Abstract:
A system and method for high resolution video conferencing is shown and described. A transmitting station and a receiving station including video cameras or sensors, a plurality of microphones and speakers, video, audio and communication processing engines are disclosed. Video is processed and transferred through the system allowing for multiple video streams to be produced and audio is processed and transferred through the system allowing for sound to be played back with an indication of position in relation to the videoconferencing system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims the benefit of priority from U.S. Provisional Patent Application No. 60/310,742, entitled “High Resolution Video Conferencing Bar” filed on Aug. 7, 2001, which is herein incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to conferencing systems, and more particularly to a high resolution videoconferencing system.  
           [0004]    2. Description of the Background Art  
           [0005]    Conventionally, videoconferencing systems utilize video cameras to capture an image of the conference participants for transmission to a remote conferencing site. A conventional, (stationary or movable) video camera can only capture one image or one view of a conferencing site at a certain point in time. In order to capture different images or views of a conferencing site at different points in time, a conventional video camera may be beneficially provided with a device for adjusting a rotational orientation of the camera. Positioning devices designed to rotate the camera about two orthogonal axes typically utilize two actuators: a first actuator rotates the camera about a vertical axis and a second actuator rotates the camera about a horizontal axis perpendicular to the camera&#39;s vertical axis. Rotation of the camera about the horizontal axis is referred to as “panning”, while rotation about the vertical axis is referred to as “tilting.” As such, devices for rotating the camera about the horizontal and vertical axis are commonly referred to as “pan/tilt positioning devices.” Further, to capture an image or view that is of a particular interest, such as the image of a speaking conference participant, a conventional video camera would require a set of zoom lenses for performing zooming functions, resulting in a “pan/tilt/zoom” (“PZT”) camera.  
           [0006]    Disadvantageously, conventional PZT cameras have many shortcomings. First, movement of mechanical components in the positioning device can generate a substantial amount of noise. These movements and noise can be annoying and distracting to the conference participants. More importantly, the noise can interfere with acoustic localization techniques utilized to automatically orient the camera in a direction of the speaking participant. Secondly, the mechanical components in the positioning device may be susceptible to misalignment or breakage due to wear or rough handling, thereby rendering the positioning device partially or fully inoperative. A further disadvantage is complexity in manufacturing of the positioning device; thus resulting in high manufacturing costs and, subsequently, high consumer prices.  
           [0007]    With the development of technology, sizes of display screens in videoconferencing systems are getting larger and larger. Consequently, positions of-participant speakers on the display screen can change over a large span area. Disadvantageously, however, conventional videoconferencing systems are unable to adjust to a new participant speaker position as the position changes over the large span area.  
           [0008]    Therefore, there is a need for a videoconferencing system and method which captures multiple views of a conferencing site without involving a complex mechanical structure. There is another need for a videoconferencing system and method which adjusts acoustics relative to a speaker&#39;s position.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides for a videoconferencing system comprising a transmitting station located at a first site, including a plurality of microphones for generating an audio signal in response to a sound source; an audio processing engine for generating a position signal that indicates the position of the sound source and for processing the audio signal; and a communication interface for transmitting the audio and position signals to a communication channel. The plurality of microphones of the videoconferencing system can be arranged in an n-fire configuration as well as a vertical array. The videoconferencing system may also comprise a receiving station located at a second site, including a communication interface for receiving the audio and position signals from the communication channel, a plurality of speakers for playing the audio signal, and an audio processing engine for selectively driving one of the speakers in response to the position signal to play the audio signal on the selected speaker.  
           [0010]    The position signal generated by the videoconferencing system is based upon magnitude differences of electric or current signals received from the plurality of microphones. Whereas, if the position of the sound source changes, the audio processing engine generates a new position signal to reflect a position change.  
           [0011]    The transmitting station communication interface includes a communication processing engine for encoding and compressing the audio signal and the position signal, and a transceiver device for transmitting the audio and position signals through the communication channel. Conversely, the receiving station communication interface includes a transceiver device, for receiving the audio and position signals through the communication channel, and a communication processing engine for decoding and decompressing the audio signal and the position signal.  
