JPH01899A - sound field control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides pseudo four-channel stereo signals from two-channel stereo signals.
This invention relates to a sound field control circuit that creates channel stereo signals.

(Prior Art) Sound field control circuits with various configurations for pseudo-four-channeling a two-channel stereo signal have been proposed. FIG. 4 is a configuration diagram of one example.

As shown in FIG. 4, the signals of the left and right channels of the 2-channel stereo signal input from the input terminals 1L and 1R are connected to the front left and right speakers LF of the 4-channel stereo via a power amplifier (not shown), etc. RF, where it is converted into sound. On the other hand, the signals of the left and right channels mentioned above.

R is subtracted by a subtracter 2, and its output (LR) is delayed by a delay circuit 3. The signal is then applied to rear left and right speakers LR2RR of a 4-channel stereo system via a power amplifier (not shown), where it is converted into sound.

In such a configuration, the rear left and right channel signals are reduced.
f(LR), it is possible to reduce the sense of discomfort that sounds (such as dialogue) that should be localized in the center are diffused to the periphery. Furthermore, since the difference signal obtained by subtraction contains many reverberation components, it is possible to increase the amount of reverberation components extracted in proportion. On the other hand, in the conventional configuration shown in FIG. 4, since the difference signal is delayed by a delay circuit, it is possible to give the listener a sense of distance to the rear. This is because real reverberation is a reflection of direct sound and therefore has a time delay.

(Problems to be Solved by the Invention) However, in the conventional configuration as described above, there is a drawback that the left and right directionality inherent in stereo signals is lost. This is due to the fact that by subtracting (LR) the signals, the rear sound is essentially converted to monaural.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sound field control circuit that can reproduce the sense of direction even for 4-channel stereo rear sounds and that can easily configure the circuit therefor.

(Means for Solving the Problems) The present invention outputs a 2-channel stereo input signal as a 4-channel stereo front left and right channel signal, and extracts a difference signal between the 2-channel stereo input signals and sends it to a delay circuit. It is a sound field control circuit 11 that outputs the input signal and outputs the output as a rear left and right channel signal of a 4-channel stereo, and is equipped with a level detection means and a level control means as described below.That is, the level detection means has a 2-channel Detects the level of the left and right input signals of the stereo input signal, controls it according to the relative level indicated by the relative output signal between them, and outputs this as a 4-channel stereo rear left and right channel signal. do.

(Function) According to the present invention, the level detection means detects the R level of the left and right input signals of the two-channel stereo input signal, and outputs a detection signal according to the relative level of R. For example, for the left channel, L/R proportional signal,
The right channel is output as an R/L proportional signal. Therefore, the level control means controls the output of the delay circuit according to the relative level indicated by the detection signal from the level detection means, and outputs this as rear left and right channel signals of a 4-channel stereo. It becomes possible to reproduce images with a sense of direction rather than monaural.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3 of the accompanying drawings. In addition, in the description of the drawings, the same elements are given the same reference numerals, and redundant description will be omitted.

FIG. 1 is a basic configuration diagram of a sound field control circuit according to an embodiment of the present invention. In the figure, there is a delay circuit 3 and a rear left 6 channel speaker LR.

Between RR, level control means 5L for controlling the level amount of each supply signal to these speakers LR and RR,
5R is provided. This level control means 5
The level amount control by L and 5R is configured to be performed by an L/R proportional signal and an R/L proportional signal from a level detection means (not shown).

FIG. 2 is a detailed configuration diagram of the main parts of the embodiment shown in FIG. 1. In the figure, the level detection circuit 7 has an input terminal 1L,
A 2-channel stereo input signal from 1R and R are respectively input, and an L/R proportional signal and an R/L proportional signal are output, respectively.

A voltage controlled amplifier (VCA) 511.51R receives a 2-channel stereo input signal and a difference signal (L-R
) is roughly delayed by the delay circuit 3, and the L/R and R signals of the level detection circuit 77')) are respectively input.
Controls each of the rear left six output signals of the four-channel stereo according to the /L proportional signal.

FIG. 3 is an explanatory diagram of a signal processing method in the level detection circuit 7. In the figure, two-channel stereo input images No. and R are each converted into absolute values in blocks 71L and 71R, and are provided to, for example, a microprocessor (not shown). Block 72L implemented by this microprocessor.

72R is 1ml/IRI and IRI/IL, respectively.
1. Find and output each ratio. These signals are then given as control voltages to the VCAs 51L and 51R, respectively.

Next, the operation of the sound field control circuit configured as described above will be explained.

For audio that should be localized in the front center of the 2-channel stereo input image and R, such as dialogue, the output of the subtractor 2 becomes L-R=O because the levels of the signal and R are equal. , no rear sounds related to these are generated. Therefore, these lines etc.
Since the sound does not spread to the surrounding area, the listener does not feel uncomfortable.

On the other hand, for different components of the two-channel stereo input image signal R, the output of the subtracter 2 is I-R.
≠O, and a rear sound based on the difference component (generally mainly a reverberation component) is generated from the rear left and right speakers LR and RR of the 4-channel stereo. At this time,
The level detection circuit 7 has a 2-channel stereo input image signal.
Specifically, depending on the relative level of R, L/R
A proportional signal and an R/L proportional signal are output, thereby controlling the output level of each of the VCAs 51L and 51R. Therefore, the 2-channel stereo input image signal, R
When the level of the left channel component is higher than the level of the right channel component R, the sound from the left speaker LR of the rear left and right speakers LR and RR of the 4-channel stereo becomes stronger, and the rear sound is localized to the left. Furthermore, when the right channel component R is higher in level than the left channel component, the rear sound is localized to the right. As a result, it becomes possible to reproduce the left and right directionality of rear sounds as well.

This invention is not limited to the above embodiments,
Various modifications are possible.

For example, the level control signal is not limited to L/R proportional and R/L proportional signals, but can be of various types, such as L2/R-proportional and R2/L2 proportional signals. Further, the level control means is not limited to using a VCA. Roughly speaking, there are 4-channel stereo front left and right speakers F.

A front center speaker may be provided in the middle of the RF.

〔Effect of the invention〕

As explained above, according to the present invention, when delaying the difference signal of the 2-channel stereo input signal and outputting it to the rear left and right speakers of the 4-channel stereo, the relative level of the 2-channel stereo input image signal is Since the output of the rear left and right speakers is controlled according to the height, the directionality of the rear sound can be reproduced, making it possible to realize a realistic 4-channel stereo. Also,
The present invention can be realized by simply adding circuits for level detection and level control, so it has the effect of simplifying the configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a configuration diagram of main parts of the sound field control circuit shown in FIG. 1, and FIG. 3 is a level detection circuit shown in FIG. 2. A diagram explaining
FIG. 4 is a configuration diagram of a conventional example. 1L, 1R...2 channel stereo input terminal, 2.
... Subtractor, 3... Delay circuit, 4... Listener,
LR2RR...4-channel stereo rear speaker, LF, RF...4-channel stereo front speaker, 51L, 51R...VCA. Patent applicant Nippon Musical Instruments Manufacturing Co., Ltd.

Claims (1)

[Scope of Claims] A 2-channel stereo input signal is output as a 4-channel stereo front left and right channel signal, and a difference signal between the 2-channel stereo input signals is extracted and inputted to a delay circuit, and its output is output as a 4-channel stereo front left and right channel signal. In a sound field control circuit that outputs rear left and right channel signals of a 4-channel stereo, the levels of the left and right input signals of the 2-channel stereo input signal are detected, and a detection signal is generated according to the relative level between them. and level control means for controlling the output of the delay circuit according to the relative level indicated by the detection signal and outputting it as rear left and right channel signals of the four-channel stereo. A sound field control circuit comprising: