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JP2018026615

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DESCRIPTION JP2018026615
Abstract: To perform correction processing in accordance with an output level. SOLUTION: DAP1
calculates a correction value based on a threshold value and an effective value of gain when the
effective value of gain of the equalizer filter is equal to or larger than a predetermined threshold
value, and corrects the equalizer filter based on the correction value. The DSP 8 includes a DSP 8
that calculates the corrected equalizer filter and changes the frequency characteristic of the
audio signal based on the corrected equalizer filter. The DSP 8 changes the threshold according
to the volume. [Selected figure] Figure 3
Equalizer apparatus and equalizer program
[0001]
The present invention relates to an equalizer apparatus that performs equalizer processing for
changing frequency characteristics of an audio signal, and an equalizer program.
[0002]
The equalizer device performs equalizer processing based on an equalizer filter (equalizer
information) indicating a gain with respect to frequency (see, for example, Patent Document 1).
The equalizer device stores, for example, an equalizer filter corresponding to a genre such as
rock, pop, jazz, etc., and the user can select the equalizer filter according to the genre.
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[0003]
In order to protect the hearing from the sound pressure reproduced from headphones (including
so-called earphones), the sound pressure regulation for portable audio devices is mainly
performed in Europe. When measuring the sound pressure output from the headphones, it is
necessary to measure the audio signal on which the equalizer processing has been performed.
[0004]
The applicant has applied for Japanese Patent Application No. 2016-076539 on April 6, 2016. In
Japanese Patent Application No. 2016-076539, when the effective value of the gain of the
equalizer filter is equal to or more than a predetermined threshold value, the correction value is
calculated based on the threshold value and the effective value of the gain. Then, the equalizer
filter is corrected based on the calculated correction value.
[0005]
JP 2012-084949 A
[0006]
However, in Japanese Patent Application No. 2016-076539, there is a problem that correction
processing is always performed even when the output level is considerably smaller than the
sound pressure regulation.
[0007]
An object of the present invention is to perform correction processing according to the output
level.
[0008]
The equalizer apparatus according to the first aspect of the invention calculates a correction
value based on the threshold value and the effective value when the effective value of the gain of
the equalizer information is equal to or more than a predetermined threshold value, and The
signal processing unit is configured to calculate corrected equalizer information in which the
equalizer information is corrected, and to change the frequency characteristic of the audio signal
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based on the corrected equalizer information, and the signal processing unit changes the
threshold according to volume. It is characterized by
[0009]
In the present invention, the signal processing unit changes the threshold according to the
volume.
As a result, when the volume is small, the correction of the equalizer information is not
performed, so that the correction process can be performed according to the output level.
[0010]
An equalizer apparatus according to a second aspect of the invention is the equalizer apparatus
according to the first aspect, wherein the signal processing unit applies a test signal to the
equalizer information as a weighting function, and the frequency characteristic of the equalizer
information obtained by applying the test signal is effective. A first effective value which is a
value is calculated, a second effective value which is an effective value of the frequency
characteristic of the test signal is calculated, and the equalizer information of the equalizer
information is calculated based on the first effective value and the second effective value. A third
effective value which is the effective value of the gain is calculated.
[0011]
In the present invention, the signal processing unit applies the test signal as the weighting
function to the equalizer information, and calculates the correction value using the equalizer
information applied with the test signal.
Then, the signal processing unit calculates corrected equalizer information obtained by
correcting the equalizer information based on the correction value.
As described above, since equalizer information is corrected using equalizer information to which
a test signal is applied as a weighting function in consideration of a test signal, even when a test
signal is input, the corrected correction equalizer information corrected does not limit Audio
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signal can be output.
[0012]
An equalizer apparatus according to a third invention is characterized in that, in the equalizer
apparatus according to the second invention, the signal processing unit calculates the correction
value by dividing the threshold value by the third effective value.
[0013]
An equalizer apparatus according to a fourth aspect of the present invention is the equalizer
apparatus according to the second or third aspect, wherein the signal processing unit divides the
first effective value by the second effective value to obtain the third effective value. It is
characterized by calculating.
[0014]
The equalizer apparatus of the fifth invention is the equalizer apparatus of any of the second to
fourth inventions, wherein the signal processing unit calculates the correction equalizer
information by multiplying the equalizer information by the correction value. It is characterized
by
[0015]
The equalizer apparatus according to a sixth aspect of the present invention is the equalizer
apparatus according to any of the second to fifth aspects, wherein the signal processing unit
transmits the equalizer information to which the test signal is applied, and the equalizer
information to which the test signal is applied. The first effective value is calculated by taking the
square root of the sum of the values at each frequency of the product of N and a complex
number complex.
[0016]
An equalizer apparatus according to a seventh invention is the equalizer apparatus according to
any one of the second to sixth inventions, wherein the signal processing unit operates at each
frequency of a product of the test signal and a complex number conjugate to the test signal. The
second effective value is calculated by taking the square root of the sum of values.
[0017]
An equalizer apparatus according to an eighth invention is characterized in that, in the equalizer
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apparatus according to any of the second to seventh inventions, the test signal is program
simulation noise.
[0018]
An equalizer apparatus according to a ninth aspect of the present invention is the equalizer
apparatus according to any of the second through eighth aspects, further comprising: a control
unit that receives the setting of the parameter of the equalizer information, and the signal
processing unit receives the control unit. The equalizer information is generated by interpolating
the parameters.
[0019]
The equalizer program according to a tenth aspect of the present invention is the equalizer
program, wherein the signal processing unit of the computer calculates a correction value based
on the threshold and the effective value when the effective value of the gain of the equalizer
information is equal to or greater than a predetermined threshold It is characterized in that
calculation of correction equalizer information in which the equalizer information is corrected
based on a value, and change of a frequency characteristic of an audio signal based on the
correction equalizer information are executed.
[0020]
According to the present invention, correction processing can be performed according to the
output level.
[0021]
It is a block diagram showing the composition of DAP concerning the embodiment of the present
invention.
It is a figure which shows the structure of the application of DAP.
It is a flowchart which shows the processing operation of DAP when volume value is changed.
It is a flowchart which shows the processing operation of DAP in the case of producing |
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generating the correction | amendment equalizer filter which correct | amended the equalizer
filter.
It is a figure which shows the parameter which received the setting.
It is a figure which shows an equalizer filter.
It is a figure which shows the equalizer filter which applied the weighting function.
It is a figure which shows an example of an equalizer filter.
It is a figure which shows the effective value of the output voltage of a headphone terminal.
[0022]
Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a digital audio player according to the present embodiment (hereinafter referred to as
"DAP").
Is a block diagram showing the configuration of.
The DAP 1 functions as an equalizer device that changes the frequency characteristics of the
audio signal by executing the music reproduction program P (equalizer program) stored in the
storage unit 5. As shown in FIG. 1, the DAP 1 includes a central processing unit (CPU) 2, a read
only memory (ROM) 3, a random access memory (RAM) 4, a storage unit 5, a display unit 6, an
operation unit 7, and a digital signal processor (DSP). Processor) 8, D / A converter (hereinafter
referred to as "DAC"). 9) amplifiers 10 and 11, wireless module 12, USB interface (hereinafter
referred to as "USB I / F". ) Provided.
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[0023]
The CPU 2 (control unit) controls each unit constituting the DAP 1 in accordance with an
application program including a control program, an OS program, and a music reproduction
program P. The ROM 3 stores a control program. The RAM 4 functions as a main memory of the
CPU 2. The storage unit 5 is a flash memory for storing an OS program, a program such as an
application program including the music reproduction program P, and various data such as
digital audio data. The storage unit 5 is not limited to the illustrated configuration, and may be an
HDD (Hard Disk Drive) or the like.
[0024]
The display unit 6 is for displaying various images (including still images and moving images),
and is configured of a liquid crystal panel. The operation unit 7 includes operation keys for
performing various settings, and a touch panel interlocked with the display unit 6. The user can
perform various character inputs and settings via the operation unit 7. Also, the user can set
parameters of the equalizer filter (equalizer information) via the operation unit 7.
