JP2011049785A - Device and method for processing sound signal, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for processing sound signal allowing each viewer of video displayed on the right and left screens of a television having a dual screen display function to clearly listen to accompanying sound without securing a space for installing a center speaker nor giving an uncomfortable feeling in localization of sound. <P>SOLUTION: A sound signal processing circuit 100 includes: LR balance adjustment sections 161, 162 for setting the volume of a left channel sound signal L<SB>1</SB>' accompanying video of a left screen and output from a speaker at the left end of the left screen larger than that of a right channel sound signal R<SB>1</SB>' accompanying video of a right screen and output from a speaker at the right end of the right screen; and LR balance adjustment sections 163, 164 for setting the volume of a left channel sound signal L<SB>2</SB>' accompanying the video of the right screen and output from the speaker at the left end of the left screen smaller than that of a right channel sound signal R<SB>2</SB>' accompanying the video of the right screen and output from the speaker at the right end of the right screen. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an audio signal processing apparatus and audio signal processing method for processing two systems of stereo audio signals. The present invention also relates to a display device including such an audio signal processing device.

  With an increase in the size of a display panel, a television receiver (hereinafter abbreviated as “TV”) having a two-screen display function has become widespread. The two-screen display refers to a display mode in which the first video is displayed on the left half of the display panel and the second video is displayed on the right half of the display panel.

  When such a two-screen display function is mounted on a television, it becomes a problem how to output sound accompanying each video.

  For example, when the first audio accompanying the first video and the second audio accompanying the second video are simultaneously output from the speaker during the two-screen display, the first viewing of the first video is performed. For the viewer, it becomes difficult for the second voice to be heard and the first voice to be heard, and for the second viewer who is watching the second video, the first voice is the noise. As a result, it becomes difficult to hear the second voice. It is possible to output the first sound from the speaker and the second sound from the headphone terminal, but in this case, the viewer watching the second video is forced to wear the headphones. Cause problems.

  In order to solve such a problem, it is conceivable to use a technique for imparting directivity to the sound wave emitted from the speaker. For example, the first viewer who views the first video can listen to only the first sound attached to the first video and the second viewer who watches the second video. The sound wave emitted from the speaker may have directivity so that only the second sound accompanying the second video can be heard.

  As a technique for imparting directivity to sound waves radiated from a speaker, Patent Document 1 discloses that sound waves radiated from a first speaker unit are transmitted from a second speaker unit disposed in the vicinity of the first speaker. A technique is disclosed in which directivity is given to the emitted sound wave by canceling with the emitted sound wave.

JP 11-239400 A (published on August 31, 1999)

  However, the technique described in Patent Document 1 is not intended to reduce crosstalk between a plurality of stereo sounds, and even if it is applied to a television having a two-screen display function, an image that each viewer wants to watch Each sound cannot be separated to such an extent that only the sound accompanying the sound can be heard without being obstructed by the sound accompanying the other video.

  Further, even if the technique described in Patent Document 1 is applied to a television having a two-screen display function, there arises a problem that the sound image of the sound accompanying each screen is not localized at the center of the screen. In addition, although it is possible to install a center speaker in order to localize a sound image in the center of a screen, in this case, the installation space is required.

  The present invention has been made in view of the above problems, and its object is to view each video displayed on the left and right screens of a television having a two-screen display function without securing a space for installing a center speaker. An audio signal processing apparatus is provided that allows a person to hear the accompanying sound clearly and without giving a sense of incongruity to sound image localization.

  In the audio signal processing device according to the present invention, in order to solve the above problem, in the audio signal processing device that processes two stereo audio signals, the volume of the first channel left channel audio signal is set to the first channel right channel. First volume control means for making the volume higher than the volume of the audio signal; and second volume control means for making the volume of the left channel audio signal of the second system lower than the volume of the right channel audio signal of the second system. It is characterized by having.

  According to the above configuration, the audio signal processing device according to the present invention is connected from the left speaker to the television in which the left speaker is disposed at the left end of the left screen and the right speaker is disposed at the right end of the right screen. When connected so that the sound of the left channel sound signal of the first system and the second system is output and the sound of the right channel sound signal of the first system and the second system is output from the right speaker, the sound is output from the left speaker. The output of the left channel sound of the first system that is output from the right speaker is louder than the sound of the right channel of the first system that is output from the right speaker, and the sound of the left channel of the second system that is output from the left speaker is The volume is lower than the sound of the right channel of the second system output from the speaker. As a result, the sound image of the first system is localized at the center of the left screen, and the sound image of the second system is localized at the center of the right screen.

  Therefore, when the audio accompanying the video on the left screen is input as the first system audio and the audio accompanying the video on the right screen is input as the second system audio, the audio signal processing device according to the present invention is Without securing the space for installing the center speaker, to give each viewer of the video displayed on the left and right screens of a TV with a two-screen display function clearly and uncomfortable sound localization. There is an effect that it can be heard without any problems.

  In the audio signal processing method according to the present invention, in order to solve the above problem, in the audio signal processing method for processing two stereo audio signals, the volume of the left channel audio signal of the first system is set to the right channel of the first system. A first volume control step for increasing the volume of the audio signal, and a second volume control step for reducing the volume of the left channel audio signal of the second system to be lower than the volume of the right channel audio signal of the second system. It is characterized by including.

  According to said structure, the audio | voice signal processing method concerning this invention has an effect similar to the audio | voice signal processing apparatus concerning this invention.

