JP7672217B2 - Audio signal processing device, audio signal processing program - Google Patents

Description

The present invention relates to an audio signal processing device and an audio signal processing program that upmixes audio signals while suppressing degradation of sound quality.

In recent years, with the realization of 4K and 8K broadcasting, there is an increasing demand to upmix stereo (2ch) audio formats to generate 22.2ch surround audio formats that are compatible with 5.1ch surround and 3D audio. In live broadcasts, 4K and 8K broadcasts can be carried out simultaneously with 2K broadcasts by generating 5.1ch surround and 22.2ch surround audio formats from stereo audio formats in real time.

As a specific method of upmixing, as described in Patent Document 1, a stereo sound source is separated into direct sound and indirect sound for each of the left and right sides, and various processes such as delay processing are performed on these four sound sources to output each channel in surround. In addition, in the technology described in Patent Document 2, a method is also known in which a stereo sound source is separated into direct sound and indirect sound for each of the left and right sides, and then upmixed using HRIR. Note that as a method of separating a stereo sound source into direct sound and indirect sound, a method of extracting coherent components from a stereo sound source is superior as described in Patent Document 3.

JP 2015-076857 A JP 2017-163458 A International Publication No. 2017/188141

However, in Patent Documents 1 and 2, after separating the stereo sound source, delay processing and filter processing associated with HRIR are performed, which causes distortion in the original sound source. In particular, in recent years, there has been a demand for downmixing a surround sound source generated by upmixing a stereo sound source back into a stereo sound source. However, if distortion occurs in the original sound source during upmixing, this distortion remains when downmixed to a stereo sound source. In addition, Patent Document 2 requires a reference HRIR, which is difficult to obtain.

The present invention aims to solve the above problem by providing an audio signal processing device that can upmix stereo sound sources without causing distortion.

The audio signal processing device of the present invention has the following configuration.
(1) An audio signal processing device that upmixes a stereo sound source into a surround sound source.
(2) A separation unit that separates the stereo sound source into direct sound and indirect sound.
(3) A setting unit that generates a parameter for adjusting at least one of the direct sound and the indirect sound.
(4) A coefficient generating unit that generates a coefficient by which the direct sound and the indirect sound are multiplied for each channel in the surround sound source based on the parameters.
(5) A calculation unit that upmixes the stereo sound source to the surround sound source by multiplying the direct sound and the indirect sound by the coefficient.

The audio signal processing device of the present invention may further include the following configuration.
(1) The parameters include parameters for adjusting the balance between a center sound source and a sound source other than the center sound source in a front channel of the surround sound source.
(2) The parameters include parameters for adjusting the balance between a center sound source and a sound source other than the center sound source in a rear channel of the surround sound source.
(3) The parameters include parameters for adjusting a mixing amount of the indirect sound with respect to the direct sound output from a front channel of the surround sound source.
(4) The surround sound source corresponds to 3D audio, and the parameters include parameters for adjusting the balance between the direct sound and the indirect sound output from a middle layer channel in the surround sound source and the direct sound and the indirect sound output from upper and lower layer channels.
(5) The parameters include parameters for adjusting the balance between the direct sound and the indirect sound.
(6) The setting unit includes a direct sound/indirect sound balance adjustment unit that adjusts the balance between the direct sound and the indirect sound.

The audio signal processing program of the present invention has the following configuration.
(1) An audio signal processing program that causes a computer to execute a process of upmixing a stereo sound source into a surround sound source.
(2) A separation procedure for separating the stereo sound source into direct sound and indirect sound.
(3) A setting procedure for generating parameters for adjusting at least one of the direct sound or the indirect sound.
(4) A coefficient generating step of generating a coefficient by which the direct sound and the indirect sound are multiplied for each channel in the surround sound source based on the parameters.
(5) A calculation procedure for upmixing the stereo sound source to the surround sound source by multiplying the direct sound and the indirect sound by the coefficient.

