JPH07106883A - Digital sound volume adjustment device and digital mixing device - Google Patents

Abstract

PURPOSE:To prevent invasion of noise onto an output signal of a multiplier when a multiplier changes rapidly by connecting a digital integration device to a multiplier input of the multiplier so as to smooth the multiplier. CONSTITUTION:An A/D converter 12 converts an analog audio signal Vin from an input terminal 11 into a digital signal and gives the result to a multiplier 13 as a multiplicand input. An output of a multiplier 13 is outputted to an output terminal 15 as an analog audio signal Vout via a D/A converter 14. First and second coefficient storage registers 16, 17 store sound data respectively and output coefficients A1, A2. A changeover device 18 selects either of the coefficients A1, A2 and the selected coefficient is fed to a digital integration device 19. The digital integration device 19 is provided with an exponent response type transfer function converged in, e.g. 50ms with respect to a step input and a rapid change due to the changeover of the coefficients A1, A2 is smoothed and fed to the multiplier 13 as a multiplier input.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital volume adjusting device for adjusting the volume of a voice signal and a digital mixing device for mixing a voice signal.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional digital volume adjusting device. In FIG. 6, reference numeral 1 is an audio signal input terminal, which is connected to an AD converter 2 for converting an audio signal into a digital signal. The output of the AD converter 2 is connected to one input of the multiplier 3. Multiplier 3
Output is a DA that converts a digital signal back into a voice signal
It is connected to the converter 4, and its signal is output to the output terminal 5.
Is output from.

On the other hand, 6 is a DC power source, which is connected to a variable resistor 7 for adjusting the volume. In the variable resistor 7,
A constant voltage is supplied from the DC power source 6 and a voltage Vc proportional to the set position of the variable resistor 7 is output. This voltage V
c is converted into a digital signal by the AD converter 8 and is connected to the other input of the multiplier 3.

Next, the operation of the above conventional example will be described. In FIG. 6, the voltage V output from the variable resistor 7
Since c is multiplied by the input signal V _{in in the} multiplier 3, the output voltage Vout is given by Vout = Vin × Vc. That is, the volume of the output voltage Vout can be adjusted by the value of the voltage Vc output from the variable resistor 7.

As described above, even the above-mentioned conventional digital volume adjusting device can perform volume adjustment in proportion to the setting position of the variable resistor.

[0006]

However, in the above-mentioned conventional digital volume adjusting device, when the disassembling ability of the AD converter 8 connected to the variable resistor 7 is insufficient, or when the operation of the variable resistor 7 is suddenly changed. If so, then FIG.
Although the volume can be adjusted as shown in, the control data value corresponding to Vc has a step-like shape, so that the envelope of the output signal becomes discontinuous, and as a result, noise is mixed in the output signal. was there.

The present invention solves such a conventional problem. Even if the resolution of the AD converter for adjusting the volume is insufficient or the setting of the variable resistor changes abruptly, An object of the present invention is to provide an excellent volume adjusting device in which noise is not mixed in an output signal and a digital mixing device using the same.

[0008]

In order to achieve the above object, the digital sound volume adjusting device of the present invention is such that a multiplier is smoothed by connecting a digital integrator to the multiplier input. .

Further, the digital volume adjusting device of the present invention is
The voltage proportional to the set position of the variable resistor connected to the AD converter is AD-converted, and the AD-converted digital data is connected to the digital integrator to smooth the multiplier.

Further, in the digital mixing apparatus of the present invention, the volume of the input of the second number is adjusted by the plurality of variable resistors in the digital volume adjusting apparatus and mixed.

[0011]

Therefore, according to the present invention, since the digital input is connected to the multiplier input of the multiplier to smooth the multiplier, noise does not occur in the output signal even when the multiplier changes abruptly. .

Further, according to the present invention, since the voltage proportional to the set position of the variable resistor connected to the AD converter is AD-converted and smoothed by the digital integrator, the variable resistor is rapidly changed. Even if the AD converter connected to the variable resistor has a low resolution, noise is not mixed in the output signal.

Further, according to the present invention, the DC voltage adjusted by the variable resistor is AD-converted, smoothed by the digital integrator, and then mixed with the input sound volume. Even if the above is performed, noise is not mixed in the output signal.

[0014]

(Embodiment 1) FIG. 1 shows the configuration of a first embodiment of the present invention. In FIG. 1, reference numeral 11 is an audio signal input terminal, which is connected to an AD converter 12 for converting an audio signal into a digital signal. The output of the AD converter 12 is connected to one input of the multiplier 13. The output of the multiplier 13 is connected to a DA converter 14 that converts a digital signal into an audio signal again, and the signal is output from the output terminal 15.

On the other hand, 16 and 17 are coefficient storage registers for storing volume data, respectively, and have coefficients A1 and A2. The coefficients A1 and A2 are selected by the switch 18, and the selected coefficient A1 or A2 is selected.
Is connected to the other input of the multiplier 13 through the digital integrator 19.

FIG. 2 shows the configuration of the integrator 19. In FIG. 2, 21 is an input terminal, which is input to one of the adders 22. The output of the adder 22 is the output terminal 23.
And a delayer 24 for delaying one sampling period and a multiplier 25 for multiplication with a coefficient α, which are connected to the other input of the adder.

