Abstract:
A method of capturing an image from a video call between a first user and a remote user over a communication network. The method includes receiving video data from the remote user at a client executed at a user terminal of the first user, the video data comprising a sequence of frames; the client capturing a frame of the video data responsive to a command from the first user; the client extracting image data from the frame; the client converting the image data to an image file and embedding a communication identity of the remote user in the image file, wherein the communication identity is suitable for initiating a communication event with the remote user; and storing the image file on a storage means of the user terminal.

Description:
RELATED APPLICATION  
       [0001]    This application claims priority under 35 U.S.C. §119 or 365 to Great Britain, Application No. 0712879.6, filed Jul. 3, 2007. The entire teachings of the above application are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    This invention relates to a video communication system and method, particularly but not exclusively for use in a voice over internet protocol communication system. 
       BACKGROUND 
       [0003]    Voice over internet protocol (“VoIP”) communication systems allow the user of a device, such as a personal computer, to make calls across a computer network such as the Internet. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long distance calls. To use VoIP, the user must install and execute client software on their device. The client software provides the VoIP connections as well as other functions such as registration and authentication. Advantageously, in addition to voice communication, the client may also provide video calling and instant messaging (“IM”). 
         [0004]    One type of VoIP communication system uses a peer-to-peer (“P2P”) topology built on proprietary protocols. To access the peer-to-peer system, the user must execute P2P client software provided by a P2P software provider on their PC, and register with the P2P system. When the user registers with the P2P system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the P2P system without the further use of a server. In particular, the users can establish their own communication routes through the P2P system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the P2P system. The exchange of the digital certificates between users provides proof of the user&#39;s identities and that they are suitably authorised and authenticated in the P2P system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a P2P system are disclosed in WO 2005/009019. 
         [0005]    As mentioned, one advantage of VoIP communication systems is the ability to support video calling. With video calling, the callers are able to view video images of the other party in addition to voice information. This obviously enables much more natural communication between the parties, as facial expressions are also communicated, thereby making video calls more comparable to a face-to-face conversation. 
         [0006]    Traditional public switched telephone networks generally do not offer video calling functionality to users. High data rate mobile networks, such as 3 rd  generation (“ 3 G”) mobile networks may offer video calling, but this generally expensive to the user. VoIP video calling is, by contrast, of very low cost or free to the user. 
         [0007]    The visual aspect of a VoIP video call enables it to be utilised to display to remote party something that could otherwise only be described verbally, or would require a photograph to be taken and sent to the other party separately. An example of this is a new baby, who can be shown to relatives (some of which may live a long distance away) using video calling. 
         [0008]    Therefore, a video call, which comprises a sequence of frames, may contain images that the called party may wish to keep (e.g. an image of the new baby, from the example above). There is therefore a need for a technique to capture and manage images from a video call stream in an efficient and user-friendly manner. 
       SUMMARY 
       [0009]    According to one aspect of the present invention there is provided a method of capturing an image from a video call between a first user and a remote user over a communication network, comprising: receiving video data from said remote user at a client executed at a user terminal of the first user, said video data comprising a sequence of frames; said client capturing a frame of said video data responsive to a command from said first user; said client extracting image data from said frame; said client converting said image data to an image file and embedding a communication identity of said remote user in said image file, wherein said communication identity is suitable for initiating a communication event with said remote user; and storing the image file on a storage means of said user terminal. 
         [0010]    Preferably, the communication identity is a username of the remote user. In one embodiment, the communication event is a voice call. In another embodiment, the communication event is a video call. In another embodiment, the communication event is a file transfer. Preferably, the file transfer is a transfer of said image file. In another embodiment, the communication event is an instant messaging conversation. 
         [0011]    Preferably, the command from said first user comprises the actuation by said first user of a control displayed in a user interface of said client. Preferably, the image file is a portable network graphics format image file. Preferably, the step of displaying said video data to said first user in a user interface of said client. Preferably, the step of capturing said frame comprises said client copying said frame from said user interface of said client displayed on said user terminal of said first user. 
         [0012]    In one embodiment, said step of capturing said frame comprises: said client transmitting a request message to a corresponding client of said remote user over said communication network, wherein said request message requests said corresponding client to copy said frame from said video data; said client accepting a request to establish a file transfer from said corresponding client; and said client receiving said frame using said file transfer from said corresponding client. 
