Multichannel recording arrangement and method

Abstract

The invention concerns a multichannel recording arrangement, comprising two mobile recording devices (M1, M2, M3), each configured to record a respective sound signals using a set of recording parameters. The recording devices are set up in a master slave configuration to receive the recorded sound signal by one recording device (M2) and generate a multichannel sound signal comprising the received first sound signal and a recorded second sound signals therefrom. A UE comprising a radio (15) is configured to receive the multichannel sound signal and stores the received multichannel sound signal. The UE is further configured to establish a wireless transmission using a second communication protocol to a remote network to transmit the stored received multichannel sound signal. One of the mobile recording devices is configured to transmit a synchronization signal to the other one in order to adjust its set of recording parameters in response to the synchronization signal.

Description

[0001] MULTICHANNEL RECORDING ARRANGEMENT AND METHOD

[0002] The present application claims priority from DK application PA202470303 dated December 16 , 2024 , the disclosure of which is incorporated herein by reference in its entirety . The present invention concerns a multichannel recording arrangement and a method for recording and transmitting a multichannel recording .

[0003] BACKGROUND

[0004] Content creators and consumers have increasing demands on the recorded content , not only related to video quality, but also audio quality . Often such recordings include sounds from various sound sources , which are to be recorded, processed and then played back on a variety of different devices . The term "sound signal" in such cases may represent and is not limited to speech, music, environmental sound, echo , and all kinds of noises . Particularly in podcasts or during interviews , the content creator usually provides two or more microphones to his or her interview partners for recording . Such a plurality of microphones enables better quality during the recording process , although postprocessing may be tedious and can take a long time .

[0005] In addition, preparation for such recording requires effort , as the required equipment must be set up, properly calibrated and adj usted, and so forth . Moreover , often recordings are not taking place in a studio with a controlled environment , but at some other location, outside , etc . As a result , content creators have begun using their mobile equipment , like mobile phones , for such recordings . The benefit of mobiles or generally mobile equipment lies in the fact that they are small , readily available and easier to set up . The downside is the lack of high-quality recordings , as the microphones in devices are usually of lower quality than studio equipment .

[0006] In addition, a single mobile device owned by a content creator suffers from basically the same issue as a studio recording, which only comprises a single microphone ; the speech of each person is recorded by said single microphone with various levels of quality . One now may use two or more mobile devices recording the speech and sound signals independently of each other and then cut the speech or the sound as desired in post . But such a procedure usually requires a long and tedious post-processing with additional effort to ensure equal sound quality .

[0007] In summary, the increasing market for podcast and video or audio content creators has a need for a mobile and flexible solution that is easy to set up and to be handled in a variety of situations . Such solution should simplify post-processing .

[0008] SUMMARY OF THE INVENTION

[0009] This and other obj ects are addressed by the subj ect matter of the independent claims . Features and further aspects of the proposed principles are outlined in the dependent claims .

[0010] One important aspect when dealing with a plurality of recorded sound signals in a sound environment lies in the synchronization of the recorded signals . The expression sound environment refers to a plurality of sound sources in a common environment with, in which two or more microphones are placed and subsequently record signals occurring in such a common environment . Hence , the two or more microphones will record signals coming from the same sound source within such an environment . However , due to different spatial locations , the recorded signals will be delayed with respect to each other, and the two or more microphones may also record reflection, cross-talk and the like .

[0011] The inventors have found a simple solution that provides a multichannel recording arrangement with a set of mobile recording devices that record two or more sound signals in a time synchronized manner . The mobile recording devices use a wireless transmission and thus are suitable for various applications and scenarios outside a professional sound studio . They are rechargeable , enabling a several hours-long recording session before being required to recharge .

[0012] The combined recorded sound signal can then be transferred to a mobile device like a phone , for example , for further transmission to a cloud or otherwise processed . Such a solution offers a highly flexible solution, as the mobile recording devices work independent of a mobile phone , although such is used for further processing and transmission . Each mobile recording device can be associated with a sound source and placed close to it , for example a speaker, enabling a high recording quality for each sound source .

[0013] In some aspects , the inventors propose a multichannel recording arrangement . The arrangement comprises at least one first mobile recording device , wherein said first mobile recording device is configured to record a first sound signal using a first set of recording parameters and comprises a radio configured to transmit the recorded first sound signal using a first packet-oriented transmission protocol .

[0014] The arrangement further comprises a second mobile recording device , said second mobile device configured to record a second sound signal using a set of second recording parameters . The first and second sound signals may originate from a common sound environment and can comprise one or more spatially separated sound sources . In some aspects , the first sound signal is associated with a first sound source , while the second sound signal is associated with a second sound source .

[0015] The second mobile recording device further comprises at least one radio configured to receive the transmitted recorded first sound signal . The at least one radio is also configured to transmit a multichannel sound signal comprising the received at least a part of the first sound signal and the recorded second sound signals using a second packet- oriented transmission protocol .

[0016] The arrangement further comprises a UE having a radio . Said radio is configured to receive the multichannel sound signal . The UE also comprises a memory configured to store at least a portion of the received multichannel sound signal . Finally, the UE is further configured to establish a wireless transmission using a second communication protocol to a remote network to transmit the stored received multichannel sound signal . In accordance with the proposed principle , one of the at least one first and the second mobile recording devices is configured to transmit a synchronization signal to the other one of the at least one first and the second mobile recording devices . The mobile recording device receiving such synchronization signal is configured to adj ust its set of recording parameters in response to the synchronization signal .

[0017] In current mobile telecommunication systems and standards like UMTS , 5G, WLAN, 802 . 11X, LTE , GSM and others the expression UE user equipment corresponds to a device used directly by an end-user to communicate with a further node of the communication network . Such UE may include , but is not limited to , a hand-held telephone , a mobile phone , tablet , a laptop computer equipped with a mobile broadband adapter , a camera , in particular a video camera, or any other device capable of communicating with base stations Node B / eNodeB as for example , specified in the ETSI 125 / 136-series and 3GPP 25 / 36-series of specifications or any other kind of network node .

[0018] The proposed arrangement provides a synchronization between the mobile recording devices independent of a mobile device . It has been observed that due to the huge variety of UEs available on the market , the communication between the UE and the mobile recording devices may not be sufficient to synchronize or adj ust its set of recording parameters in order to record the sound signals in the sound environment synchronously . Consequently, the inventors propose a master-slave configuration of mobile recording devices independent of the UE , whereas the UE serves as memory receiving the recorded and timely synchronized multichannel sound signal .

[0019] The proposed arrangement is not limited to two mobile recording devices . Rather, a plurality of mobile recording devices is able to synchronize their recording and thus transmit synchronized sound signals to a master of the mobile recording devices . For the purpose of this application, the first and second sets of parameters can include the same parameters , although some values of such parameters may change over time . In some particular aspects , the set of parameters may include a sampling rate or frequency, that is , the frequency of a signal used to sample the sound . This sampling rate may vary over time , as explained herein, and the arrangement of the proposed principle is set up to reduce such variation and to ensure that it does not increase beyond a given threshold during the recording time . In some other aspects , the inventors propose a multichannel recording arrangement with at least one first mobile recording device , wherein said first mobile recording device is configured to record a first sound signal using a first set of parameters . A second mobile recording is configured to record a second sound signal using a set of second recording parameters . The first and second sound signals may originate from a common sound environment and can comprise one or more spatially separated sound sources . In some aspects , the first sound signal is associated with a first sound source , while the second sound signal is associated with a second sound source .

