CN115175298A - Audio signal Bluetooth low-delay transmission method based on PC-SPDIF - Google Patents
Audio signal Bluetooth low-delay transmission method based on PC-SPDIF Download PDFInfo
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Abstract
A low-delay Bluetooth wireless signal transmission method based on a PC-SPDIF interface relates to a wireless signal transmission technology, and comprises the steps of connecting a Bluetooth chip A with an SPDIF interface to an SPDIF interface on the PC, then utilizing built-in software of the Bluetooth chip A to obtain the sampling frequency of an audio SPDIF source end, calculating a deviation value between the sampling frequency of the audio SPDIF source and the sampling frequency of the Bluetooth chip A through software, then enabling data to be adjusted according to a plurality of +/-0.5 microseconds in each transmission period through a method of dynamically adjusting a time interval PT of signal transmission data, then utilizing built-in software of a Bluetooth chip B of a receiving end to obtain the sampling frequency deviation of a transmitting end A and the receiving end B, then calculating the deviation value between the sampling frequency of the SPDIF source and the sampling frequency of the receiving end B, enabling the audio signals of the transmitting end and the receiving end to be identical through a sampling frequency adjusting method of the Bluetooth chip B, and optimizing output signals.
Description
Technical Field
The invention relates to the technical field of wireless transmission, in particular to a Bluetooth low-delay transmission method of an audio signal based on a PC-SPDIF.
Background
The Bluetooth technology is used as a short-distance wireless transmission technology, the application is very wide, the traditional intelligent equipment generally does not have the transmission capability of Bluetooth, the application of data transmission is very difficult to solve aiming at some equipment without Bluetooth communication capability, the stability of simultaneous transmission and the quality of transmission audio frequency also have higher requirements, the stability of data transmission and the quality of transmission audio frequency are improved at present, an extended Bluetooth connector is generally adopted, but the connector is due to the diversification of equipment interfaces and protocols, and the difference of signals is added, and the processed data is generally not high in quality.
Sampling frequencies generated by any equipment and chips cannot be completely consistent, in the process of transmitting and transmitting the Bluetooth signals, in order to ensure that the signal playing effect is optimal, the same frequency of the signals is very important, most Bluetooth playing terminals do not optimize or process the signals, and the output signal effect is poor; or the processing is excessive, and the output signal is distorted; or other signal loss and interruption conditions occur.
Disclosure of Invention
The invention aims to provide a Bluetooth low-delay transmission method of an audio signal based on PC-SPDIF (personal computer-short digital television), which keeps the synchronization of a transmitting signal main device and a wireless transmission transmitting end clock to ensure that data at the transmitting end does not overflow or interrupt, thereby ensuring that the transmitted signal quality is higher, the output signal is closer to the original audio signal, and then the data which is infinitely close to the original signal can be output without any signal adjustment by utilizing a sampling frequency adjusting method and a hardware or software adjusting method.
In order to achieve the purpose, the invention adopts the following technical scheme: the Bluetooth low-delay transmission method of the audio signal based on the PC-SPDIF comprises the following steps:
connecting a Bluetooth chip with SPDIF to a PC (personal computer), wherein the sampling frequency generated by the source of audio on the PC is F 0 The sampling frequency generated by the Bluetooth chip with SPDIF is F 1 The source of the audio on the PC is a main device for sending signals, and the Bluetooth chip with the SPDIF is a wireless transmission sending end;
step two, acquiring the sampling frequency F generated by the audio source in the step one by using the built-in software of the Bluetooth chip 0 And the sampling frequency F generated by the Bluetooth chip with SPDIF 1 Calculating, by said software, a sampling frequency F resulting from the source of the audio 0 With the bluetooth chip product of taking SPDIFRaw sampling frequency F 1 A deviation value Δ F1 therebetween;
step three, according to the delta F1 in the step two, the data is adjusted according to one or more +/-0.5 mu s in each transmission period by a method of dynamically adjusting the time interval PT of the signal transmission data, so that the data of the sending end does not overflow or is interrupted, and F is obtained 0 ＝F 1 ；
And step four, the Bluetooth chip with the SPDIF sends a wireless audio signal.
