Patent Publication Number: US-8976220-B2

Title: Devices and methods for hosting a video call between a plurality of endpoints

Description:
FIELD 
     Embodiments of the present disclosure relate to devices and methods for hosting a video call between a plurality of endpoints. More particularly, the present disclosure relates to hosting video calls for the hearing impaired. 
     BACKGROUND 
     Video phone communication systems provide visual and audio communication between two or more users during a communication session. A video phone at a first location can transmit and receive audio and video signals to and from a video phone at a second location such that participants at the first location are perceived to be present or face-to-face with participants at a second location and vice versa. 
     Video phone communication systems span a variety of applications. One contemplated application of a video phone system includes facilitization of a communication session of a hearing-impaired user (e.g., deaf or hard of hearing), because many individuals with significant hearing loss are not able to communicate effectively over conventional telephone systems that rely upon voice communications. The hearing-impaired user may use a video phone during a communication session to relay his or her expressions over the video phone communication system. Such video phone communication systems may facilitate communication sessions between different hearing-impaired users (e.g., video phone to video phone communication), or between a hearing-impaired user and a hearing-capable user (e.g., video phone to voice phone communication), which may be assisted through a video relay service (VRS) that may provide an interpretive (i.e., translation) service by providing a hearing-capable translator who relays the expressions of the hearing-impaired caller to a hearing-capable user on the other end of the communication session in a conventional manner, such as through the use of a voice-based dialogue conveyed over a conventional voice phone. The hearing-capable translator may also translate the voice-based dialogue back to the hearing-impaired user into expressions (e.g., American Sign Language (ASL)). 
     Video phones are sometimes used to facilitate communication between more than two users. In such instances, a display of the video phone is conventionally divided into a plurality of segments, and each segments displays video received from a different video phone. Conventionally, once each of the plurality of segments is assigned to display video received from a different video phone, no more participants may be added to the conversation. The number of participating video phones in a video conversation has also conventionally been limited by heavy computational and data transmission bandwidth demands associated with encoding, transmitting, and decoding video data. 
     U.S. Pat. No. 7,701,930 to Dasgupta et al., the disclosure of which is incorporated herein by this reference in its entirety, describes automatically selecting a limited subset of participants of a video conference for display by using audio detectors to determine which participants spoke most recently. The remaining participants operate in a voice only mode, are not displayed, and computing power and network bandwidth are conserved by suppressing their video output. 
     BRIEF SUMMARY 
     Embodiments of the present disclosure include a video call host module, and methods of hosting a video call. 
     In some embodiments, the present disclosure comprises a video call host module including a transceiver configured to communicate with a plurality of endpoints through one or more networks. The video call host module also comprises a processor operably coupled to the transceiver. The processor is configured to include a decoder configured to convert encoded video data received by the transceiver from the plurality of endpoints to decoded video data, the encoded video data corresponding to a plurality of videos and comprising a plurality of motion vectors. The processor is also configured to include a selector configured to rank the plurality of videos responsive to a motion indicator calculated from the plurality of motion vectors for each of the plurality of videos, and select a predetermined number of highest ranking videos for display at the endpoints. In addition, the processor is configured to include a video mixer configured to utilize the decoded video data to generate a mixed video comprising the predetermined number of highest ranking videos. 
     In other embodiments, the present disclosure comprises a method of hosting a video call. The method comprises receiving encoded video data including a plurality of motion vectors and corresponding to a plurality of videos from a plurality of endpoints participating in a video call at a transceiver of a video call host module. The method also includes utilizing a processor of the video call host module to rank the plurality of videos responsive to a motion indicator calculated from the motion vectors for each of the plurality of videos, and to select a predetermined number of highest ranking videos of the plurality of videos for display. In addition, the method includes utilizing a decoder to decode at least the encoded video data that corresponds to the predetermined number of the plurality of videos. The method further includes utilizing an encoder to convert the mixed video data into encoded mixed video data. The method also includes sending the encoded mixed video data from the transceiver to the plurality of endpoints. 
     In other embodiments, the present disclosure comprises a video call host module including a control circuit. The control circuit is configured to decode video data corresponding to a plurality of videos from a plurality of endpoints. The control circuit is also configured to rank the plurality of videos responsive to a plurality of motion indicators, each of the plurality of motion indicators corresponding to one of the plurality of videos, and each of the plurality of motion indicators calculated from one or more motion vectors of the one of the plurality of videos. The control circuit is additionally configured to select a predetermined number of highest-ranking videos for display. 
