JP5202021B2 - Audio signal conversion apparatus, audio signal conversion method, control program, and computer-readable recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a voice signal converter, making voice easy to listen to and heightening the feeling of being there. <P>SOLUTION: The voice signal converter 1 converts a right voice signal corresponding to a right channel and a left voice signal corresponding to a left channel to a central normal voice output signal corresponding to a center channel, a right voice output signal corresponding to the right channel and a left voice output signal corresponding to the left channel. A common component extracting part 3 extracts a common component contained in common in the right voice signal and the left voice signal, and an inverter part 5 generates the central voice output signal from the common component. A multiplication part 4 decreases a component calculated by subtracting the common component from the right voice signal and the left voice signal, respectively, and the inverter part 5 generates time signals of the right voice output signal and the left voice output signal. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an audio signal conversion apparatus, an audio signal conversion method, a control program, and a computer-readable recording medium that are provided in a television receiver or the like and emphasize audio such as a broadcast program.

  With the advancement of audio playback technology, users can stay at home by playing music at high volume with HiFi (High Fidelity) audio in a dedicated listening room and surround playback with a multi-channel home theater system. In the same way, you can enjoy the natural reverberation and realism of a concert hall or movie theater.

  On the other hand, usually, when viewing content such as television broadcasting, the viewer often watches at a low volume in a living room or kitchen. And even when watching TV with such a small volume, it is required that human voices such as dialogue can be accurately recognized and that a high sense of reality is required.

  However, when watching TV broadcasts with elderly people with weak hearing, etc., they will be watching at a louder volume than usual. For a person with hearing, it may be difficult to hear a person's voice and feel annoying. Therefore, when viewing at a louder volume than usual in a living room or the like, it is desirable that noise and sound effects are not emphasized in order to make it easier to hear the voice (human voice).

  Therefore, for the content being broadcast or being played, in order to enhance the sound (human voice) and suppress noise and music depending on the situation, or on the contrary, to improve the sense of reality It is necessary to emphasize music and sound effects.

  Patent Document 1 discloses a voice enhancement circuit that can be applied to a voice reproduction device such as a VTR or a tape recorder and can easily hear a human voice. The speech enhancement circuit described in Patent Document 1 includes a mid-range extraction amplifier that amplifies a mid-frequency component of a sum speech signal L + R of left and right audio signals L and R, and a mid-range extraction amplifier for left and right audio signals L and R. And left and right adders for adding the outputs.

  According to the speech enhancement circuit described in Patent Document 1, the left and right speech signals L and R are added to the summed component of the sum speech signal L + R, so that the left and right speech are reproduced. When listening, it becomes easier to hear the voice of the center person.

  Patent Document 2 discloses a vocal sound band emphasis circuit of an audio signal reproduction device. A vocal sound band emphasis circuit described in Patent Document 2 includes an in-phase component extraction circuit that extracts an in-phase component from left and right channel signals, a bandpass filter that extracts a vocal sound band from the in-phase component, and a predetermined frequency component from the vocal sound band. A notch filter that absorbs and attenuates, an automatic level control circuit that amplifies the output signal from the notch filter, a microcomputer that controls the amplification level, and the amplified output signal from the automatic level control circuit and the left and right channel signals are combined. And a first synthesis circuit and a second synthesis circuit that output the vocal sound band-emphasized left and right channel signals.

  The vocal sound band emphasis circuit of the audio signal reproduction device described in Patent Document 2 adds the left and right channel signals in the in-phase component extraction circuit. Then, a vocal sound band is extracted from the added signal by a bandpass filter, a predetermined (about 1 kHz) frequency component is absorbed and attenuated by a notch filter, and further amplified by automatic level control to be combined with left and right channel signals. It is.

  The voice enhancement circuit described in Patent Document 1 and the vocal sound band enhancement circuit described in Patent Document 2 are both vocal sound band components (middle band) of a signal obtained by adding two channel input signals of a right channel and a left channel. Component) is extracted, amplified, and added to the input signals of the left and right channels to enhance the human voice.

  By the way, Patent Document 3 discloses an audio apparatus that can widen a sound image without changing the sound quality when two-channel audio signals are subjected to predetermined processing and reproduced from a plurality of speakers including a surround speaker. It is disclosed. The audio apparatus described in Patent Document 3 has a sense of breadth by performing left and right channel spectrum analysis to extract left and right common spectral components, and generating front channel and surround channel waveforms based on the common spectral components. Get an acoustic space.

More specifically, the audio device described in Patent Document 3 calculates a spectral component (common component) that is commonly included in the left and right channels, and uses the common component to convert an input signal of two channels into four channels (front channel). And a surround channel) are calculated. Then, the spectrum of the input signal is separated into a front spectrum and a surround spectrum using a separation coefficient, and the waveforms of the front channel and the surround channel are obtained by inverse Fourier transforming them.
JP 5-115100 (published May 7, 1993) JP 2005-86462 (published March 31, 2005) JP-A-11-113097 (published on April 23, 1999)

  However, the configurations described in Patent Documents 1 and 2, that is, a vocal sound band component (middle band component) of a signal obtained by adding two channel input signals of the right channel and the left channel is extracted and amplified, In the configuration of adding to the input signal, all sounds included in the middle frequency band are emphasized, so noise and music other than human voice are also emphasized.

  This will be described in more detail as follows. When the common component of the spectrum R of the right channel signal and the spectrum L of the left channel signal is C, R = C + R ′ and L = C + L ′. R ′ is the difference between R and C, and L ′ is the difference between L and C. Here, the common component C is mainly a component corresponding to a human voice such as a vocal or speech localized at the center. R ′ and L ′ are components corresponding to ambient sounds (noise, background music, sound effects, etc.) other than human voices.

  In the configurations described in Patent Documents 1 and 2, the middle band component of the signal obtained by adding the right channel signal and the left channel signal is amplified. Here, the spectral component of the added signal is expressed as L + R (= 2C + L ′ + R ′), and in the middle range, the value increases due to amplification. In this case, not only the common component C but also R ′ and L ′ increase. In other words, not only the common component C corresponding to the human voice but also both R ′ and L ′ corresponding to the surrounding sound increase, so when the human voice is to be emphasized, the surrounding sound is also emphasized. Therefore, there is a problem that it is not always easy to hear a human voice.

  The present invention has been made in view of the above-mentioned problems, and a first object thereof is to suppress ambient sounds, that is, sounds other than human voices, in programs being broadcast or being played back. Thus, an object of the present invention is to provide an audio signal conversion device, an audio signal conversion method, a control program, and a computer-readable recording medium for realizing 3ch audio output that can make it easy to hear a human voice. . In addition, the second object of the present invention is to improve the sense of reality by emphasizing sound effects, background music, etc. by suppressing human voice in programs being broadcast or playing. An audio signal conversion device, an audio signal conversion method, a control program, and a computer-readable recording medium for realizing the above-described audio output are provided.

  In order to solve the above problems, an audio signal conversion apparatus according to the present invention converts a right audio signal corresponding to a right channel and a left audio signal corresponding to a left channel into a central audio output signal corresponding to a center channel, An audio signal conversion device for converting a right audio output signal corresponding to a channel and a left audio output signal corresponding to the left channel, wherein common components included in the right audio signal and the left audio signal are extracted. A common component extraction unit; a central audio output signal generation unit that generates the central audio output signal from the common component; and the right audio output signal by subtracting the common component from the right audio signal and the left audio signal, respectively. And left and right audio output signal generating means for generating the left audio output signal. That.

  According to the above configuration, the audio signal conversion device according to the present invention converts the right audio signal corresponding to the right channel and the left audio signal corresponding to the left channel into the central audio output signal corresponding to the center channel and the right channel. The corresponding right audio output signal and the left audio output signal corresponding to the left channel are converted. That is, the audio signal conversion apparatus according to the present invention converts a 2-channel audio input signal into a 3-channel audio output signal. Examples of the two-channel audio input signal include a stereo audio signal in television broadcasting.

  Further, according to the above configuration, the common component extraction unit extracts a common component included in common in the right audio signal and the left audio signal. The common component is a spectral component included in common in the spectrum of the right audio signal and the spectrum of the left audio signal. That is, the common component is obtained by extracting the spectrum component having the smaller absolute value from the spectrum of the right audio signal and the spectrum of the left audio signal in all frequency bands.

  Moreover, according to said structure, a center audio | voice output signal production | generation means produces | generates the said center audio | voice output signal from the said common component. The central audio output signal generation means can convert the common component, which is spectral information in the frequency domain, into a central audio output signal that is a signal waveform in the time domain, for example, by fast Fourier transform (FFT). The central audio output signal generation means may be configured to generate a central audio output signal by a discrete Fourier transform (DFT), a modified discrete cosine transform (MDCT), or the like. There is no limitation.

  Further, according to the above configuration, the left and right audio output signal generating means generates the right audio output signal and the left audio output signal by subtracting the common component from the right audio signal and the left audio signal, respectively. . The left and right audio output signal generation means can generate the right audio output signal by performing, for example, FFT on the spectrum obtained by subtracting the common component from the spectrum of the right audio signal. Similarly, the left and right audio output signal generating means can generate the left audio output signal by subtracting the common component from the left audio signal.

