Abstract:
Systems and methods are provided for video conferencing geographically disperse users. Each user operates a user computer. A network connection is established among the user computers. A respective connection speed with the network connection is determined independently for each user computer. A video signal is transmitted from one of the user computers over the network connection to others of the user computers at the independently determined connection speeds.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is related to the following commonly assigned, concurrently filed applications, each of which is incorporated herein by reference in its entirety for all purposes: U.S. patent application Ser. No. ______, entitled “BANDWIDTH MANAGEMENT OF MULTIMEDIA TRANSMISSION OVER NETWORKS,” filed by Jacob Apelbaum (Attorney Docket No. 20375-067600US) and U.S. patent application Ser. No. ______, entitled “MANAGEMENT OF VIDEO TRANSMISSION OVER NETWORKS,” filed by Jacob Apelbaum (Attorney Docket No. 20375-067700US). 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This application relates to video conferencing systems and methods.  
         [0003]     Effective collaboration in business and other environments has long been recognized as being of considerable importance. This is particularly true for the development of new ideas as interactions fostered by the collaboration may be highly productive in expanding those ideas and generating new avenues for thought. As business and other activities have become more geographically disperse, efforts to provide collaborative environments have relied on travel by individuals so that they may collaborate in person or have relied on telecommunications conferencing mechanisms.  
         [0004]     Travel by individuals to participate in a conference may be very costly and highly inconvenient to the participants. Despite this significant drawback, it has long been, and still is, the case that in-person collaboration is viewed as much more effective than the use of telecommunications conferencing. Telephone conferences, for example, provide only a limited form of interaction among the participants, does not easily permit side conversations to take place, and is generally a poor environment for working collaboratively with documents and other visual displays. Some of these drawbacks are mitigated with video conferencing in which participants may see and hear other, but there are still weaknesses in these types of environments as they are currently implemented.  
         [0005]     There is accordingly a general need in the art for improved conferencing capabilities that provides for high interactivity among conference participants.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     Embodiments of the invention thus provide methods of video conferencing a plurality of geographically disperse users. Each user operates a respective one of a plurality of user computers. A network connection is established among the plurality of user computers. A respective connection speed with the network connection is determined independently for each of the plurality of user computers. A video signal is transmitted from one of the user computers over the network connection to others of the user computers. The video signal is transmitted to each of the others of the user computers at the connection speed determined independently for the each of the others of the user computers.  
         [0007]     The connection speed for at least two of the plurality of user computers may be different. In some embodiments, a bandwidth level over the network connection is monitored in real time, with the respective connection speed for at least one of the plurality of user computers being changed in accordance with the bandwidth level.  
         [0008]     Various functionalities complementary to the transmission of the video signal may be provided in different embodiments. For instance, in one embodiment, an audio signal is also transmitted from the one of the user computers over the network connection to the others of the user computers. In another embodiment, an instant-messaging connection is established among the plurality of user computers. This permits an instant message to be transmitted over the instant-messaging connection form one of the plurality of user computers to another of the plurality of user computers. The instant message may be transmitted over the instant-messaging connection from the one of the plurality of user computers to a plurality of others of the user computers. A record of the instant message may be saved.  
         [0009]     In further embodiments, a directory of the plurality of user computers is provided. A data file may be transmitted from the one of the user computers over the network connection to another of the user computers. A computer program may also be shared over the network connection among the plurality of user computers. Access to a desktop of a first of the plurality of user computers may be provided over the network connection by a second of the plurality of user computers different from the first of the user computers.  
         [0010]     Embodiments of the invention may also include a variety of techniques to improve and/or optimize transmission of the video signal. For example, in one embodiment, data that comprises a graphical object is transmitted from the one of the user computers over the network connection to the others of the user computers. The graphical object is cached, and a cache identifier identifying the graphical object is sent from the one of the user computers over the network connection to the others of the user computers.  
         [0011]     In other embodiments, a portion of the video signal that will be obscured by a graphical output is identified. The video signal is then transmitted without the portion of the video signal that will be obscured by the graphical output.  
