JP5703944B2 - Equalizer, equalizer adjustment method, and program - Google Patents

Description

  The present invention relates to an equalizer, an equalizer adjustment method, and a program.

  For example, an equalizer divides the frequency band of the playback sound in an audio playback device, etc., increases or decreases the gain (level) of each frequency band, adjusts the expression of music or sound with fine nuances, Used to cut.

  The graphic equalizer includes a setting screen that displays a setting gain of each band. Many graphic equalizer setting screens display the gain set for each band in a bar graph as shown in FIG. The user changes the frequency characteristics of bass and treble while watching the display on the setting screen.

  The conventional graphic equalizer adjusts the gain of each band by a peaking filter. For this reason, the frequency-gain characteristic set on the setting screen is different from the actually set frequency-gain characteristic.

  For example, even if the user sets and sets the gain of each band as shown in FIG. 11 on the setting screen, the actually set frequency-gain characteristics are as shown in FIG. In the setting of FIG. 11, the gain is the same in the band where the center frequency is 1 kHz and the band of 4 kHz. However, in the actually set frequency-gain characteristics, a gain valley is formed between 1 kHz and 4 kHz. .

  Further, even if the gains of the respective bands are set to be equal as shown in FIG. 13 in order to make the gains in all the bands the same, the actually set frequency-gain characteristics are as shown in FIG. Thus, a valley is formed between the gains of the respective bands.

  In order to cope with such a problem, the graphic equalizer disclosed in Patent Document 1 uses three peaking filters when setting the gain of the band of interest, and further sets the gain of adjacent bands in conjunction with each other. To do. Thereby, the peak property of each band is eased.

Japanese Unexamined Patent Publication No. 7-111893

  In the conventional graphic equalizer, since the frequency-gain characteristic of the sound is adjusted by the peaking filter, there is a possibility that the sound imagined by the user is not reproduced.

  Even if the peaking filter of a plurality of bands is used as in Patent Document 1 and the sharpness is moderated to improve the fluctuation between the bands, the frequency characteristics are realized by the peaking filter. It does not become flat characteristics. Furthermore, since three filters are used for one setting, there is a problem that processing power cannot be assigned by an inexpensive DSP (Digital Signal Processor).

The present invention has been made in view of the above problems, and an object thereof is to provide an equalizer in which a frequency-gain characteristic set by a user and an actual frequency-gain characteristic are approximated.
Another object of the present invention is to provide an equalizer that can obtain a desired frequency-gain characteristic with a simple configuration.

In order to achieve the above object, an equalizer according to the first aspect of the present invention includes:
An operation accepting unit for accepting an operation for designating a gain set for each of a plurality of frequency bands in the input signal;
A plurality of filters for filtering the input signal for each of the plurality of frequency bands based on a parameter including a filter coefficient and a bit shift amount ;
Based on the specified gain by the operation acceptance unit operation received by, e Bei and a setting unit for setting the parameter,
When there is a frequency band group in which a difference in gain set in adjacent frequency bands among the plurality of frequency bands is equal to or less than a predetermined reference value, the setting unit includes the frequency band among the plurality of filters. Setting the parameters so that the filters corresponding to the frequency bands at both ends of the group become shelving filters;
It shall be the features a.

For example, when the frequency band group includes three or more frequency bands , the setting unit is a frequency band other than the frequency bands at both ends of the frequency band group among the plurality of filters, and the frequency band group The parameter is set so that the frequency-gain characteristic of the filter corresponding to the frequency band included in the filter becomes flat .

For example, the setting unit sets the parameter so that a filter corresponding to a frequency band that is not included in the frequency band group among the plurality of frequency bands among the plurality of filters becomes a peaking filter .

For example, when the difference between all the gains set in the plurality of frequency bands is equal to or less than a predetermined reference value , the setting unit performs the operation of a specific filter among the plurality of filters only with a coefficient of one filter. The parameter is set so that the frequency-gain characteristics of filters other than the specific filter among the plurality of filters are flat .