Further, the deviation value Δ F1 in the second step is obtained by measuring a deviation between clocks of the signal sending main device and the wireless transmission sending end in the first step, and the deviation is calculated by measuring a time of the wireless transmission sending end receiving a block of data packet of the signal sending main device.
Further, the deviation calculation formula is,
in the formula, RXppm1 represents the time deviation of the clock of the signal sending main equipment and the clock of the wireless transmission sending end;
furthermore, the method for dynamically adjusting the time interval PT1 of the signal transmission data in step three is to take ± 0.5 μ s as unit time to adjust PT, and by using the following formula,
RXppm1= ± 0.5 μ s/(PT 1 × M), this formula is further transformed,
M＝±0.5μS/(PT1×PXppm)，
in the formula, RT1 represents the time interval of signal transmission data,
m represents the number of 0.5us left or right shifts in each PT interval, and the fractional part of M is approximately represented by a decimal number 32.
Step five, the Bluetooth chip with the SPDIF is wirelessly connected with the Bluetooth chip through Bluetooth to form a sending end and a receiving end;
step six, acquiring the first sampling frequency F of the transmitting end in the step five by using the Bluetooth chip built-in software 1 And a second sampling frequency F of the receiving end 2 And the output audio signal M of the Bluetooth chip of the sending end 1 And the output audio signal M of the Bluetooth chip of the receiving end 2 Calculating a first sampling frequency F by said software 1 And a second sampling frequency F 2 A deviation value Δ F2 therebetween;
step seven, according to the delta F2 in the step six, the output audio signal M of the Bluetooth chip at the receiving end is enabled to be obtained through a digital signal dynamic synchronization algorithm or a phase-locked loop PLL (phase-locked loop) regulation 2 = output audio signal M of bluetooth chip of transmitting end 1 ；
And step eight, outputting the audio.
Further, Δ F2 in the sixth step is a deviation value between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the transmitting end, and the deviation value is calculated by measuring a time interval PT2 of receiving the data packet of the second sampling frequency at the receiving end.
Further, the calculation formula of the deviation value between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the transmitting end is RXppm2=1000000 × (PT 2rx-PT 2)/PT 2,
in the formula (I), the compound is shown in the specification,
RXppm2 represents the time deviation of the clock of the second sampling frequency of the receiving end and the first sampling frequency of the transmitting end,
RT2rx denotes the time interval of packet reception at the second sampling frequency at the receiving end,
RT2 denotes a time interval of packet reception at the first sampling frequency of the transmitting end.
Further, the digital signal dynamic synchronization algorithm or the PLL adjusting method in step seven is a hardware adjusting method or a digital signal processing method, the hardware adjusting method is a PLL adjusting method that supports fractional frequency division, the fractional bits are at least 24 bits, the minimum adjustable precision is obtained by a formula 1000000/(16 × 1024 × 1024-1) =0.0596ppm, the digital signal processing method uses a dynamic digital audio synchronization method in software, the adjusted fractional bits of the method are 32 bits, and the method is carried out by a formula 1000000/(4 × 1024 × 1024 × 1024-1) =0.00023283ppm to obtain the minimum adjustable precision, and the minimum adjustable precision is used for adjusting the second sampling frequency of the receiving terminal to send out the signal, so that the phase of the signal received by the second sampling frequency of the receiving terminal is the same as the phase of the signal sent by the first sampling frequency of the sending terminal, and the output audio signal M of the Bluetooth chip of the receiving terminal 2 = output audio signal M of bluetooth chip of transmitting end 1 。
The working principle of the invention is as follows: the invention realizes the transmission of audio signals through Bluetooth by adding a connector with a Bluetooth chip and sending the data of an audio signal generating device (such as a PC) to a third-party Bluetooth device, and in order to ensure that output signals are not lost and not overflowed, the invention generates sampling frequency F through the source of audio 0 And the sampling frequency F generated by the receiver 1 And (6) adjusting.
