JPH04142104A - Dynamic range compression device - Google Patents

Abstract

PURPOSE:To obtain a dynamic range compression device with satisfactory S/N with simple constitution by providing a gain control means, an output selection means, a D/A conversion means, and an amplifier means, etc. CONSTITUTION:An input digital signal is converted based on prescribed input/ output characteristic by the gain control means 102, and when an output signal level shows a value less than a reference value, the output signal is outputted as it is from the output selection means 106, and also, the amplification factor of an amplifier 108 connected to the output of a D/A conversion part 107 is set at a reference amplification factor. When the output signal level of the gain control means 102 exceeds the reference value, a signal in which the signal after conversion is attenuated to 1/N is outputted from the output selection means 106, and also, the reference amplification factor of the amplifier 108 connected to the output of the D/A conversion part 107 is set at the one of N times the reference amplification factor, thereby, the sensitivity of the mean output level of a digital signal processing part 101 can be increased. In such a way, it is possible to obtain the dynamic range compression device with actual satisfactory S/N with simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dynamic range compression device applied to digital audio amplifiers and the like.

2. Description of the Related Art In recent years, with the spread of digital audio sources such as CDs and DATs, the dynamic range of audio reproduction source signals has become wider than 90 dB. On the other hand, when actually listening to music, when it is not possible to produce a high volume, or in a noisy environment such as inside a moving car, quiet sounds in the playback signal become inaudible due to the noise, so the dynamics of the playback source signal may be affected. There are cases where the wide range actually becomes a hindrance to the entire playback system. As a countermeasure to this problem, digital signal processing is used to perform a predetermined gain adjustment according to the level of the input audio signal, compressing the dynamic range of the reproduced signal, and outputting the compressed signal.

FIG. 7 is a block diagram showing an example of the configuration of a conventional dynamic range compression device.

In FIG. 7, 70 is a sound source device, for example a CD player. 71 is a digital signal processing section; 72
73 is a gain control section within the digital signal processing section 71, and 73 is a level detection section within the digital signal processing section 71. 74 is a D/A converter connected to the output of the digital signal processor 71; 75 is a power amplifier connected to the output of the D/A converter 74; and 76 is a speaker connected to the power amplifier 75.

The operation of the conventional dynamic range compression device configured as described above will be explained below.

First, the input/output static characteristics of the digital signal processing section 71 will be described and the concept will be explained. Figure 8 shows the digital signal processing section 7.
1 shows the static characteristics of the output signal 71b with respect to the input signal 7La of No. 1. As shown in FIG. 8, in the section from the maximum input (OdB) to -24 dB input of the input signal 71a, log-linear gain conversion is performed so that the output signal 71b becomes from -12 dB to -24 dB. At an input signal level of -24 dB or less, no gain conversion is performed and the output is made with a gain of 1. As a result, relative to the maximum input, for example, for an input signal of -24 dB or less, the level is raised by 12 dB, and the dynamic range of the input signal 71a is -12 dB.
dB compression.

Next, the internal operation of the digital signal processing section 71 will be explained. FIG. 9 shows a time chart of the amplitude of each part in the digital signal processing section 71. The digital reproduction signal output from the CD player 70 becomes the input signal 71a of the digital signal processing section 71, and is assumed to be a signal whose envelope amplitude changes over time as shown in FIG. 9(a), for example. Input signal 71a is input to level detection section 73 and gain control section 72. The level detector 73 detects the envelope amplitude of the input signal 71a with a time constant. FIG. 9(b) shows the output of the level detection section 73. Tr is the falling time constant.