         [0013]    Preferably, the method further comprises the step of embedding the date and time of the image capture in said image file. Preferably, the step of storing the image file comprises storing the image file in a predetermined directory on said storage means of said user terminal. Preferably, the method further comprises the step of said client playing a sound to said first user responsive to capturing the frame of said video data. 
         [0014]    In one embodiment, the user terminal of the first user is a personal computer. In another embodiment, the user terminal of the first user is a mobile device. 
         [0015]    According to another aspect of the present invention there is provided a computer program product comprising program code means which when executed by a computer implement the steps according to the above defined method of capturing an image from a video call. 
         [0016]    According to another aspect of the present invention there is provided a method of initiating a communication event between a first user and a remote user over a communication network, comprising: executing a communication client at a user terminal of the first user; said client opening an image file stored at said user terminal responsive to a command from said first user, said image file comprising image data and an embedded communication identity of said remote user; reading the communication identity from the image file and displaying an image from said image data; and displaying at least one user-operable control in association with said image, wherein, responsive to actuation of said at least one user-operable control by said first user, said client uses said communication identity to initiate a communication event with said remote user over said communication network. 
         [0017]    Preferably, the communication identity is a username of the remote user. In one embodiment, the communication event is a voice call. In another embodiment, the communication event is a video call. In another embodiment, the communication event is a file transfer. Preferably, said file transfer is a transfer of said image file. In another embodiment, the communication event is an instant messaging conversation. 
         [0018]    Preferably, the method further comprises said client determining a presence state for said remote user using said communication identity, and displaying said presence state in association with said image. Preferably, the method further comprises said client determining a name for said remote user using said communication identity, and displaying said name in association with said image. 
         [0019]    Preferably, said image file further comprises the date and time of the creation of said image file, and the method further comprises the step of said client reading the date and time and displaying the data and time in association with said image. Preferably, said image is stored on a storage means of said user terminal, and wherein said step of opening said image file comprises accessing a predetermined directory of said storage means. Preferably, the method further comprises the step of opening at least one other image file stored in said predetermined directory and displaying said at least one other image file as a thumbnail image. 
         [0020]    Preferably, said communication network is a voice over internet protocol communication network. Preferably, said voice over internet protocol communication network is a peer-to-peer communication network. 
         [0021]    In one embodiment, the user terminal of the first user is a personal computer. In another embodiment, the user terminal of the first user is a mobile device. 
         [0022]    According to another aspect of the present invention there is provided a computer program product comprising program code means which when executed by a computer implement the steps according to the above defined method of initiating a communication event. 
         [0023]    According to another aspect of the present invention there is provided a user terminal for capturing an image from a video call between a first user and a remote user over a communication network, comprising: processing means arranged to execute a client, wherein said client is configured to receive video data comprising a sequence of frames, capture a frame of said video data responsive to a command from said first user, extract image data from said frame, convert said image data to an image file and embed a communication identity of said remote user in said image file, wherein said communication identity is suitable for initiating a communication event with said remote user; and storage means for storing the image file on said user terminal. 
         [0024]    According to another aspect of the present invention there is provided a user terminal for initiating a communication event between a first user and a remote user over a communication network, comprising: display means; storage means; and processing means arranged to execute a client, wherein said client is configured to open an image file stored on said storage means responsive to a command from a first user of the user terminal, said image file comprising image data and an embedded communication identity of a remote user, read the communication identity from the image file, display an image from said image data on said display means, and display at least one user-operable control in association with said image on said display means, wherein, responsive to actuation of said at least one user-operable control by said first user, said client uses said communication identity to initiate a communication event with said remote user over said communication network. 
         [0025]    According to another aspect of the present invention there is provided a method of capturing a video clip from a video call between a first user and a remote user over a communication network, comprising: receiving video data from said remote user at a client executed at a user terminal of the first user, said video data comprising a sequence of frames; said client capturing a plurality of said frames of said video data responsive to a command from said first user; said client converting said plurality of said frames to an video file and embedding a communication identity of said remote user in said video file, wherein said communication identity is suitable for initiating a communication event with said remote user; and storing the video file on a storage means of said user terminal. 
