JP2003244798A - Stereo signal processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stereo signal processing apparatus capable of performing acoustic reproduction so as to reduce a sense of incongruity in listening even when a small-sized rear speaker is in use. <P>SOLUTION: The stereo signal processing apparatus for processing four or more channels of acoustic reproduction signals including left and right channels assigned to left and right speakers and left and right rear channels assigned to left and right rear speakers, is configured to include: means 11, 12, 21, and 22 for separating the acoustic reproduction signals for a couple of left and right rear channel signals into left and right high frequency signals with a frequency band including a prescribed audible frequency or over and left and right medium and low frequency signals with a frequency band including frequencies less than the prescribed audible frequency; and means 13, 14, 23, 24, 30, and 40 for assigning a couple of left and right high frequency signals to a corresponding left and right rear channels and superimposing a couple of the left and right medium and low frequency signals on the acoustic reproduction signals for left and right channels to assign the superimposed signals to the channels, and the signals assigned to each channel is outputted. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stereo signal processing device, and more particularly, to stereo digital broadcasting, DVD (Di
The present invention relates to a stereo signal processing device for processing digital signals and the like obtained from a recording medium such as a digital versatile disk).

[0002]

2. Description of the Related Art Conventionally, a so-called 5.1-channel stereo device has been known as a device for enjoying a highly realistic three-dimensional sound. This is the use of DVDs and BS
(Broadcasting Satellite) Since it became possible to receive digital broadcasting,
This is due to the availability of 5.1-channel stereo audio signals as well as 2-channel stereo audio signals.

Here, an acoustic channel in 5.1-channel stereo is composed of 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. Standard playback device excludes low-frequency emphasis channel 5
The acoustic signals of one channel are reproduced as they are by the five speakers 201-205 shown in FIG. For the low-frequency emphasis channel, the speaker position for the low-frequency emphasis channel is free.

In a limited space such as a home, it is often difficult to use a speaker having a wide band for all five channels in terms of securing a place for the speaker. In practice, the following reproducing method is used. Is used. A first method is a method of using rear speakers 204, 205 on the rear side that are smaller than those of the left and right speakers 201, 202 on the front side, and supplementing and reproducing a lacking low-frequency component sound through a subwoofer. .

The second method is a so-called front surround method in which a speaker to be output from the rear speaker is reproduced only by the two speakers in the front without providing any speaker in the rear. In this method, not only the center channel acoustic signal is distributed to the left and right channels, but also the left and right rear channel acoustic signals are subjected to the inverse filter processing of the head related transfer function so that the virtual sound sources are located at the left rear and the right rear. Is synthesized. In other words, the rear speaker is not actually installed, and the listener can hear the sound in the place.

[0006]

However, in the first conventional method, the timbre difference between the sound from the small rear speaker and the sound from the front speaker is apt to be large, and the feeling of movement and the feeling of envelopment of the sound are likely to increase. There was a problem in that a sense of discomfort was likely to occur. This tendency becomes more remarkable as the size of the rear speaker is reduced.

Further, the second method has a problem that the effect of being surrounded by the sound from the original four sides of the 5-channel stereo is diminished because the sound cannot actually be heard from the rear. This is a drawback common to the methods that use the head-related transfer function.Since the head-related transfer function used in the design of the inverse filter is different from the head-related transfer function of the viewer himself, it has a significant role in the perception of the front and back of the sound image. This is because the reproduction of the range component is incorrect. It is theoretically possible to use the viewer's own as the head-related transfer function, but it is unrealistic when targeting an unspecified large number of users such as broadcasting.

The present invention has been made to solve the above problems, and an object of the present invention is to generate a signal for reproducing a sound in which discomfort in hearing is reduced even when a small rear speaker is used. It is to provide a stereo signal processing device capable of

[0009]