[0020] In accordance with such aspects , the at least one second recording device further comprises a radio configured to transmit the recorded second audio signal using either the first packet-oriented transmission protocol and / or a second packet-oriented transmission protocol . One of the at least one first and the second mobile recording devices is now configured to transmit a synchronization signal to the other one of the at least one first and the second mobile recording devices . The mobile recording device receiving such synchronization signal is configured to adj ust its set of recording parameters in response to the synchronization signal . The synchronization signal may be a data packet containing synchronization information . Such information may include , for example , the amount of clock cycles being passed since a specific time , for example , since the time the recording started or the time since the previous synchronization signal ( the data packet ) has been transmitted .

[0021] Finally, in accordance with the proposed principle of such aspects , the arrangement comprises a UE having a radio configured to receive the transmitted first and second sound signals using the first and / or the second packet-oriented transmission protocol . The UE also comprises a memory configured to store at least a portion of the received sound signals . Optionally, the UE may comprise a processor configured to combine the received first and second sound signals to a multichannel sound signal . Finally, the UE is further configured to establish a wireless transmission using a second communication protocol to a remote network to transmit the stored received multichannel sound signal .

[0022] In a further aspect of such concept , the first and second sound transmitted by the first and second mobile recording devices may comprise the recorded first and / second sound signals as well as synchronization information embedded in the transmitted signals . The UE or its processor is configured to evaluate the synchronization information embedded therein to generate a timely synchronized multichannel sound signal .

[0023] Some aspects concern the set of parameters to be adj usted on one of the first and / or second mobile recording devices . It has been observed that a synchronization of the frame rate of the recorded signals in the range of a few milliseconds or even less in the microsecond range is necessary to provide a basis for further processing the sound signals . Hence , the frequency of a clock signal used for generating a sample rate for recording the sound signals may be adj usted in some aspects . Alternatively or additionally, a multiplication factor for the frequency of a clock signal used for generating a sample rate for recording the sound signal may be adj usted .

[0024] In some aspects , a sample rate for recording the sound signals based on a clock signal may be adj usted . Furthermore , it is possible in some aspects to adj ust the delay of a clock signal used for generating a sample rate for the recording of the sound signal . The above-mentioned adj ustment affects the sampling rate of the sound signal , such that the recordings and particularly the frame is synchronized . Recorded sound signals synchronized using the proposed approach can contain correlated portions e . g . same parts of a common sound part but delayed due to the spatial separation of the mobile recording devices .

[0025] Correlated sound signals with such synchronization can be processed further for different purposes , like but not limited to denoising of sound portions associated with a sound source , separation of sound portions belonging to different sound sources , determination of position of sound sources in the sound environment , enhancing of sound quality, generating audio obj ects and the like .

[0026] In some aspects , the synchronization signal is transmitted between consecutive packages comprising the recorded first sound signal . Such an approach may be useful , if the packet-oriented first and / or second transmissions do not provide a time synchronization suitable for the above aspects on their own . Furthermore , transmission of the synchronization signal can be independent of transmission of data packet offering a more flexible solution in some situations .

[0027] In accordance with a transmission between consecutive packets , the synchronization signal can be transmitted after a dedicated amount of time after for example , an event corresponding to receiving a packet containing a portion of the first sound signal . The synchronization signal may also be transmitted after an event corresponding to sending or having sent a packet containing a portion of the first sound signal . Alternatively, the synchronization signal can be transmitted after an event corresponding to sending or having sent a packet containing a portion of the multichannel sound signal .

[0028] In some further aspects , the synchronization signal may comprise a value corresponding to a time value derived from a reference clock used in the one of the first and second mobile recording devices to set a sample rate for recording the sound signal . In these aspects , each of the mobile recording devices may comprise one or more reference clocks . At least one of those clocks is adj ustable , i . e . either adj usting phase , frequency or a combination thereof . The adj ustable reference clock may be used to generate the sampling rate during recording of the sound signals . By using the synchronization signals , one may ensure the same sampling rate for the mobile recording devices .

[0029] In a master and slave configuration, one of the mobile recording devices may use its reference clock as the master clock or derive the synchronization signal therefrom . In some aspects , the second mobile recording device is configured to generate and transmit the synchronisation signal to the first mobile recording device . This may be suitable , as the second mobile recording device is also the device receiving the first recorded sound signal . The second mobile recording device may be configured to generate and transmit the respective synchronization signal after receiving a dedicated number of packages from the first mobile recording device .

[0030] Some aspects concern the fact that radio communication may not always be flawless but can be interrupted or deteriorate . To avoid data loss , it is possible in some aspects that the first mobile recording device comprises a buffer memory to store at least a portion of the first recorded sound signal prior to its transmission . In some aspects , the mobile recording devices may communicate with each other to determine the channel and signal quality prior to transmission of packages . They may also communicate periodically to adj ust such evaluation or align on data rate , packet length and other parameters . Both mobile recording devices may utilize built-in functionality provided by the first communication protocol . In a further embodiment , the synchronization signal may also be generated by the respective mobile recording device utilizing a built-in functionality provided by the first communication protocol .

[0031] A further aspect concerns different implementations of the second mobile recording device . The second mobile recording device further comprises , in some aspects , a buffer memory, said buffer memory configured to store at least a part of the first sound signal . Further and / or additionally, the second mobile recording device can also comprise a memory, said memory configured to store at least a part of the second sound signal . After receiving the first recorded sound signal from the first mobile recording device , a multichannel sound signal may be created therefrom . Hence , the second mobile recording device may comprise a processor configured to obtain the first and second recorded sound signals and generate the multichannel sound signal therefrom .

[0032] Some aspects concern the data and more particularly, the recording and storage of the sound signals . The sound signal may be recorded using a nominal sampling rate of 44 . 1 kHz or 48 kHz , although other nominal sampling rates are usable . However , recorded sound signals can become quite large . Hence , some aspects propose a lossless compression of the recorded sound signal prior to transmitting them. In some cases , at least one of the first and second mobile recording devices is configured to generate packets containing portions of the respective recorded sound signal in a lossless compression format like for example , but not limited to FLAG, ALAC, APE , OFR, WV, TTA, MPEG-4 ALS or WMAL . As an alternative , one may use a lossy format while maintaining a high sound quality . Suitable lossy compression formats include but are not limited to LC3 , LC3+ , LHDC , USAC , Opus , MPEG-H and the like .

[0033] The first and second packet-oriented transmission protocols may be based on the same core protocol , in particular the Bluetooth protocol . In this regard, the first packet-oriented transmission protocol may comprise a Bluetooth derivate or add-on like the Bluetooth Low Energy Audio , LE Audio protocol . The second packet-oriented transmission protocol comprises one of LE Audio , Bluetooth standard protocol , WiFi , or any other packet-oriented data protocol , for example .

[0034] Some further aspects concern implementations and further aspects of the UE . In some aspects , the UE comprises one or more spatially separated microphones configured to record at least one third sound signal . In other words , the UE can be used in addition to the first and second mobile devices to record a third sound signal originating from the same sound environment as the recorded first and second sound signals . The UE can be configured to generate a combined multichannel sound signal from the at least one third recorded sound signal and at least the portion of the received multichannel sound signal . The UE may also be configured to transmit the combined multichannel sound signal to the remote network . For example , such an application enables the UE to record noise or background sound signals suitable for creating ambient sound, while the first and second mobile recording devices may record sound signals coming from dedicated sound sources like speakers .

[0035] In some aspects , the radio configured to receive the multichannel sound signal is a device separatable from the UE . The device can be attached to the USB and subsequently controlled by it , for example using a USB port available at the UE .

