JPH04246993A - Multi-spot image communication system - Google Patents

Abstract

PURPOSE:To reduce the size of hardware, to achieve high performance of the system, to miniaturize a communication terminal equipment and to increase the profitability of the equipment even when the number of simultaneously displayed spots is increased. CONSTITUTION:In a multi-spot connection device 2 an image received from every image communication terminal equipment 1 is supplied through an input switch part 21 to a transmission unit 22 to combine and multiplex plural pieces of image information. At the transmission unit 22, the system accumulates every piece of the image information in separate buffers 23 and, by switching the plural buffers and reading out the information, the plural pieces of information to be combined are multiplexed. The multiplexed information is then transmitted to a necessary terminal 3 through an output switching part 25. Also, in order to prevent a delay due to the increase of the data in the buffer 23 for accumulating the image information, a fill-frame is inserted into the image communication terminal equipment 1 to effectively decrease the speed transmitting the data from the image communication terminal equipment 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipoint image communication system for communicating images between a plurality of remote points. In recent years, image communication systems such as TV conferences have evolved from one-to-one communication to multipoint connections, and there is a trend toward higher functionality such as simultaneous display at multiple points. On the other hand, with image communication terminal equipment, normally the sending side only needs to send one image from its own terminal, but the receiving side needs to receive images from multiple points simultaneously, which increases the hardware scale. However, there is a tendency for the hardware required to multiplex and transmit multiple images to increase even within a multipoint connection device, and there is a desire to make the system more compact and economical. Additionally, it is essential that the system has a quick response (low delay time).

0002

2. Description of the Related Art FIG. 21 shows a conventional system configuration in which a plurality of image communication terminal devices realize multipoint connection via a multipoint connection device. In Figure 21, 90 is each point 1 to N
A transmitting side communication terminal device 91 provided at each point receives image information between the transmitting side communication terminal devices at each point, multiplexes the images, and sends the images to the receiving side communication terminal device at each point. A point connection device 92 is a communication terminal device on the receiving side at each point. Note that, depending on each location, there are locations that are equipped with communication terminal devices for both transmission and reception, and locations that are equipped with only communication terminal devices for either transmission or reception (unidirectional).

[0003] A communication terminal device (transmission side) 90 at each location transmits an image signal input from a camera 904 to an image transmission section 902.
The control unit 901 generates a header to be added to the image information, and the multiplexing unit 903 transmits it to the multipoint connection device 91 in blocks. In the multi-point connection device 91, image information from each point is sent to a receiving section 91 provided corresponding to a transmission path.
1 and multiplexed by the switch unit 913 according to a predetermined multiplexing pattern under the control of the control unit 912. That is, the transmitted images of which point and which point are multiplexed according to a multiplexing pattern indicating which point is to be received and outputted from the corresponding transmitter 914 to each point.

[0004] Multiplexing at this time is performed in units of time slots in a line frame format, and the line frame format of the image information transmitted from the multipoint connection device to each communication terminal is shown in FIG. That is, each time slot is associated with a specific point, and in each time slot, a header is added to the image information (block) from the corresponding point, and a plurality of pieces of image information are transmitted. The communication terminal device on the receiving side at each point receives the multiplexed signal in the above line frame format (Fig. 22), and the separation unit 921 performs time slot separation to transfer the image information of each point on the transmitting side to the point. The image is supplied to an image receiving section 922 provided separately. The image receiving section 922 decodes the block-by-block image information received from each point under the control of the control section, and supplies the image output to the display section 923. The display unit 923 displays multiple points simultaneously on a plurality of monitors or a single monitor.

FIG. 23 shows a configuration diagram of a conventional example of a communication terminal device on the receiving side. In FIG. 23, each information block separated by point for each time slot from the separation unit 921 is input to the corresponding image reception unit 922, and the reception operation is controlled by the control unit 9220. The header of the image information is detected by a header detection unit 924, and the header timing (the head position of each image information block) is notified to the control unit 9220. From this, the control unit 9220 controls the image decoding unit 9222 to decode each information block. Generally, information on previously received image information blocks is used for image decoding (in the case of differential encoding method for band compression), but the past information necessary for decoding is stored in the decoding information history management section. Storage and updating are performed in 9223, and the control unit 9
220 performs reference and update, and obtains parameters for controlling the image decoding unit 9222. The decryption result is supplied to the decryption information history management section 9223 and displayed on the display section 923.
is stored in the corresponding image memory 9230. Display section 9
At 23, the data in each image memory 9230 is processed by a video processing unit 9231 and displayed on each monitor 93.

[0006]

[Problem to be solved by the invention] Figures 21 to 23 described above
In the conventional method shown in Figure 1, it is necessary to parallelize the image receiving section in accordance with the number of points to be displayed simultaneously on the communication terminal device on the receiving side of each point, and the hardware scale increases as the number of points to be displayed simultaneously increases. Therefore, it is difficult to achieve higher functionality while simultaneously making communication terminal equipment smaller and more economical.

[0007] Furthermore, as the number of points increases, the delay time that occurs from reception to transmission accumulates in the image memory (or buffer) provided in the multipoint connection device, which slows down the response of the system and causes the image memory to fail (overflow). There was a problem. Figure 24 shows the problems with this image memory.
To explain using FIG. 24, an example is shown in which images of point A and point B are stored in image buffers M1 and M2 sequentially, respectively, and the information of both images is alternately switched by the selector SEL and sent to point C. There is. At this time, the transmitted images from point A and point B are sent at a speed of X/2 and written into the image buffers M1 and M2 at a speed of X/2.

[0008] In order to faithfully transmit both images from points A and B, the readout speed by the selector SEL and the transmission speed to point C must be set to X. In this case, if data accumulates in image buffers M1 and M2 (the amount of written data increases due to delays in write control, etc.), it increases sequentially and cannot be decreased (transmission speed X to point C is (assumed to be limited by bandwidth). Therefore, if the accumulated data increases and exceeds the capacity of the image memory, a failure will occur.

The first object of the present invention is to be able to reduce the hardware scale compared to the conventional system even if the number of points displayed simultaneously increases, and to improve the functionality of the system and to reduce the size and economy of communication terminal equipment. The purpose of the present invention is to provide a multipoint image communication system that can realize A second object of the present invention is to provide a multipoint image communication system that can speed up the response of the system without increasing the capacity of the image information storage memory in the multipoint connection device.

0010

[Means for Solving the Problems] FIG. 1 is a first principle block diagram of the present invention, and FIG. 2 is a second principle block diagram of the present invention. In FIG. 1, 1 is a transmitting side image communication terminal device, 2
3 is a multipoint connection device, and 3 is an image communication terminal device on the receiving side. In the image communication terminal device 1 on the transmitting side, 10 is a multiplexer for multiplexing control information and an image information block in which a header (including point information) is added to each encoded image data transmitted from this point. Department. In the multipoint connection device 2, 20 is a control section, 21 is an input switch section, 22 is a transmission unit, 23 is a buffer that stores image information input from a plurality of image communication terminal devices, 24 is a multiplexing section, 25 is an output switch section. In the image communication terminal device 3 on the receiving side, 30 represents a separation unit that separates control information and image information of multiple points. In addition,
The image communication terminal equipment at each location usually has both a transmitting side mechanism and a receiving side mechanism, but it is equipped with only one mechanism (only for transmitting images or only for receiving images). In some cases.

In FIG. 2, 1 is an image communication terminal device on the transmitting side, 12 is an image transmitter, 123 is a fill frame generating means, 2 is a multipoint connection device, 23 is a buffer, and 24 is a selector (the multiplexer shown in FIG. 1). 230 is a storage amount monitoring section. The present invention uses a multipoint connection device to supply images received from each image communication terminal device to a transmission unit that combines and multiplexes a plurality of image information using an input switch section, and stores each image information in a separate buffer in the transmission unit. By switching and reading multiple buffers, multiple image information to be combined is multiplexed and transmitted from the output switch section to the required terminal. Furthermore, in order to prevent delays due to an increase in data in the buffer that stores image information, a fill frame is inserted in the image communication terminal to effectively reduce the data rate transmitted from the image communication terminal.

0012

[Operation] In the first principle configuration diagram shown in FIG. 1, the image communication terminal device (hereinafter simply referred to as a communication terminal) 1 on the transmitting side receives image information obtained by encoding an image signal from an imaging camera (not shown). A multiplexing unit 10 multiplexes information in which a header for identifying the delimiter is added and control information from a control unit (not shown) of the communication terminal, and transmits the image information block unit to the transmission path. In this case, the location information of the communication terminal is added to the header (it may not be added, which will be explained in the embodiment section). In the multipoint connection device 2, a control section 20 receives control information from each transmission side communication terminal 1, and image information is supplied to an input switch section 21. The control unit 20 outputs control information to the transmission path to the communication terminal 3 on the receiving side, and also controls each unit in the multipoint connection device 2 .

When the image information from the communication terminal 1 is input to the input switch unit 21, its header is decoded by the control unit 20, and the input switch is configured to input the image information at that point to the buffer 23 of the transmission unit 22 that requires it. The section 21 is switched and controlled. Each transmission unit 22 performs a process of combining and multiplexing a plurality of pieces of image information, and for this purpose, a buffer 223
The image information written in each buffer is read out and multiplexed in the multiplexing section 24. The multiplexed image information from the transmission unit 22 is supplied to the output switch section 25, and the output switch section 25 is connected to the control section 20.
The information is then switched to the communication terminal 3 that made the request. In this case, the output switch section 25 is switched and connected so as to transmit the same multiplexed signal to a plurality of different communication terminals 3 on the receiving side.

When the communication terminal 3 on the receiving side receives the multiplexed image information blocks from a plurality of terminals sent from the multipoint connection device 2, it is received and decoded in the demultiplexing section 30, and then distributed and decoded by the distribution decoding means. The decoded image information is then distributed by the distribution means into image information corresponding to the transmitting communication terminal, stored in an image memory (not shown), and displayed. When displayed, multiple pieces of image information are combined onto one screen or displayed individually on multiple screens.

Next, the second basic configuration of the present invention shown in FIG. 2 will be explained. When there are n communication terminals 1 on the transmitting side, the image transmitter 12 in each communication terminal 1 receives encoded image information and transmits it to the multipoint connection device 2. The image transmitter 12 sends a fill frame (all “0” or all “1”)
When a fill frame is input from the fill frame generating means 123, a fill frame is inserted in place of the image and transmitted. In this case, the circuit for image encoding The code length (compression encoded data) of (not shown) can be changed.

The fill frame generating means 123 generates an image signal at a ratio of α (α<1) to the transmission speed X/n (n is an integer) according to the input speed setting signal (this is α). Outputs a fill frame so that it is transmitted. In other words, the ratio of fill frames in the transmitted signal is (1-
Fill frames are inserted at a period such that α). As a result, the effective image information transmission speed is (X/n)
・It becomes α.

When image signals are sent from a plurality of (n) transmitting side communication terminals 1 to the multipoint connection device 2, the multipoint connection device 2 removes the fill frame as invalid data and outputs the image information (including the control signal). ) and store them in the respective buffers 23. The multiplexing unit 24 multiplexes the information in the multiple buffers 23 and sends it out, but even if the multiplexing unit 23 multiplexes the information in multiple (n) buffers 23 at a speed of X, the information is written to each buffer 23. The speed of image information is (
X/n)·α, the readout speed is always faster and the image information does not increase in the buffer 23.

In the above explanation, the communication terminal 1 instructs the speed setting signal in advance to determine the speed, but the multipoint connection device 2 monitors the storage capacity of the buffer 23 and sends a fill request when it exceeds a predetermined value. The configuration may include a storage amount monitoring unit 230 that generates a signal requesting the communication terminal 1 to: In this case, communication terminal 1 receives this fill request (
(sent as control information), the image transmitter 12
A speed setting signal (α) is output for the speed setting signal (α). In response to the input of this speed setting signal, the communication terminal 1 inserts a fill frame into the transmission signal from the fill frame generating means 123. In this way, it is possible to adjust the effective transmission speed of the communication terminal on the sending side in accordance with the amount of storage in the buffer on the multipoint connection device 2 side, thereby preventing data corruption in the buffer and increase in delay time.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows a system configuration diagram to which embodiments 1 and 2 based on the first principle configuration of the present invention are applied. In FIG. 3, an image communication terminal device (displayed as a communication terminal) 1 is provided as communication terminals A to D and X at each point 1 to 4 and N, respectively, and is connected to a multipoint connection device 2 via a transmission path, respectively. ing. The communication terminal 1 is connected to the multipoint connection device 2 by a bidirectional transmission path, and the transmission path on the receiving side is connected to the separation unit 13, and image information, control information, and image signals for each communication terminal on the sending side are transmitted. The control information is sent to the control unit 10.
The image information is received by the image receiving section 14, and each image signal is controlled by the display section 15 and displayed on each monitor 17. The image from the camera 16 provided in the communication terminal 1 is sent to the multiplexing unit 11 via the image transmitting unit 12.
The multiplexing unit 11 multiplexes the control signal from the control unit 10 and the image information and transmits the multiplexed signal to the transmission line on the transmitting side.

Next, the configuration of the first embodiment applied to the system configuration of FIG. 3 will be explained using FIGS. 4 to 9. Figure 4 is an example configuration diagram of a communication terminal (transmission side), Figure 5 is an example configuration diagram of a multipoint connection device, Figure 6 is an example configuration diagram of a communication terminal (reception side), and Figure 7 is a frame diagram on a transmission path. A diagram showing the format, FIG. 8 is an explanatory diagram of writing to a buffer and multiplexing operation by a selector, and FIG. 9 is an example of a control operation sequence by control communication between a communication terminal and a multipoint connection device.

The communication terminal on the transmitting side shown in FIG.
The image information from 6 is preprocessed by the preprocessing unit 120 of the image transmitting unit 12, then encoded by the image encoding unit 121, and a header adding unit is added to each block of image information (basic unit of encoded data). At step 122, a header including point information on the transmitting side (point information assigned to the transmitting communication terminal) is added and output to the multiplexing section 11. Control information to be transmitted from the control unit 10 to the multipoint connection device is transmitted to the multiplexing unit 11.
The multiplexing unit 11 multiplexes the control information and image information from the control unit and transmits the multiplexed signal to the transmission path.

The line frame format when multiplexed from the communication terminal and transmitted to the multipoint connection device is shown in A of FIG.
．． Shown below. The first time slot 0 is used as a control communication path, and control information from the communication terminal to the multipoint connection device is sent through this path. A predetermined number of time slots starting from time slot 1 form an image information path, in which an image information block is combined with a header containing point information and transmitted continuously (however, the time slot and each image information (The block lengths do not correspond one-to-one.) In the signal from this communication terminal to the multipoint connection device, only the image information block of one point is transmitted. Also, the image information block is shown in C. It is configured as shown in .

In the multipoint connection device 2 shown in FIG. 5, 20 is a control section, 21 is an input switch section, and 220 is a header detection/detection section.
Switching processing units 1 to Z, 23 store images from different communication terminals, and buffers 1 to 3, 24 store selectors 1 to 24, which multiplex images from each buffer 1 to buffer 3.
A selector Z (corresponding to the multiplexing unit 24 in FIG. 1), 22
0, 23, and 24 constitute a transmission unit (22 in FIG. 1). Further, 25 is an output switch unit that performs switching connection in order to supply the multiplexed image information output from each selector 1 to Z to a requested communication terminal, and 26 is an output switch unit for controlling image information and control from each transmitting side communication terminal. The information receiving section 27 is a transmitting section that transmits image information and control information to each receiving communication terminal.

To explain the operation of FIG. 5, signals sent from each transmitting communication terminal 1 are received by the receiving section 26 and separated into control information and image information. Control information (a request for connection to a multipoint connection device, a request for a point from which to receive an image, etc.) is output to the control section 20, and image information is supplied to the input switch section 21. The control unit 20 determines which selector 24 the image information output from each receiving unit 26 should be stored in the buffer 23, and outputs the signal of each receiving unit 26 to the buffer 23 of the necessary transmission unit according to the judgment. It controls the switching of the input switch section 21 so that the input switch section 21 performs the same operation, and also instructs the header detection/switching processing section 220 from which point the image information should be taken in. The input switch section 21 is constituted by a switch element, and each output port side can independently select an input side port, and one buffer 23 is connected to each output port side. Therefore, image information from any receiving section 26 can be input to a designated buffer 23 by setting the switching state of the input switch section 21.

A header detection/switching processing unit 220 and a buffer 23 whose number of buffers is equal to the number of points to be displayed simultaneously.
(In the example of FIG. 5, the buffer for three planes) and the selector 24 constitute a set of transmission units, and generate one multiplex pattern of image information. To explain with a specific example, terminal A
, if you wish to receive images of terminal B and terminal C, terminal B
If you wish to receive images from terminals A and C, and if you wish to receive images from terminals A and B at terminal C, each transmission unit uses two buffers 23, and the first transmission unit receives images from terminals B and B. The image information of terminal C, the second unit transfers the image information of terminals A and C, and the third transmission unit transfers the image information of terminals A and B to the two-sided buffer 23.
Accumulate in.

The specific operation at this time is that each buffer 23 and the receiving section 2 corresponding to each point are operated according to instructions from the control section 20.
The input switch section 21 is set to switch so that the connection between the two transmission units is established, and at the same time, the output switch section 25 is set so that the output of each transmission unit is correctly transmitted to each terminal. In addition, the header detection/switching processing section 2 of each unit
20 receives an instruction from the control unit as to which communication terminal should store the image information in which buffer, recognizes the beginning of the header of the image information block, detects the break between the image blocks, and identifies the point information in the header. Then, each image information is written into the buffer 23 in units of image information blocks.

In this way, one header detection/switching processing unit 220 writes image information from a plurality of communication terminals 1 to be combined into a plurality of buffers 23, respectively, in units of image information blocks. The information in the buffer 23 is read out by the selector 24 in parallel with the write operation. Buffer 23 within this one transmission unit
The multiplexing operation by writing to and reading by the selector 24 will be explained with reference to FIG. However, in this example, N buffers are provided.

In FIG. 8, after receiving image information from each communication terminal (sending side) at points 1 to N,
The data is allocated to individual buffers 23 and sequentially written to each location as shown in the figure. When one block of data is accumulated in the buffer, the header detection/switching processing unit 220 (Figure 5)
sets the selector 24 to start reading from one of the multiple buffers in the unit (the one for which one block's worth of data has been accumulated first), and when the reading of one block's worth of data is completed, data is transferred to the other buffers. If one block or more of data has been accumulated, the selector 24 is switched to start reading the buffer. Note that the image information has a variable length, and if data for one block or more has not been stored in another buffer after reading one block of data, reading from the same buffer is continued. In this way, in the example of FIG. 8, the selector 24 outputs a signal in which image information of each buffer is sequentially multiplexed.

The output signal of the selector 24 is input to the output switch section 25 shown in FIG. The output switch section 25 is configured in the same manner as the input switch section 21, and is set by the control section 20 to output the output signal from each selector 24 to any necessary output port, and outputs the output signal from each selector 24 to a terminal device at each output port. A corresponding transmitter is connected. In this case, the output of one selector 24 can be output to multiple transmitters 27 at the same time (when viewing the same image on multiple communication terminals). The line frame format of the signal transmitted from the multipoint connection device 2 to the communication terminal is shown in B. in FIG. Shown below. As shown in the figure, like the signal in the opposite direction (A. in Figure 7), time slot 0 is the control communication path for this direction signal, but in time slots 1 to N, image information blocks from multiple points are sequentially transmitted. transmitted.

Next, the configuration of the embodiment of the communication terminal (receiving side) shown in FIG. 6 will be explained. In FIG. 6, the signal transmitted from the multipoint connection device via the transmission path is transmitted to the separation unit 13 of the communication terminal.
The control information of the control communication path (time slot 0) is supplied to the control unit 10, and the image information block is input to the image receiving unit 14. For the image information blocks of multiple points, the header detecting section 140 detects the header, analyzes the transmitting side point, and notifies the control section 10 of the result. Control unit 10
Before starting decoding of each image information block unit, information for decoding the image information of the communication terminal at the corresponding point stored in the decoding information history management unit 142 (image information received in the past) , and controls the image decoding unit 141 to perform decoding. At the same time, the decryption information history is updated. The decoded image is transferred to the image memory 150 for images corresponding to the transmitting terminal (transmitting point) provided on the display section 15 by switching the selector 143. The video processing unit 151 performs processing for displaying the contents of each image memory 150 and displays them on the corresponding monitor 17.

An example of a control operation sequence based on control communication between a communication terminal and a multipoint connection device in the first embodiment shown in FIG. 9 will be explained. Although FIG. 9 only shows communication terminals A and B as communication terminals connected to the multipoint connection device, other communication terminals (not shown) are also connected. First, prior to starting communication, a connection request is made from the control unit of each communication terminal to the control unit of the multipoint connection device via the control communication path (1 in FIG. 9). In response, the control unit of the multipoint connection device allocates a point number and grants connection permission via a control communication path (same 2). After a certain period of time, when multiple communication terminals to participate in the multipoint connection are determined, the control unit of the multipoint connection device switches the input switch unit and the output switch of the multipoint connection device in a predetermined connection form, as explained in FIG. 5 above. section, and the switching processing section (same as 3). For example, a connection configuration may be adopted in which images of all terminals except the own communication terminal are transmitted to each communication terminal.

Next, the multipoint connection device notifies each communication terminal of the information on the participating terminals (connection point information) through control communication (4), and instructs to start transmission (5). On the transmitting side of each communication terminal, when the control unit receives the transmission start instruction, the transmitting side writes the point number in the image information and transmits it (6). The image information from each point is transmitted through the transmission line (7), and the image information from each point is received by the multipoint connection device and stored in a buffer (8). Next, the multipoint connection device multiplexes the accumulated image information of each point and retransmits it (Same 9). This image information from multiple points is transmitted to each communication terminal (Same 10), and the communication terminal starts receiving and displaying the image (Same 11).

[0033] If the communication terminal wishes to receive images including images of other terminals instead of the images of terminals at multiple points that are currently being displayed, multiple display switching requests are sent via control communication, as in communication terminal B in Fig. 9. Notify the point connection device (12, 13). Upon receiving this information, the control unit of the multipoint connection device reconfigures the input switch unit, output switch unit, and switching processing unit. One of the buffers in the combination of processing unit and selector) is reset to change to the image of the terminal that requested the display (14), and permission is notified through control communication (15). After this, communication of image information is restarted again. In this way, a display image can be freely selected by control communication from the terminal side.

FIG. 10 is a block diagram of a multipoint connection device according to the second embodiment. In this second embodiment, in the system configuration shown in FIG. 3, the configuration of the multipoint connection device is different from that in the first embodiment, and in the configuration of the multipoint connection device of the first embodiment (FIG. 5), each transmission unit (220, 23 and 24) in that a header rewriting section 28 is provided. In this configuration, the header rewriting section 28 in the multipoint connection device writes point information in the header section of each passing image information block according to instructions from the control section 20. Specifically, the control unit 2
0 notifies the header rewriting unit 28 of each unit of point information to be written in each buffer 23 within the unit. The header rewriting unit 28 determines which buffer 23 is currently available from the header detection/switching processing unit 220 of each unit.
Upon receiving notification as to whether or not is selected and notification of the header section passage time slot, a predetermined value is entered in the header section. The control section 20 manages which communication terminal's image data is to be stored in each buffer, and instructs the header rewriting section 28 about the corresponding point number.

[0035] Thereby, writing of the point number assigned to the image information block from each communication terminal is automatically performed within the multipoint connection device. This eliminates the need to allocate a point number from the multipoint connection device to each communication terminal through control communication at the start of connection, which was executed in the control operation sequence of the first embodiment shown in FIG. It is possible to eliminate the function of writing the point number in the header of each image information block. Other controls are the same as in the first embodiment.

FIG. 11 shows a system configuration diagram to which the third and fourth embodiments based on the first principle configuration of the present invention are applied. The system shown in Fig. 11 has a configuration in which a plurality of multipoint connection devices are provided, a communication terminal under management is connected to each multipoint connection device, and the multipoint connection devices are connected to each other via a transmission path. The number of terminals that can participate in communication can be expanded by preparing and interconnecting multipoint connection devices. 2a to 2c in FIG. 11 are multipoint connection devices, and each communication terminal is equipped with a camera and a monitor.

Next, the configuration of the third embodiment applied to the system configuration of FIG. 11 will be explained using FIGS. 12 to 14. 12 is a block diagram of a multipoint connection device according to the third embodiment, FIG. 13 is an example of image information communication operation between each multipoint connection device, FIG. 14 is an example of a line frame format between multipoint connection devices, and FIG. 15 1 is a diagram showing an example of interconnection of multipoint connection devices; FIG. The configuration of the multipoint connection device of Example 3 shown in FIG. 12 is as shown in FIG.
In contrast to the configuration of Embodiment 1 shown in , a receiving section 26 and a header analysis section 260 for the multipoint connection device, and an image information block separation section 29 are provided on the receiving side for interconnection of the multipoint connection devices. and transmitting section 2 for other multipoint connection devices on the transmitting side.
It is distinctive in that it has a number 7.

To explain the operation, the receiving section 26 for the multipoint connection device separates control communication data and image information, similar to that for the terminal device, and supplies the former to the control section and the latter to the separating section 29. be done. The header analysis section 260 is the control section 2
0, the point number in the header of each image information block passing through the receiving section 26 is analyzed, and the separating section 29 is switched to instruct which output port to send the data to. That is, the separation unit 29 separates a plurality of image information blocks and performs an operation of switching which of the plurality of input terminals to the input switch unit 21 to output the separated image information blocks according to instructions from the header analysis unit 260.

Further, the separation unit 29 separates multiplexed data of multipoint image information supplied from the multipoint connection device and supplies the separated data to the input switch. Figure 1 shows the line frame format of multiplexed data of image information from this multipoint connection device.
4. As shown in the figure, in this case as well, time slot 0 is assigned as the control communication path, and time slots 1 to N are assigned image information from the multipoint connection device (in this case, image information from point 1 and point 2 are multiplexed). communication path is assigned. In addition, in the transmitting unit 27 for multipoint connection devices in FIG. 12, control communication data from the control unit 20 and the output switch unit
The image information data is multiplexed and sent to the transmission path.

Next, the operation of the third embodiment will be explained with reference to FIG. 13 for an example of interconnection of the multi-point connection device shown in FIG. 15. In the case of interconnection of multipoint connection devices in Figure 15, terminal C (point 3) wishes to receive images from terminal A (point 1) and terminal E (point 5), and terminal D (point 4) wishes to receive images from terminal B (point 4). Point 2
) and terminal F (point 6). In this case, as shown in FIG.
b, the image information of terminal A (point 1) and terminal B (point 2) is transmitted from the multipoint connection device 2a, and the image information of terminal E (point 5) and terminal F (point 6) is transmitted from the multipoint connection device 2c. are respectively transmitted in the format shown in FIG.

Multipoint connection device 2 in multipoint connection device 2b
The header analysis unit 260 (FIG. 12) corresponding to point a
and the point number of point 2 and the input port number of the input switch to be separated and outputted using the separation section 29 (from the control section 20 in FIG. 12). Further, the header analysis unit 260 corresponding to the multipoint connection device 2c receives similar instructions regarding points 5 and 6. Each header analysis section 260 reads the point number in the header of each image information block, controls the separation section 29, and inputs each image information of points 1 and 2 or points 5 and 6 to a predetermined input switch in units of blocks. Switch to the input port of section 21 and input. Note that the point number entry in the header is performed at each terminal on the sending side or within the multipoint connection devices 2a and 2c.

The input switch section 21 also connects the input port designated for point 1 to buffer 1 of unit 1 of the multipoint connection device 2b, the input port designated for terminal 6 to buffer 2, and connects the input port designated for terminal 6 to buffer 1 of unit 2. 2 designated input ports,
The control unit 20 (FIG. 12) instructs the buffer 2 to be connected to the input port designated by the terminal 6. Further, the output switch unit 25 connects the output of the unit 1 to the terminal C and the output of the unit 2 to the terminal D.
Indicated from 0. In this way, the multipoint connection device 2
The control section in b controls each section within its own device to realize multiplexing of images from multiple points requested by each terminal. By switching the reading of the buffer 23 of each unit, the terminal 2c receives the image information of terminals A and E, and the terminal D receives the image information of terminals B and F from the multipoint connection device 2b.
B in FIG. The image is retransmitted in the same format as , and the specified image reception is realized.

The display point switching process is executed by the multipoint connection devices 2a to 2c communicating with each other and working together. For example, in FIG. 13, if terminal C wishes to receive images of terminal G (point 7: accommodated in multipoint connection device 2c) instead of terminal E (point 5: accommodated in multipoint connection device 2a), terminal C The control unit notifies the control unit of the multipoint connection device 2b through control communication. The control section of the multipoint connection device 2b outputs the image information block of point 7 to the port of the corresponding input switch section instead of point 5 (terminal E) to the header analysis section 260 corresponding to the multipoint connection device 2c. Reconfigure it so that

Furthermore, the control unit of the multipoint connection device 2b determines that the terminal E and the terminal G are accommodated in the same multipoint connection device 2c (at the start of communication, each multipoint connection device terminal information is exchanged and notified to all terminals), and the control unit of the multipoint connection device 2c is notified by control communication to multiplex the image of terminal G instead of the image of terminal E. do. Multipoint connection device 2c that received this
The control unit reconfigures the input switch unit and header detection/switching processing unit (220 in FIG. 12) within the own device, and changes the multiplexing pattern of images to the multipoint connection device 2b to terminal F+terminal G. In this way, terminal C can receive images of terminal A and terminal G.

Next, the configuration of the fourth embodiment applied to the system configuration of FIG. 11 will be explained using FIGS. 16 to 18. FIG. 16 is a block diagram of a multipoint connection device according to the fourth embodiment, FIG. 17 is an example of communication operation of image information between each multipoint connection device, and FIG. 18 is an example of interconnection of multipoint connection devices according to the fourth embodiment. FIG. The configuration of the multipoint connection device of Example 3 shown in FIG. 16 is as follows:
Regarding the configuration of the multipoint connection device of Example 3 shown in FIG. 12,
A feature is that a direct connection path P is provided between the input switch section 21 and the output switch section 25 without passing through a buffer, thereby reducing the connection processing time when interconnecting multipoint connection devices.

The configuration of this fourth embodiment will be explained using an example in which images of communication terminal A and communication terminal B of multipoint connection device 2a are desired to be received by all of multipoint connection devices 2b and 2c, as shown in FIG. . In this case, multipoint connection devices 2a to 2c
The connection route is shown in FIG. Note that FIG. 17 includes a configuration in which the communication terminals A' and B' in the multipoint connection device 2a also receive images of the communication terminals A and B. To explain the operation, the image information of communication terminal A and communication terminal B from the multipoint connection device 2a is transferred to the multipoint connection device 2b from B. in FIG. It will be sent in a similar format. In the multipoint connection device 2b, the control unit 20 controls the input switch unit 21 and the output switch unit 25 as shown in FIG. In contrast, a direct connection path P that does not go through the buffer 23 is used to connect the receiving unit 26 from the multipoint connection device 2a. In this way, as shown in FIGS. 16 and 17, the image information transmitted from the multipoint connection device 2a is relayed as is to the communication terminals C and D and the multipoint connection device 2c.

Further, as shown in FIG. 17, the input switch section and the output switch section of the multipoint connection device 2c are connected to the communication terminal E.
A direct connection path that does not go through a buffer is connected to the transmission unit to the communication terminal F and the reception unit from the multipoint connection device 2b, and the image information transmitted from the multipoint connection device 2b is relayed as is. do. In this way, it is possible to prevent wasteful delay time from occurring due to the use of buffers, and it is also possible to reduce processing delay time for multi-stage connections of multi-point connection devices.

FIG. 19 shows a configuration diagram of a first embodiment corresponding to the second principle configuration (see FIG. 2) of the present invention, and FIG. 20 shows a configuration diagram of a second embodiment. In FIG. 19, 1 is an image communication terminal device (displayed as a communication terminal), A and B are communication terminals on the sending side, C is a communication terminal on the receiving side, 2 is a multipoint connection device, 1
0 is a control unit, 23 is a plurality of (two in this example) buffers, and 24 is a selector (indicated by SEL). Note that the configuration of this multipoint connection device 2 includes, although not shown, the following:
Similar to the other embodiments 1 to 6 described above, this is provided in the transmission unit 22 (comprised of a header detection/switching processing section 220, a buffer 23, and a selector 24) connected via a receiving section and an input switch section.

In this embodiment, the transmission rate (transmission speed) from the multipoint connection device to the communication terminal C on the receiving side is 512K.
A case is shown in which the transmission rate of each communication terminal is 256 Kbps (bps (kilo bits per second)). The communication terminals A and B on the sending side are as shown in FIG. 4 of the above embodiment 1.
However, only the control unit 10 and encoding unit 121, which are configurations related to this embodiment, are shown, and the others are omitted from the illustration. In each of the communication terminals A and B, an image signal such as a TV is input to the encoding unit 121, and α=0.9 is input to the control unit 10 as a speed setting signal. Control part 1
0 calculates that α×256 Kbps is approximately 230 Kbps, and operates the encoding unit 121 at an effective transmission rate of 230 Kbps. That is, by inserting fill frames at a fixed ratio into transmission data at a rate of 256 Kbps, image information (including headers) at 230 Kbps is effectively transmitted.

When the multipoint connection device 2 receives this, the receiving section (not shown) discards (ignores) the fill frame, stores only the image information in the buffer 23, and multiplexes it using the selector 24. become At this time, it is transmitted to the communication terminal C on the receiving side at a transmission rate of 512 Kbps, so even if 230 Kbps image information is sequentially stored in the two buffers 23, the combined speed of both is 4
Since the speed is 60 Kbps, the amount of information stored in the buffer 23 will not increase, and even if it temporarily increases for some reason, the amount of information stored can be gradually reduced.

Next, corresponding to the second principle configuration of the present invention,
A configuration diagram of the second embodiment will be explained with reference to FIG. 20. This figure 20
19, 1 and 2 represent communication terminals and multipoint connection devices, and A to C represent communication terminals similar to those in FIG. , a buffer retention amount detection circuit 23 is provided in the multipoint connection device 2.
1 and a comparison circuit 232.
It is the same as FIG. 19 except that 0 is provided.

To explain the operation, as in FIG. 19, image information is transmitted from communication terminals A and B, and both image information are received by the multipoint connection device 2 and stored in the respective buffers 23. The contents are sequentially read out by the selector 24 and a multiplexed signal is transmitted to the communication terminal C. The amount of data accumulated in the buffer 23 is determined by the retention amount detection circuit 231.
, it is detected by calculating the difference between the write address (representing the write position) and the read address (representing the read position). The detected retention amount is compared with a certain threshold T in a comparator circuit 232, and this value T
When the number exceeds 1, the control unit 20 of the multipoint connection device 2 sends a fill request to the corresponding communication terminal 1 on the transmitting side by control communication.

When the communication terminal 1 on the transmitting side receives this fill request at the control unit 10, it sends a fill sending instruction to the line unit 123, and causes the line unit 123 to send out a fill frame. Note that the line unit 123 outputs all “1” or all “0” at predetermined intervals in response to the generation of this fill sending instruction.
It is equipped with a fill frame generation mechanism consisting of, etc. At this time, the control unit 10 of the communication terminal 1 sends a fill control signal to the encoding unit 121 to control the encoding unit 121 to perform fill control encoding. In this fill control encoding, when encoding an image signal, compression encoding is performed such that even if a fill signal is inserted, it can be reproduced on the receiving side. This fill frame is discarded at the receiving section (not shown) of the multipoint connection device 2. As a result, a fill frame is formed on the transmission path, so that the effective transmission speed is reduced and the amount of data retained in the buffer 23 of the multipoint connection device can be reduced. When the accumulated amount of the buffer becomes small, the transmission of fill requests from the multipoint connection device 2 to the communication terminal 1 is stopped, and therefore the transmission of fill frames in the communication terminal 1 is stopped.

[0054]

Effects of the Invention According to the present invention, even if the number of points at which simultaneous display is realized increases in the communication terminal devices (receiving side) at each point, which is the majority in the system, the hardware scale can be reduced by sharing the image receiving section. The amount of increase can be reduced compared to the conventional method. Furthermore, it is possible to make communication terminal equipment smaller and more economical while increasing the functionality of the system. Furthermore, even if a plurality of multipoint connection devices are interconnected to expand the system scale, mutual image communication can be performed between the communication terminals accommodated in each multipoint connection device. Furthermore, when multipoint connection devices are interconnected, unnecessary delay time can be prevented from occurring. In addition, in multipoint image communication using multipoint connection equipment, it is possible to prevent an increase in the retention amount (increase in delay time) and a failure (overflow) of the buffer for image multiplexing installed in the multipoint connection equipment. This makes it possible to configure a system with quick response.

[Brief explanation of the drawing]

FIG. 1 is a first principle configuration diagram of the present invention.

FIG. 2 is a second principle configuration diagram of the present invention.

FIG. 3 is a system configuration diagram to which Example 1 and Example 2 are applied.

FIG. 4 is an example configuration diagram of a communication terminal (sending side).

FIG. 5 is a configuration diagram of an embodiment of a multipoint connection device.

FIG. 6 is an example configuration diagram of a communication terminal (receiving side).

FIG. 7 shows a frame format on a transmission path (line).

FIG. 8 is an explanatory diagram of writing to a buffer and multiplexing operation by a selector.

FIG. 9 is an example of a control operation sequence based on control communication between a communication terminal and a multipoint connection device.

FIG. 10 is a configuration diagram of a multipoint connection device according to a second embodiment.

FIG. 11 is a system configuration diagram to which Example 3 and Example 4 are applied.

FIG. 12 is a configuration diagram of a multipoint connection device according to a third embodiment.

FIG. 13 is an example of communication operation of image information between each multipoint connection device.

FIG. 14 is an example of a line frame format between multipoint connection devices.