For example, the setting unit updates the parameter every time the gain designated by the operation received by the operation receiving unit is updated.

In order to achieve the above object, an equalizer adjustment method according to a second aspect of the present invention includes:
An operation receiving step in which an operation receiving unit receives an operation of designating a gain set in each of a plurality of frequency bands in the input signal;
A plurality of filters, said input signal, and a plurality of filters step of filtering for each of the plurality of frequency bands based upon parameters including the coefficient of the filter and the bit shift amount,
Setting unit, based on the specified gain by the operation accepted by the accepting step operation, seen including a setting step, the setting the parameters,
In the setting step, when there is a frequency band group in which a gain difference set in an adjacent frequency band among the plurality of frequency bands is equal to or less than a predetermined reference value in the setting step, the setting unit Among these, the parameters are set so that filters corresponding to the frequency bands at both ends of the frequency band group are shelving filters .

In order to achieve the above object, a program according to the third aspect of the present invention provides:
On the computer,
An operation acceptance function for accepting an operation for designating a gain set for each of a plurality of frequency bands in the input signal;
A plurality of filter functions for filtering the input signal for each of the plurality of frequency bands based on a parameter including a filter coefficient and a bit shift amount ;
A setting function for setting the parameter based on the gain designated by the operation received by the operation reception function ;
Is a program that realizes
When there is a frequency band group in which a difference in gain set in adjacent frequency bands among the plurality of frequency bands is equal to or less than a predetermined reference value, the setting function includes the frequency among the plurality of filter functions. The parameter is set so that the filter function corresponding to the frequency bands at both ends of the band group becomes the shelving filter function .

  According to the present invention, it is possible to realize an equalizer that approximates a frequency-gain characteristic set by a user and an actual frequency-gain characteristic.

It is a block diagram of the graphic equalizer which concerns on embodiment of this invention. It is a block diagram which shows the principal part of the equalizer process part in FIG. It is a figure for demonstrating the frequency-gain characteristic of a peaking filter and a shelving filter. It is a flowchart which shows the operation | movement which sets the frequency-gain characteristic of a graphic equalizer. It is a figure which shows the example of the gain according to the frequency band which a user sets. It is a figure which shows the example of the gain according to the frequency band which a user sets. It is a figure for demonstrating the actual frequency-gain characteristic of a graphic equalizer when the setting shown in FIG. 11 is made. It is a figure which shows the gain for every zone | band set by the user, and the frequency-gain characteristic actually set. It is a figure for demonstrating the actual frequency-gain characteristic of a graphic equalizer in another example when the setting shown in FIG. 13 is made. It is a figure which shows the other example by which all the bands are set to the same gain. It is a figure which shows the bar graph displayed on a setting screen. It is a figure which shows the frequency-gain characteristic actually set by the setting screen shown in FIG. It is a figure which shows the example of the gain which a user sets. It is a figure which shows the frequency-gain characteristic actually set by the setting screen shown in FIG.

  Hereinafter, a graphic equalizer 100 according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the graphic equalizer 100 according to the present embodiment includes a microcomputer 10, a DSP (Digital Signal Processor) 20 connected to the microcomputer 10, and a user interface unit 30 connected to the microcomputer 10. It is equipped with.

  The user interface unit 30 includes a display 31 constituted by a display and the like, and an operation unit 32 such as a key and a mouse operated by a user.

  The DSP 20 includes an equalizer processing unit 21 that functions in cooperation with the microcomputer 10 to divide the frequency band of the input audio signal into a plurality of parts and adjust and output the gain (level) for each band.

  As shown in FIG. 2, the equalizer processing unit 21 includes a plurality of cascaded IIR filters 21-1, 21-2, 21-3,. The IIR filters 21-1, 21-2, 21-3,... Are respectively provided corresponding to bands obtained by dividing the frequency band of the audio signal, and the IIR filters 21-1, 21-2, 21-3. ,... Is the same as the number n of bands obtained by dividing the frequency band of the audio signal. Each of the IIR filters 21-1, 21-2, 21-3,... Is used to adjust the gain of the signal component in the assigned frequency band.