         [0012]     In various embodiments, the video signal comprises a sequence of frames. In one such embodiment, the sequence of frames is analyzed for redundant information, with the redundant information being stripped from the transmitted video signal. In another such embodiment, each frame comprises a plurality of color pixels. Each frame is analyzed to identify insignificant pixels, with a color depth of the insignificant pixels being reduced.  
         [0013]     Methods of the invention may be embodied in a computer-readable storage medium having a computer-readable program embodied therein for directing operation of a computer system to conference a plurality of geographically disperse users, each of whom operates a respective one of a plurality of user computers. The computer-readable program includes instructions to implement the methods as described above. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein like reference numerals are used throughout the several drawings to refer to similar components.  
         [0015]      FIG. 1  is a flow diagram summarizing multiple capabilities that may be provided with a conferencing application in an embodiment of the invention;  
         [0016]      FIG. 2A  as a flow diagram that summarizes aspects of video and audio conferencing within the conferencing application;  
         [0017]      FIG. 2B  is an exemplary screen view that illustrates aspects of  FIG. 2A ;  
         [0018]      FIG. 3A  is a flow diagram that summarizes aspects of an instant-messaging capability within the conferencing application;  
         [0019]      FIG. 3B  is an exemplary screen view that illustrates aspects of  FIG. 3A ;  
         [0020]      FIG. 4A  is a flow diagram that summarizes aspects of a locator service within the conferencing application;  
         [0021]      FIG. 4B  is an exemplary screen view that illustrates aspects of  FIG. 4A ;  
         [0022]      FIG. 5A  is a flow diagram that summarizes aspects of a file-transfer capability within the conferencing application;  
         [0023]      FIG. 5B  is an exemplary screen view that illustrates aspects of  FIG. 5A ;  
         [0024]      FIG. 6A  is a flow diagram that summarizes aspects of a program-sharing capability within the conferencing application;  
         [0025]      FIG. 6B  is an exemplary screen view that illustrates aspects of  FIG. 6A ;  
         [0026]      FIG. 7A  is a flow diagram that summarizes aspects of a desktop-sharing capability within the conferencing application;  
         [0027]      FIG. 7B  is an exemplary screen view that illustrates aspects of  FIG. 7A ;  
         [0028]      FIG. 8A  is a flow diagram that summarizes aspects of a method for sequence optimization that may be used by the conferencing application;  
         [0029]      FIG. 8B  is a set of frames that illustrates aspects of  FIG. 8A ;  
         [0030]      FIG. 9A  is a flow diagram that summarizes aspects of a method for palette optimization that may be used by the conferencing application;  
         [0031]      FIG. 9B  is a set of frames that illustrates aspects of  FIG. 9A ;  
         [0032]      FIG. 10A  is a flow diagram that summarizes aspects of a method for frame-reduction optimization that may be used by the conferencing application;  
         [0033]      FIG. 10B  is a set of frames that illustrates aspects of  FIG. 10A ;  
         [0034]      FIG. 11A  is a flow diagram that summarizes aspects of a method for motion analysis and frame keying that may be used by the conferencing application;  
         [0035]      FIG. 11B  is a set of frames that illustrates aspects of  FIG. 10A ;  
         [0036]      FIG. 12A  is a flow diagram that summarizes aspects of a method for video-sequence transmission that may be used by the conferencing application;  
         [0037]      FIG. 12B  is a set of frames that illustrates aspects of  FIG. 12A ; and  
         [0038]      FIG. 13  is a schematic representation of a computational unit that may be used to implement the conferencing application in embodiments of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0000]     1. Overview  
         [0039]     Embodiments of the invention provide a multifunctional application that establishes a real-time communications and collaboration infrastructure. A plurality geographically distributed user computers are interfaced by the application to create a rapid work environment and establish integrated multimodal communications. In embodiments of the invention, the application may provide telephony and conferencing support to standard switched telephone lines through an analog modem; high-speed connectivity through an integrated-services digital network (“ISDN”) modem and virtual private network (“VPN”), with adapter support; telephony and conferencing support through a Private Branch Exchange (“PBX”); and point-to-point or multiuser conferencing support through a data network. Using these internet-protocol (“IP”) telephone features, collaborative connections may be established rapidly across private and/or public networks such as intranets and the Internet.  