           [0012]    In another embodiment, a videoconferencing system comprises a transmitting station located at a first site, including a high resolution video sensor for generating an image, a video memory for storing the high resolution image, a data loading engine for loading image data from the video sensor to the video memory. Additionally, a Field Programmable Gate Array/Application Specific Integrated Circuit (FPGA/ASIC) is coupled to the video memory and data loading engine. The FPGA/ASIC defines a first image section and a second image section within the high resolution image stored in the video memory. Further the FPGA/ASIC can scale the first image section into a first video stream with a first resolution and scale the second image section into a second video stream with a second resolution. A communication interface coupled to the FPGA/ASIC transmits the first video stream and the second video stream to a communication channel. The videoconferencing system may also comprise a receiving station located at a second site, including a communication interface for receiving the first video stream and the second video stream from the communication channel. The receiving station further includes a video processing engine for processing the first video stream and the second video stream and for displaying the first video stream as a first image with a first resolution and displaying the second video stream as a second image with a second resolution, is coupled to the communication interface.  
           [0013]    The transmitting station communication interface in this embodiment comprises a communication processing engine for encoding and compressing the first and second video stream, and a transceiver device for transmitting the first and second video stream through the communication channel. Conversely, the receiving station video processing engine of the present embodiment comprises a video memory for storing the first video stream and the second video stream, a data loading engine for loading the first video stream and the second video stream from the receiving station communication interface and an FPGA/ASIC for displaying the first and second image data stream based on the high resolution image stored in the video memory.  
           [0014]    In yet another embodiment, a videoconferencing system comprises a receiving station located at a first site having a communication interface for receiving a video signal from a communication channel, a video processing engine for generating a video display output in response to the video signal, and a video display for displaying the video display output. The videoconferencing system may further comprise a transmitting station located at a second site, having a video camera for generating the video signal, a video processing engine for processing the video signal, a phase synchronization engine for synchronizing a phase between the video camera at the transmitting station and the video display output at the receiving station, and a communication interface for transmitting the video signal to the communication channel.  
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0015]    [0015]FIG. 1 shows an exemplary videoconferencing system in accordance with the present invention;  
         [0016]    [0016]FIG. 2 shows an exemplary conferencing station;  
         [0017]    [0017]FIG. 3 is an exemplary block diagram illustrating the processing unit of FIG. 2 in greater detail;  
         [0018]    [0018]FIG. 4 is an exemplary block diagram illustrating components in the video processing engine of FIG. 3;  
         [0019]    [0019]FIG. 5 is an exemplary section (or view) configuration in accordance with the present invention;  
         [0020]    [0020]FIG. 6 is a flowchart illustrating an exemplary process for transmitting audio in a videoconferencing system;  
         [0021]    [0021]FIG. 7 is a flowchart illustrating an exemplary process for transmitting high resolution images in a videoconferencing system; and  
         [0022]    [0022]FIG. 8 is a flowchart illustrating an exemplary process for transmitting a video signal in a videoconferencing system.  
     
    
     DESCRIPTION OF THE INVENTION  
       [0023]    [0023]FIG. 1 shows an exemplary videoconferencing system- 100  in accordance with the present invention. The videoconferencing system  100  includes a first conferencing station  102  and a second conferencing station  104 . The first conferencing station  102  includes an audio input/output device  106 , a video display  108  and a video camera (or video sensor)  110 . Similarly, the second conferencing station  104  includes an audio input/output device  112 , a video display  114  and a video camera (or a video sensor)  116 . The first conferencing station  102  communicates with the second conferencing station  104  through a communication channel  118 . The communication channel  118  can be an Internet, a LAN, a WAN, or any other type of network communication means. Although FIG. 1 only shows two conferencing stations  102  and  104 , those skilled in the art will recognize that additional conferencing stations may be coupled to the videoconferencing system  100 .  
         [0024]    [0024]FIG. 2 shows an exemplary conferencing station  200 , similar to the conferencing stations  102  and  104  of FIG. 1, in accordance with one embodiment of the present invention. The conferencing station  200  includes a display  202 , a high resolution conferencing bar  204 , and a video processing unit  206 . Preferably, the display  202  is a High Definition (“HD”) monitor having a relatively large-size flat screen  208  with a 16:9 viewable area. Alternatively, other view area proportions and other types of displays  202  are contemplated and may be used.  
