JPH10126755A - Videophone / videoconference terminal, ring multipoint videophone / video conference system using the same, and communication control method - Google Patents

Abstract

(57) [Problem] To provide a multipoint videophone / videoconference system with a sense of reality. Also H.
The purpose is to realize a videophone / videoconference based on the 263 system. A system based on H.263 uses a CPM mode. Then, it is determined from the PSB identifier which terminal has transmitted the image data following the identifier. If it is image data of a terminal downstream of its own terminal, it is deleted, image data of its own terminal is inserted, and if it is another terminal, the PSB identifier is converted and transferred. Also, during a conference, an interval at which each terminal transmits an image to a transmission path or a transmittable code amount is determined by designation from a certain terminal or negotiation between the terminals. Each terminal sends an image of its own terminal to the transmission path based on this decision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a videophone / videoconference terminal located at a plurality of locations, which is used for ISDN (Integrate
The present invention relates to a technology of multipoint videophone / videoconference in which a plurality of terminals are connected in a ring via a line such as d Services Digital Network) and communicate with each other.

[0002]

2. Description of the Related Art ISDN has a basic unit of a channel having a transmission speed of 64 kbit / s, and a communication line having two channels is widely used. The connection destinations of these two channels can be set independently of each other, and terminals connected to a plurality of locations can be connected in a ring by connecting each channel to a different partner. Regarding the technology of performing multipoint videophone / conference by circulating conference data on the ring set in this way, USP 5,365,265, USP 5,402,418 (Japanese Patent Laid-Open No. 5-223)
No. 21, JP-A-5-23222).

[0003] In the above prior art, ITU-T H.261 is used.
(International TelecommunicationUnion-Telecommunic
ation section H.261), image data is encoded and transmitted / received by an international standard image encoding method. H.
There are two types of image formats to be encoded by 261. One is a format called FCIF, which has a resolution of 352 pixels in the horizontal direction and 288 scanning lines in the vertical direction. The other is a resolution of FCIF in both the horizontal and vertical directions.
Half (176 pixels horizontally, 144 scan lines vertically) QC
This is a format called IF. An image frame defined by H.261 (hereinafter, referred to as an H.261 frame) stores an encoded signal for one frame of an FCIF image. H.2
61 frames are composed of a header section and an image data section. The image data section is composed of 12 GOBs (Group of blocks). The GOB image size is 176 pixels horizontally and 48 scan lines vertically, one-twelfth of FCIF and one-third of QCIF.
Image size. In the above conventional technology, GOB1
Among them, for example, GOBs 1, 3, and 5 are assigned to terminal A, GOBs 2, 4, and 6 are assigned to terminal B, GOBs 7, 9, and 11 are assigned to terminal C, and GOBs 8, 10, and 12 are assigned to terminal D. Then, each terminal removes the old QCIF image of its own terminal stored in the allocated GOB, stores the newly generated QCIF image in the allocated GOB, and transmits it. Then, since one H.261 frame includes the QCIF images of the terminals A, B, C, and D, the terminal receiving the H.261 frame displays the four QCIF images transmitted from a plurality of points on the screen. This is combined with one FCIF image and displayed. As described above, in the above-described conventional technique, a ring-type multipoint videophone / videoconference is realized between a plurality of terminals.

[0004]

However, in a conventional ring-type multipoint videophone / videoconference, a terminal to which a GOB is assigned stores a QCIF image in each H.261 frame. The number of screens of the QCIF image to be transmitted was equal.

Therefore, in a conventional ring-type multipoint videophone / videoconference, the number of screens transmitted by a certain terminal cannot be made larger than the number of screens transmitted by another terminal.

[0006] H.261 image coding is a variable length coding method. Therefore, the encoding speed at each terminal is not constant, and the time required to generate a QCIF encoded image for one screen is variable. Nevertheless,
Since the number of screens transmitted by all terminals is the same, there is a problem that the delay time of H.261 frame transmission increases due to the effect of the terminal having a low encoding speed.

On the other hand, as a next-generation encoding method of H.261,
A scheme called H.263 has recently been adopted as a standard. H.263 is expected to be widely used in the future. H.263 also has a GOB image data unit, but in QCIF mode and FCIF mode
GOB sizes are different. Therefore, in the H.263-based system, a ring multipoint videophone / conference cannot be realized by the method used in the H.261-based system.

An object of the present invention is to provide a method for controlling the amount of image data transmitted from each terminal in a multipoint videophone / videoconference system.

[0009] Further, the object of the present invention is to specify according to its own terminal or according to the specification from another terminal.
An object of the present invention is to provide a multipoint videophone / videoconference terminal that controls the transmission amount of image data.

It is another object of the present invention to provide a multipoint videophone / videoconference system capable of controlling the amount of data transmitted by each terminal.

Another object of the present invention is to increase the number of display frames of an image of a participant who is speaking to be larger than the number of display frames of other participants, thereby enabling a multi-point videophone / video to be displayed with a sense of reality. To provide a video conference system.

Another object of the present invention is to provide a communication method for increasing the number of display frames of an image of a participant who is speaking to the number of display frames of another participant to enable a realistic display. To provide.

It is another object of the present invention to increase the number of display frames of an image of a participant who is speaking to be larger than the number of display frames of other participants, thereby realizing a realistic display. It is to provide a video conference terminal.

It is another object of the present invention to provide a ring-type multipoint videophone / conference system suitable for H.263.

