Multipoint teleconference system employing communication channels set in ring configuration

Claims

What is claimed is:

1. In a multipoint video telephone/teleconference system having a plurality of video telephone/teleconference terminals which are connected to digital communication channels and which transmit and receive communication frame containing video telephonic/teleconferential data, which includes video data, through the connected digital communication channels, said multipoint teleconference system comprising:

wherein said digital communication channels connect said plurality of video telephone/teleconference terminals in a ring configuration; and

wherein each of said video telephone/teleconference terminals comprises:

generation means for generating the video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals, said telephonic/teleconferential data including said video data,

resumption means for resuming said video data contained in said communication frame received from the video telephone/teleconference terminal at an upper stream position of a loop with respect to transfer of said communication frame,

relay means for transmitting the received communication frame to the video telephone/teleconference terminal at a lower stream position of said loop so that said communication frame may revolve around said loop, said loop being formed of said digital communication channels which connect said plurality of video telephone/teleconference terminals to one another,

cancellation means for cancelling the video data which was entered into said communication frame by a video telephone/teleconference terminal itself and which has revolved around said loop, from within said communication frame which is to be relayed by said relay means, and

transmission means for entering the generated video data into an unused area of said communication frame which is to be relayed by said relay means, thereby sending said generated video data to said other video telephone/teleconference terminals which lie on said loop.

2. In a multipoint teleconference system having an ISDN which transfers a communication frame around a set channel, and a plurality of video telephone/teleconference terminals which conform to CCITT Recommendation H.320 and which are connected to the ISDN, said multipoint teleconference system comprising:

wherein said communication frame contains video telephonic/teleconferential data including video data;

wherein at least one of said plurality of video telephone/teleconference terminals comprises:

channel setting means for setting channels between the adjacent video telephone/teleconference terminals in said ISDN so that said plurality of video telephone/teleconference terminals may be connected in a ring configuration; and

wherein each of said video telephone/teleconference terminals comprises:

generation means for generating said video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals, said telephonic/teleconferential data including the video data,

resumption means for resuming said video data contained in the frame received from the video telephone/teleconference terminal at an upper stream position of a loop with respect to transfer of said communication frame,

relay means for relaying the received communication frame to the video telephone/teleconference terminal at a lower stream position of said loop so that said communication frame may revolve around said loop, said loop being formed of said plurality of video telephone/teleconference terminals and said channels set by said channel setting means so as to connect said video telephone/teleconference terminals,

cancellation means for canceling the video telephonic/teleconferential data which was entered into said communication frame by a video telephone/teleconference terminal itself and which has revolved around said loop, from within said communication frame which is to be relayed by said relay means, and

transmission means for entering the generated video data into an unused area of said communication frame which is to be relayed by said relay means, thereby transferring said generated video data to said other video telephone/teleconference terminals which lie on said loop.

3. A multipoint teleconference system as defined in claim 2, wherein:

said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame"), a frame stipulated in CCITT Recommendation H. 261 (herein below, termed "H. 261 frame") is prepared in said H. 221 frame, and groups of blocks (GOB's) included in said H. 261 frame are respectively allotted to the individual video telephone/teleconference terminals, said GOB's each being a plurality of blocks into which the data area for H. 261 frames are divided;

said resumption means resumes said video data contained in the plurality of GOB's of said H. 261 frame prepared in the received H. 221 frame, into a picture of one picture frame so as to present a display output;

said cancellation means cancels video data which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself and which has revolved around said loop, from at least one GOB allotted to said video telephone/teleconference terminal itself; and

said transmission means enters the generated video data into at least one GOB allotted to said video telephone/teleconference terminal itself, among said GOB's of said H. 261 frame prepared in said H. 221 frame.

4. A multipoint teleconference system as defined in claim 3, wherein:

said plurality of GOB's included in said H. 261 frame are divided into N (being a natural number) groups, which are respectively allotted to the N video telephone/teleconference terminals; and

said resumption means of each of said video telephone/teleconference terminals resumes the video data contained in said H. 261 frame, in respective areas of one picture frame corresponding to the GOB's having contained said video data, so as to present said display output.

