JP2000278787A - Stereophonic microphone device and processor for three- channel microphone input signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent performance from being deteriorated due to increment in the number of parts and scatter in the characteristics of parts by processing outputs from an AGC circuit for supplying right and left output sound signals from an analog mixing circuit by a digital stereophonic conversion processing circuit. SOLUTION: Right and left sound signals R3, L3 from an analog mixing circuit are supplied to an analog AGC circuit and automatically controlled to a level optimum to a post circuit and the automatically controlled signals are supplied to an A/D converter, which converts these analog signals into digital right and left sound signals R5, L5. These digital right and left sound signals R5, L5 are supplied to a digital stereophonic conversion processing circuit, to which directivity control signals are supplied from a terminal t, to execute digital stereophonic operation processing. The digital right and left sound signals R6, L6 processed by digital stereophonic conversion processing are supplied to digital recording system signal processing circuit, which executes the compression processing or the like of a color video signal outputted from a video camera.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stereo microphone device and a three-channel microphone input signal processing device each having an omnidirectional left, right, and center microphone, and a three-channel microphone input signal processing circuit.

[0002]

2. Description of the Related Art For example, a video camera-integrated magnetic recording / reproducing apparatus (VTR) is usually equipped with a plurality of microphones for collecting stereo sound. In some cases, left and right microphones each having unidirectionality (forward direction) are used, and these left and right microphones are attached to a video camera-integrated magnetic recording / reproducing apparatus at a predetermined angle. In this case, since the left and right microphones can collect the stereo sound, a complicated stereo processing circuit as described later is not required. But,
Since a certain space is required for the microphone due to the characteristics of a unidirectional (forward-directed) microphone, the left and right microphones should be mounted, for example, in a bar shape on the top of a video camera-integrated magnetic recording / reproducing apparatus. become. Further, since the angles formed by the left and right microphones are usually fixed mechanically, the directional angles of the left and right microphones are fixed. Therefore,
In this case, since the left and right microphones cannot be built in the video camera-integrated magnetic recording / reproducing apparatus, it is not suitable for downsizing the video camera-integrated magnetic recording / reproducing apparatus.

When omnidirectional left and right microphones are used, they are resistant to wind and wind noise outside and the space for the microphones does not need to be very large. The size of the video camera-integrated magnetic recording / reproducing apparatus can be reduced. Also, since the left and right microphones are used, the microphone input signal processing circuit only has to process the microphone input signal of two channels, and the configuration of the stereo conversion processing circuit becomes simple and compact. The circuit can be digitized. However, when omni-directional microphones are used as the left and right microphones, there is a disadvantage that the directivity angle cannot be changed because forward directional characteristics cannot be obtained.

When the omnidirectional left, right, and center microphones are used, the microphones are resistant to wind blown noise outdoors, and can obtain forward directivity by operation of a microphone input signal processing circuit. Since it can be built in the recording / reproducing device, the size of the magnetic recording / reproducing device integrated with the video camera can be reduced. However, three-channel microphone input signals from the left, right, and center microphones are subjected to analog signal processing for stereo processing and microphone directivity control, or digital signal processing for stereo processing. Since the AGC circuit and the A / D converter are required for three channels each, the configuration of the microphone signal processing circuit becomes complicated, which leads to an increase in the price of the stereo microphone device and the magnetic recording / reproducing device integrated with the video camera. .

[0005] By using four or more unidirectional or omnidirectional microphones in combination and processing the microphone input signals of the four or more channels, a stereo microphone device having various features can be realized. However, if the stereo processing circuit is realized by an analog circuit, the circuit configuration becomes complicated, and if it is realized by a digital circuit, the number of AGC circuits and A / D converters is required according to the number of microphones. As a result, the price increases, the microphone signal processing circuit becomes complicated, and the price of the stereo microphone device and the magnetic recording / reproducing device integrated with the video camera increases.

The stereo microphone devices of the above-mentioned methods (1) to (4) have advantages and disadvantages, but the video camera-integrated magnetic recording / reproducing device often employs the microphone devices of the methods (1) and (2).

Therefore, referring to FIG. 5, the left, right, and center microphones incorporated in a digital magnetic recording / reproducing apparatus (digital VTR) integrated with a video camera employing the stereo microphone device of the above-described method, and its three microphones. A configuration of a conventional example of a channel microphone input signal processing device (circuit) will be described.
ML, MR and MC are omnidirectional left, right and center microphones, respectively, which are facing forward, while the left and right microphones ML and MR are center microphones MC.
With respect to the rear.

[0008] Left, right and center microphone input signals (audio signals) L1, R from these microphones ML, MR and MC.
1 and C1 are respectively supplied to the preamplifiers AL, AR and AC and amplified, and then the amplified audio signal L
2, R2 and C2 are analog stereophonic arithmetic processing circuits A
The signal is supplied to the SO and converted into left and right two-channel audio signals L3, R3. The circuit configuration of this analog stereo conversion arithmetic processing circuit ASO will be described later with reference to FIG. 6, but the circuit ASO is supplied with a directional angle control signal CS for changing the directional angle of the microphone from an input terminal t. Is done.