         [0025]    Preferably, the high resolution video conferencing bar  204  contains multiple speakers  210   a  to  210   d , a video sensor (e.g., a high resolution digital video image sensor such as a CMOS video sensor)  212 , and a plurality of microphones  214 . The speakers  210   a  to  210   d  preferably operate at frequencies above 250 Hz. However, the speakers  210   a  to  210   d  may operate at any other frequency compatible with various embodiments of the present invention. In one embodiment, the conferencing bar  204  is approximately 36 inch. wide by 2 inch high and by 4 inch deep, although the conferencing bar  204  may comprise any other dimension. Typically, the conferencing bar  204  is designed to sit atop the display  202  with a front portion  218  extending slightly below a front edge of the display  202 . The positioning of the conferencing bar  204  brings the speakers  210   a  to  210   d , the video sensor  212 , and the plurality of microphones  214  closer to the screen  208 , and provides a positioning reference at the front edge of the display  202 . Other conference bar  204  positions may be utilized in keeping with the scope and objects of the present invention. Further, although only four speakers are shown in FIG. 2, more or less speakers may be utilized in the present invention.  
         [0026]    The video sensor  212  has the capability to output multiple images in real-time at a preferred resolution of  720   i  (i.e., 1280×720 interlaced at 60 fields per second) or higher, although other resolutions are contemplated by the present invention. The resolution of the video sensor  212  is sufficient based on approximately a 65 degree field of view to-capture an entire conferencing site. For a wider degree field of view (such as a 90 degree field of view), a limited horizontal pan motor may be provided. Providing this limited horizontal pan motor results in the avoidance of a costly and complicated full mechanical pan/tilt/zoom camera and lens system. Further, a pure digital zoom may be provided with a fixed lens to accommodate up to an 8× or higher effective zoom while maintaining a minimum Full CIF (352×288) resolution image.  
         [0027]    The plurality of microphones  214  are located on both sides of the video sensor  212  on the conferencing bar  204 , and can be arranged in an n-fire configuration, as shown in FIG. 2, which provides a better forward directional feature. A vertical microphone array can be optionally arranged along a side of the display  202  to provide vertical positioning references.  
         [0028]    The conferencing bar  204  is coupled to the processing unit  206  via a high speed digital link  205 . The processing unit  206  may contain a sub-woofer device that, preferably, operates from 250 Hz down to 50-100 Hz frequencies. The processing unit  206  will be discussed in more details in connection with FIG. 3. Although the processing unit  206  is shown as being separate from the conferencing bar  204 , alternatively, the processing unit  206  may be encompassed within the conferencing bar  204 .  
         [0029]    Because conference participants may not feel comfortable in view of, or seeing the movement of, the video sensor  212 , a smoked glass or similar covering can be installed in front of the video senor  212  and/or other portions of the conferencing bar  204  so that the conference participants cannot view the video sensor  212 , and/or the speakers  210   a  to  210   d  and the plurality of microphones  214 .  
         [0030]    [0030]FIG. 3 is an exemplary block diagram illustrating the processing unit  206  of FIG. 2 in greater detail in accordance with one embodiment of the present invention. The processing unit  206  preferably includes a processing engine  302 , a communication interface  304 , and a sub-woofer device  306 . The processing engine  302  further comprises a phase synchronization engine  308 , a video processing engine  310 , and an audio processing engine  312 . The phase synchronization engine  308  is able to reduce or minimize negative impact caused by transmission delay. Specifically, the video camera  110  (FIG. 1) at the local (or first) conferencing station  102  (FIG. 1) has an arbitrary phase relative to a video display output at a remote (or second) conferencing station  104  (FIG. 1). Thus, the video display output at the remote conferencing station  104  may be out of phase with the video camera  110  located at the local conferencing station  102 .  
         [0031]    Further, in transmitting a source video signal from-the local conferencing station  102  to the remote conferencing station  104 , there is a transmission delay between a time when a source video signal is being generated at the local conferencing station  102  and a time when the source video signal is displayed at the remote conferencing station  104 . The transmission delay cannot be compensated for when the video display output at the remote conferencing station  104  is out of phase with the video camera  110  located at the local conferencing station  102 . As a result, the transmission delay is added to the video display output at the remote conferencing station  104 , which may generate a negative effect in an interactive video conference. For example, when a user at the local conferencing station  102  starts to speak after a pause, participants at the remote conferencing station  104  may still see the user in pause due to the transmission delay. If any of the participants at the remote conferencing station  104  interrupts the user at this moment, the remote participant and the user will talk over each other.  
