JPH04150652A - Conference talking equipment - Google Patents

Abstract

PURPOSE:To execute the conference talk of a stereo system in a few transmission lines by generating the stereo signal of (n) channels at every ground receiving the stereo signal from sound information distributed to every ground of a receiver side and its sound image static control information. CONSTITUTION:The terminals of the stereo system are connected to a sound image static converter 7 through two-channel transmission lines 3, and the terminals of a sound image static control information communication system are connected to the sound image static converter 7 through transmission lines 6 respectively. Here, a logic number is applied to all callers preliminarily, a sound image static is detected from the stereo signal of the (n) channels received from each ground, the detected sound image position toward a transmitter is encoded by the logic signal, a logic process is operated in the case of plural simultaneous callers, and the stereo signal of the (n) channels is generated again from the logic signal. Thus, it is possible to execute the conference talking of the stereo system in a few transmission lines.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is used for communication between multiple points. In particular, the present invention relates to a conference call device that interconnects a plurality of call terminals.

The present invention provides a conference call device that connects a plurality of destinations by generating sound image localization control information from a stereo signal and generating a sound image on the listening side based on the sound image localization control information. This allows conference calls.

[Conventional technology]

Generally speaking, sound image localization methods for conference call devices are broadly divided into stereo methods, in which the sound image of the transmitting system is reproduced as is on the receiving system using n-channel signals, and sound image localization control, in which control information for sound image localization is transmitted and received. There is an information communication system. FIG. 4 shows a block diagram of a conventional conference call apparatus using a stereo system, and FIG. 5 shows a block diagram of a conventional conference call apparatus using a sound image localization control information communication system.

In the example shown in FIG. 4, two-way communication is performed using a stereo system with T1=2 channels. Each call terminal has 2
Microphones 1 and two speakers 9 are respectively arranged. These microphones 1 and speakers 9 are connected by independent two-channel transmission paths 3 for each combination of a transmitting system and a receiving system. With this configuration, the sound image in the transmitting system can be reproduced as is in the receiving system.

In the example shown in FIG. 5, a single channel transmission line 6 is used, and a plurality of transmitters and receivers face each other to conduct a communication conference. Each call terminal has a number of microphones 4 corresponding to the number of callers and a number of speakers 1 corresponding to the number of opposite parties.
1 is provided, and furthermore, a sound image localization control information transmitter 5 and a sound image localization control information receiver 10 are provided.

The sound image localization control information transmitter 5 detects the sound source position of the transmitting system, generates a number corresponding to the sound source (speaker) position as sound image localization control information, and generates a number corresponding to the sound source (speaker) position as sound image localization control information. Send on a slot channel or in a packet with an address indication. Sound image localization control information receiver 10
generates the sound at a position desired by the listener based on the received sound image localization control information.

For details on the sound image localization control information communication method, see, for example,
Shimada, Suzuki et al., “Ground identification sound image generation method for multi-site audio conference communication system”, Journal of the Institute of Electronics, Information and Communication Engineers, No. J70-
B, No. 9, 1987.

[Problem to be solved by the invention]

However, Shimada, [Development of signal processing technology in communication networks, IEICE Technical Report, Vol. 90, No. 180, Paper number DSP90]
-57.As pointed out on August 23, 1990, the stereo system is a sound image reproduction technology on the transmitting side, and in communication, it can be used for two-way communication and broadcast type communication, but the stereo system is often used. When used in a point-to-point conference call device, there is a drawback that the sound image cannot be localized at a position preferred by the listener, and furthermore, it is difficult to achieve this. This will be explained below.

FIG. 6 shows a configuration when a stereo system is used in multipoint outward communication.

Each terminal of a plurality of speakers is provided with two microphones 1 and a two-channel stereo transmitter 2, respectively. The two-channel stereo transmissions 8!2 of each terminal are connected via separate two-channel transmission paths 3 to separate speakers 9 of the common listener terminal.

This is the configuration of 2r5. For m ground connection, mx2 (
(If n=2) A channel transmission path is required.

Furthermore, in order to use it as a conference call device between both parties, 2
(m-1>xm channel transmission paths are also required.

Furthermore, in the loudspeaker system for two-way communication, four types of echo paths are formed from the speaker 9 to the microphone 1, as shown in FIG. Four echo control devices are required to eliminate the echo caused by this echo path. m ground, the required number of echo control devices is 4Xm. Moreover, the echo cancellation time in this case is not only the spatial propagation time from the speaker to the microphone.
There are problems with the stability (howling and echo) of the entire communication network considering the Messianic network.Therefore, it is expected that the cost of transmission paths and equipment will be enormous.

As described above, attempting to implement a stereo system that includes echo cancellation in multipoint communications poses considerable economical and technical difficulties.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a conference call device capable of connecting multiple points using a stereo system.

[Means to solve the problem]

The conference call device of the present invention includes a means for detecting a sound source position on a speaker side from n-channel stereo signals (n is an integer of 2 or more) arriving from a plurality of m destinations, and an output of this detecting means. means for generating sound image localization control information representing the position of the sound source; means for distributing the audio information from each location to each receiving side; and generating a stereo signal from the distributed audio information and the sound image localization control information. The present invention is characterized by comprising means for generating n-channel stereo signals for each receiving ground.

As the sound image localization control information, a logical number assigned to each speaker can be used.

The means for detecting the position of the sound source consists of
The sound image position on the speaker side can be detected using a level difference between channels, a level difference and a time difference, a cross-correlation function, or an orthogonal transformation method.

It is preferable that the means for generating the sound image control information generates the sound image control information with a different logical number for each position after the means for detecting the sound source position detects the sound source positions of all speakers.

The means for generating the stereo signal may include means for controlling the signal level difference between the n channels, or the level difference and time difference, depending on the content of the sound image localization control information.

The means for detecting, the means for generating sound image localization control information, the means for distributing, and the means for generating stereo signals may be provided in the center device, and some of them, that is, the means for detecting, the means for generating sound image localization control information and means for generating a stereo signal, or even a part of these means may be provided in the terminal.

The conference call device of the present invention can also be connected to a destination using a sound image localization control information communication system. That is, the apparatus may further include means for receiving the audio information arriving from the ground together with its sound image localization control information, and means for transmitting the sound information distributed by the distributing means and the sound image localization control information to the corresponding ground. can.

[For production]

In a conference call device, the sound source emitted from the seat position of each speaker is a point sound source, which is different from a surface sound source such as a musical sound such as an orchestra, in which a plurality of sound sources emit sound within a wide area at the beginning of an opening.

Therefore, by assigning a different logical number to each speaker in advance, and detecting the speaker's position from the n-channel stereo signal from each station, we can determine who the current speaker is for all stations. After the detection, an n-channel stereo signal is generated again for each destination from the logical number corresponding to the speaker and transmitted to the transmission path of each listener.

Furthermore, if the listening side is a terminal using the sound image localization control information communication method, the logical number is used as the sound image localization control information and is transmitted together with the audio information.

In this way, it is possible to make a conference call using stereo audio, and also to enable mutual conversion between the stereo system and the sound image localization control information communication system.

〔Example〕

FIG. 1 is a block diagram of a conference call device according to an embodiment of the present invention. Here, an example will be shown in which the present invention is implemented in a stereo system with n=2, that is, two channels. Also, to avoid complexity, an example of one-way communication will be shown.

A transmitting terminal that employs a stereo method or a sound image localization control information communication method is installed on the opposite side of the caller's side. The stereo transmission terminal includes two microphones 1,
A two-channel stereo transmitter 2 is provided. A transmitting terminal for the sound image localization control information communication system is provided with microphones 4 of a number corresponding to the number of speakers and a sound image localization control information transmitter 5.

A receiving terminal that employs a stereo system or a sound image localization control information communication system is installed on the ground that is the listener's side. A stereo receiving terminal is provided with a two-channel stereo receiver 8 and two speakers 9. A receiving terminal for the sound image localization control information communication system is provided with a sound image localization control information receiver 10 and a number of speakers 11 corresponding to the number of speakers.

