CN113473425A - Bluetooth low-delay transmission method for audio signals based on PC-SPDIF connection - Google Patents

Bluetooth low-delay transmission method for audio signals based on PC-SPDIF connection Download PDF

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CN113473425A
CN113473425A CN202110624361.3A CN202110624361A CN113473425A CN 113473425 A CN113473425 A CN 113473425A CN 202110624361 A CN202110624361 A CN 202110624361A CN 113473425 A CN113473425 A CN 113473425A
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sampling frequency
spdif
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李平
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Shenzhen Ousi Microelectronics Co ltd
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
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    • H04W4/80—Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
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Abstract

A low-delay Bluetooth wireless signal transmission method based on PC-SPDIF relates to a wireless signal transmission technology, which comprises connecting a Bluetooth chip A with an SPDIF interface to an SPDIF interface on a PC, then utilizing built-in software of the Bluetooth chip A to obtain the sampling frequency of an audio SPDIF source end, calculating the deviation value between the sampling frequency of the audio SPDIF source and the sampling frequency of the Bluetooth chip A through software, then regulating the data according to a plurality of +/-0.5 mu s in each transmission period through a method of dynamically regulating 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 a 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, and enabling the audio signals of the transmitting end and the receiving end to be the same through a sampling frequency regulation method of the Bluetooth chip B, the output signal is optimized.