Firstly, connecting a Bluetooth chip with SPDIF to a PC (personal computer), and then acquiring sampling frequency F generated by audio source by using built-in software of the Bluetooth chip 0 And the sampling frequency F generated by the Bluetooth chip with SPDIF 1 Calculating the sampling frequency F generated by the audio source through the software built in the chip 0 With sampling frequency F generated by a Bluetooth chip with SPDIF 1 The deviation value delta F between the two is obtained by measuring the deviation of the clocks of the master equipment (the source of the audio frequency) for sending the signals and the wireless transmission sending end (the Bluetooth chip with the SPDIF), and the deviation is calculated by measuring the time of receiving a data packet of the master equipment for sending the signals by the wireless transmission sending end, wherein the calculation formula of the deviation is as follows,
in the formula, RXppm1 represents the time deviation of the clock of the signal sending main equipment and the clock of the wireless transmission sending end;
then, by using a method of dynamically adjusting the time interval PT of the signal transmission data, taking +/-0.5 mu s as unit time to adjust the PT, and utilizing the following formula,
RXppm1= ± 0.5 μ S/(PT 1 × M), the formula is further transformed,
M＝±0.5μs/(PT1×PXppm1)，
in the formula, RT represents the time interval of signal transmission data, M represents the quantity of left shift or right shift 0.5us in each PT interval, the decimal part of M is approximately represented by 32 decimal, and the data is adjusted according to a plurality of +/-0.5 mus in each transmission period, so that the data at the transmitting end does not overflow or is interrupted, and F is obtained 0 ＝F 1 。
And then, after the Bluetooth chip with the SPDIF is connected with the Bluetooth chip, sampling frequencies are respectively generated at the transmitting end and the receiving end, then the sampling frequencies of the Bluetooth signal transmitting end and the receiving end are obtained through Bluetooth chip built-in software, a sampling frequency deviation value between the Bluetooth signal transmitting end and the receiving end is calculated, and the deviation is calculated according to wireless transmission, and is caused by the fact that clocks of the wireless transmission transmitting end and the wireless transmission receiving end are asynchronous, so that the problem of the deviation can be solved by solving the problem of asynchronous clock.
Firstly, measuring the time deviation between the clock of the wireless transmission receiving end and the clock of the wireless transmission transmitting end, wherein the deviation is calculated by measuring the time interval PT of receiving the data packet of the wireless transmission receiving end, and according to the following formula RXppm2=1000000 x (PT 2rx-PT 2)/PT 2, in the formula, RXppm2 represents the time deviation between the clock of the second sampling frequency of the receiving end and the first sampling frequency of the transmitting end, RT2rx represents the time interval of receiving the data packet of the receiving end, and RT2 represents the time interval of receiving the data packet of the transmitting end.
After RXppm2 is calculated, two methods can be used for solving the time deviation problem at a wireless transmission receiving end, the first method is a hardware adjusting method, the phase-locked loop PLL with high precision and supporting fractional frequency division is used for adjusting, the minimum adjustable precision is obtained through a formula 1000000/(16 multiplied by 1024-1) =0.0596ppm, the second method is a digital signal processing method, a dynamic digital audio synchronization method is used on software, the minimum adjustable precision is adjusted to be 32 bits, the formula 1000000/(4 multiplied by 1024-1) =0.00023283ppm is used for obtaining the minimum adjustable precision to adjust the sampling frequency of the receiving end to send out signals, the phase of the signals received by the sampling frequency of the receiving end is the same as that of the signals sent by the sending end, the output audio signals of the Bluetooth chip of the receiving end are the same as the output audio signals of the Bluetooth chip of the sending end, and even the output audio signals are completely consistent with the original signals.
After the technical scheme is adopted, the invention has the beneficial effects that:
1. the invention firstly keeps the synchronization of the clock of the sending terminal and the clock of the wireless transmission sending terminal, so that the data of the sending terminal does not overflow or interrupt, thereby the quality of the transmitted signal is higher, the output signal is closer to the original audio signal, and then the invention realizes that the data which is infinitely close to the original signal can be output without any signal adjustment to the signal by the sampling frequency adjusting method and the adjusting method of hardware or software.
2. The method for dynamically adjusting the time interval PT of the signal transmission data and the sampling frequency adjusting method have the characteristics of good applicability, high reliability and the like.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic flow diagram of the present invention.
Fig. 2 is a schematic diagram of the signal transmission structure in the present invention.
Fig. 3 is a schematic diagram illustrating the principle of the cause of the deviation of the digital audio signal in the wireless transmission according to the embodiment of the present invention.
Fig. 4 is a schematic diagram of an application of the embodiment of the present invention.