The left and right audio signals L3 and R3 from the analog stereophonic arithmetic processing circuit ASO are supplied to an analog AGC circuit (automatic gain control circuit) (comprising a two-channel AGC circuit) AAG, and are supplied to a subsequent circuit. After automatic gain control is performed to an optimum level for the processing of the above, the signals are supplied to A / D converters LAD and RAD, respectively, and are converted into digital left and right audio signals L5 and R5.

These digital left and right audio signals L5, R
5 is supplied to a digital recording system signal processing circuit DRSP to compress color video signals from a video camera (not shown), to shuffle digital left and right audio signals L5 and R5, and to perform color video signals and digital After performing framing processing and the like for recording the left and right audio signals L5 and R5 on the magnetic tape, the obtained digital video / audio recording signal DS is supplied to the digital magnetic recording / reproducing device RPS and converted into a high-frequency signal. Recording is performed on a magnetic tape by a rotating magnetic head provided on the rotating drum of a tape guiding drum device including a fixed drum and a rotating drum.

Next, with reference to FIG. 6, a specific circuit configuration of the analog stereo conversion processing circuit ASO in the three-channel microphone input signal processing device (circuit) of FIG. 5 will be described. Left, right, and center microphone audio signals L2, R2, and C2 from the preamplifiers AL, AR, and AC are supplied to input terminals TL1, TR1, and TC1, respectively. The left and right audio signals L2, R2 are respectively added to an adder (subtractor) ADL1,
ADR1 and a delay unit DLL,
DLR. The delayed left and right audio signals L2, R2 from the delay units DLL, DLR are output from the attenuator ATL,
After being supplied to the ATR and attenuated, the signals are supplied to adders ADR1 and ADL1 on the opposite sides, respectively, and are subtracted from the right and left audio signals R2 and L2, respectively. Adder ADL
1, the subtraction outputs of ADR1 are equalizers EQL, EQL, respectively.
After being supplied to the QR and equalized, the respective adders ADL
2, supplied to ADR2.

On the other hand, the left and right audio signals L2 and R2 from the input terminals TL1 and TR1 are supplied to an adder ADLR and added, and the converted output is supplied to a delay unit DLC to be delayed. After being supplied to the ATC and attenuated, the signal is supplied to the adder (subtractor) ADC, and is supplied to the input terminal T.
It is subtracted from C1 from the central audio signal C2 supplied to the adder ADC. The subtraction output from the adder ADC is supplied to an equalizer EQC and equalized, and then supplied to a variable gain amplifier GA. The gain is controlled by a directional angle control signal CS from an input terminal t. The signal whose gain is controlled, that is, the forward directional signal is added to the adder ADL described above.
2. Equalizers EQL, E
The added output L is added to each audio signal from the QR.
3, R3, that is, the left and right audio signals L converted into stereo
2 and R2 are output to output terminals TL2 and TR2, and supplied to the analog AGC circuit AAG in FIG.

Next, referring to FIG. 7, the configuration of a conventional example of left, right, and center microphones and a three-channel microphone input signal processing device (circuit) mounted on a digital magnetic recording / reproducing apparatus integrated with a video camera will be described. explain. In FIG. 7, parts corresponding to those in FIG.
L3, R3, C3; L4, R4, C4; L
5, R5 are the audio signals L3, R3; L4, R4;
They do not always correspond to L5 and R5.

ML, MR and MC are omnidirectional left, right and center microphones, respectively. These microphones face forward, but as in FIG.
L and MR are located behind the central microphone MC.
The left, right, and center microphone input signals (audio signals) L1, R1, and C1 from the microphones ML, MR, and MC are supplied to and amplified by the preamplifiers AL, AR, and AC, respectively, and then amplified. , R2, C2 are
After being supplied to an analog AGC (automatic gain control circuit) circuit AAG and being subjected to automatic gain control, it is supplied to A / D converters LAD, RAD, and CAD, respectively, and digitized to produce digital left, right and center audio signals. L4, R4, C4
Is obtained.

These digital left, right and center audio signals L
4, R4 and C4 are digital stereophonic operation processing circuits D
The signal is supplied to the SO and is converted into digital audio signals L5 and R5 of two channels, left and right. This digital stereo conversion arithmetic processing circuit DSO may use a circuit obtained by digitizing the analog stereo conversion arithmetic processing circuit of FIG. This circuit DSO is supplied with a directional angle control signal (digital directional angle control signal) CS from an input terminal t.

These digital left and right audio signals L5, R
5 is supplied to a digital recording system signal processing circuit DRSP to compress color video signals from a video camera (not shown), to shuffle digital left and right audio signals L5 and R5, and to perform color video signals and digital After performing framing processing and the like for recording the left and right audio signals L5 and R5 on the magnetic tape, the obtained digital video / audio recording signal DS is supplied to the digital magnetic recording / reproducing device RPS and converted into a high-frequency signal. Recording is performed on a magnetic tape by a rotating magnetic head provided on the rotating drum of a tape guiding drum device including a fixed drum and a rotating drum.