         [0026]    According to another aspect of the present invention there is provided a method of initiating a communication event between a first user and a remote user over a communication network, comprising: executing a communication client at a user terminal of the first user; said client opening an video file stored at said user terminal responsive to a command from said first user, said video file comprising video data and an embedded communication identity of said remote user; reading the communication identity from the video file and displaying a video from said video data; and displaying at least one user-operable control in association with said video, wherein, responsive to actuation of said at least one user-operable control by said first user, said client uses said communication identity to initiate a communication event with said remote user over said communication network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    For a better understanding of the present invention and to show how the same may be put into effect, reference will now be made, by way of example, to the following drawings in which: 
           [0028]      FIG. 1  shows a VoIP communication network; 
           [0029]      FIG. 2  shows a user interface of a VoIP client; 
           [0030]      FIG. 3  shows a detailed view of a user terminal on which is executed a client; 
           [0031]      FIG. 4  shows the process for a user to authenticate with the VoIP system and initiate a video call with another user; 
           [0032]      FIG. 5  shows a user interface of a client during a video call; 
           [0033]      FIG. 6  shows an image viewer displayed during a video call with one stored image; 
           [0034]      FIG. 7  shows an image viewer displayed during a video call with a plurality of stored images; 
           [0035]      FIG. 8  shows a video image capture option in a pop-up menu; 
           [0036]      FIG. 9  shows a user interface of a client with a menu option to view subsequently captured images; 
           [0037]      FIG. 10  shows an image viewer displayed subsequent to a video call; 
           [0038]      FIG. 11  shows an image viewer displayed subsequent to a video call with hidden controls; 
           [0039]      FIG. 12  shows the process by which a file transfer of an image file may be initiated from the image viewer; 
           [0040]      FIG. 13  shows a pop-up contact window for use in a file transfer; and 
           [0041]      FIG. 14  shows a drop-down menu displayed in the image viewer. 
       
    
    
     DETAILED DESCRIPTION 
       [0042]    Reference is first made to  FIG. 1 , which illustrates a system  100  for enabling the capture and storage of images from a video call over VoIP. In the embodiment shown in  FIG. 1 , a P2P communication system is illustrated, although it will be understood that other forms of communication could also be used. 
         [0043]    A first user of the VoIP communication system (given the example name “Duncan”  102 ) operates a user terminal  104 , which is shown connected to a network  106 , such as the Internet. The user terminal  104  may be, for example, a personal computer (“PC”), personal digital assistant (“PDA”), a mobile phone, a gaming device or other embedded device able to connect to the network  106 . The user device has a user interface to receive information from and output information to a user of the device. In a preferred embodiment of the invention the user interface of the user device comprises a display such as a screen and a keyboard and mouse. The user terminal  104  is connected to the network  106  via a network interface  108  such as a modem, and the connection between the user terminal  104  and the network interface  108  may be via a cable (wired) connection or a wireless connection. 
         [0044]    The user terminal  104  is running a client  110 , provided by the VoIP software provider. The client  110  is a software program executed on a local processor in the user terminal  104 . The user terminal  104  is also connected to a handset  112 , which comprises a speaker and microphone to enable the user to listen and speak in a call. The microphone and speaker does not necessarily have to be in the form of a handset, but can be in the form of a headphone or earphone with an integrated microphone, or as a separate loudspeaker and microphone independently connected to the user terminal  104 . The user terminal  104  is also connected to a camera  113 , which is used to capture video images of Duncan  102  when engaged in a video call. Preferably, the camera  113  is a webcam. 
         [0045]    An example of a user interface  200  of the client  110  executed on the user terminal  104  of Duncan  102  is shown illustrated in  FIG. 2 . The client user interface  200  displays the username  202  of Duncan  102  in the VoIP system, and Duncan can set his own presence state (that will be seen by other users) using a drop down list by selecting icon  204 . 
