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DESCRIPTION JP2009278175
An audio processing apparatus and an audio processing method capable of reproducing discrete
data with good sound quality according to user's preference. SOLUTION: In an acoustic
processing unit 3, discrete data is separated for each frequency band of a bass range, a mid
range and a high range, and a plurality of bands are generated for each frequency band via
amplifiers 5a, 5b and 5c. Inter-band interpolation units 6a, 6b, and 6c are provided for each
adjustment signal, and the inter-band adjustment signals are individually interpolated by the
inter-band interpolation units 6a, 6b, and 6c. This makes it possible to change the sampling
function used for interpolation processing for each frequency band, and by changing the
sampling function for each frequency band, the signal obtained by interpolation processing is
finely divided for each frequency band. Since the frequency characteristics of the analog signal
obtained by combining the signals obtained by the interpolation processing can be changed as
necessary, it is possible to reproduce high-quality music with user-desired sound quality. be able
to. [Selected figure] Figure 1
Sound processing apparatus and sound processing method
[0001]
The present invention relates to an acoustic processing apparatus and an acoustic processing
method, for example, interpolating between discrete data arranged in a time direction sampled at
a predetermined sampling frequency to generate discrete data at a frequency higher than the
sampling frequency at the time of input or an analog signal It is suitable to apply when
producing In the present specification, it will be described that generating a signal at discrete
intervals of high frequency and generating an analog signal are referred to as generation of an
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analog signal as the same processing. Further, the case where the value of the function has a
finite value other than 0 in the local area and becomes 0 in the other area will be referred to as
"finite base" to be described.
[0002]
Conventionally, when generating an analog signal from discrete data such as digital data, a
Shannon sampling function derived based on Shannon's sampling theorem has been widely used.
Here, as shown in FIG. 11, the sampling function of Shannon becomes 1 only at the sample
position of t = 0, becomes 0 at all other sample positions, and theoretically its oscillation from −
か ら to + ∞ Shows a waveform that continues indefinitely. For this reason, when actually
performing interpolation processing between discrete data using a sampling function of Shannon
by various processors etc., processing is forcibly terminated in a finite interval, and as a result, an
error due to truncation is There was a problem to occur.
[0003]
When such a Shannon sampling function is used, the analog signal to be reproduced is bandlimited, so discrete data recorded on, for example, a CD (Compact Disc) or a DVD (Digital
Versatile Disc) When the signal is converted into an analog signal and reproduced, an ultrasonic
wave of 22.05 kHz or more can not be reproduced, and there is a problem that a natural sound
generated by the difference sound of the ultrasonic wave can not be reproduced.
[0004]
Then, in order to solve such a problem, a sampling function which converges within a finite
range, which has no truncation error and can reproduce even higher order band components, has
been devised (for example, Patent Document) 1).
In this sampling function, since it converges to 0 at a sample position two points before and after
the origin, signal reproduction can be performed with a small amount of calculation, and it has
been confirmed that there is a band up to high frequencies. WO 99/38090
[0005]
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However, in an audio apparatus using such a sampling function, the high frequency band
component can be varied in accordance with various users such as the hearing impaired and the
elderly, and various conditions such as the music reproduction environment, the sound source
and the tune. In addition, the frequency characteristic can not be freely adjusted according to the
situation. On the other hand, in recent years, it has been desired to provide a tailor-made audio
apparatus in which the user himself can freely adjust the sound quality including the high
frequency band component according to the preference of each user, the type of music, and the
like.
[0006]
The present invention has been made in consideration of the above points, and it is an object of
the present invention to propose an acoustic processing apparatus and an acoustic processing
method capable of reproducing discrete data with good sound quality according to the
preference of the user.
[0007]
In order to solve such problems, an acoustic processing apparatus according to claim 1 of the
present invention comprises: band separation means for separating a plurality of discrete data
arranged in the time direction into a plurality of frequency bands to generate a plurality of bandspecific signals; Interpolation processing means for individually executing interpolation
processing for each band signal and generating an interpolation processing signal in which the
sampling frequency of the band signal is increased for each frequency band, and a plurality of
signals generated for each frequency band And band combining means for generating a
combined signal by combining the interpolation processed signals of
[0008]
The sound processing apparatus according to claim 2 of the present invention is characterized by
further comprising setting means for setting the method of the interpolation process for each of
the frequency bands.
[0009]
In the sound processing apparatus according to claim 3 of the present invention, the
interpolation processing means is finite-differentiable with a basic sampling function that is
finite-differentiable and has finite-order values. Each frequency band by a convolution operation
on the band-specific signal and a linear addition using a sampling function comprising a value
and a control sampling function indicating a waveform different from the waveform indicated by
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the basic sampling function. Function processing means for generating the interpolation
processing signal, the function processing means including coefficient multiplication means for
multiplying the control sampling function by a variable parameter which can be set to an
arbitrary value by the user. .
[0010]
Further, according to a fourth aspect of the present invention, there is provided a sound
processing apparatus according to the fourth aspect of the present invention, wherein a sound
pressure parameter is multiplied by one of the band-specific signal and the interpolation
processing signal to adjust sound pressure levels for each frequency band. Sound pressure
setting means for generating a band-by-band adjustment signal, wherein the interpolation
processing means individually executes the interpolation process for each of the band-by-band
adjustment signals when multiplying the sound pressure parameter by the band-by-band signal It
features.
[0011]
In the sound processing method according to claim 5 of the present invention, a band separation
step of dividing a plurality of discrete data arranged in the time direction into a plurality of
frequency bands to generate a plurality of band-specific signals, and each of the band-specific
signals Interpolation processing step of individually executing interpolation processing to
generate an interpolation processing signal in which the sampling frequency of the band-specific
signal is increased for each frequency band, and a plurality of the interpolation processing
generated for each frequency band And a band combining step of combining the signals to
generate a combined signal.
[0012]
In the sound processing method according to claim 6 of the present invention, a setting step of
setting a method of the interpolation processing for each of the frequency bands is provided
before the band separation step.
[0013]
In the sound processing method according to claim 7 of the present invention, the interpolation
processing step is a parameter setting step in which the variable parameter is set to an arbitrary
numerical value by the user, finite differentiation is possible, and a finite base value is included.
Sampling function comprising a basic sampling function that is different from the variable
parameter and is finite-differentiable and has a value in the finite range and a waveform that the
basic sampling function exhibits and a waveform that is different And a function processing step
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of generating the interpolation processing signal for each of the frequency bands by performing
a convolution operation on the band-specific signals and the linear addition.