[0017]

As described above, a stereo microphone device using omnidirectional left, right, and center microphones is resistant to wind blown noise outdoors and is operated by a microphone input signal processing circuit as described above. In addition, since it is possible to realize the forward directional characteristics and to incorporate the stereo microphone device into a device provided with the stereo microphone device, there is an advantage that the device can be downsized. Good, and furthermore, since a good stereo sound field can be realized so as to adopt a super forward directivity such as a zoom microphone device, a device provided with the stereo microphone device, for example, a video video camera It is very suitable to be mounted on an integrated magnetic recording and reproducing apparatus (VTR) for use.

In a video camera-integrated magnetic recording / reproducing apparatus (VTR), two-channel stereo sound signals are usually recorded on a magnetic tape. Therefore, in a stereo microphone apparatus, a center microphone is provided in addition to a left and right microphone. Is added, it is necessary to convert a three-channel microphone input signal into a two-channel audio signal using a stereophonic arithmetic processing circuit as described in the conventional example of FIGS.

In the case of the conventional example shown in FIG. 5, three-channel microphone input signals from omnidirectional left, right, and center microphones ML, MR, and MC are supplied to an analog stereo conversion processing circuit ASO. After converting to the audio signal of the channel, the audio signal of the two channels is converted to an analog AGC signal.
Circuit (consisting of a two-channel AGC circuit) AAG for automatic level adjustment and then A / D converter LAD,
The signal is supplied to the RAD, converted into a digital signal, and the digital audio signal is supplied to the digital recording system signal processing circuit DRSP.

In the case of the conventional example shown in FIG. 7, three omnidirectional left, right and center microphones ML, MR and MC are used.
The channel microphone input signal is supplied to an analog AGC circuit (consisting of a three-channel AGC circuit) AAG for automatic level adjustment, and then each of the A / D converters LA
D, RAD CAD to convert to digital signal,
The three channels of digital audio signals are supplied to a digital stereo processing circuit DSO, converted into two channels of digital audio signals, and then supplied to a digital recording system signal processing circuit DRSP.

In the case of the conventional example shown in FIG. 7, the analog AGC circuit AAG is constituted by a three-channel AGC circuit for automatically controlling the level of the microphone input signal for three channels. Since the configuration becomes complicated, a stereo microphone device and a device provided with the stereo microphone device, such as a video camera-integrated magnetic recording / reproducing device, cause an increase in price, an increase in power consumption, and an increase in the number of components. There is a tendency for the conventional three-channel microphone input signal processing circuit shown in FIG. 5 to be adopted, which requires only two channels for the AGC circuit.

However, if the stereo processing circuit is formed by an analog circuit as in the conventional example shown in FIG. 5, the circuit scale is not so large for realizing a large-scale integrated circuit.
There is no other choice but to use discrete elements such as general-purpose operational amplifiers (operational amplifiers), resistors and capacitors.
This increases the number of components, which makes it impossible to reduce the size of the printed circuit board, resulting in performance degradation due to variations in the characteristics of components (elements), limitations on functional improvement, S / N degradation of audio signals, and the like.

In view of the foregoing, the present invention provides a stereo system having omnidirectional left, right, and center microphones, and a three-channel microphone input signal processing circuit for processing microphone input signals from the left, right, and center microphones. In the microphone device, the AGC circuit requires only two channels,
Increasing the number of components by constructing the stereo processing circuit with discrete elements, performance degradation due to variations in component characteristics, limitations on function improvement, S / S of audio signals
An object of the present invention is to propose a device that does not cause N degradation or the like.

In view of the above, the present invention provides a three-channel microphone input signal processing apparatus for processing microphone input signals from omnidirectional left, right, and center microphones, respectively. Proposes a device that does not cause an increase in the number of components due to the configuration of the stereo conversion processing circuit using discrete elements, performance degradation due to variations in component characteristics, limitations on function improvement, S / N degradation of audio signals, etc. What you want to do.

[0025]

A stereo microphone device according to a first aspect of the present invention includes omnidirectional left, right, and center microphones, respectively, and the center microphone is located a predetermined distance behind the left and right microphones. The left, right and center microphone input signals L, R, and C are supplied from the left, right, and center microphones respectively, and the delay coefficient corresponding to a predetermined distance is α. L-αC, R-α
C, an AGC circuit to which left and right output audio signals L-αC, R-αC from the analog mix circuit are supplied, and left and right output audio signals L-αC, R from the AGC circuit A first adder for adding digital left and right output audio signals L-αC and R-αC obtained by digitizing αC, a first subtractor for subtraction, and an addition output M from the first adder, And a second adder for adding the subtraction output S from the first subtractor, and a digital-stereo operation circuit including a second subtractor for subtraction, respectively. The digital left and right audio output signals are obtained.