  The audio signal processing device preferably further includes delay means for delaying the first channel left channel audio signal and the second channel right channel audio signal.

  According to the above configuration, the sound accompanying the left screen image is input as the first system sound, the sound accompanying the right screen image is input as the second system sound, and each When the left channel audio of the system is output from the left speaker arranged at the left end of the left screen and the right channel audio is output from the right speaker arranged at the right end of the right screen, the audio signal processing device The left channel audio attached to the left screen image and the right channel audio attached to the left screen image are simultaneously reached to the viewer located on the left screen, and the right screen audio is sent to the viewer located on the right screen side. The left channel sound accompanying the video and the right channel sound accompanying the right screen video can be reached (sounded) simultaneously.

  Therefore, the audio signal processing device is configured to provide a difference between the distance between the left speaker and the viewer and the distance between the right speaker and the viewer, that is, the time for the left channel audio to reach the viewer and the right channel audio to the viewer. There is an additional effect that the deviation of the sound image due to the difference from the arrival time can be corrected.

  The audio signal processing device includes: a first channel left channel audio signal; a first channel right channel audio signal; a second channel left channel audio signal; and a second channel right channel audio signal. The phase inversion means for inverting the phase and the first channel left channel audio signal whose phase has been inverted by the phase inversion unit are combined with the second channel left channel audio signal, and the phase is inverted by the phase inversion unit. The first channel right channel audio signal is synthesized with the second channel right channel audio signal, and the second channel left channel audio signal whose phase is inverted by the phase inversion means is converted into the first channel left channel audio signal. The second system right channel audio signal whose phase is inverted by the phase inversion means is synthesized with the first system right channel audio signal. It is desirable to provide a forming means.

  According to the above configuration, the phases of the left and right channel audio signals of the first system and the left and right channel audio signals of the second system are inverted by the phase inverting means. Then, the left channel audio signal of the first system is synthesized with the second channel audio signal of the second system whose phase is inverted, and the right channel audio signal of the first system is synthesized as the right channel audio signal of the second system whose phase is inverted. The left channel audio signal of the second system is synthesized with the left channel audio signal of the first system whose phase is inverted, and the right channel audio signal of the second system is synthesized with the right channel of the first system whose phase is inverted. Synthesized into an audio signal.

  Therefore, the sound wave radiated from the left speaker based on the left channel audio signal of the first system effectively cancels the sound wave radiated from the left speaker based on the left channel sound signal of the second system. The sound wave radiated from the right speaker based on the right channel sound signal can cancel the sound wave radiated from the right speaker based on the right channel sound signal of the second system. Similarly, the sound wave radiated from the left speaker based on the left channel sound signal of the second system effectively cancels the sound wave radiated from the left speaker based on the left channel sound signal of the first system. The sound wave radiated from the right speaker based on the right channel sound signal can cancel the sound wave radiated from the right speaker based on the right channel sound signal of the first system. Therefore, there is an additional effect that each viewer watching the video on the left screen and the video on the right screen can hear the sound associated with the video being viewed more clearly.

  The audio signal processing device is a first filter that corrects a frequency characteristic of the left channel audio signal of the first system, and has a filter characteristic corresponding to a head-related transfer function with respect to a first angle. A second filter that corrects a frequency characteristic of the right channel audio signal of the first system, the second filter having a filter characteristic corresponding to a head-related transfer function with respect to a second angle, and the second filter A third filter for correcting the frequency characteristic of the left channel audio signal of the system, the third filter having a filter characteristic corresponding to the head-related transfer function with respect to the third angle; and the right channel audio of the second system A fourth filter for correcting the frequency characteristic of the signal, and a fourth filter having a filter characteristic corresponding to a head-related transfer function with respect to the fourth angle. Masui.

  According to the above configuration, the angle formed by the line connecting the position determined in advance as the viewing position of the first system audio viewer and the position of the left speaker and the television screen is the first angle. And the second angle is an angle formed between a line segment connecting a position predetermined as the viewing position of the first-line audio viewer and the position of the right speaker and the television screen, The angle is defined as an angle formed by a line connecting the position of the left speaker and the position of the left speaker, which is predetermined as the viewing position of the audio viewer of the second system, and the fourth screen is defined as the second system. Determine the filter characteristics of each filter by determining the head-related transfer function as the angle formed between the line segment connecting the position predetermined as the viewing position of the audio viewer and the position of the right speaker and the TV screen The audio signal processing device Strengthen localization of the sound of accompanying voice, to each viewer, a further advantage of being able to hear the sound associated with looking image more clearly.

  The audio signal processing device includes: a first channel left channel audio signal; a first channel right channel audio signal; a second channel left channel audio signal; and a second channel right channel audio signal. A phase inverting means for inverting the phase, and a fifth filter for correcting the frequency characteristics of the left channel audio signal of the first system whose phase is inverted by the phase inverting means, the same filter as the third filter A fifth filter having characteristics and a sixth filter for correcting the frequency characteristics of the right channel audio signal of the first system whose phase is inverted by the phase inverting means, and the same filter characteristics as the fourth filter And a seventh filter for correcting the frequency characteristics of the second channel left channel audio signal whose phase is inverted by the phase inverting means. A seventh filter having the same filter characteristics as the first filter, and an eighth filter for correcting the frequency characteristics of the second channel right channel audio signal whose phase is inverted by the phase inverting means. An eighth filter having the same filter characteristics as the second filter, and a first left-channel audio signal whose frequency characteristic is corrected by the fifth filter, and a second-channel left-channel audio signal. The first channel right channel audio signal whose frequency characteristic is corrected by the sixth filter is synthesized with the second channel right channel audio signal, and the frequency characteristic is corrected by the seventh filter. The second left channel audio signal is synthesized with the first left channel audio signal, and the second frequency characteristic is corrected by the eighth filter. It is desirable to right channel audio signal integration and a, a synthesizing means for synthesizing the right channel audio signal of the first system.

