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JP2001052444

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DESCRIPTION JP2001052444
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
audio reproduction apparatus, and more particularly to an audio reproduction apparatus
provided with a compressor for compressing the dynamic range of an audio reproduction signal.
[0002]
2. Description of the Related Art In a sound reproducing apparatus, when the dynamic range of a
sound source such as a CD player is wide, that is, when the difference between a large sound and
a small sound is large, the allowable input of the power amplifier is There may be a problem that
distortion is generated over and a problem that adversely affects the ear due to a large volume
when using headphones. Also, conversely, the sound may not be heard at a portion where the
signal level from the sound source is low, and this problem is particularly noticeable in a carmounted acoustic device where it is usual to listen in an environment where there is running
noise. As a means for solving such a problem, there is a method of using a compressor which
compresses the dynamic range according to the input signal level.
[0003]
FIG. 6 is a block diagram showing an example of such a compressor. An output signal from the
sound source 51 is input to a level calculating unit 53, and the level calculating unit 53 detects
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an input signal level. The output signal from the sound source 51 is also input to the delay circuit
52, and after being subjected to delay processing for the processing time in the level calculation
unit 53 in the delay circuit 52, the signal is output to the gain adjustment unit 54. Then, the
acoustic signal input to the gain adjustment unit 54 is amplified at an amplification factor
corresponding to the input signal level calculated by the level calculation unit 53 (the
amplification factor decreases as the input signal level increases), and then the power is obtained.
The power is amplified by the amplifier 55 and output as sound from the speaker 56. That is, by
the process applied by the compressor, the small sound becomes large, the large sound becomes
small, and the dynamic range is compressed.
[0004]
However, a sound reproducing apparatus provided with a plurality of sound sources, such as a
radio receiver, a tape player, a CD (compact disc) player, etc., is integrated, or a DVD (Digital
Video Disc) In audio playback devices capable of playing back audio signals of different types of
discs such as DVD and CD as in players and DVDs with different recording modes (recording
formats), the dynamic range differs depending on the sound source, Also the noise levels are
different. Therefore, if compression processing is simply performed by the compressor, some
sound sources may be unnaturally reproduced, or noise components may be greatly amplified
and noise may be noticeable.
[0005]
The present invention has been made in view of these problems, and it is possible to perform
natural reproduction regardless of the type of sound source, and to perform compression
processing that does not unnecessarily increase noise. The object is to realize a sound
reproducing device that can
[0006]
SUMMARY OF THE INVENTION In order to solve the above problems, the sound reproducing
apparatus (1) according to the present invention has a plurality of sound sources, and an acoustic
signal of a sound source selected to be reproduced. In a sound reproducing apparatus for
reproducing the sound of the sound source, the compressor performing compression processing
on the sound signal of the selected sound source, type detection means for detecting the type of
the sound source selected for reproduction, and the sound source detected by the type detection
means And a compression characteristic adjusting means for adjusting the compression
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characteristic of the compressor in accordance with the type.
According to the sound reproducing apparatus (1), since the compression characteristic of the
compressor is adjusted according to the type of the sound source, it becomes possible to apply
appropriate compression processing to the sound signal according to the type of the sound
source. This makes it possible to reproduce sounds that are easy to hear, and that noise is not
noticeable.
[0007]
Further, the sound reproducing apparatus (2) according to the present invention is a sound
reproducing apparatus having a multiplayer capable of reproducing plural types of storage
media in the sound reproducing apparatus (1), wherein the type detecting means However, the
present invention is characterized in that it comprises identification means for identifying the
type of storage medium being reproduced by the multiplayer and detecting different types of
storage media as different sound sources. According to the above-described sound reproducing
apparatus (2), it becomes possible to apply an appropriate compression process to the sound
signal according to the storage medium being reproduced in the multiplayer, so that any kind of
storage medium has a natural feel It is possible to reproduce sound that is easy to hear and
inconspicuous of noise.
