Emergency broadcast message receiving and transmitting method and system

Abstract

The invention provides an emergency broadcast message sending method, which is used for transmitting an instruction frame for instructing a receiving end to wake up based on medium wave amplitude modulation emergency broadcast, and comprises the following steps: framing processing: framing a broadcast audio to be sent to obtain at least one audio frame; fast playing processing: performing fast playing processing on the audio frame to be played to obtain at least one fast playing frame, and controlling the duration of the at least one fast playing frame, so that the sum of the duration of the instruction frame and the duration of the at least one fast playing frame is equal to the duration of the at least one audio frame; instruction frame insertion: inserting an instruction frame in front of or behind at least one fast broadcast frame to form an audio frame containing the instruction frame; and sending the audio frame or the audio frame containing the instruction frame. According to the invention, the sending end can completely send out the emergency broadcast message through fast broadcast processing and instruction frame insertion; and the receiving end receives the emergency broadcast message of the wake-up instruction, and filters the wake-up instruction, so that the noise is filtered, and the emergency broadcast message or the sound source is completely restored and played.

Description

Technical Field

[0001] The present invention relates to the technical field of medium wave amplitude modulation emergency broadcasting, and in particular to a method and system for sending and receiving medium wave amplitude modulation emergency broadcasting messages. Background Art

[0002] Emergency broadcasting is a communication method that broadcasts important information and emergency notifications to the public in emergency situations. It plays a key role in emergency situations such as emergencies, natural disasters, and safety accidents, and is used to promptly transmit alarm information, guide evacuation, and provide important safety tips.

[0003] In the medium wave AM emergency broadcast system, when there is no emergency broadcast message, the emergency broadcast system can play normal program sources; when receiving emergency broadcast messages from emergency broadcast platforms at all levels, the emergency broadcast message is transmitted to the medium wave transmitter through the emergency broadcast adapter and audio switch. When the receiving end is in the shutdown state, the adapter of the sending end first needs to wake up the receiving end, that is, the adapter needs to insert the wake-up command into the emergency broadcast message in time, so that the receiving end can wake up and receive the emergency broadcast message accurately and timely.

[0004] In order to avoid the problem that the receiving end misses the emergency broadcast command or the terminal has not been turned on (in time) when the wake-up command arrives, the sending end adapter often sends some medium wave commands repeatedly or even periodically and continuously. While this command sending method brings many benefits, it also causes some problems or shortcomings:

[0005] On the one hand, when the sending end needs to insert a wake-up command, the normal sound source will be cut off through the audio switching device, and replaced by a short command signal sound of the wake-up command. The normal sound source will not be switched back until the command signal sound ends. This will cause the normal sound source to be incomplete when it is sent by the sending end, and the more frequently the commands are inserted, the more seriously the normal sound source will be damaged.

[0006] On the other hand, because the wake-up command data packet will become an analog low-frequency command signal tone inserted into the normal sound source after FEC encoding and MSK modulation, it actually sounds like a sharp noise, causing the receiving terminal to broadcast noise frequently and continuously, and the normal audio without noise is also incomplete and continuous.

[0007] In summary, the traditional method of sending and receiving medium wave AM emergency broadcast commands will have problems such as incomplete normal audio source, frequent noise from the terminal, and poor broadcast experience. Summary of the invention

[0008] In view of the above-mentioned problems existing in the current medium wave amplitude modulation emergency broadcast insertion instructions, the present invention provides a system and method for sending and receiving emergency broadcast messages.

[0009] The technical solution adopted by the present invention to solve the technical problem is:

[0010] A method for sending an emergency broadcast message, based on medium wave amplitude modulation emergency broadcast transmission, is used to instruct a receiving end to wake up an instruction frame, the method comprising:

[0011] Frame processing, performing real-time frame processing on the broadcast audio to be sent to obtain at least one audio frame;

[0012] Fast play processing, performing fast play processing on the audio frame to be played to obtain at least one fast play frame, and controlling the duration of the at least one fast play frame so that the duration of the instruction frame plus the duration of the at least one fast play frame equals the duration of the at least one audio frame;

[0013] Instruction frame insertion, inserting the instruction frame before or after the at least one fast play frame to form an audio frame including the instruction frame;

[0014] The audio frame or the audio frame including the instruction frame is sent.

[0015] Preferably, the quick broadcast processing may be a single-frame quick broadcast, and the method includes:

[0016] Subtracting the duration of the instruction frame from the duration of an audio frame to be played to obtain the duration of a quick play frame;

[0017] Based on the duration of the fast-play frame, the audio frame is divided into frames, windowed and combined to achieve speed change; wherein during the frame division process, there is a first overlap rate between the frames, and during the frame combination process, there is a second overlap rate between the frames, and the first overlap rate is less than the second overlap rate.

[0018] Preferably, the fast broadcast processing may be multi-frame fast broadcast, and the method includes:

[0019] Determine the number N of audio frames to be played back in multiple frames based on frame delay and sound quality requirements, where N is an integer greater than 1;

[0020] Based on the duration of the instruction frame and the duration of N audio frames, each audio frame is fast-played one by one until all the processing is completed to obtain N fast-play frames, and the duration of the instruction frame plus the duration of the N fast-play frames is equal to the duration of the N audio frames.