Detailed Description
Referring to fig. 1 to 4, the technical solution adopted by the present embodiment is: the Bluetooth low-delay transmission method of the audio signal based on the PC-SPDIF comprises the following steps:
connecting a Bluetooth chip with SPDIF to a PC (personal computer), wherein the sampling frequency generated by the source of audio on the PC is F 0 The sampling frequency generated by the Bluetooth chip with the SPDIF is F 1 The source of the audio on the PC is a main device for sending signals, and the Bluetooth chip with the SPDIF is a wireless transmission sending end;
step two, acquiring the sampling frequency F generated by the audio source in the step one by using the built-in software of the Bluetooth chip 0 And the sampling frequency F generated by the Bluetooth chip with SPDIF 1 Calculating by said software the sampling frequency F resulting from the source of the audio 0 Sampling frequency F generated by Bluetooth chip with SPDIF 1 A deviation value Δ F1 therebetween;
step three, according to the delta F1 in the step two, the data is adjusted according to five 0.5 mu s in each transmission period by a method of dynamically adjusting the time interval PT of the signal transmission data, so that the data of the sending end does not overflow or is interrupted, and F is obtained 0 ＝F 1 ；
And step four, the Bluetooth chip with the SPDIF sends a wireless audio signal.
And the deviation value delta F1 in the step two is obtained by measuring the deviation of the clock of the signal sending main equipment and the clock of the wireless transmission sending end in the step one, and the deviation is calculated by measuring the time of the wireless transmission sending end receiving a data packet of the signal sending main equipment.
Furthermore, the deviation calculation formula is as follows,
in the formula, RXppm1 represents the time deviation of the clock of the signal sending main equipment and the wireless transmission sending end;
the method for dynamically adjusting the time interval PT1 of the signal transmission data in the third step is to take 0.5 mus as unit time to adjust PT, and by using the following formula,
RXppm1=0.5 μ s/(PT 1 × M), the formula is further transformed,
M＝0.5μS/(PT1×PXppm)，
in the formula, RT1 represents the time interval of signal transmission data,
m represents the number of 0.5us left-shifted in each PT interval, and the fractional part of M is approximately represented by a decimal number 32.
Step five, wirelessly connecting the Bluetooth chip with the SPDIF with the Bluetooth chip PTK5280 through Bluetooth to form a transmitting end and a receiving end;
step six, acquiring the first sampling frequency F of the transmitting end in the step five by utilizing the built-in software of the Bluetooth chip PTK5280 1 And a second sampling frequency F of the receiving end 2 The output audio signal M of the Bluetooth chip PTK5280 of the transmitting end 1 The output audio signal M of the Bluetooth chip of the receiving end 2 Calculating a first sampling frequency F by said software 1 And a second sampling frequency F 2 A deviation value Δ F2 therebetween;
step seven, according to the delta F2 in the step six, the output audio signal M of the Bluetooth chip at the receiving end is enabled to be obtained through a digital signal dynamic synchronization algorithm or a phase-locked loop PLL (phase-locked loop) regulation 2 = output audio signal M of Bluetooth chip PTK5280 of transmitting end 1 ；
Step eight, outputting the audio.
Further, Δ F2 in the sixth step is a deviation value between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the transmitting end, and the deviation value is calculated by measuring a time interval PT2 of receiving the data packet of the second sampling frequency at the receiving end.
Further, the calculation formula of the deviation value between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the transmitting end is RXppm2=1000000 × (PT 2rx-PT 2)/PT 2,
in the formula (I), the compound is shown in the specification,
RXppm2 represents a time deviation of a clock of the second sampling frequency of the receiving end from the first sampling frequency of the transmitting end,
RT2rx denotes the time interval of packet reception at the second sampling frequency at the receiving end,
RT2 denotes a time interval of packet reception at the first sampling frequency of the transmitting end.
