Patent Publication Number: US-9413982-B2

Title: System and method for video frame sequence control

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a U.S. National Stage Application of and claims priority to International Patent Application No. PCT/US2012/027004, filed on Feb. 28, 2012, and entitled “SYSTEM AND METHOD FOR VIDEO FRAME SEQUENCE CONTROL”. 
     BACKGROUND 
     When displaying a projected image and simultaneously capturing images of the projected scene and the display, there can be crosstalk between the projected images and the captured content. The crosstalk can reduce the image quality (i.e. brightness, color) of the captured image frames and additionally cause distracting flicker on the display. Various attempts have been made to reduce crosstalk in the projection/image capture systems. For example, the display may be changed from a passive screen display screen an active switchable diffuser to reduce crosstalk. However, although crosstalk may be reduced when using the active switchable diffuser for the display, an active diffuser display screen can limit the useful duty cycle of both the projector and the image capture device used in the system. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The figures depict implementations/embodiments of the invention and not the invention itself. Some embodiments are described, by way of example, with respect to the following Figures. 
         FIG. 1  shows a schematic drawing of a video sequence control system with binary modulation according to an example of the invention; 
         FIG. 2  shows the video sequence control system shown in  FIG. 1  where the video frame sequence frames produced and output by the video sequence control system is displayed on a see-through display screen according to an example of the invention; 
         FIG. 3A  shows a schematic drawing of a video sequence control system with spatial masking and modulation having a first modulation pattern according to an example of the invention; 
         FIG. 3B  shows a schematic drawing of a video sequence control system with spatial masking and modulation having a second modulation pattern according to an example of the invention; 
         FIG. 3C  shows a schematic drawing of a video sequence control system with spatial masking and modulation having a third modulation pattern according to an example of the invention; 
         FIG. 3D  shows a schematic drawing of a video sequence control system with spatial masking and modulation having a fourth modulation pattern according to an example of the invention; 
         FIG. 4  shows a schematic drawing of a video sequence control system according to an example of the invention; 
         FIG. 5  shows a flow diagram for a method for controlling the output of a video sequence according to an example of the invention; 
         FIG. 6  shows a computer system for implementing the method shown in  FIG. 5  described in accordance with examples of the present invention. 
     
    
    
     The drawings referred to in this Brief Description should not be understood as being drawn to scale unless specifically noted. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     For simplicity and illustrative purposes, the principles of the embodiments are described by referring mainly to examples thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one of ordinary skill in the art, that the embodiments may be practiced without limitation to these specific details. Also, different embodiments may be used together. In some instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description of the embodiments. 
     The application describes a video sequence control system  100  comprising: an input video frame buffer  102  for receiving a video stream  104  of video frames  106  from a video source  110 ; and an output video frame selection component  112  for determining a video frame to be output according to a scheduler  116  that provides timing information  118  and modulation information  119 , wherein the timing information  118  includes information regarding when each video frame will be output, wherein modulation information varies dependent upon frame type to be output, wherein frame type includes at least the image frames from the input video frame buffer and functional frames, wherein the at least the image frames and functional frames are output according to a pattern defined by the scheduler, wherein based on the timing information  118  a synchronization output signal  124  is output corresponding to the output of the functional frame. 
     The video sequence controller takes a video stream input from a video source and outputs a (1) modified video stream and (2) a synchronization output signal. Referring to  FIG. 2 , the video sequence control system  100  receives a video stream  104  from the video source at a first rate. The video sequence controller  100  receives the input video stream, modifies the video stream and outputs the modified video stream  136  at a second frame rate. In one example, the modification of the video stream occurs based on a schedule  117  that details the insertion a functional video frame into the output video stream  136 . 
     Whether an input frame or other frame is modified to create the video output stream and how frames slotted for modification are changed is dependent upon frame type. At least two frame types are available for output, including input video frames and functional frames. Input video frames refer to the input video that are not modified and directly output in the output video frame sequence. The functional frames are frames other than the input video frames. The functional video frames often have a purpose other than the output of video images. For example, in the implementation described in  FIGS. 1, 2 and 3A  the functional video frames are crosstalk reduction frames. The crosstalk reduction frames are added for the purpose of reducing crosstalk in the system in order to improve image quality. In the example shown in  FIGS. 3B and 3D , the functional frames are color channel varying frames. In one example, the purpose of varying the color channel is to add color channel varying frames to the output video stream to facilitate green-screening. Throughout the application, the term functional frame and the alternative functional description of the frame (i.e., crosstalk reduction frame, color channel varying frame) may be used interchangeably according to the implementation. 
