JPH0714136B2 - Digital equalizer device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a digital equalizer device used, for example, in processing a digitized audio signal with desired characteristics.

Background Art and its Problems For example, it is possible to digitize an audio signal and perform arithmetic processing on this digital signal to obtain characteristics of various filters. Figure 1 shows a basic configuration example for that,
In the figure, the digital audio signal from the input terminal (1) is a multiplier (2) having a multiplication coefficient K, an adder (3),
It is output to the output terminal (5) through (4). The signals between the adders (3) and (4) are supplied to the cascade circuits of the delay circuits (6 ₁ ), (6 ₂ ) ... (6 n) having the delay amount Z ⁻¹ , respectively. The outputs of these delay circuits (6 ₁ ) to (6n) are multipliers (7 ₁ ), (7 ₂ ) · with multiplication coefficients a ₁ , a ₂ ... An, respectively.
.. (7n) is supplied to the adder (4) in front.
The delay circuit (6 _1), (6 ₂₎ ... output each multiplier coefficient b ₁ of the (6n), b _2, ... bn multiplier _(81), (8 ₂₎
.. (8n) is supplied to the rear adder (3).

In this circuit, input terminal (1) to output terminal (5)
The transfer function up to It is represented by. Therefore, by changing each coefficient of K, a _{1 to} an, b _{1 to} bn, it is possible to obtain a filter such as a low pass filter, a high pass filter or a band pass filter having an arbitrary frequency characteristic.

Therefore, the above-mentioned circuits are connected in cascade in a plurality of stages (for example, 8 stages), and the characteristics of each circuit are changed in arbitrary frequency bands f _{1 to} f ₈ as shown in FIG. In addition, the so-called graphic equalizer can be configured by adjusting the amplification or attenuation level of the change point independently.

According to this, since all the processing is performed digitally, when processing a PCM audio signal that is put into practical use, there is no fear of sound quality deterioration or the like caused by conventional analog processing, and good and accurate processing is possible. Processing can be performed easily.

By the way, in the case where the above-mentioned graphic equalizer is configured, for example, the required equalizer characteristic may be fixed depending on the place where the apparatus is installed. That is, in general, the interior of a car and the room of a house have different acoustic characteristics and different equalizer characteristics are required, but if this is a user's personal car or room, each characteristic is unique to that location. Will be constant. Also, like classical music and contemporary music, there are optimum equalizer characteristics depending on the genre of the music, and they are considered to be uniquely constant for each genre.

However, in the conventional device, the user has to obtain desired characteristics one by one by operating the setting means, and also the above-mentioned predetermined characteristics have to be adjusted to the characteristics by performing a complicated operation. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and makes it possible to easily obtain predetermined characteristics.

The present invention, setting means for setting a desired property (14 _11-1
4 ₁₈ ), the coefficient table (15) is searched by the setting value from the setting means (14 _{11 to} 14 ₁₈ ) to retrieve the first coefficient corresponding to the desired characteristic, and the first coefficient is obtained. Is stored in a first buffer memory (16), and an input digital signal is arithmetically processed by a coefficient stored in the first buffer memory (16) to obtain the desired characteristics. , The setting means (14 ₁₁ ~
14 ₁₈ ) The memory (1
8), retrieve the second coefficient by searching the coefficient table (15) with the value stored in this memory, store the second coefficient in the second buffer memory (19), A digital equalizer device characterized in that the second buffer memory (19) is switched to the first buffer memory (16) to perform the arithmetic processing of the input digital signal. The predetermined characteristics can be easily obtained.

Embodiment In the case of forming the above circuit, a digital signal processing unit (DSP) including a multiplier, an adder, a coefficient register, etc. is actually used.

That is, in FIG. 3, the data from the input terminal (1) is supplied to the DSP (10) and is output from the DSP (10) to the output terminal (5). A random access memory (RAM) (11) for delaying data storage is connected to the DSP (10), and a memory control unit (MCU) (12) for controlling the RAM (11) is provided. This MCU (12) has a DSP
A signal indicating the status from (10) and a control signal from the host CPU (13) are supplied, and RAM (1
Address of 1) is controlled. Furthermore, for example, the volume (14 ₁ ), (14 ₂ ) ...
- a signal indicating the adjustment position of the (14 ₈₎ is supplied to the CPU (13). And these volumes (14 ₁₎ to in response to a signal from the (14 _8), read-only memory coefficients necessary for the characteristics (a, b) is the coefficient table (ROM) (15)
, The coefficient is set in the first buffer memory (16), the coefficient from this memory (16) is supplied to the DSP (10) through the multiplexer (17), and the CPU (13) Control signals from DSP (10), MCU (1
2) and the multiplexer (17).

