Electrical audio signal processing systems and devices – Binaural and stereophonic – Pseudo stereophonic
Reexamination Certificate
2000-06-06
2004-02-10
Harvey, Minsun Oh (Department: 2644)
Electrical audio signal processing systems and devices
Binaural and stereophonic
Pseudo stereophonic
C381S001000
Reexamination Certificate
active
06690799
ABSTRACT:
The present invention relates to a stereo signal processing apparatus, and more particularly, to a stereo signal processing apparatus having a vocal cancel function to remove vocal signals included in left and right input signals.
Conventionally, as a circuit to cancel vocal components (vocal signals) from left and right input stereo signals mixedly including vocal and instrumental plays and obtain a monophonic play signal, a circuit as shown in
FIG. 7
is employed.
This circuit has a left low-pass filter
11
that extracts a left low-frequency signal and a left high-pass filter
12
that extracts a left high-frequency signal, from a left input signal (Lin), a right low-pass filter
21
that extracts a right low-frequency signal and a right high-pass filter
22
that extracts a right high-frequency signal, from a right input signal (Rin), subtraction means
31
that performs subtraction between the right input signal (Rin) and the left input signal (Lin) to generate a vocal removal signal, left addition means
13
that adds the left low-frequency signal and the left high-frequency signal to the vocal removal signal to generate a left output signal (Lout), and right addition means.
23
that adds the right low-frequency signal and the right high-frequency signal to the vocal removal signal to generate a right output signal (Rout).
Note that at this stage, explanation will be made on the presumption that numerals
41
to
44
do not exist in FIG.
7
.
First, the left and right filters respectively extract a low-frequency signal and a high-frequency signal except an intermediate frequency including a vocal signal in advance. At this stage, the vocal signal is not included, further, an intermediate component significant as music is missing. Then, the subtraction between the left input signal and the right input signal cancels the vocal signals precisely located around the center of the stereo signals, and generates a vocal removal signal. In the vocal removal signal, the vocal signals are canceled, but signal components having different phases remain in the left and right signals. Then, the vocal removal signal is added to the respective left and right low-frequency signals and high-frequency signals, to generate stereo signals where all the frequency components are included and the vocal signals are removed.
In the above circuit, to cancel the vocal signals, the intermediate component significant as music is generated by the subtraction means
31
. Accordingly, the intermediate component is a single signal, i.e., a monophonic signal. The monophonic signal is added to the left and right signals.
As a result, when a user listens to it as music, the stereo effect is missing or degraded.
To compensate for this omission of stereo effect, it is necessary to use an expensive member having a high performance as a DSP (Digital Signal Processor) constituting the signal processing circuit, or to use the combination of a general DSP and an external memory and use all-pass filters
41
to
44
to enhance the stereo effect. The construction increases the price of the device and complicates the construction.
Accordingly, the present invention has an object to realize a stereo signal processing apparatus capable of effectively removing vocal signals without degradation of stereo effect, with a simple construction.
(1) The invention described in claim
1
is a stereo signal processing apparatus, which removes vocal signals included in right and left input signals, comprising: right filter means for extracting a right low-frequency signal and a right high-frequency signal from a right input signal; left filter means for extracting a left low-frequency signal and a left high-frequency signal from a left input signal; subtraction means for performing subtraction between the right input signal and the left input signal so as to generate a vocal removal signal; right addition means for adding the right low-frequency signal and the right high-frequency signal from the subtraction means to the vocal removal signal from the subtraction means so as to generate a right output signal; left addition means for adding the left low-frequency signal and the left high-frequency signal from the left filter means to the vocal removal signal from the subtraction means so as to generate a left output signal, wherein the right filter means and the left filter means comprise filters having different filter types.
In the stereo signal processing apparatus, filters respectively constituting the right filter means and the left filter means have filter types different from each other, and group-delay characteristics of the respective filters are different from each other. In the right output signal and the left output signal, different delay periods (phase differences) in accordance with frequency can be obtained.
Accordingly, a stereo signal processing apparatus capable of effectively removing vocal signals without degradation of stereo effect with a simple construction can realized.
(2) The invention described in claim
2
is the stereo signal processing apparatus according to claim
1
, wherein the right filter means comprises a right low-pass filter to extract the right low-frequency signal from the right input signal and a right high-pass filter to extract the right high-frequency signal from the right input signal, while the left filter means comprises a left high-pass filter to extract the left high-frequency signal from the left input signal and a left low-pass filter to extract the left low-frequency signal from the left input signal, and wherein the right low-pass filter and the left low-pass filter have filter types different from each other, and the right high-pass filter and the left high-pass filter have filter types different from each other.
In the stereo signal processing apparatus, filters respectively constituting the right low-pass filter and the left low-pass filter have filter types different from each other, and filters respectively constituting the right high-pass filter and the left high-pass filter have filter types different from each other. As group-delay characteristics of the respective filters are different from each other, in the right output signal and the left output signal, different delay periods (phase differences) in accordance with frequency can be obtained.
Accordingly, a stereo signal processing apparatus capable of effectively removing vocal signals without degradation of stereo effect with a simple construction can be realized.
(3) The invention described in claim
3
is the stereo signal processing apparatus according to claim
2
, wherein the filters having different types are Chebyshev type filters and Inverse Chebyshev type filters.
In the stereo signal processing apparatus, filters respectively constituting the right filter means and the left filter means have filter types different from each other (Chebyshev type and Inverse Chebyshev type), and group-delay characteristics of the respective filters are different from each other. In the right output signal and the left output signal, different group-delay periods (phase differences) in accordance with frequency can be obtained. Further, as the filter types are Chebyshev type and Inverse Chebyshev type, though the delay periods are different, the signal levels are approximately the same.
Accordingly, a stereo signal processing apparatus capable of effectively removing vocal signals without degradation of stereo effect with a simple construction can be realized.
Hereinbelow, an embodiment of the present invention will be described in detail. Note that in the present embodiment, description will be made using a stereo signal processing apparatus having a vocal cancel function to remove vocal signals included in left and right input signals as a particular example.
Next, a stereo signal processing apparatus
100
will be described with reference to FIG.
1
. In
FIG. 1
, the stereo signal processing apparatus
100
has a left low-pass filter
111
that extracts a left low-frequency signal and a left high-pass filter
112
that
Iwase Hiroshi
Kubota Takahiro
Faulk Devona E
Harvey Minsun Oh
Koninklijke Philips Electronics , N.V.
Schmitt Michael E.
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