JPH01190162A - Voice conference device for multi-channel - Google Patents

Abstract

PURPOSE:To stable an indoor echo cancellation effect during communication by applying voice reproduction only in a channel where power of a received voice signal is maximum and applying adaptive correction for the echo canceller only in response to the reception voice signal of the channel. CONSTITUTION:A control circuit 10 measures the power of a received voice signal of left/right channels to discriminate which channel of measured value is larger. When the measured value of the left channel is larger, adaptive correction is executed to echo cancellers 4A, 4C and the adaptive correction of the echo cancellers 4B, 4D is stopped, a switch SW-L is turned on and a switch SW-R is turned off. As a result, only the received voice signal of the left channel is reproduced and only the echo canceller in response to the received voice signal of the left channel applies the adaptive correction. Thus, the indoor echo cancelling effect is made stable during communication.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-channel audio conferencing device, and particularly to a multi-channel audio conferencing device that connects a multi-channel transmission path between conference rooms equipped with microphones for transmitting and speakers for receiving. The present invention relates to a multi-channel audio conference device for making calls over a network.

[Conventional technology]

Conventional audio conferencing equipment is a heptanaural type that sends and receives audio signals during a call via a single channel transmission path, and usually the audio generated by the audio played from the speakers in the conference room is routed to the microphone. Equipped with an echo canceller to eliminate echo. This echo canceller receives a received audio signal coming from the conference room of the other party, generates a pseudo-echo signal that approximates the room echo, and subtracts the pseudo-echo signal from the transmitted audio signal emitted by the microphone, thereby eliminating the room echo. to erase.

In order to make a pseudo echo signal approximate to a room echo, just before the meeting starts, increase the correction gain of the echo canceller and apply a training signal such as white noise instead of the received audio signal to adapt the pseudo echo generation characteristics within a short time. Correct and train. During a meeting after training, the correction gain of the echo canceller is made smaller than during training to continue adaptive correction.

[Problem that the invention seeks to solve]

To convert a conventional heptanaural (single-channel) audio conferencing device that has the function of canceling room echoes as described above to multiple channels to obtain a stereo effect, for example, simply line up the desired number of channels. It is not enough to simply install an echo canceller that cancels room echoes that occur between channels. In this way, a multi-channel audio conferencing device with an added echo canceling function between channels can eliminate echoes by allowing each echo canceller to continue its adaptive correction operation during a post-training conference, as in the case of conventional hepinaural devices. This has the problem that the erase operation tends to become unstable.

In other words, in a multi-channel device as described above, echo cancellers for individually canceling room echoes generated in response to the audio signals of each receiving channel are connected in cascade for each transmitting channel for the total number of receiving channels. It is necessary to do so.

Each cascaded echo canceller is trained to cancel only room echoes generated in response to the audio signal of one received channel.

However, if the adaptive modification of each echo canceller continues during the post-training conference, each echo canceller will only cancel the room echo from one receiving channel if there is no correlation between the received audio signals of each channel. However, as the cross-correlation increases, the adaptive correction of each echo canceller progresses toward a state where the first-stage any canceller in the cascade, which is closest to the microphone, cancels most of the room echoes of all receiving channels. do. As a result, the pseudo-echo generation characteristics of each echo canceller change according to changes in the cross-correlation of the received audio signals of each channel.
The characteristics change by deviating from and returning to the characteristics obtained during training, and during the transitional period of change, the echo cancellation residual increases, making the echo cancellation operation unstable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-channel audio conference device that solves the above-mentioned problems and stabilizes indoor echo cancellation during a conference call.

[Means for solving problems]

The device of the present invention includes at least one channel of transmitting circuits for respectively guiding audio signals emitted by microphones to a transmission path, and a plurality of channel receiving circuits for guiding audio signals received from each transmission path to a speaker. Connected between the receiving circuit and the transmitting circuit, one for each indoor echo path from the speaker of a channel to the microphone of one channel, and can adaptively modify generation characteristics of a pseudo echo signal for canceling indoor echo. and a plurality of echo cancellers capable of switching between executing and stopping the adaptive correction, and detecting one channel in which the power of the received audio signal is maximum during a conference call, and performing the reception using only the receiving circuit of the detected channel. and control means for controlling only the echo canceller that guides the audio signal to the speaker and is connected to the receiving circuit to perform the adaptive correction.