The present invention makes it possible to upmix stereo sound sources without causing distortion.

1 is a block diagram showing a configuration of an audio signal processing device according to an embodiment; FIG. 2 is a block diagram showing in detail a portion of the configuration of the audio signal processing device according to the embodiment. 5A and 5B are diagrams showing the operation of a direct sound/indirect sound balance adjustment unit according to the embodiment. 6A to 6C are diagrams illustrating the operation of the front balance adjustment unit according to the embodiment. 5A to 5C are diagrams illustrating the operation of the rear balance adjuster according to the embodiment. 5A and 5B are diagrams illustrating the operation of a mixing amount adjustment unit according to the embodiment. 6A to 6C are diagrams illustrating the operation of an interlayer balance adjustment unit according to an embodiment. FIG. 4 is a diagram showing the operation of a calculation unit according to the embodiment. 4 is a flowchart showing the operation of the audio signal processing device according to the embodiment. FIG. 11 is a block diagram showing in detail a portion of the configuration of an audio signal processing device according to another embodiment.

[First embodiment]
[composition]
The audio signal processing device 100 of the present embodiment shown in FIG. 1 is known as, for example, an audio mixing console or a mixer. In the following description, an upmix from stereo to 22.2ch surround is taken as an example, and the audio signal input to the audio signal processing device 100 is a stereo sound source. The 22.2ch surround is composed of 24 channels, 1 to 24. Specifically, it is composed of 9 channels in the upper layer, 10 channels in the middle layer, and 3.2 channels in the lower layer. The 3.2 channels in the lower layer include two LFEs. The 22.2ch surround can also be considered as being divided into 11.2 channels on the front side and 11 channels on the side and rear sides. For ease of explanation, it is considered that direct sound is mainly output from the front side channel, and indirect sound is mainly output from the side side channel and the rear side channel, but the indirect sound may be output from the front side channel.

The audio signal processing device 100 includes a separation unit 10 that separates a stereo sound source into a direct sound and an indirect sound for each of the left and right, a setting unit 20 that generates various parameters for adjusting the separated sound source, a coefficient generation unit 30 that generates coefficients based on the generated parameters, and a calculation unit 40 that generates an upmixed surround sound source from the coefficients and the separated sound source.

The separation unit 10 separates the stereo sound source into direct sound and indirect sound for each of the left and right sides. That is, the sound is separated into four sound sources: left direct sound DL, right direct sound DR, left indirect sound RL, and right indirect sound RR. Well-known techniques such as the technique of Patent Document 3 described in the background art can be used to separate the stereo sound source into direct sound and indirect sound. The separation unit 10 outputs these four sound sources to the calculation unit 40 provided in the subsequent stage. Note that direct sound is sound that reaches the ear directly, and indirect sound is sound that reaches the ear after being reflected off a wall or the like.

The setting unit 20 generates parameters for adjusting the four sound sources separated by the separation unit 10. As shown in FIG. 2, the setting unit 20 includes a direct sound/indirect sound balance adjustment unit 21 that adjusts the balance between direct sound and indirect sound, a front balance adjustment unit 22 that adjusts the balance between the center sound source and sound sources other than the center sound source in the direct sound, a rear balance adjustment unit 23 that adjusts the balance between the center sound source and sound sources other than the center sound source in the indirect sound, a mixing amount adjustment unit 24 that adjusts the mixing amount of the direct sound and the indirect sound, and an interlayer balance adjustment unit 25 that adjusts the balance between the output from the mid-layer channel and the output from the upper and lower layer channels in the direct sound and indirect sound.

As shown in FIG. 3, the direct sound/indirect sound balance adjustment unit 21 has, for example, one operator, and rotating this operator to the left increases the mixing amount of direct sound, and rotating it to the right increases the mixing amount of indirect sound. By rotating this operator left and right, the mixing engineer adjusts the balance between direct sound and indirect sound in the surround sound source after upmixing. The degree of this adjustment is output as a ROOM value to the calculation unit 40 provided at the subsequent stage.

