JPH0118633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a conference audio control circuit having a preset function for adjusting the operating state of the conference audio control circuit in a video conference device, etc. to the acoustic environment of the place where the device is installed. It is related to.

(Prior Art) A video conference requires a loudspeaker function in which sound is collected by a microphone and reproduced by a speaker. In this loudspeaker call, in order to prevent howling, echo, etc. due to acoustic coupling between the speaker and the microphone, a loss is inserted into the transmitting system during the receiving state, and a loss is inserted into the receiving system during the transmitting state. A control circuit is used.

FIG. 1 shows an example of this conference audio control circuit, in which 1 is an audio transmitting terminal, 2 is an audio receiving terminal, 3 is a microphone, 4 is a speaker, 5 is a microphone amplifier, 6 is a speaker amplifier, and 7 is a microphone 3 a transmitting/receiving determination circuit that compares the level of the transmitted audio signal collected by the microphone amplifier 5 and the level of the received audio signal inputted to the audio receiving terminal 2, and determines whether it is in the transmitting state or in the receiving state. It outputs a receiving loss insertion instruction signal when it is in the transmitting state, and outputs a sending loss insertion instruction signal when it is in the receiving state. 8 is a transmission/reception loss insertion circuit which inserts a certain loss during the period when the transmission/reception loss insertion instruction signal is output from the transmission/reception determination circuit 7, and makes the loss zero during other periods; 9 is a transmission/reception determination circuit; This is a receiving loss insertion circuit that inserts a constant loss during the period when the receiving loss insertion instruction signal is outputted from 7, and makes the loss zero during other periods.

This circuit has the above-mentioned configuration, and when in either the transmitting state or the receiving state, one system is activated (the receiving system when in the transmitting state, the transmitting system when in the receiving state).
It is controlled to insert a certain loss into the The value of this constant loss is determined so that no howling or echo occurs under certain conditions.

On the other hand, the transmitting/receiving determination method of the transmitting/receiving determining circuit 7 compares the transmitting level and the receiving level, and determines whether there is an input of a transmitting audio signal higher than a certain transmitting level and the level of the transmitting audio signal is higher than that of the receiving audio signal. There is a method of determining that the transmitting state is reached when the value is higher than the level. In the design of this conference audio control circuit, the amount of sound reproduced by the speaker 4 that is picked up by the microphone 3 (amount of acoustic coupling)
is below a certain value. For this reason, a loudspeaker telephone or the like is constructed such that the microphone 3 and speaker 4 are housed in one casing so that the amount of acoustic coupling does not change significantly. However, in video-based services such as video conferencing, the most natural method is to reproduce the received audio signal at a monitor position where the image of the other party is visible. On the other hand, the position of the microphone is the position for participating in the conference. For this reason, the positional relationship between the microphone 3 and the speaker 4 cannot be fixed depending on the arrangement of the room in which the device is placed, how it is used, etc., so the amount of acoustic coupling described above changes significantly. In addition, in such usage where the microphone and speaker are separated, the amount of acoustic coupling is influenced by the acoustic conditions (especially sound absorption characteristics) of the room. Therefore, if the conditions are bad and the amount of acoustic coupling increases, the conference audio control circuit, which is based on a certain amount of acoustic coupling, will pick up the sound reproduced from the speaker at a higher level at the microphone, causing the sound to be in the receiving state. , is determined to be in the transmitting state. As a result, unnecessary loss is inserted into the receiving system, causing phenomena in which the received audio is interrupted or becomes louder or softer, making it extremely difficult to hear.

(Object of the Invention) It is an object of the present invention to eliminate these drawbacks and to make it possible to set the audio system to suit the acoustic environment in which the device is installed and the method of use.

(Structure and operation of the invention) In order to achieve the above object, the present invention has a built-in oscillator for testing, and uses the sound reproduced from the signal of this oscillator to adjust the reproduction volume of the receiving system or the transmitting system. The drawings will be described in detail below.

FIG. 2 shows an embodiment of the conference audio control circuit according to the present invention, in which 10 and 11 are changeover switches that switch to side b only during a preset period, which will be described later.
2 is a low frequency signal generator; 13 is a preset start button; 14 is a press detection circuit that detects the press of the preset start button and outputs a press detection signal; 15 is a delay circuit that delays the press detection signal for a certain period of time; A preset end detection circuit that detects the end of preset and outputs a preset end signal, 1
Reference numeral 7 is a flip-flop that is set by the push detection signal delayed by the delay circuit 15 and reset by the preset end signal, and outputs a changeover switch control signal that changes the contacts of the changeover switches 10 and 11 to the b side for the period from set to reset. . 18 is an electronic volume, 19 is an electronic volume control circuit, and 20 is a microphone sensitivity adjustment volume.

