JP6534968B2 - Multipoint connection device, video distribution system, multipoint connection method, and program - Google Patents

Description

  The present disclosure relates to a multipoint communication apparatus, video distribution system, multipoint connection method, and program for video communication for exchanging video and audio with a remote place via a network.

  In a video conference where video and audio are exchanged with multiple remote locations via a network, the network load and video / audio decoding processing load required on the receiving side when transmitting and receiving video and audio directly between all locations are the number of locations. It is difficult to deal with a large number of bases because Therefore, in a video conference connecting many points, it is general to use a multipoint connection device in order to reduce the network load and decoding processing load on the receiving side. The multipoint connection device receives video and audio from multiple locations, combines multiple videos into one video, and distributes it to the receiving terminal, so that the network load and decoding processing load on the receiving side is one video It can be reduced to a minute.

  Patent Document 1 describes a technique for measuring physical quantities such as audio levels from video and audio at each site in a multipoint connection device, and dynamically changing the display mode of video based on the measured physical quantities. As a practical example thereof, a method is disclosed in which a speaking base is specified from the volume level, and the video of the speaking base is displayed larger than the video of the other bases. Further, Patent Document 2 describes a technique for largely allocating a limited network resource to a message base. As an embodiment, a method is described in which the video of the utterance base is made higher definition by dynamically changing the number of quantization steps in the video encoding of the utterance base and the configuration of the picture group.

JP-A-5-103324 JP 2005-341347

  In the methods of Patent Documents 1 and 2, it is premised that the multipoint connection device receives video and audio from all the bases. Therefore, the network load and the decoding processing load in the multipoint connection device increase according to the number of connected points. Although the network load and decoding processing load at the receiving terminals at each site can be reduced by using the multipoint connection apparatus, the network point corresponding to the number of connection sites and the computational resources for decoding processing (CPU and decryption for the multipoint connection apparatus Circuit) is required.

  In addition, when transmitting a plurality of camera images from one site, it is necessary to have an available network bandwidth corresponding to the number of camera images between the site and the multipoint connection device. Although it is possible to reduce the network load by stopping the transmission of video not used in composite video, it is difficult to cope with sudden video switching since it takes time to resume transmission once the coding device is stopped. .

  From the viewpoints of responsiveness and network traffic, it is desirable that the encoding apparatus performs control to transmit an IP packet only when it is used in composite video, while always performing encoding processing. However, in order to perform such control, it is necessary for the coding device to control IP packet transmission based on the information notified from the multipoint connection device. Therefore, a coding device equipped with such a function in advance is required.

  That is, in the conventional multipoint connection device, the improvement of the responsiveness of the image switching and the reduction of the network load have been problems. Therefore, the present invention has an object to provide a multipoint connection device, a video distribution system, a multipoint connection method, and a program, which can improve the responsiveness of video switching and reduce the network load, in order to solve the above problems. Do.

  In order to achieve the above object, the multipoint connection device according to the present invention decides to stop video streams not being used at any receiving terminal on the network.

Specifically, the multipoint connection apparatus according to the present invention is
A receiver for receiving a plurality of video streams from a network having a network device for controlling transmission of traffic;
A distribution unit for distributing, for each receiving terminal, a composite video stream obtained by combining any one of the video stream or any of a plurality of the video streams among the video streams received by the receiving unit;
Stopping the transmission of the video stream that has not been distributed to any of the receiving terminals and has not been synthesized to any of the composite video streams to the network device, and the video stream whose transmission has been stopped A network control unit instructing resumption of transmission;
Equipped with

Further, the video delivery system according to the present invention is
A video transmission device for transmitting a plurality of video streams to a network having a network device controlling transmission of traffic;
A receiving unit for receiving a plurality of the video streams from the network;
A distribution unit for distributing, for each receiving terminal, a composite video stream obtained by combining any one of the video stream or any of a plurality of the video streams among the video streams received by the receiving unit;
Stopping the transmission of the video stream that has not been distributed to any of the receiving terminals and has not been synthesized to any of the composite video streams to the network device, and the video stream whose transmission has been stopped A network control unit instructing resumption of transmission;
Equipped with

Also, the multipoint connection method according to the present invention is
A video transmission procedure for transmitting a plurality of video streams to a network having a network device controlling transmission of traffic;
A reception procedure for receiving a plurality of the video streams from the network;
A delivery procedure for delivering, for each receiving terminal, a composite video stream obtained by combining any of the video stream or any of a plurality of the video streams among the video streams received in the reception procedure;
Stopping the transmission of the video stream that has not been distributed to any of the receiving terminals and has not been synthesized to any of the composite video streams to the network device, and the video stream whose transmission has been stopped A network control procedure that instructs to resume transmission;
I do.