FIG. 15 is a diagram showing an example of interconnection of multipoint connection devices.

FIG. 16 is a configuration diagram of a multipoint connection device according to a fourth embodiment.

FIG. 17 is an example of communication operation of image information between each multipoint connection device.

FIG. 18 is a diagram illustrating an example of interconnection of multipoint connection devices according to the fourth embodiment.

FIG. 19 is a configuration diagram of a first embodiment corresponding to the second principle configuration.

FIG. 20 is a configuration diagram of a second embodiment corresponding to the second principle configuration.

FIG. 21 is a conventional system configuration diagram.

FIG. 22 is a line frame format of image information transmitted from the multipoint connection device to each communication terminal.

FIG. 23 is a configuration diagram of a conventional example of a communication terminal device on the receiving side.

FIG. 24 is a diagram illustrating problems with the image buffer.

[Explanation of symbols]

1 Sending side image communication terminal device 2
Multipoint connection device 3 Receiving side image communication terminal device 10
Multiplexing section 20 Control section 21 Input switch section 22 Transmission unit 23 Buffer 24 Multiplexing section 25 Output switch section 30 Separation section

Claims (8)

[Claims] Claim 1: In a multipoint image communication system in which image communication terminal devices at multiple points are interconnected by a multipoint connection device via a transmission path, the multipoint connection device transmits images transmitted from each image communication terminal device. An input switch unit that inputs information to a designated transmission unit, an output switch unit that outputs multiplexed image signals from multiple points created by the transmission unit to a designated video communication terminal device, and each video communication terminal device. and a control section that performs control communication and controls each part, and the transmission unit stores each image information from the image communication terminal device to be combined in a plurality of buffers, and multiplexes the image information of the plurality of buffers. The transmitting side of the image communication terminal device transmits image information with point information set in the point information storage area provided in the header in blocks, and the receiving side receives each block of received image information. A multipoint image communication method characterized by analyzing headers of images and receiving images from multiple points. 2. In claim 1, the multipoint connection device and the image communication terminal device transmit the control information together with the image information via the transmission path through the control communication path, and the control unit of the multipoint connection device transmits the control information through the control communication path. A multipoint image communication system characterized by transmitting and receiving notifications to an image communication terminal device and requests from the image communication terminal device using a path. 3. In claim 1, the transmission unit controls to analyze the header of the image information input from the input switch section and store it in the corresponding buffer, and to control the image information input from the input switch section to store the image information in the corresponding buffer. A multipoint image communication system characterized by comprising a header detection/switching processing unit that controls selectors that are combined and multiplexed. Claim 4: In a multipoint image communication system in which image communication terminal devices at multiple points are interconnected with a multipoint connection device via a transmission path, the transmitting side of the image communication terminal device transmits encoded image information. The multipoint connection device includes an input switch section that outputs the image information sent from each image communication terminal device to the necessary transmission unit, and a multipoint connection device created by the transmission unit. The transmission unit is equipped with an output switch section that outputs the multiplexed image signal to the required image communication terminal device, and a control section that performs control communication with each image communication terminal device and controls each section. Each piece of image information from multiple image communication terminals to be received is accumulated, and the image information in multiple buffers is multiplexed and output to the output switch section, and the control section controls the input switch through control communication with each image communication terminal device. The multiplexing unit is characterized by managing point information of each image information input from the unit to each buffer of the transmission unit, and controlling a header rewriting unit that writes point information to each of the multiplexed image information of the transmission unit. Point image communication method. 5. According to claims 1 to 4, in order to connect a plurality of multipoint connection devices to each other via a transmission path, the multipoint connection device comprises a receiving section and a transmitting section for the multipoint connection devices; The reception unit includes a header analysis unit and a separation unit, the multipoint connection device reception unit separates control information and image information, and the header analysis unit analyzes the header to detect point information instructed by the control unit. The separation unit separates image information from multiple points and inputs it to the input switch unit, and the transmission unit for the multipoint connection device separates the image information from multiple points and inputs it to the input switch unit. A multipoint image communication method characterized by transmitting images to other multipoint connection devices. 6. In claim 5, a direct connection path is provided between the input switch section and the output switch section without passing through a buffer, and the image information of the receiving section for the multipoint connection device is transmitted to the image stored in the own multipoint connection device. When outputting to a communication terminal device or other multi-point connection device transmitting section, the control section controls the input switch section and the output switch section to transmit the output to the multi-point connection device receiving section via the direct connection path. A multipoint image communication method, characterized in that it is connected to the image communication terminal device or the transmission unit for the multipoint connection device. Claim 7: In a multipoint image communication system in which image communication terminal devices at multiple points are interconnected by a multipoint connection device via a transmission path, the multipoint connection device transmits each image information from the image communication terminal device. The transmitting side of the image communication terminal device is equipped with a multiplexing section that multiplexes the image information of each buffer that accumulates the multiple image information to be combined and outputs it to the output switch section. A multipoint image communication system characterized by transmitting image information whose transmission speed is effectively reduced by inserting a fill frame at a ratio corresponding to a speed ratio setting signal. [Claim 8] In claim 7, the multipoint connection device includes a storage amount monitoring section for each buffer that stores each image information from the image communication terminal device, and the storage amount monitoring section detects the storage amount of the buffer. The multipoint connection device generates an output when the accumulated amount exceeds a predetermined amount, and the multipoint connection device transmits a fill request for the image information in response to the generation of the output from the buffer accumulated amount monitoring section. A multi-point image communication system, characterized in that the image communication terminal device supplies the speed ratio setting signal to the transmitting side upon receiving a fill request.