As shown in FIG. 4, the front balance adjustment unit 22 adjusts the balance between the center sound source and sound sources other than the center sound source among the direct sound. This center sound source is a component of the direct sound that is localized in the center. Also, this sound source other than the center sound source is a component of the direct sound other than the center sound source. The front balance adjustment unit 22 has, for example, one operator, and rotating this operator to the left increases the mixing amount of the center sound source, and rotating it to the right increases the mixing amount of the sound sources other than the center sound source. By rotating this operator to the left and right, the mixing engineer adjusts the balance between the center sound source output from the front side channel and the sound sources other than the center sound source in the surround sound source after upmixing. The degree of this adjustment is output as an Fdiv value to the coefficient generation unit 30 provided at the subsequent stage.

As shown in FIG. 5, the rear balance adjustment unit 23 adjusts the balance between the center sound source and sound sources other than the center sound source among the indirect sound. This center sound source is a component of the indirect sound that is localized in the center. Also, this sound source other than the center sound source is a component of the indirect sound other than the center sound source. The rear balance adjustment unit 23 has, for example, one operator, and rotating this operator to the left increases the mixing amount of the center sound source, and rotating it to the right increases the mixing amount of the sound sources other than the center sound source. By rotating this operator to the left and right, the mixing engineer adjusts the balance between the center sound source output from the rear channel and the sound sources other than the center sound source in the surround sound source after upmixing. The degree of this adjustment is output as an Rdiv value to the coefficient generation unit 30 provided at the subsequent stage.

As shown in FIG. 6, the mixing amount adjustment unit 24 adjusts the mixing ratio of the indirect sound to the direct sound output from the front channel, and the mixing ratio of the direct sound to the indirect sound output from the rear channel. To this end, the mixing amount adjustment unit 24 includes, for example, a main operator X and a sub-operator Y.

The main operator X adjusts the balance between the direct sound output from the front channel and the indirect sound. For example, rotating the main operator X to the left decreases the mixing amount of the direct sound and the indirect sound, and rotating it to the right increases the mixing amount of the direct sound and the indirect sound. On the other hand, the sub-operator Y adjusts the amount of direct sound mixed with the indirect sound and the amount of indirect sound mixed with the direct sound output from the front channel. For example, rotating the sub-operator Y to the left decreases the amount of direct sound mixed with the indirect sound and the amount of indirect sound mixed with the direct sound, and rotating it to the right increases the amount of direct sound mixed with the indirect sound and the amount of indirect sound mixed with the direct sound. The mixing engineer adjusts the mixing ratio of the indirect sound to the direct sound output from the front channel and the mixing ratio of the direct sound to the indirect sound by rotating the main operator X and the sub-operator Y. The main operator X and the sub-operator Y may be linked, or the main operator X may be fixed and only the sub-operator Y may rotate. When linking them, it is preferable to rotate the sub-operator Y in the opposite direction to the rotation direction of the main operator X. The degree of this adjustment is output as the FRdiv value to the coefficient generation unit 30 provided at the subsequent stage.

As shown in FIG. 7, when the surround sound source after upmixing is compatible with 3D audio, the interlayer balance adjustment unit 25 adjusts the balance between the direct sound and indirect sound output from the middle layer channel and the direct sound and indirect sound output from the upper and lower layer channels. That is, the interlayer balance adjustment unit 25 has, for example, one operator, and rotating this operator to the left emphasizes the direct sound and indirect sound output from the middle layer channel, and rotating it to the right emphasizes the direct sound and indirect sound output from the upper and lower layer channels. By rotating this operator left and right, the mixing engineer adjusts the balance between the direct sound and indirect sound output from the middle layer channel and the direct sound and indirect sound output from the upper and lower layer channels. The degree of this adjustment is output as an ELdiv value to the coefficient generation unit 30 provided at the subsequent stage.