     In still other embodiments, the present disclosure comprises a method of hosting a video call. The method includes ranking a plurality of videos generated at a plurality of endpoints participating in a video call with a control circuit responsive to a motion indicator calculated from motion vectors corresponding to each of the plurality of videos. The method also includes utilizing the control circuit to select a predetermined number of highest ranking videos of the plurality of videos. In addition, the method includes receiving encoded video data at a transceiver operably coupled to the control circuit. The encoded video data corresponds to at least the predetermined number of highest ranking videos. The method also includes decoding at least the encoded video data that corresponds to the predetermined number of highest ranking videos with the control circuit. The method further includes utilizing the control circuit to generate mixed video data corresponding to a mixed video comprising the predetermined number of the plurality of videos. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a simplified block diagram of a video call host module; 
         FIG. 2  is a simplified block diagram of an endpoint; 
         FIG. 3  is a simplified block diagram of a multiple participant video call system; 
         FIG. 4  is a simplified front view of a display device of an endpoint; 
         FIG. 5  is a simplified flowchart of a method of initiating and participating in a video call at an endpoint with a plurality of other endpoints; and 
         FIG. 6  is a simplified flowchart of a method of managing video data in a video call between multiple endpoints. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the present disclosure. It should be understood, however, that the detailed description and the specific examples, while indicating examples of embodiments of the present disclosure, are given by way of illustration only and not by way of limitation. From this disclosure, various substitutions, modifications, additions rearrangements, or combinations thereof within the scope of the present disclosure may be made and will become apparent to those of ordinary skill in the art. 
     In accordance with common practice the various features illustrated in the drawings may not be drawn to scale. The illustrations presented herein are not meant to be actual views of any particular method, device, or system, but are merely idealized representations that are employed to describe various embodiments of the present disclosure. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus (e.g., device) or all operations of a particular method. 
     Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. Some drawings may illustrate signals as a single signal for clarity of presentation and description. It should be understood by a person of ordinary skill in the art that the signal may represent a bus of signals, wherein the bus may have a variety of bit widths and the present disclosure may be implemented on any number of data signals including a single data signal. 
     The various illustrative logical blocks, modules, circuits, and algorithm acts described in connection with embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and acts are described generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the embodiments of the disclosure described herein. 
     In addition, it is noted that the embodiments may be described in terms of a process that is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe operational acts as a sequential process, many of these acts can be performed in another sequence, in parallel, or substantially concurrently. In addition, the order of the acts may be re-arranged. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. Furthermore, the methods disclosed herein may be implemented in hardware, software, or both. If implemented in software, the functions may be stored or transmitted as one or more instructions (e.g., software code) on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. 
     It should be understood that any reference to an element herein using a designation such as “first,” “second,” and so forth does not limit the quantity or order of those elements, unless such limitation is explicitly stated. Rather, these designations may be used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements may be employed there or that the first element must precede the second element in some manner. Also, unless stated otherwise a set of elements may comprise one or more elements. 
     Elements described herein may include multiple instances of the same element. These elements may be generically indicated by a numerical designator (e.g.,  110 ) and specifically indicated by the numerical indicator followed by an alphabetic designator (e.g.,  110 A) or a numeric indicator preceded by a “dash” (e.g.,  110 - 1 ). For ease of following the description, for the most part, element number indicators begin with the number of the drawing on which the elements are introduced or most fully discussed. Thus, for example, element identifiers on a  FIG. 1  will be mostly in the numerical format 1xx and elements on a  FIG. 4  will be mostly in the numerical format 4xx. 
     Embodiments of the present disclosure include devices and methods for hosting a video call between a plurality of video communication endpoints in video communication systems. As discussed above, video communication systems span a variety of applications. Embodiments of the present disclosure are generally described herein with reference to a video communication system for use by hearing-impaired users. Such video communication systems may facilitate communication sessions between different hearing-impaired users (e.g., video phone to video phone communication), or between a hearing-impaired user and a hearing-capable user (e.g., video phone to voice phone communication), which may be assisted through a video relay service (VRS). It should be noted, however, that embodiments of the present disclosure may include any application or environment where video calls between a plurality of video communication endpoints are desirable. For example, it is contemplated that embodiments of the present disclosure may include hosting video calls including one or more hearing-capable participants. 
     The term “call” refers to a communication with a video communication endpoint (hereinafter referred to simply as “endpoint”) that may be routed through a number of networks, such as, for example, a private network, the internet, a telephone system, and a VRS. The term “incoming call” refers to an incoming communication to an endpoint. The endpoint may also communicate audio and the video communication may also include audio. 
     The term “endpoint” refers to a specific compilation of hardware components, software components, or a combination thereof. The term “endpoint” may also refer to a software based endpoint that exists on a device configured to execute machine-readable commands, such as, for example a computer. As software, it should be understood that the same endpoint may exist on a first device while a user accesses the endpoint on the first device, and on a second device at a different time while the user accesses the endpoint on the second device. 
