JP2001189999

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DESCRIPTION JP2001189999
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
stereo sense emphasizing device and a stereo sense emphasizing method, and in particular, it is
necessary to emphasize left and right components of an input signal consisting of two stereo
signals. The present invention relates to stereo sense enhancement technology in audio signal
processing.
[0002]
2. Description of the Related Art As shown in FIG. 7, a conventional stereo sense emphasizing
device delays a first audio signal input (for example, left audio signal) 701 consisting of two left
and right stereo signals for a predetermined time. An element 705, a second delay element 706
for delaying a second audio signal input (for example, right audio signal) 702 consisting of left
and right two stereo signals for a predetermined time, and an output of the first delay element
705 are multiplied by a predetermined value. A first multiplier 707, a second multiplier 708 for
multiplying the output of the second delay element 706 by a predetermined value, a first input
and an output of the second multiplier 708, and a first output 709, and a second adder 704 that
adds the second input and the output of the first multiplier 707 to generate a second output 710,
From left and right two stereo signals That has a function to emphasize the respective
components 701 and 702 left and right input signals.
[0003]
However, the conventional stereo sense emphasizing device as described above has the
amplitude characteristic by the frequency as shown in FIGS.
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[0004]
Here, FIG. 8 shows an amplitude characteristic according to the sound source position in the
conventional example, in a case where the sound source position is rotated 180 degrees with the
left facing 0 degrees from the microphone, the microphone width: 3 cm, a multiplier as a
measurement condition The coefficients 707 and 708 are 0.9375, the sampling frequency is
44.1 kHz, and the delay element 705 is 706: 1 tap.
In the figure, L represents a left audio signal and R represents a right audio signal.
[0005]
FIG. 9 shows an amplitude characteristic according to the frequency of the conventional example,
the sound source position is 20 degrees, and other conditions are the same as FIG.
In the figure, L represents a left audio signal, R represents a right audio signal (the same applies
hereinafter). FIG. 10 similarly shows an amplitude characteristic according to the frequency of
the conventional example, the sound source position is 40 degrees, and the other conditions are
the same as FIG. FIG. 11 similarly shows an amplitude characteristic according to the frequency
of the conventional example, the sound source position is 60 degrees, and the other conditions
are the same as FIG.
[0006]
The conventional stereo sense emphasizing device has an amplitude characteristic with a unique
frequency as shown in FIG. 8 to FIG. 11, so there are problems to be solved as follows.
[0007]
1.
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The level difference between the first output and the second output is small in the frequency
band that achieves stereo feeling (the spread of localization by a plurality of sound sources).
[0008]
2. The level drops significantly in the low frequency band.
[0009]
The object of the present invention is to solve the above-mentioned problems, and to emphasize
each of the left and right components of an input signal consisting of two left and right stereo
signals in a frequency range where stereo feeling is realized, Even in a compact case where the
level difference is very small, the output signal can produce a localization of sound, and
furthermore, it can enhance stereo feeling that can prevent a significant level reduction in the
low frequency of the output signal. Device and stereo sense emphasizing method
[0010]
In order to achieve the above object, the invention of the stereo sense emphasizing device
according to claim 1 is a first delay means for delaying the first audio signal output of the two
left and right stereo signals for a predetermined time. A first multiplication means for multiplying
the output of the first delay means by a predetermined value, a second delay means for delaying
the second audio signal output of the left and right two stereo signals for a predetermined time,
and A second speech unit for multiplying the output of the second delay means by a
predetermined value, and a first speech signal input of the left and right two stereo signals and
an output of the second multiplication means to obtain a first speech A first addition means for
outputting a signal output, and a second audio signal output by adding the second audio signal
input of the left and right two stereo signals and the output of the first multiplication means And
the first delay means is The first audio signal output from the first addition means is delayed for
a predetermined time, and the second delay means is for delaying the second audio signal output
from the second addition means for a predetermined time. It is characterized by
[0011]
Here, the left and right components of the input signal consisting of the left and right two stereo
signals may be further emphasized in a frequency range where stereo feeling is realized.
[0012]
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In addition, the frequency range in which the stereo feeling is realized may be a frequency range
of about 102 to 104 Hz.
[0013]
Further, the stereo feeling emphasizing device is included in an audio signal processing device
attached to a relatively small casing and processing audio signals input from two left and right
stereo microphones with a relatively short distance between the microphones with respect to a
sound source. Can be characterized.
[0014]
The audio signal processing apparatus may be an audio signal processing apparatus incorporated
in a digital video camera.
[0015]
In order to achieve the above object, the invention of the stereo sense emphasizing method
according to claim 6 comprises: a first delay step of delaying the first audio signal output of the
left and right two stereo signals for a predetermined time; A first multiplication step of
multiplying the output by a predetermined value, a second delay step of delaying the second
audio signal output of the left and right two stereo signals by a predetermined time, and a
predetermined value of the output of the second delay step And adding a first audio signal input
of the left and right two stereo signals and an output of the second multiplication step to output a
first audio signal output. And a second addition step of adding a second audio signal input of the
left and right two stereo signals and an output of the first multiplication step to output a second
audio signal output, First day I step delays the first audio signal output that is the output of the
first addition step for a predetermined time, and the second delay step is the second audio signal
output that is the output of the second addition step May be delayed for a predetermined time.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described in detail with reference to the drawings.
[0017]
FIG. 1 shows a circuit configuration of a stereo sense emphasizing device according to an
embodiment of the present invention.
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Here, 105 is a first delay element that delays the output (first output) 109 of the first adder 103
for a predetermined time, and 106 is a predetermined output (second output) 110 of the second
adder 104. A second delay element delaying in time, a first multiplier 107 multiplying the output
of the first delay element 105 by a predetermined value, and a second multiplier 108 multiplying
the output of the second delay element 106 by a predetermined value The first adder 103 adds
the first audio signal input (for example, the left audio signal) 101 consisting of left and right two
stereo signals and the output of the second multiplier 108 and And the second adder 104 adds
the second audio signal input (for example, the right audio signal) 102 consisting of left and right
two stereo signals and the output of the first multiplier 107 2. Generate an output 110 of two.
That is, in the present invention, the result obtained by adding the product obtained by
multiplying the second output by delaying and multiplying and the first input is output as the
first output, and the product by multiplying the first output by delaying The point of outputting
the result of adding the second input and the second input as the second output is a point
different from the conventional configuration in which the first and second inputs are delayed
and multiplied as shown in FIG.
[0018]
Next, the operation of the present invention according to the configuration of FIG. 1 will be
described.
[0019]
For example, since the housing (not shown) of a digital video camera is generally small, the audio
signal input of stereo by two microphones has a small difference in amplitude.
[0020]
Therefore, the input signal from the sound source of a sufficiently distant sine wave having an
incident angle θ to the microphone L and the microphone R in FIG. 2 with the same amplitude
between two input signals here is the first input (Lin) of the microphone L The second input (Rin)
of the microphone R can be obtained by the following equation based on
[0021]
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ω is the frequency of the input signal, A is the amplitude.
Let l be the distance between the two microphones.
The second input (Rin) is input later or earlier as in the above equation than the first input
because v is the speed of sound and the sound source is sufficiently far.
[0022]
In the case of the circuit configuration of the conventional example shown in FIG. 7, the first and
second outputs Lout and Rout have the coefficient of the multipliers 701 and 702 as p and the
delay time of the delay elements 705 and 706 as td. ,
[0023]
Differentiate each with respect to time,
[0024]
If t is obtained and substituted into the original expression, the maximum value of the output
with time, that is, the amplitude as a function of the frequency of the input signal, for the first
output,
[0025]
For the second output,
[0026]
Here, the transfer function in the circuit of one embodiment of the present invention in FIG. 1 is
represented using z conversion, and an equation for obtaining the first output (Lout) of 109 is
shown below.
Assuming that the number of delay elements 105 and 106 is q,
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[0027]
The term after the fraction is equal to the z-transform of the output of the conventional example.
This is also true for the second input of 102.
In the circuit according to the embodiment of the present invention, the amplitude characteristic
at the frequency of the conventional example described above is newly added.
[0028]
The transfer function of
Therefore, assuming that the sampling period is T, the amplitude characteristic of the circuit of
the embodiment of the present invention is
[0029]
It can be expressed as.
This newly multiplied term is mainly responsible for lifting the low frequency band, and serves to
prevent the level decrease in the conventional low frequency band.
[0030]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As an embodiment of the present
invention, the circuit of FIG. 1 is implemented on a semiconductor substrate using a digital
circuit.
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As an example, two inputs 101 and 102 are parallel signals of sampling frequency 2.8 MHz and
10 bits, and 90 tap delay element units 105 and 106 are respectively 10 × 90 flip flop circuits
and 10 adders 103 and 104 respectively. It consists of a full adder.
The multipliers 107 and 108 consisted of 10 sets of full adders and simple array multipliers with
NAND (non-conjunction) elements, respectively.