Ta is a rise time constant, which is set to prevent an unnatural sound. The gain control section 72 obtains a gain coefficient that realizes the input/output static characteristics shown in FIG. 8 in response to the detection level from the level detection section 73, multiplies the gain coefficient by the input signal 71a, and outputs the result. FIG. 9(C) shows the output of the gain control section 72. As shown in FIG. 9(C), the output of the gain control section 72 has a falling time constant Trs.
Due to the rise time constant Ta, the amplitude changes from -36 dB to O dB with a transient amplitude change depending on the width of the amplitude change of the input signal 71a. The output of the gain control section 72 is output as the output signal 71b of the digital signal processing section 71,
The signal is output to the D/A converter 74.

The D/A converter 74 performs D/A conversion on the input digital signal and outputs it to the power amplifier 75 as an analog signal. The power amplifier 75 amplifies the power of the input signal to a desired level and drives the connected speaker 76. With the above configuration, the dynamic range of the input signal 71a is 12
dB compression and can be played back and listened to through the speaker 76.

Problems to be Solved by the Invention However, in the conventional configuration described above, the signal is attenuated in the digital signal processing section, so the output level of the digital signal processing section for a steady signal input of, for example, OdB is -12 dB. Maximum output of digital signal processing section (O
dB), the upper two bits are not regularly used effectively. This has led to the problem of a substantial decrease in S/H.

The present invention solves the above-mentioned conventional problems, and is applicable to devices such as digital audio amplifiers, and has a simple configuration and can achieve S/N.
The purpose is to provide a good dynamic range compression device.

Means for Solving the Problems In order to achieve the above objects, the dynamic range compression device of the present invention includes: (1) level detection means for detecting the level of an input digital signal; gain control processing means for gain converting an input digital signal into a predetermined output; attenuation means for attenuating a signal output from the gain control processing means by a predetermined amount; and a level of the signal output from the gain control processing means as a reference. level determining means for outputting a determination identification signal based on the determination signal, and selectively switching and outputting the signal output from the gain control processing means and the signal output from the attenuation means based on the determination identification signal. an output selection means for converting a digital signal output from the output selection means into an analog signal, and an analog signal output from the D/A conversion means based on the determination identification signal. and an amplification means for selectively switching and outputting the amplification factor of.

(2) level detection means for detecting the level of an input digital signal; attenuation means for attenuating the level of the input digital signal by a predetermined amount and outputting the level; a first gain control processing means for gain converting the output signal of the attenuation means into a predetermined output based on a detection level of the level detection means; level determination means for comparing the level of the signal output from the first gain control processing means with a reference value and outputting a determination identification signal; output selection means for selectively switching and outputting the signal and the signal output from the second gain control processing means; and a D/A for converting the digital signal output from the output selection means into an analog signal. a conversion means;
and amplification means for selectively switching and outputting the amplification factor of the analog signal output from the D/A conversion means based on the determination identification signal.

Effects With the above configuration, the present invention has the following features: (1) The gain control processing means converts the input digital signal based on predetermined input/output characteristics, and when the output signal level of the gain control processing means is below a reference value, the gain control processing is performed. The output signal of the means is outputted as it is from the output selection means, and the D/
The amplification factor of the amplifier connected to the output of the A conversion section is set to the reference amplification factor. Further, when the output signal level of the gain control processing means is higher than the reference value, a signal obtained by attenuating the converted signal to L/N is output from the output selection means, and an amplifier connected to the output of the D/A conversion section outputs a signal obtained by attenuating the converted signal to L/N. By setting the amplification factor N times the reference amplification factor, the average output level of the digital signal processing section is increased.

(2) The first gain control processing means converts the input digital signal based on predetermined input/output characteristics, and the second gain control processing means receives a signal obtained by attenuating the input digital signal to 17N and converts the input digital signal to a predetermined value. Convert based on the input/output characteristics of Second
When the output signal level of the first gain control processing means is below the reference value, the output signal of the first gain control processing means is output from the output selection means, and the amplification factor of the amplifier connected to the output of the D/A conversion section is is set as the standard amplification factor.

