JP2003189274A - Video conference system and signal transmitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a video conference system in which devices are made small and economization is performed by reducing the processing load of a processor. <P>SOLUTION: A plurality of signal transmitting devices connected in a ring shape through a network to perform a video conference have a physical interface 204 for performing physical matching with a transmission line, an SAR part 203 for mutiplexing and multiplexly separating a signal such as an image, a sound and data, and a ring functioning part 210 for constructing a ring type network. The ring type functioning part is provided internally with a conference controlling means 801 that uses data for conference control having commands for controlling the beginning and end of a conference, information indicating the number of signal transmitting devices participating in the conference, information showing a conference number for identifying a conference to realize a plurality of conferences in the network, and information showing the inherent number of a device participating in the conference and the condition of the device. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video conference system and a signal transmission device, and more particularly to the use of signals such as image / sound data and system control data according to MPEG-2 which is a high efficiency coding technique. The present invention relates to a video conference system for conducting a conference between multiple points and a signal transmission device used therefor.

[0002]

2. Description of the Related Art In recent years, a high efficiency coding system called MPEG-2 has been standardized. Transmission of signals using MPEG-2 requires a transmission speed of about 6 Mbit / sec to 10 Mbit / sec in order to perform faithful transmission of data. In a system requiring such a high-speed transmission line, an optical fiber is generally used as the transmission line, and a high-speed transmission system having a transmission speed of 155.52 Mbit / sec is often used.

Since a high-speed transmission line has a large transmission capacity, it is possible to re-multiplex and transmit a plurality of MPEG signals and a multiplexed signal of a plurality of data on one line. As a method of re-multiplexing, for example, connecting a plurality of transmission devices in a ring shape,
There is known a method of superimposing a signal generated by the own device on a signal received from the upstream transmission device of the own device and transmitting the signal to the downstream transmission device. As a conventional technique related to the re-multiplexing method, an ATM (Asynchronous) that decomposes an image, a voice, a data signal, etc. into block units of a certain length, and gives a signal type and address information to the head of each block.
Transfer Mode) Multiplex technology is known. As a conventional technique related to the method of constructing the ring network by the ATM system, for example, Japanese Patent Laid-Open No. 2001-1861.
The technique described in Japanese Patent Publication No. 35-35, etc. is known. This conventional technique realizes a ring function by a general-purpose and simple hardware configuration, which makes it possible to reduce the processing load, downsize the system, and make the system economical.

As a method of conducting a video conference between multiple points using image transmission devices connected in a ring, a method that requires a control device for managing and controlling the video conference, and a transmission device that hosts the conference. However, there is known a method of sending a conference control signal to each transmission device participating in the conference to perform management control. In the former method, the scale of the control device increases depending on the scale of the video conference. In the latter method, the conference control signal is processed by the processor attached to each transmission device, but the processing of the control signal is complicated, and each control terminal requires a transmission device.

FIG. 8 is a block diagram showing the functional arrangement of an ATM signal transmission apparatus that constitutes a video conference system using a ring network according to the prior art utilizing an ATM network. In FIG. 8, 101 is a camera and 10
2 is a microphone, 103 is an encoding processing unit, 104 is an external data generation unit, 105 is an ATM interface unit, 106 is a transmission line, 107 is a decoding processing unit, 108 is a monitor, 10
Reference numeral 9 is a speaker, and 110 is an external data receiving unit.

In FIG. 8, an encoding processing unit 103, a data generating unit 104, a decoding processing unit 107, and an external data receiving unit 110 are connected to an ATM interface unit 105, and the whole of them constitutes an ATM signal transmission device. ATM
The signal transmission device is connected to a plurality of other ATM signal transmission devices having the same configuration in a ring shape via the transmission path 106 to form a video conference system.

In the ATM signal transmission apparatus having the above-mentioned configuration, the signal input from the video input from the camera 101 and the voice input from the microphone 102 is encoded by the encoding processing unit 103 which realizes the high efficiency encoding method. It is processed. The ATM interface unit 105 performs ATM multiplexing processing on various data signals input from the external data generation unit 104 and the signals coded by the coding processing unit 103, and the multiplexed processing is performed at high speed. It is sent to the transmission line 106. Also, the ATM interface unit 1
05 receives the data from the upstream of the network having the ring-shaped transmission path, demultiplexes the data, and inputs the image and audio signals to the decoding processing unit 107. The decoding processing unit 107 decodes the input demultiplexed data to obtain image and audio signals, and these signals are reproduced by the monitor 108 and the speaker 109. Further, the data signal included in the signal demultiplexed by the ATM interface unit 105 is passed to the external data receiving unit 110 to be received and processed.

FIG. 9 is a block diagram showing the functional arrangement of the ATM interface unit 105. In FIG. 9, 201
Is a multiplexer, 202 is a demultiplexer, 203 is a segment and reassemble (Segment And Reassemble,
Block called SAR), 204 physical interface section, 205 optical / electrical conversion section, 206 address detection section, 207 switch section, 208 control circuit, 209 transfer memory, 210 ring function section, 211 control The processor 212 is a data bus.

The ATM interface unit 105 converts the various data input from the encoding processing unit 103 and the data generation unit 104 into ATM cells and multiplexes the ATM data into a multiplexing unit 2.
01 and the multiplexed signals are demultiplexed and input to the decoding processing unit 107 and the data receiving unit 110. The SAR block 203 includes the demultiplexing unit 202, and the multiplexed ATM cells are parallel-serial converted. And 155.52Mb
A physical interface unit 204 for converting it / sec into a serial signal and vice versa, and an optical / electrical converting unit 205 for mutually converting an optical signal and an electric signal are configured. Further, the ATM interface unit 105 selects whether the ATM interface unit 105 should take in the data from the upstream transmission device among the transmission devices connected in a ring shape between the physical interface unit 204 and the SAR block 203 or perform the downstream transmission. An address detection unit 206 that analyzes the address of an ATM cell header for determining whether to transfer the data to the device, a switch unit 207 that alternately multiplexes the data generated by the device itself and the data transferred to the downstream device to the ATM. A control circuit 208 for controlling the switch, and a transfer memory 20.
9 is provided with a ring function unit 210. The ATM interface unit 105 also includes a processor 211 that controls the physical interface unit 204, the SAR block 203, and the ring function unit 210 via the data bus 212.

The ATM constructed as described above
A plurality of signal transmission devices are connected in a ring shape by a high-speed transmission path, and the cameras connected to the respective signal transmission devices,
It is configured as a system for conducting multipoint video conferences using a monitor or the like.

The signal transmission device that hosts the conference is
At the time of holding or ending a conference, data for controlling and managing the conference is transmitted to the signal transmission devices that participate in the conference. The control management data includes a control command for holding and ending a conference, an image of a signal transmission device participating in the conference, an address for receiving a voice signal, and the like. The control information of such a conference is superimposed on the image, audio signal, and other data received by each transmission device. Further, the control information of the conference is extracted from a large amount of various data and processed after being received by each signal transmission device.

[0012]

The above-mentioned conventional video conference system requires an external control terminal for controlling and managing the conference or a high speed processor for processing a complicated control signal. Because
There are problems that it is difficult to downsize the entire system, to make it economical, and to reduce the processor load associated with the device.

Further, the prior art described with reference to FIGS. 8 and 9 has a problem that the processing load of the processor of each signal transmission device for processing control data becomes heavy.
Furthermore, as the scale of the conference increases, the data of the conference control information increases and becomes complicated, so that a high-speed processor is required, and it becomes difficult to reduce the size and economy of the entire system. Therefore, when a multi-point video conference is realized using a ring network, conference control data is generated by an external data generation unit connected to a signal transmission device, and each transmission device participating in the conference receives the data. The conventional technique described with reference to FIGS. 8 and 9 in which control data processing is performed by the processor attached to the signal transmission device requires a high-speed general-purpose processor, which makes it difficult to reduce the size and cost of the entire system.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide information processing for controlling a video conference.
By implementing the ring function block that performs data transfer processing and data reception processing to realize a ring network, it is possible to reduce the processor processing load, reduce the size of the device, and make it economical. It is an object of the present invention to provide a video conference system and a signal transmission device between multipoints using the signal transmission device connected to the.

Another object of the present invention is to determine whether the received data is data to be received by the device itself or data to be transferred to a device connected downstream in order to form a ring network. In the ring function unit for processing, by processing the conference control data including the information for controlling the video conference, it is possible to reduce the processor load due to complicated data processing, and thus the multi-point television. To provide a conference system and a signal transmission device.

[0016]

According to the present invention, the above object is to provide a video conference system for conducting a conference between a plurality of signal transmission devices connected in a ring by a network, wherein the signal transmission device is a conference Commands for controlling holding and ending, information indicating the number of signal transmission devices participating in the conference, information indicating the conference number for identifying the conference to realize multiple conferences in the network, and the unique number of the device participating in the conference And a conference control unit that uses conference control data having information indicating the state of the device and a device that receives the conference control data, controls the holding and ending of the conference, and selects the conference data to be received, And a means for adding the current status of the own device to the own device status information flag in the conference control data. It is made.

Further, the above-mentioned object is that the signal transmission device is
A physical interface that physically matches the transmission path,
AT from signals multiplexed with signals such as image, sound, and data
A segment and assembling unit for disassembling into M cells or assembling an ATM cell into an original multiplexed signal, and a ring function unit for configuring a ring network between the physical interface and the segment and assembling unit. And the conference control means using the conference control data is provided in the ring function unit.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a video conference system according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of a video conference system according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining a conference control data format. In FIG. 1, 301 to 304 are ATM signal transmission devices,
Other reference numerals are the same as those in FIG.

As shown in FIG. 1, a video conference system for conducting a conference between multipoints by a ring type connection system according to an embodiment of the present invention, as shown in FIG.
2, a plurality of ATM signal transmission devices 301 to 304 to which a monitor 108 and a speaker 109 are connected are connected by a transmission line 106 in a ring shape. Each of the ATM signal transmission devices 301 to 304 has the same configuration as that of the conventional technique described with reference to FIG.

In the video conference system configured as described above, any one of the plurality of ATM signal transmission devices can start the conference by transmitting the conference control data to another ATM signal transmission device. it can. The format of the conference control data used for this purpose is shown in FIG. 2, and next, this data format is controlled.

The conference control data format is, as shown in FIG. 2, a flag 401 indicating the holding and ending of the conference, a register 402 indicating the number of devices participating in the conference, and a plurality of conferences being held in the same network. , A register 403 indicating a conference number for identifying the conference, and a plurality of registers 404 having a register indicating a terminal number unique to each ATM signal transmission device participating in the conference and a terminal state of the device.
It is composed of In FIG. 2, the bit width of one line has a predetermined size and the terminal number is 2
The reason for crossing over the lines is to represent the terminal number as a series of these. The conference control data having the above-described data format is preset in the ATM signal transmission device by a method of generating the video conference control software application in the data generation unit included in the ATM signal transmission device. It can be generated by a method of generating from configuration information or the like.

The above-mentioned conference control data generated by the ATM signal transmission device hosting the conference is transmitted after being converted into ATM cells by adding a 5-byte cell header, and then ATM signal transmission connected in a ring shape. It is received by the device one after another.

FIG. 3 is a flow chart for explaining the processing operation based on the conference control data received by each ATM signal transmission apparatus. Next, this will be explained. In addition,
The received conference control data is stored in a register corresponding to each information content according to a data format defined in advance and used for processing. Note that in the following, FIG.
The conference control data having the format shown in is called a conference control cell.

(1) First, the received conference control cell is
Whether the conference is held or the conference is ended is identified by the flag 401 (step 501).

(2) Next, it is searched whether or not the number of the own terminal device is in the list of conference participating terminals. If there is no own terminal device number, the conference control cell is transferred to the next ATM signal transmission device (step 502).

(3) When the number of the own terminal device is found in the search in step 502, it is determined whether the own terminal device is in a conference waiting state, is already participating in another conference, or is in an abnormal state. The state of the terminal itself is confirmed, and the subsequent processing is executed according to the confirmed state (step 503).

(4) When the self-terminal state is confirmed in step 503 and the self-device is in the conference waiting state and the conference control cell is the conference holding notification, that is, the conference control flag 401 is the conference holding. If it is, the conference control cell described in detail with reference to FIG. 4 is performed, and then the conference control cell is transferred to the next ATM signal transmission device (steps 504 and 50).
5).

(5) If it is confirmed in step 503 that the own terminal is in the conference waiting state and the conference control cell notifies the end of the conference by the flag 401, a control command error occurs. , Transfers the conference control cell to the next device (steps 504 and 506).

(6) In the confirmation of the state of the own terminal in step 503, the own device is in the state of participating in another conference, and the conference control cell notifies the holding of the conference by the flag 401. In this case, the register indicating the state of the device corresponding to the own terminal number of the conference control cell is changed to "participating in another conference", and then the conference control cell is transferred to the next device (steps 507 and 508).

(7) In the confirmation of the status of the own terminal in step 503, the own apparatus is in the state of participating in another meeting, and the meeting control cell notifies the end of the meeting by the flag 401. In this case, the currently held conference number is compared with the conference number for which the conference ending process is performed.
After performing the process of ending the conference, which will be described in detail later,
Transfer the conference control cell to the signal transmission device (step 5).
09, 510).

(8) If the result of the comparison between the currently held conference number in step 509 and the conference number used for the conference ending process does not match, a control command error is detected and the conference control cell is set to the next device. Transfer to (step 51
1).

(9) If a failure occurs in the image / sound code decoding unit or the like in the own device in the confirmation of the own terminal state in step 503, it corresponds to the own terminal number of the received conference control cell. The register indicating the state of the device is changed to the error state, and the conference control cell is transferred to the next ATM signal transmission device (steps 512 and 513).

FIG. 4 is a flow chart for explaining the detailed processing operation of the conference holding processing at the above-mentioned step 505. Next, this will be explained.

(1) First, the conference number is set in the conference number register in the configuration information register provided in the own ATM signal transmission device, and other device numbers that should participate in the conference and be received are configured by the own device. It is set in the conference receiver number register in the information register (steps 601 and 602).

(2) Next, the register indicating the device state corresponding to the own device number in the conference control cell is changed to the participation state, and then the conference control cell is transferred to the next ATM signal transmission device (step). 603).

FIG. 5 is a flow chart for explaining the detailed processing operation of the conference end processing at the above-mentioned step 510, which will be described next.

(1) Initialize another device number to be received set in the configuration information register provided in the own ATM signal transmission device, and perform reception stop processing for the conference data reception function unit (step 701, 702).

(2) Next, the register indicating the device state corresponding to the own device number in the conference control cell is changed to the participation waiting state, and then the conference control cell is transferred to the next ATM signal transmission device ( Step 703).

In the embodiment of the present invention, conference holding and ending are controlled by the procedure of the above-described processing. According to the above-mentioned procedure, the state provided inside each ATM processing transmission device can be processed by comparison with various device configuration information and a register indicating the state. Therefore, hardware processing is performed instead of complicated processor processing. The control processor may perform the processing by the comparison circuit in 1 above, and the control processor may set the register. Therefore, the ATM processing transmission device can have a simple structure.

FIG. 6 is a block diagram showing the functional configuration of the ATM interface unit used in the embodiment of the present invention that enables the above-described processing, and FIG. 7 illustrates the configuration of the data buffer and the in-device configuration information register. It is a figure. 6 and 7, reference numeral 801 is a data buffer and device internal configuration information register, 810 is a data buffer unit, 811.
Is a register unit, and other reference numerals are the same as those in FIG.

A used in the embodiment of the present invention shown in FIG.
The TM interface unit is the address detecting unit 20 of the ATM interface unit in the conventional technique described with reference to FIG.
6, a data buffer and an in-device configuration information register 801 are provided in the subsequent stage, and other configurations are the same as in the case of FIG. The data buffer and in-device configuration information register 801 are provided in the address detection unit 206.
Is a cell for conference control, V in the ATM cell header
After the identification based on the PI / VCI value, the holding and ending of the conference are controlled using the preset device configuration information and the register indicating the current device state. In the following, the data buffer and the in-device configuration information register 801 will be referred to as the conference control cell processing block 801.

The conference control cell processing block 801 is composed of a data buffer unit 810 and a register unit 811 as shown in FIG. The data buffer unit 810 stores all the terminal numbers and the terminal states of the register 404 according to the conference control data format described with reference to FIG. Further, the register unit 811 includes an operation flag register, a conference number register, an own terminal status register,
Consists of a register for the number of participants

The conference control cell is processed as described below in the conference control cell processing block 801 of each ATM signal transmission device.

That is, in the conference control data in the conference control cell, the operation flag 401 and the conference number 403 are first stored in each register unit 811 according to the data format. Next, the register 404 indicating the state of each terminal is stored in the data buffer unit 810 for each terminal number. The number of participants 402 represents the number of registers 404 including a register showing the device status prepared for each conference participant device included in the conference control data, and is therefore set for register search. Further, the conference number 403 is stored and set in the register unit 811 of the conference control cell processing block 801 when a new conference is joined in order to identify the conference in which the own device participates. At the end of the conference, this content is initialized.

The ATM signal transmission device having received the conference control cell performs a process of storing the data content of the conference control cell in the data buffer unit 810 in the conference control cell processing block 801 described above, and the control contents Is set in each device status register unit 811. After that, the ATM signal transmission device starts the receiving process according to the contents of the register 811. The device number to be received is set in the reception block and address detection unit 206, and the demultiplexing unit 2 demultiplexes the multiplexed ATM cells to be received.
It is set to 02. As a result, the decoding processing unit 107 that decodes video and audio can correctly perform necessary processing. The decoding processing unit 107 and the data receiving unit 110 in the latter stage of the ATM interface unit 105 can each be provided with a plurality, and when receiving a plurality of data, that is, a conference using three or more ATM signal transmission devices. When performing the above, each decoding processing unit 107,
The device number to be received is set in the data receiving unit 110.

In the embodiment of the present invention described above, FIG.
The conference control data described above can be used for state management of the ATM signal transmission device connected to the network. In this case, the data format shown in FIG.
It will be treated as follows.

First, in the conference control data format, a management flag is added to the control flag 401 for holding and ending a conference. The number of devices whose status is to be managed is the total number of ATM signal transmission devices connected to the network. These state management data can be sent from any ATM signal transmission device. Then, by using a common conference number in order to distinguish it from normal conference control data, it is possible to simplify the processing of the control data.

When the conference control data for state management as described above is received by each ATM signal transmission device, each ATM signal transmission device changes the state of its own device to the state corresponding to its own device number in the cell. Display in register and transfer to next device.

The state of each ATM signal transmission device can be checked by using the conference control cell. Next, the processing procedure in this case will be specifically described.

Now, an ATM signal transmission apparatus A sets the control flag 401 as a management flag in the data format. Further, the total number of terminals participating in the network is set to the number of participating terminals 402. And
The conference number 403 is a number that is not used as the conference number and is set to a predetermined state management number. All the terminal numbers except the own terminal number are set in the register 404 indicating the state of each terminal. At this time, each terminal state does not indicate anything as an initial state.

The ATM signal transmission apparatus A transmits from the terminal A itself a conference control cell for checking the state of each apparatus constituting the network created as described above. Receiving this conference control cell, each ATM signal transmission device recognizes that it is a management cell from the operation flag, searches its own terminal number from the data format, indicates the status of its own terminal in the register, and Transfer to the terminal. In this way, each ATM signal transmission device sequentially writes the state of its own terminal in the register and transfers it. Therefore, the conference control cells in which the terminal state of each ATM signal transmission device is written are connected in a ring type. It goes around the network.

When the conference control cell is returned to the ATM signal transmission apparatus A which is the transmission source, the terminal states of all the ATM signal transmission apparatuses are written in the content of the conference control cell. Therefore, the state of each terminal can be grasped in the ATM signal transmission device A which has transmitted the cell.

As described above, according to the embodiment of the present invention, the state management of each ATM signal transmission device connected to the network can be performed from any device, and the management control is not a centralized network management system. It is possible to realize a network configuration in which the processing loads of are distributed.

According to the above-described embodiment of the present invention, when a video conference is held between multiple points via a ring-type network, the video conference is held, terminated, and connected to the network. Each AT that composes the system by using conference control data to manage the status of
The ring function unit of the M signal transmission device can process the conference control data, which can reduce the processing load of the processor that analyzes the conference control data.

Further, according to the embodiment of the present invention, the state of the ATM signal transmission device connected to the network can be managed by the conference control data, and each device can be connected to another device connected to the network. Since the state of can be grasped, network management can be performed in a distributed manner.

[0057]

As described above, according to the present invention, it is possible to provide a video conference system in which the processor processing load is reduced, the size of the device is reduced, and the cost is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a video conference system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a conference control data format.

FIG. 3 is a flowchart illustrating a processing operation based on received conference control data in each ATM signal transmission device.

FIG. 4 is a flowchart illustrating a detailed processing operation of the conference holding processing in step 505 described above.

FIG. 5 is a flowchart illustrating a detailed processing operation of the conference ending process in step 510 described above.

FIG. 6 is a block diagram showing a functional configuration of an ATM interface unit used in an embodiment of the present invention that enables the above-described processing.

FIG. 7 is a diagram illustrating a configuration of a data buffer and an in-device configuration information register.

FIG. 8 is a block diagram showing a functional configuration of an ATM signal transmission device which constitutes a video conference system by a ring network according to a conventional technique using an ATM network.

9 is a block diagram showing a functional configuration of an ATM interface section 105. FIG.

[Explanation of symbols]

101 camera 102 microphone 103 encoding processing unit 104 External data generator 105 ATM interface section 106 transmission line 107 Decoding processing unit 108 monitor 109 speaker 110 External data receiver 201 Multiplexer 202 demultiplexer 203 SAR block 204 Physical interface section 205 Optical / electrical converter 206 Address detector 207 Switch 208 control circuit 209 transfer memory 210 Ring Function 211 Control processor 212 data bus 301-304 ATM signal transmission device 801 Data buffer and device configuration information register 810 data buffer section 811 register section

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daiichiro Takashima             216 Totsuka Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture             Ceremony Hitachi Network Platform             Home Business Division (72) Inventor Tomoo Kimura             216 Totsuka Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture             Ceremony Hitachi Network Platform             Home Business Division (72) Inventor Shinteru Ando             216 Totsuka Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture             Ceremony Hitachi Network Platform             Home Business Division (72) Inventor Kenji Kasuga             216 Totsuka Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture             Ceremony Hitachi Network Platform             Home Business Division (72) Inventor Yuji Araki             216 Totsuka Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture             Ceremony Hitachi Network Platform             Home Business Division (72) Inventor Kazuhiro Enomoto             216 Totsuka Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture             Ceremony Hitachi Network Platform             Home Business Division F term (reference) 5C064 AA02 AC13 AC20 AD02 AD16                 5K031 AA05 AA06 BA06

Claims (4)

[Claims] 1. A video conference system for holding a conference between a plurality of signal transmission devices connected in a ring by a network, wherein the signal transmission device is a command for controlling holding and ending of the conference, and a signal for participating in the conference. Conference control having information indicating the number of transmission devices, information indicating a conference number for identifying a conference to realize a plurality of conferences in a network, and information indicating a unique number of a device participating in the conference and a state of the device Control means for using the conference data, receiving the conference control data, control of holding and ending the conference,
Means for selecting the conference data to be received and setting it in the receiving unit connected to the own device, and means for adding the current state of the own device to the own device state information flag in the conference control data. A video conferencing system characterized by being provided. 2. The signal transmission device further comprises means for managing the state of another signal transmission device on the network using the control data.
Video conferencing system described. 3. The signal transmission device, wherein a physical interface for physically matching with a transmission line and a signal in which signals such as image, sound, and data are multiplexed are decomposed into ATM cells, or an ATM cell is used as an original signal. A segment and assembling unit for assembling into a multiplexed signal, and a ring function unit for forming a ring network between the physical interface and the segment and assembling unit, and in the ring function unit, A video conference system comprising a conference control unit that uses conference control data. 4. In a signal transmission device for performing a video conference by connecting a plurality of devices in a ring shape by a network, a physical interface for physically matching with a transmission line and a signal of image, sound, data, etc. are multiplexed. Signal to ATM
A segment and assembling section for disassembling cells or assembling ATM cells into original multiplexed signals;
A ring function unit for forming a ring network between the physical interface and the segment and assembly unit, and a command for controlling holding and ending of the conference, and signal transmission for participating in the conference, in the ring function unit. For conference control having information indicating the number of devices, information indicating a conference number for identifying a conference to realize a plurality of conferences in a network, and information indicating a unique number of a device participating in the conference and a state of the device A signal transmission device comprising a conference control means using data.