JPH01147946A - Video conference system inter multi-point - Google Patents

Abstract

PURPOSE:To transmit a picture with high-definition even in case of a limited transmission line capacity by controlling the utilizing efficiency of a multiplex transmission optimizingly in response to the number of stations used for a video conference. CONSTITUTION:The channel number of a multiplex transmission line is set in the bit rate control means 133 of a controller 130 in response to a conference setting request of a terminal equipment and the using state of each channel of a multiplex transmission line 110 read from a managing means 131 and a channel is assigned respectively to each terminal equipment. Moreover, a bit rate corresponding to the channel in response to the channel number is decided and informed to terminal equipments 1201-120n. On the other hand, since transmission line interfaces 1211-1213 of the terminal equipments 1201-1203 are controlled in response to the bit rate information to be extracted, the picture quality in response to the optimum control of the utilizing efficiency of the multiplex transmission line 110 is controlled.

Description

[Detailed Description of the Invention] [Summary] In a multipoint video conference system that connects stations at multiple points and simultaneously conducts a video conference, the use of multiplexed transmission paths is determined according to the number of stations used for the video conference. With the aim of optimally controlling efficiency, the system consists of multiple video conference terminal devices connected via a multiplexed transmission path, a control device that assigns each terminal device to each channel of the multiplexed transmission path, and manages the transmission path. In a multipoint video conferencing system equipped with and bit rate control means for setting the number of channels, determining a bit rate corresponding to the channel, and notifying each terminal device, and each terminal device extracting this bit rate information,
The configuration is such that each transmission line interface is controlled accordingly.

[Industrial Field of Application] The present invention relates to a multipoint video conference system that connects stations at multiple locations and simultaneously conducts a video conference.

In particular, by efficiently using multiplexed transmission lines with limited capacity,
This invention relates to a multipoint video conference system that can improve image quality.

[Conventional technology]

When connecting stations at multiple locations to conduct a video conference at the same time, each station must simultaneously display the images and audio of multiple other stations. Each terminal device frames (field) multiplexes the signals of each station, is equipped with a frame memory for each station, separates the signals of each station from the transmitted frame multiplexed signal, and sends the signals of each station via the frame memory. Control is performed to display each on the monitor.

Here, the bit rate of the multiplexed transmission line connecting each station is usually fixed, and the bit rate assigned to each station is determined according to the number of multiplexed channels.

For example, in the case of a system configuration in which up to four stations simultaneously conduct a video conference, at least four channels are required, and the bit rate of the multiplexed transmission path is 6 Mbit/
Assuming that the bit rate is fixed at s, the bit rate corresponding to each channel is 1.5 Mbit/s, and the transmission line interface of each terminal device is controlled according to the bit rate.

That is, the encoding device (COD) or decoding device (DEC) of each terminal device, and the multiplex conversion device (MUX)
Alternatively, a multiplexer/demultiplexer (DMUX) or the like is set to operate in accordance with the bit rate.

[Problem that the invention seeks to solve]

In such a conventional configuration, since the bit rate of the multiplexed transmission path is fixed, the bit rate corresponding to each channel is fixed according to the maximum number of channels accommodated. Therefore, in a system configuration where a maximum of four stations can simultaneously hold a video conference in front of each other as described above, two channels are used when two stations hold a video conference, and the remaining two channels are left vacant. It has become.

On the other hand, the bit rate of interframe encoding used in conventional video conferencing systems affects the moving area area or image quality (resolution, tracking ability) of the target image, and the encoding method is the same. Now, it is possible to transmit higher quality images by increasing the bit rate of each channel.

The present invention takes these points into consideration and aims to provide a multipoint video conference system that can optimally control the usage efficiency of multiplexed transmission paths depending on the number of stations used for video conferences. do.

[Means for solving problems]

FIG. 1 is a block diagram of the principle of the present invention.

In the figure, a plurality of video conference terminal devices 120 . 3 are configurations in which set bit rate information is extracted and each transmission line interface 1211 to 1213 is controlled accordingly.

The control device 130 sets the number of channels of the multiplexed transmission path according to the management means 131 in which the usage status of each channel of the multiplexed transmission path 110 is stored, the conference setting request of the terminal device, and the usage status of each channel. and a bit rate control means 133 that determines a bit rate corresponding to a channel and notifies each terminal device, and controls the bit rate assigned to each terminal device according to the number of terminal devices in which a conference is held. It is.

[For production]

The present invention provides bit rate control means 13 of control device 130.
3, the terminal device conference setting request and management means 131
The number of channels of the multiplex transmission path is set according to the usage status of each channel of the multiplex transmission path 110 read from the multiplex transmission path 110, and a channel is assigned to each terminal device.

Furthermore, the bit rate corresponding to the channel is determined according to the number of channels, and the bit rate for each terminal device 120. ~3 will be notified.

