JP3316708B2 - Multipoint video conference controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video conference control apparatus for generally controlling video conference terminals arranged at multiple points, and more particularly to a video signal exchange processing technique.

[0002]

2. Description of the Related Art As is well known, in a multipoint video conference system, a plurality of video conference terminals are connected to a control device via a communication path, and an attendant in each conference room is connected to a television by an exchange function of the control device. This allows the user to have a conversation while looking at the screen, thereby achieving the same effect as holding a meeting in the same meeting room.

[0003] The control device, particularly the image signal exchange unit, which controls the center of such a system, appropriately switches an image suitable for the progress of the conference, such as an image of the speaker or an image selected by the chairman's office, and switches to another television. It plays the role of transmitting to the conference terminal.

An information signal created by a video conference terminal is a multimedia signal obtained by multiplexing an image, a sound, and data. In particular, an image is a predetermined signal to which all bits not assigned to the sound or data are allocated. It is video encoded data in a format.

[0005] For this reason, the image signal exchanging section requires an image (video coded data) to change the transmission source of the image.
However, in this case, if the switching is simply performed, the continuity of the video encoded data that has been decoded up to that point is lost, and a decoding error occurs.

A mode change function for changing the transmission speed of voice or data during a conference is added.
As described above, since the multimedia signal is a multiplex of audio and data along with the image, simply changing the transmission speed of the audio or data will also change the transmission speed of the encoded video data, which also causes decoding errors. Resulting in.

[0007] At the time of such image switching and mode change, image disturbance due to decoding error is prevented from occurring, and switching from a previously selected image to a new image is performed as quickly as possible. is necessary.

Therefore, in the conventional multipoint video conference control device, when switching the image or changing the mode, the reception screen of the video conference terminal is frozen in advance, and after the image switching or the mode change is completed, the error correction frame is changed. A method is adopted in which a protection period required for synchronization recovery is set, video encoded data of the video conference terminal of the transmission source is initialized / updated within the protection period, and then the freeze of the reception screen is released.

Here, in the conventional control device, a time corresponding to the synchronization recovery protection period is set in a timer in advance, and the timer is activated by a trigger generated upon completion of image switching or mode change, thereby protecting the protection period. Measurement. When the mode change of the video conference terminal is completed,
Confirmed by receiving commands from the terminal.

FIG. 4 shows an example of an image signal exchange section of a conventional multipoint video conference control device.

In FIG. 4, reference numeral 1 denotes an image signal exchange unit (MP
U), 21 to 2N are video conference terminals. The image signal exchange unit 1 is a line interface unit (hereinafter referred to as L) that inputs and outputs line signals (multimedia signals obtained by multiplexing images, audio, and data (including commands)) in frame units.
MUX / DM for multiplexing / demultiplexing command and video encoded data with respect to line signals 91 to 9N
UXs 81 to 8N, a video data exchange unit 7, and a system control unit 10. System control unit is MIX / DM
Commands can be transmitted and received between the video conference terminals 21 to 2N via the UX.

In the above configuration, conventional image exchange control processing and mode change control processing will be described with reference to FIGS.

FIG. 5 is a sequence diagram showing an example of image exchange, and shows a state of image exchange control when the source of an image received by the video conference terminal TA is switched from the video conference terminal TB to the video conference terminal TC. ing. That is, the image exchange control in this case is performed according to the following procedure.

(1) A screen freeze (VCF) command is transmitted to freeze the screen being received by the video conference terminal TA. (2) The image received by the video conference terminal TA is switched from the video conference terminal TB to the video conference terminal TC. (3)
After waiting for a protection time (T) for restoring the synchronization of the error correction frame, a screen update request (VCU) command is issued to the video conference terminal TC. (4) Initialization from TV conference terminal TC /
The updated video data and the frozen screen release command are sent out, and the video conference terminal TA receives this and releases the frozen screen.