       FIG. 1  shows a schematic drawing of a video sequence control system  100  according to an example of the invention. The video sequence control system includes an input video frame buffer  102  for receiving a video stream  104  of video frames  106  from a video source  110 . Various sources may be used for the generating the input video stream  104 . For example, video could originate from video streamed from the network. In another example, the video source could be a graphics adapter in a computing device. In another example, the video source could be a video camera that inputs the captured images to the graphics adapter in a computing device. 
     Referring to  FIG. 1 , the video sequence control system  100  includes an output video frame selection component  112  for determining the video frame to be output according to a scheduler  116 . In one example, the output video frame selection component  112  includes a modulation component  114  that modifies the input video stream that is coupled to a scheduler  116 . Timing information  118  is used by the output selection component  112  to determine the timing of when video frames are output. Modulation information  119  in the scheduler  116  can be used by the modulation component  114  to determine whether the input video frame needs to be modified and if the video frame needs to be modified which input video frames are modified and how the video input frames selected for modification are modified before being output. 
     For the example shown in  FIG. 1 , how the input video stream is modified and the resultant video stream output is dependent upon the output video frame selector schedule  117 . Referring to  FIG. 1  shows a visual representation  115  of the video frame output schedule  117 . In the example shown in  FIG. 1 , the output video frame selection component  112  can be described as a binary modulator. In one implementation of a binary modulator, the number 1 can be representative of the image frame and the number 0 can be representative of the black crosstalk reduction frame. Alternatively, the number 1 can be representative of a black crosstalk reduction frame and the number 0 can be representative of the input image frame. In one example, the arrow  126  represents a schedule pointer that points to a frame that is under consideration (to be modified/output) according to the output video frame schedule  117 . 
     Assume for purposes of example, that the number 0 in the schedule is representative of an image frame and that the number 1 is representative of the black crosstalk reduction frame. In the example shown in  FIG. 1 , when the pointer of the selection component points to an image frame (represented by a 0 in the schedule), the output video frame selection component  112  selects an image frame for output. However, for the case where the pointer is pointing to the functional frame (the crosstalk reduction frame) in the schedule, the modulator changes the image in the input file according to the modification information in the schedule. Referring to  FIG. 1  where the modulation schedule specifies a black crosstalk video frame—the modulator modifies the image component frame so that the pixels in the image frame are black. The selection component then outputs the modified image frame. 
     In an alternative example, instead of the modulator modifying each pixel of the corresponding image frame, a software or hardware implemented representation of the crosstalk reduction frame is used. For example, say for a black (crosstalk reduction) frame is required for every pixel in the video frame. The pixel value of zero could be stored and the value repeated for each pixel location in the video frame when a black frame is present on the schedule. For this case, the entire image frame may not need to be stored. In one case a single pixel value is stored. The timing information in the schedule can be used to determine when the crosstalk reduction frame is to be output. When the crosstalk reduction frame is output, the pixel value of zero is repeated for every pixel in the frame. 
     The scheduler  116  of the output video frame selection component  112  includes timing information  118  and modulation information  119 . In one example, the timing information  118  includes information regarding when each video frame will be output. For example, timing information  119  includes information about the number of frames to be output within a certain time period and when each frame in the scheduled sequence of video frames will be output. In one example, the scheduler determines the output sequence of the video frames at least in part based on the of the frame rate of the video input and the required video output. Thus for example, if the frame rate of the video source is 30 Hz and the required video output is 120 Hz, then for each video input image frame—four video frames are output. In the example shown in  FIG. 1 , the schedule  117  alternates between image frames (frames  130  and  134 ) and crosstalk reduction frames (frames  128  and  132 ). Thus for each image frame in the video input buffer a crosstalk reduction frame is output. This pattern (alternating image and crosstalk frames) is illustrated in the virtual representation  115  of the schedule and the corresponding video output sequence  136 . The video frames are output at equal time periods. Thus, for a 120 Hz output, a frame is output every 0.25 seconds. 