In view of the above points, the invention according to claim 1 is the right channel assigned to the right speaker, the left channel assigned to the left speaker,
A stereo signal processing device for processing sound reproduction signals for four or more channels including a right rear channel assigned to a right rear speaker and a left rear channel assigned to a left rear speaker, wherein the right rear channel Filter for dividing a sound reproduction signal for audio into an SR high frequency component signal having a reference frequency equal to or higher than a predetermined audible frequency and an SR mid-low frequency component signal having a frequency lower than the reference frequency, and the left rear channel A second filter for dividing the sound reproduction signal into an SL high-frequency component signal having a frequency higher than the reference frequency and an SL mid-low frequency component signal having a frequency lower than the reference frequency; A first compensation filter for correcting the head related transfer function when the signal is output from the right speaker to generate a corrected SRR middle low frequency component signal; Wherein R in the low-frequency component signal, corrected by correcting the head-related transfer function when the output from the left speaker S
A second compensating filter for generating an RL middle and low range component signal, and a corrected SLR middle and low range component by correcting the head related transfer function when the SL middle and low range component signal is output from the right speaker. A third compensation filter for generating the signal,
A fourth compensation filter for correcting the head-related transfer function when the SL low-mid frequency component signal is output from the left speaker to generate a corrected SLL mid-low frequency component signal, and the fourth compensation filter for the right channel. A first adder for adding the sound reproduction signal, the SRR middle low-frequency component signal, and the SLR middle low-frequency component signal to output as a sound reproduction signal for the right channel; and sound for the left channel Playback signal and SR
A second adder for adding the L middle / low frequency component signal and the SLL middle / low frequency component signal and outputting as a sound reproduction signal for the left channel; and the SR high frequency component signal for the right channel. Output as a sound reproduction signal for the rear channel,
The SL high frequency component signal is output as a sound reproduction signal for the left rear channel. With this configuration, the front speaker takes charge of the mid- and low-range sounds,
Since a virtual sound image is synthesized at a position that is symmetrical to the front and rear of the rear speaker, it is difficult to separate the high and middle low-frequency sound images, and it is possible to output sound with less discomfort in terms of sound quality and hearing. A signal processing device can be realized.

The invention according to claim 2 provides the invention according to claim 1, wherein the reference frequency is from 1.5 kHz to 6 kHz.
It has a configuration in which any frequency equal to or lower than z and which is variable. With this configuration, the reference frequency is 1.5k
Since it can be adjusted within the range of Hz to 6 kHz, it is possible to realize a stereo signal processing device capable of responding to individual differences of viewers, size and type of usable speakers, environment and the like.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A stereo signal processing apparatus according to a first embodiment of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention utilizes that the sense of front and back of the sound image perceived by the viewer is formed based on the sound in the frequency band of approximately 6 kHz or more. In other words, it is based on the fact that low- and mid-range sounds below approximately 6 kHz do not play an important role in perception before and after a sound image.

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 device 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, first to fourth compensation filters 13 and 1,
4, 23, 24 and the first and second adders 30, 40
Composed by.

As shown in FIG. 1, the stereo signal processing apparatus 100 has an input R signal which is an input signal for the right channel, an input L signal which is an input signal for the left channel, and an input signal for the center channel. An input C signal, an input SR signal that is an input signal for the right rear channel, and an input SL signal that is an input signal for the left rear channel are input. FIG. 2 is a diagram schematically showing an array of speakers to which signals are output from the stereo signal processing device 100.
The five speakers shown in FIG. 2 are the left and right speakers 201, 2.
02, center speaker 203, and left and right rear speakers 204, 205.

The first HPF 11 receives the input SR signal as an input, passes a signal having a frequency component of a predetermined frequency or higher in the input SR signal, and outputs the output SR signal obtained from the stereo signal processing device 100. It is a means for outputting. Below, the above-mentioned predetermined frequency is referred to as a reference frequency, and the above-mentioned 6 kHz can be used as the reference frequency, for example. A signal having a frequency band component equal to or higher than the reference frequency is referred to as a high frequency band component signal, and a signal having a frequency band component lower than the reference frequency is also referred to as a middle / low frequency band component signal.

The first LPF 12 receives the input SR signal as an input, passes a signal having a frequency component of the input SR signal which is equal to or lower than the reference frequency (hereinafter, referred to as SR mid-low range component signal), and first, It is means for outputting to the second compensation filters 13 and 14. As a result, the input SR signal is separated by the first HPF 11 and the first LPF 12 into two frequency component signals with the reference frequency as a boundary.

The first compensation filter 13 includes a first LPF.
The SR middle and low frequency component signals output from 12 are input, and S
A correction S, which is a signal obtained by performing correction processing on the R mid-low frequency component signal in consideration of the head related transfer function of the sound,
It is means for outputting the RR middle and low band component signal to the first adder 30. In the correction processing performed by the first compensation filter 13 in consideration of the head related transfer function of the sound, the correction processing is performed in consideration of the head related transfer function when the sound is output from the right speaker 201.

