10 in any existing connection manner, as long as the mutual transmission of media data and electrical signals between the conference host 10 and any conference unit 20 can be realized as required, which is not limited and described in detail. It should be noted that when the digital conference system 1 is used, the plurality of conference units 20 can be used for participating in the conference, or part of them can be used for participating in the conference. That is, when the digital conference system 1 is used, the conference host 10 communicates with at least one conference unit 20.

[0026] Please refer to Figures 2 to 4 The audio clock synchronization method provided by the present application comprises the following steps.

[0027] Step S1, the conference host 10 sends a plurality of audio data packets to at least one conference unit 20 in turn, and records the sending time of each audio data packet. When sending audio data packets other than the first audio data packet, the conference host 10 appends a reference timestamp to at least one audio data packet, wherein the reference timestamp is the sending time of the reference audio data packet, and the reference audio data packet is any one of the audio data packets sent by the conference host 10 before the audio data packet where the reference timestamp is located.

[0028] As Figure 3As shown, in one embodiment of the present invention, when the conference host 10, as the transmitter of the audio data packet, sends the multiple audio data packets to at least one of the conference units 20 in sequence, it is necessary to first construct the multiple audio data packets in sequence. When constructing the nth audio data packet, the conference host 10 can add the sending time T(n-1) corresponding to the n-1th audio data packet to the nth audio data packet, and then send the nth audio data packet, and record the sending time Tn of the nth audio data packet. After sending the nth audio data packet, the conference host 10 can wait for the construction and sending of the next audio data packet. It is not difficult to understand that the n-1th audio data packet is a reference audio data packet, and its corresponding sending time T(n-1) is the corresponding reference timestamp.

[0029] In step S2, at least one of the conference units 20 receives the multiple audio data packets sent by the conference host 10 and records the reception time of each audio data packet. When each audio data packet with the reference timestamp is received, the conference unit 20 calculates the time difference between the transmission time of the reference audio data packet corresponding to the reference timestamp and the recorded reception time of the reference audio data packet.

[0030] like Figure 4 As shown, in one embodiment of the present invention, as the receiving end of the audio data packet, the conference unit 20 will first determine whether it has received the audio data packet sent by the conference host 10. When the nth audio data packet sent by the conference host 10 is received, the conference unit 20 will record its receiving time tn and obtain the reference timestamp T(n-1) corresponding to the n-1th audio data packet attached to the nth audio data packet. It is not difficult to understand that when the conference unit 20 receives the n-1th audio data packet sent by the conference host 10, it will also record its corresponding receiving time t(n-1). In this way, the conference unit 20 can calculate the time difference (denoted as Tx) between the reference timestamp T(n-1) and the receiving time t(n-1) based on the reference timestamp T(n-1) corresponding to the n-1th audio data packet and the receiving time t(n-1). The time difference Tx is also the time taken for the n-1th audio data packet to be sent by the conference host 10 and received by the conference unit 20.

[0031] Step S3, the conference unit 20 acquires the network delay (denoted as Ty) between itself and the conference host 10, calculates the difference between the time difference Tx and the network delay Ty, and takes the difference as the clock bias (denoted as Tz) between itself and the conference host 10, so as to correct the audio clock of itself according to the clock bias Tz, and realize the audio clock synchronization with the conference host 10.

[0032] As known to those skilled in the art, in specific applications, due to the influence of the communication distance between the conference host 10 and the conference unit 20, or other factors such as electromagnetic interference, there is a certain network delay Ty between the conference host 10 and the conference unit 20. Furthermore, since the conference host 10 and the conference unit 20 have independent clock systems respectively and are not always synchronized, there may be a slight clock bias Tz between the conference host 10 and the conference unit 20. That is, taking the n-1 audio data packets as an example, the time taken for the n-1 audio data packets to be sent by the conference host 10 and received by the conference unit 20 is composed of the network delay Ty between the conference host 10 and the conference unit 20 and the clock bias Tz between the conference host 10 and the conference unit 20, that is, the time difference Tx between the reference timestamp T(n-1) and the reception time t(n-1) is the sum of the network delay Ty and the clock bias Tz. Therefore, after the conference unit 20 calculates the time difference Tx in step S2 and acquires the network delay Ty between itself and the conference host 10, the conference unit 20 can calculate the difference between the time difference Tx and the network delay Ty, which is also the clock bias Tz between the conference unit 20 and the conference host 10, and then the conference unit 20 can correct the audio clock of itself according to the clock bias Tz, and realize the audio clock synchronization with the conference host 10.

[0033] Specifically, in one possible implementation, when the difference between the time difference Tx and the network delay Ty is greater than zero, i.e. the clock deviation Tz between the conference unit 20 and the conference host 10 is greater than zero, it indicates that the audio clock of the conference unit 20 is faster than that of the conference host 10, thus the conference unit 20 needs to slow down its own audio clock according to the clock deviation Tz to realize synchronization with the audio clock of the conference host 10; in another possible implementation, when the difference between the time difference Tx and the network delay Ty is less than zero, i.e. the clock deviation Tz between the conference unit 20 and the conference host 10 is less than zero, it indicates that the audio clock of the conference unit 20 is slower than that of the conference host 10, thus the conference unit 20 needs to speed up its own audio clock according to the clock deviation Tz to realize synchronization with the audio clock of the conference host 10; of course, in yet another possible implementation, when the difference between the time difference Tx and the network delay Ty is equal to zero, i.e. the clock deviation Tz between the conference unit 20 and the conference host 10 is zero, it indicates that the conference unit 20 is synchronized with the audio clock of the conference host 10, and the conference unit 20 does not need to correct its own audio clock.