  Thus, according to the audio signal conversion device of the present invention, an audio signal (corresponding to a common component) mainly representing a human voice is obtained from a two-channel audio signal in which a human voice and surrounding sounds are mixed. It is possible to generate a three-channel audio signal including one channel and two channels of an audio signal representing surrounding sounds (corresponding to a component obtained by subtracting a common component from left and right spectral components). That is, it is possible to separate a voice signal of a human voice and a voice signal of surrounding sounds. Here, ambient sounds refer to sounds other than human voices, such as sound effects in dramas, sports broadcast cheers, background music, home and natural noise.

  Therefore, it is possible to independently adjust an audio signal representing a human voice and an audio signal representing an ambient sound. That is, it becomes possible to adjust the level balance between an audio signal representing a human voice and an audio signal representing surrounding sounds.

  The audio signal conversion method according to the present invention includes a right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, a right audio output signal corresponding to the right channel, And a method of converting an audio signal into a left audio output signal corresponding to the left channel, the common component extracting step for extracting a common component common to the right audio signal and the left audio signal, and the common component Generating a central audio output signal from the central audio output signal and subtracting the common component from the right audio signal and the left audio signal to generate the right audio output signal and the left audio output signal, respectively. And a left and right audio output signal generation step.

  According to said structure, there exists an effect similar to the audio | voice signal converter concerning this invention.

  The audio signal conversion device according to the present invention preferably further includes left and right component reduction means for reducing the values of all components of the right audio output signal and the left audio output signal.

  According to said structure, a left-right component reduction means reduces the value of all the components of a right audio | voice output signal and a left audio | voice output signal. That is, the left / right component reducing means reduces and outputs the right audio signal and left audio signal after the subtraction. Here, the left / right component reducing means may be configured to perform, for example, inverse FFT on a product obtained by multiplying the spectral components of the right audio signal and the left audio signal after the subtraction by a multiplier less than 1. There may be a configuration in which the spectral components of the right audio signal and the left audio signal after subtraction are subjected to inverse FFT or the like to be converted into an audio signal representing a time waveform and then attenuated by an attenuator, and there is no particular limitation.

  As a result, of the three channel output signals, the central audio output signal is output to the center channel without reducing the values of all components, and the right audio output signal and the left audio output signal are all component values. Are reduced and output to the right and left channels.

  Accordingly, the ambient sound represented by the right audio output signal and the left audio output signal is reduced, and the human voice represented by the central audio output signal is emphasized, so that the program is viewed at a particularly low volume. In some cases, it is possible to improve the ease of listening to a human voice.

  In the audio signal conversion apparatus according to the present invention, it is preferable that the left / right component reduction means sets the values of all components of the right audio output signal and the left audio output signal to zero.

  According to the above configuration, the left / right component reduction unit sets the values of all components of the right audio output signal to zero. The left and right component reducing means, for example, sets the right audio output signal to 0 by multiplying all components obtained by subtracting the common component from the spectrum of the right audio signal by 0 as a multiplier. Similarly, the left / right component reducing means sets the values of all components of the right audio output signal to zero.

  As a result, of the three channel output signals, the central audio output signal is output to the center channel without reducing the values of all components, and the right audio output signal and the left audio output signal are all component values. Is output as zero. That is, the magnitude of the audio output signal output to the right channel and the left channel is zero.

  Accordingly, the sound is output based only on the sound signal generated mainly from the common component including the human voice, and the surrounding sound (sound other than the human voice such as noise) is not output. Therefore, for example, even when an elderly person whose hearing has declined increases the volume, the surrounding sounds such as noise are not loud and only the human voice is emphasized. You don't feel much annoyance.

  The audio signal conversion apparatus according to the present invention preferably further comprises central audio output signal amplifying means for amplifying the values of all components of the central audio output signal.

  According to said structure, a center audio | voice output signal amplification means amplifies the value of all the components of a center audio | voice output signal. The central audio output signal amplifying means may be configured to amplify the central audio output signal by multiplying the spectrum data in the frequency domain, or may be configured to directly amplify the time waveform in the time domain. There is no limitation.

  Thereby, since the voice of the person represented by the central audio output signal can be emphasized, the ease of listening to the voice of the person can be improved. In addition, since the values of all the components can be amplified, it is possible to easily improve the human voice.

  The audio signal conversion apparatus according to the present invention preferably further includes a central level adjusting means for adjusting the value of the central audio output signal.

  The center level adjusting means is configured as a parametric equalizer, for example. Alternatively, the center level adjusting means may be composed of not only a parametric equalizer but also a filter and an amplifier that cannot adjust the center frequency, Q, and gain. According to the center level adjusting means, only a component in a specific frequency band included in the center audio output signal can be amplified.

  Thereby, since the voice of the person represented by the central audio output signal can be emphasized, the ease of listening to the voice of the person can be improved. In addition, since the value of the central audio output signal can be directly adjusted, finer adjustment is possible.

  In the audio signal conversion apparatus according to the present invention, it is preferable that the central level adjusting means adjusts the value so that the gain of the central audio output signal becomes maximum at approximately 2 kHz. Thereby, it becomes possible to emphasize a human voice more.

  The audio signal conversion apparatus according to the present invention preferably further comprises a central audio output signal reducing means for reducing the values of all components of the central audio output signal.

  According to said structure, a center audio | voice output signal reduction means reduces the value of all the components of a center audio | voice output signal. That is, the central audio output signal reducing means reduces the central audio output signal and outputs it. Here, the central audio output signal reduction unit may be configured to perform inverse FFT or the like on a product obtained by multiplying the spectrum component of the common component by a multiplier less than 1, for example. Or after performing inverse FFT etc. on a spectrum component and converting it into the audio | voice signal showing a time waveform, the structure attenuate | damped by an attenuator may be sufficient, and it does not specifically limit.

  As a result, among the three-channel output signals, the central audio output signal is reduced in all component values and output to the center channel, and the right audio output signal and the left audio output signal are reduced in all component values. Without being output to the right channel and the left channel.

  Therefore, since the human voice represented by the central audio output signal is reduced, the right audio output signal and the surrounding sound represented by the left audio output signal are emphasized, and the program is viewed at a particularly low volume. In some cases, a sense of reality can be improved.

  In the audio signal conversion apparatus according to the present invention, it is preferable that the central audio output signal reducing means sets the values of all components of the central audio output signal to zero.

  According to said structure, a center audio | voice output signal reduction means makes the value of all the components of a center audio | voice output signal zero. For example, the central audio output signal reducing unit multiplies the common component by 0 to set the values of all the common components to 0.

  As a result, among the three channel output signals, the central audio output signal is output to the center channel with all component values being zero, and the right audio output signal and the left audio output signal are all component values. Output without being reduced. That is, the magnitude of the audio output signal output to the center channel is zero.

  Therefore, only ambient sounds (noise and other sounds other than human voice) are output, and no sound based on the audio signal generated from the common component that mainly contains human voice is output, further enhancing the sense of reality. It becomes possible to make it.

  The audio signal conversion device according to the present invention preferably further includes left and right component amplifying means for amplifying the values of all components of the right audio output signal and the left audio output signal.

According to said structure, a right-and-left component amplification means amplifies the value of all the components of the said right audio | voice output signal and the said left audio | voice output signal, respectively. The left and right component amplifying means may be configured to amplify the right audio output signal and the left audio output signal by multiplying spectrum data in the frequency domain, or to directly amplify the time waveform in the time domain. There is no particular limitation.
Since the surrounding sound represented by the left audio output signal or the right audio output signal can be emphasized, the sense of reality can be improved. In addition, since the values of all the components can be amplified, the sense of reality can be easily improved.

  The audio signal converter according to the present invention preferably further comprises level adjusting means for adjusting the value of at least one of the right audio output signal and the left audio output signal.

  The left / right level adjusting means is configured as a parametric equalizer, for example. Alternatively, the left / right level adjusting means may be configured not only by a parametric equalizer but also by a filter and an amplifier that cannot adjust the center frequency, Q, and gain, and is not particularly limited. According to the left / right level adjusting means, it is possible to amplify only a component of a specific frequency band included in the right audio output signal and the left audio output signal.

  As a result, the ambient sound represented by the left audio output signal or the right audio output signal can be emphasized, so that the sense of reality can be improved. In addition, since the value of the left audio output signal or the right audio output signal can be directly adjusted, finer adjustment is possible.

  In the audio signal converter according to the present invention, the left / right level adjusting means adjusts the value so that at least one gain of the right audio output signal and the left audio output signal is minimized at approximately 4 kHz. Is preferred.

  Thereby, it is possible to further improve the sense of reality.