     The term “unencoded video” refers to a sequential series of frames, each frame including a plurality of pixels. By way of non-limiting example, an unencoded high-definition video may include a sequential series of frames, each frame including an array of pixels 1,920 pixels wide by 1,080 pixels high, and a frame rate of 60 frames per second. Assuming that each pixel in each frame may be represented by 24 bits of data (8 bits for each of red, green, and blue content of each pixel), a bandwidth needed to transmit, display, process, or store the unencoded video in real time would be about 2.99 gigabits per second (Gbps) (1,920 pixels wide×1,080 pixels high×24 bits per pixel×60 frames per second). 
     The term “encoded video” as used herein refers to a variety of formats, including, for example, H.264, H.263, MPEG-4, Windows Media Video (WMV), Advanced Video Coding (AVC), Audio Visual Standard (AVS), RealVideo, G.711, G.722 and other suitable formats. The term “encoded video” may also refer to video (in some cases also including audio) that is encoded with a lossy encoding process, or a lossless encoding process. One of the goals of encoding video is to decrease the amount of data needed to represent video images. Video images inherently include redundancies which may be mitigated through various techniques. For example, image compression techniques may be used to reduce the amount of data needed to represent each frame of a video image. In other words, the temporal and spatial correlation found in natural image sequences may be exploited for bit rate reduction. Some frames of the video may be replaced with data that enables reconstruction of the replaced frames with remaining frames. Inter frame coding may use motion compensated regions from already decoded pictures as a prediction signal for the currently coded picture. Video coding standards such as, for example, MPEG-4 and H.264, may specify the coding of motion vectors. Motion vectors may describe the translational displacement of rectangular blocks (forward motion coding) between video frames. The term “motion vector” refers to a two-dimensional vector that identifies an offset of a macroblock, region, or combination thereof, common to separate frames of video, in one of the separate frames relative to the other of the separate frames, the macroblock or region defined by a plurality of pixels. The motion vectors may be part of the frame coding and may be used to determine how much motion objects in the frames are undergoing, such as, for example by determining how many motion vectors are needed to reconstruct a frame. 
     The term “decoded video” refers to video that has been reconstructed from encoded video. Decoded video may be similar or identical to an unencoded source video used to generate the encoded video from which the decoded video is reconstructed. For example, decoded video may include the same or a different number of pixels per frame as the unencoded source video. Also by way of example, the decoded video may include the same or a different number of frames per second as the unencoded source video. 
       FIG. 1  is a simplified block diagram of a video call host module  102  (referred to hereinafter as “host module  102 ”). The host module  102  may include a processor  112  operably coupled to a transceiver  114  and a memory device  116 . The processor  112  may include a video encoder  120  (referred to hereinafter simply as “encoder  120 ”), a video decoder  118  (referred to hereinafter simply as “decoder  118 ”), a motion detector module  122  (may be integrated with the decoder  118  in some embodiments), a selector module  124 , and a video mixer  126  (referred to hereinafter simply as “mixer  126 ”). Although in  FIG. 1  the transceiver  114  and the memory device  116  are shown as external to the processor  112 , it should be understood that, in some embodiments, one or more of the transceiver  114  and the memory device  116  may be included in the processor  112 . Also, in  FIG. 1  the encoder  120 , the decoder  118 , the motion detector module  122 , the selector module  124 , and the mixer  126  are depicted as part of the processor  112 . In some embodiments, the processes performed by these modules may be performed with computing instructions executed by the processor  112 . In other embodiments, some or all of these modules may include dedicated hardware for performing the processes. In still other embodiments, one or more of the encoder  120 , the decoder  118 , the motion detector module  122 , the selector module  124 , and the mixer  126  may be external to the processor  112 . Regardless of their configuration, each of the processor  112 , the encoder  120 , the decoder  118 , the motion detector module  122 , the selector module  124 , and the mixer  126  may be collectively referred to herein as “a control circuit.” 
     The processor  112  may be configured to execute commands stored on the memory device  116 . By way of non-limiting example, the memory device  116  may include a computer readable media, such as read only memory (ROM), random access memory (RAM), Flash memory, and combinations thereof. The processor  112  may also be configured to control, and send and receive data through the transceiver  114 . The transceiver  114  may be configured to send and receive data through one or more networks  306  ( FIG. 3 ). 