[0021] A system for sending emergency broadcast messages, based on medium wave amplitude modulation emergency broadcast transmission, is used to instruct a receiving end to wake up the instruction frame, and the system comprises:

[0022] A frame processing unit, used for performing real-time frame processing on the broadcast audio to be sent to obtain at least one audio frame;

[0023] a fast play processing unit, connected to the frame processing unit, performing fast play processing on the at least one audio frame to be played to obtain at least one fast play frame, and controlling the duration of the fast play frame so that the duration of the instruction frame plus the duration of the at least one fast play frame equals the duration of the at least one audio frame;

[0024] An instruction frame insertion unit, connected to the quick broadcast processing unit, and configured to insert the instruction frame before or after the at least one quick broadcast frame to form an audio frame containing the instruction frame;

[0025] A sending unit is connected to the instruction frame insertion unit and is used to send the audio frame or the audio frame including the instruction frame.

[0026] Preferably, the quick broadcast processing may be a single-frame quick broadcast, and the method includes:

[0027] Subtracting the duration of the instruction frame from the duration of an audio frame to be played to obtain the duration of a quick play frame;

[0028] Based on the duration of the fast-play frame, the audio frame is divided into frames, windowed and combined to achieve speed change; wherein during the frame division process, there is a first overlap rate between the frames, and during the frame combination process, there is a second overlap rate between the frames, wherein the first overlap rate is less than the second overlap rate.

[0029] Preferably, the fast broadcast processing may be multi-frame fast broadcast, and the method includes:

[0030] Determine the number N of audio frames to be played back in multiple frames based on frame delay and sound quality requirements, where N is an integer greater than 1;

[0031] Based on the duration of the instruction frame and the duration of N audio frames, each audio frame is fast-played one by one until all the processing is completed to obtain N fast-play frames, and the duration of the instruction frame plus the duration of the N fast-play frames is equal to the duration of the N audio frames.

[0032] A method for receiving an emergency broadcast message, the method for filtering out instruction frames that instruct a receiving end to perform a wake-up instruction, the method comprising:

[0033] Audio sampling, where the receiving end converts the received audio data into data in PCM format through audio sampling, where the PCM format data includes at least one audio frame;

[0034] Instruction recognition, performing real-time instruction recognition on the at least one audio frame to identify an audio frame containing an instruction frame, wherein the audio frame containing the instruction frame includes an instruction frame and at least one fast play frame;

[0035] Instruction separation, when it is recognized that the audio frame contains an instruction frame, the instruction frame is separated and the at least one fast play frame is retained;

[0036] Slow play restoration, performing slow play processing on the at least one fast play frame so that the duration after slow play is equal to the duration of the at least one audio frame;

[0037] Audio playback, playing the at least one audio frame.

[0038] Preferably, the method for slow playback restoration includes:

[0039] The fast play frame is divided into frames, windowed and combined based on the duration of the audio frame to achieve speed change, so that the duration of a fast play frame is restored to the duration of an audio frame; wherein during the frame division processing, each frame has a first overlap rate, and during the frame combination processing, each frame has a second overlap rate, and the first overlap rate is greater than the second overlap rate.

[0040] A receiving system for emergency broadcast messages, the receiving system is used to filter out instruction frames that instruct a receiving end to perform a wake-up instruction, the system comprising:

[0041] An audio sampling unit, configured to convert the received audio data into PCM format data at the receiving end through audio sampling, wherein the PCM format data includes at least one audio frame;

[0042] A command recognition unit, connected to the audio adopting unit, for performing real-time command recognition on the at least one audio frame, and identifying an audio frame containing a command frame, wherein the audio frame containing the command frame includes a command frame and at least one fast play frame;

[0043] An instruction separation unit, connected to the instruction recognition unit, is used to separate the instruction frame and retain the at least one fast play frame when recognizing that the audio frame contains an instruction frame;

[0044] a slow play restoration unit, connected to the instruction separation unit, for performing slow play processing on the at least one fast play frame so that the duration after the slow play is equal to the duration of the at least one audio frame;

[0045] An audio playing unit is connected to the slow play restoration unit and is used to play the at least one audio frame.

[0046] Preferably, the method for slow playback restoration includes:

[0047] The fast play frame is divided into frames, windowed and combined based on the duration of the audio frame to achieve speed change, so that the duration of a fast play frame is restored to the duration of an audio frame; wherein during the frame division processing, each frame has a first overlap rate, and during the frame combination processing, each frame has a second overlap rate, and the first overlap rate is greater than the second overlap rate.

[0048] Beneficial effects of the present invention: The present application proposes a method and system for sending and receiving emergency broadcast messages. For the sending end, the emergency broadcast audio and command frames are sent out in a timely manner through fast play processing and command frame insertion, so that both the normal sound source and the emergency broadcast message can be sent out completely; for the receiving end, through command separation and slow play processing, when the emergency broadcast terminal receives the emergency broadcast message with the wake-up command added, the wake-up command is filtered out, so that the noise is filtered out, and the normal sound source is completely restored and played. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 An embodiment of the single-frame quick broadcast of the emergency broadcast message of the present invention;

[0050] Figure 2 An embodiment of the multi-frame fast broadcast of the emergency broadcast message of the present invention;

[0051] Figure 3 An embodiment of a system for sending emergency broadcast messages of the present invention;

[0052] Figure 4 This is an embodiment of a system for receiving emergency broadcast messages of the present invention. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0054] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatus.