According to the first aspect of the present invention, the left, right, and center microphone input signals L, R, and C from the left, right, and center microphones, respectively, are supplied to the analog mix circuit, and the rear signals to the left and right microphones are supplied. When the delay coefficient corresponding to the predetermined distance of the central microphone located at α is set to α, the left and right output audio signals L-αC and R-αC are obtained, and the left and right output audio signals L-αC from the analog mix circuit are obtained. R-αC to AG
The digital left and right output audio signals L-αC and R-αC obtained by digitizing the left and right output audio signals L-αC and R-αC from the AGC circuit are supplied to the C circuit. The signals are supplied to a processing circuit, added by a first adder, and subtracted by a first subtractor to obtain an addition output M and a subtraction output S. The signals are supplied to an adder and a second subtractor, and are added and subtracted, respectively, to obtain digital left and right audio output signals from the digital stereo processing circuit.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first aspect of the present invention comprises omnidirectional left, right and center microphones, respectively. When the left, right, and center microphone input signals L, R, and C are supplied from the right and center microphones, respectively, and a delay coefficient corresponding to a predetermined distance is α, the left and right output audio signals L-αC, R− an analog mix circuit for obtaining αC, and left and right output audio signals L from the analog mix circuit
AGC circuit to which -αC and R-αC are supplied, and its AG
Left and right output audio signals L-αC and R-αC from the C circuit
Left and right output audio signals L obtained by digitizing
A first adder for adding -αC and R-αC, a first subtractor for subtraction, and an addition output M from the first adder and a subtraction output S from the first subtractor, respectively. And a digital stereo processing circuit including a second adder and a second subtracter for subtraction, and a digital microphone output processing circuit for obtaining digital left and right audio output signals from the digital stereo processing circuit. is there.

According to a second aspect of the present invention, there is provided the stereo microphone device of the first aspect of the invention, further comprising variable adjusting means for variably adjusting the level of the added output from the first adder. Level-adjusted addition output M
Is supplied to a second adder and a second subtractor.

According to a third aspect of the present invention, there is provided the stereo microphone device according to the first aspect of the present invention, further comprising variable adjusting means for variably adjusting the level of the subtraction output from the first subtractor. Subtraction output S with variable level adjustment
Is supplied to a second adder and a second subtractor.

According to a fourth aspect of the present invention, the left, right, and center microphone input signals are respectively omnidirectional, and the left, right, and center microphones are located a predetermined distance behind the left and right microphones. When L, R, and C are supplied and a delay coefficient corresponding to a predetermined distance is set to α, an analog mix circuit that obtains left and right output audio signals L-αC and R-αC, and a left and right output from the analog mix circuit. An AGC circuit to which the right output audio signals L-αC and R-αC are supplied;
Left and right output audio signals L-αC, R-α from the GC circuit
A first adder for adding digital left and right output audio signals L-αC and R-αC obtained by digitizing C, a first subtractor for subtraction, and an addition output M from the first adder; A digital stereo processing circuit including a second adder for adding the subtraction output S from the first subtractor and a second subtractor for subtracting, respectively, from the digital stereo processing circuit; This is a three-channel microphone input signal processing device for obtaining left and right audio output signals.

According to a fifth aspect of the present invention, in the three-channel microphone input signal processing device of the fourth aspect of the present invention, variable adjustment means for variably adjusting the level of the addition output from the first adder is provided. This is a three-channel microphone input signal processing device in which an addition output M whose level has been variably adjusted by an adjustment means is supplied to a second adder and a second subtractor.

According to a sixth aspect of the present invention, in the three-channel microphone input signal processing apparatus according to the fourth aspect of the present invention, variable adjustment means for variably adjusting the level of the subtraction output from the first subtractor is provided. This is a three-channel microphone input signal processing device configured to supply a subtraction output S whose level has been variably adjusted by an adjustment means to a second adder and a second subtractor.

[Specific Example of Embodiment of the Invention] A stereo microphone device and a three-channel microphone input signal processing device (circuit) according to a specific example of the embodiment of the present invention will be described below in detail with reference to FIG. explain. Note that, in FIG. 1, portions corresponding to FIG. 5 and FIG. Further, L3 and R which are the codes of the audio signal in FIG.
L4, R5; L6, R6 do not necessarily correspond to L3, R3; L4, R4; L5, R5 in FIGS. 5 and 6 and L3, R3; L4, R4; L5, R5 in FIG.

ML, MR and MC indicate omnidirectional left, right and center microphones, respectively, and these microphones face forward, but in FIG. 1, unlike FIG. 5 and FIG. MC is located behind the left and right microphones ML and MR. Left, right and center microphone input signals (audio signals) from these microphones ML, MR and MC
L1, R1, and C1 are preamplifiers AL, AR,
After being supplied to the AC and amplified, the amplified audio signals L2, R2, and C2 are converted into analog mix circuits AMX.
And the left and right two-channel audio signal L
3. Converted to R3. The specific configuration of the analog mix circuit AMX will be described later with reference to FIG.