  The present invention does not rely on a transmitting apparatus (encoding apparatus) for transmitting a video stream, and stops transfer at a network apparatus on the network. By operating the encoding device all the time, the responsiveness of video switching can be improved. In addition, the network load can be reduced by stopping the transfer of unnecessary video streams in the network device. Therefore, the present invention can provide a multipoint connection device, a video distribution system, and a multipoint connection method capable of improving the responsiveness of video switching and reducing the network load.

This multipoint connection device is
It has a table in which a video identification number for identifying the video stream and a combining unit identification number for identifying a video combining unit included in the distribution unit are described based on the order corresponding to each layout frame displayed by the receiving terminal. Database department,
A connection management unit that acquires the video identification number from the transmission source of the video stream and exclusively describes the video identification number for each rank in the table of the database unit;
And further
The distribution unit describes the combining unit identification number in the order displayed by the receiving terminal in the table of the database unit based on the information of the layout frame.
The network control unit may determine the video stream to stop transmission and the video stream to resume transmission from the description of the table of the database unit.

  The database unit of the present multipoint connection apparatus is notified of the order of the video stream from the order determining apparatus which adds the order to the video stream, and to the order notified of the video identification number described in the table. It is characterized by moving. By giving priority to each video stream, the receiving terminal can perform display according to the priority.

For example, the multipoint connection apparatus is characterized in that the order is determined based on the volume of the transmission source of the video stream.
Also, by using information other than the physical quantity extracted from the video and audio transmitted to the multipoint connection device as a reference for determining the display mode of the video, for example, by using metadata such as infrared sensor information It can be expected that the display suitable for the preference of

For example, in the multipoint connection apparatus according to the present invention, the video stream with the highest volume of the transmission source of the video stream is ranked first, and the transition probability from the first video stream to another video stream is determined. It is characterized in that the second place or less is determined based on that.
By referring to the history of speaker changes in the past, it may be possible to predict speaker changes that will occur in the future, and to determine the order.

  The present invention is a program for causing a computer to function as the multipoint connection device. The multipoint connection apparatus according to the present invention can be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

  The present invention can provide a multipoint connection device, a video distribution system, a multipoint connection method, and a program capable of improving the responsiveness of video switching and reducing the network load.

It is a figure explaining the example of composition of the picture distribution system concerning the present invention. It is a figure explaining the video layout which the receiving terminal of the video delivery system concerning this invention displays. The numbers in the layout box are "order". It is a figure explaining the table of the database part with which the multipoint connection apparatus based on this invention is equipped. For example, the identification numbers A, B, C, and D of the video combining unit correspond to the video combining units 41-1, 41-2, 41-3, and 41-4, respectively. It is a flow chart explaining operation of a multipoint connection device concerning the present invention. It is a sequence diagram explaining operation | movement of the video delivery system concerning this invention. It is a figure explaining the transition probability table which the order determination apparatus of the imaging | video delivery system which concerns on this invention manages.

  Embodiments of the invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, components having the same reference numerals denote the same components.

FIG. 1 is a configuration diagram for explaining a video delivery system 301 according to the present embodiment. The video delivery system 301
A video transmission device 10 for transmitting a plurality of video streams to a network 20 having a network device 25 controlling transmission of traffic;
A receiver 30 for receiving a plurality of the video streams from the network 20;
A distribution unit 40 for distributing, for each of the reception terminals 51, a composite video stream obtained by combining an arbitrary video stream or an arbitrary plurality of video streams among the video streams received by the reception unit 30;
Stop of transmission of the video stream which has not been distributed to any of the receiving terminals 51 and not synthesized into any of the composite video stream with respect to the network device 25; A network control unit 61 instructing resumption of transmission;
Equipped with

  The video transmission device 10 encodes a camera (11-1 to 11-n; n is a natural number) and a video encoding device (12-) that encodes a video signal output from each camera 11 and outputs it as an IP packet (video stream). 1 to 12-n) and metadata generation devices (13-1 to 13-n) for acquiring information on the periphery of each camera 11 and outputting the information as metadata. The cameras 11 may be at the same site or at different sites.