[0036] The UE can also be used to process or preprocess the signal for example , depending on the computation power available . In some aspects , the UE comprises a processor configured to generate a spatial audio signal from the received multichannel sound signal . Alternatively or additionally, the processor is configured to enhance , in particular denoise the first and second recorded sound signals contained in the multichannel sound signal .

[0037] Some aspects concern a method for recording a multichannel sound signal . The proposed method comprises the steps of recording by a first mobile recording device , a first sound signal using a first set of recording parameters and, by a second mobile recording device , a second sound signal using a second set of recording parameters . The first and second setoff recording parameters can be the same and may include the clock frequency or the frequency of a signal referred to as a sampling frequency or sampling rate used to record the signal . The first and second sound signals may originate from a common sound environment and can comprise one or more spatially separated sound sources . In some aspects , the first sound signal is associated with a first sound source , while the second sound signal is associated with a second sound source .

[0038] In accordance with the proposed principle , the recorded first sound signal is transmitted to the second mobile recording device by the first mobile recording device using a first packet-oriented transmission protocol . A multichannel sound signal comprising the received first sound signal and the recorded second sound signals may be generated by the second mobile recording device . The multichannel sound signal is transmitted to a UE using a second packet-oriented transmission protocol . In this regard, the second packet-oriented transmission protocol can include a wired protocol or a wireless transmission protocol . In some aspects , instead of a packet-oriented transmission protocol , a USB connection between the second mobile recording device and the UE is used . In accordance with the proposed principle , a data packet containing synchronization information is transmitted by one of the UE , first and second mobile recording devices . The synchronization information may be related to clock frequency and / or contain information about clock cycles that have been passed since a specific point in time , for example , since the last data packet containing such information was transmitted .

[0039] The data packet containing the synchronization information is received and used to adj ust , in response to the synchronization information, its set of recording parameters . This approach enables , for example , a synchronous sampling rate between the respective recording devices .

[0040] In some aspects , the synchronization information is stored until at least a data packet with subsequent synchronization information is obtained . It may then be used to derive a deviation of a clock signal from a reference clock signal , which is encoded in the obtained synchronization information . The reference clock signal may be used in the device generating synchronization information for the data packet such that , for example , both sampling rates in the transmitting device and the data packet receiving device become synchronized .

[0041] The step of adj usting its set of recording parameters may for example , include adj usting the frequency of a clock signal used for generating a sample rate for recording the sound signal . In some other aspects , the step of adj usting comprises adj usting a multiplication factor for the frequency of a clock signal used for generating a sample rate . In some other aspects , a sample rate based on a clock signal is adj usted . Additionally, or alternatively, a delay of a clock signal used for generating a sample rate can be adj usted .

[0042] The data packet containing the synchronization information referred to as synchronization signal may be transmitted between consecutive packages comprising the recorded first sound signal or after a dedicated amount of time after one of an event corresponding to receiving a packet containing a portion of the first sound signal . The data packet may also be transmitted after an event corresponding to sending or having sent a packet containing a portion of the first sound signal . In some aspects , the data packet is transmitted after an event corresponding to sending or having sent a packet containing a portion of the multichannel sound signal . The data packet may contain an identifier providing information about the number of data packets being transmitted . In some implementations , the second mobile recording device is configured to generate and transmit the synchronisation signal to the first mobile recording device periodically, in particular after receiving a dedicated number of packages . In some other implementations , the UE may transit such a data packet . In such cases , a plurality of first recording mobile devices may be used .

[0043] The first and / or second recorded sound signal may be compressed either lossless or with a slightly lossy format , like for example , the LC3 compression . Other lossy formats can be used as disclosed herein . Suitable protocols for the first and second packet-oriented transmission protocols comprise Bluetooth, Bluetooth Low Energy Audio , LE Audio protocol , as well as 802 . 11 protocol family . The synchronization signal is based on the Bluetooth LE Audio protocol , particularly based on connected isochronous PDU . In some further aspects , the method also proposes to record, by the UE , a third sound signal using a third set of recording parameters . Likewise , the UE may combine the recorded and received sound signals to a combined multichannel sound signal . The combined multichannel sound signal may include at least one third recorded sound signal from the UE as well as at least the portion of the received multichannel sound signal . In some aspects , in which the UE receives sound signals from first mobile recording devices , the UE may generate a combined sound signal therefrom.

[0044] SHORT DESCRIPTION OF THE DRAWINGS Further aspects and embodiments in accordance with the proposed principle will become apparent in relation to the various embodiments and examples described in detail in connection with the accompanying drawings in which

[0045] Figure 1 shows an exemplary sound environment to illustrate several aspects of the proposed principle ; Figures 2 illustrates an exemplary embodiment of a multichannel recording arrangement according to some aspects of the proposed principle ;

[0046] Figure 3 shows a time diagram illustrating a data packet transmission in connection transmission of a packet containing a synchronization signal in accordance with some aspects of the proposed principle ;

[0047] Figure 4 illustrates a structure for a packet containing synchronization information in accordance with some aspects of the proposed principle ;

[0048] Figure 5 shows an embodiment of a receiver in a slave device in accordance with some aspects of the proposed principle ;

[0049] Figure 6 illustrates an embodiment of two devices illustrating some aspects of the proposed principle ;

[0050] Figure 7 shows another embodiment of another multichannel recording arrangement in accordance with soe aspects of the proposed principle ;

[0051] Figure 8 shows an exemplary method for recording a multichannel sound signal in accordance with some aspects of the proposed principle .

[0052] DETAILED DESCRIPTION

[0053] The following embodiments and examples disclose various aspects and their combinations according to the proposed principle . The embodiments and examples are not always to scale . Likewise , different elements can be displayed enlarged or reduced in size to emphasize individual aspects . It goes without saying that the individual aspects of the embodiments and examples shown in the figures can be combined with each other without further ado , without this contradicting the principle according to the invention . Some aspects show a regular structure or form . It should be noted that in practice slight differences and deviations from the ideal form may occur without , however , contradicting the inventive idea . In addition, the individual figures and aspects are not necessarily shown in the correct size , nor do the proportions between individual elements have to be essentially correct . Some aspects are highlighted by showing them enlarged . However , terms such as "above" , "over" , "below" , "under" "larger" , "smaller" and the like are correctly represented with regard to the elements in the figures . So it is possible to deduce such relations between the elements based on the figures .

[0054] Figure 1 illustrates an exemplary sound environment , in which an audio session is recorded creating a sound scene . The environment depicted in Figure 1 also includes three speakers identified as sound sources SI , S2 and S3 as well as several further obj ects either creating sounds by themselves or changing existing sounds coming from the sound sources . To this extent , the sound environment resembles a typical situation for content creators , in which the proposed solution is the desired fit .

[0055] The respective speakers are arranged in proximity to one or more walls restricting the sound space in two directions . In case of a more closed space , one can also consider a ceiling, but this environment may also take place during a street interview close to house walls , fences and the like .

[0056] The speakers are arranged around a central reference point , in which a microphone array MA is positioned . In the present example , the microphone array MA comprises a mobile device like a mobile phone or a camera device that includes a plurality of microphones being set spatially slightly apart . However , such microphones are not a requirement but can be suitable to further improve the sound quality during subsequent processing of the recorded sound space . Furthermore , the second speaker or sound source S2 comprises a portable microphone M2 directly attached to him. One can reasonably assume that M2 is associated with the sound source S2 in this regard . Likewise , the third speaker S3 comprises another portable microphone MS , which is directly attached to his / her body, for example , close to his / her mouth . In contrast thereto , speaker and sound source SI do not have an additional microphone attached to its body close by or generally associated with this sound source . Furthermore , possible obj ects may produce shortterm sound, referred to as events . An example of such obj ects in Figure 1 is given by the car , driving by creating event El . Event el is a short-term event and can occur randomly . Other events , like noise from a fan, are often constant or only slightly varying in amplitude and provide some background noise .