         [0040]     An overview of different types of functionality that may be provided with the application is illustrated with the flow diagram of  FIG. 1 . As with all flow diagrams provided herein, the identification of specific functionality within the diagram is not intended to be limiting; other functionality may be provided in addition in some embodiments or some functionality may be omitted in some embodiments. In addition, the ordering of blocks in the flow diagrams is not intended to be limiting since the corresponding functionality may be provided in a variety of different orders in different embodiments.  
         [0041]     At block  104 , audio and video conferencing capability is provided by using any of the supported environments to establish a connection among the geographically distributed user computers. For example, the connection may be established with a public switched telephone network (“PSTN”). Telephone connections made through a PSTN may have most calls transmitted digitally except while in a local loop between a particular telephone and a central switching office, where speech from a telephone is usually transmitted in analog format. Digital data from a computer is converted to analog by a modem, with data being converted back to its original form by a receiving modem. Basic telephony call support for modems is supported with the conferencing application using PSTN lines, such as dialing and call termination. In addition, computer-based support may be provided using any suitable command set known to those of skill in the art, such as the Hayes AT command set.  
         [0042]     An ISDN may also be used in establishing the conferencing capability. An ISDN is a digital service provided by both regional and national telecommunications companies, typically by the same company that supports the PSTN. ISDN may provide greater data-transfer rates, in one embodiment being on the order of 128 kbps, and may establish connections more quickly than PSTN connections. Because ISDN is fully digital, the lengthy process of analog modems, which may take up to about a minute to establish a connection, is not required. ISDN may also provide a plurality of channels, each of which may support voice or digital communications, as contrasted with the single channel provided by PSTN. In addition to increasing data throughput, multiple channels eliminate the need for separate voice and data lines. The digital nature of ISDN also makes it less susceptible to static and noise when compared with analog transmissions, which generally dedicate at least some bandwidth to error correction and retransmission, permitting the ISDN connections to be dedicated substantially entirely to data transmission.  
         [0043]     A PBX is a private telephone switching system connected to a common group of PSTN lines from one or more central switching offices to provide services to a plurality of devices. Some embodiments of the invention use such PBX arrangements in establishing a connection. For example, a telephony server may be used to provide an interface between the PBX and telephony-application program-interface (“TAPI”) enabled devices. A local-area-network (“LAN”) based server might have multiple connections with a PBX, for instance, with TAPI operations invoked at any associated client and forwarded over the LAN to the server. The server then uses third-party call control between the server and the PBX to implement the client&#39;s call-control requests. The server may be connected to a switch using a switch-to-host link. It is also possible for a PBX to be directly connected to the LAN on which the server and associated clients reside. Within these distributed configurations, different subconfigurations may also be used in different embodiments. For instance, personal telephony may be provided to each desktop with the service provider modeling the PBX line associated with the desktop device as a single-line device with one channel; each client computer would then have one line device available. Alternatively, each third-party station may be modeled as a separate-line device to allow applications to control calls on other stations, enabling the conferencing application to control calls on other stations.  
         [0044]     IP telephony may be used in other embodiments to provide the connections, with a device being used to capture audio and/or video signal from a user, such information being compressed and sent to intended receivers over the LAN or a public network. At the receiving end, the signals are restored to their original form and played back for the recipient. IP telephony may be supported by a number of different protocols known to those of skill in the art, including the H.323 protocols promulgated by the International Telecommunications Union (“ITU”) and described in ITU Publication H.323, “Packet-based multimedia communications systems,” the entire disclosure of which is incorporated herein by reference.  