On the other hand, each terminal device 120. ~3 transmission path interface 121. ~． is controlled in accordance with the extracted bit rate information, so that image quality can be controlled in accordance with optimal control of usage efficiency of the multiplexed transmission path 110.

In other words, the number of channels is limited depending on the usage status of the multiplexed transmission line 110 (the number of stations used for video conferences), and the image quality can be improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a flowchart showing a control example of transmission path management in the multipoint video conference system of the present invention.

In Fig. 2(a), when a conference setting request is input from one station, the control device managing the channels of the multiplexed transmission path refers to the management table in which the usage status of each channel is stored. and determines whether the specified station is currently holding a conference. If this station is not in a conference, the management table is referred to again, the number of channels is set according to the number of stations currently in conference and the number of stations that have requested conference settings, and the multiplex transmission path is divided. . Subsequently, the bit rate corresponding to the channel is determined according to the bit rate of the multiplexed transmission path and assigned to each channel.

For example, if none of the stations are currently holding a conference and stations A and B are going to hold a new three-round video conference, the multiplexed transmission path will be divided into two channels and a 6Mbit
If the multiplex transmission line has a bit rate of /s, 3 Mbit/s is allocated to each channel corresponding to the station. Furthermore, if three other stations (for example, stations 0 and D) are already in a conference, it is necessary to divide the multiplexed transmission path into 4 channels, and 1.5 Mbit/s is allocated to each channel.

Here, a transmission path frame is formed based on the set number of channels and the bit rate corresponding to each channel, and transmission control of the multiplexed transmission path is performed.

Also, the bit rate for each channel that has been set or changed (3Mbit/s, 1.5Mbit/s)
is added to the transmission path frame as transmission path information,
The terminal device of each station is notified. Also, at this point, the management table is updated.

On the other hand, in each terminal device, the transmission path interface is controlled according to the notified bit rate. Note that in the stations whose bit rates have been changed (station 0 and station D), the transmission line interfaces are reset in accordance with the change in bit rate.

FIG. 2(b) shows part of a control example of transmission path management when another station joins a conference currently in progress.

For example, if three stations (stations A and B) are in a video conference, and the third station 0 requests station A or station B to set up a conference, the management table will usually show that the conference is already in progress. Therefore, the user cannot participate in the conference due to the busy process (FIG. 2(a)).

However, as shown in Figure 2), if station A, B, or station 0 performs mid-participation settings for station 0 according to a predetermined procedure, the management table is similarly referred to, and the specified station is currently in the conference. Even if the station is in the middle, it is determined whether or not station 0 is a station that joins in the middle. That is, if a predetermined procedure is followed, it is possible for 0 stations to participate midway. Hereinafter, returning to the control flow after "■" shown in FIG. 2(a), the number of channels of the multiplex transmission path is set according to the number of stations currently in a conference and the station that has requested conference settings. The bit rate corresponding to the channel is calculated.

In this case, the video conference will be held in three rounds, including the zero station, so the multiplexed transmission path will be divided into three channels, and the bit rate for each channel will be changed from 3 Mbit/s to 2 Mbit/s. Ru.

FIG. 3 is a diagram showing an example of the structure of a transmission line frame.

FIG. 3(a) shows a state in which the multiplexed transmission path is divided into two channels, and information from stations A and B is multiplexed in each channel.

In Figure 3), the multiplexed transmission line is divided into 3 channels,
This shows a state in which information of stations A, B, and 0 are multiplexed, respectively.

In the figure, transmission path information including bit rate information corresponding to each channel is added to the beginning of the frame, and station information (identification information C1 audio information A
, low-speed data D, and image information V) are set.

Note that if the bit rate of the multiplexed transmission path is 6 Mbit/s, then in the case of 2 channels, each channel has 3 Mbit/s.
/s is allocated, and in case of 3 channels, 2Mbit
/s is assigned.

FIG. 4 is a block diagram showing an example of the configuration of a transmission line interface of a video conference terminal device.

Here, there are five stations (A, B, C) on the multiplexed transmission path.

D, E) are accommodated, and the configuration of one of them, A, is shown.
The image signal decoding means is configured to be provided for each station.

In the figure, the transmitter 410 includes a buffer memory (BM) 411 that adjusts the bit rate of the encoded image signal.
A multiplex conversion circuit (MUXI) 413 multiplexes the image signal, audio signal, and low-speed data signal output from this buffer memory 411, and a synchronization control circuit for frame multiplexing this multiplexed signal with other station signals. It is composed of a frame multiplex conversion circuit (MUXz) 415, which performs frame multiplex conversion, and a transmission line interface circuit (LIF) 417, which performs interface control with the transmission line.