Thereby, for example, the operation of the graphic equalizer described above is performed.

Furthermore, in this device, RAM (1
8) is provided, and values corresponding to the set values of the volumes (14 ₁ ) to (14 ₈ ) in a predetermined characteristic are stored at an arbitrary address of the RAM (18). In addition, preset push buttons (14 ₁₁ ) to (14 ₁₈ ) are provided.
An arbitrary address of M (18) is selected. Further, a push button (14S) for set control during presetting is provided together with the push buttons (14 ₁₁ ) to (14 ₁₈ ). Further, a second buffer memory (19) is provided in parallel with the buffer memory (16), and a coefficient corresponding to the value read from the RAM (18) described above is set in the buffer memory (19). Coefficients from (19) DSP through multiplexer (17)
Supplied to (10).

Further, in this device, the control program in the CPU (13) is provided with the following program. FIG. 4 shows a flow chart in which pushbuttons (14 ₁₁ ) to
When (14 ₁₈ ) is operated, the main routine is jumped to and the following subroutine is started.

First, in step [1], the address of the RAM (18) designated by the push buttons (14 ₁₁ ) to (14 ₁₈ ) is read.

Next, at step [2], it is determined whether or not the push button (14S) is operated.

When this operation is, the step [3] by volume (14 ₁₎ to (14 ₈₎ of the value V ₁ ~V ₈ is read in, step in [4] of these values V ₁ ~V ₈ Push button (14 ₁₁ ) ~
It is written to the RAM (18) address specified by (14 ₁₈ ). Then, the process is returned to the main routine.

When the operation is not performed in step [2], the value V ₁ to the value written in the address of the RAM (18) specified by the push buttons (14 ₁₁ ) to (14 ₁₈ ) in step [5] V ₈ is read, the coefficient table is searched using the values of V _{1 to} V ₈ in step [6], the coefficient fetched in step [7] is set in the buffer memory (19), and the step [ 8], the multiplexer (17) is switched. Then, the process is returned to the main routine.

Although the characteristics are changed in this manner, according to the above, it is possible to preset an arbitrary characteristic in the RAM (18) and read it to easily obtain a predetermined characteristic. That is, for example, the address specified by the push button (14 ₁₁ ) stores the equalizer characteristic that matches the acoustic characteristics in the vehicle, and the address specified by the push button (14 ₁₂ ) stores the equalizer characteristic in the room. As a result, desired characteristics can be obtained by simply pressing the push buttons (14 ₁₁ ) and (14 ₁₂ ) when necessary.

Furthermore, by presetting the optimum equalizer characteristics for classical music and modern music, the characteristics can be easily obtained. In this case, since these characteristics are considered to be general-purpose, the values corresponding to these characteristics V _{1 to} V ₈ are written in the ROM (15), and this can be The address of the ROM (15) may be designated.

As a result, the usability for the user can be greatly improved.

Further, when the characteristics are switched, if the coefficients are switched by software, it takes a long time to switch, and there is a possibility that noise and the like may occur due to erroneous processing because the previous coefficient and the subsequent coefficient are transiently mixed. Therefore, in the above-mentioned device, the occurrence of such noise can be prevented by using two buffer memories and temporarily switching them by the multiplexer.

EFFECTS OF THE INVENTION According to the present invention, it becomes possible to easily obtain predetermined characteristics.

[Brief description of drawings]

1 and 2 are diagrams for explaining the background art, FIG. 3 is a configuration diagram of an example of the present invention, and FIG. 4 is a diagram for explaining the same. (1) an input terminal, (5) an output terminal (10) is a digital signal processing unit, (13) the host CPU, (14 ₁₎ ~
(14 ₈ ) is the setting volume, (14 ₁₁ ) to (14 ₁₈ ) are preset push buttons, (15) is the read-only memory,
(16) and (19) are buffer memories, and (18) is a random access memory.

Claims (1)

[Claims] 1. A setting means for setting a desired characteristic, a coefficient table is searched by a setting value from the setting means, a first coefficient corresponding to the desired characteristic is fetched, and the first coefficient is obtained. Is stored in the first buffer memory, and
In the digital equalizer device for arithmetically processing the input digital signal with the coefficient stored in the buffer memory to obtain the desired characteristic, the digital equalizer device has a memory for storing a value corresponding to the set value from the setting means. , Searching the coefficient table with the value stored in this memory,
Is taken out, the second coefficient is stored in the second buffer memory, the second buffer memory is switched to the first buffer memory, and the arithmetic processing of the input digital signal is performed. Characteristic digital equalizer device.