     Referring to  FIG. 1 , the video sequence control system  100  receives the video source input at a first frame rate and outputs a modified video stream at a second frame rate. In one example, where the video sequence control system  100  is outputting video at a higher frame rate than the video input, the video output video frame selection component  112  repeats unmodified input image frames  106  and inserts the unmodified image frames into the output video stream  136  to accomplish the required frame rate. Where the video sequence control system  100  is outputting video at the same frame rate than the input video or lower, in one example frames are dropped (lower frame rate) or alternatively some of the existing frames (i.e. same frame rate) are dimmed. In one example, by dimmed we mean that the functional (i.e. crosstalk reduction frame) has an intensity lower than the corresponding input image frames in the same video sequence. The dimmed image can be a reduced intensity version of the black frame (i.e. a gray frame) or alternatively, a dimmed version of the image frame. 
     The frame rate and the video sequence pattern (sequence of frame types) effects whether the input video frames are dropped, inserted or remain the same in the output video frames  136 . For the video sequence pattern shown in the visual representation of the schedule  117  in  FIG. 1  for example, the schedule pattern includes an alternating sequence of image video frames from the input video stream  104  and crosstalk reduction frames, where the crosstalk are dimmed (black) video frames. If the input video streams and output video streams are both 60 Hz, then in one example, half of the video input frames could be modified (dimmed) to provide the video sequence pattern (alternating image and crosstalk reduction frames) shown on the visual representation  115  of the schedule. 
     In one example, the scheduler  116  includes frame type information  120 , that provides information regarding the type of video frame that is currently being processed (the video frame in the visual representation of the schedule that the pointer  126  is pointing to.) In one example, the scheduled frame types include at least crosstalk reduction frame types and image frame types. In one example, modification information is associated with the frame type information to provide information on whether the frame type is selected for output with no modification or whether the frame type is modified. Further, if the frame type is to be modified—how each frame type is modified. For example, if the frame type is a crosstalk reduction frame—the image frame might be modified to be a uniform black frame, where the black frame is output in the output video stream for display. 
     In one example, the scheduler  117  of the output video frame selection component  112  includes modification information  119 , timing information  118 , frame type information  120 , and sequence order information  122  which the scheduler  117  uses to determine whether input image frames are modified, how the input frames are modified, when the modified or unmodified frames are output, and the sequence order that the frame types are output. In one example, the sequence order information  112  provides information to the modification component  114  of the order and frame type that the video frames are output. In the example shown in  FIG. 1 , the output video sequence can be described generally as at least one crosstalk reduction from followed by a sequence of n image frames. In the example shown in  FIG. 1 , the repetitive pattern  138  is a pattern of alternating crosstalk reduction frames and image frames. However, the output video sequence could be different dependent upon the desired output and results. For example, the video sequence could be a crosstalk reduction frame followed by three image frames. This video sequence may be preferred where the video sequence is displayed as the increased number of image frames in the sequence compared to the first example (single crosstalk reduction frame followed by a single image frame), improves the quality of the displayed image. 
     In one example, the timing information  118  provides information regarding when and how often the selected (where schedule pointer  126  is currently pointing to) video frame is output. In one example, the timing information  118  is used to determine when a synchronization output signal  124  is output. The synchronization output signal  124  should correspond to the timing of the output of the crosstalk reduction frame. 
       FIG. 2  shows the video sequence control system shown in  FIG. 1  where the output video frame sequence frames are displayed on a see-through display screen  150  according to an example of the invention. In the example shown in  FIG. 2  the video sequence control system  100  outputs a video frame sequence  136  to the projector  148  that drives the display  150 . The video sequence control system  110  outputs a synchronization output signal  124  to the image capture device  146  to signal to the image capture device  146  when image capture of the scene should occur. 