         [0045]     At its most basic level, the H.323 protocol permits users to make point-to-point audio and video phone calls over the Internet. One implementation of this standard in embodiments of the invention also allows voice-only calls to be made to conventional telephones using IP-PSTN gateways, and audio-video calls to be made over the Internet. A call may be placed by the dialing user interface identifying called parties in any of multiple ways. Frequently called users may be added to speed-dial lists. After resolving a caller&#39;s identification to the IP address of the computer on which he is available, the dialer makes TAPI calls, which are routed to the H.323 telephony service provider (“TSP”). The service provider then initiates H.323 protocol exchanges to set up the call, with the media service provider associated with the H.323 TSP using audio and video resources available on the computer to connect the caller and party receiving the call in an audio and/or video conference. The conferencing application also includes a capability to listen for incoming H.323 IP telephony calls, to notify the user when such calls are detected, and to accept or reject the calls based on the user&#39;s choice.  
         [0046]     In addition the H.323 protocol may incorporate support for placing calls from data networks to the switched circuit PSTN network and vice versa. Such a feature permits a long-distance portion of a connection to be carried on private or public data networks, with the call then being placed onto the switched voice network to bypass long-distance toll charges. For example, a user in a New York field office could call Denver, with the phone call going across a corporate network from the field office to the Denver office, where it would then be switched to a PSTN network to be completed as a local call. This technique may be used to carry audio signals in addition to data, resulting in a significant lowering of long-distance communications bills.  
         [0047]     In some embodiments, the conferencing application may support pass-through firewalls based on simple network address translation. A simple proxy server makes and receives calls between computers separate by firewalls.  
         [0048]     As indicated at block  108  of  FIG. 1 , the conferencing application may also provide instant-messaging capability. In one embodiment, a messaging engine may be provided that uses a TAPI subsystem for cross messaging, providing a common method for applications and devices to control the underlying communications network. Other functionality that may be provided by the conferencing application includes a locator service directory as indicated at block  112 , a file-transfer capability as indicated at block  116 , a whiteboarding capability as indicated at block  120 , a program-sharing capability as indicated at block  124 , and a remote-desktop-sharing capability as indicated at block  128 . Each of these functionalities is described in further detail below. The whiteboarding capability may conveniently be used in embodiments of the invention to provide a shared whiteboard for all conference participants, permitting each of the participants to contribute to a collective display, importing features to the display, adding comments to the display, changing features in the display, and the like. The whiteboard is advantageously object-oriented (both vector and ASCII) in some embodiments, rather than pixel-oriented, enabling participants to manipulate the contents by clicking and dragging functions. In addition, a remote pointer or highlighting tool may be used to point out specific contents or sections of shared pages. Such a mechanism provides a productive way for the conference participants to work with documentary materials and to use graphical methods for conveying ideas as part of the conference. In addition to these functions, the conferencing application may include such convenient features as remote-control functionality, do-not-disturb features, automatic and manual silence-detection controls, dynamic network throttling, plug-and-play support and auto detection for voice and video hardware, and the like.  
         [0000]     2. Conferencing Application  
         [0049]     In a typical business-usage environment, the conferencing application may be used by employees to connect directly with each other via a local network to establish a whiteboard session to share drawings or other visual information in a conversation. In another application, the conferencing application may be used to place a conference voice call to several coworkers in different geographical locations to discuss the status of a project. All this may be achieved by placing calls through the computers with presence information that minimizes call cost, while application sharing and whiteboard functionality saves time and optimizing communications needs.  
         [0050]     Gateway and gatekeeper functionality may be implemented by providing several usage fields, such as gatekeeper name, account name, and telephone number, in addition to fields for a proxy server and gateway-to-telephone/videoconferencing systems. Calls may be provided on a secure or nonsecure basis, with options for secure calls including data encryption, certificate authentication, and password protection. In some embodiments, audio and video options may be disabled in secure calls. One implementation may also provide a host for the conference with the ability to limit features that participants may enact. For example, meeting hosts may disable the right of anyone to begin any of the functionalities identified in blocks  108 - 128 . Similarly, the implementation may permit hosts to make themselves the only participants who can invite or accept others into the meeting, enabling meeting names and passwords.  