[0034] It should be noted that in the embodiments of the present application, the conference unit 20 can use existing technologies to obtain the network delay Ty between the conference unit 20 and the conference host 10, for example, by monitoring network communication status and corresponding algorithms, which will not be described herein.

[0035] In summary, the audio clock synchronization method provided by the application is applied to a digital conference system 1 composed of a conference host 10 and a plurality of conference units 20. When the conference host 10 sequentially sends a plurality of audio data packets to the conference units 20 connected in communication thereto, a reference timestamp is attached to at least one audio data packet other than the first audio data packet. The reference timestamp is the sending time of any one of the audio data packets sent by the conference host 10 before the audio data packet where the reference timestamp is located. When the conference units 20 receive the audio data packet with the reference timestamp attached, a time difference can be calculated according to the sending time of the audio data packet corresponding to the reference timestamp and the recorded receiving time of the audio data packet corresponding to the reference timestamp. The time difference is the time taken for the audio data packet corresponding to the reference timestamp to be transmitted from the conference host 10 to the conference units 20. Further, the conference units 20 can calculate the clock deviation between the conference host 10 according to the network delay between the conference units 20 and the conference host 10 and the time difference, and then correct the audio clock of the conference units 20 according to the clock deviation, so as to realize the audio clock synchronization with the conference host 10. In this way, the problem of non-fixed delay and phase deviation of the audio data transmitted between the conference host 10 and the conference units 20 can be effectively solved, and the audio amplification effect during the use of the digital conference system 1 can be improved.

[0036] Preferably, in one embodiment of the application, when sending the audio data packets other than the first audio data packet, the conference host 10 attaches the reference timestamp in each of the audio data packets. In this way, when the conference units 20 receive the audio data packets other than the first audio data packet sent by the conference host 10, a corresponding reference timestamp can be obtained for each received audio data packet, and then the audio clock synchronization with the conference host 10 can be performed according to the reference timestamp. That is to say, in this embodiment, after receiving the first audio data packet sent by the conference host 10, the conference units 20 can perform the audio clock synchronization with the conference host 10 according to the reference timestamp attached to each new audio data packet received, which helps to improve the real-time performance of the audio clock synchronization between the conference units 20 and the conference host 10.

[0037] In other embodiments of the present application, the conference host 10 can also attach the reference timestamp to the audio data packet after every several audio data packets when sending the audio data packets other than the first audio data packet. For example, the conference host 10 can attach the reference timestamp to the next audio data packet to be sent after sending the first audio data packet and after sending every audio data packet. In this way, the conference unit 20 can perform audio clock synchronization with the conference host 10 once after receiving two new audio data packets after receiving the first audio data packet sent by the conference host 10, and the real-time performance of the audio clock synchronization between the conference unit 20 and the conference host 10 can be improved.

[0038] Preferably, in one embodiment of the present application, the reference audio data packet is the last audio data packet sent by the conference host 10 before the audio data packet where the reference timestamp is located, i.e., the last audio data packet received by the conference unit 20. It can be understood that the closer the reference audio data packet corresponding to the reference timestamp is to the audio data packet where the reference timestamp is located in the sending sequence, the smaller the clock deviation accumulation between the conference unit 20 and the conference host 10 when the conference unit 20 acquires the reference timestamp to correct its own audio clock. In this embodiment, by configuring the reference timestamp as the sending time of the last audio data packet received by the conference unit 20, when the conference unit 20 receives the current audio data packet with the reference timestamp attached, the conference unit 20 can perform audio clock synchronization with the conference host 10 according to the relevant time information of the last audio data packet corresponding to the reference timestamp, which helps to improve the accuracy of the audio clock synchronization between the conference unit 20 and the conference host 10.

[0039] Further preferably, in an embodiment of the present application, the conference host 10 sends the plurality of audio data packets to the at least one conference unit 20 one by one, specifically including that the conference host 10 sends a first audio data packet to the at least one conference unit 20, and sends another audio data packet to the conference unit 20 after every interval of a preset time. That is, in the present embodiment, when the conference host 10 sends the plurality of audio data packets to the conference unit 20, the interval time between two adjacent audio data packets in the sending order is a constant value. It is not difficult to understand that, by configuring the conference host 10 to send audio data packets to the conference unit 20 at a constant time, it is equivalent to improving the priority of the conference host 10 in sending audio data packets when the conference host 10 needs to perform tasks, which can reduce or even avoid the influence of the conference host 10 in performing other tasks on sending the audio data packets, improve the stability of the transmission of audio data packets between the conference unit 20 and the conference host 10, and further help to ensure that the clock deviation between the conference unit 20 and the conference host 10 changes within a stable range, and improve the synchronization of the audio clock between the conference unit 20 and the conference host 10.