Returning to FIG. 2, the coefficient generation unit 30 generates coefficients A, B, C, and D by arbitrarily combining the four parameters Fdiv, Rdiv, FRdiv, and ELdiv generated by the setting unit 20 and performing arithmetic operations. Furthermore, these combinations and arithmetic operations differ depending on each channel in the surround sound. In other words, 24 sets of coefficients A1 to D1, ..., A24 to D24 are generated by combining the values of Fdiv, Rdiv, FRdiv, and ELdiv for each of the 22.2 channels.

The generation of each coefficient An to Dn will be explained in more detail. Fdiv is made up of AnFdiv, BnFdiv, CnFdiv, and DnFdiv. Similarly, Rdiv is made up of AnRdiv, BnRdiv, CnRdiv, and DnRdiv, FRdiv is made up of AnFRdiv, BnFRdiv, CnFRdiv, and DnFRdiv, and ELdiv is made up of AnELdiv, BnELdiv, CnELdiv, and DnELdiv.

For example, by rotating the control of the front balance adjustment unit 22, AnFdiv and BnFdiv are generated for each channel in the surround sound source. Similarly, by rotating the control of the rear balance adjustment unit 23, CnRdiv and DnRdiv are generated for each channel in the surround sound source. By rotating the control of the mixing amount adjustment unit 24, AnFRdiv, BnFRdiv, CnFRdiv, and DnFRdiv are generated for each channel in the surround sound source. By rotating the control of the interlayer balance adjustment unit 25, AnELdiv, BnELdiv, CnELdiv, and DnELdiv are generated for each channel in the surround sound source.

An to Dn are generated by the following equations.
An=AnFdiv×AnRdiv×AnFRdiv×AnELdiv
Bn=BnFdiv×BnRdiv×BnFRdiv×BnELdiv
Cn=CnFdiv×CnRdiv×CnFRdiv×CnELdiv
Dn=DnFdiv×DnRdiv×DnFRdiv×DnELdiv

The coefficients A1 to D1, ..., A24 to D24 generated in the above manner are output to the calculation unit 40 provided in the subsequent stage.

As shown in FIG. 8, the calculation unit 40 calculates the audio signals to be output from each channel in the surround after upmixing based on the four sound sources DL, DR, RL, and RR separated by the separation unit 10, the parameter ROOM generated by the direct sound/indirect sound balance adjustment unit 21, and the coefficients A1 to D1, ..., A24 to D24 generated by the coefficient generation unit 30. The calculation unit 40 calculates the output T from each channel using the following (Equation 1). Note that in (Equation 1), n attached to the output T and each coefficient A, B, C, and D is the channel number in the surround, and for example, T1 is the output T of channel 1. Also, DL', DR', RL', and RR' are obtained by adjusting DL, DR, RL, and RR with the ROOM value, respectively. As a result, the calculation unit 40 generates outputs T1 to T24 from channels 1 to 24, respectively, and generates the surround sound source. The upmixed surround sound source is output to the outside from an output device such as a speaker (not shown) provided for each channel.
(Equation 1)
Tn=An×DL'+Bn×DR'+Cn×RL'+Dn×RR'...(Formula 1)

[Action]
The operation of the audio signal processing device 100 in this embodiment will be described with reference to Fig. 9. First, a stereo sound source, which is an original audio signal, is input to the separation unit 10. The separation unit 10 separates the stereo sound source into four sound sources, a left direct sound DL, a right direct sound DR, a left indirect sound RL, and a right indirect sound RR (step S01). The four separated sound sources are input to the calculation unit 40.