The second compensation filter 14 includes a first LPF.
The SR middle and low frequency component signals output from 12 are input, and S
A correction S, which is a signal obtained by performing correction processing on the R mid-low frequency component signal in consideration of the head related transfer function of the sound,
It is a means for outputting the RL middle and low band component signal to the second adder 40. In the correction process performed by the second compensation filter 14 in consideration of the head related transfer function of the sound, the correction process is performed in consideration of the head related transfer function output from the left speaker 202.

The second HPF 21 receives the input SL signal as an input, passes the signal having a frequency component higher than the reference frequency of the input SL signal, and outputs the output SL obtained by passing the signal.
It is means for outputting a signal from the stereo signal processing device 100. As a result, the second HPF 21 outputs a signal having the same frequency component as that of the first HPF 11.

The second LPF 22 receives the input SL signal as an input, passes a signal having a frequency component of the input SL signal which is equal to or lower than the reference frequency (hereinafter, referred to as SL mid-low range component signal), and thirdly, It is means for outputting to the fourth compensation filters 23, 24. As a result, the input SL signal is input to the input SR signal by the second HPF 21 and the second LPF 22.
The signal is separated into two frequency component signals with the same reference frequency as that of the signal as a boundary.

The third compensation filter 23 has a second LPF.
The SL mid-low frequency component signal output from 22 is input, and S
A correction process, which is a signal obtained by performing a correction process on the L middle and low frequency component signal in consideration of the head related transfer function of the sound,
It is means for outputting the LR middle and low range component signal to the first adder 30. In the correction processing performed by the third compensation filter 23 in consideration of the head related transfer function of the sound, the correction processing is performed in consideration of the head related transfer function when the sound is output from the right speaker 201.

The fourth compensation filter 24 includes a second LPF.
The SL mid-low frequency component signal output from 22 is input, and S
A correction process, which is a signal obtained by performing a correction process on the L middle and low frequency component signal in consideration of the head related transfer function of the sound,
It is a means for outputting the LL middle and low range component signal to the second adder 40. In the correction process performed by the fourth compensation filter 24 in consideration of the head related transfer function of the sound, the correction process is performed in consideration of the head related transfer function output from the left speaker 202.

The first adder 30 receives the input R signal, the corrected SRR mid-low range component signal output from the first compensation filter 13, and the corrected SLR mid-low range component output from the third compensation filter 23. It is means for adding signals and outputting the signal obtained by the addition as an output R signal from the stereo signal processing device 100.

The second adder 40 receives the input L signal, the corrected SRL mid-low range component signal output from the second compensation filter 14, and the corrected SLL mid-low range component output from the fourth compensation filter 24. It is means for adding signals and outputting the signal obtained by the addition as an output L signal from the stereo signal processing device 100.

The input C signal, which is the input signal for the center channel, is directly output from the stereo signal processing apparatus 100 as the output C signal. Therefore, input C
The signal only passes through the stereo signal processing device 100 and is the same signal as the output C signal.

Further, the first for compensating the head related transfer function
In the fourth compensation filters 13, 14, 23, and 24, the corrected SRR mid-low range component signal and the corrected SLR mid-low range component signal are reproduced by the right speaker 201, and the corrected SRL mid-low range component signal and the corrected SLL middle When the low frequency component signal is reproduced by the left speaker 202, the SR middle low frequency component signal and the SL middle low frequency component signal are designed to be localized on the virtual speakers 206 and 207, respectively. Here, a method for localizing is known, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-189399.

Here, the virtual speaker 206 is the right rear speaker 204, and the virtual speaker 207 is the left rear speaker 2.
It is assumed that there is a front-back symmetrical positional relationship with each other. Since the middle and low range sounds are likely to be erroneously recognized with respect to the front-rear relationship of the sound image, even if the virtual speakers 206 and 207 are in the front position, the sound of the high frequency band component that influences the front-back feeling of the sound image is generated. , And the sound reproduction signals for the left and right rear channels are output from the rear speakers 204 and 205 that are symmetrical with respect to the virtual speakers 206 and 207.
As a whole, they are recognized at the positions of the rear speakers 204 and 205, respectively.

The reference frequency, which is the reference of the frequency of the sound that influences the sense of front and back of the sound image, is approximately 6 kHz in the above description, but it should be adjusted according to the individual differences of the viewers, the size and type of speakers that can be used, the environment, etc. To allow
The reference frequency may be variable and adjustable within the range of 1.5 kHz to 6 kHz.