[0014]
The sound processing method according to claim 8 of the present invention further includes a
sound pressure adjustment step after any one of the band separation step and the interpolation
process step, and the sound pressure adjustment step is performed after the band separation
step. The sound pressure parameter is multiplied by the band-specific signal in step (d), the
sound pressure parameter is multiplied by the sound pressure parameter after the interpolation
processing step, and the sound pressure level is calculated for each frequency band according to
the sound pressure parameter. A plurality of adjusted band-by-band adjustment signals are
generated, and the interpolation processing means individually executes the interpolation
processing for each of the band-by-band adjustment signals when multiplying the sound pressure
parameter by the band-by-band signals. I assume.
[0015]
According to the sound processing apparatus of claim 1 of the present invention and the sound
processing method of claim 5, the method of interpolation processing can be changed for each
frequency band, and the method of interpolation processing is performed for each frequency
band. By changing it, the interpolation processing signal can be finely adjusted for each
frequency band, and thus the frequency characteristic of the synthesized signal obtained by
performing the convolution operation of the interpolation processing signal can be changed as
needed. It is possible to reproduce high-quality music of desired sound quality.
[0016]
Hereinafter, embodiments of the present invention will be described in detail based on the
drawings.
[0017]
(1) Overall Configuration of Audio Device In FIG. 1, reference numeral 1 generally denotes an
audio device provided with an audio processing unit 3 according to the present invention, and
this audio device 1 uses an input unit 2 to record various kinds of audio such as CD and DVD.
The medium is reproduced, and a plurality of discrete data arranged in the time direction
obtained as a result are sequentially sent to the sound processing unit 3.
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By the way, discrete data is, for example, discrete data obtained by sampling a smoothly changing
continuous signal at fixed time intervals and quantizing sampling data obtained as a result.
[0018]
The sound processing unit 3 includes, for example, a band separation unit 4 that separates
discrete data into three frequency bands of bass, mid, and treble, and sound pressure for each of
the three frequency bands of bass, mid, and treble. A sound pressure adjustment unit 5 for
adjusting the level, an interpolation processing unit 6 for individually executing interpolation
processing for each frequency band using a predetermined sampling function (described later)
set for each frequency band, and a user An analog signal as a synthesized signal is generated by
combining the setting unit 7 which can arbitrarily set the sound pressure level and the sampling
function for each frequency band, and the interpolation processing signal generated for each
frequency band. And a band combining unit 8 for performing the process.
[0019]
In practice, as shown in FIG. 2, in the sound processing unit 3, the band separation unit 4 is
composed of a digital low pass filter 4a, a digital band pass filter 4b, and a digital high pass filter
4c. It is made to be able to be separated into the frequency band of the high range and the high
range respectively.
Incidentally, in the case of this embodiment, the digital low pass filter 4a, the digital band pass
filter 4b and the digital high pass filter 4c will be described in the case where they are configured
by an FIR (Finite Duration Impulse Response) filter. However, the present invention is not limited
to this, and may be configured by various other digital filters such as Infinite Impulse Response
(IIR) filters.
[0020]
The band separation unit 4 takes a predetermined number of discrete data by the digital low pass
filter 4a and performs averaging thereof to generate a band-specific signal consisting of a bass
frequency band from which the high range component is removed, It sends to pressure
regulation part 5 and digital band pass filter 4b.
[0021]
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The digital high-pass filter 4c is composed of the high frequency range frequency band obtained
by removing the set bass range component from the discrete data by adding / subtracting the
discrete data and newly input discrete data at the set weighting ratio. A band-specific signal is
generated and sent to the sound pressure adjustment unit 5 and the digital band pass filter 4b.
[0022]
The digital band pass filter 4b subtracts the low band component and the high band component
from the value of the discrete data by subtracting the values of the corresponding low band and
high band signals from the remaining mid band frequency band. Signal is generated and sent to
the sound pressure adjustment unit 5.
[0023]
The sound pressure adjustment unit 5 is provided with three amplifiers 5a, 5b and 5c
corresponding to the respective frequency bands of the low tone range, the middle tone range
and the high tone range, and the sound pressure level adjustment command from the setting unit
7 An amplification value for amplifying the sound pressure level of the band-specific signal may
be set for each amplifier 5a, 5b, 5c.
[0024]
Thereby, the sound pressure adjustment unit 5 multiplies the predetermined signal in the
amplifier 5a by the band-specific signal consisting of the frequency band of the bass band and
amplifies the signal, and the other amplifier 5b amplifies the signal by the band consisting of the
midband frequency band Only the signal may be amplified by multiplying the predetermined
amplification value, and then the other amplification signal may be multiplied by the other
amplification signal and amplified by the other amplifier 5c.
As a result, the sound pressure adjustment unit 5 amplifies the sound pressure level of only the
band-specific signal of the bass region by the user through the setting unit 7, for example, by a
user who is relatively hard to listen to the bass region frequency band. When set, a band-by-band
adjustment signal is generated in which the sound pressure level is amplified according to the
amplification value.
[0025]
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As described above, each of the amplifiers 5a, 5b, and 5c amplifies each band-specific signal to a
predetermined sound pressure level based on an amplification value as a predetermined sound
pressure parameter which is individually set in advance, and thus generated. Each band-by-band
adjustment signal is sent to the interpolation processing unit 6 respectively.
Here, the interpolation processing unit 6 is provided with three band-by-band interpolation units
6 a, 6 b, 6 c corresponding to the respective frequency bands of the bass range, the mid range
and the high range, and the interpolation process from the setting unit 7 A predetermined
sampling function that interpolates the band-by-band adjustment signals may be set for each of
the band-by-band interpolation units 6a, 6b, and 6c according to the selection instruction.
[0026]
Thereby, the band-by-band interpolation unit 6a executes the interpolation process only on the
band-by-band adjustment signal in the low-pitch band according to the sampling function preset
by the setting unit 7, and sets between the band-by-band data constituting the band-by-band
adjustment signal. The sampling frequency is artificially increased by interpolation, and the
interpolation processing signal obtained as a result is sent out to the band synthesis unit 8.
Also, at this time, the band-by-band interpolation unit 6b executes interpolation processing only
on the mid-band by-band adjustment signal according to a sampling function separately set by
the setting unit 7 from the other band-by-band interpolation units 6a and 6c. Interpolating
between the band-by-band data constituting the band-by-band adjustment signal to raise the
sampling frequency in a pseudo manner, and sending out the interpolation processing signal
obtained as a result to the band synthesizing unit 8.
Further, at this time, the band-by-band interpolation unit 6c performs interpolation processing
only on the high-frequency band-by-band adjustment signal according to a sampling function
separately set by the setting unit 7 separately from the other band-by-band interpolation units 6a
and 6b. And interpolates between the band-by-band data constituting the band-by-band
adjustment signal to raise the sampling frequency in a pseudo manner, and sends out the
interpolation processing signal obtained as a result to the band synthesizing unit 8.