In the setting unit 20, the direct sound/indirect sound balance adjustment unit 21 generates a ROOM value, the front balance adjustment unit 22 generates an Fdiv value, the rear balance adjustment unit 23 generates an Rdiv value, the mixing amount adjustment unit 24 generates an FRdiv value, and the interlayer balance adjustment unit 25 generates an ELdiv value, and outputs them to the coefficient generation unit 30 or the calculation unit 40 provided in the subsequent stage (step S02). More specifically, in each of these configurations, the mixing engineer rotates one or two controls to adjust the mixing amount to adjust at least one of the direct sound or the indirect sound. As a result of this adjustment, the above-mentioned parameters are generated. The ROOM value and the coefficients generated based on the four parameters Fdiv, Rdiv, FRdiv, and ELdiv are input to the calculation unit 40 and are reflected in the surround sound source after upmixing. In other words, the adjustment of the mixing amount in the setting unit 20 can also be said to adjust the surround sound source after upmixing.

The coefficient generating unit 30 generates coefficients A, B, C, and D for each channel in the surround output by arbitrarily combining the four parameters Fdiv, Rdiv, FRdiv, and ELdiv generated by the setting unit 20 and performing arithmetic operations. That is, 24 sets of coefficients A1 to D1, ..., A24 to D24 are generated by combining the values of Fdiv, Rdiv, FRdiv, and ELdiv for each of the 22.2 channels (step S03). The coefficients A1 to D1, ..., A24 to D24 are output to the calculation unit 40 provided in the subsequent stage. Note that the Fdiv value related to the mixing amount of the direct sound does not need to be used in generating the coefficients Cn and Dn of the indirect sounds RL and RR. Similarly, the Rdiv value related to the mixing amount of the indirect sound does not need to be used in generating the coefficients An and Bn of the direct sounds DL and DR. In this way, it is not necessary to use all parameters in generating each coefficient. Also, depending on the channel, it is not necessary to generate all the coefficients using arithmetic operations. For example, the coefficients for the left channel output on the front side of the middle layer can be Bn = Dn = 1.

The calculation unit 40 calculates the outputs T1 to T24 of each channel in the 22.2ch surround from the above (Equation 1) based on the four sound sources DL, DR, RL, and RR generated by the separation unit 10, the parameter ROOM generated by the direct sound/indirect sound balance adjustment unit 21, and the 24 sets of coefficients A1 to D1, ..., A24 to D24 generated by the coefficient generation unit 30 (step S04). The calculated outputs T1 to T24 are output from speakers (not shown) provided for each channel in the surround.

[effect]
(1) In the audio signal processing device 100 of the present embodiment, the separation unit 10 separates the stereo sound source and generates four sound sources, namely, left direct sound DL, right direct sound DR, left indirect sound RL, and right indirect sound RR, by adjusting the ROOM value generated by the direct sound/indirect sound balance adjustment unit 21, and then the calculation unit 40 multiplies the coefficients generated by the coefficient generation unit 30 based on the four parameters Fdiv, Rdiv, FRdiv, and ELdiv generated by the setting unit 20, to generate a surround sound source from the stereo sound source. In this way, the stereo sound source is upmixed without performing delay processing or filter processing, so that the distortion of the sound source due to the upmix can be suppressed. Therefore, even if the upmixed surround sound source is downmixed again to the stereo sound source, the distortion generated in the stereo sound source is small.

(2) The setting unit 20 of the audio signal processing device 100 of this embodiment includes a front balance adjustment unit 22. This makes it possible to emphasize only the center sound source in the front channel output compared to other sound sources, thereby making it possible to avoid a situation in which the center sound source is buried in the other sound sources and becomes difficult to hear. In particular, when the center sound source contains important information such as a comment, it is possible to avoid a situation in which the comment cannot be heard.

(3) The setting unit 20 of the audio signal processing device 100 of this embodiment includes a rear balance adjustment unit 23. This makes it possible to adjust the balance between the center sound source and other sound sources in the rear channel output, thereby adjusting the spread of the sound output from the rear channel.