  According to the above configuration, the sound wave radiated from the left speaker based on the first channel left channel audio signal effectively cancels the sound wave radiated from the left speaker based on the second channel left channel audio signal. The sound wave radiated from the right speaker based on the right channel sound signal of the first system can cancel the sound wave radiated from the right speaker based on the right channel sound signal of the second system. Similarly, the sound wave radiated from the left speaker based on the left channel sound signal of the second system effectively cancels the sound wave radiated from the left speaker based on the left channel sound signal of the first system. The sound wave radiated from the right speaker based on the right channel sound signal can cancel the sound wave radiated from the right speaker based on the right channel sound signal of the first system.

  Further, the synthesizing means outputs the left channel audio signal of the first system whose phase characteristics are inverted by the phase inverting means and whose frequency characteristics are corrected based on the same filter characteristics as the third filter to the third filter. Is synthesized with the second channel left-channel audio signal whose frequency characteristic is corrected based on the filter characteristic. Similarly, the synthesizing unit outputs the right channel audio signal of the first system whose phase characteristic is inverted by the phase inverting unit and whose frequency characteristic is corrected based on the same filter characteristic as that of the fourth filter, to the fourth channel. Based on the filter characteristic of the filter, the second channel right-channel audio signal whose frequency characteristic is corrected is synthesized. Further, the synthesizing means outputs the second channel left channel audio signal whose phase is inverted by the phase inverting means and whose frequency characteristics are corrected based on the same filter characteristics as the first filter, to the first filter. Are synthesized with the left channel audio signal of the first system whose frequency characteristics are corrected based on the filter characteristics. Similarly, the synthesizing unit outputs the second channel right channel audio signal whose phase is inverted by the phase inverting unit and whose frequency characteristic is corrected based on the same filter characteristic as the second filter, to the second channel. Based on the filter characteristic of the filter, the first channel right-channel audio signal whose frequency characteristic is corrected is synthesized. Therefore, the sound wave radiated from the left speaker based on the left channel audio signal of the first system has the frequency characteristic corrected based on the filter characteristic corresponding to the head-related transfer function with respect to the first angle. The sound wave radiated from the right speaker based on the right channel audio signal of one system has the frequency characteristic corrected based on the filter characteristic corresponding to the head-related transfer function with respect to the second angle. Similarly, the sound wave radiated from the left speaker based on the left channel audio signal of the second system has a frequency characteristic corrected based on a filter characteristic corresponding to the head-related transfer function with respect to the third angle, The sound wave radiated from the right speaker based on the right channel audio signal of the second system has the frequency characteristic corrected based on the filter characteristic corresponding to the head-related transfer function with respect to the fourth angle.

  From the above, the first angle is the angle formed by the line connecting the position determined in advance as the viewing position of the first-line audio viewer and the position of the left speaker and the TV screen, The second angle is an angle formed by a line segment connecting a position predetermined as the viewing position of the first-line audio viewer and the position of the right speaker and the television screen, and the third angle is , The angle formed by the line connecting the position of the left speaker and the position of the left speaker determined in advance as the viewing position of the viewer of the second system audio, and the TV screen, and the fourth angle is the audio of the second system Each head-related transfer function is determined as an angle formed by a line segment connecting a predetermined position as the viewing position of the viewer and the position of the right speaker and the screen of the television, and the filter characteristics of each filter are determined. For each video, the accompanying audio While strengthening the localization of the image, so canceling the sound associated with the other image, to each viewer, a further advantage that the sound associated with looking image can be further clearly heard.

  Note that a display device including the audio signal processing device is also included in the scope of the present invention.

  That is, the display device according to the present invention is a display device capable of simultaneously displaying two images on the left screen and the right screen, and the audio signal processing device is the first system associated with the image on the left screen. And the left channel audio signal of the first channel and the second channel obtained by processing the second channel stereo audio signal associated with the image of the right screen. The right channel audio signal of the first system and the second system obtained by processing the stereo audio signal output from the left speaker provided at the left end of the right screen is provided at the right end of the right screen. Output means for outputting from the right speaker.

  As described above, the audio signal processing device according to the present invention is attached to each viewer of video displayed on the left and right screens of a television having a two-screen display function without securing a space for installing a center speaker. The voice can be heard clearly and without giving a sense of incongruity to the sound image localization.