     The video sequence control system  100  acts as a specialized video processor. It can modify frame rate by inserting or removing frames and can modify image frames. In one example, the video sequence control system is a standalone device positioned between the video source  110  and the devices that it is outputting video frames and/or synchronization signals to. For example, in  FIG. 2  the video sequence control system  100  is positioned between the video source  110  and the projector  148 . Also, the video sequence control system  100  is positioned between the video source  110  and the video camera  146 . 
     In one example, the crosstalk reduction frame  112  is a dimmed or reduced intensity frame, by dimmed or reduced intensity we mean the crosstalk reduction frame has an intensity lower than the corresponding image frames in the same video sequence. In the example shown in  FIG. 2 , the crosstalk reduction frames are black frames. The purpose of the lower intensity video frame is to provide a time interval when the image capture device  120  is capturing a video frame image of the scene behind the see-through display screen which minimizes the interference or crosstalk caused by the projected image. 
     In the example shown in  FIG. 2 , the video frame output  136  is projected onto a display screen  150  by a projector  148 . In one example, the display is a see-through display screen  150  comprised of a relatively low concentration of diffusing particles embedded within a transparent screen medium. The low concentration of diffusing particles allows a camera  146  or other image capture device to capture an image through the screen  150  (providing that the subject is well lit), while diffusing enough of the light from the projector  148  to form an image on the display screen. In another example, the display screen  150  can be a holographic film that has been configured to accept light from the projector  148  within a first range of angles and to transmit light that is visible to the remote participant within a different range of viewing angles. The holographic film is otherwise transparent. In both examples, light projected onto the first surface  156  within the first range of angles can be observed by viewing the second surface  158 , but light striking the second surface  158  is transmitted through the screen to the camera. In both examples the camera also captures light from the projector diffused or scattered off of the first surface. 
     In the example shown in  FIG. 2 , the output crosstalk reduction frames (e.g.  142   a ,  142   b ) are black frames (no light output) which simulates the projector  108  being in an off state. In one example, the image capture device  146  is a video camera. The video camera is synchronized to capture an image during the time period when the crosstalk reduction frame is being displayed. For the case where there is a see-through display screen, the video camera  146  captures the scene in front of the display screen, the display and the scene behind the see-through display screen. Thus, for a video conferencing example where there is a participant  152  on the other side of the display screen—the video camera  146  captures the image of the participant on the other side of the display screen. Because the projector is off when the image is captured, the camera does not capture the projected image. 
     Referring to  FIG. 2 , the video sequence control system  100  produces a synchronization output signal  124 . The synchronization output signal  124  is communicatively coupled to an image capture device  146  and is used to provide a signal to the image capture device  146  related to the occurrence of the at least one crosstalk reduction frame (e.g.  142   a ,  142   b ). The synchronization output signal  124  is used to trigger image acquisition by the image capture device in order to capture an image when a crosstalk reduction frame  142  is being projected. 
     In one example, the synchronization output signal  124  is directly coupled to the image capture device  146 . In the example shown in  FIG. 2 , the image capture device is communicatively coupled to the synchronization output signal via an optional signal converter  154 . In one example, the signal converter could reduce the frequency of the synchronization trigger frequency. In another example, a image capture device  146  might require a specific signal pattern that follows an industry standard protocol. For this case, the signal converter  154  could translate a simple triggering synchronization output signal  124  to the pattern according to industry standard protocol. 
     In one example, the synchronization output signal  124  provides both a synchronization signal and a command signal to the image capture device  146 . In one example, the synchronization output signal  124  provides information to the image capture device of when the crosstalk reduction frame is being projected. The command signal line can provide information to the image capture device of what camera function is to perform. In one example, the command signal to the image capture device provides a command to the image capture device to open or close its shutter. In the example shown in  FIG. 2 , the timing of the image acquisition is done in synchronization with the projection of the crosstalk reduction frame. 
     In one example, a synchronization output signal  124  is sent to the image capture device  146  to instruct it to open its shutter (take a picture) when the crosstalk rejection frames are projected onto the display screen. For example, assuming the black crosstalk reduction frame  142   a  is projected at a time t proj1 . Then the camera opens its shutter at this time, captures an image and outputs a corresponding photograph  160   a . The corresponding photograph is of the display, the scene in front of the display and for the case of a see-through screen, the viewer behind the display screen. Similarly assuming a second black crosstalk rejection frame  142   b  is projected at time t proj2 , then the camera opens its shutter at this time, captures an image and outputs the corresponding photograph  160   b.    