(4) The setting unit 20 of the audio signal processing device 100 of this embodiment includes a mixing amount adjustment unit 24. As a result, even if the center sound source is weaker than the other sound sources, by mixing the indirect sound with the direct sound output from the front channel, the center sound source output from the front channel can be reinforced, making it easier to hear the sound localized in the center. In the same way, the center sound source can be reinforced by mixing the direct sound with the indirect sound.

(5) The setting unit 20 of the audio signal processing device 100 of this embodiment includes an interlayer balance adjustment unit 25. This makes it possible to spread the direct and indirect sounds from the middle layer in the surround sound to the upper and lower layers.

(6) The setting unit 20 of the audio signal processing device 100 of this embodiment includes a direct sound/indirect sound balance adjustment unit 21. This makes it possible to emphasize indirect sounds in the surround sound source after upmixing.

[Other embodiments]
The present invention is not limited to the above-described embodiment, and in the implementation stage, the components can be modified and embodied without departing from the gist of the invention. In addition, various inventions can be formed by appropriate combinations of the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Specifically, the following other embodiments are also included.

(1) In the above embodiment, upmixing from stereo to 22.2 ch surround was described, but the present invention can also be applied to upmixing from stereo to 5.1 ch surround, or from stereo to 5.1.2 ch surround that supports 3D audio.

(2) In the above embodiment, the output Tn of each channel is calculated separately, but this is not limited to the above. For example, the outputs of the left and right channels on the front side and the left and right channels on the side and rear sides may be the same. This can reduce the amount of calculations performed by the coefficient generation unit 30 and the calculation unit 40.

(3) In the above embodiment, the setting unit 20 generates four parameters Fdiv, Rdiv, FRdiv, and ELdiv, but this is not limited to the above. If the setting unit 20 can generate at least one parameter, it is possible to finely adjust the output Tn of each channel n by diversifying the four arithmetic operations for generating the coefficients An to Dn. Also, as shown in FIG. 10, the coefficients An to Dn may be generated using five parameters including the Room value. In this case, the coefficients can be generated, for example, using the following formulas. However, it is assumed that AnRoom=BnRoom and CnRoom=DnRoom=1-AnRoom.
An=AnRoom×AnFdiv×AnRdiv×AnFRdiv×AnELdiv
Bn=BnRoom×BnFdiv×BnRdiv×BnFRdiv×BnELdiv
Cn=CnRoom×CnFdiv×CnRdiv×CnFRdiv×CnELdiv
Dn=DnRoom×DnFdiv×DnRdiv×DnFRdiv×DnELdiv

(4) In the setting unit 20 of the above embodiment, the mixing engineer generates parameters by operating the controls provided in each component, but the parameters may also be generated by operating a GUI provided in the audio signal processing device 100.

(5) In the above embodiment, the setting unit 20 includes a direct sound/indirect sound balance adjustment unit 21, a front balance adjustment unit 22, a rear balance adjustment unit 23, a mixing amount adjustment unit 24, and an interlayer balance adjustment unit 25. In addition to these components, an equalizer may also be included. In this case, the equalizer is used to the extent that it does not distort the stereo sound source too much.

(6) In the above embodiment, the mixing amount adjustment unit 24 adjusts the amount of indirect sound to be mixed with the direct sound and the amount of direct sound to be mixed with the indirect sound, but it may adjust only the former. In other words, it is not necessary to mix the direct sound with the indirect sound.

(7) In the above embodiment, the interlayer balance adjustment unit 25 uses one operator to spread the direct and indirect sounds from the middle layer of the surround sound source to the upper and lower layers. However, by providing two operators, it is possible to adjust the direct and indirect sounds separately. The two operators may be linked, or one may be fixed and the other may rotate alone. When linked, it is preferable that one rotate in the opposite direction to the other.