It is another object of the present invention to provide a communication method suitable for H.263 in a ring-type multipoint videophone / conference system.

It is another object of the present invention to provide a ring-type multipoint videophone / conference terminal suitable for H.263.

[0017]

In order to achieve the above object, a ring-type multipoint videophone / videoconference system of the present invention connects a plurality of terminals in a ring shape, and
The frame frequency or code amount of the image data generated and transmitted by the own terminal is controlled based on the control from the own terminal or another terminal.

Further, image data transmitted from a plurality of terminals is simultaneously displayed on a screen, and each terminal generates and transmits the image data on its own terminal under the control of its own terminal or another terminal. By controlling the frame frequency of image data, an image generated by the speaker's terminal is displayed at a higher frame frequency than an image generated by another terminal on the display screen of each terminal. Things.

Also, as an encoding method of image data, ITU-
Using the continuous presence multipoint mode of T H.263, the PSB identifier of the H.263 frame based on the received H.263 is detected, and the image data of the H.263 frame is stored in the own terminal. If the image data is generated by one downstream terminal, delete the image data.If the image data is generated by another terminal, delete the image data to the terminal downstream of the own terminal. Sending, and further transmitting the image data captured and encoded by the own terminal to the downstream terminal, and performing communication by circulating the image data transmitted from each terminal through a ring-shaped line. It was made.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a ring multipoint videophone /
A case where a video conference is held between terminals installed at five locations will be described with reference to FIGS.

FIG. 1 is an overall configuration diagram of a video telephone / video conference system between five points.

Each terminal connects the two ISDN channels to separate terminals, and makes a ring between terminals A1, E2, D3, C4 and B5 participating in a multipoint videophone / video conference. A communication path in the shape of a circle.

FIG. 2 shows a display screen of the terminal E when a videophone / videoconference communication is being performed between the five points.

When communication is performed between five points, a QCIF image 24 of terminal A, a QCIF image 23 of terminal B, a QCIF image 22 of terminal C, and a QCIF image 21 of terminal D are displayed on the screen of terminal E. You.
Each terminal combines the QCIF images transmitted by the terminals at four points other than itself and displays them on the screen as one FCIF image. This allows each terminal to see the images of all the other parties.

Hereinafter, the configuration and operation of each terminal for performing such a screen display will be described.

FIG. 3 shows an image transmission frame according to H.261.
(H.261 frame) is shown.

As shown in the figure, an H.261 frame has a picture start code (hereinafter referred to as PSC: Picture Start Code).
) And GOB (Group of Block) 1
It is composed of a data section 302 composed of 12 data. 12 GOBs are data for one FCIF. PSC is data for synchronization.

FIG. 4A shows the relationship between the GOB and the display position of the QCIF image on the screen, and FIG. 4B shows the relationship between the GOB and the display position of the FCIF image on the screen.

The image size of the GOB is, as described above,
There are 176 pixels in the horizontal direction and 48 scanning lines in the vertical direction. This G
As shown in FIG. 4, the relationship between the OB and the above-mentioned QCIF and FCIF formats is such that one QCIF image screen is composed of three GOBs.
One CIF image screen is composed of 12 GOBs. The relationship between each GOB number and the display position on the screen is as follows. In the case of QCIF, for example, image data of GOB numbers 1, 3, and 5 are displayed in order from the top as shown in FIG. As shown in FIG. 4B, image data of GOB numbers 1 to 12 are displayed in order from the upper left. Therefore, in order to display the screen as shown in FIG. 2 on the terminal E, the terminals D, C, and C of GOBs 1, 3, and 5 of the H.261 frame received by the terminal E are displayed. GOB7,9,1
It is sufficient that the terminal 1 stores the QCIF image of the terminal B and the GOBs 8, 10, and 12 store the QCIF image of the terminal A.

Next, the configuration and operation of each terminal will be described with reference to FIGS.

FIG. 5 shows the configuration of a ring multipoint videophone / videoconference terminal.

Each terminal receives the H.261 frame transmitted from the terminal on the upstream side of the ring through the receiving-side transmission path 503. The received H.261 frame is received by the received signal conversion circuit 5
04 and sent to the image decoding circuit 510.

The reception signal conversion circuit 504 includes a transmission line 503 on the reception side.
Of the QCIF image generated by the terminal downstream of the own terminal from among the encoded signals stored in the GOBs 1 to 12 of the data portion of the H.261 frame received from the H.261 frame. Here, it is assumed that the GOB assigned with the GOB numbers 1, 3, and 5 is a QCIF image transmitted by a terminal located downstream of its own terminal. For encoded signals of QCIF images generated by other terminals, the GOB numbers are converted.

FIG. 6 shows an example of a GOB number conversion rule.

As shown in FIG. 6, the coded signals provided with GOB numbers 2, 4, and 6 have the GOB numbers 1, 3, and 5, and the coded signals provided with GOB numbers 7, 9, and 11 have Coded signals with GOB numbers of 2, 4, and 6 and GOB numbers of 8, 10, and 12 have GOB numbers of
Replaced by 7,9,11.

The received signal converted by the received signal conversion circuit 504 is written in the buffer memory 505.

The PSC detection circuit 506 detects a PSC from the received signal read from the buffer memory 505.

When the PSC is detected by the PSC detection circuit 506, the control circuit 507 stores the header section including the PSC in the buffer memory 505.
To the transmission line 509 on the transmission side. Then, the control circuit 507
Stops reading the received signal from the buffer memory 505 once. Then, the switch 508 is switched to the image encoding circuit 502 side, and the image encoding circuit 502 is controlled so as to start encoding the image of the own terminal captured by the camera 501.