The electronic volume control circuit 19 is the press detection circuit 14
The electronic volume 1 is set by the press detection signal which is the output of
It is preset to generate a control voltage that minimizes the amount of attenuation of 8, and is preset to generate a control voltage that minimizes the amount of attenuation of 8, and a certain amount of signal is input every time there is input of a reception loss insertion instruction signal outputted from transmission/reception judgment circuit 7 inputted via changeover switch 11. In this step, a control voltage is generated to increase the amount of attenuation of the electronic volume 18, and this state is maintained when no reception loss insertion instruction signal is input. Such a circuit can be easily realized by using a presettable down-counter and a D/A converter.

The preset end detection circuit 16 outputs the preset end signal after a certain period of time after the reception loss insertion instruction signal stops or after the push detection signal delayed by the delay circuit 15 is input. The circuit prevents the output of the preset end detection signal when the reception loss insertion instruction signal is output, and outputs the preset end detection signal after a certain period of time after the reception loss insertion instruction signal stops again,
This can be easily realized using a retriggerable multivibrator and an edge detection circuit.

This circuit performs the following operations when executing preset. That is, when executing a preset, the preset start button 13 is first pressed.
When the press detection circuit 14 detects that the preset start button has been pressed, it presets the electronic volume control circuit 19 using a press detection signal outputted, and controls the electronic volume 18 so that the amount of attenuation is minimized. The above-mentioned press detection signal is sent to the delay circuit 15.
After being delayed for a certain period of time, the contacts of the changeover switches 10 and 11 are both switched to the b side by the output of the flip-flop, so that the low frequency signal output from the low frequency signal generator 12 is transferred to the receive loss insertion circuit 9 and the electronic The signal passes through the volume 18 and speaker amplifier 6 and is reproduced by the speaker 4. At this time, the volume reproduced from the speaker 4 will be the maximum volume, but if the amount of acoustic coupling between the speaker 4 and the microphone 3 is sufficiently small, the level of the sound output from the speaker 4 going around to the microphone 3 will be small. Transmission/reception determination circuit 7
remains in listening state. Therefore, the reception loss insertion instruction signal is not output, so the preset end detection circuit 16 outputs the preset end signal after a certain period of time has elapsed after the input of the delayed press detection signal, and the flip-flop 17 is thereby reset. Therefore, the contacts of the changeover switches 10 and 11 are a
Return to the side and exit the preset. In this case,
Since no reception loss insertion instruction signal is output, the output state of the electronic volume control circuit 19 does not change.
Therefore, the electronic volume 18 is set to the minimum amount of attenuation, and the received audio is set to be reproduced from the speaker at the maximum volume.

Next, the acoustic environment is poor, with speaker 4 and microphone 3
As the amount of acoustic coupling increases, the volume input to the microphone 3 increases, causing the transmitting/receiving determination circuit 7 to misidentify the transmitting state. When this misidentification occurs, a reception loss insertion signal is output, so the control voltage output from the electronic volume control circuit 19 is changed to the electronic volume 18.
At the same time, the preset end detection circuit 16 postpones the output of the preset end signal. In this state, the reception loss insertion circuit 9 inserts a loss into the reception system, so the playback volume from the speaker 4 decreases, the input volume to the microphone 3 decreases, and the transmission/reception detection circuit 7 returns to the reception state determination state. The playback volume from the speaker 4 becomes louder. However, since the amount of attenuation of the electronic volume 18 has increased by a certain amount, the playback volume has decreased by that amount. If the input volume to the microphone 3 at this time is low enough to prevent the transmitting/receiving judgment circuit 7 from mistakenly recognizing it as a transmitting state, the preset end detection circuit activates the preset end detection circuit after a certain period of time after the receiving state is established in order to maintain the receiving state. 16 outputs a preset end signal, the flip-flop 17 is reset, and the contacts of the switching switches 10 and 11 return to the side a, thus completing the preset. However, even in this state, if the input volume to the microphone 3 is still excessive and the transmitting/receiving determination circuit 7 mistakenly recognizes that the transmitting state is in the transmitting/receiving state, the above-mentioned operation is repeated, and the transmitting/receiving determining circuit 7 correctly maintains the receiving state. The amount of attenuation of the electronic volume 18 is increased until the desired playback volume is reached.

Since this circuit operates as described above, it is possible to set the volume of the incoming audio level to the maximum volume that can be reproduced in the acoustic environment of the room where the device is installed, and the audio system settings at the time of device installation. has the advantage of being very easy to perform.

In the above explanation, only the reduction in the volume of the reproduction from the speaker 3 has been explained, but in order to prevent the transmission/reception determination circuit 7 from misrecognizing the call, the sensitivity of the microphone 3 may be equivalently reduced. However, lowering the microphone sensitivity will equivalently increase the transmission detection level.
The device will not enter the transmit mode unless you speak loudly.
As the microphone sensitivity is lowered, unpleasant situations such as truncated speech frequently occur. However, if the playback volume becomes too low, it becomes necessary to lower the microphone sensitivity and increase the playback volume. In this case, it is possible to set the optimum microphone sensitivity and playback volume by slightly reducing the amount of attenuation of the microphone sensitivity adjustment volume 20 shown in FIG. 2 and executing the above-mentioned preset again.

In FIG. 2, the electronic volume 18 is used as a playback volume adjustment volume, and the changeover switch is used as a test switch. It is also possible to have a simple configuration in which the volumes 18 and 20 are manually adjusted by removing the . Furthermore, it is also possible to eliminate the changeover switch 10 and the low frequency signal generator 12 and to adjust the volumes 18 and 20 by inputting a low frequency signal or an actual audio signal from the audio receiving terminal 2.

Note that the delay circuit 15 in FIG. 2 is for not operating the changeover switches 10 and 11 until the presetting of the electronic volume control circuit 19 is completed, and is unnecessary if the presetting time of the electronic volume control circuit is sufficiently short.

FIG. 3 shows another embodiment of the conference audio control circuit according to the present invention, in which 21 is an electronic volume for adjusting the microphone sensitivity, and 22 is a reproduction volume adjustment volume for setting the reproduction volume from the speaker.

The operation of the embodiment shown in FIG. 3 is exactly the same as that shown in FIG. 2, except that the electronic volume 21 is controlled by the control voltage output from the electronic volume control circuit 19, and the playback volume of the speaker is set by the playback volume adjustment volume 22. be. Therefore, in this circuit, the microphone sensitivity is set to the maximum possible within the acoustic environment of the room in which the device is installed.

(Effects) As explained above, according to the present invention, it is possible to extremely easily set the conference audio control system to the optimum state in the acoustic environment of the room where the device is installed.
This greatly simplifies the procedure for adjusting the audio system when the device is installed in a location where the acoustic conditions cannot be predicted in advance, such as in a video conferencing device where the position of the microphone and speaker changes depending on the room conditions, method of use, etc. There are advantages.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conference audio control circuit, FIG. 2 is a diagram showing an embodiment of the conference audio control circuit according to the present invention, and FIG. 3 is a diagram showing another embodiment of the present invention. 1...Audio transmission terminal, 2...Audio reception terminal, 3
...Microphone, 4...Speaker, 5...Mic amplifier, 6...Speaker amplifier, 7...Sending/receiving call determination circuit, 8...Sending call loss insertion circuit, 9...Receiving call loss insertion circuit, 10, 11... ...Selector switch, 12...
Low frequency signal generator, 13... Preset start button, 14... Press detection circuit, 15... Delay circuit,
16...Preset end detection circuit, 17...Flip-flop, 18, 21...Electronic volume, 1
9...Electronic volume control circuit, 20...Microphone sensitivity adjustment volume, 22...Playback volume adjustment volume.

Claims (1)

[Scope of Claims] 1. means for determining whether the transmitting state or the receiving state is present; means for inserting a receiving loss into the reproduction system of the received audio signal in the transmitting state to lower the reproduction level from the speaker; In the conference audio control circuit, which has a means for inserting a transmission loss into the transmission system of the audio signal picked up by the microphone, and prevents interference due to acoustic coupling between the speaker and the microphone, the preset operation is started. means for inputting a signal, means for switching to a receiving state of an adjustment audio signal during a period from detection of the start of the preset operation to the end of the preset operation, and an electronic volume for adjusting the reproduction level from the speaker in the receiving state, The electronic volume is controlled so that the amount of attenuation becomes the minimum at the start of the preset, and during the preset period, the amount of attenuation of the electronic volume is controlled to be increased by a certain amount each time a transmitting state is entered. 1. A conference audio control circuit having a preset function, comprising means for controlling an electronic volume, and means for detecting the end of a preset period by detecting that a transmitting state does not occur after the start of the preset. 2 means for determining a transmitting state and a receiving state; means for inserting a receiving loss into the reproduction system of the received audio signal in the transmitting state to lower the reproduction level from the speaker; and means for reducing the reproduction level from the speaker in the receiving state; means for inputting the start of a preset operation in a conference audio control circuit that includes means for inserting a transmission loss into a transmission system of a voice signal and prevents interference due to acoustic coupling between a speaker and a microphone; The microphone has means for switching to a receiving state of an audio signal for adjustment during a period from detection of the start of the preset operation to the end of the preset operation, and an electronic volume for adjusting microphone sensitivity for adjusting the output level from the microphone in the receiving state. The electronic volume for sensitivity adjustment is controlled so that the amount of attenuation becomes the minimum at the start of the preset, and during the preset period, the amount of attenuation of the electronic volume for microphone sensitivity adjustment is reduced by a certain amount every time the microphone is in the transmitting state. The present invention is characterized by comprising means for controlling an electronic volume for adjusting microphone sensitivity to increase the microphone sensitivity, and means for detecting the end of the preset period by detecting that the transmitting state does not occur after the start of the preset. Conference audio control circuit with preset function.