(8) In the above embodiment, the hardware of the audio signal processing device 100 has been described, but the same effect can be achieved by software such as a program that causes a computer to execute the functions of each component of the audio signal processing device 100 as a procedure. For example, instead of the audio signal processing device 100 including the separation unit 10, the setting unit 20, the coefficient generation unit 30, and the calculation unit 40, the same effect can be achieved by an audio signal processing program that causes a computer to execute a separation procedure for separating a stereo sound source into direct sound and indirect sound, a setting procedure for generating parameters for adjusting at least one of the direct sound or the indirect sound, a coefficient generation procedure for generating coefficients for multiplying the direct sound and the indirect sound for each channel of the surround sound source based on the parameters, and a calculation procedure for upmixing the stereo sound source to the surround sound source by multiplying the direct sound and the indirect sound by the coefficients. This procedure is performed in the same manner as in the description of FIG. 9, for example.

100... Audio signal processing device 10... Separation unit 20... Setting unit 21... Direct sound/indirect sound balance adjustment unit 22... Front balance adjustment unit 23... Rear balance adjustment unit 24... Mixing amount adjustment unit 25... Inter-layer balance adjustment unit 30... Coefficient generation unit 40... Calculation unit X... Main operator Y... Sub-operator DL... Left direct sound DR... Right direct sound RL... Left indirect sound RR... Right indirect sound A to D... Coefficient T... Output

Claims (2)

An audio signal processing device that upmixes a stereo sound source into a surround sound source corresponding to 3D audio ,
a separation unit that separates the stereo sound source into a direct sound and an indirect sound;
a direct sound/indirect sound balance adjustment unit that generates a ROOM value that adjusts the balance between the direct sound and the indirect sound;
a front balance adjustment unit that generates a parameter for adjusting a balance between a center sound source and a sound source other than the center sound source among the direct sounds in a front channel of the surround sound source;
a rear balance adjustment unit that generates a parameter for adjusting a balance between a center sound source and a sound source other than the center sound source among the indirect sounds in a rear channel of the surround sound source;
a mixing amount adjustment unit that generates a parameter for adjusting a mixing amount of the indirect sound with respect to the direct sound output from a front channel of the surround sound source;
an inter-layer balance adjustment unit that generates a parameter for adjusting a balance between the direct sound and the indirect sound output from a channel in a middle layer in the surround sound source and the direct sound and the indirect sound output from a channel in an upper layer and a lower layer;
a coefficient generation unit that generates a coefficient by which the direct sound and the indirect sound are multiplied for each channel in the surround sound source based on the parameters;
An audio signal processing device comprising: a calculation unit that adjusts the direct sound and the indirect sound by the ROOM value and multiplies the direct sound and the indirect sound by the coefficient, thereby upmixing the stereo sound source to the surround sound source. An audio signal processing program for causing a computer to execute a process of upmixing a stereo sound source into a surround sound source corresponding to 3D audio ,
a separation step of separating the stereo sound source into a direct sound and an indirect sound;
a direct/indirect sound balance step for generating a ROOM value for adjusting the balance between the direct sound and the indirect sound;
a front balance adjustment step of generating a parameter for adjusting a balance between a center sound source and a sound source other than the center sound source among the direct sounds in a front channel of the surround sound source;
a rear balance adjustment step of generating a parameter for adjusting a balance between a center sound source and a sound source other than the center sound source among the indirect sounds in a rear channel of the surround sound source;
a mixing amount adjustment step of generating a parameter for adjusting a mixing amount of the indirect sound with respect to the direct sound output from a front channel of the surround sound source;
an inter-layer balance adjustment procedure for generating parameters for adjusting a balance between the direct sound and the indirect sound output from a middle layer channel in the surround sound source and the direct sound and the indirect sound output from upper and lower layer channels;
a coefficient generation step of generating a coefficient by which the direct sound and the indirect sound are multiplied for each channel of the surround sound source based on the parameters;
An audio signal processing program that causes a computer to execute a calculation procedure for upmixing the stereo sound source to the surround sound source by adjusting the direct sound and the indirect sound with the ROOM value and multiplying the direct sound and the indirect sound by the coefficient.

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