         [0051]     Further aspects of the video and audio conferencing functionalities are illustrated with the flow diagram of  FIG. 2A  and the exemplary screen view of  FIG. 2B . The screen view  228  shows an example of a display that may provided and includes the video stream being generated. The video and/or audio connection is established at block  204  of  FIG. 2A  using one of the protocols described in detail above. With the connection established, information, ideas, applications, and the like may be shared at block  208  using the video and/or audio connections. Real-time video images may be sent over the connection as indicated at block  212 ; in some instances, such images may include instantly viewed items, such as hardware devices, displayed in front of a video collection lens. Options to provide playback control over video may be provided with such features as “pause,” “stop,” “fast forward,” and “rewind.” A sensitivity level of a microphone that collects audio data may advantageously be adjusted automatically at block  216  to ensure adequate audio levels for conference participants to hear each other. The conferencing application may permit video window sizes to be change during a session as indicated at block  220 . The conferencing application may also include certain optimization techniques for dynamically trading off between faster video performance and better image quality as indicated generally at block  224 . Further description of such techniques is provided below.  
         [0052]     Further aspects of the instant-messaging functionalities are illustrated with the flow diagram of  FIG. 3A  and the exemplary screen view of  FIG. 3B . The screen view  324  shows an example of a message that may be received as part of such an instant-messaging functionality and illustrates different fields for receiving and transmitting messages. This functionality is enabled by establishing an instant-messaging connection at block  304  of  FIG. 3A . Text messages typed by one user may be transmitted to one or more other users at block  308 . In instances where the messages are transmitted to all conference participants, as indicated at block  312 , a “chat” functionality is implemented. In instances where a private message is transmitted to a subset of the conference participants, as indicated at block  316 , a “whisper” functionality is implemented. The contents of the chat session may conveniently be recorded by the conferencing application at block  320  to provide a history file for future reference.  
         [0053]     Functions of the locator service directory are illustrated with the flow diagram of  FIG. 4A  and corresponding exemplary screen view  420  of  FIG. 4B . The locator service directory permits users to locate individuals connected to a network and thereby initiate a conferencing session that includes them. Such functionality is centered around a directory that may be configured to identify a list of users currently running the conferencing application. The directory is provided at block  404  of  FIG. 4A , enabling a user to receive a selection of another user at block  408 . A connection is established between the originating user and the selected user with the conferencing application at block  412 , permitting conferencing functions between the two users to be executed. As indicated at block  416 , a variety of server transactions may also be performed in some embodiments, such as enabling different directories to be view, creating directory listing of available users, and the like.  
         [0054]     The file-transfer functionality is illustrated further with the flow diagram of  FIG. 5A  and corresponding exemplary screen view  520  of  FIG. 5B . As indicated at block  504 , this functionality permits a file to be sent in the background to conference participants. It is possible in different embodiments for the file to be sent to everyone included in a particular conference or only to selected participants, as indicated at block  508 . Each participant may have the ability to accept or reject transferred files at block  512 . Data-compression techniques may advantageously be used at block  516  to accelerate file transfers.  
         [0055]     Further aspects of the file-sharing functionality are illustrated with the flow diagram of  FIG. 6A  and the corresponding exemplary screen view  620  of  FIG. 6B . The file-sharing functionality generally enables share programs to be viewed in a frame, as indicated at block  604 , a feature that makes it easy to distinguish between shared and local applications on each user&#39;s desktop. A user may thus share any program running on one computer with other participants in a conference. Participants may watch as the person sharing the program works, or the person sharing the program can allow program control to other meeting participants. Only the person sharing the program needs to have the program installed on his computer. The shared program frame may also be minimized so that the user may proceed with other functions if (s)he does not need to work in the current conference program. Similarly, this functionality makes it easy for users to switch between shared programs using the shared-program taskbar. Limitations may be imposed at block  608  by the conference initiator to permit only a single user to work in the shared program at any particular time. Access to the shared program by additional conference participants may be permitted in accordance with an instruction by the originating user at block  612 .  
         [0056]     An illustration of the remote-desktop functionality is illustrated with the flow diagram of  FIG. 7A  and corresponding exemplary screen view  712  of  FIG. 7B . After the remote-desktop functionality has been enabled at block  704 , users have the ability to operate a user computer from a remote location, such as by operating an office computer from home or vice versa. A secure connection with a password may be used to access the remote desktop in such configurations at block  712 .  