Description

Bluetooth low-delay transmission method for audio signals based on PC-SPDIF connection
Technical Field
The invention relates to the technical field of wireless transmission, in particular to a Bluetooth low-delay transmission method for audio signals based on PC-SPDIF connection.
Background
The Bluetooth technology is taken 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 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 extension Bluetooth connector is generally adopted, but the connector is not high generally in quality due to the diversification of equipment interfaces and protocols and the difference of signals.
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.
Chinese patent publication No. CN112256087A discloses a dynamic digital signal synchronization algorithm, and the present invention refers to the relevant contents in the patent.
Disclosure of Invention
The invention aims to provide an audio signal Bluetooth low-delay transmission method based on PC-SPDIF connection, which keeps synchronization with a clock of a wireless transmission sending end through a sending signal main device, so that data of the sending end does not overflow or interrupt, the quality of the transmitted signal 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 through a sampling frequency adjustment method and a hardware or software adjustment method.
In order to achieve the purpose, the invention adopts the following technical scheme: a Bluetooth low-delay transmission method of audio signals based on PC-SPDIF connection 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 F0The sampling frequency generated by the Bluetooth chip with SPDIF is F1The source of the audio frequency on the PC is the main equipment for sending signals, and the Bluetooth chip with SPDIF is used for wireless transmissionA 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 chip0And the sampling frequency F generated by the Bluetooth chip with SPDIF1Calculating, by said software, a sampling frequency F resulting from the source of the audio0With sampling frequency F generated by a Bluetooth chip with SPDIF1The 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 obtained0＝F1；
And step four, the Bluetooth chip with the SPDIF sends a wireless audio signal.
Further, the deviation value Δ F1 in the step two is obtained by measuring a deviation between clocks of the signal sending master device and the wireless transmission sending end in the step one, 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 master device.
Further, the deviation calculation formula is,
Figure BDA0003100456390000021
in the formula, RXppm1 represents the time deviation of the clock of the signal sending master equipment and the wireless transmission sending end;
further, 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 using the following formula,
RXppm1 ═ 0.5 μ s/(PT1 × M), this equation is further transformed,
M＝±0.5μS/(PT1×PXppm)，
in the formula, RT1 represents the time interval of signaling 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 software1And a second sampling frequency F of the receiving end2And the output audio signal M of the Bluetooth chip of the sending end1And the output audio signal M of the Bluetooth chip of the receiving end2Calculating a first sampling frequency F by said software1And a second sampling frequency F2The 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 by adjusting a phase-locked loop (PLL)2Output audio signal M of Bluetooth chip of sending terminal1；
And step eight, outputting the audio.
Further, Δ F2 in the step six is a deviation value between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the sending end, and the deviation value is calculated by measuring a time interval PT2 for receiving the data packets of the second sampling frequency at the receiving end.
Further, the offset between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the transmitting end is calculated as RXppm2 being 1000000 × (PT2rx-PT2)/PT2,
in the formula (I), the compound is shown in the specification,
RXppm2 represents the time offset of the clock at the second sampling frequency at the receiver from the first sampling frequency at the transmitter,
RT2rx represents the time interval for packet reception at the second sampling frequency at the receiving end,
RT2 represents the time interval between packet receptions at the first sampling frequency on the transmit side.
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, and the hardware adjusting method is implemented by usingA PLL for adjusting a PLL supporting fractional frequency division, where the fractional number is at least 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, where the fractional number is 32 bits, and the minimum adjustable precision is obtained by using a formula 1000000/(4 × 1024 × 1024 × 1024-1) ═ 0.00023283ppm, and the minimum adjustable precision is used to adjust a second sampling frequency of a receiving end to emit a signal, so that a phase of the signal received by the second sampling frequency of the receiving end is the same as a phase of the signal transmitted by a first sampling frequency of a transmitting end, and an output audio signal M of a bluetooth chip of the receiving end is enabled to be equal to the phase of the signal transmitted by the first sampling frequency of the transmitting end2Output audio signal M of Bluetooth chip of sending terminal1。
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 audio0And the sampling frequency F generated by the receiver1And (6) adjusting.
Firstly, connecting a Bluetooth chip with SPDIF (SpDIF) to a PC (personal computer), and then acquiring sampling frequency F generated by audio source by using built-in software of the Bluetooth chip0And the sampling frequency F generated by the Bluetooth chip with SPDIF1Calculating the sampling frequency F generated by the audio source through the software built in the chip0With sampling frequency F generated by a Bluetooth chip with SPDIF1The 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,
Figure BDA0003100456390000041
in the formula, RXppm1 represents the time deviation of the clock of the signal sending master equipment and 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, by using the following formula,
RXppm1 ═ 0.5 μ S/(PT1 × MM), this equation 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 obtained0＝F1。
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, by measuring the time deviation between the clock of the wireless transmission receiving terminal and the clock of the wireless transmission transmitting terminal, the deviation is calculated by measuring the time interval PT of receiving the data packet of the wireless transmission receiving terminal, according to the following formula RXppm2 is 1000000 x (PT2rx-PT2)/PT2,
where 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 represents a time interval of packet reception at the receiving end, and RT2 represents a time interval of packet reception at the transmitting end.