         [0032]    Advantageously, the present invention synchronizes the phase between the video camera  110  located at the local conferencing station  102  and the video display output at the remote conferencing station  104  so that the transmission delay can be compensated for or reduced in the video display output. Specifically, during a video conference, the video camera  110  at the local conferencing station  102  moves at a certain frequency and speed which causes phase shifting relative to the video display output at the remote conferencing station  104 . The movement of the video camera  110  at the local conferencing station  102  can be measured and used as a reference to synchronize the phase between the video camera  110  and the video display output. The phase synchronization engine  308  includes a memory device  314  for storing a phase synchronization module for performing the phase synchronization or locking function.  
         [0033]    In operation, to transmit a source video signal, the video processing engine  310  first receives a high resolution image from the video sensor  212  (or video camera  110 ) and stores the image into a video memory (not shown). The video processing engine  310  then, preferably, defines two image sections (views) within the high resolution image stored in the video memory, and generates two respective video streams for the two image sections (views). Alternatively, more or less image sections and corresponding video streams are contemplated. The video processing engine  310  then sends the two video streams to the communication interface  304 . Conversely, to display a remote video signal from a remote site, the video processing engine  310  receives at least two video streams (i.e., Video Streams A and B) from the communication interface  304 . The video processing engine  310  then processes the video streams A and B and displays two image views on the screen  208  for the two video streams A and B, respectively.  
         [0034]    To transmit a source audio signal, each of the plurality of microphones  214  (FIG. 2) in the conferencing bar  204  receives a sound from an acoustic source (e.g., from a speaking participant) and converts the received sound to an electric or current signal. Because the plurality of microphones  214  are located at different positions in reference to the conferencing bar  204  and the acoustic source, the electric or current signals in the plurality of microphones  214  have different magnitudes. The magnitude differences in the electric or current signals indicate a position of the acoustic source. Upon receiving the electric or current signals from the plurality of microphones  214 , the audio processing engine  312  generates an audio signal and a position signal. The position signal may contain information indicating a speaker&#39;s position relative to the conferencing bar  204 . If the position of the acoustic source changes, the audio processing engine  312  generates a new position signal to reflect the position change. The audio processing engine  312  then sends the audio and position signals to the communication interface  304 .  
         [0035]    Conversely, to play a remote audio signal from a remote site, the audio processing engine  312  first receives the audio signal and position signal from the communication interface  304 . The audio processing engine  312  then drives one or more of the speakers  210   a  to  210   d  (FIG. 2) in the conferencing bar  204  according to the position signal, while the video processing engine  310  is displaying one or more views of an image on the screen  208 . The speakers  210   a  to  210   d  in the conferencing bar  204  are selected based on the position of the speaking participant displayed on the screen  208 . Because the screen  208  has a relatively large size, the present invention improves video conference by making it appear as if the sound is coming from the location of the speaking participant. It should be noted that the speakers  21 O a  to  210   d  in the speaker array of the conferencing bar  204  operate, typically, at frequencies above 250 Hz, because the sounds within this frequency range have directional characteristics. Consequently, the sub-woofer device  306  (FIG. 3) installed within the video processing unit  206  operates, preferably, at frequencies from 250 Hz down to 50-100 Hz, because the sounds within this frequency range are not directional. Although the present invention is described as including the sub-woofer device  306 , those skilled in the art will recognize that the sub-woofer device  306  is not required for operation and function of the present invention. Those skilled in the art will also recognize that any frequency range of acoustics may be utilized in the present invention. For example, lower frequencies may be used for the speakers  210   a  to  210   d  in the speaker array of the conferencing bar  204 .  
         [0036]    The communication interface  304  includes a transceiver device  316  and a communication processing engine  318 . The transmission of a communication signal containing an audio signal, a position signal, and two video streams A and B requires the communication processing engine  318  to receive the audio and position signals from the audio processing engine  312  and the two video streams A and B from the video processing engine  310 . Subsequently, the communication processing engine  318  encodes and compresses this communication signal and sends it to the transceiver device  316 . Upon receiving the communication signal, the transceiver device  316  forwards the communication signal to a remote site through the communication channel  118 .  