[0057] The three speakers are talking to each other , for example , in a podcast an interview and the like . Their voices as well as the background noise and the events are recorded by the microphones of the phone MA as well as the two microphones , M2 and M3 .

[0058] During the recording session, several events and situations can occur , which are explained in more detail . If speaker S2 or S3 are speaking , the respective microphones M2 and M3 will record their voices substantially without delay, as the microphones are located close to the respective body and mouth . In addition, the voice of speaker S2 will reach the microphone M3 and vice versa after some delay and subsequently recorded as well . Any voice component coming from either a different sound source or being reflected from a wall portion ( see below) is considered crosstalk for the purpose of this example . Likewise , the speech and voice of speaker S3 will generate crosstalk in microphone M2 . Additional crosstalk portions may occur due to reflections of the respective voices on the wall and reaching the corresponding microphones again after some delay . However , in this regard, a reflection of the voice from speaker S3 being recorded at microphone M3 is also considered cross talk in its recorded signal . Consequently, microphones M2 and M3 may record crosstalk of two different types , one being the voice and speech of the respective other sound source and one being the own voice and speech but recorded with a certain delay due to reflections on obstacles and the like .

[0059] In contrast , speaker SI does not have its own microphone associated with him . As a result , any of his / her voice components and speech is recorded by microphones M2 , M3 with a certain delay as a so-called direct sound DS . The delay between those portions m the two recordings at microphones M2 and M3 enables determining the position of SI with regard to the two other sound sources S2 and S3 . Similar as for the voices and speech of the sound sources S2 and S3 , the speech and voice of sound sources S2 may be reflected at the wall and further delayed before being recorded by one of the microphones M2 and M3 . That reflected portion is also considered crosstalk for the purpose of this example .

[0060] The mobile device MA being located at the reference point for this sound scene also records the various voice portions and speech portions of the respective sound sources and speakers SI , S2 and S3 . More particularly, such voices are recorded either as direct sounds DS with various delays and / or also as crosstalk when being reflected at the wall or other obstacles . In addition, it may also record any noise , either from nose events like El or as background noise ( again with possible reflections thereof at the wall ) . As a result , the microphones of microphone array MA record a plurality of sound signals , which contain the voice and speech portions of the various sound sources with a slight delay to each other . Furthermore , the plurality of recorded signals also contains the recorded signals of microphones M2 , and M3 including the voice and speech portions of the sound sources SI to S3 as well as the respective crosstalk .

[0061] Apart from the voice and speech components as well as the crosstalk thereof , noise and other events can occur in the sound scene during the recording session . An example is given in Figure 1 , in which event El is created by a car driving by . This additional non-voice portion is recorded by the two microphones M2 and M3 as well as by the microphone array MA with different delays . As those events usually happen at random and are only present during a short period of time , they are considered a noise event in contrast to other noise portions , which are inherently and continuously present . Those other noise portions may include lower or high-frequency noise of machinery being present close to the location the recording is taking place , a plurality of people chattering in the background, or natural sounds like wind whistling and the like . Consequently, the overall noise being recorded by the microphones can be differentiated m noise events as well as background noise .

[0062] The various sound signals originating from the sources and / or the respective events , including noise , are recorded usually independently of each other . Consequently, each of the recorded signals may contain portions of sounds that are temporarily displaced to each other due to the distance between the respective microphone and the sound source . Moreover , each microphone uses a base clock signal to derive the sampling rate for recording the sound in the sound environment . This clock signal is subj ect to deviation and will drift in its frequency over time . This frequency deviation is due to aging of the oscillator crystal but also temperature changes and other effects . As a result , the sampling rate for the recording varies over time .

[0063] The frequency deviation in the sampling rate between the recorded sound signals increases the effort and may render combining the sound signals for a multichannel signal and further processing even impossible . The inventors now propose a synchronization of the base clock and / or sampling frequency for the mobile recording devices and, optionally, the mobile device to overcome this drawback and obtain recorded sound signals that are sampled with substantially the same sampling rate .

[0064] Figure 2 illustrates an exemplary embodiment of the proposed arrangement . The depicted sound environment comprises three sound sources , SI , S2 and S3 with respective mobile recording devices Ml , M2 and M3 associated with each of the respective sound sources . As further explained in detail , the mobile recording devices are configured in a master slave combination, with mobile recording devices M2 and M3 being the slave devices and mobile recording device Ml being the master device . Each of the slave devices M2 and M3 comprises a microphone for recording the speech of the associated sound source and other sounds . The microphone is connected to a processor 11 having a base clock for generating one or more signals at various frequencies (using dividers or multiples ) , at which at least one of the generated signals is adj ustable in its frequency . One of said signals may be used to derive the sampling rate for the processor / microphone during recording of the sound . Possible sampling rates ae 44 . 1 kHz or 48 kHz for example , although different sampling rates may be suitable .

[0065] The processor is further configured to compress the recorded sound signal using a lossless compression like FLAG or a slightly lossy compression like LC3 for example . The respective mobile recording device may also comprise a smaller buffer memory ( not shown herein ) for storing the recorded and processed signal before transmitting it . Each of the slave mobile recording devices M2 and M3 comprises a radio 12 connected to an antenna 13 . The radio 12 includes a transmitter and receiver . Radio 12 is configured to transmit the recorded and compressed audio signals over the antenna 13 using a first wireless transmission protocol to the master mobile recording device Ml .

[0066] In the present example , the master and slave devices are not spaced very far from each other; hence , a low power consumption transmission protocol may suffice for this purpose . Such protocols include , for example , Bluetooth and its derivatives like Bluetooth LE audio and the like . They are characterized by low power consumption, which is beneficial for mobile devices to enhance the recording time . Furthermore , the packets allow for a high data rate transmission with optional error correction and packet loss correction . In the present example , mobile recording devices M2 and M3 are set up for the transmission of recorded sound packets without re-transmission in case of packet loss . Hence , the device Ml does not acknowledge correct reception of packets , and the radio in the mobile recording devices M2 and M3 does not listen for such acknowledgement . While such an approach may deteriorate the overall quality of the recorded sound signals in case of packet loss , it simplifies the transmission and enables higher data rates . It has been observed that with small packet size , containing only a few ms of recorded sound in a common environment , the deterioration of the recorded sound signal due to packet loss is negligible .

[0067] The transmitted packets P with the recorded sound signal are received by the master mobile recording device Ml . The master mobile recording device Ml comprises a radio 12 for receiving the transmitted data packets and decoding them to obtain the compressed recorded sound data embedded therein . The recorded sound data obtained from the two other microphones M2 and M3 are buffered in memory, said memory being part of a processor device 11 of the master mobile recording device Ml . Likewise , the master mobile recording device Ml records a sound signal using the microphone 10 being part of its casing and associated with sound source SI . The recorded sound signal is compressed and then used together with the previously stored sound signals from the other two recording devices to generate a multichannel sound signal therefrom . The generated multichannel sound signal is then forwarded to a second radio 12 ' to be transmitted via the antenna 13 ' to a mobile device UE , like a phone , a camera and the like , using a second transmission packet oriented protocol . Radio 12 ' and 13 ' can be an integral part of the radio 12 and antenna 13 , respectively, but also implemented as two separate devices .