         [0046]    The client user interface  200  comprises a tab  206  labelled “contacts”, and when this tab is selected the contacts stored by the user in a contact list are displayed. In the example user interface in  FIG. 2 , five contacts of other users of the VoIP system are shown listed in contact list  208 . Each of these contacts have authorised the user of the client  106  to view their contact details and online presence and mood message information. Each contact in the contact list has a presence status icon associated with it. For example, the presence status icon for a contact called “Ben”  210  indicates that Ben is “online”, the presence icon for a contact called “Paul”  212  indicates that Paul is “not available”, the presence icon for a contact called “Martyn”  214  indicates that Martyn&#39;s state is “do not disturb”, the presence icon for a contact called “Bob”  216  indicates Bob is “away”, and the presence icon for a contact called “Andy”  218  indicates that Andy is “offline”. Further presence indications can also be included. Next to the names of the contacts in contact list  208  are mood messages  220  of the contacts. 
         [0047]      FIG. 3  illustrates a detailed view of the user terminal ( 104 ) on which is executed client  110 . The user terminal  104  comprises a central processing unit (“CPU”)  302 , to which is connected a display  304  such as a screen, a storage device such as a hard-disk drive  305 , an input device such as a keyboard  306 , a pointing device such as a mouse  308 , a speaker  310  and a microphone  312 . The speaker  310  and microphone  312  may be integrated into a handset  112  or headset, or may be separate. The CPU  302  is connected to the camera  113 , and is also connected to the network interface  108  as shown in  FIG. 1 . 
         [0048]      FIG. 3  illustrates an operating system (“OS”)  314  executed on the CPU  302 . Running on top of the OS  314  is a software stack  316  for the client  110 . The software stack shows a protocol layer  322 , a client engine layer  320  and a client user interface (“UI”) layer  318 . Each layer is responsible for specific functions. Because each layer usually communicates with two other layers only, they are regarded as being arranged in a stack as shown in  FIG. 3 . The operating system  314  manages the hardware resources of the computer and handles data being transmitted to and from the network via the network interface  108 . The client protocol layer  322  of the client software communicates with the operating system  314  and manages the connections over the VoIP system. Processes requiring higher level processing are passed to the client engine layer  320 , which handles the processing required for the user to make and receive calls over the VoIP system. The client engine  320  also communicates with the user client user interface layer  318 . The client engine  320  may be arranged to control the client user interface layer  318  to present information to the user via the user interface of the client (as shown in  FIG. 2 ) and to receive information from the user via the user interface. The control of the client user interface  318  will be explained in more detail hereinafter. 
         [0049]    Reference is now made to  FIG. 4 , which illustrates the process for Duncan  102  to authenticate with the VoIP system and initiate a video call with another user (for the purposes of this example called “Ben”  118 ) in the system illustrated in  FIG. 1 . 
         [0050]    When Duncan  102  first registers with the VoIP system the client  110  is provided with a digital certificate from a VoIP authentication server  114 , as illustrated in step S 402 . Subsequent to the initial registration with the VoIP system, the user must also provide a username (referred to hereinafter as a VoIP ID) and password in order to log-in to the VoIP system and view their contact list and make calls. This is performed by the user entering the username (VoIP ID) and password into the client  110 , and the username and password are then authenticated with the VoIP authentication server  114 . Alternatively, these authentication details may be stored by the client  110 , so that the user does not need to manually enter them every time the client is executed, but the stored details are still passed to the VoIP authentication server  114  to be authenticated. 
         [0051]    The contact list for the users (e.g. the contact list  208  for Duncan) is stored in a contact server  116  shown in  FIG. 1 . When the client  110  logs into the VoIP system the contact server is contacted (in step S 404 ), and the contact list is downloaded to the user terminal  104 . This allows the user to log into the VoIP system from any terminal and still access the same contact list. The client  110  also periodically communicates with the contact server  116  in order to obtain any changes to the information on the contacts in the contact list, or to update the stored contact list with any new contacts that have been added. Presence information is not stored centrally in the contact server. Rather, the client  110  periodically requests the presence information for each of the contacts in the contact list  208  directly over the VoIP system. 
         [0052]    In step S 406 , a video call is made between Duncan  102  and Ben  118 . Calls to the users in the contact list may be initiated over the VoIP system by selecting the contact listed in the client  110  and clicking on a “call” button  222  (as shown in  FIG. 2 ) using a pointing device such as a mouse. Alternatively, the call may be initiated by typing in the VoIP identity of a contact in the field  224 . Referring again to  FIG. 4 , in the illustrative example of a P2P VoIP system, the call set-up is performed using proprietary protocols, and the route over the Internet  106  between the calling user and called user is determined by the peer-to-peer system without the use of servers. In  FIG. 4 , an illustrative route is shown between the caller Duncan ( 102 ) and the called party, Ben ( 118 ), via other peers ( 120 ,  122 ,  124 ) of the system. It will be understood that this route is merely an example, and that the call may be routed via fewer or more peers. 
         [0053]    Following authentication through the presentation of the digital certificates (to prove that the users are genuine subscribers of the VoIP system—described in more detail in WO 2005/009019), the video call can be made using the transmission of packets comprising video and voice data. The client  110  performs the encoding and decoding of video and voice data packets. Video and voice data packets from the user terminal  104  are transmitted into the Internet  106  via the network interface  108 , and routed by the VoIP system to the computer terminal  126  of Ben  118 , via a network interface  128 . A client  130  (similar to the client  110 ) running on the user terminal  126  of Ben  118  decodes the packets to produce a video and an audio signal that can be displayed on the display device of user terminal  126  and heard by Ben  118  using the handset  132 . Conversely, video images of Ben  118  are captured by camera  134  connected to user terminal  126 , audio data is captured by handset  132 , and the client  130  executed on user terminal  126  encodes the video and audio signals into packets and transmits them across the Internet  106  to the user terminal  104 . The client  110  executed on user terminal  104  decodes the packets from Ben  114 , and produces a video display and an audio signal that can be heard by the user of the handset  112 . 
         [0054]    The packets for the video call described above are passed across the Internet  106  only, and the public switched telephone network (“PSTN”) is not involved. Furthermore, due to the P2P nature of the system illustrated in  FIG. 4 , the actual video calls between users of the VoIP system can be made with no servers being used. This has the advantages that the system scales easily and maintains a high quality, and the call can be made free to the users. It will be appreciated, however, that other (non-P2P) types of communication system could also be used. 
         [0055]    Reference is now made to  FIG. 5 , which illustrates a user interface  500  of the client  130  displayed on user terminal  126  to the user Ben  118  during a video call with the user Duncan  102 . In the centre of the user interface  500  is a display of the video stream  502  from the user Duncan  102  (i.e. the images captured by camera  113  on user terminal  104  and transmitted over the network  106 ). The user interface  500  also shows the name  504  and presence state  506  of the user from whom the video stream is being received. Below the display of the video stream  502  is a smaller video display  508 , which shows the video being captured by the camera  134  on user terminal  126 . In other words, the small video display  508  shows the video stream that is being transmitted from Ben  118  to Duncan  102 . The small video display  508  allows the user to view how he is seen by the remote party, thereby ensuring that his own image is correctly framed. Note that it is not necessary for video to be two-way. For example, a video stream may be received from Duncan  102  without a corresponding video being sent from Ben  118  (this can be the case if, for example, only one party has a webcam or simply if they choose not to send video). In this instance, the small video display  508  is not shown for the party that is not transmitting video. 
         [0056]    The user Ben  118  can end the video call by selecting the call end button  510 . A chat button  512  is present to initiate an IM conversation with the remote user. A drop-down menu with further controls is displayed by actuating menu button  514  (as will be described hereinafter). 
         [0057]    At any point during the video call, the user Ben  118  can activate an image capture button  516 . The activation of the image capture button  516  causes the client  130  to capture the current frame of the video stream  502 . 
         [0058]    The current frame of the video stream can be captured in different ways. In one embodiment, the client  130  can capture the video frame exactly as is displayed in the user interface  500  of the client  130 . In other words, the activation of the image capture button  516  causes a “screen grab” or “screen shot” to be taken of the section of the user interface  500  that displays the video stream  502 . In an alternative embodiment, the activation of the image capture button  516  causes a message to be transmitted from the client  130  to the client  110  running on the user terminal  104  of the remote user (Duncan  102 ). The message instructs the client  110  to capture the current frame of the video from its source—the webcam  113 . Therefore, the client  110  captures the current frame that is being provided by the webcam  113  before it has been encoded and transmitted across the network  106 . The client  110  then establishes a file transfer with client  130  over the network, and transfers the captured frame to the client  130 . This method has the advantage that the image captured is of a higher quality and resolution than the “screen grab” method, as the image is taken directly from its source and has not been encoded for transmission or reduced in size. The file transfer can be performed without interaction from either of the users, so that conversation is not interrupted. 