[0027]
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The band combining unit 8 combines the plurality of interpolation processing signals generated
in the band-by-band interpolation units 6a, 6b, and 6c to generate one analog signal including all
frequency bands, and sends this to the output unit 9. Do.
As described above, the sound processing unit 3 can freely set different sampling functions for
each frequency band by configuring the interpolation processing unit 6 to individually execute
interpolation processing for each frequency band. It will be.
Thus, the sound processing unit 3 adjusts the interpolation value for interpolating between bandby-band data for each band-by-band adjustment signal by appropriately changing the sampling
function, and as a result, the interpolation process adjusted for each frequency band A signal can
be generated, and music composed of the user-desired sound quality whose frequency
characteristic of the analog signal is finely adjusted can be reproduced from the output unit 9.
[0028]
(2) Interpolation Process in Band-Specific Interpolation Unit Next, an outline of the interpolation
processing executed by each of the band-wise interpolation units 6a, 6b, 6c will be described
below.
The sampling function sN (t) used in the band-by-band interpolation units 6a, 6b, 6c is composed
of a basic sampling function f (t) and a control sampling function c0 (t).
Here, let t be a sample position of discrete data, and a sampling function consisting of, for
example, a basic sampling function f (t) between sample positions [−2, 2] of the discrete data
and a control sampling function c 0 (t) s2 (t) is the following equation,
[0029]
[0030]
If the general control sampling function is represented by ck (t), and ck (t) = cr (t−k) + cr
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(−t−k), the sample position of the discrete data [− The sampling function sN (t) is
[0031]
[0032]
Represented by
Here, α k indicates a variable parameter described later, and indicates an arbitrary numerical
value that can be set by the user, and may be the same value that does not change according to k,
such as α 1 = α 2 = α 3.
Incidentally, the sampling function s2 (t) when N = 2 will be described below simply as the
sampling function sN (t) for convenience of explanation.
Since this sampling function sN (t) can calculate an interpolation value reflecting the numerical
value of the variable parameter α, it is possible to adjust the interpolation processing signal for
each frequency band by changing the numerical value of the variable parameter α. It is done.
The basic sampling function f (t) and the control sampling function c0 (t) show waveforms as
shown in FIG. 3, and the amplitude of the waveform indicated by the control sampling function
c0 (t) according to the numerical value of the variable parameter α. May be variable.
[0033]
The basic sampling function f (t) is a finite-order function focusing on differentiability, and is, for
example, differentiable only once in the whole area, and the sample position t along the
horizontal axis is −1 to +1 (ie, , A section [−1, 1]) which has a finite value other than 0, and the
other sections are functions represented by 0 as an identity.
Specifically, the basic sampling function f (t) is a quadratic function of a representative functional
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form and shows a waveform of a convex shape that can be differentiated once in the entire
range, and is 1 only at a sample position of t = 0 And converges to 0 toward t = ± 1, and remains
at 0 until the sample position of t = ± 2.
[0034]
Further, the basic sampling function f (t) may be an n-th impulse response function in a finite
order, and it may be an n-th piecewise polynomial function continuous at points obtained by
dividing sample points.
Specifically, such a basic sampling function f (t) is given by the following equation in the case of a
second-order piecewise polynomial function:
[0035]
[0036]
Represented by
Then, the basic sampling function f (t) is used to perform superposition based on each bandspecific data that configures the band-specific adjustment signal, thereby differentiating the value
between the band-wise data of the band-specific adjustment signal only once. It is possible to
provisionally interpolate using possible functions.
[0037]
On the other hand, the control sampling function c0 (t) is a function of a finite base that focuses
on the differentiability, for example, it is differentiable only once in the whole area, and the
sample position t along the horizontal axis is −2 to +2 (Ie, it is a function having a finite value
other than 0 when it is in the interval [−2, 2]), and being represented by 0 in other intervals as
an identity.
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The control sampling function c0 (t) has a characteristic that it indicates a waveform that can be
differentiated only once in the entire range, and becomes 0 at each sample position of t = 0, ± 1,
± 2.
[0038]
Further, the control sampling function c0 (t) may be an n-order impulse response function in a
finite range, and may be an n-order piecewise polynomial function continuous at points obtained
by dividing sample points.
Here, the control sampling function c0 (t) is represented by the control sampling function c0 (t) =
cr (t) + cr (−t) as described above, and this cr (t) is specifically expressed by the following
equation ,
[0039]
[0040]
Represented by
Then, by superimposing the control sampling function c0 (t) based on each band data of the band
adjustment signal, the value between the band data of the band adjustment signal can be
differentiated only once. Temporary interpolation can be performed using a function.
[0041]
The sampling function sN (t) is represented by a linear combination of the basic sampling
function f (t) and the control sampling function c0 (t), and the actual interpolation operation is
performed using the basic sampling function f (t) and discrete data Calculated by the convolution
operation of the temporary sampling value (hereinafter referred to as a basic interpolation value)
calculated by the convolution operation with (sample value), the control sampling function c0 (t)
and the discrete data (sample value) By linearly adding a temporary interpolation value
(hereinafter referred to as a control interpolation value), it is possible to interpolate a value
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between band-by-band data of the band-by-band adjustment signal using a function that can be
differentiated only once. .
[0042]
Incidentally, the linear combination of the basic sampling function f (t) and the control sampling
function c0 (t) is characterized in that the following six conditions are satisfied.
First, S2 (0) = 1 and S2 (± 1) = S2 (± 2) = 0.
Second, even functions, that is, symmetry about the y-axis. Third, the sample position interval
[−∞, −2] and [2,]] are identically 0. Fourth, it is at most a quadratic polynomial in each section
[n / 2, (n + 1) / 2] (-4 ≦ n ≦ 3). Fifth, C1 class in all sections, that is, continuous one-time
differentiable. Sixth, in the sample position interval [-1/2, 1/2],
[0043]
[0044]
となること。
[0045]
In addition to this, at this time, the control sampling function c0 (t) can be multiplied by the
variable parameter α, which has been set by the user to any numerical value.
As a result, the control sampling function c0 (t) is kept at 0 at the sample position of t = 0, ± 1,
± 2, and is changed according to the numerical value of the variable parameter α between
sample position −2 and +2. The amplitude of the waveform may be distorted.
As a result, the control sampling function c0 (t) can change the calculation result by the
convolution operation with the discrete data (sample value). As described above, the variable
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parameter α can change the frequency characteristic of the interpolation processing signal
calculated by the sampling function sN (t) by changing the numerical value, and the signal of the
high frequency component for each frequency band It is made to be able to adjust the level.
[0046]
Therefore, in the present invention, the interpolation processing signal is adjusted by changing
the variable parameter α by which the control sampling function c0 (t) is multiplied for each
frequency band, and a plurality of these generated for each frequency band are generated. By
combining the interpolation processing signals to generate an analog signal, it is possible to
generate an analog signal having a user-desired sound quality whose high range is finely
adjusted for each frequency band.
[0047]
(3) Circuit Configuration of Band-Specific Interpolation Unit (3-1) Schematic Description of
Interpolation Processing in Band-Specific Interpolation Unit The three band-specific interpolation
units 6a, 6b, and 6c use sampling functions sN (t) used for interpolation processing. Although
different in that the variable parameter α is set individually and the difference in the band-byband adjustment signal to be subjected to the interpolation processing, the other points have the
same configuration, and hence the adjustment according to the band of the bass region
Description will be given focusing on the band-by-band interpolation unit 6a that interpolates
signals.
[0048]
As shown in FIG. 4, the band-by-band interpolation unit 6a sequentially extracts and holds a
predetermined number (four in this case) of band-by-band data constituting the band-by-band
adjustment signal, and a data extraction unit 15 The function processing unit 14 receives a
predetermined number of band data extracted and held at one time and executes interpolation
processing using these band data, and determines between band data sequentially input from the
amplifier 5a. It is designed to be able to interpolate data at time intervals of
[0049]
The function processing unit 14 processes the convolutional data with the term of the basic
sampling function f (t) in the sampling function sN (t) based on the data by band, and the data by
band. Based on the control function operation unit 17 which processes convolution operation
with the term of the control sampling function c0 (t) among the sampling function sN (t), the
calculation result of the control term operation unit 17 is multiplied by the variable parameter
α. A coefficient multiplication unit 18 and an addition operation unit 19 that linearly adds the
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calculation result of the basic term calculation unit 16 and the calculation result of the coefficient
multiplication unit 18 are included.
[0050]
In the case of this embodiment, the data extraction unit 15 extracts the immediately preceding
four band-specific data from the sequentially input band-specific data, and these four bands until
a new band-specific data is next input. The separate data is held, and these four band-based data
are sent to the basic term operation unit 16 and the control term operation unit 17, respectively.
[0051]
The basic term operation unit 16 stores the basic sampling function f (t) in a predetermined
storage means (not shown), and when the interpolation position between band-specific data is
designated, the interpolation position and the band-specific data are designated. Calculate the
value of the basic sampling function f (t) based on the distance to the data.
The basic term calculation unit 16 can calculate the value of the basic sampling function f (t) for
each of the four band-specific data sent from the data extraction unit 15.
Also, the basic term operation unit 16 multiplies the values of the band-wise data respectively
corresponding to the values of the four basic sampling functions f (t) obtained for each band-wise
data, and then these four band-wise data The convolution operation corresponding to is
performed, and the calculation result of this convolution operation is sent to the addition
operation unit 19.
[0052]
At the same time, the control term operation unit 17 stores the control sampling function c0 (t)
in a predetermined storage means (not shown), and when the interpolation position is
designated, the interpolation position and data by band are Calculate the value of the control
sampling function c 0 (t) based on the distance between
The control term operation unit 17 can calculate the value of the control sampling function c 0
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(t) for each of the four band-based data sent from the data extraction unit 15.
In addition, the control term operation unit 17 multiplies the values of the corresponding band
data for each of the values of the four control sampling functions c0 (t) obtained for each of the
band data, and adds these values. A convolution operation corresponding to the four band-based
data is performed, and the calculation result of the convolution operation is sent to the
coefficient multiplication unit 18.
[0053]
The coefficient multiplication unit 18 multiplies the variable parameter α by the calculation
result of the convolution operation of the control sampling function c 0 (t) received from the
control term operation unit 17, and adds the variable parameter multiplication result obtained as
a result to the addition operation unit 19. Send to
The addition operation unit 19 linearly adds the calculation result of the convolution operation of
the basic sampling function f (t) received from the basic term operation unit 16 and the variable
parameter multiplication result received from the coefficient multiplication unit 18. An operation
result corresponding to one of the band-by-band data is obtained. The value obtained by this
linear addition is an interpolation value at an interpolation position between predetermined two
band-wise data. Incidentally, this interpolation position is updated at a predetermined time
interval set in advance, more specifically, every 1 / N period (= T / N) of the period T
corresponding to the input interval of the band-specific data. Ru.
[0054]
(3-2) Specific Example of Obtaining Interpolation Value Based on Four Band-Specific Data Next,
an interpolation value between predetermined two band-specific data is calculated based on four
band-specific data arranged in line in time. The interpolation processing to be performed will be
described below with reference to FIG. 5 which shows the positional relationship between four
continuous band-based data and a target point which is an interpolation position. In FIG. 5, the
values of the band-by-band data d1, d2, d3 and d4 sequentially input corresponding to the
sample positions t1, t2, t3 and t4 are Y (t1), Y (t2) and Y (t). Let t3) and Y (t4), and consider a
case where an interpolation value y corresponding to a predetermined position between sample
positions t2 and t3 (that is, interpolation position (t2 to distance b)) t0 is obtained.
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[0055]
Since the sampling function sN (t) used in the present embodiment converges to 0 at a sample
position of t = ± 2, if band data d1, d2, d3, d4 up to t = ± 2 are taken into consideration Good.
Therefore, in order to obtain the interpolation value y shown in FIG. 5, only the four bandspecific data d1, d2, d3 and d4 corresponding to t = t1, t2, t3 and t4 need to be considered. The
amount can be reduced significantly. Moreover, each band-wise data (not shown) of t = ± 3 or
more should be taken into consideration, but it is not necessarily ignored in consideration of the
amount of computation, accuracy, etc., and is theoretically considered No truncation error occurs
because it is not necessary.
[0056]
As shown in FIG. 6, the data extraction unit 15 includes three shift circuits 20a, 20b, and 20c,
and when successive band-based data are input, the corresponding band is provided for each of
the shift circuits 20a, 20b, and 20c. The separate data can be shifted, for example, at a sampling
period (44.1 kHz) of CD, and each shift circuit 20a, 20b, 20c can extract and hold one of the
immediately preceding separate data d1, d2, d3, d4. That is, when the continuous four bandspecific data d1, d2, d3 and d4 are input, the data extraction unit 15 directly inputs the latest
band-specific data d4 as the basic term calculation circuit 21a of the basic term operation unit
16 and the control term. They are sent to the control term calculation circuit 22a of the
arithmetic unit 17.
