JPH06164275A - Signal processor - Google Patents

Abstract

PURPOSE:To compensate response delay for level change and to perform appropiate signal processing in a compressor with a dynamic range, etc., by performing main signal processing by using a signal obtained by delaying an input signal. CONSTITUTION:This processor is comprised of a level detection circuit 10 which detects the signal level of the input signal, a time constant control part 12 which generates a control signal to perform time constant control corresponding to a detected value, a delay circuit 14 which delays the input signal by the prescribed time (h), and a main signal processing part 16 which performs the compression processing of the dynamic range. The delay circuit 14 delays the input signal by the prescribed time (h), and gain control is performed at the main signal processing circuit 16. In other words, the main signal processing circuit 16 is comprised of a coefficient multiplier capable of varying a coefficient, and changes the level of the input signal corresponding to an inputted control signal. The response delay for the level change of a level detection signal can be compensated by performing the main signal processing by using the signal obtained by delaying the input signal in such way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device in an audio device or the like, and more particularly to a device for changing the processing according to the level of an input signal.

[0002]

2. Description of the Related Art Conventionally, in processing a voice signal,
There are various cases in which the content of processing must be changed according to the level of the input signal. For example, a dynamic range compressor in an audio amplifier outputs an input signal as it is at an input level of 0 dB, outputs an input signal up by 6 dB at an input level of -60 dB, and outputs it at 0 d.
In the range of B to -60 dB, the gain amount is continuously changed so that the output from the audio device can be easily heard.
Further, the tracking of such a change in the gain amount with respect to the input signal level is set to be fast at the time of attack and slow at the time of release.

[0003]

However, in such a conventional compressor, there is a problem that the output is not desired when the input signal level greatly changes. That is, as shown in FIG.
When the input signal level changes significantly from -60 dB to 0 dB to -60 dB (the rising point is the attack point and the falling point is the release point)
The level detection result shows that the level rises at the attack time at and the release time rt as shown in FIG.
Will gradually decrease at. By changing the time constant for level detection during attack and release, the response to the level change during attack and release is changed. Then, when a gain signal is generated using this level detection result, a result as shown in FIG. 6C is obtained. Therefore, if the compressor is operated using this gain signal, the level excessively rises near the attack point. That is, the gain determined based on the level detection result is still +6 dB at the attack point, and +6 dB is processed for a large input of 0 dB, and then the gain is gradually reduced. Therefore, as shown in FIG. 7, a signal larger than necessary for a certain period (attack period at) is output from the attack point.

Further, when a signal of 0 dB or more is output, the signal is saturating in the signal processing circuit, and as shown in FIG. 8, the end of the signal waveform is cut and the sound is generated. There was a problem of distortion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a signal processing device, such as a dynamic range compressor, which can suitably follow an input signal. With the goal.

[0006]

According to the present invention, in a signal processing device for changing signal processing for an input signal according to the level of the input signal, there are provided level detecting means for detecting the level of the input signal and the level detecting means. It is characterized in that it has a main signal processing means for processing the input signal according to the detected input signal level, and a delay means provided before the main signal processing means for delaying the signal inputted thereto.

[0007]

Since the main signal processing is performed using the signal obtained by delaying the input signal, the response delay to the level change of the level detection signal is compensated, and the suitable signal processing is performed in the main signal processing means such as the dynamic range compressor. be able to.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration, and a level detection circuit 1 for detecting the signal level of an input signal.
0, a time constant control unit 12 that generates a control signal for time constant control according to the detection value of the level detection circuit 10, a delay circuit 14 that delays an input signal by a predetermined time (h),
It is composed of a main signal processing unit 16 which performs dynamic range compression processing.

The level detection circuit 10 is composed of, for example, an absolute value circuit, an integration circuit, and a logarithmic conversion circuit. By integrating the absolute value of the input signal and logarithmically converting it,
A signal about the level of the signal at that time is obtained. But,
By passing through the integrating circuit, a delay as shown in FIG. 2 occurs depending on the time constant of the integrating circuit.

Next, the time constant control section 12 changes the time constant of the response to the change of the input signal at the time of attack and at the time of release. For example, at the time of attack, the output of the level detection circuit 10 is output as it is. Then, at the time of release, the signal from the level detection circuit 10 is further integrated. The time constant control unit 12 can also be configured by a first-order IIR low-pal filter.