[0008]
Further, in the sound reproducing apparatus (3) according to the present invention, in the sound
reproducing apparatus (2), the identification means indicates the type of the storage medium
according to identification data indicating the type of the storage medium recorded in the storage
medium. It is characterized in that According to the sound reproducing apparatus (3), since the
type of the storage medium can be detected by using the reading means for reading the acoustic
signal from the storage medium, the apparatus can be realized without adding new parts, so the
size and cost can be reduced. It is advantageous to
[0009]
Further, in the sound reproducing apparatus (4) according to the present invention, in the sound
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reproducing apparatus (2), the identification means is a memory medium based on the difference
in recording format of the sound signal recorded in the memory medium. It is characterized in
that the type is identified. According to the sound reproducing apparatus (4), since the type of
the storage medium can be detected by using the reading means for reading the acoustic signal
from the storage medium, the apparatus can be realized without adding new parts, so the size
and cost can be reduced. It is advantageous to Further, it is possible to cope with the case where
different recording formats exist even with the same storage medium.
[0010]
Further, the sound reproducing apparatus (5) according to the present invention is characterized
in that, in the sound reproducing apparatus (4), the difference between the recording formats is
the number of quantization bits of sound signal data. According to the sound reproducing
apparatus (5), the sound signal is subjected to compression processing according to the number
of quantization bits of sound signal data strongly correlated with the dynamic range of the sound
signal. Appropriate compression processing is possible.
[0011]
Further, the sound reproducing apparatus (6) according to the present invention has a plurality
of sound sources, and in the sound reproducing apparatus for reproducing the sound signal of
the sound source selected to be reproduced, the sound signal of the selected sound source is
selected. Compression characteristics for adjusting the compression characteristics of the
compressor according to the dynamic range detected by the compressor that performs
compression processing, the dynamic range of the reproduced sound of the sound source
selected to be reproduced, and the dynamic range detected by the dynamic range detection unit
And adjusting means. According to the sound reproducing device (6), the compression
characteristic of the compressor is adjusted in accordance with the dynamic range of the sound
signal from the sound source, so that the sound signal is appropriately compressed according to
the dynamic range of the sound signal. This makes it possible to reproduce sounds that are
natural and easy to hear and that noise is not noticeable.
[0012]
Further, according to the sound reproducing apparatus (7) of the present invention, in the sound
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reproducing apparatus (6), the range detecting means reads data of sound signal stored in a
storage medium, and the data reading means And calculating means for calculating a dynamic
range based on the sound signal data read by the reading means. According to the sound
reproducing device (7), since the compression characteristic of the compressor is adjusted
according to the dynamic range calculated using the sound signal to be compressed itself,
appropriate compression according to the actual music to be reproduced, etc. Is applied to the
sound signal, making it possible to reproduce sound that is natural and easy to hear, and noise is
not noticeable.
[0013]
Further, according to the sound reproducing apparatus (8) of the present invention, in the sound
reproducing apparatus (7), the data reading means reads a part of sound signal data stored in a
storage medium. It is characterized by According to the above sound reproducing apparatus (8),
the dynamic range is calculated using a part of data instead of all the data, so high speed
processing is possible.
[0014]
Further, in the sound reproducing apparatus (9) according to the present invention, in the sound
reproducing apparatus (7), the data reading means reads the sound signal data stored in the
storage medium discontinuously at intervals. It is characterized by being a thing. According to
the above-mentioned sound reproducing apparatus (9), the dynamic range is calculated using a
part of data instead of all the data, so high-speed processing becomes possible, and furthermore,
since the data is uniformly sampled from the whole, accuracy The dynamic range can be
calculated well.
[0015]
Further, according to the sound reproducing apparatus (10) of the present invention, in the
sound reproducing apparatus (7), sound data storage means for storing sound signal data stored
in the storage medium read by the data reading means. And reproduction means for performing
sound reproduction using the sound signal data stored in the sound data storage means, and the
reproduction using the sound signal data stored in the sound data storage means. The data
reading control means is provided to increase the data reading speed of the data reading means,
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read the sound signal data stored in the sound data storage means at high speed, and input the
sound signal data to the calculation means. There is. According to the sound reproducing
apparatus (10), since the dynamic range can be calculated while preceding sound reproduction,
the time until sound reproduction can be shortened.
[0016]
Further, according to the sound reproducing apparatus (11) according to the present invention,
in the sound reproducing apparatus in which a plurality of speakers including a speaker for bass
reproduction are arranged, a compressor for performing compression processing on an acoustic
signal, and the speaker for bass reproduction A range detecting means for detecting a dynamic
range of an acoustic signal to be output from the unit; and a compression characteristic adjusting
means for adjusting the compression characteristic of the compressor according to the dynamic
range detected by the range detecting means. It is characterized. According to the abovementioned sound reproduction device (11), the dynamic range is calculated by the sound signal
to be output from the bass reproduction speaker which generally has a large amplitude, and the
compression characteristic of the compressor is adjusted according to the calculated dynamic
range. As a result, an appropriate compression process is applied to the sound signal according
to the actual music to be reproduced, etc., so that sound can be reproduced with a natural feeling
that is easy to hear and noise is not noticeable. Also, since the acoustic signal used for the
calculation is not calculated using the acoustic signals to all the speakers, but is calculated using
the acoustic signal to be output from the bass reproduction speaker, the configuration is
simplified, and the calculation processing is performed at high speed. It becomes.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention
will be described. FIG. 1 is a block diagram showing the configuration of a sound reproduction
apparatus according to an embodiment (1) of the present invention. The sound signals of the
respective sound sources of the radio receiver 20, the tape player 21 and the disc player 22 are
outputted to the sound source selection unit 1. The sound source selection unit 1 is a switch
circuit composed of mechanical switches such as relays and transistors, and outputs only the
sound signal of the sound source for which reproduction is selected to the delay circuit 2 and the
level calculation unit 9 in the subsequent stage.
[0018]
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The level calculating unit 9 detects an acoustic signal level. The level calculation unit 9 is
configured of a digital signal processing circuit that calculates an average value of the acoustic
signal by digital operation. Note that the level calculating unit 9 can also be configured by a
detection circuit that performs envelope detection on an acoustic signal, and a rectification
smoothing circuit that rectifies and smoothes the envelope detection signal. The sound signal
level calculated by the level calculating unit 9 is output to a gain calculating unit 8 that controls
the gain of the gain adjusting unit 3 described later.
[0019]
The gain calculating unit 8 calculates the gain of the gain adjusting unit 3 based on the acoustic
signal level and a characteristic signal indicating compression characteristics from the
microcomputer 10 (to be described later), and outputs the calculated gain to the gain adjusting
unit 3. The gain of the adjustment unit 3 is controlled. The gain calculation unit 8 is configured
by a digital signal processing circuit that calculates the gain to be output to the gain adjustment
unit 3 from the characteristic signal indicating the sound signal level and the compression
characteristic by digital operation.
[0020]
The sound signal from the sound source is subjected to delay processing for the processing time
in the level calculating unit 9 and the gain calculating unit 8 in the delay circuit 2, and is output
to the gain adjusting unit 3. The acoustic signal input to the gain adjustment unit 3 is amplified at
an amplification factor corresponding to the gain calculated by the gain calculation unit 8 (the
amplification factor decreases as the input signal level increases). The gain adjustment unit 3 is
configured of an amplification factor variable amplification circuit (may be an attenuation factor
variable attenuation circuit) in which an output signal from the gain calculation section 8 is
applied to the amplification factor control terminal, and calculation is performed with variable
feedback amount. It can be realized by an electronic circuit constituted by an amplification
circuit, a ladder resistance whose attenuation factor is changed by an input signal to a control
terminal, and the like.