[0057]
Further, the data extraction unit 15 sends out a band-wise data train consisting of four
continuous band-wise data d1, d2, d3 and d4 to the shift circuit 20a, shifts the band-wise data
train by the shift circuit 20b, The band-by-band data d3 of the immediately preceding band is
extracted from the band-by-band data d4 and sent to the basic term calculation circuit 21b of the
basic term calculation unit 16 and the control term calculation circuit 22b of the control term
calculation unit 17.
[0058]
Furthermore, the data extraction unit 15 sequentially sends out the band-wise data trains to the
remaining shift circuits 20b and 20c, and further shifts the band-wise data trains in the shift
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circuit 20b to obtain two latest band-wise data d4. The previous banded data d2 is sent to the
fundamental term calculating circuit 21c and the control term calculating circuit 22c, and the
banded data train is further shifted by the shift circuit 20c to divide by three bands from the
latest banded data d4. The data d1 is sent to the basic term calculation circuit 21d and the
control term calculation circuit 22d.
[0059]
Here, FIGS. 7 and 8 are diagrams showing an outline of interpolation processing for the
predetermined interpolation position t0 in the basic term operation unit 16 and the control term
operation unit 17 according to the present embodiment.
As the contents of the interpolation processing, as described above, firstly, calculation processing
for calculating the basic interpolation value in the basic term calculation unit 16 (hereinafter, this
is simply referred to as basic interpolation value calculation processing); And arithmetic
processing (hereinafter, this is simply referred to as control interpolation value calculation
processing) for calculating a control interpolation value in the coefficient multiplication unit 18 is
executed.
The basic interpolation value calculation process and the control interpolation value calculation
process will be described below with reference to FIGS. 7 and 8.
[0060]
(3-2-1) Basic Interpolation Value Calculation Process As the contents of the basic interpolation
value calculation process, as shown in FIGS. 7A to 7D, the basic interpolation value calculation
process is performed for each sample position t1, t2, t3, and t4. The peak heights at t = 0 (center
position) of the sampling function f (t) are made to coincide, and the value of each basic sampling
function f (t) at the interpolation position t0 at this time is obtained.
[0061]
Focusing on the band-specific data d1 at the sample position t1 shown in FIG. 7A, the distance
between the interpolation position t0 and the sample position t1 is 1 + b.
08-05-2019
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Accordingly, the value of the basic sampling function at the interpolation position t0 when the
center position of the basic sampling function f (t) is aligned with the sample position t1 is f (1 +
b). Actually, in order to match the peak height of the central position of the basic sampling
function f (t) so as to coincide with the value Y (t1) of the band-wise data d1, the above f (1 + b) is
multiplied by Y (t1) The value f (1 + b) · Y (t1) is the value to be obtained. The calculation of f (1 +
b) is performed by the basic term calculation circuit 21a of the basic term calculation unit 16,
and the calculation of multiplying f (1 + b) by Y (t1) is performed by the basic term multiplication
circuit 23a of the basic term calculation section 16. (Figure 6).
[0062]
Similarly, focusing on the value Y (t2) of the band-specific data d2 at the sample position t2
shown in FIG. 7B, the distance between the interpolation position t0 and the sample position t2 is
b. Accordingly, the value of the basic sampling function at the interpolation position t0 when the
center position of the basic sampling function f (t) is aligned with the sample position t2 is f (b).
In practice, in order to match the peak height at the center position of the basic sampling
function f (t) so as to match the value Y (t2) of the band-wise data d2, the above f (b) is multiplied
by Y (t2) The value f (b) · Y (t2) is the value to be obtained. The calculation of f (b) is performed
by the basic term calculation circuit 21b of the basic term calculation unit 16, and the calculation
of multiplying f (b) by Y (t2) is performed by the basic term multiplication circuit 23b of the
basic term calculation section 16. (Figure 6).
[0063]
Focusing on the value Y (t3) of the band-specific data d3 at the sample position t3 shown in FIG.
7C, the distance between the interpolation position t0 and the sample position t3 is 1-b.
Accordingly, the value of the basic sampling function at the interpolation position t0 when the
center position of the basic sampling function f (t) is aligned with the sample position t3 is f (1-b).
Actually, in order to match the peak height of the central position of the basic sampling function
f (t) so as to match the value Y (t3) of the band-based data, f (1-b) described above is set to Y (t3)
The multiplied value f (1-b) · Y (t3) is the value to be obtained. The calculation of f (1-b) is
performed by the basic term calculation circuit 21c of the basic term operation unit 16, and the
calculation of multiplying f (1-b) by Y (t3) is the basic term multiplication circuit of the basic term
operation unit 16. It takes place at 23c (Figure 6).
08-05-2019
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[0064]
Focusing on the value Y (t4) of the band-specific data d4 at the sample position t4 shown in FIG.
7D, the distance between the interpolation position t0 and the sample position t4 is 2-b.
Therefore, the value of the basic sampling function at the interpolation position t0 when the
center position of the basic sampling function f (t) is aligned with the sample position t4 is f (2-b).
In practice, in order to match the peak height at the center position of the basic sampling
function f (2-b) so as to match the value Y (t4) of the band-wise data d4, the above f (2-b) (T4)
The multiplied value f (2-b) · Y (t4) is the value to be obtained. The calculation of f (2-b) is
performed by the basic term calculation circuit 21d of the basic term operation unit 16, and the
calculation of multiplying f (2-b) by Y (t4) is the basic term multiplication circuit of the basic term
operation unit 16. 23d (FIG. 6).
[0065]
Then, the basic term calculation unit 16 calculates four values f (1 + b) · Y (t1), f (b) · Y (t2), f
(1−b) obtained corresponding to the target point at the interpolation position t0. ) · Y (t3), f (2-b)
· Y (t4) are convoluted in the basic term convolution circuit 24, and the basic interpolation value
ya is calculated in the frequency band of the bass range. Incidentally, in the case of this
embodiment, values f (1 + b) · Y (t1) and f (2-b) · Y (t4) obtained corresponding to the target point
at the interpolation position t0 are shown in FIG. And 0), the basic interpolation value ya is {f (b) ·
Y (t2)} + {f (1−b) · Y (t3)}.
[0066]
(3-2-2) Control Interpolation Value Calculation Processing On the other hand, as the contents of
control interpolation value calculation processing, as shown in FIGS. 8A to 8D, for each sample
position t1, t2, t3, and t4. , Let t = 0 (center position) of the control sampling function c0 (t)
coincide, and the values Y (t1) of the band-wise data d1, d2, d3, d4 corresponding to each control
sampling function c0 (t) , Y (t2), Y (t3), Y (t4), and the value of each control sampling function c0
(t) at the interpolation position t0 at this time is obtained.