         [0057]     The various implementations described above may include different security features. For example, encryption protocols may be used to encode data exchanged between shared programs, transferred files, instant messages, and whiteboard content. Users may be provided with the ability to specify whether all secure calls are encrypted and secure conferences may be held in which all data are encrypted. User-authentication protocols may be implemented to verify the identity of conference participants by requiring authentication certificates. For instance, a personal certificate issued by an external certifying authority or an intranet certificate server may be required of any or all of the conference participants. Password protections may also be implemented by the originating user required specification of the password by other conference participants to join the conference.  
         [0000]     3. Optimization  
         [0058]     Embodiments of the invention use a number of different optimization and bandwidth-management techniques. The average bandwidth use of audio, video, and data among the computers connected for a conference may be intelligently managed on a per-client basis. In addition, a built-in quality-of-service (“QoS”) functionality is advantageously included for network that do not currently provide RSVP and QoS. Such built-in QoS delivers advanced network throttling support while ensuring that conferencing sessions do not impact live network activity. This enables a smooth operation of the separate conferencing components and limits possible consumption of bandwidth resources on the network.  
         [0059]     In one embodiment, audio, video, and data subsystems each create streams for network transmission at their own rates. The audio subsystem creates a stream at a fairly constant rate when speech is being sent. The video subsystem may produce a stream at a widely varying rate that depends on motion, quality, and size settings of the video image. The data subsystem may also produce a stream at a widely varying rate that depends on such factors as the use of file transfer, file size, the complexity of a whiteboard session, the complexity of the graphic and update information of shared programs, and the like. In a specific embodiment, the data stream traffic occurs over the secondary UDP protocol to minimize impact on main TCP arteries.  
         [0060]     Bandwidth may be controlled by prioritizing the different streams, with one embodiment giving highest priority to the audio stream, followed by the data stream, and finally by the video stream. During a conference, the system continuously or periodically monitors bandwidth use to provide smooth operation of the applications. The bandwidth use of the audio stream is deducted from the available throughput. The data subsystem is queried for a current average size of its stream, with this value also being deducted from the available throughput. The video subsystem uses the remaining throughput to create a stream of corresponding average size. If no throughput remains, the video subsystem may operate at a minimal rate and may compete with the data subsystem to transmit over the network. In such an instance, performance may exhibit momentary degradation as flow-control mechanisms engage to decrease the transmission rate of the data subsystem. This might be manifest with clear-sounding audio, functional data conferencing, and with visually useful video quality, even at low bit rates.  
         [0061]     Various optimization techniques used in different embodiments are illustrated with  FIGS. 8A-12B . These optimization techniques generally seek to reduce the amount of data transmitted during a conference, thereby maintaining high performance levels for the users.  FIGS. 8A and 8B  respectively provide a flow diagram and set of frame views to illustrate a sequence optimization method. The codec assignments to the video feed are based on a number of parameters. As indicated respectively at blocks  804 ,  808 , and  812 , various parameters may be factorized, including the connection bandwidth, the RSVP and QoS provisioning, and the connection speed. Video hardware accelerators are identified at block  816  and requests for changes in frame size and quality are identified at block  820 . The resulting codec assignment is implemented at block  824 .  
         [0062]     Graphical information may be sent as orders in some embodiment. Instead of sending graphical updates as bitmap information exclusively, the conferencing application may instead send the information as the actual graphical commands used by a program to draw information on a user&#39;s screen. In addition, various caching techniques may be used as part of the sequence optimization. Data that comprises a graphical object may be sent only once, with the object then stored in a cache. The next time the object is to be transmitted, a cache identifier may be transmitted instead of the actual graphical data. Maintenance of a queue of outgoing data may also minimize the impact on a local user when a program calls graphical functions faster than the conferencing application can transmit the graphics to remote conference participants. Graphical commands are queued as they are drawn to the screen, and the graphical functions are immediately returned so that the program can continue. An asynchronous process subsequently transmits the graphical command. Changes in the outgoing data queue may also be monitored. When the queue becomes too large, the conferencing application may collect information based on the area of the screen affected by the graphical orders rather than the orders themselves. Subsequently, the necessary information is transmitted collectively.  
