The present invention relates to a center channel positioning apparatus. In particular, the present invention relates to a center channel positioning apparatus which causes sound based on a center channel sound signal to be outputted from a left speaker and a right speaker.
Conventionally, in a surround system such as a 5.1-channel system, three speakers of a left speaker, a right speaker, and a center speaker are located in front of a listener, and it is desirable that the center speaker is located between the left speaker and the right speaker. However, since a display apparatus such as a television set is located between a left speaker and a right speaker, it is difficult that a center speaker is located between a left speaker and a right speaker.
Therefore, a surround system is proposed, in which a center speaker is omitted, and a center channel positioning based on a center channel sound signal is virtually formed by a left speaker and a right speaker.
In such a surround system mentioned above, a case will be mentioned, in which a center speaker is located in front of a listener position, and a left speaker is located with an angle of 30° in the left direction from the listener position, and a right speaker is located with an angle of 30° in the right direction from the listener position. A frequency characteristic in the case where a center channel sound signal is reproduced by left and right speakers is compared with a frequency characteristic in the case where the center channel sound signal is actually reproduced by a center speaker. In the case where a center channel sound signal is reproduced by left and right speakers, there is a problem that a gain is lowered by approximately 10 dB at a frequency band of approximately 1 to 4 kHz.
An apparatus for solving the above problem is shown, for example, in Patent Document No. 1.
In a reproducing apparatus disclosed in Patent Document No. 1 mentioned above, after a center channel sound signal is processed by an equalizer in such a way that its frequency characteristic is corrected, the resultant signal is reproduced by left and right speakers. A characteristic of the equalizer is one which causes a frequency characteristic of a head transfer function in the case where a center channel sound signal is reproduced by left and right speakers to be equal to a frequency characteristic of a head transfer function in the case where the center channel sound signal is actually reproduced by a center speaker.
Concretely, at a frequency band of approximately 1 to 4 kHz, a level of frequency characteristic in the case where a center channel sound signal is reproduced by left and right speakers becomes lower than a level of frequency characteristic in the case where the center channel sound signal is actually reproduced by a center speaker, by approximately 10 dB. Therefore, an equalizer has a characteristic which causes a gain to be raised by approximately 10 dB at a frequency band of approximately 1 to 4 kHz.
In a reproducing apparatus disclosed in Patent Document No. 1 mentioned above, a correction characteristic of an equalizer is set on the assumption that in the case where a left speaker is located with an angle of 30° in the left direction from a listener position, and a right speaker is located with an angle of 30° in the right direction from the listener position, a center channel sound signal is heard at the listener position.
Therefore, in the case where a center channel sound signal is heard at a position apart from an original listener position, only a component of a frequency band of approximately 1 to 4 kHz for which a gain has been raised by approximately 10 dB, of components of a center channel sound signal, is heard. As a result, strange feeling in sound quality is caused to a listener.
The present invention has been achieved in view of the above problem, it is an example of an object of the invention to provide a center channel positioning apparatus which does not cause strange feeling in sound quality even at a position apart from an original listener position.
In order to solve the above problem, the invention according to claim 1 relates to a center channel positioning apparatus, comprising:
Referring now to
In
In
The AV amplifier device 12 includes a decoder 16. The digital stream signal 100 is supplied to the decoder 16, and the decoder 16 decodes a signal of 5.1 ch. Surround signals SL, SR, and SW from the decoder 16 are supplied through DA conversion units 18, 20, and 22 to amplifier units 24, 26, and 28, respectively. Outputs from the amplifier units 24, 26, and 28 are supplied to surround speakers 30, 32, and 34 in the speaker unit 14.
The decoder 16 outputs a left sound signal L, aright sound R, and a center channel sound signal C. The left sound signal L, and the right sound R are supplied to a left sound signal combining unit 36, and a right sound signal combining unit 38, respectively. The center channel sound signal C is supplied to a sound signal processing unit 40, and based on the center channel sound signal C, the sound signal processing unit 40 produces a left sound signal for center channel positioning CL, and a right sound signal for center channel positioning CR, and supplies the sound signals CL and CR to the sound signal combining units 36, and 38, respectively. A structure of the sound signal processing unit 40 will be described later.
The left sound signal combining unit 36 combines the left sound signal L with the left sound signal for center channel positioning CL, and supplies a left combined sound signal 102 through a DA conversion unit 42, and an amplifier unit 44 to a left speaker 46 in the speaker unit 14. Similarly, the right sound signal combining unit 38 combines the right sound signal R with the right sound signal for center channel positioning CR, and supplies a right combined sound signal 104 through a DA conversion unit 48, and an amplifier unit 50 to aright speaker 52 in the speaker unit 14.
In the AV amplifier device 12, a block denoted by reference numeral 54 is composed of a processor such as a DSP, or a CPU which performs a digital process.
In a center channel positioning apparatus shown in
Hereinafter, the sound signal processing unit 40 will be described.