         [0037]    Conversely, to receive a communication signal containing an audio signal, a position signal, and two video streams A and B, the transceiver device  316  receives the communication signal from the communication channel  118  and forwards the communication signal to the communication processing engine  318 . The communication processing engine  318  then decompresses and decodes the communication signal to recover the audio signal, position signal, and two video data streams.  
         [0038]    [0038]FIG. 4 is an exemplary block diagram illustrating components of the video processing engine  310  of FIG. 3. The video processing engine  310  includes a data loading engine  402  coupled to the video sensor  212  (FIG. 2), a video memory  404 , and an FPGA/ASIC  406 . The data loading engine  402  receives video image data from the video sensor  212  and stores it into the video memory  404 , while the FPGA/ASIC  406  controls the data loading engine  402  and the video memory  404 . Because the video sensor  212  is, preferably, a high resolution digital image sensor, the video sensor  212  can generate a large amount of image data. For example, with a 3,000×2000 resolution, the video sensor  212  generates 6,000,000 pixels for an image. To increase input bandwidth, the data loading engine  402 , preferably, has six parallel data channels  1 - 6 . The FPGA/ASIC  406  is programmed to feed entire image pixels to the video memory  404  through these six parallel data channels  1 - 6 . The FPGA/ASIC  406  is also programmed to define at least two image sections (views) over the image stored in the video memory  404  with selectable resolutions, and to produce two video streams for the two image sections (views), respectively. Although the present embodiment contemplates utilizing six data channels, any number of data channels may be used by the present invention. Further, any number of image sections and corresponding video streams may be utilized in the present invention.  
         [0039]    [0039]FIG. 5 is an exemplary image section (or view) configuration in accordance with one embodiment of the present invention defined by the FPGA/ASIC  406  (FIG. 4) and viewed on the display  202  (FIG. 2). In FIG. 5, a large section A  502  defines an entire view of an image having a 700×400 resolution, while a small section B  504  defines a view having a 300×200 resolution in which a speaking participant from a remote conferencing station is displayed. Based on the image stored in the video memory  404  (FIG. 4), the FPGA/ASIC  406  scales the entire image down to a 700×400 resolution image to produce the video stream A (FIG. 3) for the large section A  502 . Subsequently, the FPGA/ASIC  406  scales the section B  504  image down to 300×200 resolution to produce the video stream B (FIG. 3). Because the image stored in the video memory  402  has a relatively high resolution, the two scaled images still present good resolution quality. Those skilled in the art will recognize that other resolutions may be utilized in the present invention.  
         [0040]    Advantageously, the present invention has the ability to generate a whole image of a conferencing site while zooming a view from any arbitrary section of the whole image. Further, because at least two video streams are produced for an image, it is possible to transmit a wide angle high resolution image including all participants at a conferencing site (e.g., section A  502 ) along with an inset zoomed view (e.g., section B  504 ) showing a particular speaking participant. Alternatively, more or fewer streams may be produced from a single image and consequently more or fewer views displayed. Therefore, the present invention can be used to replace conventional mechanical pan/tilt/zoom cameras.  
         [0041]    With current technology, a typical COMS video sensor can effectively provide approximately 65 degree view angle. In reality, a 90 degree view angle may be required. Therefore, a small, inexpensive pan motor can be used to move the COMS video sensor in the horizontal direction. However, because the movement and the resulting noise of the CMOS video sensor are relatively small, such movement and resulting noise are hardly noticeable to the conferencing participants. With the development of technology, the COMS video sensor may be able to provide a cost effective 90 degree view angle.  
         [0042]    In FIG. 6, an exemplary flowchart  600  illustrating a process for transmitting audio data in a videoconferencing system is shown. At step  610 , an audio signal is generated at a transmitting station of a first site by the plurality of microphones  214  (FIG. 2) in response to an acoustic source by converting the received sound into an electric or current signal. Next, a position signal is generated at step  620  that indicates a position of the acoustic source. Depending upon the position of the acoustic source from the transmitting station, the current signal will have a particular magnitude. The audio processing engine  312  (FIG. 3) determines the position signal based on the magnitude of the current signal. The audio and position signals are then transmitted to the communication interface  304  (FIG. 3) and then processed at step  630  by the communications processing engine  318  (FIG. 3). This processing can include compressing and encoding the audio and position signals for transmission. The audio and position signals are then transmitted through a communication channel such as an Internet, a LAN, a WAN, or any other type of network communication means at step  640  by a transceiver device. In step  650 , a transceiver device at a receiving station of a second site receives the audio and position signals. A communications processing engine processes the audio and position signals at step  660 , which may include decompressing and decoding the audio and position signals for playback. Subsequently, at step  670 , based on the position signal, one or more speakers at the receiving station are driven to play the audio signal. The position signal generated by the audio processing engine creates a more realistic video conference situation because the playback of the audio signal on one of the speakers makes it appear as if the audio signal is coming from a location of the acoustic source. The system then determines whether more video conferencing is occurring in step  680 . If the conference continues, the system repeats steps  610  though  670 .  