  The IIR filter 21-1 includes four delay units 210, 211, 212, 213, five multiplication units 214, 215, 216, 217, 218, and one addition unit 219, for example, a sound source Digital data to be processed is supplied from an apparatus or the like. The digital data is 16-bit data, for example.

  The input terminal T1 of the IIR filter 21-1 is connected to the input terminals of the delay unit 210 and the multiplication unit 214. The delay unit 210 delays the data supplied from the input terminal T1 by one sampling time. The multiplier 214 multiplies the data given from the input terminal T1 by a preset coefficient a0.

An input terminal of the delay unit 211 and the multiplication unit 215 is connected to the output terminal of the delay unit 210, and an input terminal of the multiplication unit 216 is connected to the output terminal of the delay unit 211.
The delay unit 211 delays the output data of the delay unit 210 by one sampling time.

The multiplier 215 multiplies the output data of the delay unit 210 by a preset coefficient a1.
The multiplier 216 multiplies the output data of the delay unit 211 by a preset coefficient a2.

  The output terminals of the multiplication units 214, 215, and 216 are connected to the input terminal of the 5-input adder 219.

The input terminal of the delay unit 212 is connected to the output terminal of the adder 219 via a bit shifter 220 described later. The delay unit 212 delays the output data of the adder 219 by one sampling time.
An output terminal of the delay unit 212 is connected to an input terminal of the delay unit 213 and the multiplication unit 217. The input terminal of the multiplication unit 218 is connected to the output terminal of the delay unit 213. The delay unit 213 delays the output data of the delay unit 212 by one sampling time. The multiplication unit 217 multiplies the output data of the delay unit 212 by a preset coefficient b1. The multiplication unit 218 multiplies the output data of the delay unit 213 by a preset coefficient b2.

  The input terminal of the adder 219 is connected to the output terminal of the multiplier 217 and the output terminal of the multiplier 218. The output of the adder 219 becomes the output of the IIR filter 21-1, and the output terminal of the adder 219 is connected to the terminal T2.

  The IIR filter 21-1 further includes a bit shifter 220 that bit-shifts the output data of the adder 219. By bit shifting the data with the bit shifter 220, it is possible to divide the data by a power of 2 or to multiply the data by a power of 2.

  Each of the IIR filters 21-2, 21-3,... 21-n has the same configuration as that of the IIR filter 21-1, and includes four delay units 210, 211, 212, 213 and five multiplications. Units 214, 215, 216, 217, and 218, an adder 219, and a bit shifter 220.

  IIR filters 21-1, 21-2, 21-3,... Are the coefficients a0, a1, a2, b1, b2 of the multiplication units 214, 215, 216, 217, 218 and the bit shift amount of the bit shifter 220. Various filters can be obtained by changing the setting.

  The IIR filters 21-1, 21-2, 21-3,... Have coefficients a0, a1, a2, b1, b2, and so on so as to function as peaking filters or shelving filters. The bit shift amount of the bit shifter 220 is set.

  As shown in FIG. 3, the peaking filter has a mountain-shaped frequency-gain (level) characteristic having a peak at a certain frequency (center frequency). On the other hand, the shelving filter has a shelf-type frequency-gain characteristic having a gain set from a certain frequency (cut-off frequency). Among the input signals, a shelving filter that raises or lowers the signal level of the signal component with a frequency lower than the cutoff frequency by a certain level is called the Low Shelving Filter, and the signal level of the signal component with a frequency higher than the cutoff frequency. The process of raising or lowering a certain level is called High Shelving Filter.

  A combination of the frequency-gain characteristics of the respective IIR filters 21-1, 21-2, 21-3,... Is the actual frequency-gain characteristics of the graphic equalizer 100.

Next, the operation of the graphic equalizer 100 will be described.
First, an operation for setting the frequency-gain characteristic of the graphic equalizer 100 will be described.

