JPH1042398A - Surround reproducing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the moving feeling of a surround sound image without increasing processing amount for sound image control. SOLUTION: This surround reproducing method makes pseudo reproduction of plural surround signals by plural speakers SPL, SPR and SPC which are in front. A sound image central position sθ in accordance with an ideal reproducing position and the size of power or amplitude of each sound signal is searched, one synthetic surround signal SCM is generated by synthesizing plural surround signals, filter factors h1 and h2 of FIR filters 16 and 17 are selected so that the synthetic surround signal SCM may be reproduced at the sound image central position sθ, and the sound image position of the synthetic surround signal SCM is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surround reproduction method and apparatus for reproducing a plurality of surround signals in a pseudo manner using a plurality of front speakers.

[0002]

2. Description of the Related Art Conventionally, in the audio-visual world, television screens have been devised to produce richer sense of realism and power by adopting a larger, higher-definition television and a surround sound system. I have.

For example, the Dolby surround system AC-3, the moving image compression standard MPEG, and the like are often used in LD software and DVD software. In the surround system, for example, two left and right speakers for surround arranged rearward are used in addition to two speakers arranged left and right or three speakers in addition to the center.

[0004] However, in general households and the like,
In many cases, the two rear speakers are not installed because the conditions are limited by room conditions. Assuming such a case, conventionally, there has been proposed a method of reproducing sound of the surround system using only two or three speakers arranged in front.

FIG. 5 is a block diagram of a conventional surround reproduction system 80. It should be noted that the figure mainly shows only a part of signal processing related to sound image control. The same applies hereinafter.

In FIG. 5, a surround reproduction system 8
0, the front (front) left channel signal FLin,
The front right channel signal FRin, the rear (surround) left channel signal SLin, and the rear right channel signal S
Four audio signals of Rin are input.

The front left channel signal FLin and right channel signal FRin are reproduced by the left and right speakers SPL and SPR without performing sound image control.

The rear left channel signal SLin and right channel signal SRin are added to each other to generate a one-channel composite surround signal SCM,
The sound image control is performed by the R filters 1 and 2 respectively, and the front left channel signal FLin or the right channel signal FRi
n, and is reproduced by the front left and right speakers SPL and SPR.

Thus, the left and right speakers SPL, S
The sound image of the surround signal is formed directly behind the listener heading to PR. The FIR filter may be replaced by an IIR filter.

FIG. 6 is a block diagram of another example of a conventional surround reproduction system 80a. In the surround reproduction system 80a shown in FIG. 6, sound image control is performed on the surround left channel signal SLin and the right channel signal SRin by independent FIR filters 1 to 4 to generate sound images of the surround signals in a plurality of directions.

According to such conventional surround reproduction systems 80 and 80a, a surround signal whose sound image is controlled is reproduced from the speakers SPL and SPR arranged in front, and a pseudo surround effect is obtained.

[0012]

However, according to the above-described surround reproduction system 80, the surround sound image is fixed in one direction, and the sense of movement of the surround sound is impaired. Further, since the position directly behind the listener is the most difficult direction to control, a clear surround sound image cannot be obtained when the sound image position is formed right behind.

According to the latter surround reproduction system 80a, since the processing of each surround signal is independent, a sense of stereo and movement of the surround sound can be obtained, but the amount of processing for controlling the sound image by the FIR filter increases. It is twice as large as the former. Therefore, it is necessary to use a high-speed DSP, which is expensive.

In any case, since the generated sound image position is fixed, the sound image direction becomes blurred when mixed with other stereo sound or center sound, and the effect may be reduced.

The present invention has been made in view of the above-described problems, and provides a surround reproduction method and apparatus capable of obtaining a sense of movement of a surround sound image without increasing the processing amount for sound image control. The purpose is to:

[0016]

According to a first aspect of the present invention, there is provided a surround reproduction method for reproducing a plurality of surround signals in a pseudo manner by a plurality of front speakers, wherein the plurality of surround signals are reproduced. A ratio between the magnitudes of the power and the amplitude is obtained, and the overall sound image position of the surround signal is controlled according to the ratio.

According to a second aspect of the present invention, a sound image center position corresponding to an ideal reproduction position and power or amplitude of each of the surround signals is obtained, and the plurality of surround signals are combined to form one combined surround signal. A signal is generated, and a sound image position of the synthesized surround signal is controlled so that the synthesized surround signal is reproduced at the sound image center position.