         [0059]    The current frame of the video stream  502  (captured in either of the two ways above) is converted to a predetermined image format and saved to the storage device (such as hard-disk drive  305  in  FIG. 3 ). In a preferred embodiment, the image format used is the portable network graphics (“PNG”) format. In alternative embodiments, the captured image could be converted and saved using an image format such as JPEG, TIFF, GIF, BMP or any other suitable image format. 
         [0060]    When the client  130  is converting the frame of the video stream to the image format, the client  130  also embeds extra data into the image file, in addition to the image itself. Specifically, the client embeds the user ID of the source of the video stream. Therefore, in this example, when the user Ben  118  activates the image capture button  516 , an image from the video stream  502  originating from Duncan  102  is captured, converted to an image format which has Duncan&#39;s user ID embedded within it, and saved to the storage device of Ben&#39;s user terminal  126 . 
         [0061]    In the preferred embodiment that saves the image in the PNG format, the user ID is stored in a text “chunk” of the PNG file. A “chunk” is a component of a PNG file that stores specific information. A text chunk can be used to store text information, and the user ID can be written as text information into this chunk. The user ID is written into the text chunk after a predetermined text label, allowing the client  130  to search for the known label, and hence extract the user ID. For example, the text label can be “SKYPENAME” and the user ID can be written in the text chunk immediately after this label. Other image formats have similar information containers that can be used to store the user ID. 
         [0062]    The user ID embedded in the image file is a communication identifier, and can be utilised to manage the saved image and also initiate communication events, as will be described in more detail hereinafter. Preferably, further data is also embedded in the image file, such as the date and time at which the image was captured from the video stream. 
         [0063]    Preferably, the image is saved immediately in a predetermined directory on the storage device, without prompting the user for input. In alternative embodiments, however, the client  130  can request that the user specifies the location to which the image is saved. Preferably, the client will also play a sound when the user selects the image capture button  516 . For example, this sound may resemble the sound of a camera shutter or a “click”. 
         [0064]    When the client  130  has converted the image and the embedded data to the required image format, and has stored the image, the client  130  initiates the opening of a pop-up image viewer  600 , as shown in  FIG. 6 . The image viewer  600  loads the saved image and displays it in image pane  602 . The image viewer  600  also reads the embedded data from the image, and displays the name  604  of the contact associated with the embedded user ID. The date and time that the image was taken is read from the embedded data and displayed at  606 . The client can also use the embedded user ID to determine other information about the user associated with the user ID, such as his current presence state, as shown using icon  608 . 
         [0065]    Below the image pane  602  is a thumbnail image region, which displays thumbnails of all the images that the user has captured from video streams and retained. In the case of  FIG. 6 , only one image has been captured, and hence thumbnail  610  is a small representation of the image shown in pane  602 .  FIG. 7  shows an example where more images ( 702 ,  704 ) have been captured, and the most recently captured image ( 610 ) is shown displayed at the end of the sequence of thumbnail images. Selecting a different thumbnail image causes the selected image to be displayed in the image pane  602 . 
         [0066]    Returning to  FIG. 6 , the directory in which the images are stored is indicated at  612 , and the user can choose to close the image viewer  600  by actuating “close” button  614 . 
         [0067]    The image viewer overlays a set of controls over the image in pane  602 . These controls are used to initiate communication events directly from the image viewer by utilising the embedded user ID in the image file. In  FIG. 6 , a chat button  616  is shown, which, when actuated by the user, causes the client  130  to initiate an IM conversation using the user ID from the image file. Therefore, in the case of the example shown in  FIG. 6 , when the user (Ben  118 ) selects the chat button  616 , an IM chat session is initiated by client  130  with Duncan  102 . A file transfer button  618  is also shown, which, when actuated, causes a file transfer of the displayed image to be initiated. This is described in more detail with reference to  FIGS. 12 and 13 , hereinafter. Furthermore, a menu button  620  is also displayed, which comprises further options, and is described in more detail with reference to  FIG. 14 . 