  The audio signal converter according to the present invention includes a right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, a right audio output signal corresponding to the right channel, And an audio signal conversion device for converting into a left audio output signal corresponding to the left channel, the right audio high frequency signal of the high frequency component of the right audio signal and the left audio high frequency of the high frequency component of the left audio signal High-frequency signal generating means for generating a signal, low-frequency signal generating means for generating a right-side audio low-frequency signal of a low-frequency component of the right-side audio signal and a left-side audio low-frequency signal of a low-frequency component of the left audio signal; A common component extraction means for extracting a high frequency common component commonly included in the right audio high frequency signal and the left audio high frequency signal; and the central audio output from the high frequency common component. Common signal generating means for generating a signal, subtracting the high frequency common component from the right audio high frequency signal and the left audio high frequency signal, respectively, and adding the right audio low frequency to the right audio high frequency signal after the subtraction Audio output signal generation means for generating the right audio output signal and the left audio output signal by adding the signal and adding the left audio low frequency signal to the left audio high frequency signal after the subtraction. It is characterized by having.

  According to the above configuration, the audio signal conversion device converts a 2-channel audio input signal into a 3-channel audio output signal. The high frequency signal generating means generates a right audio high frequency signal that is a high frequency component of the right audio signal and a left audio high frequency signal that is a high frequency component of the left audio signal. Further, the low frequency signal generating means generates a right audio low frequency signal that is a low frequency component of the right audio signal and a left audio low frequency signal that is a low frequency component of the left audio signal. Each of the high-frequency signal generating means and the low-frequency signal generating means may have a filter configuration capable of extracting a high-frequency signal and a low-frequency signal, or either of the high-frequency signal generating means and the low-frequency signal generating means. One may be a filter, and the other may be configured to subtract the signal output by the filter from the original signal, and is not particularly limited.

  Further, according to the above configuration, the common component extraction unit extracts a high frequency common component included in common in the right audio high frequency signal and the left audio high frequency signal. Here, since the high frequency audio signal does not include low frequency audio and audio other than the human voice is excluded, the high frequency common component is a component more precisely corresponding to the human voice. Only is extracted. Note that the cutoff frequency in the high-frequency signal generating means and the low-frequency signal generating means is not particularly limited as long as it is set according to the required accuracy. Then, the common signal generating means generates the central audio output signal from the high frequency common component corresponding to the human voice by, for example, FFT.

  Further, according to the above configuration, the audio output signal generation means subtracts the high frequency common component from the right audio high frequency signal and the left audio high frequency signal, respectively. That is, components corresponding to sounds other than the human voice, that is, surrounding sounds, are calculated from the right audio high frequency signal and the left audio high frequency signal. Then, the right audio low-frequency signal is added to the right audio high-frequency signal after the subtraction, and the left audio low-frequency signal is added to the left audio high-frequency signal after the subtraction. The right audio output signal and the left audio output signal corresponding to the sound are generated.

  Thereby, according to the audio | voice signal converter which concerns on this invention, it becomes possible to isolate | separate more strictly the component showing a human voice, and components other than a human voice. Therefore, a sound output signal corresponding to a human voice and a sound output signal corresponding to a surrounding sound are generated more accurately. As a result, the level balance between the sound output signal corresponding to the human voice and the sound output signal corresponding to the surrounding sound can be changed more strictly. That is, it is possible to perform reproduction that emphasizes the voice of a person accurately or emphasizes a voice other than a person's voice (realism).

  The audio signal conversion method according to the present invention includes a right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, a right audio output signal corresponding to the right channel, And an audio signal conversion method for converting into a left audio output signal corresponding to the left channel, wherein the right audio high frequency signal of the high frequency component of the right audio signal and the left audio high frequency of the high frequency component of the left audio signal A high frequency signal generating step for generating a signal, a low frequency signal generating step for generating a right audio low frequency signal of a low frequency component of the right audio signal and a left audio low frequency signal of a low frequency component of the left audio signal, A common component extraction step for extracting a high-frequency common component commonly included in the right audio high-frequency signal and the left audio high-frequency signal; A common signal generating step for generating a central audio output signal; and subtracting the high frequency common component from the right audio high frequency signal and the left audio high frequency signal, respectively, and adding the right audio high frequency signal to the right audio high frequency signal after the subtraction. An audio output signal generating step for generating the right audio output signal and the left audio output signal by adding an audio low frequency signal and adding the left audio low frequency signal to the left audio high frequency signal after the subtraction It is characterized by including.

  According to said structure, there exists an effect similar to the audio | voice signal converter concerning this invention.

  In the audio signal conversion device according to the present invention, the low-frequency signal generation means performs low-pass filtering on the right audio signal and the left audio signal, and outputs the right audio low-frequency signal and the left audio low-frequency signal. The high frequency signal generating means generates the right audio low frequency signal from the delayed right audio signal by giving the right audio signal and the left audio signal the same delay amount as the low frequency signal generating means. The left audio low-frequency signal is preferably subtracted from the delayed left audio signal to generate the right audio high-frequency signal and the left audio high-frequency signal.

  According to said structure, the said low-pass signal production | generation means carries out the low-pass filter of the said right audio | voice signal and the said left audio | voice signal. On the other hand, the high frequency signal generating means delays the right audio signal and the left audio signal by the same delay time as the low frequency signal generating means. That is, the phase of the input audio signal and the audio signal that has passed through the low-frequency signal generating means are matched. Then, the right audio low frequency signal is subtracted from the delayed right audio signal, the left audio low frequency signal is subtracted from the delayed left audio signal, and the right audio high frequency signal and the left audio high frequency signal are subtracted. Is generated.

  As a result, the high-frequency signal generating means generates a high-frequency signal without having the function of high-frequency filtering, and thus an audio signal conversion device with low power consumption can be configured using simple components.

  Moreover, in the audio signal conversion device according to the present invention, it is preferable that the cutoff frequency of the low-pass filtering in the low-frequency signal generating means is approximately 100 Hz.

  As a result, it is possible to more precisely extract a component corresponding to a human voice as a high-frequency common component, so that the human voice can be more accurately emphasized.

  In the audio signal converter according to the present invention, the high-frequency signal generation means generates the right audio high-frequency signal and the left audio high-frequency signal by high-pass filtering the right audio signal and the left audio signal. The low frequency signal generating means gives the right audio signal and the left audio signal the same delay amount as the high frequency signal generating means, and subtracts the right audio high frequency signal from the delayed right audio signal. Preferably, the left audio high frequency signal is subtracted from the delayed left audio signal to generate the right audio low frequency signal and the left audio low frequency signal.

  According to said structure, the said high-pass signal production | generation means carries out the high-pass filter of the said right audio | voice signal and the said left audio | voice signal. On the other hand, the low frequency signal generating means delays the right audio signal and the left audio signal by the same delay time as the low frequency signal generating means. That is, the phase of the input audio signal and the audio signal that has passed through the high frequency signal generating means are matched. Then, the right audio high frequency signal is subtracted from the delayed right audio signal, the left audio high frequency signal is subtracted from the delayed left audio signal, and the right audio low frequency signal and the left audio low frequency signal are subtracted. Is generated.

  As a result, the low-frequency signal generating means generates a low-frequency signal without having a low-pass filtering function, and therefore, an audio signal conversion device with low power consumption can be configured using simple components.

  In the audio signal conversion device according to the present invention, it is preferable that the cut-off frequency of high-pass filtering in the high-frequency signal generating means is approximately 100 Hz.

  As a result, it is possible to extract a component corresponding to the human voice more precisely as the low-frequency common component, so that the human voice can be more accurately emphasized.

  In the audio signal conversion device according to the present invention, the low-frequency signal generation means performs low-pass filtering on the right audio signal and the left audio signal, and outputs the right audio low-frequency signal and the left audio low-frequency signal. Preferably, the high frequency signal generating means generates the right audio high frequency signal and the left audio high frequency signal by high-pass filtering the right audio signal and the left audio signal.

  As a result, the high-frequency signal generating means has a high-pass filtering function, and the low-frequency signal generating means has a low-pass filtering function. A conversion device can be configured.

  In the audio signal converter according to the present invention, both the low-pass filtering cutoff frequency in the low-frequency signal generating means and the high-pass filtering cutoff frequency in the high-frequency signal generating means are both approximately 100 Hz. preferable.

  As a result, it is possible to more precisely extract a component corresponding to a human voice as a high-frequency common component, so that the human voice can be more accurately emphasized.

  In the audio signal conversion apparatus according to the present invention, it is preferable that the delay amount of the low-frequency signal generation unit is equal to the delay amount of the high-frequency signal generation unit. That is, it is preferable to match the phase of the input audio signal and the audio signal that has passed through the low-frequency signal generating means.

  Note that the audio signal conversion apparatus may be realized by a computer. In this case, a control program for realizing the audio signal conversion apparatus in the computer by operating the computer as each of the above means and a computer-readable recording medium on which the control program is recorded also fall within the scope of the present invention.

  The audio signal converter according to the present invention includes a right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, a right audio output signal corresponding to the right channel, And an audio signal converter for converting into a left audio output signal corresponding to the left channel, the common component extracting means for extracting a common component common to the right audio signal and the left audio signal, and the common component The central audio output signal generating means for generating the central audio output signal from, and the right audio output signal and the left audio output signal are generated by subtracting the common component from the right audio signal and the left audio signal, respectively. Left and right audio output signal generating means.