Further, when the output signal level of the second gain control processing means exceeds the reference value, the output signal of the second gain control processing means is outputted from the output selection means, and at the same time, the output signal level of the second gain control processing means is outputted from the output selection means. By setting the amplification factor of the amplifier to N times the reference amplification factor, the average output level of the digital signal processing section is increased.

Embodiments Hereinafter, embodiments of the dynamic range compression apparatus of the present invention will be described with reference to the drawings.

First, a dynamic and clean compressor according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing the configuration of a dynamic range compression device in a first embodiment of the present invention.

In FIG. 1, 100 is a sound source device, for example, C
It is a D player. 101 is a digital signal processing unit; 10
2 is a gain control section, and 103 is a level detection section. The input signal 101a of the digital signal processing section 1010 is input to each of the gain control section 102 and the level detection section 103, and the output of the level detection section 103 is connected to the gain control section 102. 104 is a level determination section connected to the output of the gain control section 102, and outputs a control signal 104a. 105 is an attenuation section connected to the output of the gain control section 102. Reference numeral 108 denotes an output selection section to which the output of the gain control section 102 and the output of the attenuation section 105 are input, and is connected to the control signal 104a. Note that the gain control section 102
output bit number and level determination section 104 and attenuation section 10
The number of input bits of 5 is greater than the number of input/output bits of the digital signal processing section 101 by two or more bits.

107 is a D/A converter to which the output signal 101b is input;
108 is a power amplifier connected to the D/A converter 107; 109. 110. 111 is a resistor in the power amplifier 108, and 112 is an amplification factor changeover switch provided in the power amplifier 108, which is driven by the control signal 104a. 113 is a speaker connected to the power amplifier 108.

The operation of the dynamic range compression device of this embodiment configured as described above will be described below.

First, the input/output static characteristics of the digital signal processing section 101 will be described, and the concept of dynamic range compression will be explained. FIG. 2 shows the static characteristics of the output signal 101b with respect to the input signal 101a of the digital signal processing section 101. As shown in FIG. 2, the input signal 101a is from the maximum input (OdB) to -
In the section up to 24 dB, log-linear gain conversion is performed so that the output signal 101b becomes -12 dB from O dB. Further, when the input signal 101a is at an input signal level of -24 dB or less, it always outputs a gain of +12 dB with respect to the input signal 101'a. As a result, for example, an input signal of -24 dB or less is raised in level by 12 dB, and the dynamic range of the input signal 101a is compressed by 12 dB.

Next, the internal operation of the digital signal processing section 101 will be explained. FIG. 3 shows a time chart of the amplitude of each part in the digital signal processing section 101 with respect to the input signal 101a.

