AU677052B2

AU677052B2 - Videoconference system

Info

Publication number: AU677052B2
Application number: AU64792/94A
Authority: AU
Inventors: Andreas Buchelt; Lothar George
Original assignee: Alcatel NV
Current assignee: Alcatel Lucent NV
Priority date: 1993-06-30
Filing date: 1994-06-20
Publication date: 1997-04-10
Anticipated expiration: 2014-06-20
Also published as: EP0632658A3; EP0632658A2; AU6479294A; DE4321674A1

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

S

*5

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: o r "VIDEOCONFERENCE SYSTEM" The following statement is a full description of this invention, including the best method of performing it known to us:- I- 2 This invention relates to a videoconference system with N subscriber terminals which are connected via a telecommunication network to a videoconference server and a subscriber terminal and a videoconference server for this videoconference system.

Such a videoconference system is known in which a videoconference server is connected to an exchange via interface circuits, like a normal subscriber. Furthermore, n subscriber terminals are connected to the exchange.

The exchange switches point-to-point channels between the subscriber terminals and the videoconference server, and all control commands which do not relate to the establishment or disconnection of such channels are exchanged in a transparent manner between the subscriber terminals and the videoconference server.

It is known that with such videoconference systems, from each subscriber terminal taking part in the videoconference, an amount of data is transmitted to the videoconference server which corresponds to a complete image.

In the known videoconference systems each participant can set the type of display on his screen, in particular the image size, of the other subscribers.

2O; That is, he can set up a mixed display in which, among other possibilities, one or more subscribers are simultaneously displayed as small images on the screen.

Such a small image corresponds to a coarsened display of the full image which is transmitted from the relevant subscriber terminal to the videoconference server, and which is converted to the coarsened display in the videoconference server before being transmitted from the videoconference server to the subscriber requiring the mixed display. In this case, the transmission of a static image of the subscriber takes place in the same way as that of the moving image.

It is an object of the present invention to describe a video- conference system which avoids unnecessarily large demands being placed on the transmission capacity of a telecommunication network.

According to the invention, there is provided a video conference system with n subscriber terminals which are connected via a telecommunication y" oo *o e

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*e *a *o II *e network to a videoconference server, wherein each of the n subscriber terminals can encode a moving image or a static image in at least two different ways which produce different amounts of data for the moving image or the static image, and wherein the videoconference server can receive and decode these, at least two, differently encoded moving images or static images of the relevant subscriber terminal, and that, depending on the type of display of the moving image or static image currently requested by the other subscriber terminals taking part in the videoconference, the moving image or the static image from each of the subscriber terminals is transmitted to the videoconference server.

An advantage of the solution according to the invention is that it provides a definite tariff saving for videoconference subscribers when the calculation of the tariff depends on the actual amount of data transmitted, In order that the invention may be readily understood, an embodiment thereof will now be described in relation to the accompanying drawings.

15 The drawing shows, simplified in the block diagram, the embodiment of a videoconference system according to the invention.

The embodiment shows a videoconference system VS with a subscriber terminal T which is connected to a videoconference server Z by means of a telecommunication network having an exchange VST.

20 The telecommunication network N can be any arbitrary telecommunication network and, in the present example, operates according to the well-known Asynchronous Transfer Mode (ATM). The exchange VST is consequently an ATM exchange such as is described, for example, in the article "Das ATM Koppelfeld von Alcatel und seine Eigenschaften" [The Alcatel ATM Switching Matrix and its Properties] by D. Boettle and U.A. Henrion, Elektrisches Nachrichtenwesen, Vol 64, Number 2/3, 1990. A number of additional subscribers are connected to the exchange VST and these are not discussed any further here as their construction corresponds to that of the subscriber terminal T. All connections to and from the exchange VST are bidirectional connections.

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Among other items, the subscriber terminal T consists of a first adaptor unit AT which, on the line side, adapts the signals arriving from the telecommunication network N to the subscriber terminal, and conversely, for further processing. It contains, among other items, a multiplexer/demultiplexer which, in particular, processes video, speech, control and signalling data. The processing of the speech is well-known and not significant for the invention and, therefore, will not be discussed any further in the present design example.