[0055] In the medium wave AM emergency broadcast system, after the medium wave radio transmitter receives the emergency broadcast message, the emergency broadcast adapter controls the audio switch to output the emergency broadcast program signal, and the radio that is listening to the frequency will receive the emergency broadcast message. In the traditional medium wave AM emergency broadcast system, when the terminal needs to be awakened, the wake-up command is directly added to the emergency broadcast program signal, and then the emergency broadcast adapter controls the audio switch to output the emergency broadcast message with the wake-up command added. Finally, the medium wave emergency broadcast terminal responds to the wake-up command, receives and plays the emergency broadcast message. However, in this way, the wake-up command is also played by the terminal, which is specifically manifested as a short command signal tone, which actually sounds like a sharp noise, which will bring a bad listening experience to the audience.

[0056] Based on this, the present application proposes a command insertion and filtering method for medium wave amplitude modulation emergency broadcasting, so that when the terminal receives an emergency broadcast message with an emergency broadcast terminal response wake-up command added, the wake-up command is filtered out during playback, so that the emergency broadcast message is sent completely and noise is filtered out.

[0057] Embodiment 1

[0058] A method for sending an emergency broadcast message is based on medium wave amplitude modulation emergency broadcast transmission to instruct a receiving end to wake up an instruction frame.

[0059] The method for sending an emergency broadcast message of an embodiment of the present invention is applicable to playing an emergency broadcast message with a wake-up instruction added in a medium wave AM emergency broadcast system. The instruction referred to in this application refers to a medium wave emergency broadcast transmission wake-up instruction, which is an instruction transmitted in a medium wave broadcast channel and used to wake up the terminal. Medium wave emergency broadcast transmission wake-up instructions include types such as start broadcast, stop broadcast, change default locked frequency, certificate authorization and certificate issuance instructions; its content also includes a start flag, instruction length, emergency broadcast message number, target area code, data packet content, data packet time, certificate number and digital signature.

[0060] The command frame in this embodiment refers to the analog waveform generated after the medium wave emergency broadcast transmission wake-up command data packet undergoes data frame encapsulation, FEC encoding, baseband encoding data encapsulation, MSK modulation, and the addition of pre-pilot and post-pilot. In addition, the emergency broadcast audio refers to the audio obtained after the emergency broadcast message is processed by the adapter.

[0061] S110 , frame processing, performing real-time frame processing on the broadcast audio to be sent to obtain at least one audio frame.

[0062] In this step, the emergency broadcast audio or emergency broadcast message to be sent can come from external devices such as the emergency broadcast platform, USB flash drive, etc. Framing processing is to divide the broadcast audio into frames in the time domain and divide it into audio frames of the same size so that the duration of each frame of audio is the same, such as 1 second in length. This is to facilitate fast playback processing and to facilitate the identification of fast playback data by the adapter at the transmitting end. In order to make the transition between different frames after framing smooth, there will be a part of overlap between frames, and different overlap rates will produce different audio playback speeds.

[0063] S120, fast play processing, performing fast play processing on the audio frame to be played to obtain at least one fast play frame, and controlling the duration of the at least one fast play frame so that the duration of the instruction frame plus the duration of the at least one fast play frame is equal to the duration of the at least one audio frame.

[0064] In this step, the fast broadcast processing is to compress each audio frame of the broadcast audio to be processed in the time domain to achieve variable speed processing, so that its length in the time domain is reduced by exactly one instruction frame compared to the original.

[0065] In an optional embodiment of the present invention, the emergency broadcast system will first determine whether it is necessary to insert a command frame indicating a wake-up command. If it is not necessary to insert a command frame, the emergency broadcast audio is directly transmitted through the medium wave transmitter of the broadcast transmitter through the audio switch. When it is determined that a command frame needs to be inserted, the audio frame of the emergency broadcast to be played is determined, and the audio frame to be played is fast-played to shorten the duration of the audio frame to be played so that its duration is less than the original duration, so as to free up a certain amount of playback time for the command frame to occupy, such as Figure 1 More specifically, the duration of the instruction frame plus the duration of the quick play frame obtained after the quick play processing is made equal to the duration of at least one audio frame.

[0066] In an optional embodiment of the present invention, the fast play processing can be a single-frame fast play, and the method includes: subtracting the length of an instruction frame from the length of an audio frame to be played to obtain the length of a fast play frame; based on the length of the fast play frame, the audio frame to be played is divided into frames, windowed and combined to achieve speed change; wherein during the frame division processing, each frame has a first overlap rate, and during the frame combination processing, each frame has a second overlap rate, and the first overlap rate is less than the second overlap rate.

[0067] Specifically, the single-frame fast playback is to perform fast playback processing on only one audio frame. In one embodiment, when the speed is changed, there is a 50% overlap between the frames in the frame processing, and there is a 70% overlap between the frames in the frame combination processing.

[0068] More specifically, the frequency-variable speed algorithm of time domain compression and expansion (TSM) can be used to realize fast broadcast processing. The basic idea is: the audio signal is framed in the time domain, and a 20ms-50ms periodic wave is generally selected as the frame unit. In order to make the transition between different frames after framing smooth, there will be a part of overlap between frames, usually 50% or 75% overlap, and the time difference between the starting positions of two adjacent frames is called frame shift. However, when changing speed, continuous signals will not be directly taken. For example, interval sampling is performed at 2 times the speed, and 0 signals are filled at 0.5 times the speed. This will cause spectrum leakage when the non-continuous signal is spliced. For this reason, after framing, each frame needs to be windowed. There are many types of window functions, among which Hanning window and sinc window functions are more commonly used. After framing, windowing and framing, speed change is realized: if the framing overlaps 50% and the framing overlaps 75%, fast broadcast is achieved, otherwise it is slow broadcast. This is the principle of time domain compression and expansion.