  The receiving unit 30 has a video decoding unit (32-1 to 32-n) that receives a video stream for each video identification number (destination port number) and decodes the received video stream. The destination port number is, for example, a UDP (User Datagram Protocol) port number. The distributing unit 40 re-encodes the synthesized video and a video synthesizing unit (41-1 to 41-m; m is a natural number) that synthesizes the video decoded so as to be the screen layout specified by the receiving side. And a video encoding unit (42-1 to 42-m). There are a plurality of receiving terminals 51, and a layout frame setting device 52 is provided to which the user can optionally set the layout of the video to be displayed on the screen. The receiving terminal 51 and the layout frame setting device 52 are not necessarily in one-to-one correspondence. It is also possible that a plurality of receiving terminals receive the same video for one layout.

The multipoint connection device 100
A receiver 30 for receiving a plurality of video streams from a network 20 having a network device 25 controlling transmission of traffic;
A distribution unit 40 for distributing, for each of the reception terminals 51, a composite video stream obtained by combining an arbitrary video stream or an arbitrary plurality of video streams among the video streams received by the reception unit 30;
Stop of transmission of the video stream which has not been distributed to any of the receiving terminals 51 and not synthesized into any of the composite video stream with respect to the network device 25; A network control unit 61 instructing resumption of transmission;
Equipped with

The multipoint connection device 100
A video identification number (for example, a destination port number) for identifying the video stream and a combining unit identification for identifying the video combining unit 41 included in the distribution unit 40 based on the order corresponding to each layout frame displayed by the receiving terminal 51 A database unit 62 having a table in which numbers are described;
A connection management unit 63 which acquires the video identification number from the transmission source of the video stream, and exclusively describes the video identification number for each rank of the table of the database unit 62;
Further comprising
Then, based on the information on the layout frame set by the layout frame setting device 52, the distribution unit 40 describes the combining unit identification number in the order displayed by the receiving terminal 51 in the table of the database unit 62. The network control unit 61 determines the video stream to stop transmission and the video stream to resume transmission from the description in the table of the database unit 62.

  The multipoint connection device 100 includes a connection management unit 63, a video decoding unit 32, a video combining unit 41, a video coding unit 42, a database unit 62, and a network control unit 61. These functions may be implemented separately on separate processes or hardware.

  The multipoint connection apparatus 100 receives the video stream encoded from the video encoding apparatus 12 at each site, identifies the stream from the information such as the destination port number, and distributes the IP packet to each video decoding unit 32. The connection management unit 63 of the multipoint connection apparatus 100 and the video encoding apparatus 12 exchange information for identifying the above-mentioned video stream at the time of connection. In addition, if this identification information is previously decided, exchange is unnecessary. In the following, the case of using a destination port number for identification of a video stream will be described. H. to establish a connection. Standardized protocols such as H.323 may be used.

  The layout frame setting device 52 transmits layout frame setting information to the video synthesizing unit 41 of the multipoint connection device 100. FIG. 2 shows an example of setting a layout frame. FIG. 2 (a) is an example of a layout frame of uniform size, and FIGS. 2 (b) and 2 (c) are examples of a layout frame on which a specific base is enlarged and displayed. The numbers in each layout frame are uniquely assigned orders. The layout frame holds the position information and the order of arranging the video in the screen. Furthermore, a parameter for specifying a display method such as transparency may be additionally held. The layout frame may comprise a time-varying animation representation. In the layout frame setting information, the video to be displayed in each layout frame is not designated. The image displayed in each layout frame is determined by determining the order of the images based on a specific criterion by the order determining device described later.

  The database unit 62 holds a table composed of destination port numbers and ranks, and composite identification numbers of video combining units using them. FIG. 3 shows an example of a relational database table. In the table of FIG. 3, "order" is the order assigned to the layout frame. The “destination port number” is a UDP port number that identifies the video decoding unit 32 of the multipoint connection device 100, and is also a number that identifies the input video stream. For example, the video (5001) of the rank 1 is used by three terminals of the receiving terminal 51-1, the receiving terminal 51-2, and the receiving terminal 51-3, and the video (5003) of the rank 3 is used only by the receiving terminal 51-1. used. On the other hand, the video (5004) of the order 4 is not used in any video terminal. In FIG. 1, the video synthesizing unit and the receiving terminal have a 1: 1 relationship, but a synthesized video may be distributed from one video synthesizing unit to a plurality of receiving terminals.