[0025]
The DSP 8 (signal processing unit) performs signal processing such as equalizer processing on
digital audio data. The DAC 9 D / A converts digital audio data into analog audio data. The
amplifiers 10 and 11 amplify analog audio data D / A converted by the DAC 9 and output the
amplified data to the headphone 100. The wireless module 12 is for performing wireless
communication in accordance with the Bluetooth (registered trademark) standard and the Wi-Fi
standard. The DAP 1 can communicate with an external server via the wireless module 12. The
USB I / F 13 is for performing communication in accordance with the USB standard. The DAP 1
can communicate with a personal computer via the USB I / F 13.
[0026]
Next, the processing operation of the DAP 1 when the volume value is changed will be described.
FIG. 2 is a diagram showing the configuration of an application of DAP1. DAP1 is equipped with
Android (registered trademark) OS. At the time of music playback, music playback is performed
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according to a framework provided by Android (registered trademark). The framework includes
Digital Volume and Volume Manager. Digital volume adjusts the volume of digital audio data. The
volume manager manages volumes, such as accepting volume changes. The application
(Application) includes a volume observer (Volume Observer) and an equalizer (Equalizer). The
volume observer monitors system volume volume values. The equalizer performs equalizer
processing on digital audio data.
[0027]
FIG. 3 is a flowchart showing the processing operation of the DAP 1 when the volume value is
changed. When detecting the change of the volume value (S11), the DSP 8 calculates the
headroom of the digital volume from the volume value and the audio route (S12). Next, the DSP 8
updates the threshold from the head room (S13).
[0028]
Next, the processing operation of DAP 1 in the case of generating a corrected equalizer filter in
which the equalizer filter is corrected will be described based on the flowchart shown in FIG. The
CPU 2 receives the setting of the equalizer filter parameter (S1). As shown in FIG. 5, the user can
set the parameters of the equalizer filter by means of a touch panel linked to the display unit 6.
The CPU 2 receives the touch position as a parameter of the equalizer filter, for example, by the
touch panel. Next, the DSP 8 generates an equalizer filter by interpolating the parameters
received by the CPU 2 (S2). The DSP 8 generates an equalizer filter as shown in FIG.
[0029]
Next, the DSP 8 applies a weighting function to the equalizer filter (S3). Here, the weighting
function is a frequency characteristic of program simulation noise. Program simulation noise is a
test signal used for measurement in the European sound pressure regulation (For program
simulation noise, http://www.jas-audio.or.jp/jas-cms/wp-content/uploads/ 2013/10 / 201309all. Pdf page 6, Figure 5, "Power spectrum distribution of Simulated program signal". Program
simulation noise has a relative high level lower than that of other bands. FIG. 7 is a diagram
showing an equalizer filter to which a weighting function is applied. As shown in FIG. 7, the high
region is lower than that of the equalizer filter shown in FIG.
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[0030]
Next, the DSP 8 calculates an effective value and calculates a correction value (S4). First, the DSP
8 calculates a first effective value which is the effective value of the frequency characteristic of
the equalizer filter to which the weighting function is applied. Specifically, the DSP 8 performs
the following calculation of Equation 1. That is, the DSP 8 takes the square root of the sum of the
values at each frequency of the product of the equalizer filter multiplied by the weighting
function, the equalizer filter multiplied by the weighting function and the conjugate complex
number. Here, F (ω) is the frequency characteristic of the equalizer filter. W (ω) is the frequency
characteristic of the weighting function. F'rms is a first effective value.
[0031]
Next, the DSP 8 calculates a second effective value which is an effective value of the frequency
characteristic of the weighting function. Specifically, the DSP 8 performs the following
calculation of Equation 2. That is, the DSP 8 takes the square root of the sum of the value at each
frequency of the product of the weighting function, the weighting function and the complex
complex number. Here, Wrms is a second effective value.