The receiving unit 420 includes a similar transmission line interface circuit (L
IF) 421 and a bit rate information extraction circuit (DMUX6) that obtains the bit rate assigned to each channel.
423, and a frame multiplexing and demultiplexing circuit (DMUXz) 42 that separates each station (B station to E station) signal from the transmission path frame.
5, and a multiplexing/demultiplexing circuit (D
It is composed of MUX I<1)-(E)) 4271+4 and buffer memories (BM(l>~□>) 429t~4.

Each circuit is supplied with the bit rate extracted by the bit rate information extraction circuit 423, and is configured to operate in accordance with the bit rate corresponding to the number of channels of this multiplexed transmission path.

In such a configuration, when none of the stations accommodated in the multiplexed transmission line is conducting a video conference,
The operation when a station and a station B hold a one-on-one video conference will be explained.

In the transmission path frame, 3 Mbit/s is allocated to each channel as shown in FIG. 3(a), and this bit rate is set as transmission path information.

The bit rate information extraction circuit 423 of each terminal device separates this bit rate information and supplies it to each circuit. The frame multiplexing/demultiplexing circuit 425 of the A station extracts the signal of only the B station from the frame multiplexed signals of the A station and B station according to this bit rate, and sends the signal of only the B station to the multiplexing/demultiplexing circuit (DMUXI).
(Ill) Send to 4271. Demultiplexing circuit 427
1, audio information A, low-speed data D, and image information V are similarly separated from the signal corresponding to station B, and image information V is sent to the corresponding buffer memory (B M (1)) 429 I.

In addition, when a video conference is held in three rounds with stations A, B, and 0, eight 2Mbits are allocated to each channel in the transmission path frame as shown in Figure 3 (b), and the transmission path information is This bit rate is set.

At this time, the frame demultiplexing circuit 425 of the A station separates the signals of the B station and the 0 station, and the corresponding demultiplexing circuits (DMUX1(81,+e>) 42L, 4
27g, and are further separated into audio information A, low-speed data D, and image information V, and image information ■ is sent to the corresponding buffer memory (BM (11, (C1) 429).
+ and 429g, respectively.

In the transmitter 410, the buffer memory 411 is controlled according to this bit rate, and the encoded image information V is limited, and the multiplex conversion circuit 413 multiplexes the audio information A, the low-speed data D, and the image information (2). become This multiplexed signal is frame-synchronized, multiplexed at a predetermined position in a frame as shown in FIG. 3, and sent to the multiplexed transmission line via the transmission line interface circuit 419.

〔Effect of the invention〕

As described above, according to the present invention, the usage efficiency of the multiplexed transmission path is optimally controlled according to the number of stations conducting a video conference, so even with limited transmission path capacity, high-quality images can be obtained. It becomes possible to transmit.

In particular, since the allocated bit rate is changed depending on the number of stations, if the number of stations is small, the quality of the image can be improved accordingly, which is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a principle block diagram of the present invention, FIG. 2 is a flowchart showing an example of controlling transmission path management in the multipoint video conference system of the invention, and FIG. 3 is a diagram showing an example of the configuration of a transmission path frame. FIG. 4 is a block diagram showing an example of the configuration of a transmission path interface of a video conference terminal device. In the figure, 110 is a multiplex transmission line, 1201 to . are video conference terminal devices, 1211-. 130 is a transmission line interface, 130 is a control device, 131 is a management means, 133 is a cut rate control means, 410 is a transmitter, 411 is a buffer memory (BM), 413 is a multiplex conversion circuit (MUXI) 513, 415 is a frame multiplex conversion circuit (MUXz), 417 is a transmission line interface circuit (LIF), 420 is a receiving section, 421 is a transmission line interface circuit (LIF), 4
23 is a bit rate information extraction circuit (DMUX3) 425
is frame demultiplexing circuit (DMUXz), 427I~4
is a demultiplexing circuit (DMUXI (I11 to (E)), 42
9 I-a is the buffer memory (B M (ml-(El
). Oki 4 To Moe Nakabu Pro... 12th 1st Figure LYF + Management Anatomy Opening (a3) (Nasty) L-Lm "14 Tet \ Sai row 3rd Figure

Claims (1)

[Claims] A plurality of video conference terminal devices (120_1_ to _3) connected via a multiplex transmission path (110), each terminal device assigned to each channel of the multiplex transmission path, and transmission path management In the multipoint video conference system, the control device (130) includes a management means (13) that stores the usage status of each channel.
1), setting the number of channels of the multiplexed transmission path according to the conference setting request of the terminal device and the usage status of each channel;
and a bit rate control means (133) that determines a bit rate corresponding to a channel and notifies each terminal device, and each terminal device (120_1_-_3) extracts this bit rate information and controls each transmission accordingly. 1. A multipoint video conference system characterized in that the road interfaces (121_1_-_3) are controlled.