JP3942914B2 - Stereo signal processor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stereo signal processing apparatus, and more particularly, to a stereo signal processing apparatus for processing a digital signal or the like obtained from a recording medium such as stereo digital broadcasting and DVD (Digital Versatile Disk).
[0002]
[Prior art]
Conventionally, a so-called 5.1-channel stereo device is known as a device for enjoying highly realistic 3D sound. This is the first time since the use of DVDs and BS (Broadcasting Satellite) digital broadcasting has become possible, and not only 2-channel stereo sound signals but also 5.1-channel stereo sound signals can be used. Because it became.
[0003]
Here, the sound channel in 5.1 channel stereo is constituted by a center channel, a right rear channel, a left rear channel, and a low frequency emphasis channel in addition to the right channel and the left channel. In a standard reproduction apparatus, the sound signals of the five channels excluding the low frequency emphasis channel are reproduced as they are by the five speakers 201 to 205 shown in FIG. For the low frequency enhancement channel, the speaker position for the low frequency enhancement channel is free.
[0004]
In a limited space such as a home, it is often difficult to use a wide-band speaker for all five channels in terms of securing the speaker placement. In practice, the following playback method is used. .
The first method is a method in which the rear left and right rear speakers 204 and 205 are smaller than the front left and right speakers 201 and 202, and the low-frequency component sound that is insufficient is supplemented and reproduced via the subwoofer. .
[0005]
The second method is a so-called front surround method in which the sound to be output from the rear speaker is reproduced with only the two front speakers without providing any speaker behind. In this method, not only the center channel sound signal is distributed to the left and right channels, but also the left and right rear channel sound signals are subjected to inverse filtering of the head-related transfer function so that the virtual sound source is located at the left rear and right rear. Synthesized. In other words, it is possible to hear the sound at the place for hearing without actually installing a rear speaker.
[0006]
[Problems to be solved by the invention]
However, in the first conventional method, there is a problem that the timbre difference between the sound from the small rear speaker and the sound from the front speaker tends to be large, and the sense of discomfort is likely to occur in terms of the sense of movement and wrapping of the sound. there were. This tendency becomes more prominent as the rear speaker is made smaller.
[0007]
Moreover, in the second method, since the sound cannot actually be heard from behind, there is a problem that the effect surrounded by the sound from the original four directions of the 5-channel stereo is reduced. This is a common disadvantage of the method using the head-related transfer function. The head-related transfer function used in the inverse filter design is different from the viewer's own head-related transfer function. This is due to inaccurate reproduction of band components. Although it is theoretically possible to use the viewer's own head-related transfer function, it is impractical when targeting an unspecified number of users as in broadcasting.
[0008]
The present invention has been made to solve such a problem, and an object of the present invention is to generate a signal for reproducing a sound with a reduced sense of incongruity even when a small rear speaker is used. The object is to provide a stereo signal processing apparatus.
[0009]
[Means for Solving the Problems]
In view of the above points, the invention according to claim 1 is a position that forms a first angle smaller than 90 degrees in the clockwise direction with respect to the front direction of the listening position on the circumference of a predetermined radius centered on the listening position. A right channel assigned to the right speaker arranged at the left channel assigned to the left speaker arranged at a position that forms the first angle counterclockwise with respect to the front direction of the listening position of the circumference, A right rear channel assigned to a right rear speaker disposed at a position that forms a second angle that is smaller than 90 degrees counterclockwise with respect to the front direction after the listening position on the circumference and smaller than the first angle. And four or more channels including a left rear channel assigned to a left rear speaker disposed at a position that forms the second angle clockwise with respect to the front direction after the listening position on the circumference In the stereo signal processing apparatus for processing a sound reproduction signal for a channel, the sound reproduction signal for the right rear channel is divided into an SR high-frequency component signal that is a predetermined audible frequency or higher and a SR that is lower than the reference frequency. A first filter for dividing the first rear filter into a middle-low frequency component signal, and an acoustic reproduction signal for the left rear channel, an SL high-frequency component signal equal to or higher than the reference frequency and an SL mid-low frequency component signal less than the reference frequency And a first filter for generating a corrected SRR middle low-frequency component signal by correcting with a head-related transfer function when the SR middle low-frequency component signal is output from the right speaker. And a second compensation filter for generating a corrected SRL middle low-frequency component signal by correcting with the head related transfer function when the SR middle low-frequency component signal is output from the left speaker. A third compensation filter for generating a corrected SLR mid-low frequency component signal by correcting with a head-related transfer function when the SL mid-low frequency component signal is output from the right speaker, and the SL mid-low frequency signal A fourth compensation filter for generating a corrected SLL middle / low frequency component signal by correcting with a head-related transfer function when the frequency component signal is output from the left speaker, the sound reproduction signal for the right channel, and the correction A first adder for adding the SRR mid-low frequency component signal and the corrected SLR mid-low frequency component signal to output as the right channel sound reproduction signal; the left channel sound reproduction signal; and A second adder for adding the corrected SRL mid-low frequency component signal and the corrected SLL mid-low frequency component signal and outputting as a sound reproduction signal for the left channel; Right Output as a rear channel sound reproduction signal, output the SL high frequency component signal as the left rear channel sound reproduction signal, and the first compensation filter and the second compensation filter are connected to the right speaker. The SR mid-frequency component signal output from the left rear speaker relative to the listening position relative to the listening position, and the third compensation filter and the fourth compensation filter are connected to the left speaker. The SL middle low-frequency component signal to be output is localized at a symmetrical position in the front- rear direction of the left rear speaker with respect to the listening position.