The image encoding circuit 502 encodes an encoded signal (QCIF image) of an image of its own terminal, and outputs the GOB numbers 8, 10,
12 is transmitted to the transmission line 509 on the transmission side. When completing the transmission of the encoded signal of the QCIF image to the transmission-side transmission path 509, the image encoding circuit 502 notifies the control circuit 507 of the completion signal.

The control circuit 507 again controls the image encoding device 502,
By transmitting a control signal to the buffer memory 505 and the switch 508, the encoding of the image encoding device 502 is stopped, and the switch 5
08 is switched to the buffer memory 505 side. Then, reading of the received signal stored in the buffer memory 505 is restarted, and the encoded signal stored in the data section of the buffer memory 505 is transferred to the transmission line 509. At this time, the GOB numbers of the data portion read from the buffer memory 505 are 1, 3,
5 and 2,4,6 and 7,9,11.

On the other hand, the image decoding circuit 510 decodes the image data stored in GOBs 1 to 12 of the H.261 frame received from the upstream terminal via the transmission line 503 on the receiving side. The display device 511 displays the decoded image data on the screen at the position shown in FIG.

FIG. 7 shows the operation of each terminal described above as a whole system.

The terminal A 701 displays the images of the terminals E, D, C, and B contained in the received H.261 frame 710 on the screen, while displaying the QCIF of the downstream terminal E in the received signal.
The GOB720 storing the coded signal of the image is deleted, and the coded signals of the QCIF images of the other terminals D, C, and B are stored.
The GOB changes the number, stores the encoded signal 721 of the QCIF image of its own terminal in the vacant GOB, and transmits it.

Next, the terminal E702 receives the H.261 frame 711 transmitted from the terminal A701, and displays the images of the terminals D, C, B, and A included in the received signal on the screen. On the other hand, the GOB722 in which the coded signal of the QCIF image of the terminal D on the downstream side among the received signals is deleted, and the other terminals C and
The GOB storing the coded signals of the QCIF images of B and A changes the number, and the coded signals of the QCIF image 723 of the own terminal are changed.
Is stored in the vacant GOB and transmitted to the terminal D. Similarly, in this system, conference communication is performed by circulating H.261 frames on the ring while deleting and inserting.

In this way, in a five-point ring multipoint videophone / videoconference system based on H.261, a conference is performed by displaying images of all other parties on the screen of its own terminal. Communication can be performed.

Next, an embodiment in which the number of QCIF images transmitted for each terminal is made variable in a multipoint videophone / video conference based on H.261 will be described with reference to FIGS.

In this embodiment, a certain terminal is a GOB
Only the GOB Header is transmitted without transmitting the contents of When the receiving terminal receives only the GOB Header, it is considered that there is no change from the previously received screen. If only the GOB Header is transmitted and the content of the GOB is not transmitted, the amount of data transmission can be saved, and the saved amount can be allocated to another terminal. As a result, it is possible to increase the image quality and the number of images transmitted by a certain terminal.

FIG. 8 is a block diagram of a multipoint videophone / videoconference terminal according to this embodiment. In this figure, the same components as those in FIG.

The counter 812 detects the PS detected by the PSC detection circuit.
Count the number of C. Register 813 contains a predetermined
A threshold for the number of PSCs has been entered. A method of setting the threshold is, for example, as follows. FIG. 10 shows a sequence for explaining the threshold setting operation. Each terminal participating in the multipoint videophone / videoconference measures the volume input from the microphone 815 with the volume meter 816 at any time or at a designated time, and compares the result with a representative terminal (a terminal serving as the chairman). , Hereinafter referred to as chair terminal). The chair terminal
First, the volume information sent from each terminal and the volume information of its own terminal are analyzed. Next, the speech terminal is determined from the analysis result. Then, a cycle at which each terminal transmits image data to the transmission path is determined, and a register value of each terminal is determined. Then, each terminal is notified of the register value. Each terminal decodes this notification in the analysis circuit 217 and sets the transmission cycle of the image data in the register 213. As a method of notifying each terminal, for example, a BAS is used when complying with ITU-T H.320 that defines a communication procedure of a videophone / video conference, and, for example, a data packet is used when complying with H.324.

Returning to FIG. 8, the value of the counter 812 is determined by comparing the threshold value of the register 813 set as described above with the comparison circuit 8
Compared at 14. Until the number of PSCs set in the register 813 is detected, the control circuit 807 determines that the GOBs 8, 10,
12 sends only the GOB header to the transmission line 509,
The buffer memory 505 and the image signal encoding circuit 102 are controlled. It does not transmit QCIF images generated by its own terminal.

When the control circuit 807 receives notification from the comparison circuit 814 that the number of PSCs set as the threshold has arrived, the control circuit 807 controls to operate in the same manner as the conference communication at the five points described above. . That is, the QCIF image of the terminal downstream of itself is deleted, the GOB storing the QCIF image of the other terminal changes the number, and the QB of the own terminal is changed to GOB 8, 10, 12.
The coded signal of the CIF image is stored and transmitted to the transmission line 509 on the transmission side. Then, the value of a counter 812 for counting the number of PSCs is initialized to zero. The counter 812 starts counting PSC again,
Hereinafter, the same processing is repeated.