     The decoder  118  may be configured to decode encoded video data  128  received from the transceiver  114  into decoded video data  136 . The encoded video data  128  may correspond to a plurality of encoded videos originating at a plurality of endpoints  204  ( FIGS. 2 and 3 ), and the decoded video data  136  may correspond to a plurality of decoded videos, which are generated by decoding the encoded video data  128 . The decoder  118  may also be configured to access motion vectors  134  from the encoded video data  128 . In addition, the decoder  118  may, in some embodiments, be configured to extract the motion vectors  134  for further processing. Such extraction of motion vectors  134  may be accomplished by modifying a traditional decoder device or algorithm to extract the motion vectors  134 . In some embodiments, the decoder  118  may convert the encoded video data  128  to decoded video data  136  that includes the same number of pixels and frames per second as an unencoded video from which the encoded video data  128  was derived. In other embodiments, the decoder  118  may decode the encoded video data  128  to decoded video data  136  that includes one or both of a different number of pixels and a different number of frames per second as the unencoded video from which the encoded video data  128  was derived. 
     The motion detector module  122  may be configured to calculate a motion indicator  138  for each decoded video from the motion vectors  134  accessed by the decoder  118 . By way of non-limiting example, the motion indicator  138  may be calculated based on a number of motion vectors  134  per video frame, a magnitude of the motion vectors  134 , a position in the video frame that the motion vectors  134  correspond to, a correlation to predetermined motion vectors, other motion vector  134  features, and combinations thereof. In some embodiments, the decoder  118  may parse and export the motion vectors  134 , and the selector module  124  may be configured to count the motion vectors  134 . The motion detector module  122  may continuously or periodically calculate the motion indicator  138  from the motion vectors  134 . Also, the motion indicator  138  may in some embodiments be, for example, a sum of motion vectors  134  for a frame, an average number of motion vectors  134  per frame, a moving average of the number of motion vectors  134  per frame, a running median of motion vectors  134  per frame, a rate of change of the number of motion vectors  134  per frame, other suitable indicators, and combinations thereof. In some embodiments, traditional motion detection based on video frame analysis may be used to calculate the motion indicator  138  if the decoder  118  is unable to extract the motion vectors  134 . 
     The selector module  124  may be configured to rank each decoded video based on its corresponding motion indicator  138 , and selected decoded video data  140  may be passed to the mixer  126 . The selected decoded video data  140  may include decoded video data  136  that corresponds to a predetermined number of the highest ranking decoded videos. In some embodiments, the selector module  124  may compare each motion indicator  138  with a predetermined threshold that may typically result from video of a person signing in American Sign Language (ASL). In other embodiments, the selector module  124  may compare each motion indicator  138  with a predetermined threshold that may typically result from video of a person performing a predetermined hand-signal, such as, for example, raising a hand to a top-right corner of a video window. Decoded videos with corresponding motion indicators  138  that are closer to the predetermined threshold may be ranked higher than decoded videos with corresponding motion indicators  138  that are further from the predetermined threshold. 
     The mixer  126  may be configured to combine each of the decoded videos corresponding to the selected decoded video data  140  into a single unencoded mixed video, corresponding to mixed selected video data  142 . The unencoded mixed video may include a sequential series of frames separated into a plurality of segments  454  ( FIG. 4 ), each segment  454  dedicated to one of the decoded videos. 
     The encoder  120  may be configured to encode the mixed selected video data  142  into encoded mixed video data  130 . The encoded mixed video data  130  may be encoded in a variety of formats, including, for example, MPEG-4, Windows Media Video (WMV), Advanced Video Coding (AVC), Audio Visual Standard (AVS), RealVideo, and other suitable formats. The encoded mixed video data  130  may also be encoded with a lossy encoding process, or a lossless encoding process. The processor  112  may cause the transceiver  114  to send the encoded mixed video data  130  to the plurality of endpoints  204  ( FIGS. 2 and 3 ). 
     The host module  102  may optionally include a camera  144 , a display device  146 , and an input device  150 , similar to a camera  244 , a display device  246 , and an input device  250 , respectively, as will be discussed in more detail with respect to an endpoint  204  of  FIG. 2 . Inclusion of the camera  144 , the display device  146 , and the input device  150  in the host module  102  may enable the host module  102  to participate in a video call as an endpoint  204 . In order to provide the decoder  118  with encoded local video data  132  and corresponding motion vectors  134 , the camera  144  may be operably coupled to the encoder  120 . The camera  144  may capture video images, and convert the video images to unencoded local video data  148 . The encoder  120  may convert the unencoded local video data  148  to encoded local video data  132 , which the decoder  118  may receive and analyze with the encoded video data  128 . 
       FIG. 2  is a simplified block diagram of an endpoint  204 . The endpoint  204  may include a processor  212  operably coupled to a transceiver  214 , a memory device  216 , an input device  250 , a display device  246 , and a camera  244 . The processor  212  may be configured to execute commands stored on the memory device  216 . By way of non-limiting example, the memory device  216  may include a computer readable media, such as read only memory (ROM), random access memory (RAM), Flash memory, and combinations thereof. The processor  212  may include a video decoder  218  (hereinafter referred to as “decoder  218 ”), and a video encoder  220  (hereinafter referred to as “encoder  220 ”). The decoder  218  may be configured to convert encoded video data, such as the encoded mixed video data  130  originating at the host module  102 , into decoded mixed selected video data  242 . The encoder  220  may be configured to convert unencoded video data  248  from the camera  244  to encoded video data  128 . In some embodiments, the processes performed by the encoder  220  and decoder  218  may be performed with computing instructions executed on the processor  212 . In other embodiments, some or all of these modules may include dedicated hardware for performing the processes. In still other embodiments, one or more of the encoder  220  and the decoder  210 , may be external to the processor  212 . 
     The transceiver  214  may be configured to receive the encoded mixed video data  130  and send the encoded video data  128  through one or more networks  306  ( FIG. 3 ) to a host module  102  ( FIG. 1 ). 
     The camera  244  may include devices capable of capturing video images and converting the video images to data, as will be readily apparent to those skilled in the art. By way of non-limiting example, the camera  244  may include a webcam, a camcorder device, a camera device integrated into the same enclosure as the processor  112 , or other suitable devices. The camera  244  may be configured to deliver unencoded video data  248  to the processor  212 . 
     The display device  246  may be any device capable of receiving video data, such as the decoded mixed selected video data  242 , and displaying video images corresponding to the video data. By way of non-limiting example, the display device  246  may be any of a light-emitting diode (LED) array, a liquid crystal display (LCD), a cathode ray tube (CRT) display, a plasma display, a projector, and combinations thereof. In some embodiments, the display device  246  may be external to an enclosure that houses the processor  212 . In other embodiments, the display device  246  may reside in the same enclosure as the processor  212 , such as, for example, in a smart phone or a tablet computer. The display device  246  may also be configured to present one or more options to a user of the endpoint  204 . By way of non-limiting example, the display device  246  may present a send invitation to join call option  458 , and an exit call option  460  ( FIG. 4 ). 
     The input device  250  may be configured to enable the user of the endpoint  204  to control some functions of the endpoint  204 . The input device  250  may also be configured to enable the user to select the one or more options presented by the display device  246 . By way of non-limiting example, the input device  250  may include a keyboard, a numerical keypad, a mouse, a touch-screen, a button array, a track pad, a remote control, motion sensors, haptic sensors, orientation sensors, position sensors, a microphone, and combinations thereof. 
     Although the endpoint  204  is described herein with particular emphasis on hearing impaired video calls, the endpoint  204  and host module  102  ( FIG. 1 ) may also be configured to enable video calls between hearing-capable users. As such, the endpoint  204  may include a speaker (not shown) for playing audio corresponding to the video being displayed on the display device  246 , and a microphone for converting sounds corresponding to a verbal conversation to data. The processor  212  may, consequently, be configured to cause the transceiver  214  to send and receive audio data corresponding to the encoded video data  128  and the encoded mixed video data  130 . 
       FIG. 3  is a simplified block diagram of an example of a multiple-participant video call system  300 . The multiple-participant video call system  300  of  FIG. 3  includes a plurality of endpoints  204 - 1 ,  204 - 2 ,  204 - 3 ,  204 - 4 ,  204 - 5  (referred to generally together as “endpoints  204 ,” and individually as “endpoint  204 ”) and a host module  102  configured to communicate with each other through one or more networks  306 . 
     Some endpoints  204 , such as endpoint  204 - 5  of  FIG. 3 , may be configured for intervention from a video relay service  308 , which may provide sign language translation to a user, such as a hearing-capable user  310 , participating in a video call with other users communicating in sign language. By way of non-limiting example, the hearing-capable user  310  may utilize a standard telephone to communicate with the video relay service  308  through the networks  306 , and the video relay service  308  may send encoded video of a person serving as a translator signing a translation of the words spoken by the hearing-capable user  310  to the host module  102  through the one or more networks  306 . 
     The one or more networks  306  (also referred to herein as “networks  306 ”) may include an internet protocol (IP) network configured to transmit communications between the endpoints  204  and the host module  102 . The networks  306  may also include other networks, such as, for example, public switched telephone networks (PSTNs). Although relatively low data rates associated with PSTNs are generally not ideal for transmitting video data, PSTNs may be adequate to transmit audio data between a conventional telephone and a video relay service  308 . The networks  306  may include a wide area network (WAN), a local area network (LAN), a personal area network (PAN), and combinations thereof. In some embodiments, the networks  306  may include a cloud network. The networks  306  may be configured to communicate with the endpoints  204  and the host module  102  wirelessly, through a cable, and combinations thereof. Some non-limiting examples of suitable wireless communications may include “WiFi,” Bluetooth, and mobile wireless networks. Some non-limiting examples of suitable cables include fiber-optic cables, coaxial cables, traditional telephone cables, and Ethernet cables. 