  Therefore, the audio signal conversion device according to the present invention can independently adjust an audio signal representing a human voice and an audio signal representing an ambient sound, and represents an audio signal representing a human voice and an ambient sound. Since the level balance with the audio signal can be adjusted, the human voice can be emphasized to make it easy to hear.

  The audio signal conversion apparatus according to the present invention also includes a right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, and a right audio output corresponding to the right channel. An audio signal conversion device for converting a signal and a left audio output signal corresponding to the left channel, wherein the right audio high frequency signal of the high frequency component of the right audio signal and the left audio of the high frequency component of the left audio signal High frequency signal generating means for generating a high frequency signal, and low frequency signal generating means for generating a right audio low frequency signal of a low frequency component of the right audio signal and a left audio low frequency signal of a low frequency component of the left audio signal A common component extraction means for extracting a high frequency common component that is commonly included in the right audio high frequency signal and the left audio high frequency signal, and the center from the high frequency common component. A common signal generating means for generating a voice output signal; and subtracting the high frequency common component from the right audio high frequency signal and the left audio high frequency signal, respectively, and adding the right audio to the right audio high frequency signal after the subtraction. Audio output signal generating means for adding the low frequency signal and adding the left audio low frequency signal to the left audio high frequency signal after the subtraction to generate the right audio output signal and the left audio output signal; It has.

  Therefore, according to the audio signal conversion device of the present invention, it is possible to more strictly separate a component representing a human voice and a component other than a human voice, and more accurately deal with a human voice. Since the level balance between the audio output signal and the audio output signal corresponding to the surrounding sound can be changed, the accuracy when emphasizing a human voice or emphasizing a voice other than a human voice (sense of presence) Can be increased.

[Embodiment 1]
(Audio signal converter 1)
FIG. 1 is a block diagram showing a configuration of an audio signal conversion apparatus 1 according to the present invention. An audio signal converter 1 according to the present invention includes a spectrum converter 2, a common component extractor 3 (common component extractor), a multiplier 4, an inverse converter 5, a parametric equalizer (PEQ) unit 6, and a subtractor. 7, 8, input terminal 12, and output terminal 13.

  The spectrum conversion unit 2 includes spectrum conversion units 2a and 2b. The multiplying unit 4 includes a multiplying unit 4a (left / right component reducing unit, left / right component amplifying unit), a multiplying unit 4b (central audio output signal amplifying unit, central audio output signal reducing unit), and a multiplying unit 4c (left / right component reducing unit, left and right component). Component amplification means). The inverse conversion unit 5 includes an inverse conversion unit 5a (left / right audio output signal generation unit), an inverse conversion unit 5b (central audio output signal generation unit), and an inverse conversion unit 5c (left / right audio output signal generation unit). The The PEQ unit 6 includes a PEQ unit 6a (left / right level adjusting unit), a PEQ unit 6b (center level adjusting unit), and a PEQ unit 6c (left / right level adjusting unit). The input terminal 12 includes input terminals 12a and 12b. The output terminal 13 includes output terminals 13a, 13b, and 13c.

  The audio signal converter 1 is an apparatus that is mounted on a television receiver or the like and emphasizes the audio of a program being broadcast. Here, the voice refers to a human voice such as dialogue or vocals, and is distinguished from sounds other than the human voice (for example, ambient noise, BGM, sound effects, etc.). That is, the audio signal conversion apparatus 1 is an apparatus that emphasizes the voice of a person in a broadcast program. In addition, when expressed as an audio signal, it indicates a signal that represents all sounds including audio and non-audio sounds in the program.

  In the present embodiment, the audio signal converter 1 receives a 2-channel audio signal digitally encoded by PCM (Pulse Code Modulation). Normally, in stereo broadcasting or the like, different audio signals are supplied to the left and right speakers provided in the television based on the input two-channel audio signals, and different audio is output from the left and right speakers.

  In the following, audio signals supplied to the left and right speakers in normal stereo broadcasting are respectively a left audio signal (left audio signal corresponding to the left channel) and a right audio signal (right audio signal corresponding to the right channel). Call. The right audio signal and the left audio signal are input to the audio signal converter 1 via the input terminal 12a and the input terminal 12b, respectively.

  In the present embodiment, the audio signal conversion apparatus 1 outputs audio via the left, right, and center speakers based on the two-channel audio signals of the right audio signal and the left audio signal. To do. That is, the audio signal converter 1 is configured to convert the input 2-channel audio signals into 3-channel audio output signals of the left channel, the right channel, and the center channel, and supply them to each speaker.

  Hereinafter, the speech enhancement process in the speech signal conversion apparatus 1 shown in FIG. 1 will be described.

  The spectrum conversion unit 2 performs various processes for calculating the spectrum of the audio signal of each channel. The spectrum conversion unit 2 will be described in detail as follows.

  First, the spectrum conversion unit 2a divides the right audio signal input via the input terminal 12a into 1024 samples per frame. When the sampling frequency of the audio signal is 44.1 kHz, the time per frame is 23 ms (= (1 ÷ 44100) × 1024).

  Next, the spectrum converter 2a multiplies the frame-divided audio signal by a window function such as a Hanning window. By applying the window function, it is possible to reduce the frequency analysis error for the frame-divided audio signal. In the present embodiment, a Hanning window is used as the window function, but a window function other than the Hanning window may be used, and is not particularly limited.

  Next, the spectrum transform unit 2a performs fast Fourier transform (FFT) on the speech signal to which the window function is applied for each frame, and converts the time domain speech signal into frequency domain data, that is, The spectrum is converted into a spectrum (hereinafter referred to as a right audio signal spectrum) and output to the common component extraction unit 3 and the subtractor 7.

  Here, assuming that the right audio signal is xr (n), the right audio signal spectrum is XR (k), and the window function w (n), the spectrum conversion unit 2a calculates the right audio signal spectrum XR (k) by the following equation. To do. Note that n is a sampling number. In the present embodiment, as described above, 1024 samples are included in one frame, and the spectrum conversion unit 2a performs 1024-point FFT.

  In this embodiment, FFT is performed to calculate a frequency spectrum from an audio signal. However, a configuration in which a frequency spectrum is calculated by a modified discrete cosine transform (MDCT) may be used. Not done.

  Further, the spectrum conversion unit 2b calculates the spectrum of the left audio signal input through the input terminal 12b (hereinafter referred to as the left audio signal spectrum) by the same processing as the spectrum conversion unit 2a, and extracts the common component. Output to the unit 3 and the subtracter 8. Here, assuming that the left audio signal is xl (n), the left audio signal spectrum is XL (k), and the window function w (n), the spectrum conversion unit 2a calculates the left audio signal spectrum XL (k) by the following equation. To do.

  The common component extraction unit 3 extracts a common component of the right audio signal spectrum and the left audio signal spectrum. 2A and 2B are diagrams for explaining the common component. FIG. 2A is a diagram illustrating the common component of the right audio signal spectrum (R channel) and the left audio signal spectrum (L channel), and FIG. It is a figure which shows only a common component.

  The common component extraction unit 3 calculates the common component spectrum C (k) by C (k) = MIN (XL (k), XR (k)), and outputs it to the subtracters 7 and 8 and the multiplication unit 4b. That is, the common component extraction unit 3 extracts the smaller spectrum of XR (k) and XL (k) as a common component.

  As described above, the audio signal conversion apparatus 1 of the present invention receives a 2-channel input signal in a stereo broadcast program or the like. In a general stereo broadcast program, sound is recorded by a one-channel microphone for recording sound, and BGM and sound effects other than vocals are recorded in advance by two microphones (stereo) on the left and right. When a program recorded by these three microphones is broadcast in stereo on 2 channels, the 3 channel signal is downmixed to 2 channels. That is, a voice signal of a human voice recorded by a one-channel microphone for recording a sound is mixed with a surrounding sound signal recorded by two left and right microphones, and a two-channel voice signal is transmitted. become. At this time, the ratio at which the human voice signal and the surrounding sound signal are mixed is set in the broadcasting station. In this case, the right audio signal is an audio signal obtained by mixing audio recorded by the right microphone and the 1-channel microphone for recording audio. The left audio signal is an audio signal obtained by mixing audio recorded by the left microphone and a one-channel microphone for recording audio. Therefore, also in this case, an audio signal representing a human voice is included in common with the left audio signal and the right audio signal. For music including vocals, vocals are also recorded by a 1-channel microphone for recording audio, and instrument sounds are recorded by two microphones (stereo) on the left and right, and then downmixed to 2 channels by a recording engineer. ing. The two-channel audio signal downmixed using the background as described above is roughly restored to the three channels before the original downmix. Here, “approximate” means that the signals recorded in advance by the two left and right microphones (stereo) have a common component and are not completely restored.

  That is, the common component extraction unit 3 extracts, as a common component, a component of an audio signal mainly representing a human voice that is included in common in the right audio signal and the left audio signal.