[0068] The second transmission packet-oriented protocol may be different from the first , and in particular includes data error correction and a correction for data packet losses . In other words , the UE acknowledges correct receipt of any packet transmitted by the master mobile recording device M3 , while M3 waits for such acknowledgement and retransmits the packet if reception is not confirmed within a certain timeframe . This ensures that packet loss is avoided . The WI FI standards 802 . llx, Bluetooth as well several other packet-oriented wireless communication standards provide packet loss avoidance and correction functionalities .

[0069] The mobile device UE receives the transmitted packages via antenna 14 , acknowledges the receipt by radio 15 , and decodes it to obtain the multichannel signal using its radio 15 . The decoded portion of the multichannel signal is then stored in memory 17 for either further processing using the processor 16 or subsequent transmission to a cloud C using a wireless or wired communication protocol . Further processing of the recorded sound signal may include , but is not limited to denoising, compression, crosstalk reduction, speech detection leveling , balancing and others . Several approaches are possible for the generation of a multichannel sound signal by the master mobile recording device . In a first simple approach, the individual sound portions , which are the respective received data packets from mobile recording devices M2 and M3 are simply added together to generate larger chunks of the respective recorded sounds . In a different approach, the obtained recorded signal may contain a certain time stamp or any other correlation that enables the master mobile recording device to provide a simple correlation between the obtained recorded sound signals . In a further approach, the master mobile recording device contains a memory storing a larger portion of the respective recorded sound signals ( received by M2 and M3 and recorded by itself ) .

[0070] In any case , the chunks are then combined with the compressed recorded signal of device M3 . In this regard, one may use the already existing compressed sound data or recompress the sound data chunks again . The latter can be useful , as the data representing the multichannel sound signal may have different characteristics compared to the original sound files . As such, different compression algorithms can be applied hereto to reduce the overall size of the multichannel sound signal .

[0071] As explained above , the slightly different clock signals in the three mobile recording devices Ml , M2 and M3 cause a deviation in the sampling rate and, thus , irrespective of a time delay, a deviation in the recorded signals . In order to reduce such deviation in the sampling rate , a synchronization signal SS is broadcast from the master mobile recording device Ml and subsequently received by the slave mobile recording devices M2 and M3 . The master mobile recording device is configured to generate a synchronization signal based on one of its clocks , further used as a reference clock signal . This clock signal or its characteristics , including its periodicity, may act as synchronization to adj ust the base frequency clocks in the respective slave mobile recording devices . The generated synchronization signal is transmitted by the master mobile recording device between the transmission and reception of the data packets of the two slave mobile recording devices . Upon reception of one or more of the synchronization signals , the two slave mobile recording devices M2 and M3 will decode the received signal and process the information within the received packet . The processor utilizes the information to adj ust one or more parameters of its process to record, that is , sample the respective sound signal . By transmitting the synchronization signal periodically or at least repeatably, a deviation in the sampling rate is reduced below a threshold given by the frequency of the transmission of such a synchronization signal and of course , the inherent drift of the clock signal in the slave mobile recording devices .

[0072] The data packets , including portions of the compressed recorded sound signal , are transmitted by the two mobile recording devices M2 and M3 according to a packet-oriented communication protocol . The data transmission may occur alternating with each of the devices transmitting packets periodically . Each packet contains an identifier enabling the master mobile recording device to correctly assign the received packet to one of the slave recording devices as well as a counter to arrange the packets correctly and / or identify missing packets . The packet length may differ in between subsequent packets .

[0073] Figure 3 illustrates a possible embodiment , in which one or more Bluetooth packets BPx are transmitted; each of those Bluetooth packets may comprise the same or different length as indicated . However , the Bluetooth packets are not transmitted continuously but in certain intervals , in which no transmission or reception between the respective Bluetooth packets BPx takes place . This is indicated in Figure 3 by certain time slots on the time axis . Bluetooth packets are transmitted at certain times T whereas the lengths of the respective packets may vary in accordance with the data content to be transmitted or received . Furthermore , due to the limited content of the data packages DPI , DP2 , the packet length is limited and does correspond to the lengths of the Bluetooth packets in the present example .

[0074] Data packages DPI and DP2 with synchronization information are now transmitted by the master mobile recording device Ml between the time periods T , in particular approximately in the middle of the intermediate intervals , m which no transmission or reception takes place . No complicated error correction, either bit or block error correction, may take place . Furthermore , the data packets are transmitted consecutively and / or periodically, for example , after a certain amount of time .

[0075] Rather , the content of the data packets DPI and DB2 being transmitted from the master device to the slave device can be demodulated in a simple way with no significant error correction necessary and subsequently processed on a low hardware level according to the OSI model . The layers on which the data packages DPI and DB2 are usually handled are layer 0 or layer 1 in the OSI model and normally do not extend to higher levels . This is beneficial , as this low-level processing can quickly trigger any hardware counter , thereby reducing overhead and a possible delay or glitches due to processing on higher OSI layers . More particularly, processing on these lower layers can be implemented in real time , or almost real-time without any significant delay . The length of the data packets is usually short and does not interfere with the packet transmission according to the Bluetooth protocol . The base frequency on which the packets DPI and DP2 are transmitted is known and may follow the actual requirements and rules for the Bluetooth protocol . Each radio of the slave mobile recording devices sets itself on the known base frequency and listens for such data packets .

[0076] The data packages DPI , DB2 being transmitted may comprise a bit pattern as indicated in Figure 4 . Each data package contains a header or identifier ID of a certain bit length . The bit lengths are chosen such that on the one hand, the demodulator is able to detect a proper identifier of the data package compared to eventually demodulated noise . The identifier may identify one or more slave devices among a plurality of slave devices . This allows grouping of devices and enables , for example , transmitting packets specifically directed to certain slave devices . Alternatively the identifier ID can be used to identify or select a specific clock frequency and multiplication factor , respectively to be adj usted within a certain slave device . The identifier can also have no further meaning and j ust be used to trigger the counter and indicate the reception of the data package . The identifier is usually placed at the start of the respective data package but can also be arranged at the end or in the central portion thereof .

[0077] In the present example , the data package contains two further subsets referred to as Patternl and Pattern! , each of those having a certain bit length . As illustrated herein, both subsets comprise the same bit lengths . The subsets contain values corresponding to events or pulses or any other characteristics of the reference clock, to which the clock frequency is to be adj usted . For example , subset Patternl may comprise a first value indicating the time in milliseconds that has passed since a certain start time . Subset Pattern! may comprise a time value in microseconds . Consequently, each data package contains a value consisting of the milliseconds and microseconds that have passed as evaluated by the reference clock since a certain start time . The bit lengths of subset Pattern! in this regard may be set to 10 bits , which corresponds to a maximum value of 10! 4 indicating that thousand microseconds correspond to 1 ms . The separation in two subsets within the data package can be beneficial in later processing . Furthermore , these two subsets can also be used to adj ust different clock signals within the same slave device identified by identifier ID in the data package .

[0078] Figure 5 illustrates a further embodiment of a transceiver 10 ' in accordance with the proposed principle . The transceiver can be implemented in the mobile recording devices , such that one of a plurality of devices can act as a master device generating and transmitting the synchronization signal , while the other devices , having the same implementation of transceiver 10 ' act as slave devices configured to adj ust its clock or any other parameter upon reception of data packets , including the synchronization information .