FIG. 9 is a diagram showing this operation as a whole system. Although only one H.261 frame transmitted on the ring is illustrated in FIG. 7, a plurality of H.261 frames are actually transmitted per second. In this example
A description will be given by showing three H.261 frames.

Here, it is assumed that terminal D is the speaker terminal. For the speaker terminal D903, 0 is set in the register value. Other terminals A901, B905, C90
4. The terminal E902 sets 2 to the register value.

As a result, the terminal D903 stores the encoded data 935 of the QCIF image of its own terminal in all the received H.261 frames 916, 917, 918 and transmits it. The other terminals A901, B905, C904, and E902 have three H.323 terminals.
Each time 261 frames are received, the encoded data of the QCIF image is stored. At other times, only the GOB header is transmitted. As a result, a larger code amount can be allocated to the terminal D than to the other terminals A, B, C, and E. Or,
The number of QCIF images transmitted by the terminal D is
It can be larger than the number of sheets transmitted by B, C and E.

The embodiment of the system based on H.261 has been described above.

Next, referring to FIG. 11 to FIG.
A technology for realizing a ring multipoint videophone / videoconference based on the Internet will be described.

In this embodiment, a function called a continuous presence multipoint mode (hereinafter, CPM mode) adopted as an option in H.263 is used. This CPM mode is set for a multipoint video conference system using a multipoint video conference control device (hereinafter MCU: Multipoint Communication Control Unit). Unlike a ring type, a multipoint videophone / videoconference system using an MCU connects all terminals that intend to participate in a videophone / conference to this MCU. The MCU performs control such as combining and editing the data sent from each terminal and returning the data to each terminal. MCU
In a system using, the line from the terminal to the MCU is usually 6
4 kbit / s, and the line from the MCU to the terminal is 240 kbit / s. The number of terminals that can be connected to the MCU is limited, and the number is, for example, four.

The present invention realizes a ring multipoint videophone / videoconference by applying the CPM mode. Further, the present invention further realizes a realistic videophone / videoconference by controlling the number of images or the amount of data transmitted from each terminal to a ring in an H.263-based system. It is. In a multipoint videophone / videoconference system using an MCU, control of the number of images and the amount of data has not been considered because the line capacity is large.

The transmission frame structure in the H.263 CPM mode will be described below.

FIG. 11 shows the configuration of an H.263 transmission frame in the CPM mode.

The H.263 frame in the CPM mode corresponds to the PSC1101
And PSB identifier (Picture Sub Bitstream Indicator) 1102
And an image data section 1103. The image data of the image data section 1103 is an encoded signal obtained by encoding an image captured by one terminal in the QCIF format. Up to four pairs of the PSB identifier and the image data part can be continued following the PSC. That is, PSC + PSB identifier + QCIF image data (+ P
SB identifier + QCIF image data ... 4 at most ...). The PSB identifier 1102 is used to identify to which terminal the image data following the identifier belongs. PSB
For example, a number from 0 to 3 is assigned to the identifier. MC
In a system using U, this identifier is fixedly associated with each terminal.

By using this PSB identifier, even in a ring multipoint videophone / videoconference system using H.263 of the present invention, the QC transmitted from a plurality of terminals can be used.
The IF image is combined with the FCIF image and displayed on the screen. The PSB identifier and the screen display position on the display device are, for example, as shown in FIG.
As shown in the figure, the QCIF image having the PSB identifier 0 is located at the upper left of the screen, the QCIF image having the PSB identifier 1 is located at the upper right of the screen, and the QCIF image having the PSB identifier 2 is located at the lower left of the screen.
The QCIF image having the identifier 3 is set to be displayed at the lower right of the screen.

Next, the configuration and operation of each terminal in this embodiment will be described with reference to FIGS.

FIG. 13 is a block diagram of a ring multipoint videophone / videoconference terminal according to this embodiment.

The H.263 frame sent from the terminal on the upstream side of the ring via the transmission line 1303 on the receiving side is sent to the buffer memory 5 and the image decoding circuit 1310.

The PSC / PSB identifier detection circuit 1306 reads the received signal from the buffer memory 1305 and detects the PSC.

When a PSC is detected by the PSC / PSB identifier detection circuit 1306, the control circuit 1307 stores the PSC in the buffer memory 130.
Transfer from 5 to the transmission line 1309 on the transmission side. Further, the PSC / PSB identifier detection circuit 1306 reads the received signal from the buffer memory 1305 and detects a PSB identifier.

When the value of the PSB identifier is 0, the encoded signal of the QCIF image stored in the buffer memory 1305 following the PSB identifier is deleted. Because, in this embodiment, when the value of the PSB identifier is 0, the QCI following the PSB identifier
This is because the F image data is generated by a terminal downstream of its own terminal. Then, the control circuit 1307 switches the switch 1308 to the image encoding circuit 1302 side, and controls the image encoding circuit 1302 to start encoding an image of its own terminal captured by the camera 1301.

The image encoding circuit 1302 sends an encoded signal (QCIF image) of the image of the terminal itself to the transmission line 1309 on the transmission side. When transmitting a coded signal (QCIF image) of an image of the own terminal, the PSB identifier is 3. Image coding circuit 13
02 notifies the control circuit 1307 of the completion signal when the transmission of the encoded signal of the QCIF image or the dummy data to the transmission side transmission line 1309 is completed.

