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JPH07336793

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DESCRIPTION JPH07336793
[0001]
FIELD OF THE INVENTION The present invention relates to microphones used for video cameras.
[0002]
2. Description of the Related Art In recent years, video cameras have become smaller, lighter and
lower in price, and are widely used in many homes, and their applications are also expanding in
various fields. Along with this, there is a change from a tendency to emphasize only video
recording to a tendency to also emphasize sound information recording, and it is desirable that
the user can experience a sense of presence at the time of reproduction more than at the time of
reproduction. Hereinafter, a conventional video camera microphone will be described with
reference to the drawings.
[0003]
FIG. 4 is a block diagram of a conventional microphone for a video camera. 1 is an angle of view
detection means, 3 is a stereo sound pickup means, 4 is an acoustic zoom control means, and 5 is
an acoustic signal recording means. 10 is a superdirective sound collecting unit, 11 is a stereo
sound collecting unit.
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[0004]
In the above configuration, when recording of a video camera is started, an audio signal is input
to the stereo sound collecting means 3. For example, the stereo sound pickup means 3 may be
configured by a superdirective sound pickup unit 10 and a stereo sound pickup unit 11 as shown
in the figure. In this case, the superdirective sound pickup unit 10 is composed of two single
directional microphone units, and the directivity pattern changes in a low frequency range and a
high frequency range, and an input with reduced wind noise and mechanical vibration noise A
signal is output to the acoustic zoom control means 4. On the other hand, in the stereo sound
pickup unit 11, two single directional microphone units are configured such that the main axes
of their directivity are at an angle of 90 °, and the input signal is an acoustic zoom control as a
left and right two channel signal It is outputted to the means 4. The angle of view detection
means 1 detects the zoom position in synchronization with the operation of the optical zoom
lens, and outputs a zoom position signal to the acoustic zoom control means 4. The acoustic
zoom control means 4 controls the output signal levels of the superdirectivity sound pickup unit
and the stereo sound pickup unit which are output signals of the stereo sound pickup means 3
according to the zoom position signal from the angle of view detection means 1. The respective
signals are then added and output to the acoustic signal recording means 5 as stereo signals of
two channels. The acoustic signal recording means 5 records the output signal.
[0005]
In this way, sound is collected by superdirectivity at the time of telephoto, and stereo sound
collection is performed synchronously with the zoom of the image at the wide angle, and
integration of the image and sound is realized.
[0006]
In such a conventional microphone for a video camera, the acoustic zoom control means 4 uses
the zoom position signal from the angle of view detection means 1 to output the output signal
level of the stereo sound pickup means 3. In the case of control, that is, in the case of controlling
the system sensitivity, the increase / decrease level is constant regardless of the frequency.
However, since the sensitivity is different between the high frequency component and the low
frequency component for the same level change, there is a problem that the reproduced timbre is
different depending on the control result of the level.
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[0007]
The present invention solves the above-mentioned problems, and is for a video camera which
realizes the zoom of a sound image with a constant tone regardless of the change in the output
signal level of the stereo sound pickup means accompanying the change in zoom magnification
of the optical lens in the acoustic zoom control means. The purpose is to realize a microphone.
[0008]
In order to achieve the above object, the present invention provides an angle of view detection
means 1 for detecting a zoom position signal of an optical lens, and a stereo sound pickup means
3 for collecting an audio signal in stereo. Acoustic zoom control means 6 for controlling the level
of the output signal from the stereo sound pickup means 3 in accordance with the loudness
curve for each frequency as a function of the zoom position signal outputted from the angle of
view detection means 1; And an acoustic signal recording means 5 for recording the stereo signal
output from the above.
[0009]
According to the present invention, according to the above configuration, by adding the audio
signal level control associated with the zoom position signal of the optical lens in accordance
with the loudness curve for each frequency, the zoom effect of the image can be obtained without
changing the timbre of the recorded sound. And get a sense of sound zoom effect.
[0010]
Embodiments of the present invention will be described hereinbelow with reference to the
drawings.
FIG. 1 is a block diagram of a video camera microphone according to a first embodiment of the
present invention.
In the figure, the same components as those of the conventional example shown in FIG.
What differs from the conventional example is the internal configuration of the acoustic zoom
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control means 6. 61 is a filter coefficient storage unit, 62 is a convolution operation unit, and 63
is a signal addition unit.
[0011]
The operation of the above arrangement will be described. First, when recording of a video
camera is started, an audio signal is input to the stereo sound collecting means 3. The process
until the output signal from the stereo sound pickup means 3 is input to the acoustic zoom
control means 6 is the same as in the prior art. The angle of view detection means 1 detects the
zoom position in synchronization with the operation of the optical zoom lens, and outputs the
zoom position signal to the acoustic zoom control means 6 as in the prior art.
[0012]
The acoustic zoom control means 6 performs the following operation. In the acoustic zoom
control means 6, with the zoom position signal value as a memory address, filter coefficients for
realizing the loudness curve corresponding to each control level are stored in advance in the
filter coefficient storage unit 61. The filter coefficient is input from the filter coefficient storage
unit 61 to the convolution operation unit 62 based on the zoom position signal value input from
the angle of view detection unit 1. Further, the output signal from the stereo sound pickup means
3 is inputted to the acoustic zoom control means 6, inputted to the convolution operation unit
62, and the convolution operation is performed. As a result, the signal addition unit 63 adds the
signals at the mixing ratio determined by the zoom position signal value, and outputs the result
to the acoustic signal recording means 5 as a stereo signal of two channels. The acoustic signal
recording means 5 records the output signal.