  FIG. 4 is a flowchart showing an operation for setting the frequency-gain characteristic of the graphic equalizer 100.

  When the user sets a gain for the graphic equalizer 100, the microcomputer 10 displays a setting screen for setting the gain on the display 31. The user operates the operation unit 32 while viewing the setting screen, and sets the gain for each frequency band.

  The microcomputer 10 checks the gain for each band set by the user and starts the setting change process shown in FIG. 4 every time one of the settings is changed. First, the microcomputer 10 is adjacent to each other with the same gain set. It is determined whether there is a band group including the band (step S10).

  For example, in an equalizer that divides an input audio signal into four bands whose center frequencies are 62.5 Hz, 250 Hz, 1 kHz, and 4 kHz, as shown in FIG. 11, the gain of the band of 62.5 Hz is 9 dB and the band of 250 Hz. If the gain is set to -5 dB, the 1 kHz band and the 4 kHz band are set to 3 dB, the adjacent 1 kHz band and the 4 kHz band are set to the same gain. It is determined that there is a band group including the band to be performed (step S10; YES).

  Also, for example, as shown in FIG. 13, if the gains of all bands of 62.5 Hz to 16 kHz are set to 9 dB, there are band groups because adjacent bands are set to the same gain ( Step S10; YES).

  On the other hand, for example, as shown in FIG. 5, if the gain of the 62.5 Hz band is set to 1 dB, the gain of the 250 Hz band is set to 3 dB, the 1 kHz band is set to 5 dB, and the gain of the 4 kHz band is set to 7 dB. Since there is no band adjacent to the gain, it is determined that the corresponding band group does not exist (step S10; NO).

  For example, as shown in FIG. 6, if the gain of the 62.5 Hz band is set to 5 dB, the gain of the 250 Hz band is set to 1 dB, the 1 kHz band is set to 9 dB, and the gain of the 4 kHz band is set to 5 dB. The gains of the .5 Hz band and the 4 kHz band are the same, but since both bands are not adjacent, it is determined that there is no corresponding band group (step S10; NO).

  When there is no band group set to the same gain as the adjacent bands (step S10: NO), for the IIR filters 21-1, 21-2, 21-3,. The coefficients a0, a1, a2, b1, b2 and the bit shift amount of the bit shifter 220 are set so that the peaking filter becomes the peak set by the user at the frequency-gain characteristic peak (step S11).

  For example, the frequency band of the input audio signal is divided into four bands with a center frequency of 62.5 Hz, 250 Hz, 1 kHz, 4 kHz, and divided into four bands with a center frequency of 62.5 Hz, 250 Hz, 1 kHz, 4 kHz. In the equalizer, when the user sets the gain of the band whose center frequency is 62.5 Hz to 9 dB, the bit shift amount of the coefficients a0, a1, a2, b1, b2 of the IIR filter 21-1 and the bit shifter 220 is set. Is set so that the frequency-gain characteristic of the peaking filter having a peak at 62.5 Hz and a peak value of 9 dB can be obtained.

  For each band whose center frequency is 250 Hz, 1 kHz, and 4 kHz, the coefficients a0, a1, a2, b1, b2 of the IIR filters 21-2, 21-3, and 21-4 and the bit shifter 220 are set according to the set gain. Set each bit shift amount.

  On the other hand, if it is determined that there is a band group set to the same gain as the adjacent band (step S10: YES), the IIR filters 21-1, 21-2 corresponding to the bands at both ends of the band group are determined. 21-3,... Are shelving filters, the coefficients a0, a1, a2, b1 so that the center frequencies of the bands at both ends become the cutoff frequencies and the frequency-gain characteristics are appropriate. , B2 and the bit shift amount of the bit shifter 220 are set (step S12).

  Here, of the bands at both ends of the band group with the same level, if the set gain is a positive value for the band on the low frequency side, a high shelving filter is set, and the set gain is If negative, set low shelving filter. The height of the shelf is set to a value equal to the set gain. Of the bands at both ends of the same level band group, if the set gain is a positive value for the high frequency band, a low shelving filter is set and the set gain is negative. If the value is, set the high shelving filter. The height of the shelf is a value obtained by inverting the sign of the set gain.

  For example, in the setting example of FIG. 11, the gains in the bands with the center frequencies of 1 kHz and 4 kHz are the same at 3 db and are adjacent to each other, respectively, at both ends of the band group. For this reason, the IIR filter 21-3 in charge of the 1 kHz band, that is, the low frequency end side, has a cutoff frequency of 1 kHz, a high frequency gain of 3 dB, and a low frequency gain of 0 dB (shelf height of 3 dB). ) Shelving filter. Further, the IIR filter 21-4 in charge of the 4 kHz band, that is, the high frequency end side, has a cutoff frequency of 4 kHz, a low frequency gain of 3 dB, a high frequency gain of 0 dB (a shelf height of −3 dB). ) Low shelving filter.

  Similarly, for example, in the setting example of FIG. 13, the IIR filter 21-1 in charge of the band having the center frequency of 62.5 Hz, that is, the low-frequency end side, the gain of the high-frequency side with the cutoff frequency of 62.5 Hz. Is set to a high shelving filter having a gain of 9 dB and a low-frequency gain of 0 dB (shelf height of 9 dB). Further, the IIR filter 21-5 in charge of the 16 kHz band, that is, the high band end side, has a cutoff frequency of 16 kHz, a low band gain of 9 dB, and a high band gain of 0 dB (the shelf height is −9 dB). ) Low shelving filter.

  After the end of step S12, the number of bands included in the band group composed of adjacent bands set to the same gain is determined, and when the band group includes three or more bands (step S13: 3 bands or more), coefficients a0, a1, a2, b1, b2 of the IIR filters 21-1, 21-2, 21-3,. The bit shift amount is set so that the frequency-gain characteristic is flat (step S14). This setting can be set by setting the coefficient a0 to 1.0, the other coefficients a1, a2, b1, b2 to 0, and the bit shift amount of the added data to 0.

  For example, in the setting example of FIG. 13, since the number of bands included in the band group composed of adjacent bands whose gains are set to be the same is 5, the band included in the band group is 3 bands or more. It is determined that there is (step S13: 3 bands or more), and the frequency frequencies and gain characteristics of the IIR filters 21-2, 21-3, and 21-4, which are in charge of the 250 Hz, 1 kHz, and 4 kHz bands excluding both ends, are flattened. (Step S13).

  On the other hand, in step S13, when the number of consecutive bands set with the same gain is two bands (step S13: two bands) or when the process of step S14 is completed, the presence / absence of an unset IIR filter is determined. When there is an unset IIR filter, the coefficients a0, a1, a2, b1, b2 are set so that the peak value of the frequency-gain characteristic becomes the peaking filter of the gain set by the user, as in step S11. The bit shift amount of the bit shifter 220 is set (step S15).

  When the process of step S11 or the process of step S15 is completed, the operation for setting and updating the frequency-gain characteristic of the graphic equalizer 100 is completed.

  Thereafter, whenever the user operates the operation unit 32 to change the gain of any frequency band, the microcomputer 10 performs the setting process of FIG. 4 in response to the notification from the user interface 30. A frequency-gain characteristic corresponding to the change is obtained.

  Thereafter, when data is input from a playback device or the like, the IIR filter 21-1. . . Filter the input data in accordance with the setting, and the IIR filter 21-2. . . Forward to. The output of the final stage IIR filter 21-n becomes the output of the equalizer processing unit 21.

  Here, the actual frequency-gain of the filter constituted by the IIR filters 21-1, 21-2, 21-3, ... in which the coefficients a0, a1, a2, b1, b2 and the bit shift amount are set. The characteristics will be described.

  FIG. 7 is a diagram for explaining the comparison between the frequency-gain characteristic of the conventional graphic equalizer 100 and the frequency-gain characteristic of the graphic equalizer 100 of the present embodiment.

  As shown in FIG. 11, the user has a gain of 9 dB for a band with a center frequency of 62.5 Hz, a gain of a band for a center frequency of 250 Hz is -5 dB, a band with a center frequency of 1 kHz is 3 dB, and a center frequency is 4 kHz. Assume that the bandwidth is set to 3 dB. In this case, in the conventional graphic equalizer 100 using only the peaking filter, the actual frequency-gain characteristic becomes the characteristic shown by the broken line in FIG. 5 (equal to the characteristic shown in FIG. 12), and around 2 kHz between 1 kHz and 4 kHz. Gain drops.

  On the other hand, in the graphic equalizer 100 of the present embodiment, the frequency-gain characteristic of the shelving filter that lifts the high frequency side by 3 dB is applied to the band with the center frequency of 1 kHz, and the high frequency side is lowered by 3 dB to the 4 kHz band. The frequency-gain characteristic of the shelving filter is applied. For this reason, the frequency-gain characteristic between 1 kHz and 4 kHz is flattened as shown by the solid line in FIG. 7, and becomes a characteristic more in line with the user's awareness than before.

  When the gain for each band set by the user on the setting screen is superimposed on the frequency-gain characteristic indicated by the solid line in FIG. 7, the result is as shown in FIG. 8, and the frequency-gain characteristic is close to the user's image. I understand that. Therefore, it is possible to reproduce an audio signal without a sense of incongruity.

  In addition, as shown in FIG. 13, in an equalizer that divides the frequency band of an input audio signal into five bands whose center frequencies are 62.5 Hz, 250 Hz, 1 kHz, 4 kHz, and 16 kHz, Assume that 9 dB is set for all gains.

  In this case, the frequency-gain characteristic of the conventional graphic equalizer 100 using only the peaking filter becomes a characteristic indicated by a broken line in FIG. 9 (equal to the characteristic shown in FIG. 14), and a drop occurs between the bands.

  On the other hand, in the graphic equalizer 100 according to the present embodiment, when the same gain is set in the continuous band by the user, the frequency-gain characteristics of the shelving filter are applied to the bands at both ends, and the band between them is set. A flat frequency-gain characteristic is applied. Therefore, as shown by a solid line in FIG. 9, no drop occurs between the bands.

  As described above, according to the graphic equalizer 100 of the present embodiment, it is possible to set the frequency-gain characteristic approximate to the frequency-gain characteristic set by the user. Further, the number of IIR filters according to the number of bands can be used.

In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. Examples of such modifications are as follows.
(1) If all the gains of the bands set by the user are the same, a filter that raises the overall flat frequency-gain characteristic to the gain set by the user without using a shelving filter may be used. Good.

  For example, in an equalizer that divides an input audio signal into five bands whose center frequencies are 62.5 Hz, 250 Hz, 1 kHz, 4 kHz, and 16 kHz, the user can set all the gains of the five bands to 9 dB (input / output voltage ratio). 2.8), the coefficient a0 is set to 0.7 for any one of the IIR filters 21-1, 21-2, 21-3,. , B1 and b2 are set to 0, and the bit shift amount of the added data is set to 2. The other IIR filters 21-1, 21-2, 21-3,..., The coefficient a0 are set to 1.0, the coefficients a1, a2, b1, b2 are set to 0, and the bits of the addition data Set the shift amount to zero. With this setting, as shown in FIG. 10, a flat frequency-gain characteristic with a gain of 9 dB in all bands can be obtained.

  (2) In the above embodiment, when two or more frequency bands are installed at the “same gain”, the IIR filters corresponding to the frequency bands at both ends are set as shelving filters. Here, the same is not limited to the case of being completely the same. For example, the absolute value of the difference is 1 dB or less, and the absolute value of the difference is 10% or less of the gain set in the adjacent frequency band. The IIR filter may be set as a shelving filter when it is equal to or less than the reference value.

  In addition, although an example in which an IIR (Infinite Impulse Response) filter is used as a filter has been shown, other digital filters, for example, an FIR (Finite Impulse Response) filter can also be used. is there.

  (3) In the above-described embodiment, the gain for the digital audio signal is set by the digital filter configured by the DSP 20, but a plurality of analog filters are provided, and the type of analog filter and the frequency-gain characteristics of the analog filter are A variable analog equalizer may be used.

  (4) The filter setting processing program shown in FIG. 4 can be stored and distributed in a recording medium, and the program can be installed in the microcomputer 10 from the recording medium and executed.

  (5) The system configuration, display examples, and numerical values are examples, and are not limited to these.

10 Microcomputer 20 DSP
DESCRIPTION OF SYMBOLS 21 Equalizer process part 21-1-21-3 IIR filter 210-213 Delay part 214-218 Multiplication part 219 Adder part 220 Bit shifter 30 User interface part 31 Indicator 32 Operation part

Claims (7)

An operation accepting unit for accepting an operation for designating a gain set for each of a plurality of frequency bands in the input signal;
A plurality of filters for filtering the input signal for each of the plurality of frequency bands based on a parameter including a filter coefficient and a bit shift amount ;
Based on the specified gain by the operation acceptance unit operation received by, e Bei and a setting unit for setting the parameter,
When there is a frequency band group in which a difference in gain set in adjacent frequency bands among the plurality of frequency bands is equal to or less than a predetermined reference value, the setting unit includes the frequency band among the plurality of filters. Setting the parameters so that the filters corresponding to the frequency bands at both ends of the group become shelving filters;
An equalizer characterized by that. The setting unit of the previous SL if the frequency band group comprises three or more frequency bands, among the plurality of filters, a frequency band other than both ends of the frequency band group, the frequency band group frequency filter that corresponds to the frequency band included in - gain characteristic, it sets the parameters so that the flat,
The equalizer according to claim 1 . The setting unit, among the plurality of filters, the plurality of the filters that correspond to the frequency band that is not included in the frequency band group of the frequency band, sets the parameters so that the peaking filter,
Equalizer according to claim 1 or 2, characterized in that.   The setting unit defines an operation of a specific filter among the plurality of filters only by a coefficient of one filter when a difference between all the gains set in the plurality of frequency bands is equal to or less than a predetermined reference value. The parameter is set so that the frequency-gain characteristics of the filters other than the specific filter out of the plurality of filters are flat.
  The equalizer according to any one of claims 1 to 3, wherein: The setting unit updates the parameter every time the gain designated by the operation received by the operation receiving unit is updated.
The equalizer according to any one of claims 1 to 4, wherein the equalizer is provided. An operation receiving step in which an operation receiving unit receives an operation of designating a gain set in each of a plurality of frequency bands in the input signal;
A plurality of filters, said input signal, and a plurality of filters step of filtering for each of the plurality of frequency bands based upon parameters including the coefficient of the filter and the bit shift amount,
Setting unit, based on the specified gain by the operation accepted by the accepting step operation, seen including a setting step, the setting the parameters,
In the setting step, when there is a frequency band group in which a gain difference set in an adjacent frequency band among the plurality of frequency bands is equal to or less than a predetermined reference value in the setting step, the setting unit Among them, the parameters corresponding to the frequency bands at both ends of the frequency band group are set so that the filter becomes a shelving filter,
Equalizer adjustment method. On the computer,
An operation acceptance function for accepting an operation for designating a gain set for each of a plurality of frequency bands in the input signal;
A plurality of filter functions for filtering the input signal for each of the plurality of frequency bands based on a parameter including a filter coefficient and a bit shift amount ;
A setting function for setting the parameter based on the gain designated by the operation received by the operation reception function ;
A program to realize,
When there is a frequency band group in which a difference in gain set in adjacent frequency bands among the plurality of frequency bands is equal to or less than a predetermined reference value, the setting function includes the frequency among the plurality of filter functions. Setting the parameter so that the filter function corresponding to the frequency bands at both ends of the band group becomes a shelving filter function;
Program .

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