The left and right audio signals L3 and R3 from the analog mix circuit AMX are supplied to an analog AGC circuit (automatic gain control circuit) (comprising a two-channel analog AGC circuit) AAG, and are supplied to a subsequent circuit. After being automatically controlled to the optimum level, the A / D converter L
AD and RAD, and converted into digital left and right audio signals L5 and R5, respectively.

These digital left and right audio signals L5, R
5 is supplied to the digital stereo conversion operation processing circuit DSO to which the respective control signals are supplied from the input terminal t, and is subjected to digital stereo conversion operation processing. The details of the digital stereo conversion operation processing circuit DSO will be described later with reference to FIG. The digital left and right audio signals L6 and R6, which have been subjected to digital stereo processing from the circuit DSO, are supplied to a digital recording system signal processing circuit DRSP to compress color video signals from a video camera (not shown). Shuffling processing of digital left and right audio signals L5 and R5, color video signals and digital left and right audio signals L5,
By performing a framing process or the like for recording on the magnetic tape of R5, a digital video / audio recording signal DS is obtained. The digital video / audio recording signal DS is supplied to a digital recording / reproducing device (digital VTR) RPS, and is converted into a high frequency signal. Recorded on a magnetic tape by the rotating magnetic head.

Next, a specific configuration of the analog mix circuit AMX in FIG. 1 will be described with reference to FIG. Left, center, and right audio signals L2, C2, and R2 from the pudding amplifiers AL, AC, and AR of FIG.
It is supplied to TC3 and TR3. In this analog mix circuit, the left, center and right audio signals L2, C2, R2 are
The left and center and right audio signals L, C, and R will be read as the respective components and the configuration and operation will be described.

The left, center, and right audio signals L, C, and R are supplied to an adder (subtractor) ADL3, a delay unit DLCC having a delay coefficient α, and an adder (subtractor) ADR3, respectively. In the adders ADL3 and ADR3, the delayed output αC of the central audio signal from the delay unit DLCC is subtracted from the left and right audio signals L and R, respectively, and the audio signals L-αC and R-αC, that is, The signals are output to the output terminals TL4 and TR4 as right audio signals L3 and R3, and supplied to the analog AGC circuit AAG in FIG.

In the analog mix circuit shown in FIG. 2, since the left and right output audio signals L-αC and R-αC obtained therefrom are symmetrical signals, the variation in the circuits is small and the level balance is good. Analog AGC circuit AAG
Design becomes easy. Also, this analog mix circuit is composed of two adders and one delay unit. Moreover, the adder can be composed of an operational amplifier IC, and the delay unit can be composed of a resistor and a capacitor. Becomes easier.

Next, a specific configuration of the digital stereo conversion operation processing circuit (digital mid-side stereo conversion processing circuit) DSO of FIG. 1 will be described with reference to FIG. Digital left and right audio signals L5 and R5 from the A / D converters LAD and RAD in FIG.
5 is supplied. In this digital stereo processing circuit, the digital left and right audio signals L5 and R5 are converted into digital left and right audio signals (L-αC), (R-α
The description is replaced with C). The digital left and right audio signals (L-αC) and (R-αC) are analog output signals L3 (= L-αC) and R3 (=) from the output terminals TL4 and TR4 of the analog mix circuit in FIG. R-
αC), which corresponds to a digitized signal that has been subjected to automatic gain control.

In the adder ADL4, the digital left audio signal (L-αC) and the digital right audio signal (R-αC)
And the digital audio signal {(L + R) -2αC}
Get. Further, in an adder (subtractor) ADR4, the digital right audio signal (R-αC) is subtracted from the digital left audio signal (L-αC) to obtain a digital audio signal (LR).
Get.

The digital audio signal {(L + R) -2αC} from the adder ADL4 is supplied to the variable gain amplifier GAA, and the gain thereof is adjusted by the directional angle control signal CS from the input terminal t. Signal ｛(L +
R) -2αC} is multiplied by the directivity angle control coefficient G to obtain a digital audio signal G {(L + R) -2αC}, and the digital audio signal G {(L + R) -2αC} is converted into a frequency-dependent coefficient γ. Is supplied to the equalizer EQLL and equalized to obtain a digital audio signal (digital mid audio signal) M [= Gγ
{(L + R) -2αC}], and adders ADL5 and ADL5
Supply to DR5. The digital audio signal (LR) from the adder ADR4 is converted into an equalizer E having a frequency-dependent coefficient β.
The digital audio signal S (= β
(LR) is obtained and supplied to the adder (subtractor) ADR5.

In the adder ADR5, the digital audio signal M [= Gγ {(L + R) -2αC}] and the digital audio signal (digital side audio signal) S (= β (L−
R)｝ to obtain a digital audio signal (M + S) at the output terminal TL6.
Is read as the digital left audio signal L6 and supplied to the digital recording system signal processing circuit DRSP of FIG. Note that the digital audio signal (M + S) is M + S = Gγ ｛(L + R)
−2αC {+ β (LR)}.