         [0043]    In FIG. 7, an exemplary flowchart  700  illustrating a process for transmitting high resolution images in a videoconferencing system is shown. At step  710 , a video camera or video sensor captures a high resolution image. The high resolution image is then loaded and stored from the video camera or video sensor to a video memory. Next, the images are converted to video streams in step  720 . Within the high resolution image stored in the video memory, a first and a second image section are initially defined by the transmitting station video processing engine. Subsequently, the first and second image sections are scaled to a first video stream having a first resolution and a second video stream having a second resolution. Scaling is implemented by the FPGA/ASIC  406  (FIG. 4) of the video processing engine  310  (FIG. 3), which scales the first image section to a first video stream having a 700×400 resolution and scales the second image section to a second video stream having a 300×200 resolution. Those skilled in the art will recognize that other resolutions may be utilized in the present invention, and that more or less than two image sections, and subsequently more or less than two video streams can also be utilized.  
         [0044]    At step  730 , the video streams are processed by a transmitting station communication processing engine. This processing can include encoding and compressing of the streams for transmission. Typically, the video streams are encoded and compressed to allow for faster transmission of the video data. Next, the processed video streams are sent to a receiving station through a communication channel in step  740 . The communication channel may be any packet-switched network, a circuit-switched network (such as an Asynchronous Transfer Mode (“ATM”) network), or any other network for carrying data including the well-known Internet. The communication channel may also be the Internet, an extranet, a local area network, or other networks known in the art. The video streams are then decoded and decompressed by the receiving station video processing engine and displayed on a video display of the receiving station at step  750 . The system then determines whether more video conferencing is occurring in step  760 . If the conference continues, the system repeats steps  710  though  750 . Although the transmission of audio, position, and video data are described in separate flowcharts and methods, the present invention contemplates the simultaneous or near simultaneous transmission of these data.  
         [0045]    In FIG. 8, an exemplary flowchart  800  illustrating an alternative process for transmitting a video signal in a videoconferencing system is shown. At step  810 , a video camera or video sensor captures a video image. Next, the video signal is processed by a transmitting station communication engine at step  820 . This processing can include encoding and compressing the video signal. Typically, the video streams are encoded and compressed to allow for faster transmission of the video data. At step  830 , a phase synchronization engine synchronizes a phase between the video camera and a video display output. The synchronizing of the phase between the video camera and the video display output allows for a minimization of a negative impact that can be caused by transmission delay. Specifically, if the video camera is out of phase with the video display output, participants at a receiving station may still see a user in pause at the transmitting station, even after the user at the transmitting station has begun to speak again.  
         [0046]    Next, the video signal is transmitted to the receiving station at step  840  via a communication channel. The communication channel may be any packet-switched network, a circuit-switched network (such as an Asynchronous Transfer Mode (“ATM”) network), or any other network for carrying data including the well-known Internet. The communication channel may also be the Internet, an extranet, a local area network, or other networks known in the art. Subsequently, at step  850 , the video signal is processed for display on the video display output by a receiving station communication processing engine. This processing can include decoding and decompressing the video signal. The video display output is generated in response to the decoded and decompressed video signal and displayed on a receiving station video display. The system then determines whether more video conferencing is occurring in step  860 . If the conference continues, the system repeats steps  810  though  850 .  
         [0047]    The invention has been described with reference to exemplary embodiments. Those skilled in the art will recognize that various features disclosed in connection with the embodiments may be used either individually or jointly, and that various modifications may be made and other embodiments can be used without departing from the broader scope of the invention. For example, it is to be appreciated that while the positioning apparatus of the present invention has been described with reference to a preferred implementation, those having ordinary skill in the art will recognize that the present invention may be beneficially utilized in any number of environments and implementations. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the invention as disclosed herein.