The control circuit 1307 returns to the image encoding device 130 again.
2. A control signal is sent to the buffer memory 1305 and the switch 1308 to stop the encoding of the image encoding device 1302, and the switch 1308 is switched to the buffer memory 1305 side. Then, reading of the received signal stored in the buffer memory 1305 is restarted.

If the value of the PSB identifier detected by the PSC / PSB identifier detection circuit is 1 to 3, the received signal conversion circuit 1304 converts the PSB identifier and transmits the image data to the transmission line 1 on the transmission side.
Send to 309. Because the value of the PSB identifier is 1 to 3
In the case of, the image data following the PSB identifier is an encoded signal of a QCIF image generated by a terminal other than the terminal downstream of itself.

FIG. 14 shows an example of a PSB identifier conversion rule.

In the received signal conversion circuit 1304, as shown in FIG. 14, the coded signal provided with the PSB identifier 1 has the PSB identifier 0, and the coded signal provided with the PSB identifier 2 has the PSB identifier 1. , The coded signal provided with the PSB identifier 3 replaces the PSB identifier with 2.

Multiple (up to 4) in one H.263 frame
If the set of the PSB identifier and the QCIF image data is included in the buffer memory 1305, the process of detecting the PSB identifier and transmitting the image data is repeatedly performed until there is no more set of the PSB identifier and the QCIF image data in the buffer memory 1305.

The image decoding circuit 1310 includes a transmission line 1303 on the reception side.
And decodes the received signal from the
In accordance with the B identifier, it is displayed on the display device 11 at the position specified in FIG.

FIG. 15 is a diagram showing the operation of the present embodiment as a whole system.

In the case of a system based on H.263, H.2
63 One frame is a PSB containing 1-4 QCIF images
including. Therefore, in this figure, in order to make the description easy to understand, it is illustrated in units of PSB.

Each time terminal A 1501 receives an H.263 frame, it displays an image stored in the PSB included in at least one of the H.263 frames on the screen.
On the other hand, if the encoded signal of the QCIF image of the terminal E on the downstream side is stored in the PSB of the received H.263 frame, the QCIF
The image 1520 is deleted. And the Q included in the H.263 frame
If the CIF image is that of another terminal D, C, or B, the PSB identifier is changed, and the coded signal 1521 of the QCIF image of the own terminal is transmitted following the PSB identifier 3.

The terminal E 1502 receives the H.263 frame transmitted one after another from the terminal A 1501. In the terminal E1502, the terminal D stored in the PSB included in at least one of the H.263 frames transmitted from the terminal A1501,
While the images of C, B, and A are displayed on the screen, if the encoded signal of the QCIF image of the terminal D1503 on the downstream side is stored in the H.263 frame, the QCIF image 1522 is deleted. For the QCIF images of the other terminals C, B and A, the PSB identifier is changed, and the coded signal 1523 of the QCIF image of the own terminal is changed to the PSB image.
The identifier is transmitted as 3 to the terminal D. The following terminal D1503,
Similarly, in C1504 and B1505, conference communication is performed by circulating image data on the ring. As above
A ring multipoint videophone / videoconference system in H.263 can be realized.

By the way, as described above, in H.263,
One H.263 frame contained only one QCIF image. This means that in an H.261-based system, the restriction that one H.261 frame always includes QCIF encoded images of all terminals has been removed. Therefore, another embodiment using this flexible frame configuration will be described below with reference to FIGS.

In this embodiment, means for changing the transmission interval of the QCIF image signal is provided in the ring multipoint videophone / videoconference terminal based on H.263. Then, the number of QCIF images to be transmitted from the terminal to the transmission path is controlled based on the control from the own terminal or another terminal.

FIG. 16 is a configuration diagram of a ring multipoint videophone / videoconference terminal in this embodiment.

In FIG. 16, the same components as those in FIG. 13 are denoted by the same reference numerals and description thereof will be omitted.

The counter 1612 is a PSC / PSB identifier detection circuit 1
506 is a P arranged at the head of the encoded signal of each QCIF image.
When the SB identifier is detected, the number of the PSB identifier is counted. However, it is not counted when the PSB identifier indicates a terminal downstream of itself.

A predetermined threshold value is input to the register 1613. As a method of setting the threshold, there is a method similar to that described with reference to FIG. 10 in the embodiment of H.261.

Returning to FIG. 16, the value of the counter 1612 is compared with the threshold value of the register 1613 set as described above in the comparison circuit 1614. Until the number of PSB identifiers set in the register 1613 is detected, the control circuit 1607
The coded signal of the QCIF image received from the receiving-side transmission path 1503 is transmitted to the transmitting-side transmission path 1509 via the reception signal conversion circuit 1504.
Control to send to However, the received QCIF image
When the PSB identifier is 0, the coded signal of the subsequent QCIF image is deleted and dummy data is transmitted instead. The dummy data is, for example, a sequence of 0s.

Upon receiving a notification from the comparison circuit 1614 that the number of PSB identifiers set as the threshold has arrived,
The control circuit 1607 includes an image encoding circuit 1502, a buffer memory
1505, outputs a control signal to the switch 1508, stops reading the encoded signal from the buffer memory 1505,
1508 is switched to the image encoding circuit 1502 side. Then, the control circuit 1607 activates the image encoding circuit 1502. The image encoding circuit 1502 starts encoding an image signal captured by the camera 1501, attaches the PSB identifier 3, and sends the signal to the transmission line 1509. Then, a counter 161 for counting the number of PSB identifiers
Initialize the value of 2 to 0.