[0021]
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An output signal from the gain adjusting unit 3 is input to a volume adjusting unit 4 formed of an
electronic volume to adjust the output signal level (all frequency bands are uniformly
attenuated). The attenuation amount in the volume adjustment unit 4 is controlled by the volume
adjustment signal from the microcomputer (microcomputer) 10. The volume adjustment signal
from the microcomputer 10 is output according to a signal from the operation unit 11 including
a push button or the like, that is, according to the operation situation of the operation unit 11 by
the user. Thereafter, the output signal from the volume adjustment unit 4 is power-amplified by
the power amplifier 5 and output from the speaker 6 as sound.
[0022]
The microcomputer 10 controls the sound source selection state of the sound source selection
unit 1 based on the operation state of the operation unit 11 (selection of the reproduction sound
source). The disc player 22 outputs to the microcomputer 10 a reproduction type signal
indicating the type of disc (CD or DVD) to be reproduced and the reproduction mode in the DVD.
The identification of the type of disc and the reproduction mode is identified by a signal relating
to a recording format included in the data recorded on the disc, for example, the number of
quantization bits of the acoustic signal (how many bits represent the acoustic signal level).
[0023]
On the other hand, the memory 12 is constituted by a ROM, and the memory 12 stores a sound
source selection state and reproduction type signal and a characteristic signal indicating
compression characteristics in association with each other. Then, the microcomputer 10 searches
the memory 12 for the characteristic signal indicating the compression characteristic based on
the sound source selection state and the reproduction type signal in the sound source selection
unit 1 (and the selection state of the compression characteristic by the user's operation unit 11).
It is output to the gain calculation unit 8. It is also possible to employ a method of calculating the
characteristic signal indicating the compression characteristic by a predetermined arithmetic
expression in which the sound source selection state and the reproduction type signal in the
sound source selection unit 1 are variables.
[0024]
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FIG. 2 is a diagram showing an example of compression characteristics (input and output
characteristics) stored in the memory 12. (A) shows a radio receiver, (B) shows a tape player, (C)
Shows a case of a disc player (CD, DVD mode (1): large number of quantization bits, DVD mode
(2): small number of quantization bits). In these compression characteristics, the dynamic range
of the input signal is L1 to L5, and the dynamic range of the output signal is L6. These
compression characteristics are not limited to the characteristics shown in FIG. 2, and
appropriate characteristics obtained by experiments may be stored in the memory 12.
[0025]
FIG. 3 shows an example of the storage state of the compression characteristics (input / output
characteristics) stored in the memory 12. In the memory 12, each sound source (including the
type of disc and the reproduction mode) 31 is shown. Parameters such as compression ratio
(dynamic range of input signal / dynamic range of output signal), threshold (input signal level at
a position where the output signal level rises from 0 to a predetermined level) are stored. The
memory 12 stores data as shown in FIG. 3 for each selection state of compression characteristics
(including non-compression) by the user through the operation unit 11. Then, data of the output
level 30 for each input level 32 corresponding to the sound source for which reproduction is
selected is output to the gain calculation unit 8, and the gain calculation unit 8 controls the gain
adjustment unit 3 based on this data.
[0026]
Next, the compression characteristic selection process performed by the microcomputer 10 will
be described. FIG. 4 is a flowchart showing the compression characteristic selection process
performed by the microcomputer 10. This process is executed when there is an operation to
change the compression characteristics, such as switching of the sound source. In step S1, the
compression mode, that is, the selection state of the compression characteristics (including noncompression) by the operation unit 11 of the user is input, and the process proceeds to step S2.
In step S2, it is determined from the operation status (uncompressed) of the operation unit 11
whether compression processing is to be performed or not. If compression is not performed,
processing proceeds to step S3. If compression processing is performed, processing proceeds to
step S4. In step S3, the compression control is released, that is, the characteristic data to be in a
non-compression state is output to the gain calculation unit, and the process is finished.