Further, the digital signal dynamic synchronization algorithm or the PLL adjusting method in the seventh step is a hardware adjusting method or a digital signal processing method, the hardware adjusting method is a PLL adjusting method that supports fractional frequency division, the fractional number is 24 bits, and the minimum adjustable precision is obtained by using a formula 1000000/(16 × 1024 × 1024-1) =0.0596ppm, the digital signal processing method uses a dynamic digital audio synchronization method in software, the fractional number adjusting method is 32 bits, the minimum adjustable precision is obtained by using a formula 1000000/(4 × 1024 × 1024 × 1024-1) =0.00023283ppm, the minimum adjustable precision is used for adjusting the second sampling frequency of the receiving end to send a signal, so that the phase of the signal received by the second sampling frequency of the receiving end is the same as the phase of the signal sent by the first sampling frequency of the sending end, and the output audio signal M of the bluetooth chip of the receiving end is output 2 = output audio signal M of Bluetooth chip of transmitting end 1 。
Furthermore, the invention realizes the transmission of audio signals through Bluetooth by adding a connector with a Bluetooth chip and sending the data of an audio signal generating device (such as a PC) to a third-party Bluetooth device, and in order to ensure that output signals are not lost and not overflowed, the invention generates sampling frequency F for audio sources 0 And the sampling frequency F generated by the receiver 1 And (5) adjusting.
Firstly, connecting a Bluetooth chip with SPDIF (short pulse digital amplification) to a PC (personal computer), and then acquiring sampling frequency F generated by audio source by using built-in software of the Bluetooth chip 0 And the sampling frequency F generated by the Bluetooth chip with SPDIF 1 Calculating the sampling frequency F generated by the audio source through the software built in the chip 0 Sampling frequency F generated by Bluetooth chip with SPDIF 1 Deviation value delta F therebetween, fig. 3 is a digital audio signalThe principle of deviation generation in wireless transmission is schematically shown, and t3, t6 and t7 in fig. 3 are the transmission time of each data packet. For low latency transmission, the transmission Time interval of the data Packet must be fixed, labeled PT (Packet Time), and the transmission of the data Packet must be ready before transmission times t3, t6, and t 7. This preparation time t6-t5 is mainly the time of packet compression, and t5-t4 is the delay of the compression algorithm, so the packet sent at t6 is the data from t1 (t 1= t 4-PT) to t 4. The wireless transmission sender sends a data packet between t1 (t 1= t 4-PT) and t4 from t6 to t7 (t 6+ PT), the wireless transmission receiver starts data packet decompression after the wireless transmission receiver stops receiving the data packet between t1 (t 1= t 4-PT) and t4 at t7, t8-t7 time is needed, tb-t4 is delay of a compression algorithm, t5-tb is time for processing asynchronous clock of the signal sending master device and the wireless transmission sender, t5-tb is represented by Msyn, and by analyzing Msyn, if the clock of the signal sending master device is faster than that of the wireless transmission sender, tb is shifted to the left, and delay from the signal sending master device to the wireless transmission sender is increased and accumulated. If the clock of the signal sending master device is slower than that of the wireless transmission sending end, tb is shifted to the right, delay from the signal sending master device to the wireless transmission sending end is reduced and accumulated, and once the clock is shifted to the right to t5, the wireless transmission sending end causes reading of invalid data.
In order to solve the problem of Msyn drift, the deviation is obtained by measuring the deviation of clocks of a main signal sending device (an audio source) and a wireless transmission sending terminal (a Bluetooth chip with SPDIF), and the deviation is calculated by measuring the time of receiving a data packet of the main signal sending device by the wireless transmission sending terminal, wherein the deviation calculation formula is as follows,
in the formula, RXppm1 represents the time deviation of the clock of the transmitting signal main equipment and the wireless transmission transmitting end;
then, by dynamically adjusting the time interval PT of the signal transmission data, 0.5 mus is taken as unit time to adjust PT1, and by using the following formula,
RXppm1=0.5 μ s/(PT 1 × M), the formula is further transformed,
M＝0.5μS/(PT1×PXppm1)，
in the formula, RT1 represents a time interval of signal transmission data, M represents the quantity of left shift 0.5us in each PT interval, the decimal part of M is approximately represented by 32 decimal, data is adjusted according to five 0.5 mus in each transmission period, so that data at a transmitting end does not overflow or data are interrupted, the quality of the transmitted signal is higher after adjustment, and the output signal is closer to the original audio signal.