[0031]
Then, it has been confirmed that the telephony feeling emphasizing circuit according to the
present invention configured as described above has a characteristic amplitude characteristic
according to the frequency as shown in FIGS.
[0032]
Here, FIG. 3 shows an amplitude characteristic according to the sound source position of the
present invention, where the sound source position is rotated 180 degrees with the left facing 0
degrees from the microphone, and the measurement conditions are the same as the conventional
example of FIG. The microphone width is 3 cm, the coefficients of multipliers 707 and 708 are
0.9375, the sampling frequency is 44.1 kHz, and the delay element 705 is 706 taps.
In the figure, L represents a left audio signal and R represents a right audio signal.
[0033]
FIG. 4 shows the amplitude characteristic according to the frequency of the present invention,
the sound source position is 20 degrees, and other conditions are the same as FIG.
In the figure, L represents a left audio signal, R represents a right audio signal (the same applies
hereinafter).
FIG. 5 similarly shows the amplitude characteristic according to the frequency of the present
invention, the sound source position is 40 degrees, and the other conditions are the same as FIG.
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FIG. 6 similarly shows the amplitude characteristic according to the frequency of the present
invention, the sound source position is 60 degrees, and the other conditions are the same as FIG.
[0034]
Comparing the amplitude characteristics according to the present invention shown in FIGS. 3 to 6
with the amplitude characteristics according to the prior art shown in FIGS. 8 to 11, it can be
seen that the present invention has the following remarkable advantages.
[0035]
In the present invention, for example, when the sound source position is 20 degrees, as shown in
FIG. 4, the difference between the amplitudes of the L output signal and the R output signal is 20
degrees in the frequency band of 102 to 104 Hz. This is significantly larger than that of the
conventional example of No. 9.
This tendency is similar to the case where the sound source position is 40 degrees and 60
degrees.
Thus, according to the present invention, the left and right components of an input signal
consisting of two stereo signals on the left and right are more likely to be in a frequency range
(102 to 104 Hz) where stereo feeling (spreading of localization by a plurality of sound sources) is
realized. It can be emphasized. Therefore, according to the present invention, even in a case such
as a digital video camera in which the level difference between the left and right inputs is very
small, it is possible for the output signal to spread the localization of sound.
[0036]
Further, at low frequencies in the output signal, in the conventional example, as shown in FIG. 8,
the gain is extremely small regardless of the angle of the sound source direction. For example,
when the L signal and the R signal are 0.1 KHz, in the conventional example of FIG. 8, the output
amplitude is approximately 0.1 regardless of the angle of the sound source direction, while in the
present invention of FIG. Is almost 0.5. Therefore, according to the present invention, it is
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possible to prevent a significant level drop at low frequencies in the output signal.
[0037]
Further, comparing the amplitude characteristics of the present invention of FIG. 3 with the
amplitude characteristics of the conventional example of FIG. 8, the present invention provides a
gain by frequency at a sound source direction of 90 degrees, that is, in front of a housing such as
a digital video camera. Variation is small. (Other Embodiments) Note that the present invention is
applied to a system including a plurality of devices (for example, a host computer, an interface
device, a reader, a printer, etc.), and an apparatus consisting of one device (for example, The
present invention may be applied to video cameras, portable stereo recording devices, etc.).
[0038]
Further, an object of the present invention is to provide a system or apparatus with a recording
medium (storage medium) in which not only the above-described hardware configuration but
also a program code of software for realizing the functions of the above-described embodiments
are recorded. It is needless to say that the computer (or CPU or MPU) of the system or apparatus
reads out and executes the program code stored in the recording medium. In this case, the
program code itself read out from the recording medium realizes the functions of the abovedescribed embodiments, and the recording medium recording the program code constitutes the
present invention. As a recording medium for recording the program code and variable data such
as a table, for example, a floppy disk (FD), a hard disk, an optical disk or the like can be used.
[0039]
As described above, according to the present invention, the result obtained by adding the product
obtained by multiplying the second output by delaying and multiplying the result by the first
input is output as the first output. Since the result obtained by adding the product obtained by
delaying and multiplying the output of 1 and the second input is output as the second output, the
left and right components of the input signal consisting of the left and right two stereo signals
are stereo It is possible to emphasize more in the frequency range where the sense is realized, so
that even in the case where the level difference between the left and right inputs is very small,
the output signal can exhibit the spread of sound localization, and the output A significant level
drop can be prevented at low frequencies in the signal, and further, the effect of small variation
in gain due to frequency can be obtained when the sound source direction is 90 degrees in front.
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