5. A multipoint teleconference system as defined in claim 2, wherein:

said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame"), and a frame stipulated in CCITT Recommendation H. 261 (herein below, termed "H. 261 frame") is prepared in said H. 221 frame;

said each video telephone/teleconference terminal further comprises audio data resumption means for resuming audio data into speech so as to emit the speech;

said generation means generates the video telephonic/teleconferential data including audio data;

said cancellation means cancels an audio data component which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself and which has revolved around said loop, from audio data contained in said H. 261 frame of the received H. 221 frame;

said audio data resumption means resumes the audio data with said audio data component of said terminal itself cancelled by said cancellation means, into the speech so as to emit said speech; and

said transmission means enters new audio data into said H. 261 frame of the H. 221 frame to be relayed by said relay means, instead of said audio data contained in said H. 261 frame of said H. 221 frame received by said relay means, said new audio data being obtained in such a way that said audio data generated by said generation means is added to said audio data, with said audio data component of said terminal itself cancelled by said cancellation means.

6. In a multipoint teleconference system having an ISDN which transfers a communication frame around a set channel, and a plurality of video telephone/teleconference terminals which conform to CCITT Recommendation H.320 and which are connected to the ISDN, said multipoint teleconference system comprising;

wherein at least one of said plurality of video telephone/teleconference terminals comprises:

channel setting means for setting channels between the adjacent video telephone/teleconference terminals in the ISDN so that said plurality of video telephone/teleconference terminals may be connected in a ring configuration;

wherein each of said video telephone/teleconference terminals comprises:

generation means for generating said video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals,

relay means for relaying the communication frame received from the video telephone/teleconference terminal at an upper stream position of a loop to the video telephone/teleconference terminal at a lower stream position of said loop so that said communication frame may revolve around said loop, said loop being formed of said plurality of video telephone/teleconference terminals and said channels set by said channel setting means so as to connect said video telephone/teleconference terminals,

transmission means for entering the generated video telephonic/teleconferential data into said communication frame which is to be relayed by said relay means, thereby transferring said generated video telephonic/teleconferential data to said other video telephone/teleconference terminals which lie on said loop, and

cancellation means for canceling the video telephonic/teleconferential data which was entered into said communication frame by said transmission means of a video telephone/teleconference terminal itself before and which has revolved around said loop, from within said communication frame which is to be relayed by said relay means;

wherein said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame"), a frame stipulated in CCITT Recommendation H. 261 (herein below, termed "H. 261 frame") is prepared in said H. 221 frame, and groups of blocks (GOB's) included in said H. 261 frame are respectively allotted to the individual video telephone/teleconference terminals, said GOB's each being a plurality of blocks into which the data area for H. 261 frames are divided;

wherein each of said video telephone/teleconference terminals further comprises resumption means for resuming video data contained in the plurality of GOB's of said H. 261 frame prepared in the received H. 221 frame, into a picture of one picture frame so as to present a display output;

wherein said cancellation means cancels video data which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself and which has revolved around said loop, from at least one GOB allotted to said video telephone/teleconference terminal itself; and

wherein said transmission means enters the generated video data into at least one GOB allotted to said video telephone/teleconference terminal itself, among said GOB's of said H. 261 frame prepared in said H. 221 frame.

7. A multipoint teleconference system as defined in claim 6, wherein:

wherein said plurality of GOB's included in said H. 261 frame are divided into N (being a natural number) groups, which are respectively allotted to the N video telephone/teleconference terminals; and

wherein said resumption means of each of said video telephone/teleconference terminals resumes the video data contained in said H. 261 frame, in respective areas of one picture frame corresponding to the GOB's having contained said video data, so as to present said display output.

8. In a multipoint teleconference system having an ISDN which transfers a communication frame around a set channel, and a plurality of video telephone/teleconference terminals which conform to CCITT Recommendation H.320 and which are connected to the ISDN, said multipoint teleconference system comprising:

wherein at least one of said plurality of video telephone/teleconference terminals comprises:

channel setting means for setting channels between the adjacent video telephone/teleconference terminals in the ISDN so that said plurality of video telephone/teleconference terminals may be connected in a ring configurations;

wherein each of said video telephone/teleconference terminals comprises:

generation means for generating said video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals,

relay means for relaying the communication frame received from the video telephone/teleconference terminal at an upper stream position of a loop to the video telephone/teleconference terminal at a lower stream position of said loop so that said communication frame may revolve around said loop, said loop being formed of said plurality of video telephone/teleconference terminals and said channels set by said channel setting means so as to connect said video telephone/teleconference terminals,

transmission means for entering the generated video telephonic/teleconferential data into said communication frame which is to be relayed by said relay means, thereby transferring said generated video telephonic/teleconferential data to said other video telephone/teleconference terminals which lie on said loop, and

cancellation means for canceling the video telephonic/teleconferential data which was entered into said communication frame by said transmission means of a video telephone/teleconference terminal itself before and which has revolved around said loop, from within said communication frame which is to be relayed by said relay means;

wherein said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame"), and a frame stipulated in CCITT Recommendation H. 261 (herein below, termed "H. 261 frame") is prepared in said H. 221 frame;

wherein each of said video telephone/teleconference terminals further comprises audio data resumption means for resuming audio data into speech so as to emit the speech;

wherein said generation means generates the video telephonic/teleconferential data including audio data;

wherein said cancellation means cancels an audio data component which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself and which has revolved around said loop, from audio data contained in said H. 261 frame of the received H. 221 frame;

wherein said audio data resumption means resumes the audio data with said audio data component of said terminal itself cancelled by said cancellation means, into the speech so as to emit said speech; and

wherein said transmission means enters new audio data into said H. 261 frame of the H. 221 frame to be relayed by said relay means, instead of said audio data contained in said H. 261 frame of said H. 221 frame received by said relay means, said new audio data being obtained in such a way that said audio data generated by said generation means is added to said audio data with said audio data component of said terminal itself cancelled by said cancellation means.

9. A video telephone/teleconference terminal connectable with a plurality of digital communication channels, comprising:

generation means for generating video telephonic/teleconferential data which is to be sent to a plurality of other video telephone/teleconference terminals, said telephonic/teleconferential data including video data;

resumption means for resuming said video data contained in a communication frame received from any of a plurality of set channels;

relay means for relaying the received communication frame to another of said set channels;

cancellation means for cancelling the video data which was entered into said communication frame by said video telephone/teleconference terminal itself before the reception of said communication frame, from within said communication frame which is to be relayed by said relay means; and

transmission means for entering the generated video data into an unused area of said communication frame which is to be relayed by said relay means.

10. A video telephone/teleconference terminal connectible with an ISDN, comprising:

channel setting means for setting a plurality of channels between said video telephone/teleconference terminal itself and a plurality of other video telephone/teleconference terminals in the ISDN;

generation means for generating video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals, said telephonic/teleconferential data including video data;

resumption means for resuming said video data contained in a communication frame received from any of the set channels;

relay means for relaying the received communication frame to another of the set channels;

cancellation means for canceling the video telephonic/teleconferential data which was entered into said communication frame by said video telephone/teleconference terminal itself before the reception of said communication frame, from within said communication frame which is to be relayed by said relay means; and

transmission means for entering the generated video data into an unused area of said communication frame which is to be relayed by said relay means.

11. A video telephone/teleconference terminal as defined in claim 10, wherein:

said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame");

said resumption means resumes said video data into a picture of one picture frame so as to present a display output, said video data being contained in a plurality of groups of blocks (GOB's) of a frame stipulated in CCITT Recommendation H. 261 (hereinbelow, termed "H. 261 frame") and prepared in the received H. 221 frame, said GOB's each being a plurality of blocks into which the data area for H. 261 frames are divided;

said transmission means enters the generated video data into at least one GOB allotted to said video telephone/teleconference terminal itself, among said plurality of GOB's of said H. 261 frame prepared in said H. 221 frame; and

said cancellation means cancels video data which was entered into said H. 261 frame by, said transmission means of said video telephone/teleconference terminal itself before the reception of said H. 221 frame to be relayed, from at least one GOB allotted to said video telephone/teleconference terminal itself.

12. A video telephone/teleconference terminal as defined in claim 10, wherein:

said communication frame is a frame stipulated n CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame"), and a frame stipulated in CCITT Recommendation H. 261 (hereinbelow, termed "H. 261 frame") is prepared in said H. 221 frame;

said video telephone/teleconference terminal comprises audio data resumption means for resuming audio data into speech so as to emit the speech;

said generation means generates the video telephonic/teleconferential data including audio data;

said cancellation means cancels an audio data component which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself before the reception of said H. 221 frame, from audio data contained in said H. 261 frame of the received H. 221 frame;

said audio data resumption means resumes the audio data with said audio data component of said terminal itself cancelled by said cancellation means, into speech so as to emit said speech; and

said transmission means enters new audio data into said H. 261 frame to be relayed by said relay means, instead of said audio data contained in said H. 261 frame of said H. 221 frame received by said relay means, said new audio data being obtained in such a way that said audio data generated by said generation means is added to said audio data with said audio data component of said terminal itself canceled by said cancellation means.

13. A video telephone/teleconference terminal connectible with an ISDN, comprising:

channel setting means for setting a plurality of channels between said video telephone/teleconference terminal itself and a plurality of other video telephone/teleconference terminals in the ISDN;

generation means for generating video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals;

relay means for relaying a communication frame received from any of the set channels to another of the set channels;

transmission means for entering the generated video telephonic/teleconferential data into said communication frame which is to be relayed by said relay means; and

cancellation means for canceling the video telephonic/teleconferential data which was entered into said communication frame by said transmission means of said video telephone/teleconference terminal itself before the reception of said communication frame, from within said communication frame which is to be relayed by said relay means;

wherein said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow termed "H. 221 frame");

wherein said video telephone/teleconference terminal comprises resumption means for resuming video data into a picture of one picture frame so as to present a display output, said video data being contained in a plurality of groups of blocks (GOB's) of a frame stipulated in CCITT Recommendation H. 261 (hereinbelow, termed "H. 261 frame") and prepared in the received H. 221 frame., said GOB's each being a plurality of blocks into which the data area for H. 261 frames are divided;

wherein said transmission means enters the generated video data into at least one GOB allotted to said video telephone/teleconference terminal itself, among said plurality of GOB's of said H. 261 frame prepared in said H. 221 frame; and

wherein said cancellation means cancels video data which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself before the reception of said H. 221 frame to be relayed, from at least one GOB allotted to said video telephone/teleconference terminal itself.

14. A video telephone/teleconference terminal connectible with an ISDN, comprising:

channel setting means for setting a plurality of channels between said video telephone/teleconference terminal itself and a plurality of other video telephone/teleconference terminals in the ISDN;

generation means for generating video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals;

relay means for relaying a communication frame received from any of the set channels to another of the set channels;

transmission means for entering the generated video telephonic/teleconferential data into said communication frame which is to be relayed by said relay means; and

cancellation means for canceling the video telephonic/teleconferential data which was entered into said communication frame by said transmission means of said video telephone/teleconference terminal itself before the reception of said communication frame, from within said communication frame which is to be relayed by said relay means;

wherein said communication frame is a frame stipulated in CCITT Recommendation H. 221 (hereinbelow, termed "H. 221 frame"), and a frame stipulated in CCITT Recommendation H. 261 (hereinbelow, termed "H. 261 frame") is prepared in said H. 221 frame;

wherein said video telephone/teleconference terminal comprises audio data resumption means for resuming audio data into speech so as to emit the speech;

wherein said generation means generates the video telephonic/teleconferential data including audio data;

wherein said cancellation means cancels an audio data component which was entered into said H. 261 frame by said transmission means of said video telephone/teleconference terminal itself before the reception of said H. 221 frame, from audio data contained in said H. 261 frame of the received H. 221 frame;

wherein said audio data resumption means resumes the audio data with said audio data component of said terminal itself cancelled by said cancellation means, into speech so as to emit said speech; and

wherein said transmission means enters new audio data into said H. 261 frame to be relayed by said relay means, instead of said audio data contained in said H. 261 frame of said H. 221 frame received by said relay means, said new audio data being obtained in such a way that said audio data generated by said generation means is added to said audio data with said audio data component of said terminal itself canceled by said cancellation means.

15. In multipoint video telephone/teleconference system having a plurality of video telephone/teleconference terminals which are connected to digital communication channels and which transmit and receive communication frame containing video telephonic/teleconferential data which includes video data, through the connected digital communication channels, said multipoint teleconference system comprising:

wherein said digital communication channels connect said plurality of video telephone/teleconference terminals in a ring configuration;

wherein said communication frame includes a plurality of data blocks each of which is divided from a data area of said communication frame;

wherein said data blocks are respectively allotted to the individual video telephone/teleconference terminals; and

wherein each of said video telephone/teleconference terminals comprises:

generation means for generating the video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals, said telephonic/teleconferential data including said video data,

resumption means for resuming said video data contained in the allotted data block of the frame received from the video telephone/teleconference terminal at an upper stream position of a loop with respect to transfer of said communication frame,

relay means for transmitting the received communication frame to the video telephone/teleconference terminal at a lower stream position of said loop so that said communication frame may revolve around said loop, said loop being formed of said digital communication channels which connect said plurality of video telephone/teleconference terminals to one another,

cancellation means for cancelling the video data which was entered into the allotted data block of said communication frame by a video telephone/teleconference terminal itself and which has revolved around said loop, from within said communication frame which is to be relayed by said relay means, and

transmission means for entering the generated video data into the allotted block of said communication frame which is to be relayed by said relay means, thereby sending said generated video data to said other video telephone/teleconference terminals which lie on said loop.

16. A video telephone/teleconference terminal connectible with a plurality of digital communication channels; wherein:

said digital communication channels transmit communication frame;

said communication frame includes a plurality of data blocks each of which is divided from a data area of said communication frame;

said data blocks are respectively allotted to individual video telephone/teleconference terminals; and

said video telephone/teleconference terminal includes:

generation means for generating video telephonic/teleconferential data which is to be sent to a plurality of other video telephone/teleconference terminals, said telephonic/teleconferential data including video data,

resumption means for resuming said video data contained in said communication frame received from any of a plurality of channels,

relay means for relaying the received communication frame to another of said channels,

cancellation means for canceling the video data which was entered into the allotted data block of said communication frame by said video telephone/teleconference terminal itself the reception of said communication frames, from within said communication frame which is to be relayed by said relay means, and

transmission means for entering the generated video data into the allotted data block of said communication frame which is to be relayed by said relay means.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a teleconference/telephone terminal. More particularly, it relates to a multipoint teleconference system wherein a conversation or a conference is had by connecting teleconference/telephone terminals at three or more multiple points or spots.

2. Description of the Related Art

As a multipoint teleconference system in the prior art, there has been known one proposed in the CCITT (International Telegraph and Telephone Consultative Committee) Recommendation H. 320.

In order to realize a multipoint teleconference, the multipoint teleconference system is equipped with an MCU in addition to teleconference/telephone terminals (hereinbelow, simply termed "ends"). Herein, the multipoint teleconference is held in such a way that all the ends to attend this teleconference are connected with the MCU, and that the MCU controls communications among multiple points.

Since the prior-art multipoint teleconference system realizes the multipoint teleconference as stated above, it poses the following problems:

(1) The number of ends which can attend the multipoint teleconference, and the transmission speed of the communications are limited by the admitting capacity of the MCU.

(2) Even in the state in which all the ends of the pertinent group can attend the multipoint teleconference, this teleconference cannot be held when the MCU is not operating or when all available MCU's are busy or occupied for the multipoint teleconferences of other groups.

(3) In a case where the MCU lies at a point distant from the ends which attend the multipoint teleconference, the communications become expensive,

SUMMARY OF THE INVENTION

The present invention therefore has for its object to provide a multipoint teleconference system in which a multipoint teleconference can be realized by only the ends attending this teleconference, without requiring any MCU.

The present invention consists of a multipoint video telephone/teleconference system having a plurality of video telephone/teleconference terminals which are connected to digital communication channels and which transmit and receive communication frames containing video telephonic/teleconferential data, through the connected digital communication channels and has the following characteristics.

The digital communication channels connect the plurality of video telephone/teleconference terminals in a ring configuration. Each video telephone/teleconference terminal comprises a generation device for generating the video telephonic/teleconferential data which is to be sent to the other video telephone/teleconference terminals, a relay device for transmitting the communication frame received from the video telephone/teleconference terminal at an upper stream position of a loop to the video telephone/teleconference terminal at a lower stream position of the loop so that the communication frames may revolve around the loop which is formed of the digital communication channels which connect the plurality of video telephone/teleconference terminals to one another, a transmission device for entering the generated video telephonic/teleconferential data into the communication frame which is to be relayed by the relay device, thereby sending the generated video telephonic/teleconferential data to the other video telephone/teleconference terminals which lie on the loop, and a cancellation device for canceling the video telephonic/teleconferential data which was entered into the communication frame by the transmission device of the video telephone/teleconference terminal itself before and which has revolved around the loop, from within the communication frame which is to be relayed by the relay device.

According to the multipoint teleconference system of the present invention, each video telephone/teleconference terminal causes the communication frame to revolve around the loop constituted by the digital communication channels which connect the plurality of video telephone/teleconference terminals to one another. In addition, each terminal enters the generated video telephonic/teleconferential data into the communication frame which is to be relayed, thereby sending the generated data to the other video telephone/teleconference terminals on the loop. Besides, each terminal cancels the video telephonic/teleconferential data transmitted by itself before, from within the communication frame having revolved around the loop, thereby avoiding the double transmission of the video telephonic/teleconferential data and the stocking of such unnecessary video telephonic/teleconferential data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the architecture of a multipoint teleconference system according to an embodiment of the present invention;

FIG. 2 is a block diagram showing the construction of a multipoint video telephone/teleconference terminal in the embodiment of the present invention;

FIGS. 3(a) and 3(b) are explanatory views showing the operation of the multipoint teleconference system of the embodiment;

FIG. 4 is an explanatory view showing the operation of the multipoint teleconference system;

FIG. 5 is an explanatory view showing the operation of the multipoint teleconference system;

FIG. 6 is an explanatory diagram showing the format of a frame stipulated in the CCITT Recommendation H. 221;

FIGS. 7(a) thru 7(d) are diagrams for explaining a frame stipulated in the CCITT Recommendation H. 261, and examples of use of the frame in the embodiment of the present invention;

FIGS. 8(a) thru 8(c) are diagrams for explaining the relationships in the embodiment between GOB's stipulated in the CCITT Recommendation H. 261 and video data;

FIG. 9 is a block diagram showing the first example of construction of a video path controller in the embodiment;

FIG. 10 is a block diagram showing the construction of a video SW/clock change-over control in the embodiment;

FIG. 11 is a block diagram showing the construction of an audio processor in the embodiment;

FIG. 12 is a block diagram showing an audio mean level discriminator in the embodiment;

FIG. 13 is a block diagram showing the second example of construction of the video path controller in the embodiment;

FIGS. 14(a) and 14(b) are explanatory diagrams showing schemes for transmitting control information in the embodiment;

FIGS. 15(a) and 15(b) are explanatory diagrams showing schemes for transmitting commands and data in the embodiment;

FIG. 16 is a block diagram showing the construction of the control system of the chairperson terminal in the embodiment;

FIG. 17 is an explanatory diagram showing an example of display of the control information in the chairperson terminal;

FIG. 18 is an explanatory diagram showing another example of display of the control information in the chairperson terminal;

FIG. 19 is a block diagram showing the construction of the control system of the terminal other than the chairperson terminal, in the embodiment;

FIG. 20 is a block diagram showing the first example of arrangement of a video decoder and peripheral constituents in the embodiment;

FIG. 21 is a block diagram showing the second example of arrangement of the video decoder and peripheral constituents in the embodiment;

FIG. 22 is an explanatory diagram showing a frame format which employs an additional channel stipulated in the CCITT Recommendation H. 221; and

FIG. 23 is a schematic diagram showing a multipoint teleconference system according the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, an embodiment of a multipoint teleconference system according to the present invention will be described.