Then, after a bluetooth chip with SPDIF is connected with a bluetooth chip PTK5280, sampling frequencies are respectively generated at a transmitting end and a receiving end, then the sampling frequencies of the bluetooth signal transmitting end and the receiving end are obtained through built-in software of the bluetooth chip PTK5280, a sampling frequency deviation value between the bluetooth signal transmitting end and the receiving end is calculated, and the sampling frequency deviation value is calculated according to wireless transmission, wherein the deviation is caused by asynchronous clocks of the wireless transmission transmitting end and the wireless transmission receiving end, so that the problem of deviation can be solved by solving the problem of asynchronous clock interval, and in the attached figure 3, as the clocks of the wireless transmission transmitting end and the wireless transmission receiving end cannot be completely consistent, the wireless transmission receiving end needs a certain space (t 9-t 8) to process the problem that the clocks of the wireless transmission transmitting end and the wireless transmission receiving end are not synchronous. In summary, the data of the wireless transmission sender t1 starts to be output at the wireless transmission receiver t 9. Wireless transmission delay = t9-t1= PT + 2+ t6-t5 (time of packet compression) + t5-t4 (delay of compression algorithm) + t8-t7 (time of packet decompression) + t9-t8 (time of processing desynchronization of clocks of wireless transmission sender and wireless transmission receiver), t9-t8 is represented by Tsyn, except Tsyn in wireless transmission delay, because compression algorithm and hardware are basically fixed after being selected in other items, the key point is to solve Tsyn, so that Tsyn is as small and stable as possible, therefore if the clock of wireless transmission receiver is slower than that of wireless transmission sender, t9 will shift right, and wireless transmission delay will increase and accumulate. If the clock of the wireless transmission receiving end is faster than that of the wireless transmission sending end, t9 will shift to the left, the wireless transmission delay will be reduced and accumulated, and once the clock is shifted to the left to t8, the wireless transmission receiving end will cause the reading of invalid data.
Firstly, by measuring the time deviation between the clock of the wireless transmission receiving end and the clock of the wireless transmission transmitting end, the deviation is calculated by measuring the time interval PT of the data packet receiving of the wireless transmission receiving end, according to the following formula, RXppm2=1000000 x (PT 2rx-PT 2)/PT 2, wherein RXppm2 represents the time deviation between the clock of the second sampling frequency of the receiving end and the first sampling frequency of the transmitting end, RT2rx represents the time interval of the data packet receiving of the receiving end, and RT2 represents the time interval of the data packet receiving of the transmitting end.
After RXppm2 is calculated, two methods can be used for solving the time deviation problem at a wireless transmission receiving end, wherein the first method is a hardware adjusting method, the phase-locked loop PLL with high precision and supporting decimal frequency division is used for adjusting, the decimal place is taken as 24 bits, the minimum adjustable precision is obtained through a formula of 1000000/(16 multiplied by 1024-1) =0.0596ppm, the second method is a digital signal processing method, a dynamic digital audio synchronization method is used on software, the decimal place is adjusted to be 32 bits, the minimum adjustable precision is obtained through a formula of 1000000/(4 multiplied by 1024-1) =0.00023283ppm, and finally the minimum adjustable precision is used for adjusting a receiving end sampling frequency to send out a signal, so that the phase of the signal received by the receiving end sampling frequency is the same as that of the signal sent by a sending end, the output audio signal of a Bluetooth chip of the receiving end is the same as that of the output audio signal of the Bluetooth chip of the sending end, even if the output audio signal is consistent with the original signal.
The above description is only for the purpose of illustrating the technical solutions of the present invention and not for the purpose of limiting the same, and other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (7)
1. PC-SPDIF-based audio signalThe Bluetooth low-delay transmission method is characterized by comprising the following steps: connecting a Bluetooth chip with SPDIF to a PC (personal computer), wherein the source sampling frequency of audio on the PC is F 0 And the sampling frequency of the Bluetooth chip with SPDIF is F 1 (ii) a Step two, acquiring the sampling frequency F generated by the audio source in the step one by using the built-in software of the Bluetooth chip 0 And sampling frequency F generated by Bluetooth chip with SPDIF 1 (ii) a Step three, according to the delta F1 in the step two, the data is adjusted according to one or more +/-0.5 mu s in each transmission period by a method of dynamically adjusting the time interval PT of the signal transmission data; step four, the Bluetooth chip with the SPDIF sends a wireless audio signal; step five, the Bluetooth chip with the SPDIF is wirelessly connected with the Bluetooth chip through Bluetooth to form a sending end and a receiving end; step six, acquiring the first sampling frequency F of the transmitting end in the step five by using the Bluetooth chip built-in software 1 And a second sampling frequency F of the receiving end 2 (ii) a Step seven, according to the delta F2 in the step six, a digital signal dynamic synchronization algorithm or a phase-locked loop PLL is adjusted; and step eight, outputting the audio.