Also, each signal output from the stereo signal processing apparatus 100 is recorded in a predetermined recording medium, and the recording medium is used as a recording medium in which each of the input signals described above is recorded. A reduced sound can be produced. Recording at that time can be performed using a known method or means, and description thereof will be omitted.

Further, each signal output from the stereo signal processing device 100 or the stereo signal processing device 10
Similarly, when each signal obtained based on the above-mentioned recording medium in which each signal output from 0 is recorded is broadcast using a known broadcasting method or broadcasting means, a sound in which discomfort in hearing is reduced is similarly generated. Can be generated. Descriptions of known broadcasting methods or means are omitted.

As described above, the stereo signal processing device according to the first embodiment of the present invention separates the input signal into the middle low frequency component signal and the high frequency component signal, and the rear speaker has the high frequency component. Since the rear speaker outputs only the high-frequency component signal in order to output the component signal, a large speaker is not required.

Further, the minimum frequency of the signal to be reproduced using the rear speaker is 1.5 kHz or more, which is extremely high compared to the lower limit of the audible frequency, so that it is possible to reproduce from the subwoofer only in the low frequency range which has been frequently used conventionally. By comparison, smaller speakers can be used. Furthermore, the front speaker takes charge of the low- and middle-range sounds of the rear-channel sound reproduction signal, and the virtual sound image is synthesized at a position symmetrical to the front and rear speakers, so that the separation of the high- and middle- and low-frequency sound images is less likely to occur.
It is possible to output sound with less discomfort in terms of sound quality and hearing.

[0032]

As described above, the present invention realizes a stereo signal processing device capable of generating a signal for reproducing a sound in which a sense of discomfort is reduced even when a small rear speaker is used. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic block configuration of a stereo signal processing device according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing an array of speakers to which signals are output from the stereo signal processing device according to the first embodiment of the invention.

[Explanation of symbols]

11 First high-pass filter 12 First low pass filter 13 First compensation filter 14 Second compensation filter 21 Second high-pass filter 22 Second low pass filter 23 Third Compensation Filter 24 Fourth Compensation Filter 30 First adder 40 Second adder 100 stereo signal processor 201 Right speaker 202 Left speaker 203 Center speaker 204 Right rear speaker 205 Left rear speaker 206, 207 Virtual speaker

Claims (2)

[Claims] 1. Four or more channels including a right channel assigned to a right speaker, a left channel assigned to a left speaker, a right rear channel assigned to a right rear speaker, and a left rear channel assigned to a left rear speaker. In the stereo signal processing device for processing the sound reproduction signal for the channel, the sound reproduction signal for the right rear channel is set to an SR high frequency component signal of a reference frequency equal to or higher than a predetermined audible frequency and less than the reference frequency. A first filter for splitting into an SR mid-low range component signal and the sound reproduction signal for the left rear channel,
A second filter for dividing into an SL high-frequency component signal having a frequency equal to or higher than the reference frequency and an SL mid-low frequency component signal having a frequency lower than the reference frequency, and the SR mid-low frequency component signal output from the right speaker. In the case, the head related transfer function is corrected to correct S
A first compensating filter for generating an RR middle and low range component signal, and a corrected SRL middle and low range component by correcting the head related transfer function when the SR middle and low range component signal is output from the left speaker A second compensation filter for generating a signal,
A third compensation filter for correcting the head related transfer function when the SL middle and low frequency component signal is output from the right speaker to generate a corrected SLR middle and low frequency component signal;
A fourth compensating filter for correcting the head related transfer function when the L speaker is output from the left speaker to generate a corrected SLL middle and low frequency component signal, and the sound for the right channel A first adder for adding the reproduction signal, the SRR middle low-frequency component signal, and the SLR middle low-frequency component signal to output as a sound reproduction signal for the right channel; and sound reproduction for the left channel. A second adder for adding a signal, the SRL mid-low range component signal, and the SLL mid-low range component signal and outputting as a sound reproduction signal for the left channel, the SR high-range component signal Is output as the sound reproduction signal for the right rear channel, and the SL high frequency component signal is output as the sound reproduction signal for the left rear channel. 2. The reference frequency is 1.5 kHz or more and 6 kHz.
The stereo signal processing apparatus according to claim 1, wherein the stereo signal processing apparatus has a frequency of any one of Hz or less and is variable.