[0067]
Focusing on the value Y (t1) of the band-specific data d1 at the sample position t1 shown in FIG.
8A, the distance between the interpolation position t0 and the sample position t1 is 1 + b.
08-05-2019
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Therefore, the value of the control sampling function at the interpolation position t0 when the
center position of the control sampling function c0 (t) is aligned with the sample position t1 is c0
(1 + b). Actually, in order to match the waveform height of the control sampling function c0 (t) in
correspondence with the value Y (t1) of the band-by-band data d1, the value c0 (c) is obtained by
multiplying c0 (1 + b) by Y (t1). 1 + b) · Y (t1) is a value to be obtained. The calculation of c0 (1 +
b) is performed by the control term calculation circuit 22a of the control term calculation unit
17, and the calculation of multiplying c0 (1 + b) by Y (t1) is performed by the control term
multiplication circuit 25a of the control term calculation unit 17. (Figure 6).
[0068]
Similarly, focusing on the value Y (t2) of the band-specific data d2 at the sample position t2
shown in FIG. 8B, the distance between the interpolation position t0 and the sample position t2 is
b. Therefore, the value of the control sampling function at the interpolation position t0 when the
center position of the control sampling function c0 (t) is aligned with the sample position t2 is c0
(b). Actually, in order to match the waveform height of the control sampling function c0 (t) in
correspondence with the value Y (t2) of the band-wise data d2, a value c0 (c) obtained by
multiplying c0 (b) described above by Y (t2) b) Y (t2) is the value to be obtained. The calculation
of c0 (b) is performed by the control term calculation circuit 22b of the control term operation
unit 17, and the calculation of multiplying c0 (b) by Y (t2) is performed by the control term
multiplication circuit 25b of the control term operation unit 17. (Figure 6).
[0069]
Focusing on the value Y (t3) of the band-specific data d3 at the sample position t3 shown in FIG.
8C, the distance between the interpolation position t0 and the sample position t3 is 1-b.
Therefore, the value of the control sampling function at the interpolation position t0 when the
center position of the control sampling function c0 (t) is aligned with the sample position t3 is c0
(1-b). Actually, in order to match the waveform height of the control sampling function c0 (t) in
correspondence with the value Y (t3) of the band-wise data d3, a value obtained by multiplying
c0 (1-b) described above by Y (t3) c0 (1-b) · Y (t3) is a value to be obtained. The calculation of c0
(1-b) is performed by the control term calculation circuit 22c of the control term calculation unit
17, and the calculation of multiplying c0 (1-b) by Y (t3) is the control term multiplication circuit
of the control term calculation unit 17 It takes place at 25c (Figure 6).
08-05-2019
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[0070]
Focusing on the value Y (t4) of the band-specific data d4 at the sample position t4 shown in FIG.
8D, the distance between the interpolation position t0 and the sample position t4 is 2-b.
Accordingly, when the center position of the control sampling function c0 (t) is aligned with the
sample position t4, the value of the control sampling function at the interpolation position t0 is
c0 (2-b). In practice, c0 (2-b) described above is multiplied by Y (t4) to match the waveform
height of the control sampling function c0 (2-b) in correspondence with the value Y (t4) of the
band-wise data d4. The calculated value c0 (2-b) · Y (t4) is the value to be obtained. The
calculation of c0 (2-b) is performed by the control term calculation circuit 22d of the control
term calculation unit 17, and the calculation of multiplying c0 (2-b) by Y (t4) is the control term
multiplication circuit of the control term calculation unit 17 It takes place at 25d (Figure 6).
[0071]
Then, four values c0 (1 + b) · Y (t1), c0 (b) · Y (t2), c0 (1-b) · Y (t3), obtained corresponding to the
target point at the interpolation position t0 After c 0 (2-b) · Y (t 4) is convoluted by the control
term convolution circuit 26 of the control term operation unit 17, the coefficient multiplication
unit 18 multiplies it by the variable parameter α, whereby the frequency band of the bass range
The control interpolation value yb at is calculated.
[0072]
(3-2-3) Interpolation value calculation processing The addition calculation unit 19 is calculated
by the basic interpolation value ya corresponding to the point of interest calculated by the basic
term calculation unit 16, the control item calculation unit 17 and the coefficient multiplication
unit 18. By linearly adding the control interpolation value yb corresponding to the target point, it
is possible to output the interpolation value y of the interpolation position t0 in the frequency
band of the bass range.
In this manner, the interpolation values are similarly calculated for all other interpolation
positions between band-specific data d2 and d3, and the band-by-band interpolation units 6b and
6c are also performed for each frequency band of mid-range and high-range. Similar
interpolation techniques may be performed using the set sampling function.
08-05-2019
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[0073]
(3-3) Interpolation processing result when changing the numerical value of the variable
parameter In addition to the above configuration, the sound processing unit 3 causes the setting
unit 7 to set the numerical value of the variable parameter α of the coefficient multiplication
unit 18 to each band-by-band interpolation unit 6 , 6b, and 6c, the value of the sampling function
sN (t) is changed for each of the band-by-band interpolation units 6a, 6b, and 6c, and the
interpolation value y can be adjusted for each of the frequency bands. . As a result, the frequency
characteristics of the analog signal generated in the band synthesis unit 8 can be adjusted by
changing the numerical value of the variable parameter α for each frequency band. Here, with
respect to how the sampling function sN (t) changes when the variable parameter α is changed,
the waveform indicated by the basic sampling function f (t) shown in FIG. 3 and the control
sampling function The following description will be given focusing on a waveform obtained by
combining the waveform indicated by c0 (t).
[0074]
The waveform of a sampling function sN (t) obtained by combining the waveform indicated by
the basic sampling function f (t) and the waveform indicated by the control sampling function c0
(t) is, as shown in FIG. It differs greatly depending on the numerical value. In the case of this
embodiment, when the variable parameter α is sequentially changed to −1.5, −0.25, 1.5, a
region of −2 ≦ t ≦ −1 and a region of 1 ≦ t ≦ 2 It was confirmed that the amplitude of the
wavelength of the sampling function sN (t) gradually increased and the polarity of the waveform
was inverted. On the other hand, it was confirmed that the amplitude of the wavelength of the
sampling function sN (t) gradually decreased in the region of −1 ≦ t ≦ 0 and the region of 0 ≦
t ≦ 1, and the waveform polarity was inverted.
[0075]
By the way, the discrete data obtained by playing the violin song "Zigeunerweisen" recorded on
CD as a test song for 23 seconds is not separated into the low frequency range, the mid range
and the high frequency range. Interpolation processing as it is. At this time, the variable
parameter α is set to −0.25, −1.5 and 1.5, respectively, and the frequency characteristics of
the analog signal interpolated with each sampling function sN (t) are compared. The results
shown are obtained.