         [0068]    It should be noted that in  FIG. 6  there is not a button to initiate a voice or video call with the user whose user ID is embedded in the image. This is because the image viewer  600  shown in  FIG. 6  has been launched immediately following the image being captured from the video stream (by activating button  516  in  FIG. 5 ). Therefore, at this point there is still an ongoing video call between, for example, Ben  118  and Duncan  102 , and hence it is not possible to initiate a further call whilst the current one is ongoing. However, once the current video call has ended, then this is possible, as will be described with reference to  FIG. 10 , below. 
         [0069]    Reference is now made to  FIG. 8 , which illustrates an alternative method for triggering the capture of an image from a video stream.  FIG. 8  shows the user interface  500  of the client  130  during a video call, as in  FIG. 5 . However, in  FIG. 8 , the user has selected menu button  514 , which causes pop-up menu  802  to be shown. One of the options in the pop-up menu  802  is entitled “Take a video snapshot”  804 , and the selection of this option activates the image capture functionality in the same way as selecting button  516  (described above with reference to  FIG. 5 ). 
         [0070]    Reference is next made to  FIG. 9 , which illustrates the user interface  200  of the client  130  through which images captured during a video call can subsequently be viewed after the call has ended. The user interface  200  comprises the same features as described above with reference to  FIG. 2 . However, in  FIG. 9 , the user has selected the menu item labelled “tools”  902 . The activation of the tools menu button displays the drop-down menu  904 . The drop-down menu  904  comprises a plurality of options (most of which are beyond the scope of this description) including an option labelled “video snapshot . . . ”  906 . 
         [0071]    Selection of the “video snapshot . . . ” option  906  by the user results in the display of the pop-up image viewer  1000  shown in  FIG. 10 . The pop-up image viewer  1000  shown in  FIG. 10  is similar to the image viewer  600  shown immediately after an image is captured (as shown in  FIG. 6  and described hereinbefore). 
         [0072]    In common with the pop-up image viewer  600  of  FIG. 6 , the image viewer  1000  of  FIG. 10  comprises an image pane  1002 , thumbnails ( 1004 ,  1006 ,  1008 ) of the images that have previously been captured by the user, a display of the directory  1010  in which the images are stored, and a “close” button  1012  that closes the pop-up image viewer  1000 . 
         [0073]    When one of the thumbnail images (e.g.  1008 ) is selected by the user the image viewer  1000  reads the embedded data from the image, and displays the image in the image pane  1002 . In particular, the image viewer reads the embedded user ID contained within the image file. This is used to display the name  1014  of the contact associated with the embedded user ID. The date and time that the image was taken is read from the embedded data and displayed at  1016 . The client can also use the embedded user ID to determine other information about the user associated with the user ID, such as his current presence state, as shown using icon  1018 . 
         [0074]    The main difference between the image viewer  600  and the image viewer  1000  is in the controls overlaid over the image being displayed, which can be used to initiate communication events directly from the image viewer. In the image viewer  1000  in  FIG. 10 , controls are displayed to display a drop-down menu  1020  (described with reference to  FIG. 14 , below), initiate a file transfer  1022  (described with reference to  FIG. 12 , below), and initiate an IM conversation  1024  using the embedded user ID. These controls were also present in image viewer  600 . However, the image viewer  1000  additionally has a control to initiate a call  1026 . The user can select button  1026  to initiate a call with the user whose user ID is embedded in the image file being displayed. More specifically, the client  130  uses the embedded user ID to set up a call over the network  106  with the client  110  that is logged in using the embedded user ID. The call established to the user with the embedded user ID may be either a voice call or a video call. 
         [0075]    If the cursor of the pointing device is moved out of the image pane  1002 , or if the cursor is motionless for a predetermined period of time, then the controls ( 1020 ,  1022 ,  1024 ,  1026 ) and the bar showing the name  1014 , time and date  1016 , and presence state  1018  are removed from the image, as illustrated in  FIG. 11 . This allows the user an unencumbered view of the image that has been captured. 