[0069] The audio frame is the smallest unit of the broadcast audio playback algorithm. The receiver can only fast-play or slow-play it after receiving a full frame, and then play it through the speaker. Then, the time consumed by the receiver to receive a frame of broadcast audio is called "frame delay". In other words, when the receiver is receiving the first frame of audio, it cannot be played immediately, because the device does not know whether the frame of audio needs compression and expansion. It can only start playing after receiving the first frame, that is, the start time of the medium wave receiver will have a "delay" relative to the sound source.

[0070] If we want this "frame delay" to be as small as possible, the simplest way is to make the size of an audio frame as small as possible. However, if the duration of a frame is too short, then after removing the duration of the command frame, the duration left for effective audio will be very small, which means that the faster the audio is played, the more serious the distortion of the sound restored after slow playback processing will be.

[0071] Therefore, in order to balance the conflict between "frame delay" and "audio distortion", we can add multiple fast-play frames after a command frame, so that these frames can "share" the duration occupied by the command frame, while not causing the audio frame to become longer. This can ensure a certain audio quality while minimizing the frame delay. This method is called "multi-frame fast play". Figure 2 shown. Figure 2 An embodiment is listed in which two audio frames are fast-played so that the duration of the instruction frame plus the duration of the two processed fast-play frames is equal to the duration of the two audio frames.

[0072] In an optional embodiment of the present invention, the fast play processing can be a multi-frame fast play, and the method includes: determining the number N of audio frames to be fast played in multiple frames based on frame delay and sound quality requirements, where N is an integer greater than 1; based on the duration of the instruction frame and the duration of the N audio frames, performing fast play processing on each audio frame one by one until all the processing is completed to obtain N fast play frames, and the duration of the instruction frame plus the duration of the N fast play frames is equal to the duration of the N audio frames.

[0073] Compared with single-frame fast play, multi-frame fast play can balance the conflict between "frame delay" and "audio distortion", allowing multiple fast play frames to share the time occupied by the command frame without causing the audio frame to become longer. This can ensure a certain audio quality while minimizing frame delay.

[0074] Specifically, during the quick play processing, if we divide the audio to be played into smaller pieces, that is, not much larger than the instruction frame. Then in order to accommodate the instruction frame, the compression and expansion rate of the audio frame is very large. After the audio is compressed by the adapter at the sending end and stretched by the receiving end, the sound quality may be greatly lost. At this time, we can compress the N audio frames to be played, so the time reduced after each audio frame is compressed is 1 / N of the time reduced by a single quick play frame, that is, the compression and expansion rate becomes smaller. Specifically, first determine the compression and expansion rate based on the frame delay and sound quality requirements, and then further determine the number of quick play frames N, where N is an integer greater than 1; secondly, when it is determined that the instruction frame needs to be inserted, each time an audio frame is compressed (to form a quick play frame), N is reduced by 1 until N is 0, indicating that N quick play frames have been compressed; the audio frames after this are sent normally without compression processing.

[0075] S130: Insert an instruction frame before or after at least one quick play frame to form an audio frame including the instruction frame.

[0076] In an optional embodiment of the present invention, the adapter at the transmitting end has an audio frame to be sent at each moment. Therefore, as long as there is a command frame to be sent, the command frame can be merged with the current quick play frame to be sent to form an audio frame containing the wake-up command, and finally the audio frame containing the wake-up command is sent out.

[0077] In an optional embodiment of the present invention, the specific position of the audio frame to be played where the instruction frame is to be inserted can be determined based on the emergency broadcast message, the content of the wake-up instruction, and whether it is a single-frame fast play or a multi-frame fast play. For example: for the start-up instruction, the instruction frame can be inserted at the beginning of the entire audio frame generated by the emergency broadcast message; for the stop-play instruction, the instruction frame can be inserted at the end of the entire audio frame generated by the emergency broadcast message; for other instructions, such as certificate authorization instructions, certificate release instructions, or changing the default locked frequency, etc., can be inserted at any time in the audio frame. In short, the instruction frame may require itself to be sent at any time, whether it is a manual setting of the system or a remote control command of the server. In addition, for single-frame fast play processing, the instruction frame can be inserted in front of or behind a single fast play frame; and for multi-frame fast play, the instruction frame can only be inserted in front of N fast play frames. Because if the instruction frame is added to the back of N fast play frames, it is necessary to wait until all fast play frames are cached before the instruction frame can be found, which will cause a large delay.

[0078] In an optional embodiment of the present invention, the instruction frame is inserted before the quick play frame to be played to form an audio frame containing the wake-up instruction, and finally transmitted to the medium wave emergency broadcast terminal through the audio switch and the medium wave transmitter.

[0079] In the traditional emergency broadcast message sending system, when the sending end needs to insert a wake-up instruction, the normal sound source will be cut off through the audio switching device, and the normal sound source to be played will be directly replaced with the wake-up instruction, and the normal sound source will not be switched back until the command signal tone of the wake-up instruction ends. This will cause the normal sound source to be incomplete when it is sent by the sending end. The sending method of the embodiment of the present application, by framing and fast-playing the audio, can ensure that both the normal sound source and the emergency broadcast message can be sent completely even if the instruction frame is added, thereby maintaining the integrity of the audio.