[0032]
Next, the DSP 8 calculates a third effective value, which is an effective value of the gain of the
equalizer filter, based on the first effective value and the second effective value. Specifically, the
DSP 8 performs the following calculation of Equation 3. That is, the DSP 8 divides the first
effective value by the second effective value. Here, Grms is a third effective value.
[0033]
Next, the DSP 8 calculates a correction value based on the threshold and the third effective value
when the third effective value is equal to or greater than a predetermined threshold. Specifically,
the DSP 8 performs the following calculation 4 That is, the DSP 8 divides the threshold by the
third effective value. Here, Vc is a correction value. Vt is a threshold. This threshold Vt is linked
to the system volume.
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[0034]
Next, the DSP 8 calculates a corrected equalizer filter obtained by correcting the equalizer filter
based on the correction value (S5). Specifically, the DSP 8 performs the following equation 5.
That is, the DSP 8 applies a correction value to the equalizer filter. Here, Fc (ω) is a correction
equalizer filter.
[0035]
The DSP 8 executes equalizer processing to change the frequency characteristic of the audio
signal (digital audio data) based on the correction equalizer filter.
[0036]
FIG. 8 is a diagram showing an example of the equalizer filter.
FIG. 9 is a diagram showing the effective value of the output voltage of the headphone terminal.
"Volume" indicates a step of system volume. "Headroom" indicates the headroom of the system
volume. “Threshold” indicates the above-described threshold. "None" is an effective value
when equalizer processing is not performed. “A” is an effective value when the equalizer
processing is performed. European sound pressure regulations require that the effective value be
less than 150 mV.
[0037]
If the volume step is 160, then the headroom is 0 dB and the threshold is 1. Further, the effective
value without equalizer processing is 130 mV, and the effective value with equalizer processing
is 92 mV. If the volume step is 140, then the headroom is 10 dB and the threshold is 3.1.
Further, the effective value without equalizer processing is 41 mV, and the effective value with
equalizer processing is 92 mV. If the volume step is 120, then the headroom is 20 dB and the
threshold is 5.6. The effective value without equalizer processing is 13 mV, and the effective
value with equalizer processing is 36 mV.
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[0038]
As described above, in the present embodiment, the DSP 8 changes the threshold according to
the volume. As a result, when the volume is small, the correction of the equalizer filter is not
performed, so that the correction processing can be performed according to the output level.
[0039]
Further, in the present embodiment, the DSP 8 applies the frequency characteristic of program
simulation noise to the equalizer filter as a weighting function, and calculates the correction
value using the equalizer filter to which the frequency characteristic of the program simulation
noise is applied. Then, the DSP 8 calculates a corrected equalizer filter obtained by correcting the
equalizer filter based on the correction value. As described above, since the equalizer filter is
corrected using the equalizer filter to which the frequency characteristic of the program
simulation noise is applied as the weighting function in consideration of the program simulation
noise, even if the program simulation noise is input, the corrected correction By the equalizer
filter, it is possible to output an audio signal below regulation.
[0040]
As mentioned above, although embodiment of this invention was described, the form which can
apply this invention is not restricted to the above-mentioned embodiment, As it illustrates below,
it is suitably in the range which does not deviate from the meaning of this invention. It is possible
to make changes.
[0041]
In the above embodiment, program simulation noise is used as the test signal.
Not only this but another signal may be sufficient.
[0042]
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In the above embodiment, the equalizer program is incorporated in the music reproduction
program P. Not limited to this, the music reproduction program for reproducing music files and
the equalizer program may be different programs.
[0043]
In the above embodiment, the case where the music reproduction program P is installed in DAP 1
has been described. Not limited to this, as a device to function as an equalizer device, a
smartphone, a tablet PC, a feature phone, a portable media player, a portable game machine, or
the like may be used.
[0044]
The present invention can be suitably adopted for an equalizer apparatus that performs equalizer
processing for changing the frequency characteristic of an audio signal, and an equalizer
program.
[0045]
1 DAP (equalizer device) 2 CPU (control unit) 6 display unit 7 operation unit 8 DSP (signal
processing unit) P music reproduction program (equalizer program)
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