         [0076]      FIG. 12  illustrates the process by which a file transfer of the image file may be initiated from the image viewer  1000 . If the user selects the file transfer button  1022 , then the drop-down menu  1202  is displayed. The drop-down menu  1202  comprises two options. The first option shows the name  1204  of the user whose user ID is embedded in the image file. If this option is selected, then the file transfer is established between the client  130  of Ben  118 , and the client  110  of Duncan  102  (whose user ID is embedded in the image). When the file transfer is established, a copy of the image file comprising Duncan&#39;s user ID is transmitted over the network  106  and received by the client  110 , and can subsequently be viewed and stored on the user terminal  104 . Therefore, using this technique, an image captured from the video stream of a remote user can be sent back to the remote user very readily, using the information embedded in the image file itself, and by the simple selection of a single option in the image viewer displaying the image. 
         [0077]    The second option in menu  1202 , indicated at  1206 , allows the user to send the image file to another (third) user of the communication system. If this option is selected, then the pop-up contact window  1300  shown in  FIG. 13  is displayed. The pop-up contact window  1300  displays the contact list  1302  of the user in order for the user to select a contact to which the image file should be sent. Scrollbars  1304  allow the user to scroll though the contacts if there are more than can be displayed within the pop-up window. The selected contact is highlighted, as shown at  1306 . The user can send the file to the selected contact by activating the “send” button  1308 , or cancel the process by selecting the “cancel” button  1310 . When the send button  1308  is selected, the file transfer is established between client  130  and the client of the selected contact over the network  106 , and the image file comprising the embedded data is transmitted to the selected contact. 
         [0078]    Reference is now made to  FIG. 14 , which shows the drop-down menu  1402  displayed when the user activates the menu button  1020 . The drop-down menu comprises several options that the user can use to manage the currently selected captured image. The user can save a copy of the current image to a given location on the storage device of the user terminal  126  by selecting the “save as . . . ” option  1404 . The user can open the currently selected image in an image editing application by selecting the “edit” option  1406 . The user can delete the currently selected image from the storage device by selecting the “delete” option  1408 . 
         [0079]    The option labelled “send snapshot”  1410  in drop-down menu  1402  provides the same functionality as the file transfer button  1022 , described above with reference to  FIG. 12 . The “set as my picture” option  1412  allows the user to set the currently selected image as their avatar picture in the communication system. The “set as desktop background” option sets the currently selected image as the background image in the operating system of the user terminal  126 . 
         [0080]    In an alternative embodiment, the client  130  is arranged to capture not a single frame of the video, but a clip of the video. In other words, rather than capturing an image from the video stream, a copy of the video stream itself is captured. The length of the video clip captured can be determined by the user (e.g. Ben  118 ) by the length of time that the capture button  516  is activated for. For example, when Ben  118  wants to capture a clip of the incoming video stream, he selects the capture button  516 , and holds it in an activated state for the duration of the clip that he wishes to capture. When he releases the button, the video is saved to the storage device. Alternatively, the client  130  can be arranged to capture a predetermined interval of the video stream with a single activation of the capture button  516 . 
         [0081]    The result of capturing a clip of the video stream is that a sequence of frames have been grabbed by the client. This sequence of frames is converted to a predetermined video format and saved to the storage device (such as hard-disk  305  in  FIG. 3 ). Example video formats include (but are not limited to) AVI, MOV, WMV, 3GP and DivX formats. The client  130  also embeds the user ID of the source of the video stream in the video file, in a similar manner as described above with reference to image files. 
         [0082]    The video file can then be viewed and utilised in a similar manner to the image files described hereinbefore. The pop-up image viewer described with reference to  FIG. 6  comprises an embedded video player arranged to playback the video format used to save the video clip. The user can then view the video clip using the embedded video player. In common with the image embodiment described above, the video player overlays controls over the video to allow communication events such as a call, IM conversation or file transfer to be initiated to the user with the ID embedded in the video. Therefore, the overall operation of the system is the same as that described above for images, except that the pop-up viewer ( 600 ,  1000 ) can playback video clips, rather than only displaying images. 
         [0083]    While this invention has been particularly shown and described with reference to preferred embodiments, it will be understood to those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appendant claims.