After RXppm2 is calculated, two methods can be used to solve the time deviation problem at the receiving end of wireless transmission, the first method is a hardware adjusting method, the phase-locked loop PLL with high precision and supporting fractional frequency division is used to adjust, the formula 1000000/(16 × 1024 × 1024-1) ═ 0.0596ppm is used to obtain the minimum adjustable precision, the second method is a digital signal processing method, the method uses dynamic digital audio synchronization on software, the minimum digital bit of the method is 32 bits, the formula 1000000/(4 × 1024 × 1024 × 1024-1) ═ 0.00023283ppm is used to obtain the minimum adjustable precision, finally, the minimum adjustable precision is used to adjust the receiving end sampling frequency to send out signals, the phase of the signals received by the sampling frequency of the receiving end is the same as the phase of the signals sent by the sending end, so that 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, even if the output audio signal and the original signal are completely identical.
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 end and the clock of the wireless transmission sending end through the sending signal main equipment, so that the data of the sending end does not overflow or the data is not interrupted, thereby the quality of the transmitted signal 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 through the utilized sampling frequency adjusting method and the hardware or software adjusting method.
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: a Bluetooth low-delay transmission method of audio signals based on PC-SPDIF connection 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 F0And the sampling frequency generated by the Bluetooth chip with the SPDIF is F1The 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 chip0And the sampling frequency F generated by the Bluetooth chip with SPDIF1Calculating, by said software, a sampling frequency F resulting from the source of the audio0Sampling frequency F generated by Bluetooth chip with SPDIF1The 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 obtained0＝F1；
And step four, the Bluetooth chip with the SPDIF sends a wireless audio signal.
The deviation value Δ F1 in the step two is obtained by measuring the deviation of the clocks of the signal sending main device and 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 block of data packet of the signal sending main device.
Further, the deviation calculation formula is,
Figure BDA0003100456390000071
in the formula, RXppm1 represents the time deviation of the clock of the signal sending master equipment and the wireless transmission sending end;
the method for dynamically adjusting the time interval PT1 of the signal transmission data in step three is to take 0.5 mus as unit time to adjust PT, and using the following formula,
RXppm1 is 0.5 μ s/(PT1 × M), and the formula is further transformed,
M＝0.5μS/(PT1×PXppm)，
in the formula, RT1 represents the time interval of signaling 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 using built-in software of a Bluetooth chip PTK52801And a second sampling frequency F of the receiving end2The output audio signal M of the Bluetooth chip PTK5280 of the transmitting end1And the output audio signal M of the Bluetooth chip of the receiving end2Calculating a first sampling frequency F by said software1And a second sampling frequency F2The 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 by adjusting a phase-locked loop (PLL)2Output audio signal M of bluetooth chip PTK5280 as transmitting end1；
And step eight, outputting the audio.
Further, Δ F2 in the step six is a deviation value between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the sending end, and the deviation value is calculated by measuring a time interval PT2 for receiving the data packets of the second sampling frequency at the receiving end.
Further, the offset between the clock of the second sampling frequency at the receiving end and the first sampling frequency at the transmitting end is calculated as RXppm2 being 1000000 × (PT2rx-PT2)/PT2,
in the formula (I), the compound is shown in the specification,
RXppm2 represents the time offset of the clock at the second sampling frequency at the receiver from the first sampling frequency at the transmitter,
RT2rx represents the time interval for packet reception at the second sampling frequency at the receiving end,
RT2 represents the time interval between packet receptions at the first sampling frequency on the transmit side.
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 supporting fractional frequency division, the fractional bit is 24 bits, and the minimum adjustable precision is obtained by using a formula 1000000/(16 × 1024 × 1024-1) to 0.0596ppm, the digital signal processing method uses a dynamic digital audio synchronization method in software, the fractional bit of the method is 32 bits, the minimum adjustable precision is obtained by using a formula 1000000/(4 × 1024 × 1024 × 1024-1) to 0.00023283ppm, the minimum adjustable precision is used to adjust the signal sent by the second sampling frequency of the receiving end, 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, make the output audio signal M of the bluetooth chip of the receiving end2Output audio signal M of Bluetooth chip of sending terminal1。
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 sources0And the sampling frequency F generated by the receiver1And (6) adjusting.
First of all the tape is brought to SPDIFThe Bluetooth chip is connected to the PC, and then the sampling frequency F generated by the audio source is obtained by using the built-in software of the Bluetooth chip0And the sampling frequency F generated by the Bluetooth chip with SPDIF1Calculating the sampling frequency F generated by the audio source through the software built in the chip0Sampling frequency F generated by Bluetooth chip with SPDIF1Fig. 3 is a schematic diagram illustrating the principle of deviation generation of the digital audio signal in wireless transmission, 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 (packettime), and the transmission of the data packet must be ready to complete before the transmission times t3, t6, t 7. The 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(t1 ═ t4-PT) to t 4. The wireless transmission sender sends data packets from t6 to t7(t6+ PT) between t1(t 1-t 4-PT) and t4, the wireless transmission receiver starts data packet decompression after stopping receiving the data packets from t1(t 1-t 4-PT) to t4 at t7, t8-t7 time is needed, tb-t4 is the delay of the compression algorithm, t5-tb is the time for processing the clock of the signal sending master device and the clock of the wireless transmission sender are not synchronous, t5-tb is represented by Msyn, and if the clock of the signal sending master device is faster than that of the wireless transmission sender by analyzing Msyn, tb is shifted to the left, the delay from the signal sending master device to the wireless transmission sender device is increased and accumulated. If the clock of the signaling master is slower than the radio transmitter, tb shifts to the right, the delay from the signaling master to the radio transmitter is reduced and accumulated, and the radio transmitter causes invalid data to be read once the clock has shifted to the right at t 5.
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,
Figure BDA0003100456390000091
in the formula, RXppm1 represents the time deviation of the clock of the signal transmitting master device and the wireless transmission transmitting terminal;