[0080] Embodiment 2

[0081] Corresponding to the sending method, the present invention also proposes a system for sending emergency broadcast messages, such as Figure 3 As shown, based on the medium wave amplitude modulation emergency broadcast transmission, a command frame for instructing the receiving end to wake up is transmitted, and the system includes:

[0082] A frame processing unit, used for performing real-time frame processing on the broadcast audio to be sent to obtain at least one audio frame;

[0083] A quick play processing unit is connected to the frame processing unit, performs quick play processing on at least one audio frame to be played to obtain at least one quick play frame, and controls the duration of the quick play frame so that the duration of the instruction frame plus the duration of the at least one quick play frame equals the duration of the at least one audio frame;

[0084] An instruction frame insertion unit, connected to the quick broadcast processing unit, is used to insert an instruction frame before or after at least one quick broadcast frame to form an audio frame containing the instruction frame;

[0085] The sending unit is connected to the instruction frame insertion unit and is used to send the audio frame or the audio frame containing the instruction frame.

[0086] The emergency broadcast message sending system of the present application performs frame and quick broadcast processing on the audio through a frame processing unit and a quick broadcast processing unit, so that even if a command frame is added, both the normal audio source and the emergency broadcast message can be sent out completely, thereby maintaining the integrity of the audio.

[0087] In this embodiment, the emergency broadcast message or emergency broadcast audio to be sent can come from external devices such as the emergency broadcast platform, USB flash drive, etc. The frame processing unit is used to frame the emergency broadcast audio in the time domain and divide it into audio frames of the same size so that the duration of each frame of audio is the same, such as 1 second in length. This is to facilitate fast playback processing and to facilitate the identification of fast play data by the adapter at the transmitting end. In order to make the transition between different frames after framing smooth, there will be a partial overlap between frames, and different overlap rates will produce different audio playback speeds.

[0088] In an optional embodiment of the present invention, the emergency broadcast system also includes a judgment unit, which is connected to the frame processing unit and is used to judge whether it is necessary to insert a command frame indicating a wake-up command. When it is not necessary to insert a command frame, the emergency broadcast audio is directly transmitted through the medium wave transmitter of the broadcast transmitter through the audio switch. When it is determined that an instruction frame needs to be inserted, the audio frame of the emergency broadcast to be played is determined, and the audio frame to be played is fast-played, and the duration of the audio frame to be played is shortened so that its duration is less than the original duration, so as to free up a certain amount of playback time for the instruction frame to occupy. More specifically, the duration of the instruction frame plus the duration of the fast-play frame obtained after the fast-play processing is equal to the duration of at least one audio frame.

[0089] In an optional embodiment of the present invention, the quick broadcast processing unit can realize single-frame quick broadcast, and the method includes: subtracting the duration of the instruction frame from the duration of an audio frame to be played to obtain the duration of a quick broadcast frame; performing frame division, windowing and frame combination processing on an audio frame based on the duration of the quick broadcast frame to realize speed change; wherein the frames have a first overlap rate during the frame division processing, and the frames have a second overlap rate during the frame combination processing, wherein the first overlap rate is less than the second overlap rate. For example, the first overlap rate is 50%, and the second overlap rate is 75%.

[0090] Specifically, the fast broadcast processing unit can use the frequency-variable speed algorithm of time domain compression and expansion (TSM) to realize fast broadcast processing. The basic idea is: the audio signal is framed in the time domain, and a 20ms-50ms periodic wave is generally selected as the frame unit. In order to make the transition between different frames after framing smooth, there will be a part of overlap between frames, usually 50% or 75% overlap, and the time difference between the starting positions of two adjacent frames is called frame shift. However, when changing speed, continuous signals will not be directly taken. For example, interval sampling is performed at 2 times the speed, and 0 signals are filled at 0.5 times the speed. This will cause spectrum leakage when the non-continuous signal is spliced. For this reason, after framing, each frame needs to be windowed. There are many types of window functions, among which Hanning window and sinc window functions are more commonly used. After framing, windowing and then framing, speed change is realized: if the framing overlaps 50% and the framing overlaps 75%, slow broadcast is achieved, and vice versa. This is the principle of time domain compression and expansion.

[0091] In an optional embodiment of the present invention, the quick broadcast processing unit can realize multi-frame quick broadcast, and the method includes: determining the number N of audio frames to be fast broadcasted in multiple frames based on frame delay and sound quality requirements, where N is an integer greater than 1; based on the duration of the instruction frame and the duration of the N audio frames, performing quick broadcast processing on each audio frame one by one until all the processing is completed to obtain N quick broadcast frames, and the duration of the instruction frame plus the duration of the N quick broadcast frames is equal to the duration of the N audio frames. Compared with single-frame fast broadcast, multi-frame fast broadcast can balance the conflict between "frame delay" and "audio distortion", allowing multiple quick broadcast frames to share the duration occupied by the instruction frame, while not causing the audio frame to become longer, so that a certain audio quality can be guaranteed while minimizing frame delay.

[0092] In this embodiment, if we need to divide the audio to be played into smaller pieces, that is, not much larger than the instruction frame. Then in order to accommodate the instruction frame, the compression and expansion rate of the audio frame is very large. After the audio is compressed by the sender and stretched by the receiver, the sound quality may be greatly lost. At this time, we can compress all N audio frames, so the time reduced after compression of each audio frame is 1 / N of the time reduced by a single quick play frame, that is, the compression and expansion rate becomes smaller. Specifically, firstly, the number N of quick play frames is determined based on the selection of the compression and expansion rate, where N is an integer greater than 1; secondly, when it is determined that the instruction frame needs to be inserted, each time an audio frame is compressed (to form a quick play frame), N is reduced by 1, until N is 0, indicating that N quick play frames have been compressed; the audio frames thereafter are sent normally without compression.

[0093] Optionally, the adapter at the transmitting end has an audio frame to be sent at each moment. Therefore, as long as there is a command frame to be sent, the command frame can be merged with the current fast broadcast frame to be sent to form an audio frame containing the wake-up command. Finally, the audio frame containing the wake-up command is transmitted through the transmitting unit, and the medium wave emergency broadcast terminal receives and processes it.

[0094] In an optional embodiment of the present invention, the instruction frame insertion unit is connected to the quick broadcast processing unit, and is used to insert an instruction frame before or after at least one quick broadcast frame to form an audio frame containing the instruction frame.

[0095] Specifically, the specific position of the audio frame to be played where the instruction frame is to be inserted can be determined based on the emergency broadcast message, the content of the wake-up instruction, and whether it is a single-frame fast play or a multi-frame fast play. For example: for the start-up instruction, the instruction frame can be inserted at the beginning of the entire audio frame generated by the emergency broadcast message; for the stop-play instruction, the instruction frame can be inserted at the end of the entire audio frame generated by the emergency broadcast message; for other instructions, such as certificate authorization instructions, certificate release instructions, or changing the default locked frequency, they can be inserted at any time in the audio frame. In short, the instruction frame may require itself to be sent at any time, whether it is a manual setting of the system or a remote control command of the server. In addition, for single-frame fast play processing, the instruction frame can be inserted in front of or behind a single fast play frame; and for multi-frame fast play, the instruction frame can only be inserted in front of N fast play frames. Because if the instruction frame is added to the back of N fast play frames, it is necessary to wait until all fast play frames are cached before the instruction frame can be found, which will cause a large delay.

[0096] Embodiment 3

[0097] Corresponding to the transmitting end, the present invention further proposes a method for receiving an emergency broadcast message, the receiving method is used to filter out the instruction frame that instructs the receiving end to perform a wake-up instruction, and the method includes:

[0098] Audio sampling: the receiving end converts the received audio data into PCM format data through audio sampling, and the PCM format data includes at least one audio frame;

[0099] Instruction recognition, performing real-time instruction recognition on at least one audio frame, identifying an audio frame containing an instruction frame, wherein the audio frame containing the instruction frame includes the instruction frame and at least one fast play frame;

[0100] Command separation: when an audio frame is identified to contain a command frame, the command frame is separated and at least one fast play frame is retained;

[0101] Slow playback restoration: slow playback of at least one fast playback frame, so that the duration of the slow playback is equal to the duration of at least one audio frame;

[0102] Audio playback, play at least one audio frame.

[0103] The emergency broadcast message receiving method of the present invention, through command separation and slow broadcast processing, enables the emergency broadcast terminal to receive the emergency broadcast message with the wake-up command added, and the wake-up command is filtered out, so that the noise is filtered out, and the normal sound source is completely restored and played.

[0104] In this embodiment, after the receiving end receives the audio frame containing the wake-up instruction introduced above, audio sampling, instruction recognition, instruction filtering and slow playback restoration are performed respectively, and the wake-up instruction that will generate noise during playback is separated and filtered out, and only the emergency broadcast message, that is, the emergency broadcast audio, is retained. In this way, the emergency broadcast terminal only plays the emergency broadcast message. It should be noted that the filtered instruction frame can be transmitted to the control processing unit of the receiving end for processing to obtain an instruction data packet, and then the start, stop, certificate authorization or release of the receiving end is controlled according to the content of the instruction data packet. That is, the receiving end executes the action of the wake-up instruction, but does not play the inserted wake-up instruction, but only plays the emergency broadcast audio, thereby realizing the function of completely playing the emergency broadcast message, bringing a good listening experience to the audience.

[0105] In this embodiment, although the transmitting end sends audio frames frame by frame, because only the frame header of the fast play frame has a special instruction frame, the receiving end cannot distinguish the audio frame when receiving the normal audio frame. The receiving end needs to calculate and determine whether the instruction frame is received for each frame of data received. Specifically, the receiving end obtains audio data in PCM format through audio sampling, and then uses the instruction recognition method, which specifically includes digital filtering, coherent calculation, peak detection, pre-pilot detection, MSK demodulation, LDPC decoding and other steps to identify whether the audio data in PCM format contains instruction frames: when it is identified that no instruction frame is included, the audio frame is played directly; when it is identified that an instruction frame is included, the receiving end can determine that the data after the instruction frame is the beginning of the audio frame, and it is one or more fast play frames, then it is necessary to perform frame caching, instruction separation and slow play restoration processing on the one or more fast play frames, and finally play the audio frame with the instruction frame filtered out.