With this configuration, the mid-low range sound is handled by the front speaker, and the virtual sound image is synthesized in a position symmetrical to the front and rear of the rear speaker. It is possible to realize a stereo signal processing apparatus capable of outputting sound with a sense of incongruity reduced in terms of hearing.
[0010]
The invention according to claim 2 has a configuration in which, in claim 1, the reference frequency is any frequency between 1.5 kHz and 6 kHz and is variable. With this configuration, since the reference frequency can be adjusted within the range of 1.5 kHz to 6 kHz, a stereo signal processing device that can respond to individual differences among viewers, the size and type of speakers that can be used, the environment, and the like can be realized.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a stereo signal processing apparatus according to a first embodiment of the present invention will be described with reference to the accompanying drawings. The present invention utilizes the fact that the sense of front and back of the sound image perceived by the viewer is formed based on sound in a frequency band of approximately 6 kHz or more. In other words, the mid-low range sound below about 6 kHz utilizes the fact that it does not play an important role in perception before and after the sound image.
[0012]
FIG. 1 is a diagram showing a schematic block configuration of a stereo signal processing apparatus according to the first embodiment of the present invention. The stereo signal processing apparatus 100 includes first and second high-pass filters (hereinafter referred to as HPFs) 11 and 21, first and second low-pass filters (hereinafter referred to as LPFs) 12 and 22, and second. 1 to 4 compensation filters 13, 14, 23, 24 and first and second adders 30, 40 are included.
[0013]
As shown in FIG. 1, the stereo signal processing apparatus 100 includes an input R signal that is an input signal for the right channel, an input L signal that is an input signal for the left channel, and an input C signal that is an input signal for the center channel. The input SR signal, which is an input signal for the right rear channel, and the input SL signal, which is an input signal for the left rear channel, are input.
FIG. 2 is a diagram schematically showing the arrangement of speakers from which signals are output from the stereo signal processing apparatus 100. The five speakers shown in FIG. 2 include left and right speakers 201 and 202, a center speaker 203, and left and right rear speakers 204 and 205.
[0014]
The first HPF 11 receives an input SR signal, passes a signal having a frequency component equal to or higher than a predetermined frequency in the input SR signal, and outputs an output SR signal obtained by passing the signal from the stereo signal processing device 100. It is means of. Hereinafter, the predetermined frequency is referred to as a reference frequency, and the reference frequency may be, for example, the above 6 kHz. A signal having a frequency band component equal to or higher than the reference frequency is referred to as a high-frequency component signal, and a signal having a frequency band component lower than the reference frequency is also referred to as a middle / low-frequency component signal.
[0015]
The first LPF 12 receives an input SR signal, passes a signal having a frequency component equal to or lower than the reference frequency in the input SR signal (hereinafter referred to as an SR low-frequency component signal), and passes the first and second signals. This is a means for outputting to the compensation filters 13 and 14. As a result, the input SR signal is separated into two frequency component signals by the first HPF 11 and the first LPF 12 with the reference frequency as a boundary.
[0016]
The first compensation filter 13 has the SR mid-frequency component signal output from the first LPF 12 as an input, performs a correction process on the SR mid-frequency component signal in consideration of the head-related transfer function of the sound, and performs the correction process. This is means for outputting the corrected SRR middle / low frequency component signal, which is the signal obtained by the above, to the first adder 30. In the correction process in consideration of the head-related transfer function of sound performed by the first compensation filter 13, the correction process is performed in consideration of the head-related transfer function when output from the right speaker 201.