[0013]
As described above, by controlling the sound signal level control according to the zoom position
signal of the optical lens in accordance with the loudness curve for each frequency, the zoom
effect of the image and the zoom effect of the audio can be maintained while maintaining the
timbre of the reproduced sound. You can get a sense of experience.
[0014]
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Next, a second embodiment of the present invention will be described with reference to the
drawings.
FIG. 2 shows a block diagram of a microphone for a video camera in the second embodiment of
the present invention. The angle of view detection means 1, the stereo sound collection means 3,
and the acoustic signal recording means 5 are the same as in the first embodiment. What differs
from the first embodiment is the internal configuration of the acoustic signal control means 7.
[0015]
The sound signal control means 7 changes the characteristics of the input signal from the stereo
sound collecting means 3 so as to change the spatial impression in response to the zoom position
signal from the angle of view detection means 1. For example, when control is performed to
increase the sense of spread at the time of telephoto and decrease at the time of wide angle, the
sound pressure frequency characteristics in which the frequency band correlating to the sense of
spread is changed stepwise corresponds to the zoom position signal. Then, the filter coefficient is
determined by inverse Fourier transform, and the zoom position signal is stored in the expansion
feeling filter coefficient storage unit 71 with the memory address. A band that is particularly
correlated with the sense of spread is 320 Hz in the 1/3 octave band. In the acoustic signal
control means 7, the filter coefficients at the memory address corresponding to the zoom
position signal value inputted from the angle of view detection means 1 are taken out from the
spread feeling filter coefficient storage unit 71 and set in the convolution operation unit 72. The
signal from the stereo sound pickup means 3 is converted by the convolution operation unit 72
by the convolution operation. The converted signals are added as in the first embodiment and
stored in the acoustic signal recording means 5.
[0016]
As described above, by converting the characteristics of the acoustic signal by coupling to the
zoom magnification and recording the signal to which the sense of spread is added, the sense of
spread is large in the case of long distance at the time of reproduction, and in the case of
proximity. It is possible to realize the sound more in the image, such as narrowing the width of
the sound image.
[0017]
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Next, a third embodiment of the present invention will be described with reference to the
drawings.
FIG. 3 shows a block diagram of a microphone for a video camera in the third embodiment of the
present invention. The angle of view detection means 1, the stereo sound collection means 3, and
the acoustic signal recording means 5 are the same as in the first embodiment. 9 is an elevation
angle detection means, 8 is an acoustic signal control means. 81 is a filter coefficient storage
unit, 82 is a convolution operation unit, and 83 is a signal addition unit. Here, the filter
coefficients of the filter coefficient storage unit 81 are created as follows.
[0018]
By controlling the sound pressure frequency characteristics, the height of the sound image is
changed. Therefore, the sound pressure frequency characteristic in which the level of the band
correlated with the height of the sound image is changed is created with the number of steps of
the height of the sound image to be controlled, and the filter coefficient is determined by the
inverse Fourier transform. As a band correlated with the height of the sound image, bands of 200
Hz, 5 K to 10 KHz, and 16 KHz in the 1/3 octave band can be mentioned.
[0019]
The operation in the above configuration will be described. When recording is started, an audio
signal is taken in by the stereo sound collecting means 3. Also, the target direction of the video
camera is detected by the elevation angle detection means 9 every hour as an elevation angle
from the horizontal plane, and is inputted to the acoustic signal control means 8 as an elevation
angle signal. For example, a level may be incorporated as elevation angle detection means 9. In
the acoustic signal control means 8, the filter coefficient is output from the filter coefficient
storage unit 81 to the convolution operation unit 82 corresponding to the data information of
the elevation signal, and is set as a filter. In the convolution unit 82, the input signal from the
stereo sound pickup means 3 is convoluted with the filter. The filtered signal is added by the
signal addition unit 83 at the mixing ratio determined by the zoom position signal value obtained
by the angle of view detection means 1 and output to the acoustic signal recording means 5 as a
stereo signal of two channels. . The acoustic signal recording means 5 records the output signal.
[0020]
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As described above, by controlling the collected sound signal, it is possible to obtain a sound
image corresponding to the movement of the video camera at the time of reproduction, and it is
possible to realize the realism of the site.
[0021]
In the second embodiment, the frequency to be controlled is set to a specific value by focusing on
the sense of expansion of the sound image, but other bands are controlled similarly by changing
the data of the filter coefficient storage unit Also, the contour of the sound can be changed in
conjunction with the zoom position signal.
[0022]
In the third embodiment, only the height of the sound image coupled to the elevation signal is
controlled. However, the sense of reality may be further enhanced by combining with the sense
of spread as in the second embodiment.
[0023]
As described above, according to the present invention, by controlling the sound signal level
control associated with the zoom position signal of the optical lens in accordance with the
loudness curve for each frequency, the zoom of the image is maintained while maintaining the
timbre of the reproduced sound. It is possible to obtain a sense of unity between the effect and
the zoom effect of audio.
[0024]
In addition, by converting the characteristics of the acoustic signal by coupling to the zoom ratio
and recording the signal to which a sense of spread is added, the sense of spread is large in the
case of long distance during reproduction, and the width of the sound image in the case of
proximity. It is possible to realize the sound that was more in the image, such as
[0025]
Furthermore, by controlling the height of the sound image of the sound signal collected by the
stereo sound collecting means in accordance with the change of the elevation signal obtained by
the elevation detection means for detecting the target direction of the video camera, At the time
of reproduction, a sound image corresponding to the movement of the video camera can be
obtained, and a more realistic presence on the site can be realized.
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