then, by dynamically adjusting the time interval PT of the signal transmission data, taking 0.5 μ s as a unit time, PT1 is adjusted, using the following formula,
RXppm1 is 0.5 μ s/(PT1 × M), and the formula is further transformed,
M＝0.5μS(PT1×PXppm1)，
in the formula, RT1 represents the time interval of signal transmission data, M represents the amount 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 μ s in each transmission period, so that the data at the transmitting end does not overflow or data break, 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 an asynchronous clock problem, in the attached figure 3, because 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 (t9-t8) 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. The 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 unsynchronized clocks of wireless transmission sender and wireless transmission receiver), t9-t8 is represented by Tsyn, and except for Tsyn, the wireless transmission delay is basically fixed after selecting compression algorithm and hardware in other items, so the important point is to solve Tsyn, and the Tsyn is as small and stable as possible, so if the clock of the wireless transmission receiver is slower than that of the wireless transmission sender, t9 will shift to the right, and the wireless transmission delay will increase and accumulate. If the clock of the wireless transmission receiver is faster than that of the wireless transmission transmitter, t9 will shift to the left, the wireless transmission delay will be reduced and accumulated, and once the clock shifts to the left at t8, the wireless transmission receiver 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 receiving the data packet of the wireless transmission receiving end, according to the following formula, RXppm2 is 1000000 x (PT2rx-PT2)/PT2, 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 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 to solve the time deviation problem at the receiving end of wireless transmission, the first method is a hardware adjusting method, which uses a phase-locked loop PLL with high precision and supporting decimal frequency division to adjust, the decimal digit is 24 bits, the minimum adjustable precision is obtained by the formula 1000000/(16 × 1024 × 1024-1) ═ 0.0596ppm, the second method is a digital signal processing method, the method uses dynamic digital audio synchronization method on software, the decimal digit of the method is adjusted to 32 bits, the minimum adjustable precision is obtained by the formula 1000000/(4 × 1024 × 1024-1) — 0.00023283ppm, finally the minimum adjustable precision is obtained 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 the phase of the signals sent by the sending end, the output audio signal of the Bluetooth chip at the receiving end is the same as the output audio signal of the Bluetooth chip at 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. A Bluetooth low-delay transmission method of audio signals based on PC-SPDIF connection is characterized by comprising the following steps:
step one, connecting a Bluetooth chip with SPDIF to a PC (personal computer), wherein the source sampling frequency of audio on the PC is F0And the sampling frequency of the Bluetooth chip with SPDIF is F1The 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 chip0And the sampling frequency F generated by the Bluetooth chip with SPDIF1Calculating, by said software, a sampling frequency F resulting from the source of the audio0With sampling frequency F generated by a Bluetooth chip with SPDIF1The 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 the data is interrupted, and F is obtained0＝F1；
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 software1And a second sampling frequency F of the receiving end2And the output audio signal M of the Bluetooth chip of the sending end1And the output audio signal M of the Bluetooth chip of the receiving end2By passingThe software calculates a first sampling frequency F1And a second sampling frequency F2The 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 by adjusting a phase-locked loop (PLL)2Output audio signal M of Bluetooth chip of sending terminal1；
And step eight, outputting the audio.
2. The method for bluetooth low latency transmission of audio signals based on PC-SPDIF connection according to claim 1, wherein: the deviation value Δ F1 in the step two is obtained by measuring the deviation of the clocks of the signal sending main device and 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 block of data packet of the signal sending main device.
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,
Figure FDA0003100456380000021
in the formula, RXppm1 represents the time offset between the master device sending the signal and the clock of the sending end of the wireless transmission.
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 ═ 0.5 μ s/(PT1 × M), this equation is further transformed,
M＝±0.5μS/(PT1×PXppm)，
in the formula, RT1 represents the time interval of signaling 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 audio signals based on PC-SPDIF connection according to claim 1, wherein: and step six, the delta F2 is a deviation value between 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 calculated by measuring a time interval PT2 for receiving the data packets of the second sampling frequency of the receiving end.
6. The method for bluetooth low latency transmission of audio signals based on PC-SPDIF connection according to claim 5, wherein: 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 sending end is,
in the formula (I), the compound is shown in the specification,
RXppm2 represents the time offset of the clock at the second sampling frequency at the receiver from the first sampling frequency at the transmitter,
RT2rx represents the time interval for packet reception at the second sampling frequency at the receiving end,
RT2 represents the time interval between packet receptions at the first sampling frequency on the transmit side.
7. The method for bluetooth low latency transmission of audio signals based on PC-SPDIF connection according to 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, the minimum adjustable precision is obtained, the digital signal processing method uses dynamic digital audio synchronization method in software, the adjustment decimal place of the method is 32, the minimum adjustable precision is obtained by the formula 1000000/(4 × 1024 × 1024 × 1024-1) ═ 0.00023283ppmAdjusting the precision, namely adjusting the second sampling frequency of the receiving end to send a signal by using the minimum adjustable precision to ensure 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, so that an output audio signal M of a Bluetooth chip of the receiving end is2Output audio signal M of Bluetooth chip of sending terminal1。
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Publication number Priority date Publication date Assignee Title
CN115175298A (en) * 2022-07-08 2022-10-11 深圳市欧思微电子有限公司 Audio signal Bluetooth low-delay transmission method based on PC-SPDIF

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115175298A (en) * 2022-07-08 2022-10-11 深圳市欧思微电子有限公司 Audio signal Bluetooth low-delay transmission method based on PC-SPDIF

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