     Referring now to  FIGS. 1 through 3 , in operation, each endpoint  204  may capture a video of a person participating in a video call hosted by the host module  102 , and convert the video to unencoded video data  248 . The endpoints  204  may convert the unencoded video data  248  into encoded video data  128 , and send the encoded video data  128  to the host module  102 . The host module  102  may receive the encoded video data  128  from each of the endpoints  204 , and utilize motion vectors  134  from the encoded video data  128  to determine a motion indicator  138  corresponding to each of the endpoints  204 . The host module  102  may rank the videos from each of the endpoints  204  based on the corresponding motion indicators  138 . The host module  102  may convert at least the encoded video data  128  corresponding to a predetermined number of highest-ranking videos to decoded video data  136 . The host module  102  may combine the decoded video data  136  corresponding to the predetermined number of highest-ranking videos into a single mixed video with corresponding mixed selected video data  142 . The host module  102  may convert the mixed selected video data  142  into encoded mixed video data  130 , and send the encoded mixed video data  130  to the endpoints  204 . The endpoints  204  may display video corresponding to the encoded mixed video data  130  to users of the endpoints  204 . 
     The ranking of the various videos may include other parameters. As a non-limiting example, one or more of the participants may be defined as to be always presented (e.g., a participant who is hosting the video call, a supervisor, a person designated to direct the conversation, etc.) and will, therefore, be ranked highest regardless of the motion indicator  138  for the video stream. As another non-limiting example, a video stream that is presently being displayed may include a higher priority relative to a video stream that is not presently being displayed. In this way, a non-displayed video stream may need to have a relatively higher motion indicator  138  than a displayed video stream in order to be presented and knock out one of the displayed video streams. The users of the endpoints  204  may see the users of the endpoints  204  that correspond to the predetermined number of highest-ranking videos on the display devices  246 . As the users perform acts that cause the rankings of the videos to change over time, different users of the endpoints  204  may be displayed at different times. By way of non-limiting example, at any given time the predetermined number of highest-ranking videos may correspond to the endpoints  204  whose users most recently signed in American Sign Language. Also by way of non-limiting example, at any given time the predetermined number of highest-ranking videos may correspond to the endpoints  204  whose users are performing the greatest amount of motion. Consequently, the number of participants in a video call may exceed a number of segments  454  on a screen  452  ( FIG. 4 ) of a display device  246 . 
     In some embodiments, the host module  102  may send different encoded mixed video data  130  to different endpoints  204 . By way of non-limiting example, the host module  102  may exclude a first video corresponding to a first endpoint  204 - 1  when ranking videos to be included in a first mixed video to be sent to the first endpoint  204 - 1 . Consequently, the first endpoint  204 - 1  may only receive encoded mixed video data  130  including videos originating at other endpoints  204 . Limiting the encoded mixed video data  130  sent to the first endpoint  204 - 1  in this way may be advantageous as a user of the first endpoint  204 - 1  may prefer to dedicate the limited number of videos included in the encoded mixed video data  130  received at the first endpoint  204 - 1  to videos originating at other endpoints  204 . Furthermore, the first endpoint  204 - 1  may already access the video that originates at the first endpoint, therefore receiving the video that originates at the first endpoint  204 - 1  as part of the encoded mixed video data  130  is redundant. Such embodiments may require a significant amount of processing power as the processor  112  ( FIG. 1 ) would be required to mix and encode a separate mixed video for each endpoint participating in a video call. A central server with relatively high network  306  bandwidth and processing power may optionally be used as the host module  102  to provide the needed bandwidth for the network  306  and encoder  120 . 
     In some embodiments, each endpoint  204  may receive the same encoded mixed video data  130  corresponding to the same predetermined number of highest ranking videos. In such embodiments, less network  306  bandwidth and processing power may be required. If the host module  102  is itself an endpoint with limited network  306  bandwidth and processing power, such embodiments may be preferred. 