The digital playback signal output from the CD player 100 becomes the input signal 101a of the digital signal processing section 101,
As an example, assume a signal whose envelope amplitude changes over time as shown in FIG. 3(a). The input signal 101a is sent to the level detection section 10
3 and is input to the gain control section 102. The operation of the level detection section 103 is the same as that described in the conventional example, and the envelope amplitude of the input signal 101a is detected with a time constant. FIG. 3(b) shows the output of the level detection section 103. Tr is a falling time constant, and is set to about 5 seconds. T
a is a rise time constant, which is set to about 10 milliseconds. The gain control section 102 obtains a gain coefficient based on the input/output static characteristics shown in FIG. 2 in response to the detection level from the level detection section 103, and uses the gain coefficient as
Multiply with and output. FIG. 3(C) shows the gain control section 102.
shows the output of As shown in FIG. 3(C), the output of the gain control unit 102 has a transient amplitude change depending on the amplitude change width of the input signal 101a due to the fall time constant Tr and rise time constant Ta described above. -24dB to +
It varies between 12dB. The output of gain control section 102 is input to level determination section 104. Note that the gain control section 10
Since the number of output bits of 2 and the number of input bits of the level judgment section 104 are two or more bits larger than the number of input/output bits of the digital signal processing section 11, the output of +12 dB is transmitted to the level judgment section 104 without being saturated. . The level determination unit 104 determines the amplitude of the input signal for each sample.
dB (reference value), and when a sample with an amplitude exceeding the reference value is input, the control signal 104a is set to H'' for a time of rising time constant Ta from the input point, regardless of the amplitude level of the input signal. Outputs.Also,
At times other than the above, that is, when samples with amplitudes below the reference value are continuously input for longer than the rise time constant Ta, "L" is output as the control signal 104a. FIG. 3(d) shows the control signal 104a. As shown in FIG. 3(d), the output of the gain control IJB 102 is transiently
"H" is output to the control signal 104a during the time of the rise time constant Ta exceeding dB and for a further time Ta after that time. The output of the gain control section 102 is output to the output selection section 10.
6 is input as one input signal 106a. Also, the output of the gain control section 102 is 12 dB at the attenuation section 105.
It is attenuated (-2 bit shifted) and inputted as the other input signal 106b of the output selection section 106. The output selection section 106 operates to output the input signal 106a as the output signal 101b when the control signal 104a is "L", and the output of the gain control section 102 is outputted as the output signal 101b at the same level. On the other hand, when the control signal 104a is "H", the output selection unit 106 outputs the input signal 106b.
is output as the output signal 101b, and the output of the gain control section 102 is attenuated by 12 dB and becomes the output signal 101b.
is output to. FIG. 3(e) shows the output signal 101b. As shown in FIG. 3(e), the control signal 104a is "H".
”, the output signal 101b is output after attenuating the signal in FIG. 3(C) by 12 dB, and since the maximum output of the output signal 101b does not exceed O dB, it is transmitted to the next stage without saturation.Output signal 101b is input to the D/A converter 107.The D/A converter 107 performs D/A conversion on the input digital signal, and converts the input digital signal to the power amplifier 10 as an analog signal.
Output to 8. The power amplifier 108 amplifies the voltage and power of the input signal, and drives the connected speaker 113.

Amplification factor changeover switch 1 provided in power amplifier 108
12 is controlled by a control signal 104a of the level determination section 104, and selectively switches the amplification factor of the power amplifier 108. When the control signal 104a is "L", the switch 112 is turned on, and the amplification factor of the power amplifier 108 is set to the reference amplification factor (R2/RI). Further, when the control signal 104a is "H", the switch 112 is turned off, and the amplification factor of the power amplifier 108 is 12d higher than the reference amplification factor.
B is set to a large value (4X R*/R+).

Therefore, the control signal 104a shown in FIG. 3(d) is "H".
In the section 11 of the output signal 101b shown in FIG. 3(e),
The 2 dB attenuated portion is D/A converted and input to the power amplifier 108, where it is amplified by 12 dB greater than the reference amplification factor and transmitted to the speaker 113. Also, Figure 3(d)
In the section where the control signal 104a shown in FIG.
) The unattenuated portion of the output signal 101b shown in ) is the D/A
The converted signal is input to the power amplifier 108, amplified by a reference amplification factor, and transmitted to the speaker 113. Speaker 1
The input signal of the speaker 113 is shown in FIG. 3(f). As shown in FIG. 3(f), the input signal of the speaker 113 is reproduced similarly to the output of the gain control unit 102 shown in FIG. 3(C). Desired dynamic characteristics can be obtained.

As described above, according to this embodiment, the dynamic range of the input signal 101a is compressed by 12 dB, and the speaker 113
You can play and listen to it via . In addition, the digital signal processing section 101 outputs an output that is attenuated by 12 dB only during the transient time when the control signal 104a becomes "H", which is equivalent to reducing the number of output bits of the digital signal processing section 101 by 2 bits during that time. Although this will result in a significant S/N deterioration,
Since the configuration is such that the entire number of output bits of the digital signal processing section 101 is effectively used to output a signal outside of that time, which occupies most of the time, no S/N deterioration occurs. In addition, since the signal level itself is large during the transient period, the amplification factor of the knocker amplifier 108 is set to 12d.
The increase in output noise due to the increase in B is audibly masked and poses no practical problem. Therefore, the problem of reduction in S/N as described in the operation of the conventional example is practically solved.