       FIG. 3A  shows a schematic drawing of a video sequence control system shown in  FIG. 1  with an alternative modulation pattern according to the schedule. The modulation component  114  of the video sequence control system  100  takes an input video and generates output video by dropping video frames, repeating video frames, or inserting dimmed, masked or otherwise modulated images. Similar to the example shown in  FIG. 1 , the modulation pattern shown in the visual representation of the schedule in  FIG. 3A  alternates between the image frame and a crosstalk reduction frame. However, instead of a black crosstalk reduction as shown in  FIG. 1 —the crosstalk reduction frame in  FIG. 3A  is modulated to output a gray frame. 
     In one example, instead of the crosstalk reduction frame having the highest possible darkness or intensity value (100%)—a black frame, a dimmed image may be implemented. For example, a gray image having some percentage of the possible intensity range. For example, the gray crosstalk reduction frame could have an intensity of 50%. In another example, the dimming can be applied at continuous varying levels. For example, the modified output video could consist of modulated versions of the input video frames where the modulated versions of the input video frames are at 75%, 50% and 25% of the intensity of the input image. 
     In another example, the darkness of the crosstalk reduction frame might be reduced from its highest possible intensity (black) to a lower intensity level. One case where this might be a reasonable option would be the case where the projected image frames are likely to be very bright. For the case where the projected images go between a very bright projected image to a black video frame (the crosstalk reduction frame), the high amount of change between the two projected images that the human eye perceives—increases the perception of flashing and flicker. To reduce this effect, in one example, the crosstalk reduction frame color could be changed from black to a gray color (lower intensity value.) In another example, where the display screen is not bright (in some cases where a see-through display is used), it is not necessary to have the crosstalk reduction frame be completely black in order to substantially reduce crosstalk. In one example, fully software-controllable dimming allows crosstalk reduction to be turned on/off or to vary continuously between zero and full. In the example shown in  FIG. 1 , the crosstalk reduction frame  112  is a black frame (uniform distribution of black pixels across the video frame.) In another example, the color or intensity value of pixels can be applied in a spatially varying fashion across the modulated frame. 
       FIG. 3B  shows a schematic drawing of the video sequence control system  100  shown in  FIG. 3A  having a second alternative modulation (or masking) pattern. Both the modulation pattern shown in  FIGS. 3A and 3B  apply dimming to the video frame according to the schedule  117 , however, the image frames are modulated according to a schedule that applies dimming to each color channel of the multichannel input video frames. In one example, dimming can be applied uniformly to each color channel. In another example, dimming can be applied at a different level to each color channel. In another example, dimming can also be applied differently to each channel of multi-channel video frames. For example, in one implementation dimming could be applied only to the red channel of the video frames. 
     One potential application of the video output sequence  100  shown in  FIG. 3B  is to use the video output to effectively perform “green-screening” techniques using the video output frames. Assume for purposes of example, the video sequence control system  100  shown in  FIG. 2  where the video sequence control system outputs a video output sequence  136  on a display screen  150 . In one example, assume that the display screen  150  is opaque and that a weatherman is standing in front of the display screen while a video camera is capturing the weatherman standing in front of a green display screen. Previous use of the green-screening techniques may have been to cut out the image of the weatherman and recomposite the weatherman in front of a weather map afterwards. However, it may be desirable for the weatherman to be able to see the display as a TV viewer would see it—instead of seeing a green display screen. 
     In one example, instead of taking video of the weatherman standing in front of a green screen display, the weatherman is photographed standing in front of a weather map. The modulation pattern shown in the schedule in  FIG. 3B , for example, could be implemented by scheduling a green channel in one time slot (frame  128 ). The image of the weatherman could be captured against the green channel and in the next time slot the image of the weatherman could be captured against the combined blue and red color channel (frame  130 ). In the first time slot, the video camera captures an image of the weatherman in front of the green backdrop. In the second time slot, the camera captures an image of the weatherman in front of a combined blue and red backdrop. As long as frame rate of the video output is sufficiently high, the viewer&#39;s eyes average the green, blue and red channels so that the viewer sees a full color weather map. 
     In image processing, there are advantages to using more than one color channel background—for example when you are trying to subtract out a person standing in front of a background. In one example, the image is modulated to present different color video frames that can be used as different backdrops when performing image processing. For example, if an image is captured of a person against a black background and the person is wearing a black jacket—the black jacket will not show up well in the captured image. However, if an image of the same person is against a green background—the black jacket will show up. Alternating image capture against at least two substantially different color backgrounds—means no matter what color the person is wearing, for example, it will be easy to determine all of the colors in the image. 
       FIG. 3C  shows a schematic drawing of the video sequence control system  100  shown in  FIG. 3A  having a third alternative modulation pattern. In the example shown in  FIG. 3C , the video frame output  136  is comprised of modulated image frames where the modulation occurs according to a schedule  117  that has a pattern that varies in a spatially varying manner. In the example shown in  FIG. 3C , the third modulation pattern shown in the visual representation  115  of the schedule  117  is a crescent shaped pattern that is used as a mask to create a crescent shaped pattern on the input image frame. In one example, the mask is used to perform both spatial masking and color channel masking. For example, for the pattern shown in  FIG. 3C , the crescent shaped area could be green while the areas outside of the crescent shape could be blue. 
     Although the shape in  FIG. 3C  is a crescent shape, other shapes and patterns could be used. For example, referring to  FIG. 3D  the schedule  117  shows a modulation pattern that instead of dividing the frame into crescent shaped regions—divides each frame into four rectangular regions.  FIG. 3D  shows a schematic drawing of a video sequence control system shown in  FIG. 3A  having a fourth alternative modulation pattern. In the example shown in  FIG. 3D , each of the four rectangular regions  128   a - d ,  130   a - d ,  132   a - d  and  134   a - d  have two different color channels—two rectangular regions having a red color channel (represented by the letter “R”) and two rectangular regions having a combined green+blue color channel (represented by the letters G+B). In the example shown in  FIG. 3D , two sequential frames alternate color patterns so that similar to the example described with respect to  FIG. 3B , the color patterns alternate to provide all of the colors (RGB) within two sequential frames—so that the viewer sees the full color palate. 
     For purposes of example, consider the two sequential video frames in the schedule video frames  128  and  130 . Each of the video frames in the schedules has four rectangular regions  128   a - 128   d  and  130   a - 130   d . Each of sequential video frames have two rectangular regions having a red color channel ( 128   b ,  128   c  and  130   a ,  130   d ) and two rectangular regions having a combined green+blue color channel ( 128   a ,  128   d  and  130   a ,  130   d ). The color patterns of the two sequential video frames alternate—for example, if the color channel is red in video frame  128 , it is combined green+blue in video frame  130  and vice versa. Thus, video frame region  128   b  is red and in its next (sequential) video frame the video frame region  130   b  is combined+blue. Similarly, video frame region  128   a  is green+blue, while the corresponding sequential video frame  130   a  is red. Similar to the alternating color channel video frames in  FIG. 3B , the result of the pattern of alternating regions in the video frames video is that the viewer of the video output sequence  136  sees the full color palate of the input video frame images  104 . 
       FIG. 4  shows a schematic drawing of a time multiplex control system with binary modulation according to an example of the invention. Similar to the configuration shown in  FIG. 1 , the configuration shown in  FIG. 3  includes an input video frame buffer  102  for receiving a video stream  104  of input video frames  106  from a video source  110  and an output selection component  112  for determining video frames to be output according to a schedule. However, instead of the output selection component  112  being implemented using a modulator for modifying the input video stream, the output selection component is implemented using a multiplexer that selects the appropriate input from either the input video frame buffer  102  or the crosstalk reduction buffer  108 . In contrast to the implementation shown in  FIG. 1  which modifies the input video stream to create a desired crosstalk reduction video frame, the implementation shown in  FIG. 4  stores the desired crosstalk reduction video frames in a crosstalk buffer. Thus, compared to the configuration shown in  FIG. 1 , a crosstalk reduction frame buffer is added in  FIG. 4 . 
     Referring to  FIG. 4 , in one example the output selection component  112  includes a multiplexer  114  which selects a particular frame type for output. The multiplexer has as possible inputs: video frames from the input frame buffer  102  or crosstalk reduction frames from the crosstalk reduction frame buffer  108 . Based on the schedule  115 , the multiplexer  114  chooses which video frame from which input buffer (input frame buffer or crosstalk reduction buffer) will be selected for output. In one example, the multiplexer  114  is implemented in hardware, software or a combination of the two. 
       FIG. 5  shows a flow diagram for a method for controlling the output of a video sequence according to an example of the invention. The method includes the steps of: receiving a sequence of input video frames from a video source (step  510 ); determining when to output the input video frames from timing information provided to a scheduler  116  of the output selection component (step  520 ); determining whether the input video frames will be modified based on scheduler modulation information, wherein modulation information varies dependent upon the frame types available to be output, wherein the available frame types include at least image frames from the input video frame buffer  102  and crosstalk reduction frames (step  530 ); outputting the at least input video frames and modified crosstalk reduction frames according to the scheduler (step  540 ); and outputting an synchronization output signal  124 , wherein the synchronization output signal corresponds to the crosstalk reduction frame (step  550 ). 
       FIG. 6  shows a computer system for implementing the methods shown in  FIGS. 5A and 5B  and described in accordance with the examples herein. The computing apparatus  600  includes one or more processor(s)  602  that may implement or execute some or all of the steps described in the method  400 . Commands and data from the processor  602  are communicated over a communication bus  604 . The computing apparatus  600  also includes a main memory  606 , such as a random access memory (RAM), where the program code for the processor  602 , may be executed during runtime, and a secondary memory  608 . The secondary memory  608  includes, for example, one or more hard drives  610  and/or a removable storage drive  612 , representing a removable flash memory card, etc., where a copy of the program code for the method  400  may be stored. The removable storage drive  612  reads from and/or writes to a removable storage unit  614  in a well-known manner. 
     These methods, functions and other steps described may be embodied as machine readable instructions stored on one or more computer readable mediums, which may be non-transitory. Exemplary non-transitory computer readable storage devices that may be used to implement the present invention include but are not limited to conventional computer system RAM, ROM, EPROM, EEPROM and magnetic or optical disks or tapes. Concrete examples of the foregoing include distribution of the programs on a CD ROM or via Internet download. In a sense, the Internet itself is a computer readable medium. The same is true of computer networks in general. It is therefore to be understood that any interfacing device and/or system capable of executing the functions of the above-described examples are encompassed by the present invention. 
     Although shown stored on main memory  606 , any of the memory components described  606 ,  608 ,  614  may also store an operating system  630 , such as Mac OS, MS Windows, Unix, or Linux; network applications  632 ; and a display controller component  630 . The operating system  630  may be multi-participant, multiprocessing, multitasking, multithreading, real-time and the like. The operating system  630  may also perform basic tasks such as recognizing input from input devices, such as a keyboard or a keypad; sending output to the display  620 ; controlling peripheral devices, such as disk drives, printers, image capture device; and managing traffic on the one or more buses  604 . The network applications  632  includes various components for establishing and maintaining network connections, such as software for implementing communication protocols including TCP/IP, HTTP, Ethernet. USB, and FireWire. 
     The computing apparatus  600  may also include an input devices  616 , such as a keyboard, a keypad, functional keys, etc., a pointing device, such as a tracking ball, cursors, mouse  618 , etc., and a display(s)  620 . A display adaptor  622  may interface with the communication bus  604  and the display  620  and may receive display data from the processor  602  and convert the display data into display commands for the display  620 . 
     The processor(s)  602  may communicate over a network, for instance, a cellular network, the Internet, LAN, etc., through one or more network interfaces  624  such as a Local Area Network LAN, a wireless 402.11x LAN, a 3G mobile WAN or a WiMax WAN. In addition, an interface  626  may be used to receive an image or sequence of images from imaging components  628 , such as the image capture device. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. The foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive of or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations are possible in view of the above teachings. The embodiments are shown and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents: