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JPH05152982

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DESCRIPTION JPH05152982
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
transmission frequency characteristic correction apparatus, and more particularly to a
transmission frequency characteristic correction apparatus for obtaining a desired frequency
characteristic with a simple operation by a user.
[0002]
2. Description of the Related Art In recent years, in audio devices, transmission frequency
characteristic correction that applies predetermined frequency characteristic correction to
original sound in order to change the reproduced sound (original sound) from a CD device or
stereo device to the sound quality according to the user's preference. There is an increase in the
number of devices incorporated. In this type of conventional frequency characteristic correction
device, the range of frequency characteristics that can be corrected is limited, and for example,
there are many cases in which the sharpness and center frequency are fixed for each band.
[0003]
As described above, in the conventional transmission frequency characteristic correction
apparatus, the range of the frequency characteristic that can be corrected is limited, so that it is
not possible to obtain the frequency characteristic desired by the user. In addition, although
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there are cases in which the sharpness and center frequency can be varied, the parameters of the
center frequency, sharpness and gain (attenuation amount) must be given for each band, so the
correction characteristics of the frequency characteristic correction device are set. It is difficult if
the user is not skilled in the operation, and it is difficult to obtain the desired frequency
characteristics.
[0004]
Therefore, an object of the present invention is to provide a transmission frequency
characteristic correction device capable of setting a desired frequency correction characteristic
by a simple operation of a user.
[0005]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the
transmission frequency characteristic correction device according to the present invention can
arbitrarily set the center frequency, the sharpness, the gain or the amount of attenuation, and a
plurality of different bands. A variable filter unit having a filter, a target characteristic data
output unit to which target characteristic data is output, and a central frequency and a
bandwidth as inputs to estimate sharpness of the filter, and a plurality of filters of the variable
filter unit And a setting unit configured to set the synthetic filter characteristic by changing the
characteristic.
[0006]
In the present invention, the target characteristic data is input, and the center frequency,
sharpness, gain or attenuation of each filter of the variable filter unit comprising a plurality of
filters are arbitrarily set, and the above center frequency and band The sharpness of the filter is
estimated based on the width, and the synthesis filter characteristic is set to enable setting of a
desired frequency correction characteristic by a simple operation of the user.
[0007]
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram showing an
embodiment of a correction apparatus according to the present invention.
The input unit 1 includes, for example, a keyboard and a light pen, and is a device for the user to
input desired characteristic information. The microcomputer 2 having received the inputted
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characteristic information performs desired correction based on the characteristic information.
Characteristic parameters (data for setting the filter unit) are obtained by calculation.
The correction characteristic thus obtained is displayed on the display unit 5 and sent to the
variable filter unit 4 through the interface unit 3.
The variable filter unit 4 is a filter unit having a plurality of filters whose center frequency (f0),
filter sharpness (Q), and gain (attenuation amount) can be arbitrarily set, and parameters
transmitted through the interface unit 3 The filter characteristics are set at. The acoustic signal
interface unit 6 sends, for example, a reproduction signal (acoustic signal) from a CD or the like
to the variable filter unit 6, and outputs the acoustic signal subjected to the desired correction
processing by the variable filter unit 6 to an output amplifier or the like. Interface unit.
[0008]
Hereinafter, the processing procedure of the frequency correction processing in the
microcomputer 2 will be described in detail. When two user-desired frequency characteristics
input from the input unit 1 are supplied to the microcomputer as filter unit setting data
(hereinafter referred to as setting data), the microcomputer 2 performs a certain initializing
operation, and The filter setting calculation process described in detail below is started. As shown
in FIG. 2, first, determination of filter shape, estimation of sharpness and calculation of coefficient
are performed (step S1), calculation of setting band characteristics and calculation of synthesis
characteristics are performed (step S2), setting data and calculation An error of the synthesized
characteristic is obtained (step S3). Then, it is judged whether or not there is a band whose total
error is smaller than a predetermined (in this example, 5 [dB]) (step S4), and if it is, the setting of
that band is ended (step S5). If not, it is determined whether the setting has been completed for
all the bands (step 6). If all bands have been set in step 6, the process ends. If not ended, it is
determined whether or not the filter is set to n bands as shown in FIG. 3 (step S7). If not, as in
step S1, filter shape determination, sharpness estimation and coefficients are calculated (step S8).
In step S7, if n bands are set, the center frequency of the filter of the setting band is corrected as
described later (step S9), and coefficients are calculated based on the corrected center frequency
(step S10). After the processes of steps S8 and S10, calculation of set band characteristics and
calculation of combined characteristics are performed (step S11), and an error between the set
data and the calculated combined characteristics is determined in the same manner as step S3
(step S12). Then, as shown in FIG. 4, it is determined whether or not an n-band filter has already
been set (step S13). If so, the error of the entire band of the processed band is checked (step S14)
Then, it is determined whether the error before correction of the center frequency is smaller than
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the error after correction (step S15). Here, if it is not, the coefficient of the filter is stored in the
coefficient table (step S16), and if it is judged to be small, the coefficient before correction is
obtained from the coefficient table, and the frequency characteristic and the synthesis
characteristic of the set band are calculated. (Step S17) The setting of the processed band is
ended (step S18). If it is determined in step S13 that no setting is made, it is determined after the
processing in steps S16 and S18 whether there is a band in which the overall error is smaller
than 5 [dB] (step S19). Setting is completed (step S20), and if it is determined that there is no, the
process returns to the process of step S6 of FIG.
[0009]
The determination of the filter shape, the estimation of the sharpness and the coefficient
calculation in step S1 are performed according to the processing procedure shown in the
flowcharts of FIG. 5 and FIG. First, all input setting data is searched to obtain the maximum value
and the minimum value, and the condition that the absolute value of the maximum value is
smaller than the absolute value of the minimum value, and both the maximum value and the
minimum value are negative numbers It is determined whether or not one of the conditions is
satisfied (step S111). If not, the peaking filter is selected, the center frequency is set to the
frequency having the maximum value, and the gain is set to the maximum value of the setting
data (step S112). On the other hand, when any one of the conditions is satisfied, the notch filter
is selected, the center frequency is set to the frequency having the minimum value, and the
attenuation is set to the minimum value of the setting data (step S113). After the process of step
S112 or S113, the difference between the maximum value and the minimum value is obtained as
the gain difference (step S114), and it is determined whether the gain difference is smaller than 3
[dB] (step S115). If it is large, the bandwidth is determined as the absolute value of the difference
between the frequencies taking the minimum value of the input data from the frequency taking
the maximum value of the input data (step S116), and the center frequency and the bandwidth as
the input values are sharpness by fuzzy inference etc. Are set (step S118). Next, the coefficients
of the filter are calculated from the center frequency, the sharpness, and the gain (attenuation
amount) (step S119), the obtained coefficients are stored in the coefficient table (step S120), and
the process is ended. On the other hand, if it is determined in step S115 that the gain difference
is smaller than 3 [dB], the sharpness is set to a predetermined value (step S117), and the process
proceeds to the processing of step S119 and the subsequent steps in FIG.
[0010]
In step S2 of FIG. 2, the frequency characteristics of the first band are calculated using the
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coefficients calculated in this way, the combined characteristics of the n-band filter to be set are
calculated, and the combined characteristics calculated with the set data in step S3. Find the
error of The details of this process are shown in FIG. 7. In the set value and the synthesis
characteristic, the frequency range between the same three frequency points is one band, the
frequency range to be set is divided into a plurality of bands, and the error is set. The difference
in synthetic characteristics is taken from the data. First, it is determined whether all the
frequency ranges to be set have been completed (step S311), and if not completed, band division
is performed, and the error of the entire band, the maximum value of errors, and the minimum
value of errors are performed for each band. The frequency of the maximum value of the error
and the frequency of the minimum value of the error are obtained (step S312), and the process
returns to step S311. In step S311, when all are completed, the band with the largest error is
examined, and the maximum value, the minimum value, the frequency at the maximum value, the
maximum value of the error in the band with the largest error at the frequency at the minimum
value, The minimum value of the error, the frequency of the maximum value of the error, and the
frequency of the minimum value of the error are made to correspond (step S313), and the
process is ended.
[0011]
The correction of the center frequency in step S9 of FIG. 3 is performed according to the
procedure shown in the flowchart of FIG. That is, the error of the whole band and the center
frequency are stored for the band to be processed (step S911), and the subtraction result
obtained by subtracting the absolute value of (center frequency-frequency that becomes the
maximum error) from the absolute value of the maximum error The correction amount is
estimated by the fuzzy inference (step S912). Next, it is determined whether the maximum error
is positive or negative, and if it is negative, it is determined whether the subtraction result
obtained by subtracting the frequency that is the maximum error from the center frequency is
positive or negative (step S914). Here, if it is determined to be negative, the new center
frequency is made the value of the difference between the previous center frequency and the
correction amount (step S915), and if it is determined to be positive, the new center frequency is
corrected to the previous center frequency. It is set as the added value (step S916). On the other
hand, if it is determined in step S913 that the maximum error is positive, it is determined
whether the difference in frequency of the maximum value of errors from the center frequency is
positive or negative (step S917). The center frequency is set to a value obtained by adding the
correction amount to the previous center frequency (step S 918), and when it is determined to be
positive, the new center frequency is set to the difference value of the correction amount from
the previous center frequency (step S 919).
