JPH07154172A - Voice limiter - Google Patents

Abstract

PURPOSE:To provide the voice limiter simple in circuit configuration but difficult in causing distortion in signals. CONSTITUTION:An equalizing circuit 4, a level detection circuit 6, a polygonal line data constant table circuit 8 and a multiplier circuit 10 form one loop. The equalizing circuit 4 adjusts a level of a voice input signal 3 digitally converted by an input circuit 2, the detection circuit 3 detects a level of a voice input signal 3 after the adjustment to provide detection data 7, the polygonal line data constant table circuit 8 provides an output of a predetermined constant 9 based on the detected data 7 and the multiplier circuit 10 adjusts the level of the digital voice input signal 3 by using a constant 9 as a control signal. Thus, distortion due to a discontinuous characteristic is not caused in a level adjusted signal with a simple circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice limiter device, and more particularly to a device for controlling the level of a voice signal.

[0002]

2. Description of the Related Art Conventionally, a voice limiter device generally frequency-decomposes a modulated signal in order to increase the average degree of modulation, and performs gain adjustment on each of the decomposed frequency distributions. This relationship will be specifically described below.

FIG. 4 shows an example of the circuit configuration of a conventional voice limiter device. In this configuration example, the digital audio input signal 1
Is converted into a digital audio signal 3 separated into L and R channels by an input circuit 2, and then a low pass filter circuit 1
4. The band pass filter circuit 15 and the high pass filter circuit 16 separate the signal into a low band signal 17, a mid band signal 18 and a high band signal 19, respectively. The levels of the separated signals are controlled by the level control circuit 20 so as to enhance the average degree of modulation in terms of audibility according to the type of the input material, and the signals 21, 22, and 23 are output. Further, the limiter circuit 24 having different gain characteristics set for each band processes the low-frequency output signal 25, the mid-frequency output signal 26, and the high-frequency output signal 27. Is output.

In the above-mentioned conventional example, the digital audio signal is separated into audio signals for each band by a filter, and a limiter is directly applied to each of the separated audio signals. On the other hand, in another conventional example shown in FIG. 5, the digital audio signal 3 is distributed to each band, the level is detected by the level detection circuit 6 for each band, and these detection signals 29, 30, 3 are detected.
1 is input to the polygonal line data constant table circuit 8 to generate a constant 9 as a control signal, and the multiplier 9 converts the frequency characteristic of the audio signal by the constant 9. The converted audio signal 11 is converted into an analog signal 13 by the output circuit 12.
Is converted to and output.

Prior art examples related to the present invention are listed in Japanese Patent Application Laid-Open Nos. 4-277823 and 4-922.
56, JP-A-3-296904, JP-A-2
There is a publication of -285804.

[0006]

However, as described above, in the conventional voice limiter device, the input signal is distributed for each band, and each distributed band has a limiter circuit, or only one limiter circuit is provided. Even in this case, the adjustment processing of the level of the input signal is performed separately for each band. Such a circuit configuration increases the circuit scale and complicates filter setting. Further, since the band is divided to control the level of the audio signal, there is a problem that discontinuity occurs at the connection points of the distributed bands, and distortion is likely to occur in the level-adjusted output signal.

It is an object of the present invention to provide a voice limiter device having a simpler circuit configuration and less likely to cause signal distortion.

[0008]

To achieve the above object, a voice limiter device of the present invention comprises an equalizing means for adjusting and outputting the level of an arbitrary frequency component of a digital voice input signal, and an output digital voice. Level detection means for detecting the level of a signal and outputting the detected data, and a predetermined constant for the value of the detected data are stored in advance, and a polygonal line data constant table for outputting a predetermined constant corresponding to the value of the data. Means and a multiplication means for compressing or expanding the level of the digital audio input signal using a constant as a control signal, and the digital audio signal after the level of the digital audio input signal is adjusted by the equalizing means is a control signal of the multiplying means. Is used to adjust the level of a digital voice input signal.

[0009]

According to the voice limiter device of the present invention, the level of the digital voice input signal is adjusted, the level of the adjusted digital voice input signal is detected, and a predetermined constant is output based on the detected value. Is used as a control signal to adjust the level of the digital audio input signal, the level of the digital audio signal can be continuously adjusted without frequency decomposition.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a voice limiter device according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, there is shown an embodiment of the voice limiter device of the present invention. In the circuit configurations of the embodiment and the conventional example, the same reference numerals are added to the same functional units that do not require particular distinction.

The apparatus shown in FIG. 1 comprises an input circuit 2, an equalizing circuit 4, a level detecting circuit 6, a broken line data constant table circuit 8, a multiplying circuit 10, and an output circuit 12.

The input circuit 2 is an AES / EBU (Audio Eng
This is a circuit unit for converting a digital audio signal of the neering Society / European Broadcasting Union) format into a digital audio signal of L and R channels and outputting the converted digital audio input signal.