When the transmission of the encoded signal is completed, the image encoding circuit 1502 notifies the control circuit 1607 of the completion signal. The control circuit 1607 outputs a control signal to the image encoding circuit 1502, the buffer memory 1505, and the switch 1508 again, stops encoding of the image encoding circuit 1502, switches the switch 1508 to the buffer memory 1505 side, and Reading of the encoded signal from 1505 is restarted. Then, the counting of the PSB identifier is started again, and the same processing is repeated thereafter.

FIGS. 17 and 18 show the above operation as a whole system.

In the following, it is assumed that terminal A is the chair terminal.

First, the operation when the intervals of the image data transmitted from each terminal are set to be the same will be described with reference to FIG. In the register 1613 of each terminal, 3 which is the same value for all terminals is set according to the notification from the chair terminal.

First, every time terminal A 1501 receives an H.263 frame, it receives the PSB included in the H.263 frame.
Displays the QCIF image stored on the screen. On the other hand, terminal A 1501 detects a PSB identifier. If the coded signal of the QCIF image following the PSB identifier is that of the terminal E1520 on the downstream side, the QCIF image is deleted from the value. PS
If the QCIF image following the B identifier is that of another terminal D, C, or B, the PSB identifier is changed and transmitted, and the number of received PSB identifiers is counted. When the number of received PSB identifiers reaches 3, the Q
The coded signal 1521 of the CIF image is transmitted. Then, the count value is reset.

Next, in terminal E1502, terminal A1501
And displays the QCIF image stored in the PSB included in the H.263 frame on the screen. On the other hand, terminal E1502 detects the PSB identifier.
If the encoded signal of the QCIF image following the PSB identifier is that of the terminal D1503 on the downstream side, the QCIF image 1522 is deleted from the value. If the QCIF image following the PSB identifier is that of another terminal C, B, or A, the PSB identifier is changed and transmitted, and the number of received PSB identifiers is counted. Then, when the counted number of received PSB identifiers becomes three, the terminal transmits an encoded signal 1523 of the QCIF image of its own terminal. Then, the count value is reset.

Thus, assuming that the register value of each terminal is 3, every time the PSB identifier is received three times, the QCIF of its own terminal is
Since the encoded signal of the image is inserted once, the number of QCIF images transmitted from each terminal is the same.

Next, the case where the terminal D1503 has become the speaker terminal will be described with reference to FIG. As described earlier with reference to FIG. 10, first, the chair terminal A1501 analyzes the sound volume measurement result received from each terminal, and determines that the terminal D1503 is the speaker terminal. Then, the register value of terminal D1503 is 1, terminal E
The register value of 1502 is determined to be 3, and the register values of the other terminals A, B, and C are determined to be 5. Then, this value is notified to each terminal. Each terminal receives this notification and sets the value in the register. As a result, the terminal D1503 transmits the QCIF image of its own terminal once each time the PSB storing the QCIF image of the terminal other than the terminal downstream of itself reaches once. Terminal E
1501 once every 3 times, other terminals once every 5 times
Send an IF image.

As a result, the number of screens transmitted by terminal D1503 is three times the number of screens transmitted by another terminal. As an example, FIG. 19 shows a screen displayed on the display device of terminal E1502. Thus, on the screen, the image of the terminal D, which is the speaker, is displayed at, for example, 30 frames / second, and the images of the other terminals A, B, and C are displayed at 10 frames / second.
Therefore, the image of the speaker has smooth motion and is easy to see, so that a realistic image can be obtained. Returning to FIG. 18, in the terminal E1502, the coded signal of the terminal D1503 that generates the coded signal of the QCIF image most frequently is deleted, and the coded signal 1523 of the QCIF image of the own terminal is inserted. I do. Therefore, the terminal E1502 lacks the coded signal to be transmitted to the terminal D1503. Therefore, terminal E1502 generates a dummy signal and compensates for the shortage. A dummy signal is a meaningless signal that does not conform to the rules of the frame.
Use continuous data of 0. In the terminal D1503, the received dummy signal is removed, and the QCIF
Insert the encoded signal of the image.

The method of determining the register value is such that the chair terminal analyzes and determines the volume measurement result of each terminal as described above, and each terminal transmits a speech request or request value to the chair terminal, and The terminal may determine the register value of each terminal based on the received request. Also, instead of being determined by the chair terminal, a plurality of terminals may negotiate and determine.

The following modifications are also within the scope of the present invention. That is, instead of counting the number of PCB identifiers, when receiving QCIF images from all terminals except the downstream terminal and the own terminal, the QCIF image of the own terminal may be inserted. This is especially because QC does not notify the presence or absence of the speaker by other means, each terminal independently captures its own terminal
This is suitable for determining the timing to start coding / inserting an IF image.

Also, in the above embodiment, the PSB identifier is converted so that any terminal can check the QC of one downstream terminal.
The PSB identifier of the coded signal of the IF image is set to 0. In this case, the operation of each terminal is common. However, the PSB identifier is fixedly assigned to the terminal, and the terminal itself recognizes the number of the PSB identifier of its own terminal, the downstream terminal, and other terminals, and deletes and inserts the QCIF image. Is also good.

In addition to setting the transmission interval of the QCIF image that can be transmitted by each terminal, the code amount that can be transmitted by each terminal may be set. Even if each terminal controls both codes that can be transmitted, under a limited capacity (64 kbit / s) communication line,
Effective image data transmission can be performed, and communication with a sense of reality can be realized by increasing the image quality of the speaker or the number of images.

