BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to a system and method for providing redundant back-up to a video transmission system, and more particularly to a video changeover switch that can switch a video signal from primary equipment to back-up equipment upon the failure of the primary equipment.  
           [0002]    A contemporary video broadcasting system is illustrated in FIG. 1. Here, video signals from multiple video sources  130  ( 130 - 1  through  130 -N) are transmitted to an editing location  105  through transmission equipment  100 . In a typical system, transmission equipment  100  encodes the video signals and then transmits them over a communication path or channel (e.g., a fiber optic or electrical channel). Finally, the signals are decoded prior to entering editing location  105 . At editing location  105 , all of the signals from video sources  130  are tested, edited and/or mixed to produce one video signal that contains the best or preferred footage from the video sources. The edited video signal is then broadcast to viewers, for example, from a broadcast site  110 . Viewers desiring to watch the broadcast receive the edited video signal with a receiver  115  and watch the broadcast with a television or other suitable video device. As one skilled in the art will appreciate, receiver  115  can be an antenna at a person&#39;s house, the TV itself, or any suitable receiver at a head-end of a cable provider.  
           [0003]    During high profile broadcasting events (e.g., the Super Bowl or the Olympics) it is important for the broadcaster to avoid any disruption in the broadcast signal. Transmission interruptions can cause embarrassment, loss of income and ill will for the broadcaster. In most systems, a critical transmission path for the video signals is through transmission equipment  100 . If transmission equipment  100  fails, the signal being broadcast to the viewers may be lost. Possible transmission equipment  100  failures include the loss of power in the encoders or decoders, failure of the encoders or decoders themselves, loss of signal in the channel due to channel failure, or the like. Thus, there is a need in the art for overcoming possible failures in transmission equipment  100  to prevent loss of the video signal to editing location  105 .  
         BRIEF SUMMARY OF THE INVENTION  
         [0004]    In accordance with one embodiment of the present invention, a system and method for providing a video delivery system with a redundant back-up is provided.  
           [0005]    A more complete understanding of the present invention may be derived by referring to the detailed description of preferred embodiments and claims when considered in connection with the figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    In the Figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.  
         [0007]    [0007]FIG. 1 is a block diagram of one embodiment of a video transmission system currently known in the art;  
         [0008]    [0008]FIG. 2 is a block diagram of one embodiment of a video transmission system, in accordance with the present invention;  
         [0009]    [0009]FIG. 3 is a block diagram of the video transmission system of FIG. 2 having a plurality of video sources; and  
         [0010]    [0010]FIG. 4 is a block diagram of one embodiment of a video protection switch that can be used in the video transmission systems of FIGS. 2 and 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    The present invention relates generally to a system and method for providing redundant back-up to a video transmission system, and more particularly to a video changeover switch that can switch a video signal from primary equipment to back-up equipment upon the failure of the primary equipment.  
         [0012]    [0012]FIG. 2 illustrates one embodiment of a video transmission system  5  in accordance with the present invention. In the illustrated embodiment, video transmission system  5  comprises a video source  10 , a first transmission path  12 - 1  and a second transmission path  12 - 2  through which the video signals from video source  10  pass, and remote from the video source  10 , a video protection switch (VPS)  30  for switching between the video signals passed over the two transmission paths.  
         [0013]    Video source  10  can be any video signal producing device, such as a video camera, a VCR, a DVD player, the Internet, a cable system, or the like. For example, while broadcasting a basketball game, a network may have several TV cameras covering the game, but only one signal typically is broadcast to the viewers at a time. Moreover, the network may use computers to generate instant replays, statistical views, player profiles, etc. Before broadcasting a signal to the viewing public, all of the signals from the various cameras, computers and other devices covering the game typically are transmitted to an editing location for signal editing, switching and/or mixing. This allows the network to produce and transmit the best footage possible for the TV broadcast.  
         [0014]    As discussed above, the video signals from video source  10  pass through two transmission paths. In one embodiment, first transmission path  12 - 1  comprises a first encoder  15 , a first transmission channel  20 - 1  and a first decoder  25 , and second transmission path  12 - 2  comprises a second encoder  16 , a second transmission channel  20 - 2  and a second decoder  26 .  
         [0015]    As one skilled in the art will appreciate, encoders  15 ,  16  can be any device that transforms the video signal from video source  10  into a signal that can be easily transmitted over a communication or transmission path. For example, encoders  15 ,  16  may convert the video signals into a compressed digital format, such as MPEG, MPEG2, or the like. Similarly, decoders  25 ,  26  typically are devices that convert the transmission signal back into a video signal. In one embodiment, encoders  15 ,  16  and decoders  25 ,  26  may comprise, for example, Digilink 1220 encoders/decoders from Artel Video Systems, Inc., Marlborough, Mass.  
         [0016]    Moreover, transmission channels  20  may comprise any suitable communication channel. In accordance with one embodiment, transmission channels  20  comprise high bandwidth fiber optic cable. As one skilled in the art will appreciate, an optical multiplexer also may be used to place more than one signal on each fiber channel, such as, for example, the MegaWav optical multiplexer from Artel Video Systems, Inc.  
         [0017]    As discussed in more detail below, video protection switch (VPS)  30  receives video signals  40  and  41  from the two transmission paths  12 - 1  and  12 - 2 , respectively, and produces a video output signal  45  from one of the two input video signals  40  or  41 . In addition, VPS  30  receives alarm signals from alarm relay outputs  35  and  36  at decoders  25  and  26 , respectively. Alarm relay output  35  sends an alarm signal to VPS  30  upon a detection of a video signal error or failure in transmission path  12 - 1  (e.g., errors introduced by encoder  15 , transmission channel  20 - 1 , or decoder  25 ), and alarm relay output  36  sends an alarm signal to VPS  30  upon a detection of a video signal error or failure in transmission path  12 - 2  such error or alarm signals are provided in conventional decoders, such as the previously mentioned Digilink 1220 encoder/decoder). As discussed below, in the event of a video signal error or failure on one of transmission paths  12 - 1 ,  12 - 2 , VPS  30  switches from the failing transmission path to the back-up or other transmission path.  
         [0018]    [0018]FIG. 3 illustrates a video transmission system  13  having a plurality of video sources  10 , each of which transmits video signals over two transmission paths in a manner similar to that in transmission system  5  in FIG. 2. Thus, in accordance with the embodiment illustrated in FIG. 3, the first transmission path for the video signal from video source  10 - 1  is first encoder  15 - 1 , first transmission channel  20 - 1  and first decoder  25 - 1 , and the second transmission path is second encoder  16 - 1 , second transmission channel  20 - 2  and second decoder  26 - 1 . Similarly, for the video signal from video source  10 -N, the first transmission path is first encoder  15 -N, first transmission channel  20 - 1  and first decoder  25 -N, and the second transmission path is second encoder  16 -N, second transmission channel  20 - 2  and second decoder  26 -N.  
         [0019]    As with the system in FIG. 2, VPS  30  generates a video output signal  45  from one of the video inputs  40 ,  41  into VPS  30  originating from each of the transmission paths. Accordingly, output signal  45 - 1  from VPS  30  is either video signal  40 - 1  originating from video source  10 - 1  and communicating through the first transmission path (encoder  15 - 1 , transmission channel  20 - 1 , and decoder  25 - 1 ) or video signal  41 - 1  communicating through the second transmission path (encoder  16 - 1 , transmission channel  20 - 2 , and decoder  26 - 1 ), depending on which path the VPS  30  is using. Similarly, output signal  45 -N from VPS  30  is either video signal  40 -N originating from video source  10 -N and passing through the first transmission path (encoder  15 -N, transmission channel  20 - 1 , and decoder  25 -N) or video signal  41 -N passing through the second transmission path (encoder  16 -N, transmission channel  20 - 2 , and decoder  26 -N).  
         [0020]    This is further illustrated in FIG. 4 which provides a more detailed illustration of one embodiment of VPS  30 . In the illustrated embodiment, VPS  30  receives input signals from two transmission paths for each video source  10 . That is, VPS  30  receives a first input signal  40 - 1  from the first transmission path for video source  10 - 1 , and a second input signal  41 - 1  from the second transmission path for video source  10 - 1 . Similarly, VPS  30  receives a first input signal  40 - 2  from the first transmission path for video source  10 - 2 , and a second input signal  41 - 2  from the second transmission path for video source  10 - 2  (and so on).  
         [0021]    In addition to receiving inputs  40 ,  41  from the two transmission paths, and more specifically from decoders  25  and  26 , VPS  30  receives alarm signals from alarm relay outputs  35  and  36  from each of decoders  25  and  26 , respectively. The alarm signals are provided to alarm controls  55  of switches  60  within VPS  30 , which in turn control which switch input  65  or  66  is connected to the outputs  45 . In the embodiment shown, VPS  30  can be pre-set so that the first input  65 - 1  is initially connected to output 1   45 - 1  by way of the switch  60 - 1 , and thus alarm control  55 - 1  is under the control of first alarm relay output  35 - 1  from decoder  25 - 1 . If there is a problem with the signal input into the decoder  25 - 1 , decoder  25 - 1  will send an alarm signal to the VPS  30  by way of alarm relay output  35 - 1 . The alarm signal causes alarm control  55 - 1  to change the state of switch  60 - 1  to connect output  45 - 1  to receive the signal from the second input  66 - 1 , and switch  60 - 1  stays in this state (i.e., input  66 - 1  provided to output  45 - 1 ) until reset. The other switches  60  operate in the same way, each connecting switch input  65  to the output  45  unless an alarm signal is received at one of the alarm relay outputs  35 .  
         [0022]    In FIG. 4, the VPS  30  is illustrated in operation after an alarm signal has been received from decoder  25 - 2 , indicating an error in the video signal from video service  10 - 2  (an error in the first transmission path-encoder  15 - 2 , channel  20 - 1 , and decoder  25 - 2 ). In that event, switch  60 - 1  remains in the first state (input  65  connected to the out  45 - 1 ), but switch  60 - 2  has received an alarm signal (from alarm relay output  35 - 2 ) and has switched to the second state (input  66 - 2  connected to output  45 - 2 ).  
         [0023]    In one embodiment, it is possible to use only the alarm relay outputs  35  (the alarm relay outputs  36  are not necessary), and each switch  60  is pre-set to connect input  65  to output  45 . If an alarm signal is present on any one of the alarm relay outputs  35 , the alarm control  55  for the corresponding switch changes to connect input signal  66  to the output  45 , and that connection continues until the switch is manually reset to the original position (i.e., connecting input signal  65  to the output  45 ). In other embodiments, the alarm relay outputs  36  may be actively used, and when any switch  60  changes to the second state (input  66  connected to output  45  by virtue of an alarm signal on alarm relay output  35 ), the switch stays in that state until an alarm signal is provided at the corresponding alarm relay output  36 . When that alarm signal from alarm relay output  36  is provided to the alarm control  55 , the switch is automatically changed back to the first state (input  65  connected to the output  45 ), without the need for a manual reset.  
         [0024]    Thus, the present invention provides means for overcoming a problem with a signal, while disrupting the transmission only momentarily, i.e. the brief switching time during which the alarm control  55  changes the one of the inputs  65  or  66  that is provided to output  45 .  
         [0025]    In the event of power failure, the state of the switches  60  are magnetically retained and the switches  60  continue to connect outputs  45  to the input signals connected before the power failure. Thus, the present invention provides a video protection switch that continues to function after power loss.  
         [0026]    The VPS  30  may also be provided with protection ports  70 - 1 ,  70 - 2  according to one preferred embodiment of the present invention seen in FIG. 4. The ports  70 - 1 ,  70 - 2  provide access to an extra or redundant switch  60 -P for connecting one of the inputs  40 ,  41  to an output  45 , in the event one of the switches  60  fails or is otherwise inoperable. Thus, if during operation it is determined that one of the outputs  45  does not output the correct signal, the inputs  40 ,  41  corresponding to that output  45  may be physically switched to protection port  70 - 1  and protection port  70 - 2 , respectively. For example, if output  45 - 2  is not outputting the correct signal due to a failure of switch  60 - 2 , inputs  40 - 2 ,  41 - 2  may be physically disconnected from input  65 - 2  and input  66 - 2 , respectively. The video signal inputs  40 - 2  and  41 - 2  may then be physically connected to protection port 1   70 - 1  and protection port  70 - 2 , respectively. Also, first alarm relay output  35 - 2  and second alarm relay output  36 - 2  (if used) are connected to alarm control  55 -P of switch  60 -P. Once connected, output  45 -P will provide the signals from either the first input  40 - 2  or the second input  41 - 2 , depending on the state of switch  60 -P.  
         [0027]    There are various modifications to the present invention that will be apparent to those of ordinary skill in the art. For instance, more redundancy may be provided by having more than two encoders and decoders per video source, the amount of channels being equal to the number of encoders and decoder per video source. The VPS  30  could be modified to allow for more inputs per output to increase to the redundancy of the system. For example, three encoders and decoders per video source may be provided with three channels to carry the signals. The VPS  30  would be modified to have three inputs per output and to receive three alarm relay outputs from the decoders.  
         [0028]    Further, the VPS  30  can provide an external reset switch for each switch  60  individually (or all switches  60 , collectively) so that the switches  60  may be reset manually at any time (reset to their original, pre-set state).  
         [0029]    In conclusion, the present invention provides novel systems and methods for providing redundant back-up of a video transmission system. While detailed descriptions of one or more embodiments of the invention have been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art without varying from the spirit of the invention. Therefore, the above description should not be taken as limiting the scope of the invention, which is defined by the appended claims.
A system and method for providing video signals wherein the video signals from a single video source may be separately passed over two different transmission paths. Each transmission path includes an encoder, a communications channel and a decoder. The output of each communications path at the decoder provides the video signals and an alarm signal. The alarm signal indicates an error or disruption of the video signals over the corresponding communications path. The outputted video and alarm signals are provided to a video protection switch (VPS) device which provides the video signal from the second transmission path if the alarm signals indicates an error or disruption in the first transmission path. In one embodiment, the VPS has multiple switches, one for each of plural video sources, and a redundant switch and protection ports. The redundant switch and protection ports may be connected to receive the video and alarm signals if one of the switches in the VPS fails.