The stereo type terminals are each connected to the sound image localization converter 7 via the two-channel transmission line 3, and the sound image localization control information communication type terminals are each connected to the sound image localization converter 7 via the transmission line 6. .

In a stereo transmission terminal, an audio signal input to a microphone 1 is sent to a two-channel transmission line 3 via a two-channel stereo transmitter 2.

In the transmission terminal of the sound image localization control information communication system, the sound image localization control information transmitter 5 detects the position of the sound source from the microphone 4 and identifies the speaker. Furthermore, the sound image localization control information transmitter 5 gives the sound image localization control information of a logical number assigned in advance to the speaker, and adds or extracts the audio signals output from each of the microphones 4. The audio signal and the sound image localization control information are transmitted through the transmission path 6.
Send to.

The signals transmitted from a plurality of stations in this manner are subjected to sound image localization conversion processing by the sound image localization converter 7, depending on whether the listening side uses the two-channel stereo system or the sound image localization information communication system.

Here, (1) a method of detecting the sound source position from the microphone 4 of the transmitting terminal of the sound image control information communication system, identifying the speaker, and adding the sound image localization control information; (2) input from multiple ground sources; A method of performing sound image localization conversion processing on the following will be explained step by step.

First, the operation of the transmitting terminal of the sound image localization control information communication system will be explained.

To identify the speaker, it is necessary to detect from multiple microphones whether the frustum is the speaker. As this detection method, a technique called a sound source position detection method is known. The most general and simplest method of this method is: (a) Select the microphone with the highest audio input level among the input signals of each microphone, and use the person corresponding to that microphone as the person speaking. b) A method in which the speaker corresponding to the microphone whose signal reaches the earliest among audio signals input to multiple microphones becomes the speaker, (C) A method for determining the difference in travel time between each microphone (distance between the microphones) Take the cross-correlation function of the input signal,
A method of detecting the speaker's position (sound source position) from the travel time difference that takes the maximum value, and (d) a method of performing orthogonal transformation from the amplitude sampling amount of each signal input to two microphones are known. There is. Regarding the method (C), see, for example, Noto, Abe, Kido, "Estimation of sound source position using envelope line of band signal", IEICE Electroacoustic Research Group Material EA.
82-3. Shown in 1982. Regarding the method (d), for example, Suzuki, "Analysis of stereo audio signals by optimal orthogonal transformation", IEICE journal paper (
A), Vol. J71-A, No. 2, 1988.

The methods (a) and et al. are effective when there are multiple microphones. On the other hand, methods (c) and (d) are useful for detecting multiple sound source positions from two microphones. That is, using method (C) or (d),
By calculating two audio input signals from the travel time difference between the two microphones, it is possible to detect a sound source position with considerably high accuracy, and it is also possible to detect a plurality of sound source positions. Such position detection can be easily performed using two-channel stereo signals.

Next, sound image localization conversion processing will be explained.

FIG. 2 is a block diagram showing details of the sound image localization converter 7. As shown in FIG. Here, unlike the case in FIG. 1, a case of bidirectional communication will be explained.

This sound image localization converter 7 is equipped with a sound image position detection circuit 12 as means for detecting the sound source position on the speaker side from n=2 channel stereo signals arriving from a plurality of m points of ground, and corresponds to the output of this circuit. A sound image localization control information generation circuit 13 is provided as a means for generating sound image localization control information representing the position of the sound source, and an adder circuit 15 and an audio addition/distribution circuit are provided as means for distributing audio information from each location to each listening location. 16, and n=2 for each ground receiving a stereo signal from the distributed audio information and its sound image localization control information.
A two-channel stereo generation circuit 14 is provided as means for generating channel stereo signals.

The stereo signals input from the two-channel transmission line 3 are input to the corresponding sound source position detection circuits 12, respectively. The sound image position detection circuit 12 has the above-mentioned (C) or (d).
According to the method described above, sound source position information is detected from two-channel audio signals.