First, FIG. 1 illustrates the architecture of the multipoint teleconference system in this embodiment, under the assumption that the number of ends or terminals which attend a multipoint teleconference is four.

Referring to the figure, numerals 1, 2, 3 and 4 indicate the ends, and numeral 5 indicates a digital communications network. Here in this embodiment, the end A at numeral 1 is a chairperson end which takes charge of the functions of the chairperson of the multipoint teleconference. Incidentally, in this embodiment, an ISDN stipulated in the CCITT Recommendations I-Series is assumed as the digital communications network 5. Also, for the brevity of the description, it is supposed that each of the ends is connected with the ISDN by a fundamental interface of 2B+D.

In this embodiment, the individual ends attending the multipoint teleconference are connected in the shape of a loop. More specifically, as shown in the FIG. 1, the end-A 1 is connected to the end-D 4 and the end-B 2 by separate B channels, the end-B 2 to the end-A 1 and the end-C 3, the end-C 3 to the end-B 2 and end-D 4, and the end-D 4 to the end-C 3 and the end-A 1.

Next, FIG. 2 illustrates the construction of each end in this embodiment.

Referring to the FIG., the end includes a video input/output device 200 such as a CRT or video camera, a video codec 201 which codes/decodes video information, a video path controller 202 which multiplexes/demultiplexes video information, an audio input/output device 210 such as a loudspeaker or microphone, an audio codec 211 which codes/decodes audio information, an audio processor 212 which processes audio information, a conference controller 220 which performs the controls of various parts attendant upon the multipoint teleconference, a telematic unit 230, a system controller 240 which controls the entire end, an end/network signal controller 250 which performs communication controls such as a call control between the end and the digital communications network 5, an MUX/DMUX (multiplexor/demultiplexor) 260 which performs the framing process of H. 221 frames to be described later, and a network interface unit 270 which takes charge of the interface of a lower layer with the network 5. In addition, the system controller 240 is furnished with an end/end signal controller which processes control data and notification data sent to the pertinent end or to be sent to the other ends.

Among these constituents, the video I/O device 200, video codec 201, audio I/O device 210, audio codec 211, telematic unit 230, system controller 240, end/network signal controller 250, MUX/DMUX 260, network interface unit 270 and end/end signal controller have the same details as stipulated in CCITT Recommendations H. 320, H. 221, H. 242 and H. 261, and their operations in ordinary one-to-one communications are also as stipulated in the above recommendations. In the ensuing description, therefore, those points of difference from the ordinary one-to-one communications which arise in the execution of the multipoint teleconference will be chiefly elucidated.

Now, the operation of the multipoint teleconference system of this embodiment will be outlined.

FIGS. 3(a) and 3(b), FIG. 4, and FIG. 5 illustrate the situations of video outputs from the video I/O devices 200 of the respective ends and audio outputs from the audio I/O devices 210 as to the case where the four ends A, B, C and D are holding the multipoint teleconference.

In an example depicted in FIGS. 3(a) and 3(b), all the ends present video information transmitted from one of the ends, as display outputs. FIG. 3(a) shows the state in which the video information transmitted from the end B is presented as the display outputs by all the ends A, B, C and D. Usually, the source end of the video information is the end which is used by a speaker in the conference. This source end is determined in compliance with an instruction from the chairperson end, or it is automatically determined to be the end which is transmitting the audio information of the highest level. FIG. 3(b) shows the state in which the source end of the video information has changed-over from the end B to the end C.

On the other hand, the audio outputs of the respective ends do not depend upon the displayed video information, but they are produced by mixing all the items of audio information received from the other ends attending the conference. Herein, the audio information transmitted by the pertinent end itself is prevented from being output in the pertinent end, by the use of an echo canceling technique.

More specifically, in the example depicted in FIGS. 3(a) and 3(b), the audio information items transmitted from the ends B, C and D are output by the end A; those transmitted from the ends A, C and D are output by the end B; those transmitted from the ends A, B and D are output by the end C; and those transmitted from the ends A, B and C are output by the end D.

In an example depicted in FIG. 4, all the ends present two items of video information transmitted from two different ends, as display outputs. FIG. 4 sho