2. The bluetooth low latency transmission method of an audio signal based on PC-SPDIF of claim 1, wherein: and the deviation value delta F1 in the step two is obtained by measuring the deviation of the clock of the signal sending main equipment and the clock of the wireless transmission sending end in the step one, and the deviation is calculated by measuring the time of the wireless transmission sending end receiving a data packet of the signal sending main equipment.
3. The method for adjusting the Bluetooth low latency of an audio signal based on a PC-SPDIF connection as claimed in claim 2, wherein: the deviation is calculated by the formula as follows,
in the formula, RXppm1 represents a time offset between a transmission signal master device and a wireless transmission transmitting end clock.
4. The method for adjusting the Bluetooth low latency of an audio signal based on a PC-SPDIF connection as claimed in claim 1, wherein: the method for dynamically adjusting the time interval PT1 of the signal transmission data in the third step is to take +/-0.5 mus as unit time to adjust PT, and by using the following formula,
RXppm1＝±0.5μs/(PT1×M),
the formula is further transformed into that,
M＝±0.5μS/(PT1×PXppm)，
in the formula, RT1 represents the time interval of signal transmission data,
m represents the number of 0.5us left or right shifts in each PT interval, and the fractional part of M is approximately represented by a decimal number 32.
5. The method for bluetooth low latency transmission of PC-SPDIF-based audio signals according to claim 1, wherein: and F2 in the sixth step is a deviation value of the clock of the second sampling frequency of the receiving end and the first sampling frequency of the sending end, and the deviation value is obtained by measuring a time interval PT2 for receiving the data packet of the second sampling frequency of the receiving end.
6. The bluetooth low latency transmission method of an audio signal based on PC-SPDIF of claim 5, wherein: the calculation formula of the deviation value between the clock of the second sampling frequency of the receiving end and the first sampling frequency of the sending end is as follows,
in the formula (I), the compound is shown in the specification,
RXppm2 represents a time deviation of a clock of the second sampling frequency of the receiving end from the first sampling frequency of the transmitting end,
RT2rx denotes the time interval of packet reception at the second sampling frequency at the receiving end,
RT2 represents the time interval of packet reception at the first sampling frequency at the transmitting end.
7. The bluetooth low latency transmission method of an audio signal based on PC-SPDIF of claim 1, wherein: the digital signal dynamic synchronization algorithm or the phase-locked loop PLL adjusting method in the seventh step is a hardware adjusting method or a digital signal processing method, the hardware adjusting method is to use the phase-locked loop PLL supporting fractional frequency division to adjust, the fractional number is at least 24 bits, and the digital signal dynamic synchronization algorithm or the phase-locked loop PLL adjusting method in the seventh step is a hardware adjusting method or a digital signal processing method, the hardware adjusting method is to use the phase-locked loop PLL supporting fractional frequency division to adjust, and the fractional number is at least 24 bits through a formula
1000000/(16 × 1024 × 1024-1) =0.0596ppm to obtain the minimum adjustable precision, the digital signal processing method uses dynamic digital audio synchronization method in software, the adjustment decimal place of the method is 32 bits, the minimum adjustable precision is obtained by formula 1000000/(4 × 1024 × 1024-1) =0.00023283ppm, the minimum adjustable precision is used for adjusting the second sampling frequency of the receiving end to send out signals, the phase of the signals received by the second sampling frequency of the receiving end is the same as the phase of the signals sent by the first sampling frequency of the sending end, so that the output audio signal M of the bluetooth chip of the receiving end is enabled to be the same as the phase of the signals sent by the first sampling frequency of the sending end 2 = output audio signal M of bluetooth chip of transmitting end 1 。
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| CN113473426A (en) * | 2021-06-04 | 2021-10-01 | 深圳市欧思微电子有限公司 | Audio signal Bluetooth low-delay transmission method based on PC-USB connection |
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