[0079] The transceiver 10 ' comprises an antenna portion 13 , which is connected to a low-noise amplifier 106 . The antenna 13 is configured to receive various signals over a wireless air interface . These signals may correspond to a packet-oriented communication protocol like Bluetooth, ZigBee , 80! . 11 and similar protocols . The antenna 13 is also configured NQ01P038WQ 24 to receive the data packages DPI and DP2 m accordance with the proposed principle . Based on the implementation, the data packages DPI and DP2 correspond to data packets as defined by the underlying communication protocol . For example , Bluetooth LE Audio is a communication standard that provides specific packets referred to as connected isochronous PDU that enable the receiver to adj ust its clock within a few ]is due to its high accuracy in relation to the anchor point and the CIS and CIG event structure . To this extent , the slave device may utilize Bluetooth LE Audio to transmit the recorded and compressed sound signal to the master device . One of the devices can now also act as master in regard to generating and transmitting the connected isochronous PDU to the respective other device ( s ) in order to adj ust its characteristic parameter when recording audio .

[0080] In some other implementation, the data packages DPI and DP2 do not correspond to data packets as defined by the underlying communication protocol . The data packets are demodulated on a low hardware layer with its content processed thereon to avoid the processing on higher layers of the OSI model , thereby avoiding possible delays during the processing .

[0081] Antenna 13 of transceiver 10 ' is coupled to a low noise amplifier 106 , whose output is connected to an IQ demodulator 107 . Although the current example utilizes an IQ demodulator 170 , other demodulation units like and OFDM demodulator , SDR and others are also suitable . The IQ demodulator comprises a local oscillator signal input ( not shown herein ) , which in turn is coupled to a local master clock oscillator 400 . The output of the demodulator is connected to a pre-processing device 108 , which in turn is connected to a memory 109 . The preprocessing device 108 receives several clock signals from the local master generator , not shown herein . Furthermore , the preprocessing device 108 is coupled to a timer circuit or counter 420 as well as to a comparator unit 601 , which also receives data from a local memory 600 . The output of the preprocessing device 108 is connected to a memory 109 to store the content of the data packages received in accordance with the proposed principle . NQ01P038WQ

[0082] The output of the memory 109 is coupled to a comparator 431 , which m turn is connected to an adj ustment circuit 433 to provide an adj ustment signal on output 433 . The output is used to adj ust any parameter affecting the sampling rate . For example , a possible deviation is adj usted by changing the multiplication factor of the clock signal ( not shown herein) that is also driven by the local master clock generator 400 .

[0083] In a possible exemplary operation of the transceiver, a data package is received via antenna 13 and amplified by the low-noise amplifier 106 . The IQ demodulator 107 demodulates the received signal and provides a bit sequence to the preprocessing device 108 . The preprocessing device uses the first bit of the sequence corresponding to a possible header and forwards the bits to the comparator 601 . The comparator 601 compares the received bit sequence with a stored sequence provided by memory 600 , corresponding to an identification tag . If the bit sequences are not equal , the comparator transmits a signal indication to ignore the rest of the received message .

[0084] Upon a correct identification, the comparator 601 triggers the timer or counter 420 to start the event counter . The preprocessing device 108 is also provided with a corresponding feedback of positive identification and continues to demodulate the rest of the received data package . The remaining bits are saved as a pattern in the temporary memory, wherein the pattern corresponds to a value . After a certain period, a new data package is received via antenna 13 . The received signal is again amplified and demodulated via demodulator 17 . The preprocessing device 108 provides the first bits , corresponding to the header , to the comparator 601 , which compares it again with the stored sequence in memory 600 to evaluate the identification . Upon the correct identification, the content of the received data package is processed, and the second value obtained by preprocessing device 108 . The value is stored in memory 109 .

[0085] Furthermore , upon correct identification, the timer and counter 420 are triggered by the comparator to stop the event counting . So far , the counter has counted the pulses of the local reference clock provided by the master clock generator 400 between the two triggering events , that is between reception of the first and second data packages . The counted pulses are forwarded to comparator 431 , which also receives the two values from the temporary memory 109 . These results are compared to estimate a possible time gap or frequency deviation between the values received in the data packages and the counted pulses in between the received data packages . Any possible gap or deviation is forwarded to the adj ustment circuit 433 , which adj usts the multiplication factor and provides an adj usted multiplication factor at the output 433 .

[0086] The process can then continue or be repeated with another data package , which is subsequently demodulated, pre-processed and stored in the memory area . Consequently, a possible deviation either in time or frequency ( given by the difference of the counted pulses and the value in the received packages ) is estimated at the reception of the subsequent data packages . This will result in a periodical update of the adj ustment factor .

[0087] Figure 6 illustrates a master-slave configuration of two mobile recording devices in accordance with the present invention . Those devices can, for example , be used in the arrangement of Figures 1 and 2 . Each of the devices records sound signals . One of the devices provides a synchronization signal using a packet-oriented protocol and receives the recorded and compressed sound signal from the slave device . The synchronization content enables the slave device to adj ust a clock frequency to a common time base .

[0088] The transmitter or master device Ml comprises one or more antennas 13 and 201 , which are suited to communicate with the slave device M2 in accordance with one or more wireless communication protocols . At the same time , the master device Ml is configured to receive data packets from the slave device M2 comprising compressed recorded sound content .

[0089] The wireless communication protocols used for transmission of data packets (both containing sound content and synchronization information ) are time-division multiplexed and packet-oriented protocols , meaning that the transmission and reception takes place in defined data packets being transmitted or received over the wireless communication interface using the antennas 13 , 201 . A time gap can occur between data packets being transmitted or received . Examples for packet-oriented data packages with such a time gap include but are not limited to the one already mentioned herein . The transmitter Ml further comprises a respective communication interface 101 that is coupled to the antennas 201 . The communication interface 101 is connected to a memory and processor 170 for storing the recorded sound from its own microphone and the received sound data packets . The processor and memory 170 are configured to generate a multichannel sound signal therefrom . In some aspects , this information is time coded, time stamp or otherwise assigned with an identifier , enabling a further device to arrange the various sound portions in the correct order . In other aspects , the multichannel signal is already generated such that the sound signals are in correct order . A typical , yet very simple , multichannel signal can be for example , a stereo signal , in which each sound recorded by the respective devices utilizes one of the stereo channels . Other formats for multichannel audio are known to the skilled person .

[0090] The communication interface 101 is further connected to a data package generator 160 for generating data packages with synchronization information in accordance with the proposed principles . These data packages are generated by the data package generator 160 using a global reference clock from a reference clock generator 150 . For this purpose , reference clock generator 150 is connected to an input 162 of the data package generator 160 . The package generator 160 uses the reference clock to provide a first and date second data package in accordance with the proposed principle by generating a value corresponding to the reference clock . The data packages are transmitted via the communication interface to the slave device . In other words , the reference clock generator 150 provides a signal with a reference clock frequency, to which the slave device and, more particularly, the clock frequency of the slave device in accordance with the proposed principle is synchronized . Likewise , the reference clock generator 150 also provides the reference clock, from which the master mobile recording device derives its own sampling frequency for its microphone 310 . Hence , after the slave device is synchronized, both sampling rates will be the same .

[0091] The reference clock generator 150 also provides all further clock signals to the respective components of the transmitter . As an exemplary implementation here , the reference clock generator 150 is connected with its output 151 to a clock input of the communication interface 101 for providing a clock signal to the communication interface . In the case of other implementations , for example , using LE Audio for generating the synchronization information, one may utilize the respective Bluetooth stack and a different hardware .