[0017]
The second compensation filter 14 receives the SR mid-frequency component signal output from the first LPF 12 and performs a correction process on the SR mid-frequency component signal in consideration of the head-related transfer function of the sound. This is a means for outputting the corrected SRL middle / low band component signal, which is the signal obtained by the above, to the second adder 40. In the correction process in consideration of the head-related transfer function of the sound performed by the second compensation filter 14, the correction process is performed in consideration of the head-related transfer function when output from the left speaker 202.
[0018]
The second HPF 21 receives the input SL signal, passes a signal having a frequency component equal to or higher than the reference frequency in the input SL signal, and outputs an output SL signal obtained by passing the signal from the stereo signal processing device 100. Means. As a result, a signal having the same frequency component as that of the first HPF 11 is output from the second HPF 21.
[0019]
The second LPF 22 receives the input SL signal, and passes a signal having a frequency component equal to or lower than the reference frequency in the input SL signal (hereinafter referred to as an SL low-frequency component signal). This is means for outputting to the compensation filters 23 and 24. As a result, the input SL signal is separated into two frequency component signals by the second HPF 21 and the second LPF 22 with the same reference frequency as that of the input SR signal as a boundary.
[0020]
The third compensation filter 23 receives the SL low-frequency component signal output from the second LPF 22 and performs correction processing on the SL low-frequency component signal in consideration of the head-related transfer function of the sound. This is means for outputting the corrected SLR mid-low frequency component signal, which is the signal obtained by the above, to the first adder 30. In the correction process in consideration of the head-related transfer function of sound performed by the third compensation filter 23, the correction process is performed in consideration of the head-related transfer function when output from the right speaker 201.
[0021]
The fourth compensation filter 24 has the SL low-frequency component signal output from the second LPF 22 as input, performs a correction process on the SL low-frequency component signal in consideration of the head-related transfer function of the sound, and performs the correction process. This is a means for outputting the corrected SLL mid-low frequency component signal, which is the signal obtained by the above, to the second adder 40. In the correction process in consideration of the head-related transfer function of sound performed by the fourth compensation filter 24, the correction process is performed in consideration of the head-related transfer function when output from the left speaker 202.
[0022]
The first adder 30 adds the input R signal, the corrected SRR middle low frequency component signal output from the first compensation filter 13, and the corrected SLR middle low frequency component signal output from the third compensation filter 23. The signal obtained by the addition is a means for outputting from the stereo signal processing apparatus 100 as an output R signal.
[0023]
The second adder 40 adds the input L signal, the corrected SRL middle low frequency component signal output from the second compensation filter 14, and the corrected SLL middle low frequency component signal output from the fourth compensation filter 24. The signal obtained by the addition is a means for outputting from the stereo signal processing apparatus 100 as an output L signal.
[0024]
Note that the input C signal which is an input signal for the center channel is output from the stereo signal processing apparatus 100 as an output C signal as it is. Therefore, the input C signal only passes through the stereo signal processing apparatus 100 and is the same signal as the output C signal.
[0025]
The first to fourth compensation filters 13, 14, 23, and 24 for compensating the head related transfer function reproduce the corrected SRR mid-frequency component signal and the corrected SLR mid-frequency component signal on the right speaker 201. When the corrected SRL mid-low frequency component signal and the corrected SLL mid-low frequency component signal are reproduced by the left speaker 202, the SR mid-low frequency component signal and the SL mid-low frequency component signal are respectively virtual speakers 206, 207. Designed to localize. Here, a method for localization is known, and is disclosed in, for example, Japanese Patent Laid-Open No. 6-189399.
[0026]
Here, it is assumed that the virtual speaker 206 and the left rear speaker 205 are in a front-rear symmetrical positional relationship with the right rear speaker 204 and the left rear speaker 205, respectively. The mid-low range sound is likely to be misrecognized with respect to the front-rear relationship of the sound image. If the sound signals are emitted from the rear speakers 204 and 205 that are symmetrical with the virtual speakers 206 and 207, the sound reproduction signals for the left and right rear channels are recognized at the positions of the rear speakers 204 and 205, respectively.
[0027]
In the above description, the reference frequency, which is the reference of the frequency of the sound that affects the sense of front and back of the sound image, has been described as approximately 6 kHz. Therefore, the reference frequency may be variable and adjustable within the range of 1.5 kHz to 6 kHz.
[0028]
Further, the sense of discomfort in hearing can be reduced by recording each signal output from the stereo signal processing apparatus 100 on a predetermined recording medium and using the recording medium as a recording medium on which the above input signals are recorded. Sound can be generated. The recording at that time can be performed using a known method or means, and description thereof will be omitted.
