JP2005020639A - Multi-point video conference system using satellite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-point video conference system wherein delay does not occur even if the number of participating stations increases, and more natural and smooth multi-point conference can be realized without echoes, howling, etc. <P>SOLUTION: The synthesized voice from all conference terminals 21, 22, 23 is distributed to all the conference terminals 21, 22, 23 participating in a conference through a multi-point conference control unit 20. In the respective conference terminals 21, 22, 23, the same signal of the voice signal which was transmitted from a self-conference terminal is stored beforehand in a buffer, the signal stored in the buffer is deducted from the synthesized voice of each conference terminal side on the basis of time delay of response wherein voice returns from the multi-point conference control unit 20 through a satellite line 10, and only the voice of the self-conference terminal is removed. As a result, natural and comfortable conference is realized without delay, echoes, howling, etc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multipoint video conference system using satellites, and more particularly to a multipoint video conference system in which a multipoint conference is held around an MCU (Multipoint Control Unit).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a system for performing video / audio video conferencing between a plurality of remote locations using satellites, each participant station has one line and MCU station centered on an MCU (Multipoint Control Unit). Allocating lines for the number of participating stations, connecting the MCU and the TC CONT (TV conference control unit) installed in each participating station via a satellite line, and selecting any of the conference participating stations under the control of the MCU The image information of the other station and the voice data mixed with the other participating stations other than the own station were sent out, and a multipoint conference was held.
[0003]
In the invention described in Document No. 1, a loop LAN communication apparatus to which time division multiplexing is applied is used to sequentially transmit a transmission signal from its own apparatus sent to a transmission line using a predetermined slot of a frame in units of frames. Buffer means for storing, selection means for selecting one of the transmission signals stored in the buffer means in accordance with the number of delay frames, and a component of the transmission signal selected by the selection means from the received signal from the transmission line Subtracting means for subtracting, and adding means for synthesizing the signal subtracted by the subtracting means and its own transmission signal to generate a signal sent to the transmission line.
[0004]
In the invention described in Document No. 1, transmission signals sent from the own apparatus to the transmission path are stored in the buffer means in units of frames, and a frame including the transmission signal from the own apparatus is an integer of one frame via the transmission path. When returning to its own device after double delay, the same transmission signal is extracted from the buffer means by the selection means according to the number of delay frames, and this extracted signal is sent to the subtraction means, and its components are sent to its own device. The signal is removed from the signal of a predetermined slot of the returned frame, and the frame includes only the transmission signal component from the other device. Even if the signal after the removal is converted into an audio signal and external output is performed, no echo or howling occurs.
[0005]
[Patent Document 1] Japanese Patent Laid-Open No. 02-035862 [Problems to be Solved by the Invention]
In the conventional technology using the above-described MCU, when a multipoint conference is to be performed using a satellite line, a transmission signal (audio signal) from the local station is returned to the local station as an echo and howling prevention measure. In order to prevent this, the MCU performs a speech component removal process for each arbitrary station, so that there is a problem in that uplink and downlink 2CH lines and peripheral devices are required for each participating station.
[0006]
The invention described in Document No. 1 connects each communication device in a loop, assigns an arbitrary slot to each station in a time division manner for data communication, and sends a signal (voice component) from the own station in a loop. When a multipoint conference is to be realized by a method of removing only the transmission signal (voice component) of the local station from a predetermined slot when returning to the local station via the transmission path of Although there is no particular problem when the number of communication devices (stations) participating in the system is small, the amount of delay between the stations increases as the number of stations increases, causing a problem in conference operation.
[0007]
In addition, when trying to realize a communication line using a satellite line, the above-described method of assigning an arbitrary slot to each station by the time division method has a problem that the delay amount of the satellite line is further added. It was.
[0008]
The present invention has been made in view of the above problems, and the present invention realizes a more natural and smooth multipoint conference without echo and howling without causing a delay even if the number of participating stations increases. Aims to provide a multi-point video conference system.
[0009]