FIG. 6 is a sequence diagram showing an example of a mode change, in which a data channel is opened in response to a request from the video conference terminal TB and the video conference terminals TA and TC receive data transmitted from the video conference terminal TB. 3 shows the mode change control. That is, the mode change control in this case is performed according to the following procedure.

(1) A token request command (DCA-L, <B>) is received from the video conference terminal TB. (2) Set the data to be distributed to ALL “1” (idle bit).
(3) A screen freeze (VCF) command and a video-off command are transmitted to freeze the screens received by the video conference terminals TA, TB, and TC, and stop the transmission of the encoded video data. (4) The MCS and the LSD <B> command instruct the video conference terminals TA, TB and TC to open the data channel at the transmission rate <B> requested by the video conference terminal TB. (5) TV conference terminal TA,
It is confirmed by the LSD <B> command from TB and TC that the data transmission speed has been matched. (6) Transmission of video encoded data is restarted by the video-on command.

(7) Waiting for a protection time (T) for restoring the synchronization of the error correction frame, and requesting a screen update request (VC
U) Issue a command. As a result, the video coded data initialized / updated is transmitted from the source of the image, and the video conference terminals TA, TB, TC receive this and release the freeze of the screen. (8) A setting is made to distribute the data transmitted from the video conference terminal TB to the video conference terminals TA and TC. (9) The video conference terminal T is transmitted by the DIT-L command.
Notify B that you have given the token. (10) Receive the data format command from the video conference terminal TB and distribute it. (11) The video conference terminal TB starts data transmission.

The synchronization recovery protection time (T) of the error correction frame in the procedure (3) in FIG. 5 and the procedure (7) in FIG. 6 is used by referring to a predetermined value calculated in advance. The synchronization recovery protection time (T) of the error correction frame is a value obtained by adding a margin for stabilizing the operation to the re-locking time of the error correction frame synchronization of the image decoding device.

Here, the image decoding devices of the terminals 21 to 2N operate 340 after the phase of the error correction frame is switched.
Since the frame synchronization is designed to be reacquired within 00 transmission clocks, the reacquisition time for the error correction frame synchronization can be easily calculated from the image transmission speed. Experience has shown that the synchronization recovery protection time (T) of the error correction frame is about 2 to 3 times the re-lock time of the error correction frame synchronization.
Double value is set.

In FIG. 6, the completion of the mode change of the video conference terminal means that the MCS and the command LSB <B> in the procedure (4) in FIG.
The determination is made by receiving SD <B>.

However, in the conventional multipoint video conference control apparatus having the above-described processing procedure, the mode change is required because the synchronization recovery protection time (T) of the error correction frame changes depending on the image transmission speed. A suitable value must be referred each time the operation is performed, and the control is very troublesome. Further, since this value is a fixed value assuming the worst case of synchronization re-pulling, even if synchronization re-pulling is completed in a short time, it is not possible to shift to the next processing during the protection time. Therefore, there is a disadvantage that the time until a new image is displayed becomes long.

Further, in the system control unit, since the command transmitted / received to / from the terminal is transmitted at a very low transmission rate and is not synchronized with the content of the video coded data, the mode change is actually completed. However, there is a drawback that it is not possible to shift to the next process until notified by a command.

Here, as a prior art, for example,
Japanese Patent Application Laid-Open No. 7-207485 (hereinafter referred to as prior art) includes a gate circuit that turns on and off by a trigger at a television vertical timing, in addition to a first latch circuit that latches data from a computer at a computer timing. ,
A "video switcher control method" is disclosed in which a plurality of video switchers can be switched at the same timing by controlling the output of a first latch circuit by a gate circuit.

[0024]

As described above, in the conventional multipoint video conference control device, it takes time to control the switching of images and the mode change.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a multipoint video conference control device capable of shortening the processing time for image switching and mode change by simple processing. And

Here, the prior art 1 discloses an invention of a "video switcher control system" for switching at the same timing, and detects synchronization of an error correction frame as in the present invention. It does not disclose any technical idea of shortening the processing time of image switching or mode change by performing switching.

[0027]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a plurality of video conferences having media of image, voice, and data, and multiplexing and outputting each of the media with the same transmission speed and signal format. An interface unit to which each terminal is connected via a communication path for inputting / outputting multiplexed data to / from each terminal; separating means for separating image data from multiplexed output data of each terminal input from the interface unit; Image data exchange means for exchanging image data separated for each terminal by means, and re-multiplexing the image data exchanged by the image data exchange means with other media transmission data to a predetermined terminal, and the interface unit in multipoint video conference control device and a multiplexing means for sending to the terminal through at the separating means
Error correction frames included in the image data of each separated terminal
Synchronization of image data of each terminal by detecting
At the timing of detection of this error correction frame.
An error correction module that outputs a reception synchronization timing pulse every time
Frame synchronization detection circuit and the reception synchronization obtained by this detection circuit.
Of any of the initial timing pulses
And the reception synchronization timing
A transmission synchronization timing pulse generating means for generating a synchronization with the transmission synchronization timing pulses to the pulse, converts the output phase of the image data of each terminal separated by the separating means in a single phase represented by the transmission synchronous timing pulses And a buffer memory circuit for outputting the image data to the image data exchange means.

Further, there is provided a matching determining means for monitoring whether the error correction frame synchronization of the image data is established, thereby determining whether or not the transmission speed on the communication path matches between the self and the video conference terminal. Video conference terminal
Mode change system for transmitting image data to other video conference terminals
At your time, freeze the screen of the video conference terminal
After the matching is determined by the matching determining means.
Requesting the one video conference terminal to update the screen,
The multipoint video conference control system according to claim 1 , wherein the freeze of the screen is released afterwards .

[0029]

In the multipoint video conference control device having the first characteristic, the image data transmitted to the terminal is supplied to the image data exchange means by supplying the image data synchronized with the transmission synchronization timing pulse. Is not changed before and after image switching.

In the multipoint video conference control device having the second feature, the state of establishing the error correction frame synchronization of the image data is further monitored, and the transmission speed on the communication path is matched between itself and the video conference terminal. By determining whether or not the recovery protection time for the error correction frame synchronization is not required, the control software is simplified.

[0031]

An embodiment of the present invention will be described below in detail with reference to the drawings. However, in FIG. 1, the same portions as those in FIG. 4 are denoted by the same reference numerals, and different portions will be mainly described here.

FIG. 1 is a block circuit diagram showing a configuration of an image signal exchange unit of the multipoint video conference control device according to the present invention. The image signal exchanging unit 1 shown here has a corrected frame synchronization detection circuit (VFEC-DET) in addition to the configuration of FIG.
31 to 3N, a selector circuit (SEL) 4, a counter circuit (CTR) 5, and a buffer memory circuit (BM) 6
1 to 6N.

Error correction frame synchronization detection circuits 31 to 3N
Detects the synchronization of the error correction frame from the video coded data A1 to AN separated by the MUX / DMUXs 81 to 8N, and outputs the synchronization establishment states E1 to EN and the reception synchronization timing pulses C1 to CN.

The selector circuit 4 receives the reception synchronization timing pulses C1 to CN output from the error correction frame synchronization detection circuits 31 to 3N, and generates a transmission synchronization timing pulse D to be described later based on transmission / reception control of the system control unit 10. This is for synchronizing with any of the reception synchronization timing pulses C1 to CN.

The counter circuit 5 counts the reception synchronization timing pulses C1 to CN selected by the selector circuit 4 to determine the phase of the error correction frame of the video encoded data B1 to BN to be sent to the terminals 21 to 2N. , A transmission synchronization timing pulse D is generated. The transmission synchronization timing pulse D is transmitted to the buffer memory circuits 61-6.
N.

The buffer memory circuits 61 to 6N have MUX
/ DMUXs 81 to 8N, and receives the encoded video data A1 to AN, and converts the phase into the phase indicated by the transmission synchronization timing pulse D from the counter circuit 5. The converted output is sent to the video data converter 7.