1, showing an embodiment of the present invention, is a block diagram showing a configuration of an audio signal processing circuit. FIG. FIGS. 2A to 2D show an embodiment of the present invention and are block diagrams showing a more detailed configuration of the digital filter unit. FIGS. 3A to 3D show the embodiment of the present invention and are block diagrams showing a more detailed configuration of the crosstalk canceling unit. It is a figure which shows that the position of a sound image will shift | deviate from the midpoint of the line segment which connects a left and right speaker, if there exists a level difference in the audio | voice output from a left and right speaker. FIG. 2 is a diagram illustrating an embodiment of the present invention and a positional relationship between speaker arrangements and viewers on a television. FIG. 6A is a diagram showing the positional relationship between the speaker arrangement and the viewer, and FIG. 6B is the interaural level difference and the sound image direction perceived by the viewer (the front is 0 °). FIG. 6C is a graph showing the correlation between the interaural time difference and the sound image direction perceived by the viewer. It is the graph which showed the relationship between the time difference between both ears and the level difference between both ears which makes a sound image localize in the center. When each sound output from two speakers is non-coherent, it is a diagram showing that sound images of each sound are easily separated as the distance between the speakers increases.

  An embodiment of an audio signal processing device according to the present invention will be described below with reference to the drawings. Since the audio signal processing apparatus according to the present embodiment is realized as a circuit that can be incorporated in a television, hereinafter, this will be referred to as an “audio signal processing circuit” and denoted by reference numeral 100.

(Audio signal processing circuit 100)
First, the configuration of the audio signal processing circuit 100 will be described with reference to FIG.

  FIG. 1 is a block diagram showing the configuration of the audio signal processing circuit 100. Generally speaking, the audio signal processing circuit 100 outputs audio for each screen from the audio / video output device 200 having two screens (screen A 210a and screen B 210b) so that the sound image is localized at the center of the screen. Therefore, this is a circuit for processing two systems of stereo audio signals input from the outside. The stereo audio signal processed by the audio signal processing circuit 100 may be an analog signal. In the following, a digital signal, particularly a PCM (Pulse Code Modulation) signal is assumed.

  As shown in FIG. 1, the audio signal processing circuit 100 generally includes an input unit 110, a directivity control unit 120, synthesis units 141 to 144, a sound image balance control unit 150, and an output unit 170. And.

  The input unit 110 is a means for receiving inputs of two stereo audio signals, and can be configured by, for example, four input terminals 111 to 114 as shown in FIG. Here, the input terminal 111 is a terminal for inputting the left channel audio signal L1 of the first system, and the input terminal 112 is a terminal for inputting the right channel audio signal R1 of the first system. The input terminal 113 is a terminal for inputting the second channel left channel audio signal L2, and the input terminal 114 is a terminal for inputting the second channel right channel audio signal R2.

  The directivity control unit 120 can be configured by four digital filter units 121 to 124 and four crosstalk cancellation units 131 to 134. The digital filter unit 121 controls the mid-high frequency directivity of the first channel left channel audio signal L1, and the digital filter unit 122 controls the mid-high frequency directivity of the first channel right channel audio signal R1. It is something to control. The digital filter unit 123 controls the directivity of the second channel left channel audio signal L2 in the mid-high range, and the digital filter unit 124 controls the directivity of the second channel right channel audio signal R2 in the mid-high range. It controls sex.

  The crosstalk cancellation units 131 to 134 generate audio signals that cancel audio output from different systems. Specifically, the crosstalk cancellation unit 131 generates an audio signal -L1 that cancels the audio output from the first system left speaker 201, and the crosstalk cancellation unit 132 receives the first system right speaker 203. A voice signal -R1 for canceling the outputted voice is generated. Further, the crosstalk canceling unit 133 generates a sound signal -L2 that cancels the sound output from the second speaker 202 in the second system, and the crosstalk canceling unit 134 is output from the right speaker 204 in the second system. A voice signal -R2 for canceling the voice is generated. The configurations of the digital filter units 121 to 124 and the crosstalk cancellation units 131 to 134 will be described in detail later.

  The combining unit 141 combines -L2 generated by the crosstalk canceling unit 133 with the signal L1 ′ whose directivity is controlled by the digital filter unit 121, and the combining unit 142 is generated by the crosstalk canceling unit 134. -R2 is combined with the signal R1 'whose directivity is controlled by the digital filter unit 122. The combining unit 143 combines -L1 generated by the crosstalk canceling unit 131 with the signal L2 ′ whose directivity is controlled by the digital filter unit 123, and the combining unit 144 is generated by the crosstalk canceling unit 132. The signal -R1 is combined with the signal R2 'whose directivity is controlled by the digital filter unit 124.

  The sound image balance control unit 150 can include delay units 151 and 154 and LR balance adjustment units 161 to 164. The delay unit 151 is a unit for delaying the input signal L1'-L2, and the delay unit 154 is a unit for delaying the input signal -R1 + R2 '. Here, the delay unit 151 is opposed to the input terminal 111 at a predetermined position (hereinafter referred to as “the position of the viewer A”) at which the viewer views the center of the screen A 210a facing the screen A 210a. , 112 so as to be able to hear each sound represented by the first-system sound signal simultaneously input to the sound system 112, and to correct a sound image shift due to a time difference. In addition, the delay unit 154 faces the screen B 210b at a predetermined position (hereinafter referred to as “viewer B position”) where the viewer is assumed to view the center of the screen B 210b. This is a configuration for correcting the deviation of the sound image due to the time difference so that each sound represented by the second-system sound signal input to 114 can be heard simultaneously.

  The LR balance adjustment units 161 and 162 adjust the output level of the input signal so that a difference in level occurs in the sound output from the left speaker 201 of the first system and the right speaker 203 of the first system. is there. Further, the LR balance adjustment units 163 and 164 adjust the output level of the input signal so that a difference in level is generated in the sound output from the second speaker 202 and the second speaker 204. Is. The LR balance adjustment unit is configured to obtain a sound image moving effect due to a level difference between sounds output from the left and right speakers. The sound image moving effect due to the delay will be described later with reference to the drawings.