[0027]
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In step S4, a sound source for which reproduction is selected is detected, and the process
proceeds to step S5. In step S5, it is determined whether the sound source whose reproduction is
selected is a disc player. If it is a disc player, the process proceeds to step S6, and if it is not a
disc player, the process proceeds to step S7. In step S6, in order to identify the type of disc to be
reproduced by the disc player and the reproduction mode, the recording format of the data
recorded on the disc is detected to identify the type of disc and the reproduction mode, and the
process proceeds to step S7. . In step S7, the data in the memory 12 is searched according to the
detected sound source, the type of disc and the reproduction mode to detect the compression
characteristic, and the process proceeds to step S8. In step S8, compression control is performed
by outputting the data of the detected compression characteristic to the compression calculation
unit 8, and the process ends.
[0028]
Therefore, according to the sound reproducing apparatus of the embodiment (1), the
compression characteristics of the compressor are adjusted according to the type of sound
source, the type of disc and the reproduction mode, so the type of sound source and the type of
disc An appropriate compression process is applied to the sound signal according to the
reproduction mode, and the sound reproduction is made natural and easy to hear and
inconspicuous in noise. In addition, since the type of the disk (storage medium) and the
reproduction mode (quantization bit etc.) are detected using the reading means for reading the
acoustic signal from the storage medium, the program change of the microcomputer 10 is made
without adding new parts. Since it can be realized, it is advantageous for downsizing and cost
reduction.
[0029]
In the sound reproducing apparatus according to the above embodiment (1), the compression
characteristics of the compressor are adjusted in accordance with the type of sound source, the
type of disc and the reproduction mode, but from the sound source It is also possible to calculate
the dynamic range of the reproduced sound from the reproduced sound itself before sound
output, and adjust the compression characteristic of the compressor by the calculated dynamic
range. In this case, since the compression characteristic is adjusted according to the actual
dynamic range, the compression characteristic corresponds to the recording content of the
storage medium (the recording level of the acoustic signal), and the compression characteristic
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can be adjusted with higher accuracy. In addition, by performing measurement of the dynamic
range using a part of the acoustic signal data instead of all the data, the processing time can be
shortened and the time to the audio reproduction output can be shortened. By temporally
separating the sampling timing of (1), it is possible to prevent deviation of data and to detect the
dynamic range with high accuracy.
[0030]
Next, the embodiment (2) will be described. FIG. 5 is a block diagram showing the configuration
of a vehicle-mounted audio reproduction apparatus according to the second embodiment. The invehicle acoustic reproduction device according to the second embodiment includes a multitrack
sound source 41 that outputs different acoustic signals for each of the speakers disposed in the
vehicle compartment. The sound source 41 outputs digital data of an acoustic signal to the
memory 42, and the memory 42 stores the digital data. Sound data is written from the sound
source 41 to the memory 42 at a speed higher than the sound reproduction speed until the data
is stored to the full capacity of the memory 42. Sound data is output from the memory 42 at a
speed corresponding to the sound reproduction speed, and the data is erased from the memory
42. Therefore, even if the output signal from the sound source 41 is interrupted due to vibration
or the like, the sound reproduction is continued by the output signal from the memory 42, and
the sound disconnection is prevented.
[0031]
An output signal from the memory 42 is input to a DSP (digital signal processor) 44 that digitally
processes digital data of an acoustic signal, and the DSP 44 performs compression processing.
The processing in the delay circuit 2, the gain adjustment unit 3, the level calculation unit 9, and
the gain calculation unit 8 shown in FIG. 1 is realized by the arithmetic processing of the DSP 44,
and the control signal from the microcomputer 48 generates an acoustic signal. The signal is
subjected to the same compression processing as that shown in FIG.
[0032]
The audio signal compressed in the DSP 44 is converted into an analog audio signal in a digital /
analog converter (D / A) 46. A sound signal output from the D / A 46 is processed by a
preamplifier (PRAMP) 47 that performs volume control, sound quality control, sound field
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control, etc., and a power amplifier CA (for center front playback sound) that performs power
amplification to a level that allows voice reproduction. (For left front playback sound), FRA (for
right front playback sound), RLA (for left rear playback sound), RRA (for right rear playback
sound), WA (for center rear bass sound) power amplified, and then in the car cabin Speaker CS
(center front arrangement), FLS (left front arrangement), FRS (right front arrangement), RLS (left
rear arrangement), RRS (right rear arrangement), WS (center rear) arranged at front / rear, left /
right and back center for voice reproduction Arrangement: A speaker for reproducing bass is
converted to an audio signal and reproduced. Although D / A 46 and PRAMP 47 are shown in a
single configuration, a configuration for six channels exists inside. In addition, the volume and
sound quality control performed by the PRAMP 47 can also be performed by the digital
operation processing of the DSP 44. In that case, only the operation program of the DSP 44
needs to be slightly changed. It is advantageous in terms of
[0033]
Of the sound signal data stored in the memory 42, data to be output from the bass reproduction
speaker WS is output to the range detection unit 45, and the dynamic range of the acoustic
signal to be output to the bass reproduction speaker WS Is detected. The detection of the
dynamic range can be detected by calculating the average level or peak level of all data of the
acoustic signal stored in the memory 42. Incidentally, by performing measurement of the
dynamic range using a part of the acoustic data instead of all the data, the processing time can be
shortened and the time required for the audio reproduction output can be shortened. By
temporally separating the sampling timing of the acoustic data, it is possible to prevent the bias
of the data and accurately detect the dynamic range. The data output from the memory 42 to the
range detection unit 45 is output regardless of the acoustic reproduction, and the speed thereof
is high in the processable range as compared to the case of the acoustic reproduction.
[0034]
The memory 43 is configured in the same manner as the memory 12 shown in FIG. 1, and stores
data of compression characteristics in association with the dynamic range. Then, the
microcomputer 48 searches the memory 43 for a characteristic signal indicating compression
characteristics based on the dynamic range detected by the range detection unit 45, and outputs
the characteristic signal to the DSP 44. Further, the microcomputer 48 performs operation
control of the sound source 41 and the memory 42 for sound reproduction and detection of the
dynamic range in the range detection unit 45.
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[0035]
Therefore, according to the sound reproducing apparatus of the embodiment (2), since the
compression characteristic of the compressor is adjusted according to the actual dynamic range
of the reproduced music recorded on the storage medium, An appropriate compression process
is applied to the sound signal according to the music to be reproduced, so that sound
reproduction that is natural and easy to hear and inconspicuous of noise is possible. In addition,
since the dynamic range can be calculated while preceding the sound reproduction, the time to
sound reproduction can be shortened. Also, the dynamic range is calculated using the acoustic
signal to be output from the bass reproduction speaker, which generally has a large amplitude,
instead of calculating the acoustic signal used for the calculation using the acoustic signals to all
the speakers. Therefore, the configuration is simplified, and the speed of calculation processing
can be increased.
[0036]
Brief description of the drawings
[0037]
1 is a block diagram showing a configuration of a sound reproduction apparatus according to the
embodiment (1) of the present invention.
[0038]
2A to 2C are characteristic diagrams showing compression characteristics.
[0039]
3 is a data storage state table diagram showing the data storage state of the memory.
[0040]
4 is a flowchart showing the processing performed by the microcomputer.
[0041]
5 is a block diagram showing a configuration of a vehicle-mounted sound reproduction apparatus
according to the embodiment (2) of the present invention.
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[0042]
6 is a block diagram showing a configuration of a conventional sound reproduction apparatus.
[0043]
Explanation of sign
[0044]
DESCRIPTION OF SYMBOLS 1 ... Sound source selection part 2 ... Delay circuit 3 ... Gain
adjustment part 8 ... Gain calculation part 9 ... Level calculation part 10 ... Microcomputer 20 ...
Radio receiver 21 ... Tape player 22 ... Disc player
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