The first adaptor unit AT is connected to a first control unit ST, a first SWT1 and a second SWT2 signal converter, which, in turn, are connected to a first image processing unit BVT.

A camera, a video screen, a loudspeaker and a microphone are connected S: to the first image processing unit BVT, but these are not shown in the diagram.

The videoconference server Z, among other items, consists of a second adaptor unit AZ which, on the line side, adapts the signals arriving from the o..1 telecommunication network N to the videoconference server Z, and conversely, for further processing. Among other items, it contains, a multiplexer/ demultiplexer which, in particular, processes video, speech, control and signalling data. The second adaptor unit AZ is connected to the second control unit SZ and a switching matrix SM. The switching matrix SM is connected to the second control unit SZ, and to a first SZW1 and a second SZW2 signal converter which are each also connected to the second control unit SZ a second image processing unit BVZ. The second control unit SZ is also connected to the second image processing unit BVZ. All the connections described, within the S. video- conference server Z and within the subscriber terminal T, are bidirectional connections.

During the videoconference with at least three subscribers, an image is transmitted from each of the three associated subscribers to the videoconference server Z. The image can be a moving image as well as a static image. In order to ensure that each participant can capture the current videoconference situation optimally, one of the participants is displayed on his video screen as a full image and the others as a small image, or not at all. The small image then corresponds to a smaller amount of information, and therefore a smaller amount of data, than the full image.

For the subscriber terminal T this means that the image captured by the camera connected to the first image processing unit BVT is converted to a form suitable for transmission over the telecommunication network N, by either the first SWT1 or the second SWT2 signal converter. The first SWT1 and the second SWT2 signal converter each operate according to suitable algorithms which carry out the encoding of the video signal into a line signal, a subsidiary operation which is not relevant to the invention. These algorithms can, for example, be the compression algorithms recommended by the ISO Motion Picture Expert Group (MPEG). SWT1 encodes the image taken by the camera directly as a full image, while SWT2 converts the image taken by the camera to a small image before encoding it as the line signal. The small image then S represents a minimum required amount of video data. In which of these two i possible forms of display the video data of the subscriber terminal T is transmitted to the videoconference server Z depends on which form the other two subscribers request. If the two other subscriber terminals request a small image from the subscriber terminal T, the video data from subscriber terminal T encoded by the second signal converter SWT2 is transmitted to the videoconference server Z. If at least one of the other subscriber terminals requests the full image from the subscriber terminal T, then the video data from subscriber terminal T encoded by the first signal converter SWT1 is transmitted to the videoconference server Z. Information about which form of display has just been requested by the other subscriber terminals is contained in the control S. data transmitted from the videoconference server Z to the subscriber terminal T.

The first control unit ST of subscriber terminal T determines, by means of internal control commands, that the video data of the requested form of display is correspondingly transmitted to the videoconference server Z via either SWT1 or SWT2.

In the videoconference server Z, the second control unit SZ affects the switching matrix SM in accordance with the control data in such a way that the video signal coming from the first signal converter SWT1 is conducted to the first signal converter SWZ1 of the videoconference server Z, and the video signal coming from the second signal converter SWT2 is conducted to the second signal converter SWZ2 of the videoconference server Z.

The first signal converter SWZ1 of the videoconference server Z operates according to the same algorithm as the first signal converter SWT1 of the subscriber terminal T, and the second signal converter SWZ of the videoconference server Z operates according to the same algorithm as the second signal converter SWT2 of the subscriber terminal T. The video signal corresponding to the full image, converted by SWZ1, or the video signal corresponding to a small image, converted by SWZ2, is applied to the second image processing unit BVZ. In the second image processing unit BVZ, the video signal is mixed, in the known manner, with the video signals transmitted from the other subscriber terminals to tne videoconference server Z so as to produce the form of display individually requested by each participant. This video signal i mixing can be carried out in a known manner. The individual video signal mixtures are then retransmitted to the respective subscriber terminals of the videoconference.

Although every participant in the videoconference can freely select the form of display of the other participants, usually the current speaker is displayed S: as a full image and the inactive participants as small images. A speech-detection unit SE is integrated into the second image processing unit BVZ to permit the detection of speech. This can operate in accordance with different known methods. One method, for example, consists of the evaluation of the strength of the sound signals of every subscriber terminal. That is, the speech-detection unit SE selects that participant as the speaker from whom the sound signal with the loudest amplitude is received.