Next, a dynamic range compression device according to a second embodiment of the present invention will be described. In the dynamic range compression device in the first embodiment, it is necessary that the number of internal processing bits of the digital signal processing section is larger than the number of input/output bits in the digital signal processing section. The device is configured to achieve the same effect even when the number of internal processing bits of the digital signal processing section is the same as the number of input/output bits of the digital signal processing section. FIG. 4 is a block diagram showing the configuration of a dynamic range compression device in a second embodiment.

In FIG. 4, 400 is a sound source device, for example, C
It is a D player. 401 is a digital signal processing section, 402 is a first gain control section, 403 is a second gain control section, 404 is an attenuation section, and 405 is a level detection section. The input signal 401a of the digital signal processing section 401 is input to the first gain control section 402, the attenuation section 404, and the level detection section 405, and the output of the attenuation section 404 is input to the second gain control section 403. has been done. Further, the output of the level detection section 405 is connected to the first gain control section 402 and the second gain control section 403. 406 is a level determination unit connected to the output of the second gain control unit 403, and outputs a control signal 406a. 407 is the output of the first gain control section 402 and the second gain control section 403
This is an output selection section to which the output of the control signal 406 is input.
a is connected. Note that the digital signal processing unit 401
The number of internal processing bits is the same as the number of input/output bits of the digital signal processing section 401. 408 is output signal 4
409 is a power amplifier connected to the D/A converter 408, 410, 411 .
412 is a resistor in the power amplifier 409, and 413 is an amplification factor changeover switch provided in the power amplifier 409, which is driven by the control signal 406a. 414 is a speaker connected to the power amplifier 409.

The operation of the dynamic range compression device of this embodiment configured as described above will be described below.

The input/output static characteristics of the digital signal processing unit 1114Ql are the same as the input/output static characteristics of the digital signal processing unit 101, which is located on the second cape of the input/output static characteristics of the first processing unit 401, and is similar to that described above. The operation compresses the dynamic range of the input signal 401a by 12 dB.

Next, the internal operation of the digital signal processing section 401 will be explained. FIG. 6 shows a time chart of the amplitude of each part in the digital signal processing section 401 with respect to the input signal 401a.

The digital playback signal output from the CD player 400 becomes the input signal 401a of the digital signal processing section 401,
As an example, assume a signal whose envelope amplitude changes over time as shown in FIG. 6(a). The input signal 401a is sent to the level detection section 40
5 and the first gain control section 402 . The operations of the level detection section 405 and the first gain control section 402 are exactly the same as the operations of the level detection section 103 and the gain control section 102 described in the first embodiment. Obtaining a gain coefficient based on the input/output characteristics shown in FIG. 5 in response to the detection level from the detection unit 405,
The input signal 401a is multiplied by the gain coefficient and output.

The output of the level detection section 405 is shown in FIG. 6(b).
C) shows the output of the first gain control section 402. Since the number of internally processed bits of the digital signal processing section 401 is the same as the maximum number of bits of the input/output signal of the digital signal processing section 401, the output of the first gain control section 402 is a saturated output during the rising time constant Ta. It is transmitted to the next stage as On the other hand, the input signal 401a is attenuated by 12 dB in the attenuation section 404 and input to the second gain control section 403. The second gain control section 403 has exactly the same configuration as the first gain control section 402, and obtains a gain coefficient based on the input/output characteristics shown in FIG. 5 in response to the detection level from the level detection section 405. The gain coefficient is multiplied by the input signal from the attenuator 404 and output. FIG. 6(d) shows the output of the second gain control section 403. As shown in FIG. 6(d), the second gain control section 4
The output of 03 is the first gain control section 4 shown in FIG. 6(C).
It is 12 dB smaller than the output of 02, and does not exceed O dB at the maximum, so it is transmitted to the next stage without saturation.