     In still other embodiments the multiple participant video call system may be configured as a distributed multiple control unit (MCU). In such embodiments, the processor  212  ( FIG. 2 ) of each endpoint  204  may be configured to perform similar functions to those of the processor  112  ( FIG. 1 ) of the host module  102 . By way of non-limiting example, each endpoint  204  may be configured to receive encoded video data  128  from the other endpoints  204 , rank the corresponding videos based on a motion indicator  138  calculated from the motion vectors  134  of each video, select a predetermined number of the highest ranking videos based on the motion indicator  138 , generate a mixed video including the predetermined number of highest ranking videos, and cause the display device  246  to display the mixed video. In such embodiments, each endpoint  204  would require a sufficiently powerful processor  212  to decode the encoded video data  128  from the other endpoints  204 , and a sufficient communication bandwidth to the networks  306  to receive the encoded video data  128  from each of the other endpoints  204 . 
     In further embodiments, each endpoint  204  may utilize the motion vectors  134  from the encoded video data  128  it generates to determine the corresponding motion indicator  138 . The endpoints  204  may send the motion indicators  138  to the host module  102 , which may rank the videos and select the predetermined number of highest-ranking videos. The host module  102  may cause the endpoints  204  corresponding to the predetermined number of highest-ranking videos to send encoded video data  128  to the host module  102 . The host module  102  may decode, mix, and re-encode the predetermined number of highest-ranking videos, and send the resulting encoded mixed video data  130  to the endpoints. Such embodiments may reduce the amount of network  306  bandwidth and the processing power of the host module  102  needed to operate the multiple-participant video call system  300 . 
       FIG. 4  is a simplified front view of a display device  446  of an endpoint  204 . The display device  446  may include a screen  452  configured to display the predetermined number of highest-ranking videos corresponding to the decoded mixed selected video data  242  ( FIG. 2 ). The screen  452  may be configured to display the plurality of videos in a plurality of segments  454 - 1 ,  454 - 2 ,  454 - 3 ,  454 - 4  (referred to generally together as “segments  454 ” and individually as “segment  454 ”) of the screen  452 . Each segment  454  may be configured to display one of the predetermined number of highest-ranking videos selected by the selector module  124  of the host module  102  ( FIG. 1 ). 
     In some embodiments, the screen  452  may also be configured to display a list  456  of the participants that are participating in a video call. The screen  452  may indicate which participants from the list  456  are currently displayed participants  464 , and which participants from the list  456  are not currently displayed participants  468 . On the screen  452  of  FIG. 4 , for example, the currently displayed participants  464  are grouped together, and separated from the not currently displayed participants  468  by a dashed line. In other embodiments, text such as “on screen” may be placed next to the currently displayed participants  468 . In still other embodiments any of highlights, color coded text, icons, other indicators, and combinations thereof, may be used to indicate which participants from the list  456  are currently displayed participants  464 . 
     The screen  452  may also be configured to present a send invitation to join call option  458  and an exit call option  460 . A user may select the send invitation to join call option  458  or the exit call option  450  by using the input device  250  of the endpoint  204  ( FIG. 2 ). 
     The screen  452  may optionally be configured to display a thumbnail  462  of the local user&#39;s own video. The thumbnail  462  may assist the user in positioning his or her self in a suitable location relative to the camera  244  of the endpoint  204 . The thumbnail  462  may also enable the user to perform some act that may move the user&#39;s video up in the rankings, such as, for example, placing a hand in the top right corner of the video. 
       FIG. 5  is a simplified flowchart  570  of a method of initiating and participating in a video call at an endpoint  204  with a plurality of other endpoints  204  ( FIGS. 2 and 3 ). Referring to  FIGS. 1 through 5 , the method may include determining whether the endpoint  204  is currently participating in a video call. If the endpoint  204  is not currently participating in a video call, a screen  452  of the endpoint  204  may present a send invitation to join call option  458  to a user of the endpoint  204  at operation  574 . A user may select the send invitation to join call option  458  by using the input device  250 . 
     If the user of the endpoint  204  selects the send invitation to join call option  458 , the endpoint  204  may cause the screen  452  to prompt the user to indicate one or more of the plurality of other endpoints  204  that the user desires to invite to join the video call at operation  578 . In some embodiments, the screen  452  may display a list of contacts stored on the memory device  216 , and the user may utilize the input device  250  to select the contacts that the user desires to invite to join the video call. In other embodiments, the processor  212  may cause the endpoint  204  to prompt the user for one or more unique identifiers corresponding to the plurality of other endpoints  204  that the user desires to invite to join the video call, such as, for example, internet protocol (IP) addresses, usernames associated with IP addresses on a server, a directory stored on a memory device  116  of a host module  102  or a server, and combinations thereof. 