In the above, the technology for realizing a ring multipoint videophone / videoconference based on H.263 and the technology for varying the number of QCIF images to be transmitted or the code amount for each terminal have been described.

As described above, according to the present invention, for example, the number of images transmitted by the speaker terminal can be made larger than the number of screens transmitted by other terminals, so that the movement of the speaker can be smooth. Thus, it is possible to provide a multipoint videophone / videoconference system with a sense of reality.

Further, according to the present invention, since a larger code amount can be allocated to the speaker terminal, it is possible to provide a multipoint videophone / videoconference system in which the image of the speaker is clear and realistic. it can. Further, according to the present invention, in the H.263 system, a ring-type multipoint videophone /
A meeting can be realized.

Further, the present invention can be realized by adding a few circuits to a conventional terminal.

[0105]

According to the present invention, a multipoint videophone / videoconference system having a sense of reality can be provided.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a videophone / videoconference system between five points.

FIG. 2 is a diagram showing an example of a display screen in the ring multipoint videophone / conference system.

FIG. 3 is a configuration diagram of an H.261 frame.

FIG. 4A is an explanatory diagram showing a relationship between display positions of QCIF and GOB on a screen. (b) It is explanatory drawing which shows the relationship of the display position on the screen of FCIF and GOB.

FIG. 5 is a block diagram of a ring multipoint videophone / conference terminal.

FIG. 6 is a diagram showing an example of a GOB number conversion rule in H.261.

FIG. 7 is a diagram illustrating transmission and reception of image data in the ring multipoint video conference system.

FIG. 8 is a block diagram of a ring multipoint videophone / conference terminal.

FIG. 9 is a diagram illustrating transmission and reception of image data in the ring multipoint video conference system.

FIG. 10 is a sequence diagram illustrating an operation of setting an image transmission cycle.

FIG. 11 is a diagram illustrating an outline of a configuration of an H.263 transmission frame in a CPM mode.

FIG. 12 is a diagram illustrating a relationship between a PSB identifier and a display position on a screen.

FIG. 13 is a block diagram of a ring multipoint videophone / conference terminal.

FIG. 14 is a diagram showing an example of a PSB identifier conversion rule.

FIG. 15 is a diagram illustrating transmission and reception of image data in the ring multipoint video conference system.

FIG. 16 is a block diagram of a ring multipoint videophone / conference terminal.

FIG. 17 is a diagram illustrating transmission and reception of image data in a ring multipoint video conference system.

FIG. 18 is a diagram illustrating transmission and reception of image data in the ring multipoint video conference system.

FIG. 19 is a diagram illustrating screen display on a terminal.

[Explanation of symbols]

1-5: videophone / videoconference terminal, 21: captured image of terminal D, 22: captured image of terminal C, 23: captured image of terminal B,
24: captured image of terminal A, 301: header section, 302: data section, 501, 1301: camera, 502, 1302: image encoding circuit, 50
3,1303 ... Reception-side transmission line, 504,1304 ... Reception signal conversion circuit,
505,1305… buffer memory, 506… PSC detection circuit, 507,80
7,1307,1607… Control circuit, 508,1308… Switch, 509,130
9: transmission side transmission line, 510, 1310 ... image decoding circuit, 511, 131
1 ... Display device, 701-705,901-905,1501-1505 ... Videophone / video conference terminal, 710-714,910-924 ... H.261 frame, 720-729,930-939,1520-1529 ... QCIF image, 812,
1612: Counter, 813, 1613: Register, 814, 1614: Comparison circuit, 815, 1615: Microphone, 816, 1616: Volume meter, 1101
... PSC, 1102 ... PSB identifier, 1103 ... QCIF image data, 1306
… PSC / PSB identifier detection circuit.

Claims (9)