08-05-2019
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[0076]
As shown in FIG. 10, in the interpolation processing by each sampling function sN (t) in which
the numerical value of the variable parameter α is changed, even if the numerical value of the
variable parameter α is changed, the signal in the high range of 20 kHz or more The level was
increased, and it was confirmed that the high range component can be reproduced as compared
with the case where the conventional Shannon sampling function is used. A waveform having
such a characteristic is formed similarly even when interpolation processing is performed on
band-wise data generated by separating discrete data in the low band, mid band and high band
frequency bands, The treble band component in the range can be reproduced for each range of
each frequency band of the bass range, the middle range and the treble range as compared with
the case of using the sampling function of Shannon.
[0077]
Also, when the variable parameter α was set to 1.5, -1.5 or -0.25, the waveforms of each signal
level were different from each other. Then, a waveform having such characteristics is formed
similarly even when interpolation processing is performed on band-wise data generated by
separating discrete data into frequency bands of bass, mid and treble bands. By adjusting the
value of variable parameter α for each frequency band of bass, midrange and treblerange as
appropriate, the signal level is individually adjusted within the range of each frequency band of
bass, midrange and treblerange. can do.
[0078]
As described above, the sound processing unit 3 can adjust the signal level finely for each
frequency band by changing the variable parameter α of the sampling function sN (t) for each
frequency band. More detailed adjustments can be easily made to the user. Thus, in the present
invention, the interpolation processing signals are individually adjusted by changing the variable
parameter α for each frequency band, and the plurality of adjusted interpolation processing
signals are synthesized to generate an analog signal. The high frequency range can generate an
analog signal finely adjusted for each frequency band.
[0079]
08-05-2019
24
(4) Operation and Effect In the above configuration, the sound processing unit 3 separates
discrete data for each frequency band of bass, mid and treble, and generates a plurality of
adjustment signals according to band generated for each frequency band. The inter-band
interpolation units 6a, 6b, and 6c are provided for each band, and the inter-band adjustment
signals are individually interpolated by the inter-band interpolation units 6a, 6b, and 6c. Thereby,
the sound processing unit 3 can change the sampling function used for the interpolation process
for each frequency band, and the interpolation process obtained by performing the interpolation
process by changing the sampling function for each frequency band The signal can be finely
adjusted for each frequency band, and thus by combining a plurality of interpolation processing
signals obtained by the interpolation processing, the frequency characteristics of the analog
signal can be finely changed as needed, and the user-desired sound quality It can play highquality music consisting of
[0080]
As described above, the sound processing unit 3 generates the interpolation processing signal in
which the interpolation value is finely adjusted for each frequency band, and generates the
analog signal by combining the plurality of interpolation processing signals. High-quality music
consisting of user-desired sound quality in which the frequency characteristics of the analog
signal are adjusted by the user appropriately changing the sampling function for each frequency
band according to various conditions such as music playback environment, sound source, tune
and the like Can be played.
[0081]
In particular, in the present invention, the variable parameter α of the sampling function sN (t) is
individually changed for each frequency band and interpolation processing can be performed, so
that fine adjustment of the interpolation value can be performed for each frequency band. As a
result, the frequency characteristics of the analog signal can be finely adjusted by that amount.
That is, discrete data consisting of all frequency bands without being separated into low
frequency range, middle frequency range, and high frequency range is simply processed as it is
by changing variable parameter α of sampling function sN (t) As compared with the case of
adjusting the characteristics, in the present invention, the fine adjustment of the interpolation
value can be performed for each frequency band, so that the frequency characteristics of the
analog signal can be adjusted more finely. It can play music.
08-05-2019
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[0082]
Further, in the case of this embodiment, the basic sampling function f (t) is stored in the basic
term operation unit 16 and each of the band-wise data d1, d2, d3 and d4 extracted by the data
extraction unit 15 is stored. The value of the basic sampling function f (t) is calculated with the
distance to the interpolation position t0 as t and the value of the basic sampling function f (t)
corresponding to each of the band-wise data d1, d2, d3, d4. Is calculated to calculate the basic
interpolation value ya at the interpolation position t0.
[0083]
Further, separately from this, in the sound processing unit 3, the control sampling function c 0 (t)
is stored in the control term operation unit 17, and the band-wise data d 1, d 2, d 3, and so forth
extracted by the data extraction unit 15. The value of the control sampling function c0 (t) is
calculated with t being the distance at the interpolation position t0 for each d4, and the control
sampling function c0 (t) corresponding to each of the band-specific data d1, d2, d3, d4 The
control interpolation value yb at the interpolation position t0 is calculated by multiplying the
variable parameter α set to an arbitrary value by the user by the convolution operation result of
the control sampling function c0 (t) after performing the convolution operation of the value of It
was calculated.
[0084]
The sound processing unit 3 calculates the interpolation value y between the discrete data by
linearly adding the basic interpolation value ya and the control interpolation value yb calculated
in this manner, whereby control sampling is performed. It is possible to calculate an interpolation
value y reflecting the numerical value of the variable parameter α to be multiplied by the value
of the function c0 (t).
[0085]
Therefore, the sound processing unit 3 can easily adjust the interpolation value y obtained by the
interpolation processing with the sampling function sN (t) simply by changing the numerical
value of the variable parameter α, so that different sampling functions sN (t It is not necessary
to provide a plurality of circuit boards corresponding to each t), the configuration can be
simplified accordingly, and the cost can be reduced.
[0086]
Further, the sound processing unit 3 uses the basic sampling function f (t) and the control
08-05-2019
26
sampling function c0 (t) in the finite range which can be differentiated once in the whole area as
the sampling function sN (t), Since the transformation function c0 (t) is multiplied by the variable
parameter α, the amount of operation required for interpolation processing between discrete
data can be significantly reduced compared to the case where the conventional Shannon
sampling function is used, Further, no truncation error occurs when the Shannon sampling
function is used, and the occurrence of aliasing can be prevented.
[0087]
In the case of this embodiment, it is possible to cause the value of the waveform of the sampling
function sN (t) to converge to 0 particularly in a range narrower than or equal to two sample
positions before and after the interpolation position t0. Therefore, when performing data
interpolation and the like using this sampling function sN (t), it is sufficient to use a total of four
discrete data two on each of the front and back of the target position, and using Shannon's
sampling function It is possible to dramatically reduce the processing load compared to the case.