Another object of the present invention is to provide a multipoint video conference system that realizes a multipoint conference with a minimum number of lines and has a high economic effect.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 is a multipoint in which a multipoint conference control device that controls the overall system such as voice synthesis of all participating stations during a multipoint conference and a plurality of conference terminals are connected in a star shape via a satellite. In the video conference system, the conference terminal includes a buffer unit that stores a transmission signal, a delay control unit that controls the buffer based on a delay time of a response returned from the multipoint conference control device to the own station, and It has a subtracting means for subtracting the transmission signal stored in the buffer from the reception signal from the multipoint conference control device.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a multipoint video conference system using the satellite of the present invention.
FIG. 2 is a block diagram showing a configuration of a conference terminal (voice system) used in the multipoint video conference system of the present embodiment.
[0012]
In FIG. 1, 10-13 are satellite lines. Through this satellite line 10-13, the multipoint conference control device 20 that controls the overall system such as speech synthesis of all participating stations at the time of the multipoint conference is used to control the entire conference room such as a camera and a microphone. Conference terminals 21, 22, and 23 are connected in a star shape.
[0013]
Each conference terminal is assigned one line per station, and the data transmitted from the conference terminals 21, 22, 23 are modulated by the modulators 31, 32, 33, and then demodulated by the demodulator 40, via the satellite channel. 41 and 42 are multiplexed and output to the line interface unit 50.
[0014]
The line interface unit 50 converts the multiplexed signal into a line data format, and controls the multipoint conference via the modulators 31, 32, 33, the satellite lines 11, 12, 13, and the demodulators 40, 41, 42. Sent to the device 20.
[0015]
On the other hand, the audio sent from the multipoint conference control device 20 to each conference terminal 21, 22, 23 via the satellite line 10 is an audio signal obtained by adding all the signals transmitted from each conference terminal 21, 22, 23. is there. As for the video, the video from the conference terminal of an arbitrary station selected by the multipoint conference control device 20 is sent. A multiplexed signal of audio, video, and data sent from the multipoint conference control device 20 is supplied to each conference terminal 21, 22, 23 via the modulator 30, the satellite line 10, and the demodulators 43, 44, 45. Is done. The multiplexed signal supplied to each conference terminal is sent to the MUX / DMUX unit 51 via the line interface unit 50 and separated into video, audio, and data signals, and then the audio code is encoded / decoded. 52.
[0016]
The encoding / compositing unit 52 performs a decoding process and outputs the result to the echo canceller 62. The echo canceller unit 62 includes a subtracter 64, a delay control unit 66, and a buffer 68. The echo canceller 62 has a function of removing only the audio signal transmitted from the own conference terminal from the synthesized audio of all the participating conference terminals added by the multipoint conference control device 20.
[0017]
The audio signal combined by the encoding / decoding unit 52 is subtracted by the subtracting unit 64 from the audio signal previously stored in the buffer unit 68 at the timing of control from the delay control unit 66. It is sent to the D / A converter 54.
[0018]
In the delay control unit 66, a response time in which an audio signal transmitted from the self-conference terminal in advance is returned to the self-conference terminal via the satellite lines 11, 12, 13, the multipoint conference control device 20, and the satellite line 10. , And output control of the audio signal stored in the buffer unit 68 is performed according to the measured value.
[0019]
The voice sent to the D / A converter 54 is a digital signal. The analog audio signal is converted by the D / A converter 54, amplified by the amplifier 56, and sent to the speaker 58. Only synthesized speech from all participating conference terminals other than the self-conference terminal flows from the speaker 58, and a natural and smooth conference without echo and howling is realized.
[0020]
【The invention's effect】
According to the present invention, it is possible to realize a more natural and smooth multipoint conference without echo and howling without causing a delay even when the number of participating stations increases.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a conference terminal according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Satellite 10, 11, 12, 13 Satellite line 20 Multipoint conference control apparatus 21, 22, 23 Conference terminal 30, 31, 32, 33 Modulator 40, 41, 42, 43, 44, 45 Demodulator 50 Line interface part 51 MUX / DMUX section 52 Encoding / combining section 53 A / D converter 54 D / A converter 55, 56 Amplifier 57 Microphone 58 Speaker 61, 62 Echo canceller 63, 64 Attenuator 65, 66 Buffer 67, 68 Delay Control unit

Claims (1)

In a multipoint video conference system in which a multipoint conference control device that controls the overall system such as speech synthesis of all participating stations during a multipoint conference and a plurality of conference terminals are connected in a star shape via a satellite,
The conference terminal includes buffer means for storing a transmission signal, delay control means for controlling the buffer based on a response delay time returned from the multipoint conference control apparatus to the own station, and the multipoint conference control apparatus. A multipoint video conference system using a satellite, comprising subtracting means for subtracting a transmission signal stored in the buffer from a received signal from a satellite.

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