Here, before starting communication, how many communication partners exist,
Suppose you know who it is. That is,
A number is assigned to each caller, for example, the first 2
It is known who's voice will arrive from the channel transmission line 3. Therefore, the sound source position detection circuit 12 corresponding to the first two-channel transmission path 3 sends the logical number to the sound image localization control information creation circuit 13 only when there is a call. Similarly, for the audio signal arriving from the r-th (r is an integer not exceeding the number of stereo transmitting terminals) two-channel transmission path 3, the corresponding r-th sound source position detection circuit 12 assigns a logical number. , is sent to the sound image localization control information creation circuit 13.

Since sound image localization control information has already been added to the signal arriving from the transmission path 6, the signal is sent as is to the sound image localization control information creation circuit 13.

The sound image localization control information creation circuit 13 creates sound image localization control information for generating a sound image at the listening side terminal from the input sound image localization control information. If the logic signal described in the paper by Shimada, Suzuki et al. mentioned above is used as the sound image localization control information, the sound image localization control information creation circuit 13 is realized by a circuit that combines a logic story and an exclusive logic story. .

By giving independent logical numbers to each caller in this way, no problem will occur even if a plurality of callers act as talkers at the same time.

For the stereo signals inputted from the two-channel transmission line 3, the signals of both left and right channels are added by corresponding adder circuits 15, respectively. This added signal is sent to the audio addition/distribution circuit 16. Audio information input from the transmission path 6 is also sent to the audio addition/distribution circuit 16.

The audio addition/distribution circuit 16 adds audio signals for each destination other than that destination, and if the corresponding destination is a stereo system,
It is sent to the corresponding two-channel stereo generation circuit 14.

The two-channel stereo generation circuit 14 controls the level difference between left and right audio information, or the level difference and time difference, according to the sound image localization control information from the sound image localization control information creation circuit 13, and generates a two-channel stereo signal. .

When the corresponding destination is an audio localization control information communication system, the audio addition/distribution circuit 16 sends the corresponding audio signal output to the transmission path 6 as is. At this time, audio control information from the sound image localization control information generation circuit 13 is also sent out.

In this way, audio information arriving from a terminal other than the stereo terminal can be supplied as a stereo signal to the stereo terminal. Further, to a terminal using the sound image localization control information communication system, audio information from another terminal and the corresponding sound image localization control information can be supplied.

Many documents are known regarding methods for controlling level differences. For example, illumination, the sense of spread and distance of the sound image J, N
HK Giken Monthly Report, May 1983 issue, Nikaido, “From the Topic of Stereo Acoustics, J, NHK Giken Monthly Report, 1975 April
There are monthly issues, etc.

That is, when it is desired to localize a sound image in the middle of two speakers, the standard listening volume level is set to "1", and the signal levels of both the left and right channels are set to 1/2, respectively. Also, assuming that the front is 0 degrees, the angle at which sound image localization is generated is θ,
Set the direction of the speaker to θ. , if the ratio of the left and right signal levels is k, then sin θ = (1-k)/(1+k) x sin θ.

It is said that there is a relationship between Therefore, by controlling this left and right level difference from audio information, a two-channel stereo signal can be generated.

Regarding the time difference, there is generally known a method called advance sound localization in which the sound image is localized in the direction that reaches the ear first, even if the left and right sound levels are the same. See, for example, Haas, “The Influence on a Single Echo on the Audibility on Speech,” Journal on the Audio Engineering Society, 1972, Vol. 20. The March issue shows that when a time difference is set between the left and right two channel signals, the sound image will be drawn in the direction in which it reaches the ear first if it is within 39m5ec.

This paper also states that when performing sound image localization control, 0 to 5
It has been shown that if control is performed within m5ec, it is possible to freely localize the sound image.

Next, the logical operation of the sound image localization control information creation circuit 13 will be explained.

