Signal Processing Method, Signal Processing Apparatus, and Program

Abstract

To transmit high quality sound by using a commonly used phone call application.SOLUTION: Provided is a signal processing method of a first acoustic signal and a second acoustic signal, which are collected from the same sound source, wherein the first acoustic signal is transmitted via a transmission path with less delay than the second acoustic signal. The signal processing method includes: receiving, by a first reception part, the first acoustic signal transmitted via a first transmission path; receiving, by a second reception part, the second acoustic signal transmitted via a second transmission path whose delay time on transmission is larger than the first transmission path and which is different from the first transmission path; calculating, by a delay amount calculation part, a transmission delay amount which is a relative delay amount in the first acoustic signal and the second acoustic signal; and delaying, by a delay amount addition part, the first acoustic signal based on the transmission delay amount and outputting the delayed first acoustic signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a signal processing method, a signal processing apparatus, and a program. This application claims priority based on U.S. Application No. 63 / 022,591, filed on May 11, 2020, the content of which is incorporated herein by reference.

Background Art

[0002] There is a demand to connect remote locations via a network to conduct online music lessons or remote meetings. It is conceivable to use an existing application program (hereinafter referred to as a call application) that provides an online call service such as Skype (registered trademark) to conduct an online music lesson or the like by linking video and sound.

[0003] In the case of conducting communication mainly centered on sound, such as an online music lesson, transmission of particularly high-quality sound is required while suppressing delay. On the other hand, for video, it is sufficient if the sound and video are synchronized, and such a high level of image quality is not required. For example, Patent Document 1 discloses a technique for expanding the number of participants in a music session while suppressing delay. Patent Document 2 discloses a technique for realizing high-quality and real-time online performance. Patent Document 3 discloses a technique for synchronizing a plurality of images.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the internal specifications of existing call apps are generally not disclosed and are black-boxed. For this reason, it is generally difficult to apply the technologies disclosed in Patent Documents 1-3 to existing call apps.

[0006] Since there are already multiple call apps in the market, it is also conceivable to select an app suitable for music lessons. General-purpose call apps such as Skype (registered trademark) are widely popular, and most people are familiar with operating such general-purpose call apps, so the introduction is smooth. However, with such general-purpose call apps, the transmission status of sound and images varies depending on the bandwidth situation, and high-quality sound is not necessarily transmitted. On the other hand, there is an acoustic dedicated session app that can transmit each other's performances with high-quality sound while minimizing transmission delay. However, since it is specialized for acoustic transmission and is rarely used for general calls, the general public is not familiar with operating the app, and the introduction is difficult. Also, since there is no video with only sound, it is not suitable for lessons.

[0007] That is, there is no existing call app or session app that is easy to introduce for beginners who are about to start learning music and can transmit high-quality sound. For this reason, there has been a problem that it is difficult to use for online music lessons.

[0008] The present invention has been made in view of such circumstances. Its object is to provide a signal processing method, a signal processing device, and a program that can transmit high-quality sound using a generally popular call app.

Means for Solving the Problems

[0009] To solve the above problems, the signal processing method of the present invention is a signal processing method for a first acoustic signal and a second acoustic signal in which the same sound source is picked up. The first acoustic signal is a signal processed through a transmission path with less delay than the second acoustic signal. A first receiving unit receives the first acoustic signal transmitted through a first transmission path, and a second receiving unit receives the second acoustic signal transmitted through a second transmission path different from the first transmission path and having a delay time related to transmission greater than that of the first transmission path. A delay amount calculation unit calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal. A delay amount addition unit delays the first acoustic signal based on the transmission delay amount, and outputs the delayed first acoustic signal. Instead of the second acoustic signal This is the signal processing method. Further, the signal processing method of the present invention is a signal processing method for a first acoustic signal and a second acoustic signal in which the same sound source is picked up. The first acoustic signal is a signal processed through a transmission path with less delay than the second acoustic signal. A first receiving unit receives the first acoustic signal transmitted through a first transmission path, and a second receiving unit receives the second acoustic signal transmitted together with a video signal through a second transmission path different from the first transmission path and having a delay time related to transmission greater than that of the first transmission path. A delay amount calculation unit calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal. A delay amount addition unit delays the first acoustic signal based on the transmission delay amount, and outputs the delayed first acoustic signal. Instead of the second acoustic signal This is the signal processing method.

[0010] Also, the signal processing apparatus of the present invention is a signal processing apparatus that performs signal processing on a first acoustic signal and a second acoustic signal in which the same sound source is picked up. The first acoustic signal is a signal processing apparatus that is transmitted via a transmission path with less delay than the second acoustic signal, and includes a first receiving unit that receives the first acoustic signal transmitted via a first transmission path, and a second transmission path whose delay time related to transmission is greater than that of the first transmission path and is different from the first transmission path, and a second receiving unit that receives the second acoustic signal transmitted via the second transmission path, a delay amount calculation unit that calculates a transmission delay amount that is a relative delay amount between the first acoustic signal and the second acoustic signal, and a delay amount addition unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal. Instead of the second acoustic signal A signal processing apparatus comprising: Also, the signal processing apparatus of the present invention is a signal processing apparatus that performs signal processing on a first acoustic signal and a second acoustic signal in which the same sound source is picked up. The first acoustic signal is a signal processing apparatus that is transmitted via a transmission path with less delay than the second acoustic signal, and includes a first receiving unit that receives the first acoustic signal transmitted via a first transmission path, and a second transmission path whose delay time related to transmission is greater than that of the first transmission path and is different from the first transmission path, and a second receiving unit that receives the second acoustic signal transmitted together with video via the second transmission path, a delay amount calculation unit that calculates a transmission delay amount that is a relative delay amount between the first acoustic signal and the second acoustic signal, and a delay amount addition unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal. Instead of the second acoustic signal A signal processing apparatus comprising:

[0011] In addition, the program of the present invention is a signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal in which the same sound source is picked up, and the first acoustic signal is transmitted via a transmission path with less delay than the second acoustic signal. A first receiving step of receiving, by a computer which is a signal processing device, the first acoustic signal transmitted via a first transmission path; a second transmission path having a delay time related to transmission larger than that of the first transmission path and different from the first transmission path; a second receiving step of receiving the second acoustic signal transmitted via the second transmission path; a delay amount calculating step of calculating a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; and delaying the first acoustic signal based on the transmission delay amount, and outputting the delayed first acoustic signal Instead of the second acoustic signal is a program for executing an additional delay amount step.

Effects of the Invention

[0012] As described above, according to the present invention, high-quality sound can be transmitted by using a generally popular call application.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0014] Hereinafter, a transmission system according to an embodiment will be described with reference to the drawings.

[0015] (First Embodiment) FIG. 1 is a block diagram showing a configuration example of a transmission system 1 according to the first embodiment. The transmission system 1 includes, for example, a transmission-side terminal 10, a reception-side terminal 20, a microphone 30, and a speaker 40. The transmission-side terminal 10 and the reception-side terminal 20 are communicably connected via a general-purpose communication line such as the Internet, for example.

[0016] The transmission system 1 is applied, for example, when performing remote music communication such as an online music lesson. In this case, in the transmission system 1, the transmission-side terminal 10 and the reception-side terminal 20 transmit acoustic signals to each other. In the following description, the case where the acoustic signal x(t) is transmitted from the transmission-side terminal 10 to the reception-side terminal 20 will be described as an example. The same method can be applied when an acoustic signal is transmitted from the reception-side terminal 20 to the transmission-side terminal 10.

[0017] In this embodiment, two applications, a session application and a call application, are installed on both the transmission-side terminal 10 and the reception-side terminal 20. The session application (hereinafter referred to as a dedicated application) is an acoustic dedicated session application. In the dedicated application, it is possible to transmit high-quality sound while suppressing the delay due to transmission as much as possible. The call application (hereinafter referred to as a general-purpose application) is a general-purpose call application that is widely popular in general, such as Skype (registered trademark). However, in the general-purpose application, the transmission state varies depending on the bandwidth situation, and high-quality sound is not transmitted.

[0018] The transmission-side terminal 10 transmits the acoustic signal x(t) in which the same sound source is picked up to the reception-side terminal 20 using both the session application and the call application. The reception-side terminal 20 receives the acoustic signal x(t) transmitted from each of the session application and the call application.

[0019] Specifically, the receiving terminal 20 receives the acoustic signal x(t) (hereinafter referred to as the received acoustic signal xN(t)) transmitted via a dedicated application. Also, it receives the acoustic signal x(t) (hereinafter referred to as the received acoustic signal xS(t)) transmitted via a general-purpose application.

[0020] Here, in the dedicated application, transmission is performed via the transmission path ND. In the general-purpose application, transmission is performed via the transmission path SD. Generally, the transmission paths of ND and SD are different. Therefore, at the receiving terminal 20, the received acoustic signal xN(t) and the received acoustic signal xS(t) are received at different timings.

[0021] Here, since in the dedicated application, transmission is performed with minimal delay, it is assumed that the received acoustic signal xN(t) is received by the receiving terminal 20 with less delay compared to the received acoustic signal xS(t). In this case, the received acoustic signal xN(t) is an example of the "first acoustic signal". The transmission path ND is an example of the "first transmission path". Also, the received acoustic signal xS(t) is an example of the "second acoustic signal". The transmission path SD is an example of the "second transmission path".

[0022] The receiving terminal 20 synchronizes and outputs two acoustic signals received at different timings. The receiving terminal 20 calculates the relative transmission delay amount between the two acoustic signals. In the following description, the transmission delay amount is simply referred to as the delay amount.

[0023] The receiving terminal 20 uses the calculated delay amount τ to generate a received acoustic signal xN(t - τ) obtained by delaying the received acoustic signal xN(t), which is the acoustic signal with less delay, by the delay amount τ. Then, instead of the received acoustic signal xS(t), the receiving terminal 20 outputs the received acoustic signal xN(t - τ) to the speaker 40. Thereby, it is possible to output high-quality sound in accordance with the timing at which the general-purpose application outputs sound on the receiving side. Therefore, it is possible to enable a call via the general-purpose application to be made with high-quality sound.

[0024] The transmitting terminal 10 is a computer device on the sender side, such as a smartphone, a personal computer, a mobile phone, a tablet terminal, a wearable terminal, etc. The transmitting terminal 10 includes, for example, a communication unit 11, a storage unit 12, a control unit 13, and an input / output unit 14.

[0025] The communication unit 11 communicates with the receiving terminal 20. For example, the communication unit 11 transmits the acoustic signal x(t) to the receiving terminal 20 according to the control of a dedicated application. Also, the communication unit 11 transmits the acoustic signal x(t) to the receiving terminal 20 according to the control of a general-purpose application.

[0026] The storage unit 12 is composed of a storage medium, for example, an HDD (Hard Disk Drive), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access read / write Memory), a ROM (Read Only Memory), or an arbitrary combination of these storage media. The storage unit 12 stores programs for executing various processes of the transmitting terminal 10 and temporary data used when performing various processes.

[0027] The control unit 13 realizes functions by a Processing Unit (such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit)) as hardware included in the transmitting terminal 10 executing the programs stored in the storage unit 12.

[0028] The control unit 13 includes, for example, a dedicated application 130, a general-purpose application 131, and a device control unit 132. The dedicated application 130 is a functional unit that realizes the functions of the general-purpose application, and transmits the acoustic signal x(t) acquired from the microphone 30 to a preset communication destination device (here, the receiving terminal 20). The general-purpose application 131 is a functional unit that realizes the functions of the general-purpose application, and transmits the acoustic signal x(t) acquired from the microphone 30 to a preset communication destination device (here, the receiving terminal 20). The device control unit 132 comprehensively controls the transmitting terminal 10. For example, the device control unit 132 outputs the acoustic signal x(t) input from the microphone 30 to the dedicated application 130 and the general-purpose application 131. Further, the device control unit 132 outputs, to the communication unit 11, a control signal for establishing communication with the communication destination device, which is output from the dedicated application 130 and the general-purpose application 131, so as to transmit it to the receiving terminal 20.

[0029] The input / output unit 14 is a functional unit that mediates the input / output of signals with external devices connected to the transmitting terminal 10. Here, the acoustic signal x(t) picked up by the microphone 30 is input to the input / output unit 14.

[0030] The receiving terminal 20 is a computer device on the receiver side, and is, for example, a smartphone, a personal computer, a mobile phone, a tablet terminal, a wearable terminal, or the like. Here, it is assumed that the receiving terminal 20 has the same configuration as the transmitting terminal 10. In the following description, only the functions of the receiving terminal 20 that are different from those of the transmitting terminal 10 will be described, and detailed descriptions of the functions equivalent to those of the transmitting terminal 10 may be omitted.

[0031] The receiving terminal 20 includes, for example, a communication unit 21, a storage unit 22, a control unit 23, and an input / output unit 24. The communication unit 21 communicates with the transmitting terminal 10. For example, the communication unit 21 receives the received acoustic signal xN(t) from the transmitting terminal 10. The communication unit 21 receives the received acoustic signal xS(t) from the transmitting terminal 10.

[0032] The storage unit 22 is composed of a storage medium, for example, an HDD, a flash memory, an EEPROM, a RAM, a ROM, or any combination of these storage media. The storage unit 22 stores programs for executing various processes of the receiving terminal 20 and temporary data used when performing various processes.

[0033] The control unit 23 realizes functions by a Processing Unit such as a CPU and a GPU as hardware provided in the receiving terminal 20 executing the programs stored in the storage unit 22.

[0034] The input / output unit 24 is a functional unit that mediates the input / output of signals with external devices connected to the receiving terminal 20. Here, the input / output unit 24 outputs the received acoustic signal xN(t - τ) to the speaker 40.

[0035] The control unit 23 includes, for example, a delay estimation unit 230, a delay unit 231, a device control unit 232, a dedicated application 233, and a general-purpose application 234. The delay estimation unit 230 is an example of a "delay amount calculation unit". The delay unit 231 is an example of a "delay amount addition unit". The device control unit 232 integrally controls the receiving terminal 20. The dedicated application 233 is a functional unit equivalent to the dedicated application 130. The general-purpose application 234 is a functional unit equivalent to the general-purpose application 131.

[0036] FIG. 2 is a diagram for explaining the processes performed by the control unit 23. The delay estimation unit 230 acquires the received acoustic signal xN(t) and the received acoustic signal xS(t), and calculates the relative delay amount τ between the two signals. The delay estimation unit 230 outputs the calculated delay amount τ to the delay unit 231.

[0037] The delay unit 231 generates a received acoustic signal xN(t - τ) obtained by delaying the received acoustic signal xN(t) using the delay amount τ acquired from the delay estimation unit 230, and outputs the generated received acoustic signal xN(t - τ).

[0038] Here, a specific method for the delay estimation unit 230 to calculate the delay amount will be described. The delay estimation unit 230, for example, buffers the received acoustic signal xN(t) for a period corresponding to a certain time interval (e.g., 1 second). That is, the delay estimation unit 230 sequentially stores the received acoustic signal xN(t) received by the communication unit 21, and temporarily stores the signal corresponding to a certain time interval, for example, in the storage unit 22.

[0039] Also, the delay estimation unit 230, for example, buffers the received acoustic signal xS(t) for a period corresponding to a certain time interval (e.g., 1 second). That is, the delay estimation unit 230 sequentially stores the received acoustic signal xS(t) received by the communication unit 21, and temporarily stores the signal corresponding to a certain time interval, for example, in the storage unit 22.

[0040] The delay estimation unit 230 calculates the cross-correlation value between the buffered received acoustic signal xN(t) for a certain time interval T and the received acoustic signal xS(t). For example, the delay estimation unit 230 calculates the cross-correlation value R using the following equation (1). In equation (1), R(n) represents the cross-correlation value when the delay amount is n. T represents a certain time interval. t represents time.

[0041]

Equation

[0042] For example, the delay estimation unit 230 calculates the cross-correlation value R(n) while changing n. The delay estimation unit 230 sets the delay amount n at which the absolute value |R(n)| is maximized among the calculated cross-correlation values R(n) as the relative delay amount between the received acoustic signal xN(t) and the received acoustic signal xS(t).

[0043] Further, as shown in the following equation (2), the delay estimation unit 230 may use the weighted sum of the cross-correlation values R´(n) as the cross-correlation value R(n). Here, the cross-correlation value R´(n) is the cross-correlation value obtained in the most recent (for example, the previous time interval). In equation (2), R´(n) represents the cross-correlation value when the delay amount is n and is the most recent cross-correlation value. T represents a fixed time interval. t represents time.

[0044] [Number]

[0045] Here, the delay amounts due to the transmission path ND and the transmission path SD do not always take a constant value and usually vary from moment to moment depending on the bandwidth situation, the complexity of the signals transmitted and received, etc. For this reason, even if the received acoustic signal xN(t) is delayed using the calculated delay amount, the synchronization between the received acoustic signal xN(t) and the received acoustic signal xS(t) may gradually become lost.

[0046] As a countermeasure against this, the delay estimation unit 230 appropriately updates the delay amount. For example, the delay estimation unit 230 calculates the delay amount each time a predetermined calculation timing arrives. The delay estimation unit 230 stores the calculated delay amounts, for example, as delay amounts n(1), n(2), …, n(N) in the storage unit 22. The arguments (1, 2, …, N) of the delay amount n indicate the calculation timings. The delay estimation unit 230 uses the delay amount n(k) obtained at each calculation timing k (k = 1 to N) as the delay amount at that time. Thereby, even when the delay amount related to transmission changes from moment to moment, it is possible to output the received acoustic signal xN(t) that follows the change.

[0047] Note that the calculation timing may be set arbitrarily. For example, the delay amount may be calculated each time the received acoustic signal xN(t) or the received acoustic signal xS(t) is received. Alternatively, the calculation timing may arrive every buffering time interval T (or 1 / 2T, 1 / 4T, etc.), or the calculation timing may arrive randomly.

[0048] In the above, each time the delay amount is calculated, the case where the received acoustic signal xN(t) is delayed by the calculated delay amount has been described as an example, but the present invention is not limited thereto. For example, the delay unit 231 may be configured to determine whether to delay the received acoustic signal xN(t) by the calculated delay amount, that is, whether to update the delay amount, based on the delay amount calculated by the delay estimation unit 230.

[0049] For example, the delay unit 231 acquires a reference value nf which is a reference delay amount stored in advance in the storage unit 22 or the like. The delay unit 231 determines whether to update the delay amount of the received acoustic signal xN(t) by the calculated delay amount n(k) using the acquired reference value nf and the calculated delay amount n(k). For example, when the absolute value |nf - n(k)| of the difference between the reference value nf and the delay amount n(k) is equal to or greater than a predetermined threshold value (tolerance range described later), the delay unit 231 determines to update the delay amount. When the absolute value |nf - n(k)| is less than the predetermined threshold value, the delay unit 231 determines not to update the delay amount. Alternatively, when the absolute value |nf - n(k)| is less than the predetermined threshold value, the delay unit 231 may set the delay amount to the reference value nf.

[0050] In other words, the delay unit 231 determines to update the delay amount when the delay amount n(k) is greater than (reference value nf + tolerance range) or less than (reference value nf - tolerance range). When the delay amount n(k) is less than (reference value nf + tolerance range) and greater than (reference value nf - tolerance range), the delay unit 231 determines not to update the delay amount. In this case, (reference value nf + tolerance range) is an example of the "first threshold value". Thereby, the delay amount can be updated only when the calculated delay amount n(k) exceeds the tolerance range from the currently set value. Therefore, it is possible to suppress a change in the minute delay amount and reduce the occurrence of an acoustic discomfort, while following the change in the actual delay amount.

[0051] In the above description, the case where the reference value nf is a fixed value was described as an example. However, it is not limited to this. The reference value nf may be a variable value. The delay estimation unit 230 may, for example, set the reference value nf as the average of the delay amounts n(1), n(2), …, n(N) calculated at each calculation timing. The average may be a simple arithmetic mean value from calculation timings 1 to N, or a weighted average value. Alternatively, it may be a recent moving average. The recent moving average means that when the latest delay amount is n(N), it is the average value of the delay amount n(N) and a plurality of recent delay amounts (for example, the delay amounts n(N - 1), n(N - 2) at calculation timings N - 1, N - 2).

[0052] Also, when the delay unit 231 updates (changes) the delay amount, it may change the delay amount step by step so that the change is smooth. For example, when the delay unit 231 updates the delay amount, first, it calculates the difference between the current delay amount and the updated delay amount as the change amount. The delay unit 231 ensures that the change speed (change amount per unit time) does not exceed a predetermined threshold based on the calculated change amount. Thereby, the delay unit 231 can gradually change the delay amount and suppress the occurrence of sound dropout and sound skipping.

[0053] Note that in the above description, the case where the delay estimation unit 230 sets the delay amount n when the peak value (maximum value) of the absolute value |R(n)| of the cross-correlation value is used as the relative delay amount between the received acoustic signal xN(t) and the received acoustic signal xS(t) was described as an example.

[0054] However, when an acoustic signal close to silence is transmitted, for example, the overall signal amplitude of the received acoustic signal is smaller compared to the case when it is not silent. In this case, a prominent peak value does not appear in the cross-correlation value R(n), and it is conceivable that the cross-correlation value takes a similar value regardless of the value of the delay amount n. In such a case, the value of n at which the cross-correlation value R(n) is maximized is likely to be unreliable as the actual delay amount.

[0055] As a countermeasure, when the peak value of the cross-correlation value R(n) is less than a predetermined threshold, the delay estimation unit 230 determines not to adopt the corresponding delay amount n as the actual delay amount. That is, when the peak value of the cross-correlation value R(n) is equal to or greater than the predetermined threshold, the delay estimation unit 230 adopts the corresponding delay amount n as the actual delay amount. Thereby, the delay estimation unit 230 can accurately calculate the delay amount.

[0056] Also, for some reason, the transmission of a signal through either the transmission path SD or the transmission path ND may be interrupted. In such a case, the delay amount calculated using the cross-correlation value R(n) cannot be trusted. As a countermeasure, the delay estimation unit 230 determines whether the transmission path is interrupted, and if it is determined that either one of the transmission paths is interrupted, the calculation of the cross-correlation value R(n) is not performed.

[0057] For example, the delay estimation unit 230 calculates the power (maximum level) of each of the buffered received acoustic signal xS(t) and the received acoustic signal xN(t). The power here is an index indicating the strength of the buffered signal. The power may be, for example, the sum of the absolute values of the signal amplitudes in the buffered signal, or the signal amplitude value of the signal having the maximum absolute value of the signal amplitudes among the buffered signals.

[0058] When one of the calculated powers of the received acoustic signal xS(t) and the received acoustic signal xN(t) exceeds a predetermined threshold and the other is below the threshold, the delay estimation unit 230 determines that the transmission path of the one that is below the threshold is interrupted. The threshold here is an example of the "second threshold".

[0059] Specifically, when the power of the received acoustic signal xN(t) is less than the threshold value and the power of the received acoustic signal xS(t) is equal to or greater than the threshold value, the delay estimation unit 230 determines not to calculate the cross-correlation value R(n) and not to calculate the delay amount. Further, when the power of the received acoustic signal xN(t) is equal to or greater than the threshold value and the power of the received acoustic signal xS(t) is less than the threshold value, the delay estimation unit 230 determines not to calculate the cross-correlation value R(n) and not to calculate the delay amount.

[0060] In addition, when the delay estimation unit 230 determines that the transmission of the signal through either one of the transmission paths SD or ND is interrupted, it may reproduce the acoustic signal of the non-interrupted side. Specifically, when the power of the received acoustic signal xN(t) is less than the threshold value and the power of the received acoustic signal xS(t) is equal to or greater than the threshold value, the delay estimation unit 230 causes the received acoustic signal xS(t) to be output to the speaker 40 via the input / output unit 24. Further, when the power of the received acoustic signal xN(t) is equal to or greater than the threshold value and the power of the received acoustic signal xS(t) is less than the threshold value, the delay estimation unit 230 causes the received acoustic signal xN(t - τ) to be output to the speaker 40 via the input / output unit 24. The delay amount τ here is the currently set delay amount. Thereby, the delay estimation unit 230 can continue the reproduction of the sound even when one of the transmission paths is interrupted.

[0061] FIG. 3 is a sequence diagram showing the processing flow of the transmission system 1 in the first embodiment. The transmitting terminal 10 acquires the acoustic signal x(t) from the microphone 30 (step S10). The transmitting terminal 10 transmits the acoustic signal x(t) to the receiving terminal 20 by means of each of the dedicated application and the general-purpose application (step S11). The acoustic signal x(t) transmitted via the dedicated application reaches the receiving terminal 20 as the received acoustic signal xN(t) through the transmission path ND. The acoustic signal x(t) transmitted via the general-purpose application reaches the receiving terminal 20 as the received acoustic signal xS(t) through the transmission path SD.

[0062] The receiving terminal 20 receives the received acoustic signal xN(t) (step S12). The receiving terminal 20 receives the received acoustic signal xS(t) (step S13). The receiving terminal 20 estimates (calculates) the delay amount τ using the received received acoustic signal xN(t) and the received acoustic signal xS(t) (step S14). The receiving terminal 20 delays the received acoustic signal xN(t) using the estimated delay amount τ, and outputs the delayed received acoustic signal xN(t−τ) to the speaker 40 (step S16).

[0063] As described above, the transmission method by the transmission system 1 of the first embodiment is a transmission method of the received acoustic signal xN(t) and the received acoustic signal xS(t) in which the acoustic signal x(t) that is the same sound source is picked up. The transmission method is an example of a "signal processing method". The received acoustic signal xN(t) is an example of a "first acoustic signal". The received acoustic signal xS(t) is an example of a "second acoustic signal".

[0064] In the transmission method by the transmission system 1, the communication unit 21 receives the received acoustic signal xN(t) transmitted via the transmission path ND. The communication unit 21 is an example of a "first receiving unit". The transmission path ND is an example of a "first transmission path". The communication unit 21 receives the received acoustic signal xS(t) transmitted via the transmission path SD. The communication unit 21 is an example of a "second receiving unit". The transmission path SD is a transmission path in which the delay time related to transmission is larger than that of the transmission path ND, and is an example of a "second transmission path". The delay estimation unit 230 calculates the relative delay amount τ between the received acoustic signal xN(t) and the received acoustic signal xS(t). The delay estimation unit 230 is an example of a "delay amount calculation unit". The delay amount τ is an example of a "transmission delay amount". The delay unit 231 delays the received acoustic signal xN(t) based on the calculated delay amount τ, and outputs the delayed received acoustic signal xN(t−τ).

[0065] Thereby, in the transmission system 1 of the first embodiment, high-quality sound can be output at a timing synchronized with the sound output from the general-purpose application. Therefore, high-quality sound can be transmitted using a generally popular call application.

[0066] Also, in the transmission method by the transmission system 1 of the first embodiment, the delay estimation unit 230 calculates the delay amount τ every time a predetermined calculation timing k arrives. Every time the delay amount τ is calculated, the delay unit 231 delays the received acoustic signal xN(t) by the delay amount τ calculated this time. The delay unit 231 outputs the delayed received acoustic signal xN(t−τ). Thus, in the transmission method by the transmission system 1 of the embodiment, even when the delay amount changes moment by moment, it is possible to follow the change and continuously output the received acoustic signal xN(t) synchronized with the received acoustic signal xS(t).

[0067] Also, in the transmission method by the transmission system 1 of the first embodiment, every time the delay amount is calculated, the delay unit 231 determines whether or not the delay amount τ calculated this time is equal to or greater than a threshold value (first threshold value). When the delay amount τ calculated this time is equal to or greater than the threshold value, the delay unit 231 delays the received acoustic signal xN(t) by the delay amount τ calculated this time. The delay unit 231 outputs the delayed received acoustic signal xN(t−τ). Thus, when a large change occurs in the delay amount, it is possible to follow the change.

[0068] Also, in the transmission method by the transmission system 1 of the first embodiment, every time the delay amount τ is calculated, the delay unit 231 determines whether or not the delay amount τ calculated this time is equal to or greater than a threshold value (first threshold value). When the delay amount τ calculated this time is not equal to or greater than the threshold value, the delay unit 231 delays the received acoustic signal xN(t) by a predetermined delay amount (for example, a reference value nf). The delay unit 231 outputs the delayed received acoustic signal xN(t−nf). Thus, it is possible to suppress a change in a minute delay amount and reduce the occurrence of an acoustic discomfort.

[0069] Also, in the transmission method by the transmission system 1 of the first embodiment, the threshold value (first threshold value) is the average of the delay amounts n(k) calculated each time a predetermined calculation timing k arrives. As a result, when there is a large change in the delay amount calculated this time compared to the average of the previous delay amounts, it follows that change, and when the delay amount calculated this time is of the same level as the previous delay amounts, the delay amount can be maintained as it is as a minute change. Therefore, an effect similar to the above-described effect can be achieved.

[0070] Also, in the transmission method by the transmission system 1 of the first embodiment, each time the delay amount τ is calculated, the delay unit 231 delays the received acoustic signal xN(t) step by step based on the previously calculated delay amount and the currently calculated delay amount. Thereby, the delay amount can be gradually changed, and it is possible to suppress the occurrence of sound dropout, skipped sound, and the like.

[0071] Also, in the transmission method by the transmission system 1 of the first embodiment, the delay estimation unit 230 calculates the delay amount n at which the cross-correlation value R(n) between the time-series change of the received acoustic signal xN(t) and the time-series change of the received acoustic signal xS(t) received in a predetermined time interval T becomes maximum. When the calculated delay amount is equal to or greater than a threshold value (second threshold value), the delay estimation unit 230 sets the calculated delay amount n as the delay amount τ. Thereby, when the calculated delay amount is not reliable, such as when a silent state continues, it is possible to prevent the unreliable delay amount from being applied.

[0072] Also, in the transmission method by the transmission system 1 of the first embodiment, when the calculated delay amount is equal to or greater than a threshold value (second threshold value), the delay estimation unit 230 sets the calculated delay amount n as the delay amount τ. When the calculated delay amount is less than the threshold value (second threshold value), the delay estimation unit 230 does not set the calculated delay amount n as the delay amount τ. Thereby, when the calculated delay amount is not reliable, such as when a silent state continues, it is possible to prevent the unreliable delay amount from being applied.

[0073] Also, in the transmission method by the transmission system 1 of the first embodiment, when the maximum level of the received acoustic signal xN(t) received in a predetermined time interval T is equal to or greater than a threshold value (second threshold value) and the maximum level of the received acoustic signal xS(t) is less than the threshold value (second threshold value), the delay amount is not calculated. The delay estimation unit 230 does not calculate the delay amount when the maximum level of the received acoustic signal xN(t) received in a predetermined time interval T is less than the threshold value (second threshold value) and the maximum level of the received acoustic signal xS(t) is equal to or greater than the threshold value (second threshold value). Thereby, when the calculated delay amount is not reliable, such as when one of the transmission paths is interrupted, it is possible to prevent the unreliable delay amount from being applied.

[0074] (Second Embodiment) Next, the second embodiment will be described. In this embodiment, it is different from the above-described embodiment in that a video signal y(t) is transmitted together with the acoustic signal x(t) by a general-purpose application.

[0075] FIG. 4 is a block diagram showing a configuration example of a transmission system 1A according to the second embodiment. In the transmission system 1A, a camera 50 is connected to the transmission-side terminal 10. Also, in the transmission system 1, a display 60 is connected to the reception-side terminal 20.

[0076] The transmission-side terminal 10 acquires the acoustic signal x(t) from the microphone 30 via the input / output unit 14. Also, the transmission-side terminal 10 acquires the video signal y(t) from the camera 50 via the input / output unit 14. The transmission-side terminal 10 transmits the acoustic signal x(t) via the dedicated application to the reception-side terminal 20 by the dedicated application 130. Also, the transmission-side terminal 10 transmits the acoustic signal x(t) and the video signal y(t) via the general-purpose application to the reception-side terminal 20 by the general-purpose application 131.

[0077] The receiving terminal 20 receives the received acoustic signal xN(t) via the transmission line ND. Also, the receiving terminal 20 receives the received acoustic signal xS(t) and the received video signal yS(t) via the transmission line SD. The delay estimation unit 230 of the received acoustic signal xN(t) calculates the relative delay amount τ between the received acoustic signal xN(t) and the received acoustic signal xS(t). The receiving terminal 20 outputs the received acoustic signal xN(t - τ) delayed by the calculated delay amount τ to the speaker 40 via the input / output unit 24. The receiving terminal 20 outputs the received video signal yS(t) to the display 60 via the input / output unit 24.

[0078] FIG. 5 is a sequence diagram showing the processing flow of the transmission system 1A according to the second embodiment. The transmitting terminal 10 acquires the acoustic signal x(t) from the microphone 30 and acquires the video signal y(t) from the camera 50 (step S20). The transmitting terminal 10 transmits the acoustic signal x(t) to the receiving terminal 20 by a dedicated application and transmits the acoustic signal x(t) and the video signal y(t) to the receiving terminal 20 by a general-purpose application (step S21). The acoustic signal x(t) via the dedicated application reaches the receiving terminal 20 as the received acoustic signal xN(t) via the transmission line ND. The acoustic signal x(t) and the video signal y(t) via the general-purpose application reach the receiving terminal 20 as the received acoustic signal xS(t) and the received video signal yS(t) via the transmission line SD.

[0079] The receiving terminal 20 receives the received acoustic signal xN(t) (step S22). The receiving terminal 20 receives the received acoustic signal xS(t) and the received video signal yS(t) (step S23). The receiving terminal 20 estimates (calculates) the delay amount τ using the received received acoustic signal xN(t) and the received acoustic signal xS(t) (step S24). The receiving terminal 20 delays the received acoustic signal xN(t) using the estimated delay amount τ, outputs the delayed received acoustic signal xN(t - τ) to the speaker 40, and outputs the received video signal yS(t) to the display 60 (step S26).

[0080] As described above, the transmission method by the transmission system 1A of the second embodiment is a transmission method for the received acoustic signal xN(t) and the received acoustic signal xS(t) which are acoustic signals from the same sound source.

[0081] In the transmission method by the transmission system 1A, the communication unit 21 receives the received acoustic signal xN(t) transmitted via the transmission path ND. The communication unit 21 receives the received acoustic signal xS(t) and the received video signal yS(t) transmitted via the transmission path SD. The delay estimation unit 230 calculates the relative delay amount τ between the received acoustic signal xN(t) and the received acoustic signal xS(t). The delay unit 231 delays the received acoustic signal xN(t) based on the calculated delay amount τ, and outputs the delayed received acoustic signal xN(t - τ).

[0082] Thereby, in the transmission system 1A of the second embodiment, high-quality sound can be reproduced in synchronization with the video transmitted by the general-purpose application. Therefore, high-quality sound can be transmitted using a generally popular call application.

Industrial Applicability

[0083] According to the embodiments exemplified above, a transmission system applicable to online music lessons and the like can be provided.

Explanation of Reference Numerals

[0084] 1... Transmission system, 10... Transmitting terminal, 11... Communication unit, 12... Storage unit, 13... Control unit 13, 130... Dedicated application, 131... General-purpose application, 20... Receiving terminal (signal processing device), 21... Communication unit, 22... Storage unit, 23... Control unit, 230... Delay estimation unit (delay amount calculation unit), 231... Delay unit (delay imparting unit), 30... Microphone, 40... Speaker, 50... Camera, 60... Display

Claims

1. A signal processing method for a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, the signal processing method comprising: a first receiving unit receiving the first acoustic signal transmitted via a first transmission path; a second receiving unit receives the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is longer than the first transmission path and different from the first transmission path; a delay amount calculation unit calculates a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit delays the first acoustic signal based on the transmission delay amount, and outputs the delayed first acoustic signal in place of the second acoustic signal. Signal processing methods.

2. A signal processing method for a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, the signal processing method comprising: a first receiving unit receiving the first acoustic signal transmitted via a first transmission path; a second receiving unit receives the second acoustic signal transmitted together with the video signal via a second transmission path having a delay time related to transmission that is longer than the first transmission path and different from the first transmission path; a delay amount calculation unit calculates a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit delays the first acoustic signal based on the transmission delay amount, and outputs the delayed first acoustic signal in place of the second acoustic signal. Signal processing methods.

3. The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit delays the first acoustic signal by the currently calculated transmission delay amount every time the transmission delay amount is calculated, and outputs the delayed first acoustic signal.

3. The signal processing method according to claim 1.

4. The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit determines whether the currently calculated transmission delay amount is equal to or greater than a first threshold each time the transmission delay amount is calculated, and if the currently calculated transmission delay amount is equal to or greater than the first threshold, delays the first acoustic signal by the currently calculated transmission delay amount and outputs the delayed first acoustic signal.

3. The signal processing method according to claim 1.

5. A signal processing method for a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, the signal processing method comprising: a first receiving unit receiving the first acoustic signal transmitted via a first transmission path; a second receiving unit receives the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is longer than the first transmission path and different from the first transmission path; a delay amount calculation unit calculates a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit determines whether the currently calculated transmission delay amount is equal to or greater than a first threshold each time the transmission delay amount is calculated, and if the currently calculated transmission delay amount is not equal to or greater than the first threshold, delays the first acoustic signal by a predetermined delay amount and outputs the delayed first acoustic signal. Signal processing methods.

6. A signal processing method for a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, the signal processing method comprising: a first receiving unit receiving the first acoustic signal transmitted via a first transmission path; a second receiving unit receives the second acoustic signal transmitted together with the video signal via a second transmission path having a delay time related to transmission that is longer than the first transmission path and different from the first transmission path; a delay amount calculation unit calculates a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit determines whether the currently calculated transmission delay amount is equal to or greater than a first threshold each time the transmission delay amount is calculated, and if the currently calculated transmission delay amount is not equal to or greater than the first threshold, delays the first acoustic signal by a predetermined delay amount and outputs the delayed first acoustic signal. Signal processing methods.

7. The first threshold is an average of the transmission delay amounts calculated each time a predetermined calculation timing arrives. The signal processing method according to any one of claims 4 to 6.

8. The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit, each time the transmission delay amount is calculated, delays the first acoustic signal in a stepwise manner based on the previously calculated transmission delay amount and the currently calculated transmission delay amount, and outputs the delayed first acoustic signal. The signal processing method according to any one of claims 1 to 6.

9. A signal processing method for a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, the signal processing method comprising: a first receiving unit receiving the first acoustic signal transmitted via a first transmission path; a second receiving unit receives the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is longer than the first transmission path and different from the first transmission path; a delay amount calculation unit calculates a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; the delay amount calculation unit calculates a delay amount at which a cross-correlation value between a time series change in the first acoustic signal and a time series change in the second acoustic signal received in a predetermined time section is maximized, and when the calculated delay amount is equal to or greater than a second threshold value, the calculated delay amount is set as the transmission delay amount. Signal processing methods.

10. A signal processing method for a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, the signal processing method comprising: a first receiving unit receiving the first acoustic signal transmitted via a first transmission path; a second receiving unit receives the second acoustic signal transmitted together with the video signal via a second transmission path having a delay time related to transmission that is longer than the first transmission path and different from the first transmission path; a delay amount calculation unit calculates a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; the delay amount calculation unit calculates a delay amount at which a cross-correlation value between a time series change in the first acoustic signal and a time series change in the second acoustic signal received in a predetermined time section is maximized, and when the calculated delay amount is equal to or greater than a second threshold value, the calculated delay amount is set as the transmission delay amount. Signal processing methods.

11. the delay amount calculation unit does not calculate the transmission delay amount when a maximum level of the first acoustic signal received in a predetermined time period is less than the second threshold and a maximum level of the second acoustic signal is equal to or greater than the second threshold. The signal processing method according to claim 9 or 10.

12. the delay amount calculation unit does not calculate the transmission delay amount when a maximum level of the first acoustic signal received in a predetermined time period is equal to or greater than the second threshold and a maximum level of the second acoustic signal is less than the second threshold. The signal processing method according to claim 9 or 10.

13. A signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, a first receiving unit that receives the first acoustic signal transmitted via a first transmission path; a second receiving unit that receives the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation unit that calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal instead of the second acoustic signal; A signal processing device comprising:

14. A signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, a first receiving unit that receives the first acoustic signal transmitted via a first transmission path; a second receiving unit that receives the second acoustic signal transmitted together with the video via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation unit that calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal instead of the second acoustic signal; A signal processing device comprising:

15. The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit delays the first acoustic signal by the currently calculated transmission delay amount every time the transmission delay amount is calculated, and outputs the delayed first acoustic signal. The signal processing device according to claim 13 or 14.

16. The delay amount calculation unit calculates the transmission delay amount every time a predetermined calculation timing arrives, the delay amount adding unit determines whether the currently calculated transmission delay amount is equal to or greater than a first threshold each time the transmission delay amount is calculated, and if the currently calculated transmission delay amount is equal to or greater than the first threshold, delays the first acoustic signal by the currently calculated transmission delay amount and outputs the delayed first acoustic signal. The signal processing device according to claim 13 or 14.

17. A signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, a first receiving unit that receives the first acoustic signal transmitted via a first transmission path; a second receiving unit that receives the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation unit that calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; Equipped with The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit determines whether the currently calculated transmission delay amount is equal to or greater than a first threshold each time the transmission delay amount is calculated, and if the currently calculated transmission delay amount is not equal to or greater than the first threshold, delays the first acoustic signal by a predetermined delay amount and outputs the delayed first acoustic signal. Signal processing device.

18. A signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, a first receiving unit that receives the first acoustic signal transmitted via a first transmission path; a second receiving unit that receives the second acoustic signal transmitted together with the video via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation unit that calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; Equipped with The delay amount calculation unit calculates the transmission delay amount each time a predetermined calculation timing arrives, the delay amount adding unit determines whether the currently calculated transmission delay amount is equal to or greater than a first threshold each time the transmission delay amount is calculated, and if the currently calculated transmission delay amount is not equal to or greater than the first threshold, delays the first acoustic signal by a predetermined delay amount and outputs the delayed first acoustic signal. Signal processing device.

19. The first threshold is an average of the transmission delay amounts calculated each time a predetermined calculation timing arrives. A signal processing device according to any one of claims 16 to 18.

20. The delay amount calculation unit calculates the transmission delay amount every time a predetermined calculation timing arrives, the delay amount adding unit, each time the transmission delay amount is calculated, delays the first acoustic signal in a stepwise manner based on the previously calculated transmission delay amount and the currently calculated transmission delay amount, and outputs the delayed first acoustic signal. The signal processing device according to any one of claims 13, 14, and 16 to 19.

21. A signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, a first receiving unit that receives the first acoustic signal transmitted via a first transmission path; a second receiving unit that receives the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation unit that calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; Equipped with the delay amount calculation unit calculates a delay amount at which a cross-correlation value between a time series change in the first acoustic signal and a time series change in the second acoustic signal received in a predetermined time period is maximized, and when the calculated delay amount is equal to or greater than a second threshold value, the calculated delay amount is set as the transmission delay amount. Signal processing device.

22. A signal processing device that performs signal processing on a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal, a first receiving unit that receives the first acoustic signal transmitted via a first transmission path; a second receiving unit that receives the second acoustic signal transmitted together with the video via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation unit that calculates a transmission delay amount, which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding unit that delays the first acoustic signal based on the transmission delay amount and outputs the delayed first acoustic signal; Equipped with the delay amount calculation unit calculates a delay amount at which a cross-correlation value between a time series change in the first acoustic signal and a time series change in the second acoustic signal received in a predetermined time period is maximized, and when the calculated delay amount is equal to or greater than a second threshold value, the calculated delay amount is set as the transmission delay amount. Signal processing device.

23. the delay amount calculation unit does not calculate the transmission delay amount when a maximum level of the first acoustic signal received in a predetermined time period is less than the second threshold and a maximum level of the second acoustic signal is equal to or greater than the second threshold. A signal processing device according to claim 21 or 22.

24. the delay amount calculation unit does not calculate the transmission delay amount when a maximum level of the first acoustic signal received in a predetermined time period is equal to or greater than the second threshold and a maximum level of the second acoustic signal is less than the second threshold. A signal processing device according to claim 21 or 22.

25. a signal processing device that processes a first acoustic signal and a second acoustic signal obtained by collecting a same sound source, the first acoustic signal being transmitted via a transmission path having less delay than the second acoustic signal; a first receiving step of receiving the first acoustic signal transmitted via a first transmission path; a second receiving step of receiving the second acoustic signal transmitted via a second transmission path having a delay time related to transmission that is greater than the first transmission path and different from the first transmission path; a delay amount calculation step of calculating a transmission delay amount which is a relative delay amount between the first acoustic signal and the second acoustic signal; a delay amount adding step of delaying the first acoustic signal based on the transmission delay amount and outputting the delayed first acoustic signal instead of the second acoustic signal; A program for executing the above.

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