According to a third aspect of the present invention, there is provided a surround reproducing apparatus for reproducing a plurality of surround signals in a pseudo manner by a plurality of front speakers, wherein an ideal reproducing position and power or amplitude of each surround signal are provided. Means for determining a sound image center position corresponding to the size of the sound source, means for synthesizing the plurality of surround signals to generate one synthesized surround signal, and such that the synthesized surround signal is reproduced at the sound image center position. Means for controlling a sound image position of the synthesized surround signal.

According to a fourth aspect of the present invention, there is provided an apparatus for calculating a center position of a sound image in accordance with an ideal reproduction position and power or amplitude of each of the surround signals, and synthesizing the plurality of surround signals. Synthesizing means for generating one synthesized surround signal, a plurality of FIR filters for inputting as an input signal to each speaker so that the synthesized surround signal is reproduced from a plurality of speakers in front of the FIR filter, Coefficient varying means for varying a filter coefficient according to the sound image center position,
Is configured.

According to a fifth aspect of the present invention, the position calculating means calculates an average value of power or amplitude of each of the surround signals, and the ideal reproduction position of each of the surround signals. And a position determining means for calculating a weighted average of the respective surround signals by the average value to obtain the sound image center position.

The average value calculating means calculates the average value of the power or amplitude of each surround signal, for example, at regular intervals. The position determining means calculates a weighted average based on an average value of each surround signal with respect to an ideal reproduction position of each surround signal to obtain a sound image center position.
That is, the sound image position at the time of reproducing the synthesized surround signal is determined using the average value of each surround signal.

As the coefficient variable means, for example, a coefficient buffer is used in which filter coefficients used for calculation in the FIR filter are determined and stored in advance corresponding to each sound image center position. In this case, a filter coefficient corresponding to the center position of the sound image output from the position determining means is read from the coefficient buffer and transferred as a coefficient of the FIR filter. In determining the filter coefficients of the coefficient buffer, various known methods are used.

In the present invention, the front speakers include headphones.

[0024]

FIG. 1 is a block diagram showing the configuration of a surround reproduction system 1 according to the present invention. FIG. 2 is a diagram for explaining a surround signal. FIG. 3 is a diagram showing an example of a coefficient buffer 15. 4 is the filter coefficient h of the FIR filter
FIG. 3 is a diagram for explaining a method for determining l and hr.

In FIG. 1, a surround reproduction system 1
Is a synthesizing unit 11, power average calculating units 12, 13, a sound image position determining unit 14, a coefficient buffer 15, an FIR filter 1
6, 17, synthesis units 18 and 19, and speakers SPL and S
It is composed of PR, SPC, etc. Although not shown, circuits or functions necessary for the sound reproduction system, such as a preamplifier, a power amplifier, and various adjustment circuits, are naturally provided.

The surround reproduction system 1 reproduces, for example, an AC-3 5-channel signal, which is a Dolby surround system. The surround playback system 1 includes a front (front) left channel signal FLin, a right channel signal FRin, a center channel signal FCin,
Five audio signals of the rear (surround) left channel signal SLin and right channel signal SRin are input. These five channel signals are transmitted to the three front speakers SPL and SPL.
Playback is performed by PR and SPC. However, the center speaker SPC reproduces only the center channel signal.

The input audio signal may be encoded audio data in the frequency domain or compressed data obtained by compressing the audio data. In that case, a decompressor that performs decompression processing on input compressed data, an IMDCT (inverse modified discrete cosine transform) that inversely transforms frequency domain data into a time domain signal, or an IDFT (inverse discrete Fourier transform) ) May be used in combination.

First, the surround left channel signal SLi
n and the right channel signal SRin will be described. FIG.
, The speakers SPL, SP in front of the listening position PL
R and SPC are arranged. Each surround signal is ideally reproduced by each speaker SPS arranged behind the listening position PL.

For example, the above-described two-channel surround signals SL and SR in AC-3 are speakers SPS arranged at an arrangement angle θ of 30 ° or 150 °, respectively.
1, ideally reproduced by SPSi. In this case, the ideal reproduction positions of the surround signals SL and SR are 30 ° and 15 °, which are the respective arrangement angles θ.
0 °.

In a surround system other than the above-described AC-3, the ideal reproduction position of the surround signal may have an arrangement angle θ different from the above. Also, a surround signal of three channels or four or more channels may be input.

Therefore, in the following description, each input surround signal is represented by SSi [i = 1, 2, 3,...
i], and the ideal reproduction position of each surround signal SSi is θ
It may be i.

The combining section 11 combines the surround left channel signal SLin and right channel signal SRin to generate one combined surround signal SCM. Synthesizing unit 11
Is realized, for example, by an adder that adds two signals at the same ratio.

The power average calculators 12 and 13 output the surround left channel signal SLin or the right channel signal SRi.
An average value Pi of the power magnitudes of n is calculated. In each of the power average calculation units 12 and 13, for example, a calculation is performed by the following equation (1).

[0034]

(Equation 1)

Where N is the average sample time length and si is i
It is the amplitude of the surround signal SSi of the channel.
The power average calculators 12 and 13 calculate the average values P1 and P2 of each surround signal.

The sound image position determining unit 14 determines whether the surround signal S
With respect to the ideal reproduction position of Si, each surround signal SSi
Of the sound image center s
Find θ. That is, the sound image position at the time of reproducing the combined surround signal SCM is determined using the average value Pi of each surround signal SSi.

In the sound image position determining section 14, for example, the following equation (2) is used to calculate the sound image center position sθ.

[0038]

(Equation 2)

Where I is the number of channels of the surround signal SSi. The coefficient buffer 15, as shown in FIG.
The filter coefficients hl and hr used in the calculations in the FIR filters 16 and 17 are determined and stored in advance corresponding to each sound image center position sθ. Sound image position determination unit 1
4, the filter coefficients hl and hr corresponding to the sound image center position sθ from the FIR filter 1 are read out.
6,17.

The filter coefficients hl and h of the coefficient buffer 15
In determining r, various known methods are used. An example will be described below. As shown in FIG. 4, two speakers SPL, S arranged in front of the listening position PL.
The spatial transfer characteristics of sound from the direction of PR and the virtual sound image center position sθ to be obtained to the listening position PL (the positions of both ears) are measured.

Each of the measured space transfer characteristics is Hl
1, Hlr, Hrr, Hrl, Hl, and Hr, the filter coefficient h for the sound image center position sθ
l and hr are obtained by the following equations (3) and (4).

Hl = (Hl × Hrr-Hr × Hrl) / (Hll × Hrr-Hr × Hrl) (3) hr = (Hr × Hll-Hl × Hlr) / (Hrr × Hll-Hrl × Hrr) (4) Next, the FIR filters 16 and 17 perform arithmetic processing on the combined surround signal SCM using the filter coefficients hl and hr read from the coefficient buffer 15, and reproduce the signals from the speakers SPL and SPR. Then, surround signals SCL and SCR whose sound image positions are controlled so that the listener can hear from the direction of the sound image center position sθ are generated.

The combining sections 18 and 19 add the surround signal SCL or SCR to the front left channel signal FLin or right channel signal FRin to generate a combined left channel signal FLC and right channel signal FRC.

The speakers SPL, SPR and SPC are shown in FIG.
Is arranged in front of the listening position PL as shown in FIG. These speakers SPL, SPR, and SPC reproduce the left channel signal FLC, the right channel signal FRC, and the center channel signal FCin. Thus, the surround left channel signal SLin and right channel signal SRin are reproduced in a pseudo manner by the front speakers SPL and SPR.

According to the above-described surround reproduction system 1, the position of the sound image of the surround sound reproduced from the speakers SPL and SPR changes according to the respective powers of the left channel signal SLin and the right channel signal SRin of the surround sound. A feeling of movement can be obtained. Moreover,
Only two FIR filters 16, 1 for sound image control
7, the processing amount is not increased as compared with the conventional surround reproduction system 80a. Therefore, the processing can be performed by a DSP that is not so fast, and an increase in cost can be suppressed accordingly.

Next, an example of calculation in the power average calculation units 12 and 13 and the sound image position determination unit 14 will be described. Assuming that the input surround signals are xs1 [t] and xsr [t] in the power average calculation units 12 and 13, and the respective average values Psl and Psr at 256 sample times are obtained, the above-described equation (1) Equations (5) and (6) are obtained.

[0047]

(Equation 3)

The ideal reproduction position is 30 ° and 150 °.
If the angle is °, the above-described equation (2) for calculating the sound image center position sθ in the sound image position determining unit 14 is as shown in the following equation (7).