  A flowchart at the time of table update is shown in FIG. The timing at which the table is updated will be described later. When the database unit 62 updates the table (step S01), the database unit 62 notifies the video decoding unit 32 of the identification number of the video synthesis unit 41 to which the decoded video should be passed (step S02). Further, the network control unit 61 monitors the database unit 62, and when an unused video stream is generated ("Yes" in step S05), a command is sent to the network device 25 transmitting the video stream. Then, the transfer of the video stream is stopped (step S06). The command to the network device may be a command specific to the network device or a command based on a protocol such as OpenFlow. Further, when there is a management program that integrates and manages a plurality of network devices, a command for the management program may be issued to realize the desired operation to the management program.

  The video delivery system 301 reduces unnecessary traffic by stopping a video stream not used by any receiving terminal on the network as described above. For example, in FIG. 3, since the video stream addressed to the 5004 port is not used in any composite video output from the video combining unit 41, the network control unit 61 transmits the video addressed to the 5004 port to the network device 25. Stop the stream transfer. On the other hand, when the video stream which has been stopped up to that point is newly used as a composite video (“Yes” in step S03), the network control unit 61 issues a command to the network device 25. The transfer of the video stream is started (step S04).

  Since the video stream is distinguished by the destination port number, it is possible to control transfer stop or start by the network device 25 and does not depend on the function of the video encoding device 12. The network device 25 to be controlled may be any network device in the network path from the video transmission device 10 to the multipoint connection device 100.

  The video decoding unit 32 decodes the video from the received coded video stream, and passes the decoded video to the video combining unit 41 notified from the database unit 62. The video synthesis unit 41 receives the decoded video from the one or more video decoding units 32, synthesizes the video according to the layout frame setting notified from the layout frame setting device 52, and transmits the synthesized video to the video coding unit 42. hand over. At this time, the voice is also synthesized and passed to the video encoding unit. The video encoding unit 42 encodes the composite video delivered from the video combining unit 41 and transmits an IP packet to the receiving terminal 51.

  As shown in FIG. 1, one multipoint connection device may include a plurality of video combining units and generate a plurality of combined videos. Also, one multipoint connection device may be equipped with one video combining unit and transmit a single combined video to a plurality of receiving terminals.

  For example, the time when the video synthesis unit 41 receives layout frame information from the layout frame setting device 52 can be set as table update time. When receiving the layout frame information from the layout frame setting device 52, the video combining unit 41 confirms whether the layout is possible. If the layout can not be realized because the number of videos to be used exceeds the number of decodable videos, an error is returned to the layout frame setting device 52. When it is confirmed that the layout is possible, the layout setting of its own is updated, and at the same time, the table of the database unit 62 is updated.

For example, the time when the order of the video stream changes can be set as the table update time.
The database unit 62 is notified of the order of the video stream from the order determining device 14 which assigns the order to the video stream, and moves the video identification number described in the table to the notified order.
The order determination device 14 receives not only video and audio but also metadata from the metadata generation device 13 such as various sensors, and ranks the video stream according to a specific criterion. For example, “order” is an order such that the last utterance is first and the preceding utterance is second, and the order in which the magnitude of the movement of the person to be photographed detected by the infrared sensor is large. The order determination device 14 updates the table of the database unit 62 when changing the order of the video stream. In the table as shown in FIG. 3, the destination port numbers in the second column may be exchanged. For example, when the order of the video stream of the destination port number 5003 changes from the third place to the first place and the order of the video stream of the destination port number 5001 changes from the first place to the third place, the order determining device 14 The part 62 is notified, and the database part 62 replaces the current first destination port number with the current third destination port number.

The sequence up to the start of video composition is shown in FIG.
At the same time as the connection management unit 63 notifies the video encoding apparatus 12 of the destination port number, an entry of the destination port number is created in the table of the database unit 62. In the initial stage, since the relationship between the “destination port number” and the “order” is unknown, any “order” may be set so as not to overlap each entry created. The setting of the "order" will be described later.