  The subtractor 7 subtracts the common component spectrum C (k) output from the common component extraction unit 3 from the right audio signal spectrum XR (k) output from the spectrum conversion unit 2a to obtain the right component spectrum XR ′ ( k) is calculated and output to the multiplication unit 4a. That is, the subtractor 7 performs an operation of XR ′ (k) = XR (k) −C (k).

  The subtracter 8 subtracts the common component spectrum C (k) output from the common component extraction unit 3 from the left audio signal spectrum XL (k) output from the spectrum conversion unit 2b to obtain the left component spectrum XL ′ ( k) is calculated and output to the multiplier 4c. That is, the subtracter 8 performs the calculation of XL ′ (k) = XL (k) −C (k).

  FIG. 3 is a diagram showing the remaining components obtained by removing the common component spectrum from the right audio signal spectrum (R channel) and the left audio signal spectrum (L channel). FIG. 3A shows the left component spectrum XL ′ (k (B) is a diagram showing the right component spectrum XR ′ (k).

  Here, the left component spectrum XL ′ (k) and the right component spectrum XR ′ (k) are components mainly representing sounds other than the human voice (background sounds such as BGM, sound effects, and noise).

  The multiplier 4a multiplies XR ′ (k) output from the subtractor 7 by a multiplier M1 (0 ≦ M1 ≦ 1) to calculate XR ″ (k) (= M1 × XR ′ (k)), and the inverse The multiplication unit 4b multiplies C (k) output from the common component extraction unit 3 by a multiplier M2 (0 ≦ M2 ≦ 1) to obtain C ″ (k) (= M2 × C). (K)) is calculated and output to the inverse transform unit 5b. Further, the multiplier 4c multiplies XL ′ (k) output from the subtractor 8 by the multiplier M1 to calculate XL ″ (k) (= M1 × XL ′ (k)), and outputs the result to the inverse converter 5c. To do.

  Hereinafter, XR ″ (k), C ″ (k), and XL ″ (k) are referred to as a right component output spectrum, a common component output spectrum, and a left component output spectrum, respectively.

  FIG. 4 is a diagram showing the right component output spectrum XL ″ (k) and the left component output spectrum XL ″ (k). FIG. 4A is a diagram in which the right component spectrum shown in FIG. FIG. 4B is a diagram illustrating the right component output spectrum XR ″ (k) calculated in FIG. 3B, and FIG. 3B is a diagram illustrating the left component output spectrum XL ″ (k) calculated by multiplying the left component spectrum illustrated in FIG. ).

  The left component output spectrum XL ″ (k) and the right component output spectrum XR ″ (k) are components of an audio signal representing surrounding sounds (sounds other than human voice).

  The inverse transform unit 5a converts the right component output spectrum XR ″ (k), which is frequency domain information, into a time domain signal waveform by inverse FFT and outputs it to the right speaker (right side corresponding to the right channel). (Sound output signal) is generated and output to the PEQ unit 6a, and the inverse transform unit 5b performs the same processing as the inverse transform unit 5a, and outputs the common component output spectrum C ″ (k), which is information in the frequency domain. An audio output signal (a central audio output signal corresponding to the central channel) that is converted to a signal waveform in the time domain by inverse FFT and output to the central speaker is generated and output to the PEQ unit 6b. The inverse transform unit 5c performs the same processing as the inverse transform unit 5c, converts the left component output spectrum XL ″ (k), which is frequency domain information, into a signal waveform in the time domain by inverse FFT and outputs the signal waveform to the left speaker. Audio output signal (left audio output signal corresponding to the left channel) is generated and output to the PEQ unit 6c.

  When the time waveform is FFT-converted into the frequency domain, the above common component extraction is performed, and then the signal waveform on the time axis is restored again by inverse FFT, the distortion (harmonic component) generated at the joint of the frames is reduced. In order to reduce this, a window function is applied to smoothly bring the beginning and end portions of the time waveform before the FFT processing close to zero. In this embodiment, when the frame cut-out time is t, the cut-out time is shifted by 1 / 2t, the Hann window function is applied to each cut-out waveform, and the data after inverse FFT overlaps by 1 / 2t before and after. To add and return to a continuous time waveform. In the present embodiment, the overlap of 1 / 2t is performed in accordance with the shape of the Hanning window, but the overlap length may be set according to the shape of the window, and is not particularly limited.

  When it is desired to enhance the sense of reality, that is, when it is desired to enhance surrounding sounds, the PEQ unit 6a applies a parametric equalizer having the characteristic of an equal loudness curve to the right channel audio output signal output from the inverse transform unit 5a. Output to the right channel speaker via the output terminal 13a. Alternatively, the presence can be enhanced by multiplying the subtracted right audio signal by a multiplier larger than 1 in the multiplication unit 4a.

  FIG. 5 is a diagram showing a frequency characteristic example of a parametric equalizer that emphasizes a human voice band having a peak of about 2 kHz, and FIG. 6 is a parametric having a minimum value of about 4 kHz created based on an equal loudness curve. It is a figure which shows the frequency characteristic example of an equalizer. FIG. 7 is a diagram showing an equal loudness curve measured by Robinson et al.

  When it is desired to make the human voice easy to hear, that is, when the human voice is to be emphasized, the PEQ unit 6b has a peak at 2 kHz as shown in FIG. 5 with respect to the central channel audio output signal output from the inverse transform unit 5b. A parametric equalizer for emphasizing the voice band is applied and output to the speaker of the central channel via the output terminal 13b. Alternatively, the multiplication unit 4b can easily hear a human voice by multiplying the extracted common component by a multiplier larger than 1.

  In addition, as in the case of the PEQ unit 6a, the PEQ unit 6c applies the left channel audio output signal output from the inverse conversion unit 5c to the audio output signal of FIG. In this manner, a parametric equalizer having the characteristic of an equal loudness curve is applied and output to the left channel speaker via the output terminal 13c. Alternatively, the presence can be enhanced by multiplying the subtracted left audio signal by a multiplier greater than 1 in the multiplication unit 4c.

  Here, the loudness is a numerical value representing how a human sound is perceived as a sensation amount. Loudness is distinguished from sound pressure, which is a physical quantity representing the intensity of sound. In general, human hearing is most sensitive in the vicinity of 4 kHz (such as a baby cry), and the sensitivity decreases as the frequency becomes lower or higher. Therefore, the actual physical sound pressure level is different even when the sounds are heard at the same volume. Also, even if the sound pressure is doubled, a person does not feel that the loudness has doubled. The equal loudness curve is a plot of the sound pressures of other frequencies that have been heard with a loudness equal to the reference sound of 1 kHz, and is a substantially V-shaped curve having a minimum value near 4 kHz as shown in FIG. . Further, since the characteristic of the equal loudness curve approaches flat as the sound pressure increases, it is preferable to change the characteristic of the parametric equalizer shown in FIG. 6 according to the input level of the input audio signal.

  The parametric equalizer is an equalizer that can adjust the gain (including 1 or less) of the pass level for each band by dividing the audio frequency band into several parts, and includes “center frequency”, “gain”, “Q”. With the three parameters (Quality factor), the center frequency and frequency bandwidth of the passband can be independently changed and adjusted. Here, the Q value is represented by a ratio Q = ω0 / Δω of a frequency bandwidth (Δω) attenuated or amplified by 3 dB from the level of the center frequency and the center frequency ω0.

  That is, in the PEQ section 6a and the PEQ section 6c described above, the "center frequency", "gain", and "gain" are shown so as to show the characteristic of the equal loudness curve, that is, the substantially V-shaped characteristic at which the passing level is minimum at 4 kHz. An equalizer in which “Q (Quality factor)” is set is applied.

  In the present embodiment, the PEQ unit 6b is used as means for enhancing the voice band having a peak of 2 kHz, but may be realized using a combination of a filter and an amplifier other than the PEQ. Moreover, the multiplication unit 4b may be used for the spectrum after FFT to directly weight the spectrum at 2 kHz. Further, although the PEQ unit 6a and the PEQ unit 6c are used as means for enhancing surrounding sounds, the PEQ unit 6a and the PEQ unit 6c may be implemented using a combination of a filter and an amplifier other than the PEQ. Further, the characteristics of the equal loudness curve may be weighted to the spectrum after the FFT using the multiplier 4a and the multiplier 4c, and the spectrum is not particularly limited.

  In the audio signal conversion apparatus 1 according to the present invention, the voice can be enhanced by reducing the multiplier M1 multiplied by the left component spectrum XL ′ (k) and the right component spectrum XR ′ (k). For example, when a common component spectrum is generated by multiplying the common component spectrum by 1, and the left component output spectrum and the right component output spectrum are reduced by multiplying the right component spectrum and the left component spectrum by a multiplier of less than 1, The size of the audio output signal corresponding to the human voice does not change and only the audio output signal corresponding to the surrounding sound is reduced, so it is generated from the common component output spectrum, left component output spectrum, and right component output spectrum. The voice output from the speaker based on each voice output signal is emphasized by a human voice. Further, if the right component spectrum and the left component spectrum are multiplied by 0 as a multiplier, the human voice can be more emphasized.

  On the other hand, if the multiplier M1 multiplied by the left component spectrum XL ′ (k) and the right component spectrum XR ′ (k) is increased without changing the size of the common component spectrum, the audio output signal corresponding to the surrounding sound is obtained. Since the surrounding sound output from the speaker increases, the sense of reality can be enhanced.

  Further, the voice can be enhanced by increasing the multiplier by which the common component spectrum C (k) is multiplied without changing the sizes of the right component spectrum and the left component spectrum. On the other hand, if the multiplier by which the common component spectrum C (k) is multiplied is reduced, the sense of reality can be enhanced. Furthermore, if the common component spectrum is multiplied by 0 as a multiplier, the sense of reality can be further enhanced.

  In the present embodiment, when calculating the right component output spectrum XR ″ (k), the common component output spectrum C ″ (k), and the left component output spectrum XL ″ (k), the right component spectrum XR ′ (k) The common component spectrum C (k) and the left component spectrum XL ′ (k) are multiplied by numerical values between 0 and 1 as multipliers M1 and M2, but may be multiplied by one or more multipliers. Further, the left component spectrum XL ′ (k) and the right component spectrum XR ′ (k) may be multiplied by different multipliers, respectively, and there is no particular limitation.

  In the present embodiment, the left component spectrum XL ′ (k), the right component spectrum XR ′ (k), and the common component spectrum C (k) are multiplied by M1 (multiplier of 0 to 1) to obtain a final result. The left component spectrum XL ′ (k), the right component spectrum XR ′ (k), and the common component spectrum are configured to change the level balance of the audio output signals output to the left channel, the right channel, and the center channel. C (k) is converted into a time waveform by performing inverse FFT without multiplying by a multiplier, and the audio output signals corresponding to the left channel, right channel, and center channel obtained by the conversion are input / output same as multipliers M1 and M2. It may be configured to amplify and attenuate by characteristic amplification and attenuator, and change the level balance of each audio output signal, especially limited Not.

  That is, in addition to a configuration in which the spectral component is multiplied by a multiplier, the multiplication unit 4 performs inverse FFT or the like on the spectral component to convert it into an audio signal representing a time waveform, and then attenuates it by an attenuator or amplifies it by an amplifier. The configuration may be realized and is not particularly limited.

  The processing for changing the level balance of the audio output signal may be realized in the PEQ unit 6 or may be realized using a combination of a filter and an amplifier other than the PEQ unit 6, and is not particularly limited. For example, if the PEQ unit 6b amplifies an audio signal mainly corresponding to a human voice, a configuration that emphasizes the human voice can be realized. Further, if the PEQ unit 6a or 6c amplifies an audio signal corresponding to the surrounding sound, a configuration that enhances the sense of reality can be realized.

[Embodiment 2]
Below, with reference to FIGS. 8-9, the audio | voice signal converter 1a, 1b which can emphasize a human voice more is demonstrated.

  The audio signal conversion devices 1a and 1b are devices that are mounted on a television receiver or the like, as with the audio signal conversion device 1, and emphasize the audio of a program being broadcast. Here, the voice refers to a human voice such as dialogue or vocals, and is distinguished from sounds other than the human voice (for example, ambient noise, BGM, sound effects, etc.). That is, the audio signal conversion device 1a is a device that emphasizes the voice of a person in a broadcast program. In addition, when expressed as an audio signal, it indicates a signal that represents all sounds including audio and non-audio sounds in the program.

  In the present embodiment, two-channel audio signals digitally encoded by PCM (Pulse Code Modulation) are input to the audio signal converters 1a and 1b. Normally, in stereo broadcasting or the like, different audio signals are supplied to the left and right speakers provided in the television based on the input two-channel audio signals, and different audio is output from the left and right speakers.

  In the following, audio signals supplied to the left and right speakers in normal stereo broadcasting are respectively a left audio signal (left audio signal corresponding to the left channel) and a right audio signal (right audio signal corresponding to the right channel). Call. The right audio signal and the left audio signal are input to the audio signal converters 1a and 1b via the input terminal 12a and the input terminal 12b, respectively.

  Audio signal conversion apparatuses 1a and 1b according to the present embodiment are divided into a high-frequency component audio signal and a low-frequency component audio signal for the right audio signal and the left audio signal that are input, and the right audio signal. A common component is extracted from the high frequency component of the signal (hereinafter referred to as the right audio high frequency signal) and the high frequency component of the left audio signal (hereinafter referred to as the left audio high frequency signal). Here, the common component mainly corresponds to human voices such as vocals and lines, but strictly speaking, includes the bass and noise of musical instruments. Therefore, if the common component is extracted with respect to a high frequency component of 100 Hz or more corresponding to a human voice, for example, components other than the human voice can be more strictly removed from the common component. Thereby, it becomes possible to emphasize a human voice more correctly. Hereinafter, the speech enhancement processing in the speech signal converters 1a and 1b will be described in more detail.

(Audio signal converter 1a)
The audio signal conversion apparatus 1a according to the present invention will be described below with reference to FIG. The audio signal converter 1a outputs audio via the left, right, and center speakers based on the two-channel audio signals of the right audio signal and the left audio signal. In other words, the audio signal conversion device 1a is configured to convert the input 2-channel audio signals into 3-channel audio output signals of the left channel, the right channel, and the center channel, and supply them to each speaker.

  FIG. 8 is a block diagram showing the configuration of the audio signal converter 1a according to the present invention. The audio signal converter 1a includes a spectrum converter 2, a common component extractor (common component extractor) 3, a multiplier 4, an inverse converter (common signal generator, audio output signal generator) 5, and a parametric equalizer (PEQ; Parametric Equalizer) 6, subtractors 7 and 8, input terminal 12 and output terminal 13, delay units (high frequency signal generating means) 21 and 23, subtractors (high frequency signal generating means) 27 and 28, and low pass Filter sections (low-frequency signal generating means) 22 and 24 and adders (audio output signal generating means) 25 and 26 are provided.

  The right audio signal and the left audio signal are input to the audio signal converter 1a via the input terminal 12a and the input terminal 12b, respectively. The right audio signal input to the input terminal 12a is input to the delay unit 21 and the low-pass filter unit 22 (for example, a low-pass filter). The left audio signal input to the input terminal 12 b is input to the delay unit 23 and the low-pass filter unit 24.

  The low-pass filter unit 22 performs low-pass filtering on the input right audio signal and outputs it to the adder 25 and the subtractor 27. That is, only the low frequency component of the right audio signal (hereinafter referred to as the right audio low frequency signal) is passed. In the present embodiment, the cutoff frequency of the low-pass filtering is approximately 100 Hz. However, the cutoff frequency may be a cutoff frequency other than 100 Hz depending on the required accuracy, and is not particularly limited.

  The delay unit 21 delays the input right audio signal and outputs it to the subtractor 27. Here, the delay amount in the delay unit 21 is the delay amount in the low-pass filter unit 22 (that is, the time required for the input right audio signal to be low-pass filtered and output as the right audio low-frequency signal). Preferably they are the same. As a result, the phase of the delayed right audio signal from the delay unit 21 and the right audio low frequency signal from the low pass filter unit 22 can be matched.

  The subtractor 27 subtracts the right audio low-frequency signal from the low-pass filter unit 22 from the delayed right audio signal from the delay unit 21 and outputs the result to the spectrum conversion unit 2a. As described above, since the phase of the delayed right audio signal from the delay unit 21 and the right audio low frequency signal from the low pass filter unit 22 are synchronized, the subtractor 27 outputs a high frequency component of the right audio signal. (Hereinafter referred to as the right audio high frequency signal) is output.

  In the present embodiment, a combination of the low-pass filter unit 22, the delay unit 21, and the subtracting unit 27 outputs a low-frequency signal and a high-frequency signal. In addition, there may be a configuration in which a high frequency signal and a low frequency signal are output in combination with a subtracting unit, and there is no particular limitation.

  The spectrum conversion unit 2a calculates a frequency spectrum (hereinafter, referred to as a right audio high-frequency signal spectrum XR (k)) from the right audio high-frequency signal by FFT or the like, and sends it to the common component extraction unit 3 and the subtractor 7. Output. Note that the processing of the spectrum conversion unit 2 is the same as the processing in the audio signal conversion device 1, and thus detailed description thereof is omitted.

  The left audio signal input to the input terminal 12b is input to the delay unit 23 and the low-pass filter unit 24 in the same manner as the right audio signal input to the input terminal 12a. And the low frequency component of the left audio signal (hereinafter referred to as the left audio low frequency signal) are output to the subtractor 28. Here, the delay amount in the delay unit 23 is preferably the same as the delay amount in the low-pass filter unit 24. The low-pass filter unit 24 also outputs the left audio low-frequency signal to the adder 26. Then, the subtractor 28 subtracts the left audio low-frequency signal from the low-pass filter unit 24 from the delayed left audio signal from the delay unit 23 to obtain a high-frequency component (hereinafter, left audio) of the left audio signal. (Referred to as a high frequency signal) is output to the spectrum converter 2b. Then, the spectrum conversion unit 2b calculates a frequency spectrum (hereinafter referred to as the left audio high frequency signal spectrum XL (k)) from the left audio high frequency signal by FFT or the like, and the common component extraction unit 3 and the subtractor 8 And output. Note that the processing of the spectrum conversion unit 2 is the same as the processing in the audio signal conversion device 1, and thus detailed description thereof is omitted.