Sθ = (Psr × 30 + Psl × 150) / (Psr + Psl) (7) The average value of the power is calculated at regular intervals, and the sound image center position sθ is calculated each time. Each time the sound image center position sθ is calculated, the filter coefficients hl,
hr is read out, whereby the FIR filter 16,
Rewritten as 17 filter coefficients.

According to the surround reproduction system 1 described above, the following effects can be obtained. Since the control direction of the sound image of the surround sound is not directly behind, the sound image of the surround sound is clarified. Since the sound image direction of the surround sound changes in a certain cycle,
A feeling of movement of the sound image is obtained. Although the surround signal is converted into one channel, the sense of reality is improved because the sound image is moving.

In the above embodiment, the synthesizing unit 11 is used as the synthesizing means of the present invention, the power average calculating units 12 and 13 are used as the average calculating means of the present invention, the sound image position determining unit 14 is used as the position determining means of the present invention, The coefficient buffer 15 corresponds to a coefficient variable unit of the present invention.

In the above embodiment, the FIR filter is used, but an IIR filter may be used. The number of inputs to the combining unit 11, the number of power average calculating units 12, 13 and the number of FIR filters 16, 17 may be increased according to the number of channels of the surround signal. Speaker SP
Headphones may be used instead of L, SPR, and SPC. In addition, the configuration of each unit or the whole, the processing content, the order, and the like in the surround playback system 1 can be appropriately changed according to the gist of the present invention.

[0053]

According to the first to fifth aspects of the present invention,
A sense of movement of a surround sound image can be obtained without increasing the processing amount for sound image control.

Therefore, it is possible to provide a realistic and powerful surround playback system at a low price.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a surround playback system according to the present invention.

FIG. 2 is a diagram illustrating a surround signal.

FIG. 3 is a diagram illustrating an example of a coefficient buffer.

FIG. 4 is a diagram for explaining a method of determining a filter coefficient of an FIR filter.

FIG. 5 is a block diagram of a conventional surround playback system.

FIG. 6 is a block diagram of another example of a conventional surround playback system.

[Explanation of symbols]

Reference Signs List 1 surround reproduction system (surround reproduction device) 11 synthesizing section (synthesizing means) 12, 13 power average calculating section (average calculating means, position calculating means) 14 sound image position determining section (position determining means, position calculating means) 15 coefficient buffer ( Coefficient varying means) 16, 17 FIR filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H04S 7/00 H04S 7/00 F

Claims (5)

[Claims] 1. A surround reproduction method for pseudo-reproduction of a plurality of surround signals by a plurality of front speakers, wherein a ratio of magnitudes of powers or amplitudes of the plurality of surround signals is obtained. A surround reproduction method, comprising: controlling an entire sound image position of the surround signal according to a ratio. 2. A surround reproduction method for pseudo-reproduction of a plurality of surround signals by a plurality of front speakers, wherein a sound image center corresponding to an ideal reproduction position of each of the surround signals and a magnitude of power or amplitude. Determining a position, generating a single combined surround signal by combining the plurality of surround signals, and controlling a sound image position of the combined surround signal so that the combined surround signal is reproduced at the sound image center position. Surround playback method characterized by the following. 3. A surround reproducing apparatus for reproducing a plurality of surround signals in a pseudo manner by a plurality of front speakers, wherein a sound image center corresponding to an ideal reproduction position of each of the surround signals and a magnitude of power or amplitude. Means for determining a position; means for combining the plurality of surround signals to generate one combined surround signal; and setting the sound image position of the combined surround signal so that the combined surround signal is reproduced at the sound image center position. Means for controlling, and a surround reproducing apparatus comprising: 4. A surround reproducing apparatus for pseudo-reproducing a plurality of surround signals by a plurality of front speakers, wherein a sound image center corresponding to an ideal reproduction position of each of the surround signals and a magnitude of power or amplitude. Position calculating means for obtaining a position; synthesizing means for synthesizing the plurality of surround signals to generate one synthesized surround signal; and synthesizing the surround signals so that the synthesized surround signals are reproduced from a plurality of front speakers. A surround reproducing apparatus comprising: a plurality of FIR filters for inputting as input signals; and coefficient varying means for varying a filter coefficient of the FIR filter according to the center position of the sound image. 5. The position calculating means includes: an average calculating means for calculating an average value of power or amplitude of each of the surround signals; and an ideal reproduction position of each of the surround signals. The surround reproducing apparatus according to claim 4, further comprising: a position determining unit that calculates a weighted average based on the average value to obtain the sound image center position.