JPH0494300A - Four-channel surround processor - Google Patents

Abstract

PURPOSE:To obtain a natural presence by sharing output levels of left and right rear channels depending on the ratio of the level of left and right front channel input signals. CONSTITUTION:The above processor is provided with a divider 6, a logarithmic amplifier 7, a voltage controlled attenuator(VCA) circuits 8,9, an inverse amplifier 10, a variable resistor 11 and averaging circuits 12,13 in addition to differential amplifiers 1,4,5, a phase shifter 2 and an inverse amplifier 3. Then the divider 6 calculates an amplitude ratio of an original signal of both channels, the logarithmic amplifier 7 applies logarithmic transformation to the amplitude ratio to output a logarithmic amplitude ratio signal. Then the variable resistor 11 adjusts the amplitude of the logarithmic amplitude ratio to output a reference voltage signal, the VCA circuits 8,9 receive an indirect signal and uses the reference voltage signal to adjust the amplitude of the indirect signal thereby outputting a rear channel signal. Thus, a natural presence is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-channel surround processor, and particularly to a four-channel surround processor suitable for audiovisual (AV) applications.

[Conventional technology]

FIG. 4 shows an example of a conventional 4-channel surround processor.

In FIG. 4, the conventional 4-channel surround processor is comprised of differential amplifiers 1 and 4.5, a phase shifter 2, and an inverting amplifier 3.

Next, the operation of a conventional 4-channel surround processor will be explained.

An audio channel input signal LI and an R channel input signal RI are respectively input, and the differential amplifier 1 generates and outputs a difference signal LR between the two signals.

Next, the difference signal LR is input to the phase shifter 2, a predetermined phase shift is performed, and a phase-shifted difference signal φ(L-R) is output.

Next, the differential amplifier 4 outputs the L channel input signal LI
and the phase shift difference signal φ(LR) are added and output as the front upper channel output signal LF.

On the other hand, the differential amplifier 5 outputs the R channel input signal RI
and the phase shift difference signal φ(LR) whose phase has been inverted by the inverting amplifier 3 are added and output as a front R channel output signal RF.

Further, the phase shift difference signal φ(L-R) is output as is as the rear output signal BO.

[Problem to be solved by the invention]

The conventional 4-channel surround processor mentioned above is
The front, that is, the front, had two channels, but the back, that is, the rear, had one channel.

Recently, there have been some models with two rear channels, but most of these simply invert the phase of the rear output of one channel to generate another rear channel.

In the above-mentioned refinement, for example, if the left and right signals are in phase, such as the anallancer's voice, they will be output from the front channel, and if the left and right signals are random, such as applause or cheers, the difference component will be output. Since the rear channel is output, you can get a certain sense of reality.

However, assuming a biased sound field such as an anallancer being right next to you, the difference signal between the R channel and L channel will be large, and even if you perform processing such as phase shift on this, the output level of the rear channel will be There was a drawback that the left and right sides were the same.

Therefore, in such a case, not only when the rear channel is 1 channel, but also when the rear channel is 2 channels, there will be a considerable output level from the rear channel on the side opposite to the side where the anallancer is located, which is unnatural due to the present invention. The 4-channel surround processor adds the original signals of the left and right channels and an indirect signal obtained by changing the phase of the amplitude difference signal of the original signals to generate front left and right channel signals and the indirect signal as a rear channel signal. a four-channel surround processor, comprising: a division circuit that calculates the amplitude ratio of the original signals of both channels; a logarithmic amplifier circuit that logarithmically transforms the value of the amplitude ratio and outputs a logarithmic amplitude ratio signal; and the logarithmic amplitude ratio. an amplitude adjustment circuit that adjusts the amplitude of a signal and outputs a reference voltage signal; and a voltage control amplitude adjustment circuit that receives the indirect signal, adjusts the indirect signal amplitude using the reference voltage signal, and outputs the rear channel signal. It has the following.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

In FIG. 1, the 4-channel surround processor of the present invention includes differential amplifiers 1, 4, .
5, phase shifter 2, and inverting amplifier 3, as well as a divider 6, a logarithmic amplifier 7, and a voltage controlled attenuation (VCA) circuit 8.9
, an inverting amplifier 10, a variable resistor 11, and 1. It is refined from an average northerly time of 11!12.13.

The averaging circuits 12 and 13 are circuits that output the average effective value of the input signal over a certain period of time for each channel.

A VCA circuit is a variable attenuator that controls the amount of attenuation of a signal path using a reference voltage signal.

Next, the operation of this embodiment will be explained.

First, an audio channel input signal LI and an R channel input signal RI are respectively inputted to the differential amplifier 1.
A difference signal LR between both signals is generated and output.

Next, the difference signal LR is input to the phase shifter 2, a predetermined phase shift is performed, and a phase-shifted difference signal φ(L-R) is output.

Next, the differential amplifier 4 outputs the L channel input signal LI
and the phase shift difference signal φ(LR) are added and output as the front upper channel output signal LF.

On the other hand, the differential amplifier 5 outputs the R channel input signal RI
and the phase shift difference signal φ(LR) whose phase has been inverted by the inverting amplifier 3 are added and output as a front R channel output signal RF.

The process up to this point is similar to the conventional example described above.

Next, the rear LR each channel output signal LB.

Generation of RB will be explained.

First, the input signals of each LR channel, LI, and R are converted into average effective values of the input levels within a preset time by averaging circuits 12 and 13, respectively, and are input to the divider 6. be done.

In the divider 6, the level ratio of L and H is L/R! , and input to the logarithmic amplifier 7.

The logarithmic amplifier 7 logarithmically transforms the input or R level ratio L/R value and outputs a logarithmic level ratio signal LOGL/R.

Next, the logarithmic level ratio signal LOGL/R is connected to the variable resistor 11.
The level is adjusted by , and the reference voltage signal ■ is generated.

The reference voltage signal V is applied to the control terminal of the VCA circuit 8.

On the other hand, the signal terminal of the VCA circuit 8 has a phase shift difference signal φ.
(LR) is input, and its attenuation amount, ie, level, is controlled by the reference voltage V, and is output as a rear L channel signal LB.

Further, the reference voltage signal V has its phase inverted by the inverting amplifier 10 and is applied to the control terminal of the VCA circuit 9.

Similar to the L channel, the phase shift difference signal φ (LR) is input to the signal terminal of the VCA circuit 9, and its attenuation, that is, the level, is controlled by the reference voltage ■, and the rear L channel signal is Output as RB.

FIG. 2 shows an example of the relationship between the above signals when a point sound source moves at a constant speed from right to left.

In FIG. 2, the rear L channel signal LB gradually changes from a low level to a high level, while the level of the rear L channel signal RB changes in the opposite direction from a high level to gradually a low level. The situation will be shown.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

In FIG. 3, a level control circuit 14 digitally controlled by a remote control is used in place of the manual variable resistor 11 in the first embodiment.

As a result, you can control the surround effect with a remote control.

The level control circuit 14 includes a voltage controlled attenuator 15 and a D-A
It is composed of a converter 16, a microcomputer 17, a remote control receiver 18, and a remote control transmitter 19.

The other configurations and functions are the same as those in the first embodiment, and the explanation will be omitted to avoid redundancy.

Next, the operation of this embodiment will be explained.

First, one remote control transmitter transmits a command signal specifying the control voltage of the voltage control attenuation H15 for generating the reference voltage of the VCA circuit 8.9 that determines the surround effect.

The remote control receiver 18 receives and decodes this, and the microcomputer 17 converts it into a digital value corresponding to the specified control voltage.

This digital value is converted into a DC voltage by the DA converter 16, inputted to the voltage control attenuator 15, and similarly to the variable resistor of the first embodiment, the logarithmic level ratio signal LOG L/
A predetermined amount of attenuation is given to H.

Other operations are the same as those in the first embodiment, and the explanation will be omitted to avoid redundancy.

〔Effect of the invention〕

As described above, the present invention has the effect of obtaining a realistic four-channel surround effect by distributing the output levels of the rear left and right channels according to the amplitude ratio of the front left and right channel input signals.

Furthermore, even in an extremely biased sound field, for example, when a sound source is directly to the side, the output of the channel opposite to the rear sound source is greatly attenuated, resulting in the effect that a natural sound field feeling can be obtained.

1.4.5... Differential amplifier, 2... Phase shifter, 3.1
0... Inverting amplifier, 6... Divider, 7... Logarithmic amplifier, 8.9... Voltage controlled attenuation (VCA) circuit, 11
..., variable resistor, 12.13...averaging circuit, 14
... Level control circuit, 15 ... Voltage control attenuator, 1
6... D-A converter, 17... Microcomputer, 18... Remote control receiver, 19... Remote control transmitter.

Claims (1)

[Scope of Claims] The original signals of both left and right channels and an indirect signal obtained by changing the phase of the amplitude difference signal of the original signals are respectively added to form front left and right channel signals, and the indirect signals are added to a rear channel signal. a four-channel surround processor, comprising: a division circuit that calculates the amplitude ratio of the original signals of both channels; a logarithmic amplifier circuit that logarithmically transforms the value of the amplitude ratio and outputs a logarithmic amplitude ratio signal; and the logarithmic amplitude ratio. an amplitude adjustment circuit that adjusts the amplitude of a signal and outputs a reference voltage signal; and a voltage control amplitude adjustment circuit that receives the indirect signal, adjusts the indirect signal amplitude using the reference voltage signal, and outputs the rear channel signal. A 4-channel surround processor characterized by having.