  The output unit 170 is a means for outputting a processed audio signal to the outside, and can be constituted by four output terminals 171 to 174 as shown in FIG.

  Here, from the output terminal 171, a signal (L 1 ′ −L 2) ′ whose sound level has been adjusted by the LR balance adjustment unit 161 is output. Similarly, (−L1 + L2 ′) ′ is output from the output terminal 172, (R1′−R2) ′ is output from the output terminal 173, and (−R1 + R2 ′) is output from the output terminal 174. ) 'Is output.

  The audio signal processed by the audio signal processing circuit 100 is, for example, by a digital-analog converter (hereinafter abbreviated as “DAC”) 180 provided at the subsequent stage of the audio signal processing circuit 100 as shown in FIG. It is converted into an analog audio signal, further amplified by an amplifier 190 provided at the subsequent stage of the DAC 180, and then supplied to the video / audio output device 200.

(Video / audio output device 200)
As the audio / video output device 200 that is the output destination of the audio signal processed by the audio signal processing circuit 100, a television, a display, or the like is assumed. The video / audio output device 200 will be described in more detail with reference to FIG.

  5 shows the arrangement of the screen A 210a, the screen B 210b, the left speaker 201 for the screen A, the left speaker 202 for the screen B, the right speaker 203 for the screen A, and the right speaker 204 for the screen B in the video / audio output apparatus 200. Show.

  As shown in FIG. 5, the video / audio output device 200 has a two-screen display function, and can display the video A on the screen A 210a and the video B on the screen B 210b. . The audio signals L1 and R1 shown in FIG. 1 are stereo audio signals representing the audio A associated with the video A, and the audio signals L2 and R2 shown in FIG. Is a stereo audio signal representing

  In the video / audio output device 200, the left speaker 201 for the screen A and the left speaker 202 for the screen B are arranged below the left end of the screen A 210a so as to be adjacent to the left and right, respectively. It is composed. Further, the right speaker 203 for the screen A and the right speaker 204 for the screen B are arranged below the right end of the screen B 210b so as to be adjacent to the left and right, respectively, and constitute the right speaker 200b.

  In the present embodiment, the horizontal distance L between the left speaker for the screen A and the right speaker 204 for the screen B may be determined according to the sum of the horizontal width of the screen A 210a and the horizontal width of the screen B 210b. In the case of 65-inch type, it is set to about 1.4 m. In the present embodiment, it is assumed that L = 1.4 m. That is, the widths of the screens A and B are 0.7 m, and the distance L / 4 = 0.35 m from the center of the screens A and B to the boundary line between the screens A and B.

(Digital filter part 121-124)
Each configuration of the digital filter units 121 to 124 will be described below with reference to FIGS. 2 and 5. 2A to 2D are block diagrams showing the configurations of the digital filter units 121 to 124, respectively.

As shown in FIG. 2A, the digital filter unit 121 extracts the medium-frequency component of the input signal using the HPF 121a, and the HRTF (head related transfer function) filter 121c (first filter) is extracted. The frequency characteristic of the medium-high frequency component is corrected based on the filter characteristic corresponding to the head-related transfer function. Here, this head-related transfer function is an angle θ _AL (first angle) formed by a line segment connecting the speaker 201 and the position of the viewer A and a perpendicular line drawn from the screen A to the position of the viewer A. Is determined in advance. Further, the digital filter unit 121 extracts a low frequency component of the input signal by the LPF 121b. The digital filter unit 121 synthesizes the medium and high frequency components whose frequency characteristics are corrected by the HRTF filter 121c and the low frequency components extracted by the LPF 121b, and outputs them to the outside.

Similar to the digital filter unit 121, the digital filter units 122 to 124 change the frequency characteristics of the medium-high frequency component of the input signal according to the head-related transfer function, as shown in FIGS. 2 (b) to 2 (d). The correction is made based on the filter characteristics, and the medium and high frequency components with the corrected frequency characteristics and the low frequency components are synthesized and output to the outside. Note that the head-related transfer function used by the HRTF filter 122c (second filter) of the digital filter unit 122 for correcting the frequency characteristic is a line segment connecting the speaker 203 and the position of the viewer A, and the screen A to the viewer. It is determined in advance according to the angle θ _AR (second angle) formed by the perpendicular drawn to the position A. Similarly, the head-related transfer function that the HRTF filter 123c (third filter) of the digital filter unit 123 uses for correcting the frequency characteristics is viewed from the screen B and the line segment connecting the speaker 202 and the position of the viewer B. party and perpendicular line to the position of B, and predetermined in accordance with the angle theta _BL (third angle), the correction of the HRTF filters 124c (fourth filter) is the frequency characteristic of the digital filter section 124 The head-related transfer function to be used depends on an angle θ _BR (fourth angle) formed by a line segment connecting the speaker 204 and the position of the viewer B and a perpendicular line drawn from the screen B to the position of the viewer B. Predetermined.

  As described above, by configuring the digital filter units 121 to 124, the left and right channel sounds accompanying the screen A output from the speakers 201 and 203, respectively, are more prominently heard at the position of the viewer A. The left and right channel sounds accompanying the screen B, which are respectively output from 202 and 204, can be heard more remarkably at the position of the viewer B.