In the adder (subtractor) ADR5, the digital audio signal M [= Gγ ｛(L +
R) -2αC {], the digital audio signal S (= β (LR)} from the equalizer EQRR is subtracted to obtain a digital audio signal (MS).
-S) as the digital right audio signal R6,
To the digital recording system signal processing circuit DRSP.
Note that the digital audio signal (MS) is given by MS = Gγ
{(L + R) -2αC} -β (LR)}.

Digital audio signal (M + S) [= Gγ
{(L + R) -2αC} + β (LR)} and digital audio signal (MS) [Gγ {(L + R) -2αC} −
β (LR)}] are generally omnidirectional microphones ML, M
(M + S), (MS) calculated from the audio signals from R and MC according to the calculation of the mid-side stereo system.
According to the specific example of this embodiment, the arithmetic processing of the mid-side method can be performed even after the signal passes through the analog mix circuit AMX.

According to the stereo processing circuit shown in FIG.
Even after the left, right, and center microphone input signals from the left, right, and center microphones are synthesized by the analog mix circuit AMX, the digital audio signal ｛(L + R) −2, which is the center channel signal, is output by the variable gain amplifier GAA.
By varying the level of αC｝, the microphone directivity angle can be controlled.

Although the variable gain amplifier GAA is inserted in the signal path of the digital audio signal M in the circuit of FIG. 3, the signal path of the digital audio signal S, ie, the subtractor ADR
4 and the equalizer EQRR, the gain of which is changed by the directivity control signal CS from the input terminal t, and the level of the digital audio signal (LR) from the subtractor ADR4 is changed. Is also good.

FIG. 4A shows left, right and center microphones ML, M
The arrangement of R and MC is shown, and these left, right and center microphones M
L, MR and MC are facing forward, and the central microphone M
C is located behind the left and right microphones ML and MR, so that the center microphone MC is
Sound is collected with a time delay α from L and MR. Correspondingly, the analog center audio signal C from the center microphone MC has a time delay α in the analog mix circuit of FIG.
Is multiplied by the delay coefficient α.

FIG. 4B shows a digital mid-speech signal M [= Gγ in the digital stereophonic operation processing circuit of FIG.
{(L + R) -2αC}], and has a single directivity in the front principal axis direction. FIG. 4C
Indicates a directivity pattern of a sound output of the digital side audio signal S ｛= β (LR)｝ in the digital stereophonic arithmetic processing circuit of FIG. 3, and a bidirectional pattern is formed in two directions perpendicular to the front main axis direction. Show.

FIG. 4D shows a digital audio signal (M + S),
3 shows the directivity pattern of each of the voiced sounds of (MS), and shows the directivity angle control coefficient G in the digital stereo conversion arithmetic circuit of FIG.
, The angle between the M + S axis and the MS axis can be changed. The variable gain amplifier GA in the digital stereo conversion operation circuit of FIG.
When the gain G of A is increased (G> 1), the M + S axis and M−
When the angle formed by the S-axis decreases, the forward directional characteristics increase. On the contrary, when the gain G is reduced (G <1), the angles formed by the M + S axis and the MS axis increase, and the forward directional characteristics weaken. Become.

As described in the description of the modification of the circuit shown in FIG. 3, the variable gain amplifier GAA outputs the digital audio signal S (=
LR), the gain G of the variable gain amplifier GAA is increased (G> 1), contrary to the above.
And the angle between the M + S axis and the MS axis becomes larger,
The forward directivity becomes weak, and conversely, the gain G is reduced (G <
1), the angles formed by the M + S axis and the MS axis become smaller, and the forward directional characteristics become stronger.

[0052]

According to the first aspect of the present invention, there are provided omnidirectional left, right and center microphones, respectively. When the left, right, and center microphone input signals L, R, and C are supplied from the right and center microphones, respectively, and a delay coefficient corresponding to a predetermined distance is α, the left and right output audio signals L-αC, R− an analog mix circuit for obtaining αC, and left and right output audio signals L from the analog mix circuit
AGC circuit to which -αC and R-αC are supplied, and its AG
Left and right output audio signals L-αC and R-αC from the C circuit
Left and right output audio signals L obtained by digitizing
A first adder for adding -αC and R-αC, a first subtractor for subtraction, and an addition output M from the first adder and a subtraction output S from the first subtractor, respectively. And a digital left / right audio output signal is obtained from the digital / stereo conversion processing circuit. The digital left and right audio output signals are obtained from the digital / stereo conversion processing circuit. Directivity left,
A stereo microphone device having a right and center microphone and a three-channel microphone input signal processing circuit for processing microphone input signals from the left, right, and center microphones,
The AGC circuit requires only two channels, and the number of components increases due to the configuration of the discrete arithmetic processing circuit by discrete elements, performance degradation due to variations in component characteristics, limit of function improvement, S / N degradation of audio signal, etc. And a small and inexpensive device that does not cause the above problem can be obtained. The analog mix circuit has a simple structure, and the left and right output audio signals L-αC and R-α obtained therefrom are obtained.
Since C is a symmetric signal, there is little variation in the circuit,
Since the level balance is good, the design of the analog AGC circuit at the subsequent stage becomes easy.