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[0012]
By the above processing, the coefficient of the filter having the frequency characteristic desired
by the user is obtained on the coefficient table, and the microcomputer 2 sends the data of the
coefficient table to the interface unit 3 of the filter unit. Set the filter unit according to. For
example, when setting data as shown in FIG. 9 is given, the entire setting data is first examined to
obtain the maximum value, the minimum value, the frequency at the maximum value, and the
frequency at the minimum value. In this example, the maximum value is 8 dB, the frequency at
the maximum value is 60 Hz, the minimum value is 2 dB, and the frequency at the minimum
value is 120 Hz. In the processing of the flowcharts of FIG. 5 and FIG. 6, the filter shape: peaking
filter, center frequency: 60 [Hz], gain: 8 [dB], and the gain difference = 8-2 = 6 [dB]. Bandwidth =
120 The filter sharpness is estimated by fuzzy inference using -60 = 60 Hz and a center
frequency of 60 Hz as input values. The estimation result is 1.08. The coefficients are calculated
from the center frequency 60 [Hz], the sharpness 1.08 and the gain 8 [dB], and stored in the
coefficient table. The calculated composite properties are shown in FIG.
[0013]
According to the process shown in the flowchart of FIG. 7, the error between the setting data and
the synthesis characteristic is obtained, and the frequency range of three points having the same
frequency in the setting value and the synthesis characteristic is set as one band. In the case of
the above example, the low band: 60, 120, 250 [Hz], the mid band: 500, 750, 1 k [Hz], and the
high band: 4 k, 8 k, 16 k [Hz]. As a result of the processing, since the high band is the one with
the largest error, the value of the high band error is set in the following settings. Therefore, the
maximum value is 7 [dB], the minimum value is 7 [dB], the frequency is 4 k [Hz] at the maximum
value, and the frequency is 4 k [Hz] at the minimum value. In the processing of FIG. 2 to FIG. 4,
the setting of all the bands is not completed, and the filter is also set to only one band, so the
flowchart processing of FIG. 5 and FIG. After the processing is completed, the set values have a
center frequency of 4 k [Hz], a sharpness of 0.25, a gain of 7 [dB], and the characteristics of the
set band are shown in FIG. Also, the synthesis characteristics are shown in FIG.
[0014]
Next, the process shown in FIG. 7 is executed again. As a result of the processing, since the
middle band is the largest in error, the value of the middle band is set in the following settings.
Therefore, the maximum value is 4 [dB], the minimum value is 0 [dB], the frequency is 250 [Hz]
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at the maximum value, and the frequency is 500 [Hz] at the minimum value. In FIG. 2 to FIG. 4,
since all bands have not been set yet and only two filters are set, the processing of FIG. 5 and FIG.
6 is executed again. After the processing is completed, the set values become the center
frequency 250 [Hz], the sharpness 1.18, and the gain 4 [dB]. The characteristics of the set band
are shown in FIG. Also, the synthesis characteristics are shown in FIG. By this setting, since the
error of the entire band is 5 [dB] or less in all the bands, the setting of all the bands is completed.
In this example, the coefficient data of the filter of three bands is obtained in the coefficient table
simultaneously with the completion of setting. The other remaining band filters remain initialized
to have a 0 dB characteristic. The subsequent operation of the microcomputer is as described
above.
[0015]
FIG. 15 is a block diagram showing another embodiment of the transmission frequency
characteristic correction apparatus according to the present invention. In the present
embodiment, an acoustic characteristic measurement device is used in place of the input unit 1 in
the embodiment of FIG. First, the microcomputer 2 sets the changeover switch 9 to the signal
generator 8 side, and sends an instruction of signal generation to the signal generator 8. From
the signal generator 8, reference signals such as impulse and white noise are reproduced from
the speakers 11L and 11R through the sound reproduction system. The reference signal
collected by the microphone MIC is frequency-analyzed by the acoustic characteristic
measurement device 7 and supplied to the microcomputer 2 as correction data. The
microcomputer 2 ends the measurement by receiving the correction data, and switches the
changeover switch 9 to the sound signal interface 6 side. Thereafter, a correction filter is formed
on the filter unit by the same process as described above. Hereinafter, after the frequency
characteristic of the acoustic signal is corrected by the filter unit 4, the acoustic signal is
amplified by the amplifier 10 and output in stereo from the speakers 11L and 11R. As described
above, according to the present embodiment, it is possible to automatically correct the indoor
frequency characteristic, and to limit the number of bands of the correction filter so that the filter
of the remaining bands is made the user desired frequency characteristic. it can.
[0016]
FIGS. 16 and 17 show an example of characteristics obtained by the conventional correction
device when each sharpness is calculated as 1.77 and an example of characteristics obtained by
the correction device according to the present invention. According to the device of the present
invention, compared to the filter center frequency and sharpness fixed correction device, there
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are no unnecessary peaks and dips for the user's setting, and it is possible to obtain
characteristics close to the characteristics desired by the user Can understand.
[0017]
As described above, according to the transmission frequency characteristic correction apparatus
of the present invention, the frequency characteristic desired by the user can be accurately set
with extremely simple operation, and the operability is remarkably improved. That is, according
to the present invention, it is not necessary for the user to set the center frequency, sharpness
and the like of the filter for each band, and the problem of the oscillation of the filter and the like
is eliminated by the user's operation.
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