[Claims] 1. A multipoint videophone / videoconference system in which a plurality of terminals are connected in a ring by a line to perform communication, wherein the plurality of terminals include one chair terminal and other participating terminals, Each of the terminals includes a speaker detection unit that detects whether the user of the own terminal is speaking or not, an analysis unit that analyzes control information sent via the line, A control unit for controlling the transmission of the image data received from the terminal on the upstream side and the image data generated by the own terminal to the terminal on the downstream side via the line, and each of the participating terminals has The result detected by the speaker detection unit is transmitted to the chair terminal.The chair terminal analyzes the detection result, determines the speaker, transmits control information to each of the participating terminals, and receives the control information. Was Participating terminal, the multipoint video telephone / teleconference system, characterized in that on the basis of the control information, controls a transmission amount of the image data generated by their own terminal. 2. A communication method for conducting a multipoint videophone / videoconference by connecting a plurality of terminals in a ring, wherein the plurality of terminals comprises one chair terminal and other participating terminals, Each of the participating terminals detects whether the user of the own terminal is speaking and transmits the detection result to the chair terminal, and the chair terminal analyzes the detection result to determine the speaker Transmitting control information to each of the participating terminals, and each participating terminal receiving the control information controls the transmission amount of image data generated by its own terminal based on the control information. Communication method to be used. 3. A multipoint videophone / videoconference terminal connected in a ring form by a plurality of lines, comprising: an analysis unit for analyzing control information sent via the line; A control unit for controlling transmission of image data received from the terminal and image data generated by the own terminal to a downstream terminal via the line, the control unit includes: A multipoint videophone / videoconference terminal that controls the transmission amount of image data generated by its own terminal based on the terminal. 4. A multipoint videophone / videoconference system in which a plurality of terminals are connected in a ring by a line, and each of the terminals simultaneously displays a plurality of image data transmitted from other terminals on a display screen. The plurality of terminals include one chair terminal and other participating terminals, wherein each of the terminals is a speaker detection unit that detects whether a user of his own terminal is speaking. An analysis unit for analyzing control information sent via the line, and image data received from the terminal on the upstream side via the line and image data generated by the terminal of the own device on the downstream side via the line And a control unit for controlling transmission to the terminal. Each of the participating terminals transmits a result detected by the speaker detecting unit to the chair terminal, and the chair terminal analyzes the detection result and makes a speech. Person At the same time, control information is transmitted to each of the participating terminals so as to increase the number of frames of image data generated and transmitted at the speaker's terminal, and each participating terminal receiving the control information transmits the control information to the participating terminal. On the display screen of each terminal, the image generated by the speaker's terminal is higher than the image generated by the other terminal on the display screen of each terminal. A multipoint videophone / videoconference system characterized by being displayed in frequency. 5. A multipoint videophone / videoconference in which a plurality of terminals are connected in a ring and each of the terminals simultaneously displays a plurality of image data transmitted from other terminals on a display screen. In the communication method, the plurality of terminals include one chair terminal and other participating terminals, and each of the participating terminals determines whether or not a user of the own terminal is speaking or not by the chair terminal. The chair terminal analyzes the detection result to determine the speaker, and controls each of the participating terminals to increase the number of frames of image data generated and transmitted by the speaker's terminal. Each participating terminal that has received the control information controls the transmission amount of image data generated by its own terminal based on the control information, and the display screen of each terminal displays the speaker's Terminal Communication method characterized in that the generated image is displayed at a higher frame frequency than the image generated by the other terminals. 6. A multipoint videophone / videoconference terminal which is connected in a ring shape by a line and simultaneously displays a plurality of image data transmitted from another terminal on a display screen. An analysis unit for analyzing the received control information, and a control for transmitting image data received from an upstream terminal via the line and image data generated by its own terminal to a downstream terminal via the line. The control unit controls the transmission amount of image data generated by its own terminal based on the control information, and on the display screen, generated by the speaker's terminal A multipoint videophone / videoconference terminal wherein image data is displayed at a higher frame frequency than an image generated by another terminal. 7. A multi-point videophone / videoconference system in which a plurality of terminals are connected in a ring via a line to perform communication, wherein a continuous presence of ITU-T H.263 is used as an image data encoding method. Multipoint mode (Conti
H.263 frame based on the H.263 is used for synchronization PSC (Pict
ure start code) and PSB (Picture
(Sub Bitstream) identifier and image data.Each of the above terminals includes a buffer memory for storing the H.263 frame received from the upstream terminal via the above line, and is included in the received H.263 frame. A PSC / PSB identifier detection unit that detects a PSC and PSB identifier to be detected, a camera, an image encoding unit that encodes an image signal captured by the camera, and a value of the PSB identifier detected by the PSC / PSB identifier detection unit. If the image data received and stored in the buffer memory is image data encoded and transmitted by one terminal downstream of its own terminal, the image data is deleted and encoded by the other terminals. If the image data is transmitted and transmitted, the image data is transmitted to the terminal on the downstream side of the own device via the line, and further, the image data encoded by the image signal Ring multipoint video telephone / teleconference system characterized by having an image data and a control unit for controlling so as to be transmitted to the downstream side of the terminal through the line. 8. A communication method for performing a videophone / videoconference between multiple points by connecting a plurality of terminals in a ring via a line, wherein a continuous method of ITU-T H.263 is used as an image data encoding method. Ass Presence Multipoint Mode (Conti
H.263 frame based on the H.263 is used for synchronization PSC (Picture Start C
ode) and a PSB identifier (Picture Sub
Bitstream identifier) and image data, and each of the plurality of terminals is H.263 sent from the terminal on the upstream side via the line.
Receives the frame, detects the PSB identifier included in the received H.263 frame, and, based on the value of the detected PSB identifier, converts the image data included in the received H.263 frame to one downstream of its own terminal. If the image data is encoded and transmitted by the terminal, the image data is deleted.If the image data is encoded and transmitted by another terminal, the image data is deleted by itself through the above line. To the downstream terminal of
Furthermore, a communication method characterized by transmitting image data captured and encoded by a camera of its own terminal to a downstream terminal via the line. 9. A multipoint videophone / videoconference terminal connected in a ring by a plurality of lines using a continuous presence multipoint mode of ITU-T H.263 as an encoding method of image data. , PSC (Picture Start Code) for synchronization and PSB identifier (Picture Sub Bitstream identifier) for identifying the terminal
And an image data and an H.263 frame transmitted and received via the above-mentioned line, and a buffer memory for storing the H.263 frame received from a terminal on the upstream side of the above-mentioned line. A PSC / PSB identifier detector for detecting the included PSC and PSB identifiers, a camera, an image encoder for encoding an image signal captured by the camera, and a value of the PSB identifier detected by the PSC / PSB identifier detector. If the image data received and stored in the buffer memory is image data that has been encoded and transmitted by one terminal downstream of its own terminal, the image data is deleted, and the If the image data is encoded and transmitted, the image data is transmitted to the terminal on its own downstream side via the line, and further, the terminal of its own terminal encoded by the encoding unit. A control unit for controlling transmission of image data to a downstream terminal via the line.