(Crosstalk cancellation unit 131-134)
Each configuration of the crosstalk cancellation units 131 to 134 will be described below with reference to FIG. FIGS. 3A to 3D are block diagrams illustrating the configurations of the crosstalk cancellation units 131 to 134, respectively.

  As shown in FIG. 3A, the crosstalk cancellation unit 131 inverts the phase of the input signal by 180 degrees in the antiphase filter 131a (phase inversion means), and the medium frequency component from the signal after phase inversion in the HPF 131b. To extract. Further, the crosstalk canceling unit 131 is predetermined based on a filter characteristic (that is, a third angle) that is the same as the filter characteristic of the HRTF filter 123c (third filter) in the HRTF filter 131c (fifth filter). The frequency characteristic of the medium / high frequency component is corrected based on the filter characteristic according to the head-related transfer function), and the corrected medium / high frequency component is output to the outside.

  Similar to the crosstalk cancellation unit 131, the crosstalk cancellation units 132 to 134 invert the phase of the input signal by 180 degrees as shown in FIG. 3B to FIG. The high frequency component is extracted from the frequency, and the frequency characteristic of the extracted high frequency component is corrected based on the filter characteristic corresponding to the head-related transfer function. Note that the filter characteristic of the HRTF filter 132c (sixth filter) of the crosstalk canceling unit 132 is the filter characteristic of the HRTF filter 124c (fourth filter) (that is, a head that is predetermined based on the fourth angle). Filter characteristics corresponding to the transfer function). Similarly, the filter characteristic of the HRTF filter 133c (seventh filter) of the crosstalk canceling unit 133 is the same as the filter characteristic of the HRTF filter 121c (first filter) (that is, a predetermined head based on the first angle). The filter characteristic of the HRTF filter 134c (eighth filter) of the crosstalk cancellation unit 134 is the same as the filter characteristic of the HRTF filter 122c (second filter) (ie, the first filter characteristic). Filter characteristics corresponding to a head-related transfer function determined in advance based on the angle of 2).

  As described above, by configuring the crosstalk cancellation units 131 to 134, the left and right channel sounds accompanying the screen A output from the speakers 201 and 203 are prevented from being heard at the position of the viewer B. Can do. Further, it is possible to prevent the left and right channel sounds accompanying the screen B output from the speakers 202 and 204 from being heard at the position of the viewer A, respectively.

  As described above, the directivity control unit 120 can clearly hear the sound associated with the screen A at the position of the viewer A, and can clearly hear the sound associated with the screen B at the position of the viewer B. .

(Adjustment amount of audio output delay time and audio level performed by the sound image balance control unit 150)
Next, the audio output delay time and audio level adjustment amount performed by the sound image balance control unit 150 will be described. Before that, referring to FIGS. 4 to 7, the audio level output from the left and right speakers The relationship between the difference and time difference and the moving amount of the sound image will be described.

  FIG. 6 (a) shows the positional relationship between the left and right speakers and the listener. FIG. 6 (b) shows the interaural level difference and the listener's level under the conditions of FIG. 6 (a). FIG. 6C is a graph showing the correlation of the perceived sound image direction (azimuth angle with the front being 0 °), and FIG. 6C shows the correlation between the interaural time difference and the sound image direction perceived by the viewer under the same conditions. (All are based on Jens Brauert, Masayuki Morimoto, Toshiyuki Goto, “Spatial Acoustics”, Kashima Publishing Co., Ltd., Fig. 4.2). FIG. 7 is a graph showing the relationship between the interaural time difference and the interaural level difference in which the sound image is localized in the center without being biased under the conditions of FIG. -Based on Brauert, Masayuki Morimoto, Toshiyuki Goto, "Spatial Acoustics", based on Figure 4.5 of Kashima Publishing Co.).

  As shown in FIG. 6B and FIG. 7, when the level of the sound output from the left (right) speaker is higher than the level of the sound output from the right (left) speaker, the listener uses the left speaker. It can be seen that a sound image is perceived on the left (right) side from the center of the speaker and the right speaker. In addition, as shown in FIG. 6C and FIG. 7, when the sound is output from the left (right) speaker earlier than the sound is output from the right (left) speaker, that is, the listener is left When listening to the sound output from the (right) speaker earlier than the sound output from the right (left) speaker, the listener displays a sound image on the left (right) side from the center of the left and right speakers. I understand that I perceive.

  The sound image moves depending on the level difference of the output sound and the time difference of the listener listening to the sound in the case of FIG. 6A where the listener is located at an equal distance from the left speaker and the right speaker. The same applies to the case where the viewer A (B) is not located at the same distance from the speakers 201 and 203 for the screen A (the speakers 202 and 204 for the screen B) as shown in FIG. It is. That is, the viewer A (B) has no level difference in the sound output from the left speaker 201 for the screen A and the right speaker 203 (the left speaker 202 for the screen B, the right speaker 204), and the left speaker 201 (left When the sound from the speaker 202) and the sound from the right speaker 203 (right speaker 204) are simultaneously heard, the sound image is perceived at the boundary between the screen A 201a and the screen B 201b. On the other hand, the level of the sound output from the left speaker 201 for the screen A is larger (smaller) than the level of the sound output from the right speaker 203 for the screen A, and the sound from the left speaker 201 and the sound from the right speaker 203 are When the viewer A listens simultaneously, the sound image perceived by the viewer A moves to the screen A side (screen B side) from the boundary portion. Further, the level of the sound output from the left speaker 202 for the screen B is larger (smaller) than the level of the sound output from the right speaker 204 for the screen B, and the sound from the left speaker 202 and the sound from the right speaker 204 are When the viewer B listens simultaneously, the sound image perceived by the viewer B moves to the screen B side (screen A side) from the boundary portion.

  As described above, the delay unit 151 is configured so that the sound by the left and right audio signals for the screen A input simultaneously can be heard at the position of the viewer A at the same time. It plays a role of shifting the timing at which the left and right sounds are output from the speakers so that the sound by the sound signal can be heard simultaneously at the position of the viewer B.

In the present embodiment, the distance D from the position of the viewer A to the screen A and the distance D from the viewer B to the screen B are each 1 m. That is, tan θ _AL = tan θ _BR = (L / 4) /D=0.35, and θ _AL = θ _BR = about 19.3 °. Further, tan θ _AR = tan θ _BL = (3L / 4) /D=1.05, and θ _AR = θ _BL = about 46.4 °.

In this case, the delay time by the delay units 151 and 154 is from the distance ((3L / 4) ² + D ² ) ^1/2 between the position of the viewer A (B) and the position of the left speaker 201 (left speaker 202). A value obtained by dividing the speed of sound (340 m / s) from the value obtained by subtracting the distance ((L / 4) ² + D ² ) ^1/2 between the position of the viewer A (B) and the position of the right speaker 203 (right speaker 204). Therefore, it becomes about 1.2 ms.

  In addition, the LR balance adjustment unit 161 and the LR balance adjustment unit 162 make the level of the sound output from the left speaker 201 larger than the level of the sound output from the right speaker 203 so that the viewer A perceives it. The sound image is positioned at the center of the screen A.

  In the present embodiment, in order to move the sound image to the center of the screen A, it is necessary to move the 0.35 m sound image. Therefore, the LR balance adjustment unit 161 and the LR balance adjustment unit 162 are output from the left speaker 201. The sound level is adjusted to be about 2 dB higher than the sound level output from the right speaker 203.

  Similarly, the LR balance adjustment unit 163 and the LR balance adjustment unit 164 are adjusted so that the level of the sound output from the right speaker 204 is approximately 2 dB higher than the level of the sound output from the left speaker 202. The sound image perceived by the person B is positioned at the center of the screen B.

(Advantages of the audio signal processing circuit 100)
As described above, the audio signal processing circuit 100 causes the LR balance adjustment unit 161 to make the volume of the left channel audio signal L ₁ ′ of the first system larger than the volume of the right channel audio signal R ₁ ′ of the first system. 162, and LR balance adjusting sections 163 and 164 for making the volume of the second channel left channel audio signal L ₂ ′ smaller than the volume of the _second channel right channel audio signal R ₂ ′.

That is, in the audio signal processing circuit 100, the LR balance adjustment units 161 and 162 are attached to the video of the screen A 210a (left screen) of the audio / video output device 200 and are output from the speaker 200a at the left end of the screen A 210a. The volume of the audio signal L ₁ ′ is set higher than the volume of the right channel audio signal R ₁ ′ attached to the video on the screen A 210a and output from the speaker 200b at the right end of the screen B 210b (right screen). Similarly, the LR balance adjusting units 163 and 164 attach the volume of the left channel audio signal L ₂ ′ output from the speaker 200a at the left end of the screen A 210a to the video of the screen A 210a, and attach to the video of the screen B 210b. The volume of the right channel audio signal R ₂ ′ output from the speaker 200b at the right end of the screen B210b is set to be smaller.

  As a result, the audio accompanying the left screen image is localized at the center of the left screen image, and the audio accompanying the right screen image is localized at the center of the right screen image. Even without this, it is possible to allow the viewer of the left screen video and the viewer of the right screen to hear the sound accompanying each video clearly and without giving a sense of incongruity to the sound image localization.

(Additional notes)
The audio / video output device 200 from which the audio signal processing circuit 100 outputs an audio signal has a two-screen display function. The left speaker for each of the left and right screens is provided at the left end of the left screen, and for each of the left and right screens. However, the left screen speakers 201 and 203 and the right screen speakers 202 and 204 should be as far as possible from each other as long as the right speaker is positioned adjacent to the right edge of the right screen. desirable. This is because the sound image of the sound output from the left screen speaker and the sound image of the sound output from the right screen speaker are easily separated, and the clarity is improved like a cocktail party effect. This will be described below with reference to FIG. FIG. 8 is a diagram showing the position at which the listener perceives the sound image in terms of the azimuth angle φ and the elevation angle δ when the sounds output from the two speakers are non-coherent (by Jens Brawelt, Morimoto). Masayuki, translated by Toshiyuki Goto, “Spatial Acoustics”, based on Kashima Publishing Co., Ltd., Figure 4.32.) Here, the hatched portion in each figure indicates a position where the listener perceives a sound image relatively high, and the mesh portion indicates a position where the listener perceives a sound image relatively low. .

  As FIG. 8 shows, the closer the distance between the two speakers, the sound image of the sound output from each speaker appears in a certain azimuth and elevation range, and the longer the distance between the two speakers, It can be seen that the sound image of the sound output from each speaker is separated into different ranges.