     At operation  580 , one of the endpoint  204  and the host module  102 , or both, if integrated together, may send invitations to the one or more of the plurality of other endpoints  204  that the user indicated at operation  578 . In some embodiments, the processors  212  of the other endpoints  204  may cause the screens  452  of the other endpoints  204  to indicate the invitation to join the video call, and prompt the users of the other endpoints  204  to accept or reject the invitation to join the video call. The users of the other endpoints  204  may use the input devices  250  of the other endpoints  204  to indicate their acceptance or rejection of the invitation to join the video call. 
     At operation  582 , the host module  102  may initiate a video call with the other endpoints  204  whose users accepted the invitation to join the video call. During the video call, video is captured, encoded, decoded, displayed, and exchanged between the endpoints  204  and the host module  102 . Greater detail regarding the capture, encoding, decoding, displaying, and exchanging of video during the video call is discussed with respect to  FIG. 6 . 
     Returning to operation  572 , if the endpoint  204  is currently participating in a video call, the screen  452  of the endpoint  204  may present the send invitation to join call option  458  and an exit call option  460  to the user at operation  576 . If the user selects the send invitation to join call option  458 , the screen  452  may prompt the user to indicate one or more of the plurality of other endpoints  204  that the user desires to invite to join the video call at operation  578 , and one of the endpoint  204  and the host module  102  may send invitations to the one or more indicated endpoints  204  at operation  580 , as previously discussed. At operation  584 , the host module  102  may add accepting invitees to the video call. 
     Returning to operation  576 , if the user selects the exit call option  460 , the endpoint  204  may exit from participating in the video call at operation  586 . The endpoint  204  may stop sending data to and receiving data from the other endpoints  204 . 
       FIG. 6  is a simplified flowchart  688  of a method of managing video data in a video call between multiple endpoints  204  ( FIGS. 2 and 3 ). Referring to  FIGS. 1 through 4  and  6 , the method may include receiving encoded video data  128  at a host module  102  at operation  690 . The encoded video data  128  may originate at each of a plurality of endpoints  204 , and may correspond to encoded videos originating at each of the endpoints  204 . The method may include converting the encoded video data  128  to decoded video data  136  and accessing motion vectors  134  from the encoded video data  128  at operation  692 . 
     The method may also include utilizing the motion vectors  134  to determine a motion indicator  138  for each of the decoded videos corresponding to the decoded video data  136  at operation  694 . By way of non-limiting example, determining the motion indicator  138  may be based on a number of motion vectors  134  per video frame, a magnitude of the motion vectors  134 , a position in the video frame that the motion vectors  134  correspond to, a correlation to predetermined motion vectors, other motion vector  134  features, and combinations thereof. 
     In some embodiments, the decoder  118  may extract the motion vectors  134  from the encoded video data  128  at operation  692 . In such embodiments, the decoder  118  may continuously decode all of the encoded video data  128  received from all the endpoints  204  in order to monitor the motion vectors  134 . In other embodiments, the endpoints  204  may each extract the motion vectors  134  from their corresponding encoded video data  128  at encoding, and the host module  102  may receive the motion vectors  134  with the encoded video data  128  at operation  690 . In such embodiments, the decoder  118  may only decode the encoded video data  128  corresponding to videos that will be selected for display, as discussed more fully with respect to operation  696 . Limiting the amount of encoded video data  128  that the decoder  118  decodes may decrease a total decoder  118  bandwidth needed to operate the host module  102 . Decoder  118  bandwidth may, in some instances, be a limiting design constraint. Consequently, in situations where the host module  102  includes a relatively limited decoder  118 , extraction of the motion vectors  134  during encoding at the endpoints  204  may be advantageous. 
     Once motion indicators  138  have been determined, the method may include selecting from the decoded videos for videos that will be displayed at the endpoints  204 . Selecting from the decoded videos for videos that will be displayed at the endpoints  204  may include ranking the videos based on the motion indicators  138  that have been assigned thereto. By way of non-limiting example, if the display devices  246  of the endpoints  204  are configured to display four videos at a time, then the four highest ranking streams may be selected for display. 
     At operation  698 , the host module  102  may mix the selected videos together into a single video corresponding to mixed selected video data  142 . At operation  601 , the mixed selected video data  142  may be converted to encoded mixed video data  130 . The host module  102  may send the encoded mixed video to the endpoints  204  at operation  603 . 
     While certain illustrative embodiments have been described in connection with the figures, those of ordinary skill in the art will recognize and appreciate that embodiments encompassed by the disclosure are not limited to those embodiments explicitly shown and described herein. Rather, many additions, deletions, and modifications to the embodiments described herein may be made without departing from the scope of embodiments encompassed by the disclosure, such as those hereinafter claimed, including legal equivalents. In addition, features from one disclosed embodiment may be combined with features of another disclosed embodiment while still being encompassed within the scope of embodiments encompassed by the disclosure as contemplated by the inventors.