Next, the operation of the first embodiment will be described. First, regarding the operation of FIG. 2, assuming that the output value at a certain time is Y (n), the transfer function becomes the expression (1). Y (n) = (1-α) X (n) + αY (n-1) (1)

Here, in this difference equation, between α and n for the output when a step function is input such that X (0) = 0 and X (1) = X _{0 at} n = 0. Seek a relationship. Under this condition, equation (1) can be rewritten as equation (2). Further, similarly, when n = 1, this formula becomes like the formula (3). Y (n) = (1-α) X ₀ + αY (n-1) (2)

Y (n−1) = (1−α) X ₀ + αY (n−2) (3) By taking the difference between the formula (2) and the formula (3), the formula (4) is obtained. The
In this, the difference of Y becomes a geometric series. Y (n) -Y (n-1) = α {Y (n-1) -Y (n-2)} (4)

Since the equation (5) holds for the initial value, the general equation becomes the equation (6), and the equation (7) is obtained from this. Y (1) -Y (0) = X 0 (1-α) ··· (5) Y (n) -Y (n-1) = α n-1 (1-α) X 0 ··· ( 6)

Y (n) = (1−α ⁿ ) X ₀ (7) In the formula (7), when α is 0 <α <1, the output is gradually gradually changed from 0 to X ₀ with the passage of time. It has the property of focusing on.

In the equation (7), Y (n) is X _0.
Since the condition of focusing on ± 0.1 dB of is given by the equation (8), α = 0.0114469 is obtained.

1-α ⁿ = 0.98855553 (8) When the log of both sides of this equation is taken, the equation (9) is obtained.
Equation (10) is obtained. Here, if the integration time is set to T _i and the sampling period is set to T _S , the relationship of Expression (11) is established, and thus the relationships of Expression (12) and Expression (13) are obtained. log (α ⁿ ) = log (0.0114469) (9) n = log (0.0114469) / log (α) = -1.94131191 / log (α) (10) n = T _i / T _S・ ・ ・ (11) T _i = −1.943131191 · T _S / log (α) ・ ・ ・ (12) α = 10̂ (−1.94131191 · T _S / T _i ) ・ ・ ・ (13)

For example, when the sampling period is 48 kHz and the integration time T _i = 50 ms, the integration number α becomes α = 10 ^ {-1.941311191 / 48000 / 0.05 = 0.99814, which is about 50 ms after the step input. It turns out that it is almost focused.

In such an integrator, as shown in FIG.
When the coefficient A1 is switched to A2 by the switch 18, the output coefficient Ac has a characteristic of gradually changing from the coefficient A1 to A2 and focusing. Since this coefficient is multiplied by the input signal V _{in in the} multiplier 13, the output power V in
_out is given by V _out = V _in × Ac, i.e., the value of the register value, V _out
You will be able to adjust the volume of.

As described above, according to the first embodiment,
Since the digital integration 19 is connected to the multiplication input of the multiplier 13 to smooth the multiplier, noise does not occur in the output signal even when the multiplier sharply changes.

(Embodiment 2) FIG. 3 shows the configuration of a second embodiment of the present invention. In FIG. 3, reference numeral 31 is an audio signal input terminal, which is connected to an AD converter 32 which converts the audio signal into a digital signal. The output of the AD converter 32 is connected to one input of the multiplier 33. The output of the multiplier 33 is connected to the DA converter 34 that converts the digital signal into an audio signal again, and the signal is output from the output terminal 35.

On the other hand, 36 is a DC power source, which is connected to a variable resistor 37 for adjusting the volume. Variable resistor 37
Is supplied with a constant voltage from the DC power supply 36 and outputs a voltage Vc proportional to the setting position of the variable resistor 37.
The voltage Vc is converted into a digital signal by the AD converter 38 and then input to the digital integrator 39.
The integrator 39 has a configuration as shown in FIG. 2 as in the first embodiment. The output of the integrator 39 is connected to the other input of the multiplier 33.

Next, the operation of the second embodiment will be described. The resistance value of the variable resistor 37 changes and the DC power source 3
It is assumed that the output voltage of 6 is divided by the variable resistor 37 to output a voltage as shown in FIG. Since the AD converter 38 performs discrete conversion, stepwise output data as shown in FIG. 4B is obtained. When such stepwise changed data is given to the digital integrator 39, the smoothed integrator output as shown in FIG. 4C is obtained by the smoothing effect described in the first embodiment. Is obtained and input to the multiplier 33.

As described above, according to the second embodiment,
Since the voltage proportional to the set position of the variable resistor 37 is converted into a digital signal by the AD converter 38 and the AD-converted digital data is smoothed by the digital integrator 39, the variable resistor 37 is rapidly changed. Alternatively, even if the resolution of the AD converter 38 connected to the variable resistor 37 is low, noise is not mixed in the output signal.

The variable resistor 37 of the second embodiment described above is used.
Can use a fader whose resistance value changes due to a linear operation, or a so-called rotary volume whose resistance value changes due to a rotation operation.