         [0063]     A method for color-palette optimization is illustrated with the flow diagram of  FIG. 9A  and corresponding set of frames  924  of  FIG. 9B . This method reduces the color depth of insignificant pixels in order to reduce the overall size of a transmitted image by transmitting only pixels relevant to the image integrity. At block  904 , global and local palettes are shrunk to reduce the color depth, and the local dependency on the client palette is removed. A global meta-palette is created at block  912 , permitting the client palette to be removed at block  916  after a successful merge with a new global palette. The meta-palette is mapped to the new global palette at block  920 .  
         [0064]     A frame-reduction method may also be used, as illustrated with the flow diagram of  FIG. 10A  and the corresponding set of frames  1020  of  FIG. 10B . The sequence frames are shrunk at block  1004 , such as to the smallest possible rectangle. Duplicated pixels are replaced with transparency and alpha channels at block  1008 , permitting creation of a complete pixel vector map for the new image at block  1012 . Redundant and noncritical frames are marked and removed at block  1016 . This method permits the conferencing application to check, prior to adding a new piece of graphic output to the outgoing data queue, for existing output that the new graphic output might obscure. Existing graphic output in the queue that will be obscured by the new graphic output is discarded and the obscured output never gets transmitted. This method also permits the conferencing application to analyze various image frames for redundant information, stripping that redundant information from the transmission.  
         [0065]     A method for motion analysis and frame keying is illustrated with the flow diagram of  FIG. 11A  and the corresponding set of frames  1116  shown in  FIG. 11B . Excessive motion patterns within a family of related frames are identified at block  1104  of  FIG. 11A , permitting new anchor frames to be generated at block  1108 , based on statistical trends and new frame variances. The intermediate frames on excessive motions may be eliminated at block  1112  so that the size of the transmission is correspondingly reduced.  
         [0066]     A method for optimizing video-sequence transmission is illustrated with the flow diagram of  FIG. 12A  and the corresponding set of frames  1220  provided in  FIG. 12B . This method is related to the method described in connection with  FIGS. 8A and 8B  and results in a dynamic reassignment of codecs based on certain identified parameters. For example, at block  1204 , changes in connection bandwidth, RSVP and QoS provisioning, and/or connection speed are identified. At block  1208 , video hardware changes are identified. At block  1212 , changes in frame size and/or in image quality are identified. Based on these identifications, the dynamic reassignment of codecs is implemented at block  1216 .  
         [0067]     The conferencing application described herein may be embodied on a computational device such as illustrated schematically in  FIG. 5 , which broadly illustrates how individual system elements may be implemented in a separated or more integrated manner. The computational device  500  is shown comprised of hardware elements that are electrically coupled via bus  526 . The hardware elements include a processor  502 , an input device  504 , an output device  506 , a storage device  508 , a computer-readable storage media reader  510   a , a communications system  514 , a processing acceleration unit  516  such as a DSP or special-purpose processor, and a memory  518 . The computer-readable storage media reader  510   a  is further connected to a computer-readable storage medium  510   b , the combination comprehensively representing remote, local, fixed, and/or removable storage devices plus storage media for temporarily and/or more permanently containing computer-readable information. The communications system  514  may comprise a wired, wireless, modem, and/or other type of interfacing connection and permits data to be exchanged with external devices.  
         [0068]     The computational device  500  also comprises software elements, shown as being currently located within working memory  520 , including an operating system  524  and other code  522 , such as a program designed to implement methods of the invention. It will be apparent to those skilled in the art that substantial variations may be used in accordance with specific requirements. For example, customized hardware might also be used and/or particular elements might be implemented in hardware, software (including portable software, such as applets), or both. Further, connection to other computing devices such as network input/output devices may be employed.  
         [0069]     Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Accordingly, the above description should not be taken as limiting the scope of the invention, which is defined in the following claims.