That is, as shown in FIG. 3, the first-order IIR filter is composed of three coefficient multipliers a, b and c, two delay circuits d and e and one adder f,
The signal is input to the adder f via the coefficient multiplier a, and
It is input to the adder f via the delay circuit and the coefficient multiplier b. The output of the adder f is fed back to the adder f via the delay circuit e and the coefficient multiplier c. Then, the coefficient a to be multiplied in the coefficient multipliers a, b and c,
The time constant of the filter is set by setting b and c.

That is, the coefficients a, b, and c are set in the relationship of a = b and c = 1-2a, and 0 <a <1, and when a is close to 0, the time constant is large and close to 1. And the time constant is small. Therefore,
The time constant can be set to a desired value by changing the value of the coefficient a.

The attack and the release can be easily detected by the sign of the differential of the output from the level detection circuit 10.

When attacking, the time constant is small,
Make the time constant large at the time of release. Therefore, it is possible to obtain a signal having a different time constant between the attack time and the release time, as shown in FIG. 6B. Then, the time constant control unit 12 obtains the gain signal of FIG. 6C from the level detection signal thus obtained.

On the other hand, the delay circuit 14 delays the input signal by a predetermined time h, and as a result, FIG.
The signal shown in (a) is obtained. This delay time h is a time corresponding to the attack time at, and the attack time at
A slightly shorter time, for example, a time of about 1/2 to 3/4 is suitable. The attack time at is usually 20 ms.
It is set to about ec.

In the present invention, the main signal processing circuit 16 performs gain control.
That is, the main signal processing circuit 16 of the present embodiment is composed of coefficient variable coefficient multipliers, and changes the level of the input signal according to the input control signal. That is, FIG.
As shown in (c), the amplification gain for the input signal is changed between 0 dB and +6 dB. Therefore, as shown in FIG. 4B, the delayed input signal is sufficiently small during the period from the attack point based on the input signal to the time h of −60d.
Even though it is a B signal, the gain decreases from +6 dB, the level of the output signal becomes smaller, and then the time between the end of the attack time at of the input signal is a 0 dB signal with a large level, Some amplification from a few dB to 0 dB is performed. Also, in the release time with reference to the input signal, some amplification is initially performed for a signal with a large level, and then a small level of -60 dB.
The gain for the signal gradually increases, and the gain is +6 dB.
Leading to.

As described above, in this embodiment, during the period from the attack point based on the input signal to the time h, the gain is reduced from +6 dB to the output even though the delayed input signal is a sufficiently small −60 dB signal. The signal level decreases. However, even if the gain for a signal with a small level is reduced, it does not affect the audibility so much and the sound quality hardly occurs. In addition, in the time between the end of the attack time at of the input signal, a little amplification of several dB to 0 dB is performed and saturation occurs even though the level is 0 dB. However, this amount is very small, and the resulting distortion of the sound can be suppressed to be very small. Further, at the release time with reference to the input signal, some amplification is performed for a signal having a large initial level, but in this case as well, the amount is small and the distortion of the sound is not a problem.

FIG. 5 is an explanatory diagram of the waveform distortion in this embodiment. As described above, a slight distortion occurs immediately after the attack point and immediately before the release point in the delayed input signal, but this is much smaller than in the conventional case, and the present embodiment can perform suitable dynamic range compression processing. It is understood that

The processing for changing the processing content according to the level of the input signal includes, for example, noise reduction processing.

[0020]

As described above, according to the signal processing apparatus of the present invention, since the main signal processing is performed using the signal obtained by delaying the input signal, the response delay to the level change is compensated, and the dynamic range is compensated. Suitable signal processing can be performed in the main signal processing device such as the compressor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment.

FIG. 2 is a waveform diagram of a level detection signal in the example.

FIG. 3 is a first-order I used in the time constant controller 12 of the embodiment.
Explanatory drawing which shows the structure of an IR filter.

FIG. 4 is a waveform diagram illustrating the operation of the embodiment.

FIG. 5 is an explanatory diagram showing a state of waveform distortion.

FIG. 6 is a waveform diagram showing a generation state of a gain signal.

FIG. 7 is a waveform diagram showing a state of a conventional output signal.

FIG. 8 is an explanatory diagram showing a conventional waveform distortion state.

[Explanation of symbols]

 10 level detection circuit 12 time constant control circuit 14 delay circuit 16 main signal processing circuit

Claims (1)

[Claims] 1. A signal processing device for changing the signal processing for an input signal according to the level of the input signal, the level detecting means detecting the level of the input signal, and the input signal level detected by the level detecting means. A signal processing device comprising: a main signal processing means for processing an input signal; and a delay means provided in a stage preceding the main signal processing means for delaying a signal input thereto.