The output of the second gain control section 403 is input to the level determination section 406. The level judgment unit 40et compares the amplitude of the input signal with -12 dB (reference value) for each sample, and when a sample with an amplitude exceeding the reference value is input, it takes a time of rise time constant Ta from the input point. , the control signal 406a regardless of the amplitude level of the input signal.
outputs "H". In addition, at times other than the above, that is, when a sample with an amplitude below the reference value rises, the time constant Ta
If the input is continuous for more than the time, the control signal 40
"L" is output as 6a. FIG. 6(e) shows the control signal 406a. As shown in FIG. 6(e), the control signal 406a is at "H" during the rising time constant Ta during which the output of the first gain control section 402 is transiently saturated, and at a further time Ta after that time. is being output. The output of the first gain control section 402 is inputted as one input signal 407a of the output selection section 407. Further, the output of the second gain control section 403 is inputted as the other input signal 407b of the output selection section 407. The output selection section 407 operates to output the input signal 407a as the output signal 401b when the control signal 406a is "L", and the output of the first gain control section 402 is outputted as the output signal 101b. Further, the output selection unit 407 outputs the control signal 406a at “H”.
At this time, an operation is performed to output the input signal 407b as the output signal 401b, and the output of the second gain control section 403 is output as the output signal 401b. Output signal 4 is shown in Figure 6(f).
01b. As shown in FIG. 6(f), the output signal 4
01b is the same as the output signal 101b shown in FIG. 3(e) in the first embodiment. Output signal 401b is D/A
The data is input to the converter 408 .

The D/A converter 408 performs D/A conversion on the input digital signal and outputs it to the power amplifier 409 as an analog signal. The power amplifier 409 amplifies the voltage and power of the input signal, and drives the connected speaker 414. Amplification factor changeover switch 413 provided in power amplifier 408
is controlled by a control signal 406a of the level determination section 406, and selectively switches the amplification factor of the power amplifier 409. When the control signal 406a is "L", the switch 413 is turned on, and the amplification factor of the power amplifier 409 is set to the reference amplification factor (R1/R1). In addition, control signal 4
When 06a is "H", the switch 413 is turned off, and the amplification factor of the power amplifier 409 is set to a value (4X R2/R1) that is 12 dB larger than the reference amplification factor. Therefore,
In the section where the control signal 406a is H'', the output of the second gain control section 403 shown in FIG. 414. Furthermore, in the period in which the control signal 406a is "L", the output of the first gain control section 402 shown in FIG. It is amplified by the amplification factor and transmitted to the speaker 414.The input signal of the speaker 414 is shown in FIG. 6(g).As shown in FIG. 6(g), the input signal of the speaker 414 is the same as in the first embodiment. Figure 3 (
It becomes the same as the input signal of the speaker 113 shown in f).

As described above, according to the present embodiment, the dynamic range of the input signal 401a is compressed by 12 dB and then transmitted to the speaker 41.
4, and the same improvement effect as the S/N improvement effect described in the first embodiment is also achieved.

Effects of the Invention As described above, the present invention provides the following advantages: (1) The gain control processing means converts an input digital signal based on predetermined input/output characteristics, and when the output signal level of the gain control processing means is below a reference value, the gain control processing means converts the input digital signal based on a predetermined input/output characteristic. The output signal of the control processing means is output as it is from the output selection means, and the D/
The amplification factor of the amplifier connected to the output of the A conversion section is set to the reference amplification factor, and when the output signal level of the gain control processing means is higher than the reference value, the converted signal is set to 1/1.
By outputting a signal attenuated to N from the output selection means and setting the amplification factor of the amplifier connected to the output of the D/A converter to N times the reference amplification factor, the configuration can be effectively achieved with a simple configuration. It is possible to realize a dynamic range compression device with a good S/N ratio, and its practical value is great.