  When the two-screen display function of the video / audio output device 200 that outputs an audio signal is used by the audio signal processing circuit 100 of the present embodiment, a different video is generally displayed on each screen. The sound accompanying the video and the sound accompanying the video on the right screen are usually incoherent. Therefore, as the left screen speakers 201 and 203 and the right screen speakers 202 and 204 are separated as much as possible, the viewer can clearly hear the sound accompanying the video being viewed.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention can be particularly suitably used for a display device that displays two screen images simultaneously.

100 Audio signal processing circuit (audio signal processing device)
DESCRIPTION OF SYMBOLS 110 Input part 120 Directivity control part 121-124 Digital filter part 131-134 Crosstalk cancellation part 141-144 Synthesis | combination part (synthesis | combination means)
150 Sound image balance control unit 151, 154 Delay unit (delay means)
161, 162 LR balance adjustment unit (first volume control means)
163, 164 LR balance adjustment unit (second volume control means)
170 Output unit (output means)
200 Video / Audio Output Device 200a Left Speaker 201 Screen A Left Speaker 202 Screen B Left Speaker 200b Right Speaker 203 Screen A Right Speaker 204 Screen B Right Speaker 210a Screen A (Left Screen)
210b Screen B (right screen)

Claims (7)

In an audio signal processing apparatus that processes two stereo audio signals,
First volume control means for making the volume of the left channel audio signal of the first system larger than the volume of the right channel audio signal of the first system;
An audio signal processing apparatus comprising: a second volume control unit configured to make the volume of the left channel audio signal of the second system smaller than the volume of the right channel audio signal of the second system.   2. The audio signal processing apparatus according to claim 1, further comprising delay means for delaying the left channel audio signal of the first system and the right channel audio signal of the second system. Phase inversion means for inverting the phase of each of the first channel left channel audio signal, the first channel right channel audio signal, the second channel left channel audio signal, and the second channel right channel audio signal. When,
The first system left channel audio signal whose phase is inverted by the phase inversion means is synthesized with the second system left channel audio signal, and the first system right channel audio signal whose phase is inverted by the phase inversion means. Is synthesized with the second channel right channel audio signal, the second channel left channel audio signal whose phase is inverted by the phase inverting unit is synthesized with the first channel left channel audio signal, and the phase inverting unit 3. The audio signal according to claim 1, further comprising: a synthesizing unit configured to synthesize the second channel right channel audio signal whose phase is inverted by the first channel right channel audio signal. Processing equipment.   A first filter that corrects a frequency characteristic of the left channel audio signal of the first system, the first filter having a filter characteristic corresponding to a head-related transfer function with respect to a first angle; A second filter for correcting the frequency characteristic of the right channel audio signal, the second filter having a filter characteristic corresponding to the head-related transfer function with respect to the second angle, and the left channel audio signal of the second system. A third filter for correcting the frequency characteristic, the third filter having a filter characteristic corresponding to the head-related transfer function with respect to the third angle, and the frequency characteristic of the right channel audio signal of the second system are corrected. A fourth filter, comprising: a fourth filter having a filter characteristic corresponding to a head-related transfer function with respect to a fourth angle. The audio signal processing apparatus according to. Phase inversion means for inverting the phase of each of the first channel left channel audio signal, the first channel right channel audio signal, the second channel left channel audio signal, and the second channel right channel audio signal. When,
A fifth filter for correcting the frequency characteristics of the first channel left channel audio signal whose phase is inverted by the phase inverting means, the fifth filter having the same filter characteristics as the third filter; A sixth filter that corrects a frequency characteristic of the right channel audio signal of the first system whose phase is inverted by the phase inverting means, the sixth filter having the same filter characteristic as the fourth filter; A seventh filter for correcting the frequency characteristics of the second channel left channel audio signal whose phase has been inverted by the phase inverting means and having the same filter characteristics as the first filter; and the phase An eighth filter that corrects the frequency characteristics of the second-channel right-channel audio signal whose phase is inverted by the inverting means, and is the same as the second filter. An eighth filter having a filter characteristic,
The first channel left channel audio signal whose frequency characteristic is corrected by the fifth filter is synthesized with the second channel left channel audio signal, and the first channel whose frequency characteristic is corrected by the sixth filter. The right channel audio signal is synthesized with the second channel right channel audio signal, and the second channel left channel audio signal whose frequency characteristics are corrected by the seventh filter is synthesized with the first channel left channel audio signal. And synthesizing means for synthesizing the second-channel right channel audio signal whose frequency characteristic is corrected by the eighth filter with the first-channel right channel audio signal. 4. The audio signal processing device according to 4. A display device capable of simultaneously displaying two images on a left screen and a right screen,
The audio signal processing device according to any one of claims 1 to 5,
The audio signal processing apparatus is obtained by processing the first system stereo audio signal associated with the left screen image and the second system stereo audio signal associated with the right screen image. The sound of the left channel audio signal of the first system and the second system is output from the left speaker provided at the left end portion of the left screen, and the first system and the above obtained by processing the stereo audio signal An output means for outputting the sound of the right channel audio signal of the second system from a right speaker provided at the right end of the right screen. In an audio signal processing method for processing two stereo audio signals,
A first volume control step of making the volume of the left channel audio signal of the first system larger than the volume of the right channel audio signal of the first system;
And a second volume control step of making the volume of the second channel left channel audio signal smaller than the volume of the second channel right channel audio signal.

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