[0092] The slave device M2 comprises two or more antennas 13 connected to a communication controller 502 . The communication controller 502 is connected to a control unit 430 . Control unit 430 , communication controller 502 and the antennas form the communication interface 100 of the transceiver 10 . The communication controller 502 is also connected to a control device 501 . The control device 501 is coupled to a recording device 500 , which in turn is connected to an input device 310 , for example , a microphone . In operation of the transceiver , the microphone 310 records a sound signal using the recording device 500 , which is forwarded to the control device 501 . The recorded sound signal is then transmitted via the communication controller 502 using a packet-oriented communication protocol to the transmitter 11 .

[0093] The recording device 500 is supplied by clock frequency provided by an adj ustable clock generator 410 . The adj ustable clock generator 410 utilizes a local clock signal provided by a local master clock generator 400 and an adj ustable multiplication factor . Consequently, the clock frequency provided to the recording device 500 is derived from the multiplication factor and the local master clock generator 400 by changing either the local master clock generator or the multiplication factor . The clock signal can therefore be adj usted . The transceiver M2 further comprises a timer or counter 420 , which is connected with its input either to the adj ustable clock generator 410 or the local master clock generator 400 . The timer or counter 420 is used to count pulses from one of the clock signals provided by generators 400 and 410 , thereby simply speaking, measuring the respective frequency thereof . The timer or counter 420 is controlled by the control device 430 . This implementation uses certain hardware components to adj ust the clock frequency used for generating the sampling rate of the microphone . It will be acknowledged by the s killed person that different implementations for adj usting the sampling rates are possible . In some aspects , for example , one may adj ust only the sampling rate using the synchronization information, changing a multiplication factor for the clock generating the sampling frequency .

[0094] In other aspects , the synchronization signal may be generated by the slave device . In such a case , the master device received data packets with the recorded sound and subsequent data packets with the synchronization information . Such an approach may be suitable , as the slave device does not require a receiver in such a case but only a transmitter . Element 160 is then implemented in slave device M2 , while timer 420 and control device 430 are implemented in the master device . The master device still generates the multichannel from the recorded signal and provides it to the UE as illustrated above . Data packets containing the synchronization information are generated periodically to ensure that any deviation in the sampling frequency stays below a threshold .

[0095] Figure 7 illustrates a further embodiment of an arrangement in accordance with the proposed principle . The arrangement comprises two first mobile recording devices M2 and M3 , each of the mobile recording devices associated with a respective sound source S2 and S3 . Each of the first mobile recording devices , M2 and M3 comprise a microphone 10 recording the sound . An internal processor samples the recorded sound signal using a given sampling signal with an adj ustable frequency and subsequently compresses the sampled recorded sound signal using a lossless or slightly lossy compression, like LC3 compression, for example . The recorded and compressed sound signals are then transmitted to a radio device 20 connected to a mobile device UE , like a mobile phone , a camera and the like . The first and second mobile recording devices use a Bluetooth protocol , like standard Bluetooth or Bluetooth LE audio of the transmission . Other data packet-oriented transmission protocols are suitable as well .

[0096] The radio device 20 is either an integral part of the mobile device UE or , as in the present example , connected thereto via a USB interface . The radio 20 comprises a receiver for receiving the respective packets containing recorded and compressed sound signals from the first mobile recording devices . The radio 20 forwards the received data packets to the UE for further processing and storage . The UE also comprises one or more microphones recording sound signals and compressing them . The UE is also configured to receive the different sound signals from the radio 20 and generate a multichannel sound signal from the various sound signals . To this extent , the UE and radio 20 implement the same functionality as the second mobile recording device .

[0097] Furthermore , the UE compromises a processor configured to process the received sound signal . Such processing includes , but is not limited to denoising the various sound signals .

[0098] The radio 20 is also configured to generate data packets , including synchronization information to synchronize the sampling frequency in the first mobile recording devices M2 and M3 as explained herein . The respective reference clock ( from which the respective synchronization information is derived ) is either implemented in the radio 20 itself or part of the UE . In the latter case , the radio receives the respective information from the UE .

[0099] The radio 20 transmits the data packet containing the synchronization information to the first mobile recording devices . Upon reception, the information is used to adj ust the sampling rate accordingly, such that both devices record with the same sampling frequency . The UE may also record with the same sampling rate .

[0100] Figure 8 illustrates a possible embodiment of a method for generating a multichannel sound signal . Step SI is a preparatory step, in which at least two mobile recording devices are provided . For the purpose of this exemplary embodiment , a UE is also provided, although it is understood that the UE may also refer to a mobile recording device . To start a recording session, the UE may send a respective start signal to the two mobile recording devices . Upon reception, the two mobile recording devices start recording the sound signal . In addition, further steps , like , for example , transmitting a data packet containing synchronization information, can be transmitted to ensure that the sampling rate ( or any other parameter ) for all mobile recording devices is adj usted and substantially the same . In some instances , such a data packet is transmitted by the UE , particularly if the UE shall record a sound signal as well . In other aspects , the data packet with the synchronization information is transmitted by one of the mobile recording devices .

[0101] After reception of an indication to start recording , in step S2 the first mobile recording device records a first sound signal using a first set of recording parameters . The set of parameters may include but is not limited to the sampling frequency or sampling rate , for example , one of 22 kHz , 44 . 1 kHz and 48 kHz . Likewise , the second mobile recording device records a second sound signal in step S3 using a second set of recording parameters . The second set of parameters is similar or equal to the first set of parameters , e . g . the sampling rate is nominally the same .

[0102] Each of the recorded signals may be compressed to have its size reduced . The compression may be lossless or slightly lossy using , but not limited to one of the compression methods disclosed herein . The recorded and compressed sound signals may be stored in a small buffer .

[0103] The proposed method then continues with step S4 , in which the first mobile recording device using a first packet-oriented transmission protocol transmits the recorded first sound signal to the second mobile recording device . The first packet-oriented transmission protocol transmits not continuously but in data packets of either equal or variable length . This transmitted signal is received by the second mobile recording device in steps S5 . The received compressed sound signal is then combined with the second recorded sound signal to form a multichannel sound signal comprising the received first sound signal and the recorded second sound signal by the second mobile recording device in step S 6 . For the purpose , the second mobile recording device may also compress its own recorded sound signal prior to generating a multichannel sound signal using preferably the same compression algorithm.

[0104] In some other aspects of step S 6 , the second mobile recording device decompresses the received compressed first sound signal and then combines it with its own recorded sound signal to create a multichannel sound signal . The generated multichannel sound signal can be optionally compressed to further reduce the size . The multichannel sound signal is then transmitted to the UE in step S7 using a second packet-oriented transmission protocol .

[0105] As the recording continues , the clock frequency and particularly the sampling rate of the respective recording devices may start to differ from each other . In accordance with the proposed principle , a data packet is generated by one of the UE , first and second mobile recording devices , referred to as the master device , for the purpose of such creation . This step is illustrated in step S8 . The data packet contains synchronization information related to clock frequency and particularly concerning the adj ustment of the sampling rate . The data packet is transmitted by the respective master device in step S9 and subsequently received in step S10 by at least one of the first and second mobile recording devices the data packet . In response thereto , the receiving device utilizes the information to adj ust its set of recording parameters .

[0106] The steps S8 to S10 are periodically repeated to ensure synchronization accuracy over a longer period of time . For example , the data packets may be generated and transmitted after a few 100 ms . In some aspects , the data packet is a connected isochronous PDU according to Bluetooth LE Audio standard . For example , the mobile phone may generate such connected isochronous PDU as a master device , irrespective of whether it is recording an audio signal as well . Alternatively, one of the mobile recording devices may be used for such a task .