According to the second aspect of the present invention, in the stereo microphone device of the first aspect of the present invention, the stereo microphone device is provided with variable adjustment means for variably adjusting the level of the addition output from the first adder.
Since the addition output M whose level is variably adjusted by the variable adjustment means is supplied to the second adder and the second subtractor, the omnidirectional left, right, and center microphones and the left and right microphones are respectively provided. In a stereo microphone device having a three-channel microphone input signal processing circuit for processing microphone input signals from the right and center microphones, the AGC circuit is sufficient for two channels, and the stereo conversion processing circuit is constituted by discrete elements. , There is no risk of causing performance degradation due to variations in component characteristics, limitations on function improvement, S / N degradation of the audio signal, etc., and the emission of the audio signals (M + S) and (MS). Obtaining a compact and inexpensive device capable of controlling the microphone pointing angle by variably adjusting the angle between the (M + S) and (MS) axes of the directional pattern of sound and voice. It is possible. The analog mix circuit has a simple structure, and the left and right output audio signals L-αC and R-αC obtained therefrom are symmetrical signals.
Because there is little circuit variation and good level balance,
The design of the subsequent analog AGC circuit is facilitated.

According to the third invention, in the stereo microphone device of the first invention, variable adjusting means for variably adjusting the level of the subtraction output from the first subtractor is provided.
The subtraction output S whose level has been variably adjusted by the variable adjusting means is supplied to the second adder and the second subtractor. Therefore, the omnidirectional left, right and center microphones and the left and right microphones are respectively provided. In a stereo microphone device having a three-channel microphone input signal processing circuit for processing microphone input signals from the right and center microphones, the AGC circuit is sufficient for two channels, and the stereo conversion processing circuit is constituted by discrete elements. , There is no risk of causing performance degradation due to variations in component characteristics, limitations on function improvement, S / N degradation of the audio signal, etc., and the emission of the audio signals (M + S) and (MS). Obtaining a compact and inexpensive device capable of controlling the microphone pointing angle by variably adjusting the angle between the (M + S) and (MS) axes of the directional pattern of sound and voice. It is possible. The analog mix circuit has a simple structure, and the left and right output audio signals L-αC and R-αC obtained therefrom are symmetrical signals.
Because there is little circuit variation and good level balance,
The design of the subsequent analog AGC circuit is facilitated.

According to the fourth aspect of the present invention, the left, right, and center microphones are respectively omnidirectional, and the left, right, and center microphones are located a predetermined distance behind the left and right microphones. Supply the input signals L, R, C,
When a delay coefficient corresponding to a predetermined distance is α, an analog mix circuit for obtaining left and right output audio signals L-αC and R-αC, and left and right output audio signals L-αC and R from the analog mix circuit. AGC circuit to which -αC is supplied, and left and right output audio signals L-α from the AGC circuit.
A first method of adding digital left and right output audio signals L-αC and R-αC obtained by digitizing C and R-αC, respectively.
, A first subtractor for subtraction, a second adder for adding an addition output M from the first adder and a subtraction output S from the first subtractor, and a second subtractor for subtraction, respectively. And a digital stereo processing circuit comprising:
Since the digital left and right audio output signals are obtained from the digital stereo processing circuit, a three-channel microphone input signal processing device for processing the microphone input signals from the omnidirectional left, right and center microphones respectively. In this case, the AGC circuit requires only two channels, the number of components increases due to the configuration of the stereo conversion processing circuit by discrete elements, the performance deteriorates due to the variation in the characteristics of the components, the limit of the function improvement, the S / N of the audio signal. It is possible to obtain a small and inexpensive device that does not cause deterioration or the like. Further, the analog mix circuit has a simple configuration, and the left and right output audio signals L-αC,
Since R-αC is a symmetric signal, there is little variation in the circuit and good level balance.
The design of the C circuit becomes easy.

According to the fifth aspect of the present invention, the third aspect of the fourth aspect of the present invention is provided.
In the channel microphone input signal processing device, variable adjusting means for variably adjusting the level of the added output from the first adder is provided, and the level of the added output M variably adjusted by the variable adjusting means is converted to the second output. Are supplied to the adder and the second subtractor, so that the omnidirectional left and
In a three-channel microphone input signal processing apparatus for processing microphone input signals from right and center microphones, an AGC
The circuit requires only two channels, and the number of components increases due to the configuration of the discrete operation processing circuit by discrete elements, performance degradation due to variation in component characteristics, limit of function improvement, S / N degradation of audio signal, etc. There is no fear of inviting, and audio signals (M + S), (M-
(M + S) and (M−
S) It is possible to obtain a small and inexpensive device capable of variably adjusting the angle formed by the axes and controlling the directional angle of the microphone. Further, the analog mix circuit has a simple configuration, and the left and right output audio signals L-αC and R-αC obtained therefrom are symmetrical signals. The design of the analog AGC circuit is facilitated.

According to the sixth aspect of the present invention, there is provided the third aspect of the fourth aspect of the present invention.
In the channel microphone input signal processing device, variable adjusting means for variably adjusting the level of the subtraction output from the first subtractor is provided, and the subtracted output S whose level is variably adjusted by the variable adjusting means is supplied to the second output section. Are supplied to the adder and the second subtractor, so that the omnidirectional left and
In a three-channel microphone input signal processing apparatus for processing microphone input signals from right and center microphones, an AGC
The circuit requires only two channels, and the number of components increases due to the configuration of the discrete operation processing circuit by discrete elements, performance degradation due to variation in component characteristics, limit of function improvement, S / N degradation of audio signal, etc. There is no fear of inviting, and audio signals (M + S), (M-
(M + S) and (M-S)
S) It is possible to obtain a small and inexpensive device capable of variably adjusting the angle formed by the axes and controlling the directional angle of the microphone. Further, the analog mix circuit has a simple configuration, and the left and right output audio signals L-αC and R-αC obtained therefrom are symmetrical signals. The design of the analog AGC circuit is facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a stereo microphone device and a three-channel microphone input signal processing device (circuit) of a specific example of an embodiment of the present invention.

FIG. 2 is a block diagram showing a specific example of the analog mix circuit of the specific example of FIG. 1;

FIG. 3 is a block diagram showing a specific example of a digital stereophonic arithmetic processing circuit of the specific example of FIG. 1;

FIG. 4 is a layout diagram showing an arrangement of left, right, and center microphones in the specific example of FIG. 1 and a directional pattern diagram showing a directional pattern of each voiced sound;

FIG. 5 is a block diagram showing a conventional stereo microphone device and its three-channel microphone input signal processing device (circuit).

6 is a block diagram showing an example of a conventional digital stereophonic arithmetic processing circuit of FIG. 5;

FIG. 7 is a block diagram showing another conventional stereo microphone device and its three-channel microphone input signal processing device (circuit).

[Explanation of symbols]

ML left microphone, MR right microphone, MC center microphone,
AL, AR, AC purine amplifier, AMX analog mix circuit, AAG analog AGC circuit, LAD, R
AD A / D converter, DSO digital stereo conversion processing circuit, DRSP digital recording system signal processing circuit, R
PS Recording / playback device (digital VTR).

Claims (6)

[Claims] An omnidirectional left, right, and center microphone is provided, and the center microphone is located a predetermined distance behind the left and right microphones. An analog mix circuit that supplies left, right, and center microphone input signals L, R, and C and obtains left and right output audio signals L-αC and R-αC when a delay coefficient corresponding to the predetermined distance is α. And left and right output audio signals L from the analog mix circuit.
AGC circuit to which -αC and R-αC are supplied; and left and right output audio signals L-αC and R from the AGC circuit.
A first adder for adding digital left and right output audio signals L-αC and R-αC obtained by digitizing αC, a first subtractor for subtraction, and an addition output from the first adder, A digital adder for adding a subtractor M and a subtraction output S from the first subtractor, and a digital adder for subtraction, and a digital adder for subtraction. And a digital left and right audio output signal. 2. The stereo microphone device according to claim 1, further comprising: a variable adjusting unit that variably adjusts a level of an addition output from the first adder, wherein the level is variably adjusted by the variable adjusting unit. A stereo microphone device, wherein the added output M is supplied to the second adder and the second subtractor. 3. The stereo microphone device according to claim 1, further comprising: a variable adjusting unit that variably adjusts a level of a subtraction output from the first subtractor, wherein the level is variably adjusted by the variable adjusting unit. A stereo microphone device wherein the subtracted output S is supplied to the second adder and the second subtractor. 4. The left, right, and center microphone input signals L, R, and C from the left, right, and center microphones, respectively, which are omnidirectional and the center microphone is located a predetermined distance behind the left and right microphones. And the delay coefficient corresponding to the predetermined distance is α, the left and right output audio signals L-α
An analog mix circuit for obtaining C and R-αC; and left and right output audio signals L from the analog mix circuit.
AGC circuit to which -αC and R-αC are supplied; and left and right output audio signals L-αC and R from the AGC circuit.
A first adder for adding digital left and right output audio signals L-αC and R-αC obtained by digitizing αC, a first subtractor for subtraction, and an addition output from the first adder, A digital adder for adding a subtractor M and a subtraction output S from the first subtractor, and a digital adder for subtraction, and a digital adder for subtraction. A three-channel microphone input signal processing device for obtaining digital left and right audio output signals. 5. The three-channel microphone input signal processing device according to claim 4, further comprising: a variable adjusting unit that variably adjusts a level of an addition output from the first adder. A three-channel microphone input signal processing device, wherein an addition output M whose level is variably adjusted is supplied to the second adder and the second subtractor. 6. The stereo microphone device according to claim 4, further comprising: a variable adjusting unit that variably adjusts a level of a subtraction output from the first subtractor, wherein the level is variably adjusted by the variable adjusting unit. A stereo microphone device wherein the subtracted output S is supplied to the second adder and the second subtractor.