[0029]
Furthermore, each signal output from the stereo signal processing apparatus 100 or each signal obtained based on the above-described recording medium on which each signal output from the stereo signal processing apparatus 100 is recorded is converted into a known broadcast method or broadcast. Similarly, when broadcasting using means, it is possible to generate sound with a reduced sense of discomfort in the sense of hearing. Description of known broadcasting methods or means is omitted.
[0030]
As described above, the stereo signal processing apparatus according to the first embodiment of the present invention separates the input signal into the mid-low frequency component signal and the high frequency component signal, and the rear speaker receives the high frequency component signal. Since the rear speaker only needs to reproduce the high-frequency component signal for output, a large speaker is not required.
[0031]
In addition, the minimum frequency of a signal to be reproduced using a rear speaker is 1.5 kHz or higher, which is extremely higher than the lower limit of the audible frequency. Smaller speakers can be used. Furthermore, the front and rear speakers are responsible for the mid- and low-frequency sounds of the rear channel sound reproduction signal, and the virtual sound image is synthesized at a position symmetrical to the front and rear of the rear speaker. It is possible to output sound with a sense of incongruity reduced in terms of sound quality and hearing.
[0032]
【The invention's effect】
As described above, the present invention can realize a stereo signal processing device capable of generating a signal for reproducing a sound with a reduced sense of incongruity even when a small rear speaker is used.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic block configuration of a stereo signal processing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram schematically showing an arrangement of speakers from which signals are output from the stereo signal processing apparatus according to the first embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 1st high-pass filter 12 1st low-pass filter 13 1st compensation filter 14 2nd compensation filter 21 2nd high-pass filter 22 2nd low-pass filter 23 3rd compensation filter 24 4th compensation filter 30 1st adder 40 2nd adder 100 Stereo signal processor 201 Right speaker 202 Left speaker 203 Center speaker 204 Right rear speaker 205 Left rear speakers 206, 207 Virtual speaker

Claims (2)

A right channel assigned to a right speaker disposed at a position that forms a first angle smaller than 90 degrees clockwise with respect to the front direction of the listening position of a circumference of a predetermined radius centered on the listening position; Left channel assigned to the left speaker arranged at a position that forms the first angle counterclockwise with respect to the front direction of the listening position of the listening position, counterclockwise with respect to the front direction after the listening position on the circumference A right rear channel assigned to a right rear speaker arranged at a position that is smaller than 90 degrees and larger than the first angle in the direction, and with respect to the front direction after the listening position on the circumference The sound reproduction signal for four or more channels including the left rear channel assigned to the left rear speaker disposed at the position forming the second angle in the clockwise direction is processed. In the stereo signal processing apparatus,
A first filter for dividing the sound reproduction signal for the right rear channel into an SR high-frequency component signal equal to or higher than a reference frequency that is a predetermined audible frequency and an SR medium-low frequency component signal lower than the reference frequency; A second filter for dividing the sound reproduction signal for the left rear channel into an SL high-frequency component signal equal to or higher than the reference frequency and an SL mid-low frequency component signal lower than the reference frequency;
A first compensation filter for generating a corrected SRR middle low-frequency component signal by correcting the SR middle low-frequency component signal with a head related transfer function when output from the right speaker;
A second compensation filter for generating a corrected SRL middle low-frequency component signal by correcting the SR middle low-frequency component signal with a head-related transfer function when output from the left speaker;
A third compensation filter for generating a corrected SLR mid-low frequency component signal by correcting with the head related transfer function when the SL mid-low frequency component signal is output from the right speaker;
A fourth compensation filter for generating a corrected SLL mid-low frequency component signal by correcting the SL mid-low frequency component signal with a head related transfer function when output from the left speaker;
A first adder for adding the right channel sound reproduction signal, the corrected SRR mid-low frequency component signal, and the corrected SLR mid-low frequency component signal to output as the right channel sound reproduction signal; A second adder for adding the left channel sound reproduction signal, the corrected SRL mid-low frequency component signal, and the corrected SLL mid-low frequency component signal to output as the left channel sound reproduction signal And
Outputting the SR high-frequency component signal as a sound reproduction signal for the right rear channel, and outputting the SL high-frequency component signal as a sound reproduction signal for the left rear channel;
The first compensation filter and the second compensation filter are configured to localize the SR middle low-frequency component signal output from the right speaker to a front-rear symmetrical position of the right rear speaker with respect to the listening position,
The third compensation filter and the fourth compensation filter are configured to localize the SL middle low-frequency component signal output from the left speaker at a front-rear symmetrical position of the left rear speaker with respect to the listening position. A stereo signal processing device.   2. The stereo signal processing apparatus according to claim 1, wherein the reference frequency is any frequency between 1.5 kHz and 6 kHz and is variable.

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