In
In
As mentioned above, by shifting a phase of the right sound signal for center channel positioning CR, sound based on a center channel sound signal C is outputted from a left speaker 46, and a right speaker 52.
Although a phase of the right sound signal for center channel positioning CR is shifted in the sound signal processing unit 40 shown in
As mentioned above, the sound signal processing unit 40 shifts a phase of the right sound signal for center channel positioning CR, or a phase of the left sound signal for center channel positioning CL. Here, the sound signal processing unit shifts a phase based on a processing coefficient. The processing coefficient may be fixed or variable. Hereinafter, a case where the processing coefficient is variable will be described.
The processing coefficient depends on an arrangement of a speaker, such as a space between a left speaker and a right speaker, a distance from a speaker to a listener. It is possible to change a processing coefficient based on an arrangement of a speaker. An arrangement for such a change is shown in
In
In
Now, in
In an arrangement of speaker in
In the case where the left speaker 46 and the right speaker 52 are arranged as shown in
As mentioned above,
Hereinafter, a process of deriving an amount of delay of phase at each band shown in
In
In
In
On the other hand, around an area of 2 KHz, there exist two phases whose degree of a center channel positioning is 0 degree. That is, around an area of 2 KHz, in two areas 72 (a degree of phase: π(pi) radian) and 74 (a degree of phase: 0 radian) which are denoted by a broken line, a degree of center channel positioning is 0 degree. Therefore, it is possible to select the two areas 72 (a degree of phase: π(pi) radian) and 74 (a degree of phase: 0 radian). However, the area 72 (a degree of phase: π(pi) radian) is selected for the following reason.
First,
A bar-shaped indicator 76 on the right side in
In
Now,
A bar-shaped indicator 82 on the right side in
In
From graphs of
(a degree of center positioning)=(1/(an absolute value of the difference in level between both ears))*(the sum of power at both ears)*(the weight of phase)
The degree of center positioning is calculated for each band. When a phase is changed for each band, an absolute value of the difference in level between both ears, and the sum of power at both ears change. At this time, (1/(an absolute value of the difference in level between both ears), and (the sum of power at both ears) are set to be normalized in such a way that they change between 0 and 1, respectively.
Further, the weight of phase is added, because it is desirable that a change of phase is as small as possible. That is, the weight of phase is set to change linearly with a phase in such a way that the weight of phase is a value of 1 when a phase is 0 radian, and the weight of phase is a value of 0 when a phase is 2π(pi) radian.
As mentioned above, since (1/(an absolute value of the difference in level between both ears)), (the sum of power at both ears), and (the weight of phase) change between 0 and 1, a degree of center positioning changes between 0 and 1.
Now,
A bar-shaped indicator 82 on the right side in
As one embodiment of the present invention, a center channel positioning apparatus is used only for a band of frequency of approximately 1 KHz to approximately 4 KHz. Hereinafter, this embodiment will be described hereinafter.
As mentioned in an column of “BACKGROUND ART” of this specification, in a frequency band of approximately 1 to approximately 4 kHz, a level of frequency characteristic in the case where a center channel sound signal is reproduced by left and right speakers becomes lower than a level of frequency characteristic in the case where the center channel sound signal is actually reproduced by a center speaker, by approximately 10 dB. Therefore, in the embodiment, a center channel positioning apparatus is used only for a band of frequency of approximately 1 KHz to approximately 4 KHz. Consequently, strange feeling in sound quality is not caused for a listener.
This embodiment has an advantageous effect that strange feeling in sound quality is not caused for a listener, because an arrangement is one in which a phase is changed, even if a center channel sound signal is heard at a position apart from an original listener position, as compared with an arrangement mentioned in Patent document No. 1 in which a gain is raised, i.e., a frequency characteristic is changed.
The present invention is not limited to the foregoing embodiment. The embodiment is illustrative. Anything having substantially the same configuration and producing similar effects as the technical ideas described in the scope of claims of the present invention is included in the technical scope of the present invention.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/073201 | 11/30/2007 | WO | 00 | 5/19/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/069228 | 6/4/2009 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
20030031332 | Tatsuta et al. | Feb 2003 | A1 |
20040175001 | Sakagami et al. | Sep 2004 | A1 |
20050013442 | Ohta | Jan 2005 | A1 |
20060080089 | Vierthaler et al. | Apr 2006 | A1 |
20070002971 | Purnhagen et al. | Jan 2007 | A1 |
20070127733 | Henn et al. | Jun 2007 | A1 |
20070258607 | Purnhagen et al. | Nov 2007 | A1 |
Number | Date | Country |
---|---|---|
63-269900 | Nov 1988 | JP |
3-195199 | Aug 1991 | JP |
2003-061198 | Feb 2003 | JP |
2004-266604 | Sep 2004 | JP |
2005-039311 | Feb 2005 | JP |
Number | Date | Country | |
---|---|---|---|
20100272269 A1 | Oct 2010 | US |