Claims

PATENT CLAIMS1 . Multichannel recording arrangement , said arrangement comprising :A first mobile recording device , said first mobile recording device configured to record a first sound signal using a first set of recording parameters and comprising a radio configured to transmit the recorded first sound signal using a first packet- oriented transmission protocol ;A second mobile recording device , said second mobile device configured to record a second sound signal using a set of second recording parameters and further comprising at least one radio configured to receive the transmitted recorded first sound signal and to transmit a multichannel sound signal comprising the received first sound signal and the recorded second sound signals using a second packet-oriented transmission protocol ;A UE comprising a radio configured to receive the multichannel sound signal , and a memory configured to store at least a portion of the received multichannel sound signal ; the UE further configured to establish a wireless transmission using a second communication protocol to a remote network to transmit the stored received multichannel sound signal ; whereinOne of the first and second mobile recording devices is configured to transmit a synchronization signal to the other one of the first and second mobile recording devices , said other one of the first and second mobile recording devices configured to adj ust its set of recording parameters in response to the synchronization signal .2 . Multichannel recording arrangement according to claim 1 , wherein the set of parameters to be adj usted comprises one of : a frequency of a clock signal used for generating a sample rate ; a multiplication factor for a frequency of a clock signal used for generating a sample rate ; a sample rate based on a clock signal ; a delay of a clock signal used for generating a sample rate .3 . Multichannel recording arrangement according to claim 1 or 2 , wherein the synchronization signal is transmitted between consecutive packages comprising the recorded first sound signal .4 . Multichannel recording arrangement according to any of the preceding claims , wherein the synchronization signal is transmitted after a dedicated amount of time after one of an event corresponding to receiving a packet containing a portion of the first sound signal ; an event corresponding to sending or having sent a packet containing a portion of the first sound signal ; an event corresponding to sending or having sent a packet containing a portion of the multichannel sound signal .5 . Multichannel recording arrangement according to any of the preceding claims , wherein the synchronisation signal comprises a value corresponding to time value derived from a reference clock used in the one of the first and second mobile recording devices to set a sample rate for recording the sound signal .6 . Multichannel recording arrangement according to any of the preceding claims , wherein the second mobile recording device is configured to generate and transmit the synchronisation signal to the first mobile recording device periodically, in particular after receiving a dedicated number of packages .7 . Multichannel recording arrangement according to any of the preceding claims , wherein the first mobile recording device comprises a buffer memory to store at least a portion of the first recorded sound signal prior to its transmission .8 . Multichannel recording arrangement according to any of the preceding claims , wherein the second mobile recording device further comprises- a buffer memory, said buffer memory configured to store at least a part of the first sound signal ; and / or- a memory said memory configured to store at least a part of the second sound signal ;- a processor configured to obtain the f rst and second recorded sound signals and generate the multichannel sound signal therefrom.9 . Multichannel recording arrangement according to any of the preceding claims , wherein at least one of the first and second mobile recording device is configured to generate packets containing portions of the respective recorded sound signal in a lossless compression format ; or at least one of the first and second mobile recording device is configured to generate packets containing portions of the respective recorded sound signal with a LC3 compression .10 . Multichannel recording arrangement according to any of the preceding claims , wherein the first and second packet-oriented transmission protocols are the based on the same core protocol , in particular the Bluetooth protocol .11 . Multichannel recording arrangement according to any of the preceding claims , wherein the first packet-oriented transmission protocol comprises the Bluetooth Low Energy Audio , LE Audio protocol ; and / or wherein the second packet-oriented transmission protocol comprises one of LE Audio and Bluetooth standard protocol ; and / or wherein the synchronization signal is based on the Bluetooth LE Audio protocol , particularly based on connected isochronous PDU .12 . Multichannel recording arrangement according to any of the preceding claims , wherein the UE comprises one or more spatially separated microphones configured to record at least one third sound signal ; wherein the UE is configured to receive the synchronization signal and further configured to adj ust its set of recording parameters in response to the synchronization signal for recording at least one third sound signal ;wherein the UE is configured to generate a combined multichannel sound signal from the at least one third recorded sound signal and at least the portion of the received multichannel sound signal ; and wherein the UE is configured to transmit the combined multichannel sound signal to the remote network .13 . Multichannel recording arrangement according to any of the preceding claims , wherein the radio configured to receive the multichannel sound signal is a device separatable from the UE , and optionally wherein the device and the UE each comprises a USB port .14 . Multichannel recording arrangement according to any of the preceding claims , wherein the UE comprises a processor configured to generate a spatial audio signal from the received multichannel sound signal ; and / or enhance , in particular denoise the first and second recorded sound signal contained in the multichannel sound signal .15 . Multichannel recording arrangement according to any of the preceding claims , wherein the UE comprises one of :A mobile ;A tablet ;A laptop;A camera, in particular a video camera .16 . Method for recording a multichannel sound signal comprising the steps of :Recording , by a first mobile recording device , a first sound signal using a first set of recording parameters ;Recording , by a second mobile recording device , a second sound signal using a second set of recording parameters ;Transmitting, by the first mobile recording device using a first packet-oriented transmission protocol , the recorded first sound signal to the second mobile recording device ;Generating, by the second mobile recording device , a multichannel sound signal comprising the received first sound signal and the recorded second sound signals ;Transmitting, by the second mobile recording device , the multichannel sound signal to a UE using a second packet-oriented transmission protocol ;Transmitting, by one of the UE , first and second mobile recording devices , a data packet containing synchronization information related to clock frequency;Receiving , by at least one of the first and second mobile recording devices the data packet and adj usting , in response to the synchronization information, its set of recording parameters .17 . Method according to claim 16 , wherein the step of adj usting its set of recording parameters comprises adj usting at least one of :- a frequency of a clock signal used for generating a sample rate for recording the sound signal ;- a multiplication factor for a frequency of a clock signal used for generating a sample rate ;- a sample rate based on a clock signal ;- a delay of a clock signal used for generating a sample rate .18 . Method according to claim 16 or 17 , the synchronization signal is transmitted between consecutive packages comprising the recorded first sound signal or after a dedicated amount of time after one of an event corresponding to receiving a packet containing a portion of the first sound signal ; an event corresponding to sending or having sent a packet containing a portion of the first sound signal ; an event corresponding to sending or having sent a packet containing a portion of the multichannel sound signal .19 . Method according to any of claims 16 to 18 , wherein the second mobile recording device is configured to generate and transmit the synchronisation signal to the first mobile recording device periodically, in particular after receiving a dedicated number of packages .20 . Method according to any of claims 16 to 19 , further comprrsrng the step ofCompressing at least one of the first and second recorded sound signal with one of a lossless compression format and LC3 compression .21 . Method according to any of claims 16 to 20 , wherein the first packet-oriented transmission protocol comprises the Bluetooth, Bluetooth Low Energy Audio , LE Audio protocol ; and / or wherein the second packet-oriented transmission protocol comprises one of LE Audio and Bluetooth standard protocol and / or wherein the synchronization signal is based on the Bluetooth LE Audio protocol , particularly based on connected isochronous PDU .22 . Method according to any of claims 16 to 21 , further comprising Recording , by the UE , a third sound signal using a third set of recording parameters ; and / or generating a combined multichannel sound signal from the at least one third recorded sound signal and at least the portion of the received multichannel sound signal .

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