(2) A first gain control processing means and an input digital signal
A second gain control processing means is provided to input the attenuated signal to /H, and when the output signal level of the second gain control processing means is below a reference value, the output signal of the first gain control processing means is outputted. The amplification factor of the amplifier connected to the output of the D/A converter is set to the reference amplification factor as well as output from the selection means, and the output signal level of the second gain control processing means exceeds the reference value. In this case, the output signal of the second gain control processing means is outputted from the output selection means, and the amplification factor of the amplifier connected to the output of the D/A conversion section is set to N times the reference amplification factor. Even when the number of internal processing bits of the signal processing section is equal to the number of input/output bits, it is possible to realize a dynamic range compression device with substantially good S/H, and its practical value is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a dynamic range compressor according to the first embodiment of the present invention, FIG. 2 is a characteristic diagram showing the input/output static characteristics of the digital signal processing section 101 in FIG. 1, and FIG. 1 is a time chart of the output of each part in the digital signal processing unit 101, FIG. 4 is a block diagram showing the configuration of the dynamic range compression device in the second embodiment of the present invention, and FIG. Characteristic diagram showing the input/output static characteristics of the digital signal processing unit 401, No. 6
The figure is a time chart of the output of each part in the digital signal processing section 401 in FIG. 4, FIG. 7 is a block diagram showing an example of the configuration of a conventional dynamic range compression device, and FIG. 8 is the digital signal processing section in FIG. 7. FIG. 9 is a characteristic diagram showing the input/output static characteristics of the digital signal processing section 71, and FIG. 9 is a time chart of the outputs of each part in the digital signal processing section 71 in FIG. 100.400...CD player, 101,40
1... Digital signal processing section, 102... Gain control section, 103,405... Level detection section, 1
04°406...Level determination section, 105. '40
4... Attenuation section, 108,407... Output selection section, 107°408... D/A conversion section, 108
．． 409...Power amplifier, 109-111,4
10~412...Resistor, 112.413...
Amplification factor changeover switch, 113.414...Speaker,
402...first gain control section, 403...second gain control section.

Claims (2)

[Claims] (1) A dynamic range compression device that converts the level of an input digital signal based on predetermined input/output characteristics, and then converts it to an analog signal and outputs it, comprising a level detection means for detecting the level of the input digital signal. , gain control processing means for gain converting the input digital signal into a predetermined output based on the detection level of the level detection means; attenuation means for attenuating the signal output from the gain control processing means by a predetermined amount; Level determination means for comparing the level of the signal output from the control processing means with a reference value and outputting a determination identification signal; Based on the determination identification signal, the signal output from the gain control processing means and the attenuation means output selection means for selectively switching and outputting the signal output from the output selection means; D/A conversion means for converting the digital signal output from the output selection means into an analog signal; A dynamic range compression device comprising: amplification means that selectively switches and outputs the amplification factor of an analog signal output from a D/A conversion means. (2) A dynamic range compression device that converts the level of an input digital signal based on predetermined input/output characteristics, and then converts it to an analog signal and outputs it, comprising a level detection means for detecting the level of the input digital signal. , attenuating means for attenuating the level of the input digital signal by a predetermined amount and outputting it; first gain control processing means for gain converting the input digital signal into a predetermined output based on the detection level of the level detecting means; a second gain control processing means for gain converting the output signal of the attenuation means into a predetermined output based on the detection level of the level detection means; and a level of the signal output from the second gain control processing means as a reference. a level determination means for comparing a signal output from the first gain control processing means and a signal output from the second gain control processing means based on the determination identification signal; an output selection means for selectively switching and outputting a signal; a D/A conversion means for converting a digital signal outputted from the output selection means into an analog signal; and a D/A conversion means based on the determination identification signal. A dynamic range compression device comprising: amplification means that selectively switches and outputs the amplification factor of an analog signal output from the means.