  The common component extraction unit 3 extracts the smaller spectrum of the right audio high frequency signal spectrum XR (k) and the left audio high frequency signal spectrum XL (k) as a common component. That is, the common component extraction unit 3 converts the components of the audio signal mainly representing human voice included in common with the right audio high frequency signal and the left audio high frequency audio signal into the high frequency common component C (k ). Note that the processing of the common component extraction unit 3 is the same as the processing in the audio signal conversion apparatus 1, and thus detailed description thereof is omitted.

  The subtractor 7 subtracts the high frequency common component spectrum C (k) output from the common component extraction unit 3 from the right audio high frequency signal spectrum XR (k) output from the spectrum conversion unit 2a, The band component spectrum XR ′ (k) is calculated and output to the multiplication unit 4a. That is, the subtractor 7 performs an operation of XR ′ (k) = XR (k) −C (k).

  The subtracter 8 subtracts the high frequency common component spectrum C (k) output from the common component extraction unit 3 from the left audio high frequency signal spectrum XL (k) output from the spectrum conversion unit 2b, The band component spectrum XL ′ (k) is calculated and output to the multiplication unit 4c. That is, the subtracter 8 performs the calculation of XL ′ (k) = XL (k) −C (k).

  Here, the left high frequency component spectrum XL ′ (k) and the right high frequency component spectrum XR ′ (k) mainly represent sounds other than human voice (ambient sounds such as BGM, sound effects, and noise). It is an ingredient.

  The multiplier 4a multiplies XR ′ (k) output from the subtractor 7 by a multiplier M1 (0 ≦ M1 ≦ 1) to calculate XR ″ (k) (= M1 × XR ′ (k)), and the inverse The multiplication unit 4b multiplies C (k) output from the common component extraction unit 3 by a multiplier M2 (0 ≦ M2 ≦ 1) to obtain C ″ (k) (= M2 × C). (K)) is calculated and output to the inverse transform unit 5b. Further, the multiplier 4c multiplies XL ′ (k) output from the subtractor 8 by the multiplier M1 to calculate XL ″ (k) (= M1 × XL ′ (k)), and outputs the result to the inverse converter 5c. To do.

  Hereinafter, XR ″ (k), C ″ (k), and XL ″ (k) are referred to as a right high-frequency component output spectrum, a high-frequency common component output spectrum, and a left high-frequency component output spectrum, respectively. .

  The left high-frequency component output spectrum XL ″ (k) and the right high-frequency component output spectrum XR ″ (k) are audio signal components representing surrounding sounds (sounds other than human voice).

  The inverse transform unit 5a converts the right high frequency component output spectrum XR ″ (k), which is information in the frequency domain, into a signal waveform in the time domain by inverse FFT and outputs the signal waveform to the adder 25. Further, the inverse transform unit 5b. Performs the same processing as the inverse transform unit 5a, converts the common component output spectrum C ″ (k), which is information in the frequency domain, into a signal waveform in the time domain by inverse FFT, and outputs the sound to the central speaker. A signal (central audio output signal corresponding to the central channel) is generated and output to the PEQ unit 6b. The inverse transform unit 5c performs the same processing as the inverse transform unit 5c, converts the left high-frequency component output spectrum XL ″ (k), which is information in the frequency domain, into a signal waveform in the time domain by inverse FFT, and an adder 26.

  In addition, as described above, the left audio low-frequency signal is input to the adder 25 from the low-pass filter unit 22, and the right audio low-frequency signal is input to the adder 26 from the low-pass filter unit 24. Has been.

  The adder 25 adds the signal obtained by performing inverse FFT on the right high frequency component output spectrum XR ″ (k) and the right audio low frequency signal to generate a right audio output signal corresponding to the right channel, and PEQ The adder 26 adds the signal obtained by performing inverse FFT on the left high frequency component output spectrum XL ″ (k) and the left audio low frequency signal, and adds the left side corresponding to the left channel. An audio output signal is generated and output to the PEQ unit 6c.

  The PEQ unit 6a applies a parametric equalizer having a loudness curve characteristic to the right audio output signal output from the adder 25, and outputs the parametric equalizer to the right channel speaker via the output terminal 13a. The PEQ unit 6b also applies a parametric equalizer that emphasizes the audio band having a peak of 2 kHz to the audio output signal of the central channel output from the inverse conversion unit 5b, and applies it to the speaker of the central channel via the output terminal 13b. Output. Also, the PEQ unit 6c applies a parametric equalizer having the characteristic of an equal loudness curve to the left audio output signal output from the adder 26, and outputs the result to the left channel speaker via the output terminal 13c.

  As described above, since the audio signal conversion device 1a is configured to extract a common component for the high frequency components of the input left and right audio signals, a component representing a human voice and a component other than the human voice are more strictly classified. Can be separated. Therefore, a sound output signal corresponding to a human voice and a sound output signal corresponding to a surrounding sound are generated more strictly. As a result, the level balance between the sound output signal corresponding to the human voice and the sound output signal corresponding to the surrounding sound can be changed more accurately, so that the accuracy is improved even when the human voice is emphasized. Will be able to.

  In the present embodiment, the right audio low-frequency signal and the left audio low-frequency signal obtained by performing low-pass filtering in the low-pass filter units 22 and 24 from the input signals delayed in the delay units 21 and 23 are used. Although it is the structure which subtracts and produces | generates a right audio | voice high frequency signal and a left audio | voice high frequency signal, the structure further equipped with the high-pass filter part may be sufficient. That is, the right audio low-frequency signal and the left audio low-frequency signal are subtracted from the input signal delayed in the delay unit by subtracting the right audio high-frequency signal and left audio high-frequency signal obtained by high-pass filtering in the high-pass filter unit. There may be a configuration for generating an area signal, and there is no particular limitation.

(Audio signal converter 1b)
The audio signal conversion device 1b according to the present invention will be described below with reference to FIG. The audio signal converter 1b outputs audio via the left, right, and center speakers based on the two-channel audio signals of the right audio signal and the left audio signal. That is, the audio signal conversion device 1b is configured to convert the input 2-channel audio signals into 3-channel audio output signals of the left channel, the right channel, and the center channel, and supply the audio signals to the speakers.

  FIG. 9 is a block diagram showing the configuration of the audio signal converter 1b according to the present invention. The audio signal converter 1a includes a spectrum converter 2, a common component extractor (common component extractor) 3, a multiplier (component reducer) 4, an inverse converter (common signal generator, audio output signal generator) 5, Parametric equalizer (PEQ) unit 6, subtractors 7 and 8, input terminal 12 and output terminal 13, high-pass filter units (high-frequency signal generating means) 31 and 33, and low-pass filter unit (low-frequency filter unit) Signal generating means) 32 and 34 and adders (sound output signal generating means) 35 and 36.

  Since the audio signal conversion device 1b has the same configuration as the audio signal conversion device 1a except for the high-pass filter units 31 and 33 and the low-pass filter units 32 and 34, the audio signal conversion device 1a will be described below. Only the different configuration will be described.

  The right audio signal and the left audio signal are input to the audio signal converter 1a via the input terminal 12a and the input terminal 12b, respectively. The right audio signal input to the input terminal 12a is input to the high-pass filter unit 31 (for example, a high-pass filter) and the low-pass filter unit 32. The left audio signal input to the input terminal 12b is input to the high-pass filter unit 33 and the low-pass filter unit 34.

  The high-pass filter unit 31 performs high-pass filtering on the input right audio signal and outputs it to the spectrum conversion unit 2a. That is, only the high frequency component of the right audio signal (hereinafter referred to as the right audio high frequency signal) is passed. Similarly, the high-pass filter unit 33 performs high-pass filtering on the input right audio signal and outputs it to the spectrum conversion unit 2b. That is, only the high frequency component of the left audio signal (hereinafter referred to as the left audio high frequency signal) is passed. In the present embodiment, the cutoff frequency of the low-pass filtering is approximately 100 Hz. However, the cutoff frequency may be a cutoff frequency other than 100 Hz depending on the required accuracy, and is not particularly limited.

  The low-pass filter unit 32 performs low-pass filtering on the input right audio signal and outputs it to the adder 35. That is, only the low frequency component of the right audio signal (hereinafter referred to as the right audio low frequency signal) is passed. Similarly, the low-pass filter unit 34 performs low-pass filtering on the input left audio signal and outputs it to the adder 36. That is, only the low frequency component of the left audio signal (hereinafter referred to as the left audio low frequency signal) is passed. In the present embodiment, the cutoff frequency of the low-pass filtering is approximately 100 Hz. However, the cutoff frequency may be a cutoff frequency other than 100 Hz depending on the required accuracy, and is not particularly limited. Here, it is preferable that the delay amount in the high-pass filter units 31 and 33 and the delay amount in the low-pass filter units 32 and 34 are the same.