FIG. 3 shows the arrangement of sound source positions extracted for each ground.

aSb, cSd, eS f, °” In this example, there are three conference participants dSe and f from number 2, and three conference participants x and ySz from destination number m.

Here, first, let the total number of destination numbers m be the number of bits, 00...01 for destination number 1, OO...10 for destination number 2, etc.
, and 10...00 is assigned to the destination number m.

Furthermore, the maximum number of conference participants for each destination is the number of bits, 001 for conference participant a of destination number 1, 0 for conference participant
10. Assign 100 to conference participant C.

Furthermore, 001 is assigned to conference participant d with destination number 2.

As a result, all conference participants are represented by the number of [destination number 10 conference participant numbers of each destination]. These numbers are mutually independent and form orthogonal coded sequences. Therefore, even when a plurality of participants are speakers, it is possible to easily determine how many people are simultaneously speaking by calculating the logical sum.

In the above embodiment, assuming that all destinations perform two-way communication using the stereo system, the number of n-channel transmission paths required for m-ground connections is 2% m, which means that the stereo system requires fewer transmission paths than the conventional example. conference calls can be realized. Also,
Since the signal is not sent back to the transmitting terminal, there is no need for echo cancellation.

In the above embodiments, an example has been described in which the center device is provided with detecting means, sound image localization control information generating means, distributing means, and stereo signal generating means. The present invention can be similarly implemented even if some of these are provided on the terminal side.

〔Effect of the invention〕

As explained above, logical numbers are assigned to all callers in advance, sound image localization is detected from the n-channel stereo signals received from each destination, and the sound image position for the detected caller is determined using logical signals. If multiple people are talking at the same time, this signal is encoded, then subjected to logical processing, and an n-channel stereo signal is generated again from the logical signal. This has the effect of realizing a stereo conference call with a small amount of transmission path. be.

Also, if you prevent the signal from being sent back to the transmitting terminal,
There is no need for echo cancellation, which has the effect of further simplifying the device configuration.

Furthermore, since the sound image localization control information is generated within the apparatus from the stereo signal, it is possible to connect to the sound image localization control information communication system even though it is a stereo system, and there is an effect of obtaining practical flexibility.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conference call device according to an embodiment of the present invention. FIG. 2 is a block diagram showing details of the sound image localization converter. FIG. 3 is a diagram showing the arrangement of sound source positions extracted for each ground. FIG. 4 is a block diagram of a conventional conference call device using a stereo system. FIG. 5 is a block diagram of a conventional conference call device using a sound image localization control information communication system. FIG. 6 is a diagram showing a configuration when a stereo system is used in unidirectional communication between multiple points. 1.4...Microphone, 2...2 channel stereo transmitter, 3...2 channel transmission line, 5...Sound image localization control information transmitter, 6...Transmission line, 7...Sound image Localization converter, 8...2 channel stereo receiver, 9.11
... Speaker, 10 ... Sound image localization control information receiver,
12...Sound image position detection circuit, 13...Sound image localization control information creation circuit, 14...2 channel stereo generation circuit, 15...Addition circuit, 16...Audio addition and distribution circuit.

Claims (1)

[Claims] 1. In a conference call device that connects a plurality of destinations, means for detecting the position of a sound source on the speaker side from n-channel stereo signals arriving from each of a plurality of destinations; and this detecting means. means for generating sound image localization control information representing the position of the sound source in response to the output of the sound source, means for distributing the audio information from each location to each location on the listening side, and distributing the distributed audio information and its sound image localization control information. and means for generating an n-channel stereo signal for each destination receiving the stereo signal from the conference call device. 2. The conference call device according to claim 1, wherein the sound image localization control information is a logical number assigned to each caller at the destination. 3. means for detecting, means for generating sound image localization control information,
2. The conference call device according to claim 1, wherein the means for distributing and the means for generating the stereo signal are provided in the center device. 4. The conference call device according to claim 1, wherein a portion of the detecting means, the sound image localization control information generating means, and the stereo signal generating means are provided in the terminal.