[0106] In an optional embodiment of the present invention, the method for slow play restoration includes: framing, windowing and merging fast play frames based on the duration of audio frames to achieve speed change so that the duration of a fast play frame is restored to the duration of an audio frame; wherein there is a first overlap rate between the frames during the frame division processing, and there is a second overlap rate between the frames during the frame merging processing, and the first overlap rate is greater than the second overlap rate.

[0107] In this embodiment, the method of slow play restoration is similar to the method of fast play processing, except that the overlapping rates are different when performing frame division and frame combination processing. When slow play restoration is performed, the first overlapping rate can be 75% when performing frame division processing, and the second overlapping rate can be 50% when performing frame combination processing, thereby achieving slow play restoration.

[0108] In an optional embodiment of the present invention, when slow play is restored, the number N of audio frames contained in the fast play frame is analyzed based on the duration of the fast play frame and the duration of the audio frame. When N=1, it is a single-frame slow play restoration; when N is greater than 1, it is a multi-frame restoration. The method for single-frame restoration is the same as described above. For multi-frame restoration, after the analysis obtains the number N of multi-frame restorations, each fast play frame is restored one by one until all are processed and N audio frames are obtained, so that the duration of each processed audio frame is equal, and the total duration is equal to the duration of N audio frames that do not contain instruction frames.

[0109] Embodiment 4

[0110] The present invention also provides a Figure 4 The receiving system of the emergency broadcast message shown is used to filter out the instruction frame that instructs the receiving end to perform a wake-up instruction, and the system includes:

[0111] An audio sampling unit, configured to convert the received audio data into PCM format data at the receiving end through audio sampling, wherein the PCM format data includes at least one audio frame;

[0112] The instruction recognition unit is connected to the audio adopting unit and is used to perform real-time instruction recognition on at least one audio frame and recognize an audio frame containing an instruction frame, wherein the audio frame containing the instruction frame includes the instruction frame and at least one fast play frame;

[0113] An instruction separation unit, connected to the instruction recognition unit, is used to separate the instruction frame and retain the at least one fast play frame when recognizing that the audio frame contains the instruction frame;

[0114] A slow play restoration unit, connected to the instruction separation unit, for performing slow play processing on at least one fast play frame, so that the duration after slow play is equal to the duration of at least one audio frame;

[0115] The audio playing unit is connected to the slow play restoration unit and is used to play at least one audio frame.

[0116] The emergency broadcast message receiving system of the present invention processes the command separation unit and the slow broadcast restoration unit so that when the emergency broadcast terminal receives the emergency broadcast message with the wake-up command, the wake-up command is filtered out, so that the noise is filtered out and the normal sound source is completely restored and played.

[0117] In this embodiment, after the receiving end receives the audio frame containing the wake-up instruction introduced above, audio sampling, instruction recognition, instruction filtering and slow play restoration are performed respectively, and the wake-up instruction that will generate noise during playback is separated and filtered out, and only the emergency broadcast message, that is, the emergency broadcast audio, is retained. In this way, the emergency broadcast terminal only plays the emergency broadcast message.

[0118] In this embodiment, although the transmitting end sends audio frames frame by frame, because only the frame header of the fast play frame has a special instruction frame, the receiving end cannot distinguish the audio frame when receiving the normal audio frame. The receiving end needs to calculate and determine whether the instruction frame is received for each frame of data received. Specifically, the receiving end obtains audio data in PCM format through audio sampling, and then uses the instruction recognition method, which specifically includes digital filtering, coherent calculation, peak detection, pre-pilot detection, MSK demodulation, LDPC decoding and other steps to identify whether the audio data in PCM format contains instruction frames: when it is identified that no instruction frame is included, the audio frame is played directly; when it is identified that an instruction frame is included, the receiving end can determine that the data after the instruction frame is the beginning of the audio frame, and it is one or more fast play frames, then it is necessary to perform frame caching, instruction separation and slow play restoration processing on the one or more fast play frames, and finally play the audio frame with the instruction frame filtered out.

[0119] In an optional embodiment of the present invention, the method for slow play restoration includes: framing, windowing and merging fast play frames based on the duration of audio frames to achieve speed change so that the duration of a fast play frame is restored to the duration of an audio frame; wherein there is a first overlap rate between the frames during the frame division processing, and there is a second overlap rate between the frames during the frame merging processing, and the first overlap rate is greater than the second overlap rate.

[0120] In this embodiment, the method of slow play restoration is similar to the method of fast play processing, except that the overlapping rates are different when performing frame division and frame combination processing. When slow play restoration is performed, the first overlapping rate can be 75% when performing frame division processing, and the second overlapping rate can be 50% when performing frame combination processing, thereby achieving slow play restoration.

[0121] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for sending an emergency broadcast message, characterized in that: Based on medium wave amplitude modulation emergency broadcast transmission, a command frame for instructing a receiving end to wake up is transmitted, and the method includes: Frame processing, performing real-time frame processing on the broadcast audio to be sent to obtain at least one audio frame; Fast play processing, performing fast play processing on the audio frame to be played to obtain at least one fast play frame, and controlling the duration of the at least one fast play frame so that the duration of the instruction frame plus the duration of the at least one fast play frame equals the duration of the at least one audio frame; Instruction frame insertion, inserting the instruction frame before or after the at least one fast play frame to form an audio frame including the instruction frame; The audio frame or the audio frame including the instruction frame is sent.

2. The method for sending an emergency broadcast message according to claim 1, characterized in that: The quick broadcast processing may be a single-frame quick broadcast, and the method includes: Subtracting the duration of the instruction frame from the duration of an audio frame to be played to obtain the duration of a quick play frame; Based on the duration of the fast-play frame, the audio frame is divided into frames, windowed and combined to achieve speed change; wherein during the frame division process, there is a first overlap rate between the frames, and during the frame combination process, there is a second overlap rate between the frames, and the first overlap rate is less than the second overlap rate.

3. The method for sending an emergency broadcast message according to claim 1, characterized in that: The fast broadcast processing may be multi-frame fast broadcast, and the method includes: Determine the number N of audio frames to be played back in multiple frames based on frame delay and sound quality requirements, where N is an integer greater than 1; Based on the duration of the instruction frame and the duration of N audio frames, each audio frame is fast-played one by one until all the processing is completed to obtain N fast-play frames, and the duration of the instruction frame plus the duration of the N fast-play frames is equal to the duration of the N audio frames.

4. A system for sending emergency broadcast messages, characterized in that: Based on medium wave amplitude modulation emergency broadcast transmission, a command frame for instructing a receiving end to wake up is transmitted, and the system includes: A frame processing unit, used for performing real-time frame processing on the broadcast audio to be sent to obtain at least one audio frame; a fast play processing unit, connected to the frame processing unit, performing fast play processing on the at least one audio frame to be played to obtain at least one fast play frame, and controlling the duration of the fast play frame so that the duration of the instruction frame plus the duration of the at least one fast play frame equals the duration of the at least one audio frame; An instruction frame insertion unit, connected to the quick broadcast processing unit, and configured to insert the instruction frame before or after the at least one quick broadcast frame to form an audio frame containing the instruction frame; A sending unit is connected to the instruction frame insertion unit and is used to send the audio frame or the audio frame including the instruction frame.

5. The system for sending emergency broadcast messages according to claim 4, characterized in that: The quick broadcast processing may be a single-frame quick broadcast, and the method includes: Subtracting the duration of the instruction frame from the duration of an audio frame to be played to obtain the duration of a quick play frame; Based on the duration of the fast-play frame, the audio frame is divided into frames, windowed and combined to achieve speed change; wherein during the frame division process, there is a first overlap rate between the frames, and during the frame combination process, there is a second overlap rate between the frames, wherein the first overlap rate is less than the second overlap rate.

6. The system for sending emergency broadcast messages according to claim 4, characterized in that: The fast broadcast processing may be multi-frame fast broadcast, and the method includes: Determine the number N of audio frames to be played back in multiple frames based on frame delay and sound quality requirements, where N is an integer greater than 1; Based on the duration of the instruction frame and the duration of N audio frames, each audio frame is fast-played one by one until all the processing is completed to obtain N fast-play frames, and the duration of the instruction frame plus the duration of the N fast-play frames is equal to the duration of the N audio frames.

7. A method for receiving emergency broadcast messages, characterized in that: The receiving method is used to filter out the instruction frame that instructs the receiving end to perform a wake-up instruction, and the method includes: Audio sampling, where the receiving end converts the received audio data into data in PCM format through audio sampling, where the PCM format data includes at least one audio frame; Instruction recognition, performing real-time instruction recognition on the at least one audio frame to identify an audio frame containing an instruction frame, wherein the audio frame containing the instruction frame includes an instruction frame and at least one fast play frame; Instruction separation, when it is recognized that the audio frame contains an instruction frame, the instruction frame is separated and the at least one fast play frame is retained; Slow play restoration, performing slow play processing on the at least one fast play frame so that the duration after slow play is equal to the duration of the at least one audio frame; Audio playback, playing the at least one audio frame.

8. The method for receiving emergency broadcast messages according to claim 7, characterized in that: The methods of slow playback restoration include: The fast play frame is divided into frames, windowed and combined based on the duration of the audio frame to achieve speed change, so that the duration of a fast play frame is restored to the duration of an audio frame; wherein during the frame division processing, each frame has a first overlap rate, and during the frame combination processing, each frame has a second overlap rate, and the first overlap rate is greater than the second overlap rate.

9. A system for receiving emergency broadcast messages, characterized in that: The receiving system is used to filter out the instruction frame that instructs the receiving end to perform a wake-up instruction, and the system includes: An audio sampling unit, configured to convert the received audio data into PCM format data at the receiving end through audio sampling, wherein the PCM format data includes at least one audio frame; A command recognition unit, connected to the audio adopting unit, for performing real-time command recognition on the at least one audio frame, and identifying an audio frame containing a command frame, wherein the audio frame containing the command frame includes a command frame and at least one fast play frame; An instruction separation unit, connected to the instruction recognition unit, is used to separate the instruction frame and retain the at least one fast play frame when recognizing that the audio frame contains an instruction frame; a slow play restoration unit, connected to the instruction separation unit, for performing slow play processing on the at least one fast play frame so that the duration after the slow play is equal to the duration of the at least one audio frame; An audio playing unit is connected to the slow play restoration unit and is used to play the at least one audio frame.

10. The emergency broadcast message receiving system according to claim 9, characterized in that: The methods of slow playback restoration include: The fast play frame is divided into frames, windowed and combined based on the duration of the audio frame to achieve speed change, so that the duration of a fast play frame is restored to the duration of an audio frame; wherein during the frame division processing, each frame has a first overlap rate, and during the frame combination processing, each frame has a second overlap rate, and the first overlap rate is greater than the second overlap rate.

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