  The audio signal conversion device 1a uses the delay units 21 and 23 and the low-pass filter units 22 and 24 to directly extract the low-frequency component of the input audio signal, and the high-frequency component from the original signal to the low-frequency component. In contrast, the audio signal conversion device 1b uses the high-pass filter units 31 and 33 and the low-pass filter units 32 and 34 to extract from the input audio signal. In this configuration, the high-frequency component and the low-frequency component are directly extracted, and this point is different from the audio signal conversion device 1a only in this point. The operations of the other parts constituting the audio signal conversion device 1b are the same as those of the audio signal conversion device 1a, and a description thereof will be omitted.

  The present invention can also be expressed as follows.

(First configuration)
In a playback apparatus for inputting a 2-channel stereo source signal including sound and reproducing the 3-channel stereo source signal including a center component, frequency converting means for converting the input source from the time domain to the frequency domain, and the left and right of the frequency-converted spectrum Means for extracting the common component of the channels, means for subtracting the extracted common component from the spectrum of the left channel and the right channel, a reproducing means for outputting the common component to the center channel, and the subtracted left and right channels A first configuration comprising means for multiplying a component by a multiplier of 0 to 1 and outputting the result to the left and right channels.

(Second configuration)
Finally, each block of the audio signal converters 1, 1a, 1b may be configured by hardware logic, or may be realized by software using a CPU as follows.

  That is, the audio signal converters 1, 1a, and 1b include a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and a RAM that expands the program. (Random access memory), a storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is to enable the computer to read the program code (execution format program, intermediate code program, source program) of the control program of the audio signal converters 1, 1a, 1b, which is software that implements the functions described above. This can also be achieved by supplying the recorded recording medium to the audio signal converters 1, 1a, 1b, and the computer (or CPU or MPU) reading out and executing the program code recorded on the recording medium.

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  Further, the audio signal converters 1, 1a, 1b may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The audio signal conversion apparatus according to the present invention can be suitably used in a television receiver or the like because it can emphasize human voices such as vocals and lines of content being broadcast or reproduced.

It is a block diagram which shows the structure of the audio | voice signal converter 1 which concerns on this invention. It is a figure for demonstrating a common component, (a) is a figure which shows the common component of a right audio | voice signal spectrum (R channel) and a left audio | voice signal spectrum (L channel), (b) is only a common component. FIG. It is a figure which shows the remaining component remove | excluding the common component spectrum from the right side audio | voice signal spectrum (R channel) and the left side audio | voice signal spectrum (L channel), (a) is a figure which shows left component spectrum XL '(k). (B) is a figure which shows right component spectrum XR '(k). It is a figure which shows right component output spectrum XR "(k) and left component output spectrum XL" (k), (a) is calculated by multiplying the right component spectrum shown to Fig.3 (a) by a predetermined multiplier. FIG. 4B shows a right component output spectrum XR ″ (k), and FIG. 3B shows a left component output spectrum XL ″ (k) calculated by multiplying the left component spectrum shown in FIG. 3B by a predetermined multiplier. FIG. It is a figure which shows the example of a frequency characteristic of the parametric equalizer which emphasizes the zone | band of the human voice which peaked about 2 kHz. It is a figure which shows the example of a frequency characteristic of the parametric equalizer which made based on the equal loudness curve and made about 4 kHz the minimum value. It is a figure which shows the equal loudness curve measured by Robinson et al. It is a block diagram which shows the structure of the audio | voice signal converter 1a which concerns on this invention. It is a block diagram which shows the structure of the audio | voice signal converter 1b which concerns on this invention.

Explanation of symbols

1 Audio signal converter (Audio signal converter)
2 Spectrum conversion unit 3 Common component extraction unit (common component extraction means)
4 Multiplying unit 4a Multiplying unit (left / right component reduction means, left / right component amplification means, component amplification means)
4b Multiplication unit (central audio output signal amplifying means, central audio output signal reducing means)
4c Multiplier (left / right component reduction means, left / right component amplification means, component amplification means)
5 Inverse conversion unit 5a Inverse conversion unit (left and right audio output signal generation means, audio output signal generation means)
5b Inverse conversion unit (central audio output signal generating means, audio output signal generating means)
5c Inverse conversion unit (left / right audio output signal generating means, audio output signal generating means)
6 PEQ section 6a PEQ section (left and right level adjustment means)
6b PEQ section (center level adjustment means)
6c PEQ section (left / right level adjustment means)
7 Subtractor (subtraction means)
8 Subtractor (subtraction means)
9 Adder (Audio output signal generation means)
10 Adder (Audio output signal generation means)
12 input terminal 13 output terminal 14 output terminal 21, 23 delay unit (high-frequency signal generating means)
22, 24 Low-pass filter section (low-frequency signal generating means)
25, 26 Adder (Audio output signal generating means)
27, 28 Subtractor (High-frequency signal generating means)
31, 33 High-pass filter section (high-frequency signal generating means)
32, 34 Low-pass filter section (low-frequency signal generating means)
35, 36 Adder (Audio output signal generating means)

Claims (8)

A right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, a right audio output signal corresponding to the right channel, and a left audio output corresponding to the left channel. An audio signal converter for converting into a signal,
A high frequency signal generating means for generating a right audio high frequency signal of 100 Hz or higher, which is a high frequency component of the right audio signal, and a left audio high frequency signal of 100 Hz or higher, which is a high frequency component of the left audio signal;
Low-frequency signal generating means for generating a right-side audio low-frequency signal less than 100 Hz that is a low-frequency component of the right-side audio signal and a left-side audio low-frequency signal less than 100 Hz that is a low-frequency component of the left-side audio signal;
A common component extraction means for extracting a high frequency common component included in common in the right audio high frequency signal and the left audio high frequency signal;
Common signal generating means for generating the central audio output signal from the high frequency common component;
The right audio high frequency signal and the high frequency common components from the left side audio high frequency signal is subtracted as each adds the right audio low frequency signal to the right audio high frequency signal after subtraction, after subtraction An audio signal comprising audio output signal generation means for generating the right audio output signal and the left audio output signal by adding the left audio low frequency signal to the left audio high frequency signal Conversion device. The low-frequency signal generating means is
Low-pass filtering the right audio signal and the left audio signal to generate the right audio low-frequency signal and the left audio low-frequency signal,
The high frequency signal generating means is
The right audio signal and the left audio signal have the same amount of delay as the low frequency signal generation means, the right audio low frequency signal is subtracted from the delayed right audio signal, and the left audio signal is delayed from the left audio signal. The audio signal conversion apparatus according to claim 1, wherein the left audio low frequency signal is subtracted to generate the right audio high frequency signal and the left audio high frequency signal. The high frequency signal generating means is
High-pass filtering the right audio signal and the left audio signal to generate the right audio high-frequency signal and the left audio high-frequency signal,
The low-frequency signal generating means is
The right audio signal and the left audio signal have the same amount of delay as the high frequency signal generating means, the right audio high frequency signal is subtracted from the delayed right audio signal, and the left audio signal is delayed from the left audio signal. The audio signal converter according to claim 1, wherein the left audio high frequency signal is subtracted to generate the right audio low frequency signal and the left audio low frequency signal. The low-frequency signal generating means is
Low-pass filtering the right audio signal and the left audio signal to generate the right audio low-frequency signal and the left audio low-frequency signal,
The high frequency signal generating means is
The audio signal conversion apparatus according to claim 1, wherein the right audio signal and the left audio signal are high-pass filtered to generate the right audio high-frequency signal and the left audio high-frequency signal.   5. The audio signal conversion apparatus according to claim 4, wherein a delay amount of the low-frequency signal generation unit is equal to a delay amount of the high-frequency signal generation unit. A right audio signal corresponding to the right channel and a left audio signal corresponding to the left channel, a central audio output signal corresponding to the center channel, a right audio output signal corresponding to the right channel, and a left audio output corresponding to the left channel. An audio signal conversion method for converting into a signal,
A high-frequency signal generation step for generating a right-frequency audio high-frequency signal of 100 Hz or higher, which is a high-frequency component of the right-side audio signal, and a left-frequency audio high-frequency signal of 100 Hz or higher, which is a high-frequency component of the left-side audio signal;
A low frequency signal generating step for generating a right audio low frequency signal of less than 100 Hz that is a low frequency component of the right audio signal and a left audio low frequency signal of less than 100 Hz that is a low frequency component of the left audio signal;
A common component extraction step for extracting a high frequency common component that is commonly included in the right audio high frequency signal and the left audio high frequency signal;
A common signal generation step of generating the central audio output signal from the high frequency common component;
The right audio high frequency signal and the high frequency common components from the left side audio high frequency signal is subtracted as each adds the right audio low frequency signal to the right audio high frequency signal after subtraction, after subtraction An audio signal comprising: an audio output signal generating step of generating the right audio output signal and the left audio output signal by adding the left audio low frequency signal to the left audio high frequency signal Conversion method.   A control program for operating the audio signal converter according to any one of claims 1 to 5, wherein the control program causes a computer to function as each of the above means.   A computer-readable recording medium in which the control program according to claim 7 is recorded.

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