〔Example〕

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

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

Although this embodiment uses two channels for both transmission and reception, the same configuration can be applied to a case where there are more channels. The microphones IL and IR and the speakers 9L and 9R are installed in the same conference room. The microphones IL and IR are connected to a transmitting/receiving section 5 via a transmitting circuit having an amplifier 2 and an analog-to-digital converter (ADC) 3, respectively. In addition, the speakers 9L and 9R each have a digital-to-analog converter (DAC).
) 7 and an amplifier 8 . In the middle of the left channel transmitter circuit, that is, the transmitter circuit connected to the microphone IL,
Echo cancellers 4A and 4B are connected in cascade, and echo cancellers 4C and 4D are cascaded in the middle of the right channel transmission circuit, that is, the transmission circuit connected to the microphone IR. Echo canceller 4A~4D
have the same configuration. For example, the echo canceller 4A is connected to the left channel receiving circuit, that is, the speaker 9L.
Receives the audio signal arriving at the receiving circuit connected to the
A pseudo echo signal is generated by the adaptive filter 42 and sent to one input terminal of the subtracter 41. The other input terminal of the subtracter 41 is given a signal obtained by amplifying the audio signal emitted from the microphone IL by the amplifier 2 and converting it into a 7-nano-to-digital signal by the ADC 3. The subtracter 41 sends out a difference signal between the two human power signals. The adaptive filter 42 executes or stops adaptively modifying the pseudo-echo generation characteristics in response to a control signal sent from the control circuit 10. When performing adaptive modification, the adaptive filter 42 modifies the pseudo-echo generation characteristics in response to the difference signal sent out by the subtracter 41 and the audio signal given from the receiving circuit so that the difference signal converges to zero. To go.

The control circuit 10 has a power detection circuit that measures the power of the received audio signal of each left and right channel and determines which channel has a larger power measurement value. ) is larger, the control signal causes the echo cancellers 4A and 4C (or 4B and 4D) to perform adaptive correction and causes the echo cancellers 4B and 4D (or 4A and 4C) to stop the adaptive correction. At the same time, the switch 5W-L (or 5W-R) is turned on, and the switch 5W-
Control R (or 5W-L) to turn it off.

As a result, only the left channel (or right channel) received audio signal is reproduced, and only the echo canceller responsive to the left channel (or right channel) received audio signal performs an adaptive correction operation. Therefore, it is possible to prevent the echo canceling operation from becoming unstable, which would occur if the received audio signals of both channels were to be regenerated and all the echo cancellers continued to make adaptive corrections.

In addition, when the receiving circuit has three or more channels, the sound is reproduced only on the channel with the maximum power of the received audio signal, and only the echo canceller that responds to the received audio signal of that channel performs the adaptive correction operation. Just control it.

〔Effect of the invention〕

As described above, the present invention has the effect of realizing a multi-channel audio conference device that stabilizes the indoor echo cancellation operation during a conference call.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention. IL, IR...Microphone, 2,8...
...Amplifier, 3...Analog-digital converter (ADC), 4A to 4D...Echo canceller, 5...Transmission/reception section, 6...Transmission road,
7...Digital-to-analog converter (DAC)
, 9L, 9R...Speaker, 10...
Control circuit, 5W-L, 5W-R...switch,
41...Subtractor, 42...Adaptive filter. Agent Patent Attorney Oto Uchihara

Claims (1)

[Claims] at least one channel of transmitting circuit for guiding the audio signal emitted by each microphone to a transmission path, a plurality of channel receiving circuits for respectively guiding the audio signal received from the transmission path to a speaker, and one channel for guiding the audio signal received from the transmission path to a speaker.
1 for each room echo path to said microphone in a channel
a plurality of echo cancellers each connected between the receiving circuit and the transmitting circuit, each capable of adaptively modifying the generation characteristics of a pseudo echo signal for canceling indoor echoes, and capable of switching execution and stopping of the adaptive modification; Then, during a conference call, one channel in which the power of the received audio signal is maximum is detected, and the received audio signal is guided to the speaker by only the receiving circuit of the detected channel, and the echo is connected to the receiving circuit. A multi-channel audio conference device, comprising: control means for controlling only a canceller to execute the adaptive correction.