[0040] It should be noted that, in the embodiments of the present application, the conference host 10 and the conference unit 20 each include a plurality of hardware functional modules to implement the audio clock synchronization method through the plurality of hardware functional modules. Next, the hardware functional modules of the conference host 10 and the conference unit 20 and the principles of the related steps of the audio clock synchronization method implemented by the hardware functional modules will be described in detail. Figure 5 and Figure 6 The hardware functional modules of the conference host 10 and the conference unit 20 and the principles of the related steps of the audio clock synchronization method implemented by the hardware functional modules will be described in detail.

[0041] Please refer to Figure 5 In the embodiments of the present application, the conference host 10 includes a first processing module 11, a first clock signal generation module 12, and a first clock signal calibration module 13 connected with the first processing module 11 and the first clock signal generation module 12, respectively. The first processing module 11 includes a first local clock module 111 for generating a first local clock (also referred to as a first network clock). Preferably, in an embodiment of the present application, the audio clock synchronization method further includes the following steps:

[0042] After the conference host 10 sends the first audio data packet to at least one of the conference units 20, the first local clock module 111 generates a first timing interrupt signal containing the first local clock, and the first clock signal calibration module 13 acquires the first timing interrupt signal and corrects the output frequency of the first clock signal generated by the first clock signal generation module 12 according to the first local clock contained in the first timing interrupt signal. The corrected first clock signal serves as the audio clock signal Clk of the conference host 10.

[0043] As known by those skilled in the art, the clock of a conference host generally includes a local clock reference for recording the time of sending and receiving audio data packets and an audio clock reference for collecting audio signals. Generally, the local clock reference and the audio clock reference are synchronized, but due to the working characteristics (e.g., the crystal oscillator of a voltage-controlled oscillator) of the functional module (generally, a voltage-controlled oscillator or a frequency synthesizer) for generating an audio clock signal, there is a slight deviation between the local clock reference and the audio clock reference. In the embodiment, according to the first timing interrupt signal containing the first local clock generated by the first local clock module 111, the first clock signal generation module 12 can correct the output frequency of the first clock signal generated thereby. The corrected first clock signal serves as the audio clock signal Clk of the conference host 10, and the synchronization between the first local clock and the audio clock signal Clk of the conference host 10 can be achieved. In this way, the conference host 10 records the sending time of each audio data packet based on the first local clock, and then appends the reference time stamp (i.e., the sending time of the reference audio data packet) to at least one of the audio data packets and sends it to the conference units 20, so that the synchronization between the audio clock of the conference units 20 and the first local clock of the conference host 10, i.e., the synchronization between the audio clock of the conference units 20 and the audio clock of the conference host 10, can be achieved, and the synchronization accuracy is high.

[0044] It should be noted that, in the embodiments of the present application, the first processing module 11 can be, but is not limited to, a central processing unit, a general-purpose processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, etc., and the first clock signal generation module 12 can be, but is not limited to, a voltage-controlled oscillator or a frequency synthesizer, and the present application is not limited in this regard.

[0045] As Figure 5As shown, in one embodiment of the present invention, the first clock signal calibration module 13 specifically includes a first comparator 131 and a first counter 132. The first comparator 131 is connected to the first local clock module 111 and the first clock signal generation module 12, respectively, and the first counter 132 is connected to the first comparator 131 and the first clock signal generation module 12, respectively. The functions of the first comparator 131 and the first counter 132 are the same as those of existing comparators and counters, and are not described in detail here.

[0046] In a possible implementation, in the aforementioned steps, the first clock signal calibration module 13 obtains the first timing interrupt signal and corrects the output frequency of the first clock signal generated by the first clock signal generation module 12 according to the first local clock included in the first timing interrupt signal, specifically including the following steps:

[0047] In the first step, when the first comparator 131 receives the first timing interrupt signal, it obtains the number of pulses of the first clock signal generated by the first clock signal generating module 12 by the first counter 132 ( Figure 5 Plus) and controls the count of the first counter 132 to be cleared. After the first counter 132 is cleared, it can be used for counting in a new cycle.

[0048] In a second step, the first comparator 131 calculates the current output frequency of the first clock signal based on the total count, and determines the speed of the current output frequency of the first clock signal in combination with the first local clock included in the first timer interrupt signal. It is readily understood that, due to the operating characteristics of the first clock signal generating module 12 (e.g., the crystal oscillator of a voltage-controlled oscillator), there may be a slight deviation between the first clock signal generated by the module and the first local clock. The current output frequency of the first clock signal may be faster than, slower than, or synchronized with the output frequency of the first local clock.

[0049] In the third step, the first comparator 131 outputs a corresponding first correction signal based on its determination of the current output frequency of the first clock signal, thereby triggering the first clock signal generation module 12 to correct the output frequency of the first clock signal based on the first correction signal. For example, when the first clock signal generation module 12 utilizes a voltage-controlled oscillator, the first comparator 131 may output the first correction signal to a voltage controller connected to the voltage-controlled oscillator. By controlling the voltage value provided by the voltage controller to the voltage-controlled oscillator, the frequency of the output signal of the voltage-controlled oscillator can be corrected.

[0050] Of course, in another possible implementation, in the first step described above, when the first comparator 131 receives the first timing interrupt signal, it may also control the first counter 132 to count the number of pulses (i.e., the number of Plus) of the first clock signal generated by the first clock signal generation module 12 within a first timing interrupt period (e.g., 1s) corresponding to the first timing interrupt signal, and feed the total count back to the first comparator 131. The first comparator 131 continues to perform the second and third steps described above based on the total count, and can also achieve correction of the output frequency of the first clock signal.

[0051] It is understandable that, in the embodiment of the present invention, the sending period of the first timing interrupt signal can be set to 1s, 2s, 3s or other reasonable time according to actual needs, and there is no limitation on this.

[0052] Please refer again Figure 5 In one embodiment of the present invention, the conference host 10 further includes a first audio transceiver module 14 electrically connected to the first processing module 11. The first audio transceiver module 14 is configured to receive audio data (shown as Data in) transmitted by any of the conference units 20 and to transmit audio data (shown as Data out) to any of the conference units 20. The first audio transceiver module 14 may, but is not limited to, utilize an existing network chip having a physical interface transceiver. The physical interface transceiver can record the corresponding transmission or reception time of audio data passing through the physical interface transceiver. The first audio transceiver module 14 can further transmit the recorded relevant time to the first local clock module 111 of the first processing module 11 via a network protocol such as IEEE1588. Thus, before the first audio transceiver module 14 transmits audio data to any of the conference units 20, the first local clock module 111 can append a corresponding reference timestamp to the audio data packet. The specific operating principle of the first audio transceiver module 14 is the same as that of existing audio transceiver modules and is not further described.

[0053] Furthermore, if Figure 5As shown in the embodiment of the present application, the conference host 10 further comprises a first audio codec 15 and a first conversion module 16 electrically connected to the first audio codec 15. The first audio codec 15 acquires the corrected first clock signal Clk generated by the first clock signal generation module 12 (i.e. the audio clock signal of the conference host 10) and controls the first conversion module 16 to perform analog-digital conversion on audio data according to the first clock signal Clk. For example, in a possible implementation, the first audio codec 15 controls the first conversion module 16 to convert the analog signal of audio data input by an analog audio device (such as a microphone or an external line input device) into a digital signal according to the first clock signal Clk, so as to transmit the audio data to any of the conference units 20 (Audio in). In another possible implementation, the first audio codec 15 controls the first conversion module 16 to convert the digital signal of audio data transmitted by any of the conference units 20 into an analog signal according to the first clock signal Clk, so as to transmit the audio data to a loudspeaker or other sound amplification device for sound amplification and external playing (Audio out). Figure 5 As shown in the embodiment of the present application, the conference host 10 further comprises a first audio codec 15 and a first conversion module 16 electrically connected to the first audio codec 15. The first audio codec 15 acquires the corrected first clock signal Clk generated by the first clock signal generation module 12 (i.e. the audio clock signal of the conference host 10) and controls the first conversion module 16 to perform analog-digital conversion on audio data according to the first clock signal Clk. For example, in a possible implementation, the first audio codec 15 controls the first conversion module 16 to convert the analog signal of audio data input by an analog audio device (such as a microphone or an external line input device) into a digital signal according to the first clock signal Clk, so as to transmit the audio data to any of the conference units 20 (Audio in). In another possible implementation, the first audio codec 15 controls the first conversion module 16 to convert the digital signal of audio data transmitted by any of the conference units 20 into an analog signal according to the first clock signal Clk, so as to transmit the audio data to a loudspeaker or other sound amplification device for sound amplification and external playing (Audio out). Figure 5

[0054] In the embodiment of the present application, the first audio codec 15 and the first conversion module 16 can adopt existing audio codec and digital-analog conversion module, and the specific structure and function thereof will not be described herein. Alternatively, the first audio codec 15 and the first conversion module 16 can be integrated or separately arranged, and the present application is not limited in this aspect.

[0055] Further, as shown in the embodiment of the present application, the conference host 10 further comprises a digital processor 17. The digital processor 17 acquires the corrected first clock signal Clk generated by the first clock signal generation module 12 and performs different audio processing (such as gain, noise reduction, sound mixing and synthesis) on the audio data received thereby according to the first clock signal Clk. The digital processor 17 can adopt existing digital audio processor, and the specific structure and function thereof will not be described herein. Figure 6 As shown in the embodiment of the present application, the conference host 10 further comprises a digital processor 17. The digital processor 17 acquires the corrected first clock signal Clk generated by the first clock signal generation module 12 and performs different audio processing (such as gain, noise reduction, sound mixing and synthesis) on the audio data received thereby according to the first clock signal Clk. The digital processor 17 can adopt existing digital audio processor, and the specific structure and function thereof will not be described herein.