[0088]
Further, in the case of this embodiment, in the sampling function sN (t), the basic sampling
function f (t) and the control sampling function c0 (t) which varies with the numerical value of
the variable parameter α are separately stored. The convolution operation is individually
performed on discrete data, and the convolutional result of the control sampling function c 0 (t)
and the discrete data is multiplied by the variable parameter α, and this is multiplied by the
basic sampling function sN (t And the discrete data are linearly added to obtain an output signal,
so that one control sampling function c 0 (t) is sufficient, and the equation can be simplified as
much as possible. Variable control of the sampling function c0 (t) can be easily performed.
[0089]
Furthermore, in the sound processing unit 3, the amplifiers 5a, 5b and 5c are provided for each
frequency band, and the sound pressure level is individually amplified by each of the amplifiers
5a, 5b and 5c. It is possible to amplify only the sound pressure level in the frequency band which
is hard to hear, and thus to reproduce high-quality music composed of the sound quality desired
by the user.
[0090]
(5) Other Embodiments The present invention is not limited to the present embodiment, and
various modifications can be made within the scope of the present invention.
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For example, in the embodiment described above, the case has been described where
interpolation processing using a sampling function sN (t) is applied as interpolation processing,
but the present invention is not limited to this, and sampling functions may be used. Not only the
interpolation process used but also various other interpolation processes may be applied.
[0091]
Also, here, using the sampling function sN (t) consisting of the basic sampling function f (t) and
the control sampling function c0 (t), the variable parameter α to be multiplied by the control
sampling function c0 (t) Although the case where the interpolation processing signal is adjusted
by changing the numerical value of is described, the present invention is not limited to this, and
in addition to the sampling function sN (t), the sampling function of Shannon is selected.
Alternatively, the interpolation processing signal may be adjusted by simply selecting various
sampling functions set in advance.
[0092]
Also, for example, although the sampling function sN (t) is a finite function that can be
differentiated only once in the entire range, the number of differentiable times may be set to two
or more.
Furthermore, in the above-described embodiment, although the analog signal is generated as a
synthesized signal by performing interpolation processing using the sampling function sN (t), the
present invention is not limited to this. Alternatively, an interpolation process may be performed
using a sampling function sN (t) to generate a simply oversampled composite signal, and then an
analog-to-digital converter may generate an analog signal.
[0093]
Furthermore, in the above-described embodiment, the sampling function sN (t) is described as
being converged to 0 at t = ± 2, but the present invention is not limited to this, and t = ± 3 or
more. It may converge to 0.
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For example, in the case of converging to 0 at t = ± 3, the data extraction unit 15 extracts the
last six discrete data, and the function processing unit 14 performs sampling function sN on
these six discrete data. The value of (t) may be calculated.
[0094]
Furthermore, in the embodiment described above, the basic sampling function f (t) is stored in
the basic term operation unit 16, and the control sampling function c0 (t) is stored in the control
term operation unit 17 separately from this. In addition, the basic interpolation value ya and the
control interpolation value yb are calculated by performing a convolution operation on the bandwise data d1, d2, d3 and d4 for each of the basic sampling function f (t) and the control sampling
function c0 (t). After that, the basic interpolation value ya and the control interpolation value yb
are linearly added to calculate the interpolation value y. However, the present invention is not
limited to this, and the basic sampling function f (t) and The control sampling function c0 (t) is
linearly added in advance and stored as one sampling function sN (t), and using the sampling
function sN (t) in which the variable parameter α is changed, band-specific data d1, Perform a
convolution operation on d2, d3 and d4 to directly interpolate y It may be calculated.
[0095]
Furthermore, in the embodiment described above, the case has been described in which the
interpolation process is performed for each of the band-by-band adjustment signals obtained by
amplifying the sound pressure level, but the present invention is not limited to this. Even if the
interpolation processing unit directly receives the band-specific signals separated into the
predetermined frequency bands by the band separation unit without amplifying the sound
pressure level, the predetermined interpolation processing may be performed for each of the
band-specific signals. Good.
[0096]
Furthermore, in the embodiment described above, although the case where the interpolation
process is performed after amplifying the sound pressure level has been described, the present
invention is not limited to this, and the sound pressure level is not increased after the
interpolation process is performed. It may be made to amplify, and in this case, while performing
interpolation processing separately for every adjustment signal classified by zone, a sound
pressure parameter may be separately multiplied to the interpolation processing signal obtained
as a result.
[0097]
Furthermore, in the embodiment described above, the case has been described where the sound
08-05-2019
29
pressure level in the frequency band which the user can not easily listen to is amplified by
multiplying the amplification value as the sound pressure parameter, but the present invention is
limited thereto Alternatively, the sound pressure level in the frequency band easy for the user to
listen to may be attenuated by multiplying the attenuation value as the sound pressure
parameter, and even in this case, the other sound pressure level is not attenuated. Since the
frequency band can be emphasized, it is easy to listen to the frequency band that the user can
not normally listen to, and thus, the user can reproduce high-quality music.
[0098]
Furthermore, in the embodiment described above, the discrete data is separated into three
frequency bands of bass, mid and treble, but the present invention is not limited to this, and bass
and high are not limited to this. The discrete data may be separated into two of the sound range,
or the discrete data may be further divided into four or five plural frequency bands such as a
low-mid range between the low-tone range and the mid-range more finely. In this case, amplifiers
and inter-band interpolation units may be provided according to the number of frequency bands
to be separated.
[0099]
It is a block diagram which shows the circuit structure of an audio apparatus.
It is a block diagram which shows the circuit structure of a sound processing part.
It is the schematic which shows the relationship between the waveform of the basic sampling
function used with the interpolation part classified by zone ¦ band of this invention, and the
waveform of a control sampling function.
It is a block diagram which shows the circuit structure of the interpolation part classified by zone
¦ band.
It is the schematic which shows the positional relationship of four data according to band, and an
attention point.
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It is a block diagram which shows the detailed structure of the interpolation part classified by
zone ¦ band.
FIG. 6 is a schematic view showing an interpolation process using a basic sampling function by a
band-wise interpolation unit according to the present invention.
FIG. 6 is a schematic view showing an interpolation process using a control sampling function by
a band-wise interpolation unit according to the present invention.
It is the schematic which shows the waveform of a sampling function when changing a variable
parameter.
It is the schematic which shows the frequency characteristic when changing a variable
parameter.
It is the schematic which shows the waveform of the sampling function of the conventional
Shannon.
Explanation of sign
[0100]
3 acoustic processing unit (acoustic processing apparatus) 4 band separation unit (band
separation unit) 5 sound pressure adjustment unit (sound pressure adjustment unit) 6
interpolation processing unit (interpolation processing unit) 7 setting unit (setting unit) 8 band
synthesis unit ( Band synthesis means) 14 Function processing unit (function processing means)
18 Coefficient multiplication part (coefficient multiplication means)
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