With so-called broadcast videoconferences, a presentation- oriented style of communication is supported. This means that one participant of the videoconference is the presenter and the other participants are his listeners, who only occasionally take an active part in videoconference. In this case the lecturing participant can give himself priority by means of a defined control command so that he appears as a full image on the screens of the participants.

For this purpose, the second image processing unit BVZ has a priority allocation 'e unit PE integrated into it.

In both of the two cases mentioned, the speech detection unit SE and the priority allocation unit PE generate control data which causes the appropriate components of the videoconference system VS to transmit video signals as described over the telecommunication network N.

In the present dL;ign example the subscriber terminal T and the videoconference server Z each have two signal converters which operate in accordance with different algorithms, and which therefore make it possible to encode and decode the video data into either a small image or a full image. It is also possible to have further image formats, in addition to the small image and full image, if a corresponding number of additional signal converters is provided in the subscriber terminal T and the videoconference server Z. It is also possible to provide signal converters which operate according to several different algorithms, so-called multistandard signal converters. Instead of two or more .Io signal converters in the subscriber terminal T or the videoconference server Z, only one such multistandard signal converter is then required, which is controlled by the control units of the relevant components of the videoconference system VS in accordance with the currently requested form of display.

Claims

1. A video conference system with n subscriber terminals which are connected via a telecommunication network to a videoconference server, wherein each of the n subscriber terminals can encode a moving image or a static image in at least two different ways which produce different amounts of data for the moving image or the static image, and wherein the videoconference server can receive and decode these, at least two, differently encoded moving images or static images of the relevant subscriber terminal, and that, depending on the type of display of the moving image or static image currently requested by the other subscriber terminals taking part in the videoconference, the moving image or the static image from each of the subscriber terminals is transmitted to the videoconference server.

2. A subscriber terminal including a videoconference system as claimed in Claim 1, comprising at least two video signal converters each operating 15 according to a predetermined algorithm, and a control unit which, as a result of S. control data transmitted to the subscriber terminal, can switch a moving image or a static image to one of the, at least two, video signal converters.

3. A videoconference server for a videoconference system as claimed in Claim 1, comprising n first, video signal coiiverters which operate as claimed in 20 a first algorithm, and n second signal converters which operate according to a second algorithm; and a switching matrix which makes it possible, by means of a control unit and incoming control data, to switch a plurality of incoming encoded video data streams, corresponding to a moving image or a static image, either to one of the n first signal converters or to one of the n second signal converters.

4. A videoconference system as claimed in Claim 1, wherein the n subscriber terminals are subscriber terminals as claimed in Claim 2; the videoconference server being a videoconference server as claimed in Claim 3 wherein as a result of an exchange of control data between respectively one of the n subscriber terminals and the videoconference server, a first or a second video signal converter of the relevant subscriber terminal, and, via the switching Smatrix, one of the first or one of the second video signal converters of the videoconference server are activated in pairs.

A videoconference system as claimed in Claim 1, wherein the telecommunication network is a packet-oriented telecommunication network.

6. A videoconference system as claimed in Claim 1, comprising means which can determine the current speaker du"ing a videoconference.

7. A videoconference system as claimed in Claim 1, comprising means by which a priority can be allocated to a particular participant in the videoconference.

8. A videoconference system substantially as herein described with reference to the accompanying drawing. DATED THIS TWELFTH DAY OF FEBRUARY 1997 ALCATEL N.V e *a *N N *go *o* e* 0 o o* o o* *go SUMMARY Videoconference System In videoconference systems (VS) the video signal corresponding to the full image of each subscriber terminal is transmitted to a videoconference server This converts the video signal of some subscriber terminals into a video signal corresponding to a small image. With this method, an unnecessarily large amount of the transmission capacity of a telecommunication network is occupied. In accordance with the invention, only that amount of video data from a subscriber terminal is transmitted to the videoconference server which corresponds to the minimum necessary amount of video data required to fulfil the current requirements of the other subscriber terminals. Fig. o* S Se