[0056] As shown in the embodiment of the present application, the conference host 10 further comprises a digital processor 17. The digital processor 17 acquires the corrected first clock signal Clk generated by the first clock signal generation module 12 and performs different audio processing (such as gain, noise reduction, sound mixing and synthesis) on the audio data received thereby according to the first clock signal Clk. The digital processor 17 can adopt existing digital audio processor, and the specific structure and function thereof will not be described herein. Figure 6 As shown in the embodiment of the present application, the conference host 10 further comprises a digital processor 17. The digital processor 17 acquires the corrected first clock signal Clk generated by the first clock signal generation module 12 and performs different audio processing (such as gain, noise reduction, sound mixing and synthesis) on the audio data received thereby according to the first clock signal Clk. The digital processor 17 can adopt existing digital audio processor, and the specific structure and function thereof will not be described herein.

[0057] ​In the aforementioned step S2, when each audio data packet with the reference timestamp attached is received, the conference unit 20 calculates the time difference between the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet, specifically including: the second processing module 21 obtains the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet, and calculates the time difference Tx between the two.

[0058] In the aforementioned step S2, the conference unit 20 obtains the network delay Ty between the conference host 10, calculates the difference between the time difference Tx and the network delay Ty, and uses the difference as the clock deviation Tz between the conference host 10 to correct its own audio clock according to the clock deviation Tz. Specifically, the following two steps are included:

[0059] Step 1: The second processing module 21 obtains the network delay Ty between the second processing module 21 and the conference host 10, calculates the difference between the time difference Tx and the network delay Ty, and uses the difference as the clock deviation Tz between the second processing module 21 and the conference host 10, so as to generate a second timing interrupt signal including the clock deviation Tz according to the clock deviation Tz;

[0060] In step 2, the second clock signal calibration module 23 obtains the second timing interrupt signal, and corrects the output frequency of the second clock signal generated by the second clock signal generation module 22 according to the clock deviation Tz contained in the second timing interrupt signal. The corrected second clock signal serves as the audio clock signal Clk of the conference unit 20.

[0061] Among them, similar to the aforementioned first processing module 11, the second processing module 21 can be but is not limited to a central processing unit, a general-purpose processor, a dedicated integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, etc.; similarly, the second clock signal generation module 22 can be but is not limited to a voltage-controlled oscillator or a frequency synthesizer, and there is no limitation on this.

[0062] like Figure 6 As shown, in one embodiment of the present invention, the second clock signal calibration module 23 specifically includes a second comparator 231 and a second counter 232. The second comparator 231 is connected to the second processing module 21 and the second clock signal generation module 22, respectively, and the second counter 232 is connected to the second comparator 231 and the second clock signal generation module 22, respectively. The functions of the second comparator 231 and the second counter 232 are the same as those of existing comparators and counters, and are not described in detail here.

[0063] In one possible implementation, in the aforementioned step 2, the second clock signal calibration module 23 obtains the second timing interrupt signal and corrects the output frequency of the second clock signal generated by the second clock signal generation module 22 according to the clock deviation Tz included in the second timing interrupt signal, specifically including the following steps:

[0064] First, when the second comparator 231 receives the second timing interrupt signal, it obtains the number of pulses of the second clock signal generated by the second clock signal generating module 22 by the second counter 232 ( Figure 6 Plus) and controls the count of the second counter 232 to be cleared. After the second counter 232 is cleared, it can be used for counting in a new cycle.

[0065] Next, the second comparator 231 calculates the current output frequency of the second clock signal based on the total count, and determines the speed of the current output frequency of the second clock signal in combination with the clock deviation Tz contained in the second timing interrupt signal. As previously mentioned, if the clock deviation Tz is greater than zero, it means that the audio clock of the conference unit 20 is faster than the audio clock of the conference host 10, that is, the output frequency of the audio clock signal of the conference unit 20 (i.e., the second clock signal) is too fast; if the clock deviation Tz is less than zero, it means that the audio clock of the conference unit 20 is slower than the audio clock of the conference host 10, that is, the output frequency of the second clock signal is too slow; if the clock deviation Tz is zero, it means that the audio clocks of the conference unit 20 and the conference host 10 are synchronized, and the output frequency of the second clock signal does not need to be corrected.

[0066] Finally, the second comparator 231 outputs a corresponding second correction signal based on its determination of the current output frequency of the second clock signal, thereby triggering the second clock signal generation module 22 to correct the output frequency of the second clock signal based on the second correction signal. Similar to the aforementioned first clock signal generation module 12, when the second clock signal generation module 22 utilizes a voltage-controlled oscillator, the second comparator 231 can output the second correction signal to a voltage controller connected to the voltage-controlled oscillator. By controlling the voltage value provided by the voltage controller to the voltage-controlled oscillator, the frequency of the output signal of the voltage-controlled oscillator can be corrected.

[0067] Of course, in another possible implementation, when the second comparator 231 receives the second timing interrupt signal, it can also control the second counter 232 to count the number of pulses of the second clock signal generated by the second clock signal generation module 22 within the second timing interrupt period (e.g. 1s) corresponding to the second timing interrupt signal, and feed the count sum to the second comparator 231. The second comparator 231 continues to perform the following two steps according to the count sum, and the output frequency of the second clock signal can also be corrected.

[0068] It can be understood that, in the embodiments of the present application, the sending period of the second timing interrupt signal can also be set to 1s, 2s, 3s or other reasonable time according to actual needs, similar to the aforementioned first timing interrupt signal, which is not limited.

[0069] Please refer again to Figure 6 In one of the embodiments of the present application, each conference unit 20 further comprises a second audio transceiver module 24 electrically connected to the second processing module 21. Similar to the function of the aforementioned first audio transceiver module 14, the second audio transceiver module 24 is used to receive and send audio data packets and record the receiving time of the audio data packets, and is also used to obtain the network delay between the conference unit 20 and the conference host 10.

[0070] The second audio transceiver module 24 can also but not limited to use the existing network chip with a physical interface transceiver. The physical interface transceiver can record the sending time or receiving time of the audio data when passing through the physical interface transceiver, and the second audio transceiver module 24 can further send the recorded related time to the second processing module 21 through IEEE1588 or other network protocols. The specific working principle of the second audio transceiver module 24 is the same as that of the existing audio transceiver module, which is not described here.

[0071] As shown in Figure 6 In one of the embodiments of the present application, the second processing module 21 comprises a third comparator 212 and a second local clock module 211 for generating a second local clock, the third comparator 212 is connected to the second audio transceiver module 24 and the second local clock module 211 respectively, and the second local clock module 211 is connected to the second clock signal calibration module 23 (specifically connected to the second comparator 231).

[0072] In the foregoing step, the second processing module 21 acquires the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet, and calculates the time difference Tx therebetween, specifically including the following two steps:

[0073] Firstly, the second audio transceiver module 24 receives each of the audio data packets sent by the conference host 10, and records the receiving time of each of the audio data packets, while acquiring the network delay Ty between the conference unit 20 and the conference host 10;

[0074] Secondly, the third comparator 212 acquires the receiving time of the reference audio data packet recorded by the second audio transceiver module and the sending time of the reference audio data packet corresponding to the reference timestamp received by the second audio transceiver module 24, to calculate the time difference Tx therebetween.

[0075] In the foregoing step, the second processing module 21 acquires the network delay Ty between the conference host 10, calculates the difference between the time difference Tx and the network delay Ty, and takes the difference as the clock deviation Tz between the conference host 10, to generate the second timing interrupt signal containing the clock deviation Tz according to the clock deviation Tz, specifically including the following two steps:

[0076] Firstly, the third comparator 212 acquires the network delay Ty between the conference unit 20 and the conference host 10 acquired by the second audio transceiver module 24, and calculates the difference between the network delay Ty and the time difference Tz, to send the difference as the clock deviation Tz between the conference host 10 to the second local clock module 211;

[0077] Then, the second local clock module 211 corrects the generated second local clock according to the clock deviation Tz, realizes the time synchronization of the local clocks between the conference unit 20 and the conference host 10, and generates the second timing interrupt signal containing the clock deviation Tz according to the clock deviation Tz, to send to the second clock signal calibration module 23 (specifically to the second comparator 231). After the second comparator 231 acquires the clock deviation Tz, it can execute the corresponding steps to realize the correction of the second clock signal, which will not be described here.

[0078] It can be understood that through the above steps, the time synchronization of the local clocks between the conference unit 20 and the conference host 10 is realized, which helps to improve the accuracy of the audio clock synchronization between the conference unit 20 and the conference host 10.

[0079] As Figure 6In one of the embodiments of the present application, as shown, each of the conference units 20 further comprises a second audio codec 25 and a second conversion module 26 electrically connected to the second audio codec 25. The second audio codec 25 acquires the corrected second clock signal Clk (i.e. the audio clock signal of the conference unit 20) generated by the second clock signal generation module 22, and controls the second conversion module 26 to perform analog-digital conversion on audio data according to the second clock signal Clk. In one possible implementation, the second audio codec 25 controls the second conversion module 26 to convert the analog signal of the audio data input by a sound pickup device (Audio in) into a digital signal, so as to transmit the audio data to the conference host 10; in another possible implementation, the second audio codec 25 controls the second conversion module 26 to convert the digital signal of the audio data sent by the conference host 10 into an analog signal, so as to send the analog signal to the loudspeaker or earphone output end of the conference unit 20 for listening (Audio out). Figure 1 ​

[0080] It should be noted that the second audio codec 25 and the second conversion module 26 can also adopt existing audio codec and digital-analog conversion modules, and the specific structure and functions thereof are not described herein. Alternatively, the second audio codec 25 and the second conversion module 26 can be integrated, or can be independently arranged, and no limitation is made in this regard.

[0081] It should be noted that in the embodiments of the present application, the audio data transmitted between the conference host 10 and the conference units 20 includes but is not limited to audio data in the formats of WAV, MP3, WMA, etc.

[0082] Further, referring again to ​ The embodiments of the present application further provide a digital conference system 1 comprising a conference host 10 and a plurality of conference units 20 communicatively connected to the conference host 10.