  Each video synthesizing unit 41 describes its own identification number in the entry of “order” to be used among the entries created in the table of the database unit 62 based on the notified layout frame setting (“order” to be used). Do.

  The database unit 62 notifies the video decoding unit 32 of the identification number of the video synthesis unit 41 which passes the decoded video. When the video encoding device 12 starts video streaming, the video stream sent from the video encoding device 12 is decoded by the video decoding unit 32, and the video is delivered to the video synthesizing unit 41 where the video is used according to the setting of the table. .

  In the initial stage, since the relationship between the "destination port number" and the "order" in the table is arbitrary, the receiving terminal displays an arbitrary video stream in each rank of the layout. After predetermined, the destination port number string of the table is updated according to the order determined by the order determining device 14 and the manual order setting of the user, and the image is delivered to the image combining unit 41 according to the updated table setting.

As described above, the video delivery system 301
A video transmission procedure for transmitting a plurality of video streams to a network 20 having a network device 25 controlling transmission of traffic;
A reception procedure for receiving a plurality of the video streams from the network 20;
A distribution procedure for distributing, for each of the reception terminals 51, a composite video stream obtained by combining any of the video stream or any of a plurality of the video streams among the video streams received in the reception procedure;
Stop of transmission of the video stream which has not been distributed to any of the receiving terminals 51 and not synthesized into any of the composite video stream with respect to the network device 25; A network control procedure that instructs to resume transmission;
I do.

Example 1
In the present embodiment, an example of the video distribution system 301 that determines a layout based on the order of utterances will be described. The order is determined based on the volume of the transmission source of the video stream.

A volume measuring device is installed at each site, and the volume of each site is transmitted to the order determining device. The sound to be transmitted to a remote location may be branched and used for volume measurement. Alternatively, a microphone dedicated to volume measurement may be used. The order determining device determines which site is currently in the speech state by comparing the volumes of all sites. The current speaker is ranked first, and the speaker before that is ranked second, and lowers as the last speech becomes older. For example, when using the layout of FIG. 2B, the first place base is arranged in the largest area in the speech state, and the second, third and fourth places are displayed smaller at the lower part of the screen thereafter. The fifth and subsequent positions are not used for composite video. By this, it is possible to visually grasp the base where the latest speech was made.
By using the video delivery system 301 of this embodiment, the user can grasp the speech situation of each site from the composite video.

(Example 2)
In this embodiment, an example of the video distribution system 301 for determining the layout based on the next speaker estimation will be described. The video stream with the highest volume at the transmission source of the video stream is ranked first, and the second or lower rank is determined based on the transition probability from the first video stream to another video stream. It is.

  In Patent Document 1, the video layout is determined by the current speaker. However, depending on the time required to detect an utterance, there may be a situation where the video is not switched even after the speaker is switched. In order to prevent such a situation, by predicting the next speaker and arranging in advance on the composite video, it can be expected that the flow of conversation can be easily grasped even if the video switching is delayed.

  The order of the speaker change is recorded in advance from the record of the past conversation, and the transition probability from the current speaker to the next speaker as shown in FIG. 6 is calculated. The volume is calculated at each location and the result is sent to the ranking device. The order determination device compares the volume of each site, and the point with the largest volume is taken as the current speaker. The current speaker is ranked first, and the second and subsequent ranks are determined in descending order of the transition probability from the current speaker. For example, when using the transition probability of FIG. 6, when the current speaker is the camera 11-1, the destination port number 5001 is the first place, the camera 11-2 is the second place, the camera 11-3 is the third place, the camera 11 -4 is the fourth place. When using the layout of FIG. 2C, the video of the camera 11-1 is displayed in a large area, and the video of the camera 11-2 is displayed in a small area.

  As a method of predicting the next speaker, estimation from a gaze direction using a gaze sensor or estimation from a breathing rhythm using a respiration sensor or the like may be used.

(Effect of the invention)
By controlling the network device in the video transmission path so as to transfer only the video used for the composite video to the multipoint connection device, the effect of reducing the network traffic can be expected. Since it is not necessary to change the state of the video encoding device when changing the state of transfer start or stop of the video stream, the response to the video switching is faster than when the state of the video encoding device is controlled. is there. Also, since the control target is only the network device, the video encoding device does not have to support such a control function.

  In order to decode only the necessary video stream, if the number of bases (the number of cameras and the number of video streams) used for the composite video is constant, the amount of decoding processing in the video combining device increases even if the total number of bases increases. do not do. This makes it possible to handle a large number of bases.

  Aside from physical quantities extracted from video conference video and audio, they can also be used as a basis for determining the layout. You may use the reference | standard which ranks an image | video from various metadata, such as sensor information. It can be expected that this feature makes it possible to configure a composite video according to the preference of the receiver.

10: Video transmission devices 11, 11-1, 11-2, ...: Cameras 12, 12-1, 12-2, ...: Video coding devices 13, 13-1, 13-2, ... · · · Metadata generation device 14: Rank determination device 20: Network 25, 25-1, 25-2, ...: Network device 30: Receiver 31, 31-1, 31-2, ...: Destination port 32, 32-1, 32-2, ...: Video decoding unit 40: Distribution units 41, 41-1, 41-2, ...: Video combining unit 42, 42-1, 42-2, ... · ·: Video coding unit 51, 51-1, 51-2, ...: Reception terminals 52, 52-1, 52-2, ...: Layout frame setting device 61: Network control unit 62: Database unit 63 : Connection management unit 100: Multipoint connection device 301: Video distribution system

Claims (8)

A receiving unit that receives, via a network device that controls transmission of traffic on the network, a plurality of video streams that the video transmission device constantly transmits ;
A distribution unit for distributing, for each receiving terminal, a composite video stream obtained by combining any one of the video stream or any of a plurality of the video streams among the video streams received by the receiving unit;
Stopping the transmission of the video stream that has not been distributed to any of the receiving terminals and has not been synthesized to any of the composite video streams to the network device, and the video stream whose transmission has been stopped A network control unit instructing resumption of transmission;
A multipoint connection device comprising: It has a table in which a video identification number for identifying the video stream and a combining unit identification number for identifying a video combining unit included in the distribution unit are described based on the order corresponding to each layout frame displayed by the receiving terminal. Database department,
A connection management unit that acquires the video identification number from the transmission source of the video stream and exclusively describes the video identification number for each rank in the table of the database unit;
And further
The distribution unit describes the combining unit identification number in the order displayed by the receiving terminal in the table of the database unit based on the information of the layout frame.
2. The multipoint connection apparatus according to claim 1, wherein the network control unit determines the video stream to stop transmission and the video stream to resume transmission from the description of the table of the database unit.   The database unit is notified of the rank of the video stream from a rank determination device that ranks the video stream, and moves the video identification number described in the table to the notified rank. The multipoint connection device according to claim 2.   The multipoint connection device according to claim 3, wherein the order is determined based on a volume of a transmission source of the video stream. The order is
It is assumed that the video stream with the largest volume of the transmission source of the video stream is regarded as the first place, and the second place or less is determined based on the transition probability from the first video stream to the other video stream. A multipoint connection device according to claim 3, characterized in that: Comprising a video transmitting apparatus for transmitting continuously a plurality of video streams to the network equipment that controls the transmission of traffic on the network, and a multipoint control unit,
The multipoint connection device
A receiving unit that receives a plurality of the video streams from the network via the network device ;
A distribution unit for distributing, for each receiving terminal, a composite video stream obtained by combining any one of the video stream or any of a plurality of the video streams among the video streams received by the receiving unit;
Stopping the transmission of the video stream that has not been distributed to any of the receiving terminals and has not been synthesized to any of the composite video streams to the network device, and the video stream whose transmission has been stopped A network control unit instructing resumption of transmission;
A video delivery system comprising: Video transmission apparatus performs image transmission step of transmitting a plurality of video streams to the network equipment that controls the transmission of traffic on the network at all times,
The multipoint connection device
A reception procedure for receiving a plurality of the video streams from the network via the network device ;
A delivery procedure for delivering, for each receiving terminal, a composite video stream obtained by combining any of the video stream or any of a plurality of the video streams among the video streams received in the reception procedure;
Stopping the transmission of the video stream that has not been distributed to any of the receiving terminals and has not been synthesized to any of the composite video streams to the network device, and the video stream whose transmission has been stopped A network control procedure that instructs to resume transmission;
A multipoint connection method characterized by performing.
  A program for causing a computer to function as the multipoint connection device according to any one of claims 1 to 5.

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