(Embodiment 3) FIG. 5 shows the configuration of a third embodiment of the present invention. In FIG. 5, reference numeral 51 is a digital input terminal, and a digital input interface 52
Is connected to the AES / EBU digital audio input interface circuit, whose output is input to the adder 55 via the digital equalizer 53 and the multiplier 54. The fader 56, which is a variable resistor, is the second
DC power source 57 and AD converter 5 as shown in the embodiment of FIG.
8 and a digital integrator 59 are used to provide a multiplier for the multiplier 54 via a control circuit 60.

There are a plurality of input circuits having such a configuration, each of which is input to the adder 55. Adder 55
The signal input to is output as a digital signal from the output terminal 62 via the AES / EBU digital audio output interface circuit which is the digital output interface 61 after being mixed and output.

In the control circuit 60, as in the second embodiment, the DC power source 57 proportional to the set position of the fader 56.
The digital integrator 59 smoothes the staircase noise when the constant voltage is converted into a digital signal by the AD converter 58.

In this embodiment, since the fader 56 has the independent control circuit 60, the envelope of the output signal of the multiplier 54 is already smoothed even if any of the faders 56 is operated. Therefore, even if such mixing of signals is performed in the adder 55, noise due to the stepwise envelope change does not occur in the output signal.

As described above, according to the third embodiment,
DC power supply 57 adjusted by fader 56 which is a variable resistor
Since the voltage of 1 is AD-converted by the AD converter 58, smoothed by the digital integrator 59 and then mixed with the input sound volume, noise is not mixed in the output signal even when a plurality of audio signals are mixed.

[0037]

As is apparent from the above embodiment, the present invention connects the multiplier input of the multiplier to the digital integrator to smooth the multiplier. Therefore, even when the multiplier sharply changes, This has the effect that noise does not occur in the output signal.

Further, according to the present invention, since the voltage proportional to the set position of the variable resistor is AD-converted and the AD-converted digital data is smoothed by the digital integrator, the variable resistor is steep. Even if the AD converter connected to the variable resistor has low resolution, noise is not mixed into the output signal.

Furthermore, according to the present invention, the DC voltage adjusted by the fader is AD-converted, then smoothed by the digital integrator, and then mixed with the input sound volume, so that a plurality of audio signals are mixed. Even in the case of having noise, there is an effect that noise is not mixed in the output signal.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a configuration of a digital volume adjusting device according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram showing the configuration of an integrator according to the first embodiment of the present invention.

FIG. 3 is a schematic block diagram showing the configuration of a digital volume adjusting device according to a second embodiment of the present invention.

FIG. 4 is a signal waveform diagram showing a waveform example of each part in the second embodiment of the present invention.

FIG. 5 is a schematic block diagram showing a configuration of a digital mixing device according to a third embodiment of the present invention.

FIG. 6 is a schematic block diagram showing the configuration of a conventional digital volume adjusting device.

FIG. 7 is a signal waveform diagram showing an example of conventional control data and output signal waveforms.

[Explanation of symbols]

 11 Input Terminal 12 AD Converter 13 Multiplier 14 DA Converter 15 Output Terminal 16 Coefficient Storage Register (1) 17 Coefficient Storage Register (2) 18 Switcher 19 Integrator 21 Input Terminal 22 Adder 23 Output Terminal 24 Delayer 25 Multiplier 31 Input Terminal 32 AD Converter 33 Multiplier 34 DA Converter 35 Output Terminal 36 DC Power Supply (Constant Voltage Source) 37 Variable Resistor 38 AD Converter 39 Integrator 51 Digital Input Terminal 52 Digital Input Interface 53 Digital Equalizer 54 Multiplier 55 Adder 56 Fader 57 DC Power Supply (Constant Voltage Source) 58 AD Converter 59 Integrator 60 Control Circuit 61 Digital Output Interface 62 Output Terminal

Claims (3)

[Claims] 1. An AD converter that converts an input audio signal into a digital signal, a digital integrator that is input by switching different coefficients, and a multiplication that inputs the respective outputs of the AD converter and the digital integrator. A vessel,
A digital volume adjusting device comprising: an AD converter that converts the output of the multiplier into an audio signal. 2. A first AD converter for converting an input audio signal into a digital signal, a variable resistor connected to a DC power source, and a voltage proportional to a set position of the variable resistor into a digital signal. A second AD converter that
A digital integrator to which the output of the second AD converter is input, a multiplier to which each output of the first AD converter and the digital integrator is input, and an output of the multiplier are converted into audio signals. A digital volume control device including a DA converter. 3. A plurality of digital input interface circuits, a plurality of digital equalizers connected to the respective digital input interface circuits, a plurality of DC power sources connected to a plurality of faders, and adjustment of the respective faders. A plurality of AD converters for converting the voltage of the DC power supply proportional to the amount into a digital signal, a plurality of digital integrators to which the outputs of the respective AD converters are input, and the digital equalizers and the digital integrators on the input side. A digital mixing apparatus comprising: a multiplier connected to the above; an adder to which outputs of the respective multipliers are input; and a digital output interface circuit connected to an output of the adder.