In FIG. 1, the selector circuit 4 is not an essential component of the present invention.

The operation of the image signal exchange unit of the present invention will be described below with reference to FIGS. FIG. 2 is a sequence diagram showing an example of the image exchange, and FIG. 3 is a sequence diagram showing an example of the mode change.

First, in the case of image exchange control, the system control unit 10 monitors the synchronization detection states E1 to EN of the error correction frame synchronization detection circuits 31 to 3N, and counts any one of the reception synchronization timing pulses for which synchronization has been established. The selector circuit 4 is switched so as to be supplied to the circuit 5. The counter circuit 5 generates a transmission synchronization timing pulse D in synchronization with this. As a result, in all video encoded data output from the buffer memory circuits 61 to 6N, the phase of the error correction frame is synchronized with the transmission synchronization timing pulse D from the counter circuit 5.

As described above, the video data exchange unit 7
Is supplied with synchronized video coded data, the phases of the error correction frames of the video coded data B1 to BN transmitted to the video conference terminals 21 to 2N do not change before and after the image switching. Therefore, since the video conference terminals 21 to 2N do not lose synchronization of the error correction frame, the system control unit 10 does not need to consider the synchronization recovery protection time. A change request (VCU) command can be sent.

FIG. 2 shows that the source of the image received by the video conference terminal TA is changed from the video conference terminal TB to the video conference terminal T.
This is the image exchange control when switching to C, and is performed according to the following procedure.

(1) A screen freeze command (VCF) is transmitted to freeze the screen being received by the video conference terminal TA. (2) The image received by the video conference terminal TA is switched from the video conference terminal TB to the video conference terminal TC. (3)
Screen update request command (VCU) to TV conference terminal TC
Issue (4) A freeze screen release command is transmitted from the video conference terminal TC together with the initialized / updated video coded data, and the video conference terminal TA receives this and releases the freeze on the screen.

Next, a mode change procedure in the multipoint video conference control device of the present invention will be described.

As described above, the data of the video conference terminal is handled by a multimedia signal obtained by multiplexing the image, the voice, and the data, and all bits not allocated to the voice and the data are allocated to the image. Therefore, for example, when the mode change is started so as to open the data channel at the transmission rate <B>, the transmission rate of the image temporarily becomes inconsistent with the video conference terminal, and the synchronization of the error correction frame is lost. Then, when the data channel is opened and the mode change is completed, the image transmission speeds match, and the synchronization of the error correction frame is restored. Therefore, by monitoring the establishment state of the synchronization of the error correction frame, the completion of the mode change is completed. Can be determined.

FIG. 3 shows a mode change control in the case where a data channel is opened in response to a request from the video conference terminal TB and the data transmitted by the video conference terminal TB is received by the video conference terminals TA and TC. Done.

(1) The video conference terminal TB receives the token request command (DCA-L, <B>). (2) Set the data to be distributed to ALL “1” (idle bit).
(3) A screen freeze command (VCF) and a video-off command are transmitted to freeze the screen being received by the video conference terminals TA, TB, and TC, and stop the transmission of the video encoded data. (4) The command MCS, LSD <B> instructs the video conference terminals TA, TB, TC to open the data channel at the transmission rate <B> requested by the video conference terminal TB. (5) The transmission of the encoded video data is restarted by the video-on command.

(6) The synchronization establishment state of the error correction frame of the video coded data received from the video conference terminals TA, TB, TC is monitored, and it is confirmed that the data transmission speed is matched by the restoration of the synchronization. (7) Issue a screen update request (VCU) command to the source of the image. As a result, the video encoding data initialized / updated is transmitted from the image transmission source, and the video conference terminals TA, TB. TC receives this and releases the freeze on the screen. (8) Make settings for distributing the data transmitted by the video conference terminal TB to the video conference terminal TA and the video conference terminal TC. (9) The DIT-L command notifies the video conference terminal TB that the token has been given. (10) A data format command (data application bus command) is received from the video conference terminal TB and distributed. (11) Video conference terminal T
B starts transmitting data in real time.