[0083] The conference host 10 is configured to sequentially send a plurality of audio data packets to at least one of the conference units 20, and record the sending time of each of the audio data packets. The conference host 10 is further configured to attach a reference timestamp to at least one of the audio data packets other than the first audio data packet sent by the conference host 10, wherein the reference timestamp is the sending time of a reference audio data packet, and the reference audio data packet is any one of the audio data packets sent by the conference host 10 and located before the audio data packet where the reference timestamp is located. ​​

[0084] The conference unit 20 is used to receive the multiple audio data packets sent by the conference host 10, record the reception time of each audio data packet, and, when receiving each audio data packet with the reference timestamp attached, calculate the time difference between the transmission time of the reference audio data packet corresponding to the reference timestamp and the recorded reception time of the reference audio data packet; the conference unit 20 is also used to obtain the network delay between the conference host 10, calculate the difference between the time difference and the network delay, and use the difference as the clock deviation between the conference host 10, so as to correct its own audio clock according to the clock deviation and achieve audio clock synchronization with the conference host 10.

[0085] During use, the digital conference system 1 provided by an embodiment of the present invention can employ the audio clock synchronization method described in any of the aforementioned embodiments to achieve audio clock synchronization between the conference host 10 and the conference unit 20. This resolves the issues of non-fixed delay and phase deviation in audio data transmitted between the conference host 10 and the conference unit 20, thereby improving the audio amplification effect during use of the digital conference system 1. For more details, please refer to the aforementioned related description and will not be elaborated on here.

[0086] It should be noted that, similar to existing digital conference systems, the digital conference system 1 may also include other components such as a network switch, a sound pickup device, and a sound amplification device, which will not be described in detail.

[0087] In the description of the present invention, reference to terms such as "embodiment," "specific embodiment," and "example" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0088] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. An audio clock synchronization method, applied to a digital conference system, wherein the digital conference system comprises a conference host and a plurality of conference units communicatively connected to the conference host, characterized in that: The audio clock synchronization method comprises: The conference host sequentially sends multiple audio data packets to at least one of the conference units and records the sending time of each of the audio data packets, wherein when sending other audio data packets except the first audio data packet, the conference host appends a reference timestamp to at least one audio data packet, where the reference timestamp is the sending time of the reference audio data packet, and the reference audio data packet is any audio data packet sent by the conference host and located before the audio data packet containing the reference timestamp; at least one of the conference units receives the plurality of audio data packets sent by the conference host and records the reception time of each of the audio data packets, wherein, upon receiving each of the audio data packets with the reference timestamp attached, the conference unit calculates the time difference between the transmission time of the reference audio data packet corresponding to the reference timestamp and the recorded reception time of the reference audio data packet; and The conference unit obtains the network delay between itself and the conference host, calculates the difference between the time difference and the network delay, and uses the difference as the clock deviation between itself and the conference host, so as to correct its own audio clock according to the clock deviation and achieve audio clock synchronization with the conference host.

2. The audio clock synchronization method according to claim 1, wherein: When sending other audio data packets except the first audio data packet, the conference host appends the reference timestamp to each of the audio data packets.

3. The audio clock synchronization method according to claim 1, wherein: The reference audio data packet is a previous audio data packet sent by the conference host and located before the audio data packet where the reference timestamp is located.

4. The audio clock synchronization method according to claim 1, wherein: The conference host sequentially sends a plurality of audio data packets to at least one of the conference units, specifically comprising: The conference host sends a first audio data packet to at least one of the conference units, and sends another audio data packet to the conference unit after a preset time interval.

5. The audio clock synchronization method according to claim 1, wherein: The conference host includes a first processing module, a first clock signal generating module, and a first clock signal calibration module connected to the first processing module and the first clock signal generating module respectively, wherein the first processing module includes a first local clock module for generating a first local clock, and the audio clock synchronization method further includes: After the conference host sends the first audio data packet to at least one of the conference units, the first local clock module generates a first timing interrupt signal containing the first local clock. The first clock signal calibration module obtains the first timing interrupt signal and corrects the output frequency of the first clock signal generated by the first clock signal generation module according to the first local clock contained in the first timing interrupt signal. The corrected first clock signal serves as the audio clock signal of the conference host.

6. The audio clock synchronization method according to claim 5, wherein: The first clock signal calibration module includes a first comparator and a first counter, the first comparator is connected to the first local clock module and the first clock signal generation module respectively, and the first counter is connected to the first comparator and the first clock signal generation module respectively; The first clock signal calibration module obtains the first timing interrupt signal and corrects the output frequency of the first clock signal generated by the first clock signal generation module according to the first local clock included in the first timing interrupt signal, specifically including: When the first comparator receives the first timing interrupt signal, it obtains the total number of pulses of the first clock signal generated by the first clock signal generating module counted by the first counter, and controls the count of the first counter to be reset to zero; The first comparator calculates the current output frequency of the first clock signal according to the count sum, and determines the speed of the current output frequency of the first clock signal in combination with the first local clock included in the first timing interrupt signal; The first comparator outputs a corresponding first correction signal based on the speed result of the current output frequency of the first clock signal determined by it, so as to trigger the first clock signal generation module to correct the output frequency of the first clock signal according to the first correction signal.

7. The audio clock synchronization method according to any one of claims 1 to 6, wherein: Each of the conference units includes a second processing module, a second clock signal generating module, and a second clock signal calibration module connected to the second processing module and the second clock signal generating module respectively; Upon receiving each of the audio data packets with the reference timestamp attached thereto, the conference unit calculates the time difference between the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet, specifically including: The second processing module obtains the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet, and calculates the time difference between the two; The conference unit obtains the network delay between the conference host and the conference unit, calculates the difference between the time difference and the network delay, and uses the difference as the clock deviation between the conference host and the conference unit to correct the audio clock of the conference unit according to the clock deviation, specifically including: The second processing module obtains the network delay between the conference host and the second processing module, calculates the difference between the time difference and the network delay, and uses the difference as the clock deviation between the second processing module and the conference host, so as to generate a second timing interrupt signal including the clock deviation according to the clock deviation; The second clock signal calibration module obtains the second timing interrupt signal, and corrects the output frequency of the second clock signal generated by the second clock signal generation module according to the clock deviation contained in the second timing interrupt signal. The corrected second clock signal serves as the audio clock signal of the conference unit.

8. The audio clock synchronization method according to claim 7, wherein: The second clock signal calibration module includes a second comparator and a second counter, the second comparator is connected to the second processing module and the second clock signal generation module respectively, and the second counter is connected to the second comparator and the second clock signal generation module respectively; The second clock signal calibration module obtains the second timing interrupt signal and corrects the output frequency of the second clock signal generated by the second clock signal generation module according to the clock deviation included in the second timing interrupt signal, specifically including: When the second comparator receives the second timing interrupt signal, it obtains the total number of pulses of the second clock signal generated by the second clock signal generating module counted by the second counter, and controls the count of the second counter to be cleared; The second comparator calculates the current output frequency of the second clock signal according to the count sum, and determines the speed of the current output frequency of the second clock signal in combination with the clock deviation included in the second timing interrupt signal; The second comparator outputs a corresponding second correction signal based on the speed result of the current output frequency of the second clock signal determined by it, so as to trigger the second clock signal generation module to correct the output frequency of the second clock signal according to the second correction signal.

9. The audio clock synchronization method according to claim 7, wherein: Each of the conference units further includes an audio transceiver module, which is used to receive and send audio data packets and record the reception time of the audio data packets, and is also used to obtain the network delay between the conference unit and the conference host; The second processing module includes a third comparator and a second local clock module for generating a second local clock, the third comparator is connected to the audio transceiver module and the second local clock module respectively, and the second local clock module is connected to the second clock signal calibration module; The second processing module obtains the sending time of the reference audio data packet corresponding to the reference timestamp and the recorded receiving time of the reference audio data packet, and calculates the time difference between the two, specifically including: The audio transceiver module receives each audio data packet sent by the conference host, records the reception time of each audio data packet, and obtains the network delay between the conference unit and the conference host; The third comparator obtains the reception time of the reference audio data packet recorded by the audio transceiver module and the sending time of the reference audio data packet corresponding to the reference timestamp received by the audio transceiver module, so as to calculate a time difference between the two; The second processing module obtains the network delay between the second processing module and the conference host, calculates the difference between the time difference and the network delay, and uses the difference as the clock deviation between the second processing module and the conference host, so as to generate a second timing interrupt signal including the clock deviation according to the clock deviation, specifically including: The third comparator obtains the network delay between the conference unit and the conference host obtained by the audio transceiver module, and calculates the difference between the network delay and the time difference, so as to send the difference as the clock deviation between the conference host and the second local clock module; The second local clock module synchronizes the local clocks between the conference unit and the conference host based on the second local clock generated by the clock deviation correction, and generates a second timing interrupt signal containing the clock deviation based on the clock deviation to send to the second clock signal calibration module.

10. A digital conference system, characterized in that: It includes a conference host and a plurality of conference units communicatively connected to the conference host; The conference host is used to sequentially send multiple audio data packets to at least one of the conference units and record the sending time of each audio data packet. The conference host is further used to attach a reference timestamp to at least one of the other audio data packets sent by the conference host except the first audio data packet, where the reference timestamp is the sending time of the reference audio data packet, and the reference audio data packet is any audio data packet sent by the conference host that is located before the audio data packet with the reference timestamp. The conference unit is used to receive the multiple audio data packets sent by the conference host, record the reception time of each audio data packet, and when receiving each audio data packet with the reference timestamp attached, calculate the time difference between the transmission time of the reference audio data packet corresponding to the reference timestamp and the recorded reception time of the reference audio data packet; the conference unit is also used to obtain the network delay between the conference host, calculate the difference between the time difference and the network delay, and use the difference as the clock deviation between the conference host, so as to correct its own audio clock according to the clock deviation and achieve audio clock synchronization with the conference host.

11. The digital conference system according to claim 10, wherein: The conference host adds the reference timestamp to each of the audio data packets sent by the conference host except the first audio data packet.

12. The digital conference system according to claim 10, wherein: The reference audio data packet is a previous audio data packet sent by the conference host and located before the audio data packet where the reference timestamp is located.

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