The equalizing circuit 4 is a circuit section which receives a digital audio signal as an input signal, controls the level of an arbitrary frequency component or an arbitrary frequency component divided in advance, and outputs the controlled equalizing audio signal. FIG. 2 is a characteristic setting example of one of the equalizing circuits and shows a frequency vs. gain characteristic example. This characteristic is approximately 10 ² [Hz] and 10 ³ [Hz]
Is defined as a boundary, and the gain characteristic of each region is defined by dividing into three frequency bands of a low frequency band, a middle frequency band, and a high frequency band. Low side separation frequency of each band 3
2, the high frequency side separation frequency 33 and the slope of each band equalizing curve can be set arbitrarily. Also,
There is no characteristic step at the boundary of each band.

The level detection circuit 6 is a circuit section for detecting the level of an input signal and outputting the detected data. In this embodiment, the equalized digital audio signal output from the equalizing circuit is used as an input signal,
The detection data corresponding to the level of the input signal is output.

The polygonal line data multiplier table 8 is a circuit section that outputs a predetermined constant based on the input data.
Regarding the relationship between the input data and the constant to be output, an input / output characteristic having an arbitrary characteristic is previously stored in an internal memory as a constant table. In the embodiment, the constant to be output is determined according to the state of the data input from the level detection circuit 6.

The multiplication circuit 10 is a circuit portion for compressing or expanding the level of the digital audio signal according to the constant of the control signal.

The output circuit 12 is a circuit section for converting the input digital audio signal into an analog audio signal and outputting the converted analog signal.

In the audio limiter device composed of the above-mentioned respective circuit parts, the digital audio signal of AES / EBU format is converted into the digital input audio signal 3 of L and R channels by the input circuit 2. The equalizing circuit 4 performs gain correction of an arbitrary frequency component on the digital audio input signal 3 separated into the L and R channels. An example of the characteristic of this gain correction is shown in FIG. The equalized audio signal 5 is applied to the level detection circuit 6, and the data whose level has been detected is output as a detection signal. The detection signal 7 is input to the polygonal line data constant table circuit 8. The polygonal line data constant table circuit 8 outputs a constant 9 according to the value of the data of the input detection signal. The constant 9 is input to the multiplication circuit 10, and the characteristic change based on the constant 9 is applied to the digital voice input signal 3. The digital audio signal whose level characteristic has been changed is converted into an analog audio signal 13 by the output circuit 12 and output. An example of the characteristics of the input / output signal based on the above procedure is shown in FIG.

According to the above signal processing, it is possible to arbitrarily set the low frequency side separation frequency 32, the high frequency side separation frequency 33 of each band, and the slope of each band equalizing curve, depending on the type of input signal. It is possible to configure a free limiter characteristic. Further, by applying the equalizing shown in the characteristic curve of FIG. 2 or the like to the input signal 3 in the equalizing circuit 4, it is possible to change the level of the compression ratio to the weighted component. The broken line data constant table circuit 8 and the multiplication circuit 10 constitute a limiter circuit, and the limiter function can be constituted by an extremely simple circuit. With the above configuration, simplification of the circuit, reduction of adjustment man-hours, reduction of distortion signals, etc. can be achieved.

Although the above-described embodiment is a preferred embodiment of the present invention, the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

[0021]

As is apparent from the above description, the voice limiter device of the present invention adjusts the level of a digital voice input signal, detects the level of the adjusted signal, and sets a predetermined constant based on the detected value. Is used as a control signal to adjust the level of the digital audio input signal. Therefore, frequency decomposition of the digital audio signal to be adjusted is not required, the circuit configuration is simplified, and the adjustment and setting are simplified. In addition, since the level of the digital audio input signal in the entire frequency range can be adjusted by the one-loop configuration circuit, continuous level adjustment is ensured and distortion due to the discontinuous characteristic occurs in the adjusted digital audio signal. Never.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a voice limiter device of the present invention.

FIG. 2 is a diagram showing an example of setting frequency characteristics of an equalizing circuit which constitutes the audio limiter device of FIG.

FIG. 3 is a diagram showing an example of input / output characteristics by the voice limiter device of FIG.

FIG. 4 is a block diagram showing a configuration example of a voice limiter device according to a conventional technique.

FIG. 5 is a block diagram showing a configuration example of a voice limiter device according to a conventional technique.

[Explanation of symbols]

 1 Digital voice input signal 2 Input circuit 3 Digital voice signal 4 Equalizing circuit 5 Equalizing voice signal 6 Level detection circuit 7 Level control signal 8 Line data constant table circuit 9 Control constant 10 Multiplier circuit 11 Controlled voice signal 12 Output circuit 13 Output voice signal

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 2, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (1)

[Claims] 1. An equalizing means for adjusting and outputting the level of an arbitrary frequency component of a digital audio input signal, and detecting the level of the output digital audio signal,
Level detection means for outputting the detected data, a predetermined constant for the value of the detected data is stored in advance, polygonal line data constant table means for outputting the predetermined constant corresponding to the value of the data, and A multiplication means for compressing or expanding the level of the digital audio input signal using a constant as a control signal, and controlling the digital audio signal after the level of the digital audio input signal is adjusted by the equalizing means. An audio limiter device, which is used for a signal to adjust the level of the digital audio input signal.