As described above, the multipoint video conference control apparatus of the present invention is different from the conventional one in which the switching is performed without adjusting the phase of the error correction frame of the video coded data when the image is switched. In this case, the time required to output the updated image signal can be reduced by the amount corresponding to the synchronization recovery protection time, and when the mode is changed, by the amount corresponding to the transmission delay of the command and the synchronization recovery protection time of the error correction frame.

In addition, since the recovery protection time of the error correction frame synchronization conventionally changes depending on the information transmission speed of the video coded data, it is necessary to refer to an appropriate value every time the mode is changed. However, since this setting becomes unnecessary, there is an effect that control software can be simplified.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0051]

As described above, according to the present invention, it is possible to provide a multipoint video conference control device capable of shortening the processing time for image switching and mode change by simple processing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a multipoint video conference control device according to an embodiment of the present invention, particularly, an image signal exchange unit.

FIG. 2 is a sequence diagram illustrating an example of image exchange according to the embodiment.

FIG. 3 is a sequence diagram illustrating an example of a mode change of the embodiment.

FIG. 4 is a block diagram illustrating a configuration of a conventional multipoint video conference device, particularly, a configuration of an image signal exchange unit.

5 is a sequence diagram showing an example of image conversion in the conventional configuration of FIG.

6 is a sequence diagram showing an example of a mode change in the conventional configuration of FIG.

[Explanation of symbols]

1 Multipoint Video Conference Controller (MCU) 21-2N Video Conference Terminal 31-3N Error Correction Frame Synchronization Detection Circuit (VFEC
-DET) 4 Selector circuit (SEL) 5 Counter circuit (CTR) 61-6N Buffer memory circuit (BM) 7 Video data exchange unit 81-8N MUX / DMUX 91-9N Line interface unit (LIF) 10 System control unit A1 to AN Received encoded video data B1 to BN Transmitted video encoded data C1 to CN Reception synchronization timing pulse D Transmission synchronization timing pulse E1 to EN Synchronization established state F Control data bus

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N ^7/ 14-7/15 H04N ^7/ 24-7/68

Claims (2)

(57) [Claims] 1. It has an image, sound, and data media,
A plurality of video conference terminals for multiplexing and outputting each medium with the same transmission speed and signal format are connected via a communication path, respectively, and an interface unit for inputting / outputting multiplexed data to / from each terminal and an input from this interface unit Separating means for separating image data from multiplexed output data of each terminal, image data exchanging means for exchanging image data separated for each terminal by the separating means, and image data exchanged by the image data exchanging means. Multiplexing means for re-multiplexing the data with other media transmission data to a predetermined terminal and transmitting the data to the terminal through the interface unit, the image data of each terminal separated by the separation means. Included in
Image data of each terminal by detecting
Data, and detects the error correction frame.
Output reception synchronization timing pulse for each terminal at the timing
Error-correction frame synchronization detection circuit, and a reception synchronization timing pulse obtained by the detection circuit.
Counts any pulse and counts the number of times
Then, a transmission synchronization timing pulse generating unit that generates a transmission synchronization timing pulse in synchronization with the reception synchronization timing pulse, and an output phase of image data of each terminal separated by the separation unit is determined by the transmission synchronization timing. A multipoint video conference control device, comprising: a buffer memory circuit for converting the signal into a single phase represented by a pulse and outputting the converted signal to the image data exchange means. 2. An apparatus according to claim 1, further comprising a matching determination unit that monitors whether an error correction frame synchronization of the image data is established, and determines whether a transmission speed on the communication path matches between the communication terminal and the video conference terminal. , One of the video conference terminals
Mode change for transmitting image data to other video conference terminals
During control, freeze the screen of the video conference terminal.
The matching has been determined by the matching determining means.
Later, it requests the one video conference terminal to update the screen, and
2. The method according to claim 1, further comprising: releasing the freeze of the screen after the step.
A multipoint video conference control system as described.