Abstract:
A wire harness apparatus for remotely accessing and controlling a number of synchronized low-cost camera nodes sharing a single cable is provided. The invention converts power, control, and video signals where necessary for long distance remote access including conversion between single-ended and differential signals. Frame synchronization is provided for multiple externally synchronizable camera nodes. A method is provided to generate address data for selection of individual uniquely addressable camera nodes. And, a method to modify the video signal driven from a camera node onto the wire harness apparatus with a code that uniquely identifies that particular camera node. The invention extends the usable range of control while maintaining the cost savings associated with the camera nodes&#39; wiring and installation.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
         [0001]    Not Applicable  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable  
         BACKGROUND OF THE INVENTION  
         [0003]    1. Field of the Invention  
           [0004]    This invention relates to video surveillance systems and more particularly to video surveillance systems using motion video camera arrays on a single wire harness.  
           [0005]    2. Description of the Related Art  
           [0006]    There are several shortcomings in the current video surveillance systems that need to be overcome before complete video coverage becomes commonplace. Generally, installation and materials cost of individual video cameras is prohibitively high to permit complete video coverage of an installation or facility to be placed under surveillance. Motion video cameras used for video surveillance generally use CCD based technology, expensive lenses and enclosures. Therefore, in one solution, cameras are strategically mounted to cover thoroughfares and sensitive areas. In a retail store, for example, a fixed mount motion video camera may be placed over the main entrance, another strategically placed to cover the cash register and countertop, and another to cover expensive or easily concealed merchandise. These placements may be foiled because line-of-sight is not ideal for a particular event, or an irregular activity occurs elsewhere in the store where coverage does not exist.  
           [0007]    In another solution, servo-controlled moveable cameras are used in which line-of-sight may be remotely altered by a human operator or tracking algorithm. Movable cameras have the ability to be steered and even zoomed into an area of interest. However, each movable camera is significantly more expensive than a number of fixed mount cameras, and generally requires a human operator.  
           [0008]    In all of the present solutions, cabling costs for each camera typically requires a power cable as well as coaxial cable for the video signals. Servo-controlled moveable cameras also require cabling to support the remote camera control interface. The cabling and mounting costs may often exceed the unit cost of individual cameras.  
           [0009]    In addition, when a number of cameras are placed, a device called a video multiplexer is typically added to the system to control and access the plurality of video signals. In current systems, a multiplexer provides cost saving benefits by allowing several cameras to share the same display and/or video recording device. However, the multiplexer does not reduce the number or cost of individual camera placements.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    A wire harness apparatus to remotely support a number of synchronized low-cost camera nodes to reduce cost associated with wiring, installation, cameras, video multiplexer and mounting is provided.  
           [0011]    In a first aspect of the present invention, a wire harness apparatus supports remote access to an array of multiple camera nodes sharing a common set of conductors on a cable. A conductor that conducts power, video, and serial control signals extends access to the array. Connected to one end of the conductor is a remote signal converter for connection to a general-purpose remote interface to access and control camera node array. The remote signal converter provides conversion between single-ended signals at the general-purpose remote interface and differential signals on conductor. Connected to other end of conductor is a local signal converter for interface to camera node array that provides conversion between differential signals at conductor and single-ended signals at camera node array.  
           [0012]    The wire harness apparatus provides frame synchronization for multiple externally synchronizable camera nodes. The local signal converter receives alternating current power input from the conductor. It then derives a frame synchronization signal from the power input for use by camera nodes. The local signal converter may also convert the alternating current power on the power conductor to provide power source for use by the camera nodes.  
           [0013]    A second aspect of the invention provides a method for using the wire harness apparatus to generate address data for selection of individual uniquely addressable camera nodes. The address data constitute either a fixed pattern or selection of individual camera nodes based on activity sensed by each camera node.  
           [0014]    In a third aspect of the invention, a method for using the wire harness apparatus to modify the video signal driven from a camera node onto the wire harness apparatus with a code that uniquely identifies that particular camera node. This modified video signal allows other devices that use the video signal to discern the source camera node of each video frame composing the video signal.  
           [0015]    Objectives, advantages, and applications of the present invention will be made apparent by the following detailed description of embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a block diagram of the wire harness apparatus connected to an array of camera nodes.  
         [0017]    [0017]FIG. 2 is a block diagram detailing the use of conductors within the cable of the wire harness apparatus of FIG. 1.  
         [0018]    [0018]FIG. 3 is a block diagram of the power and frame sync generation parts within the local signal converter of the wire harness apparatus.  
         [0019]    [0019]FIG. 4 is a block diagram of an embodiment of the local signal converter that supports node identification insertion onto the video signal.  
         [0020]    [0020]FIG. 5 is a flow chart illustrating a method of selecting camera nodes based on activity within a camera node&#39;s field of view.  
         [0021]    [0021]FIG. 6 is a flow chart illustrating a method by which node identification is inserted onto the video signal. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring to FIG. 1, the present invention extends the usable range of an array of camera nodes  10  using a wire harness apparatus  1 . The array of camera nodes  10  consists of a plurality of individual, externally synchronizable camera nodes  12 , each connected to a common cable  11 . The wire harness apparatus  1  extends the usable range of the array of camera nodes  10  by providing signal conversion for transmitting over extension cable  7  as described hereinbelow. The local converter  9  connects on one side to the array of camera nodes  10  which has single-ended signals and on the other side to one end of the extension cable  7 . The local converter  9  converts these single-ended signals to differential signals for use on the extension cable  7 . The extension cable  7  carries the differential signals to and from its other end, which is connected to the remote converter  5 . Similar to the local converter  9 , the remote converter converts the differential signals from and to the extension cable  7  to single ended signals for use at the general-purpose remote interface  3 . The general-purpose remote interface  3  may be connected to any device capable of using the video signal for display, recording, or the like. For camera selection and camera status polling, the general-purpose remote interface  3  may be connected to any device capable of transmitting and receiving a serial stream.  
         [0023]    Referring now to FIG. 2, a detail of the signals at the general-purpose remote interface  3 , the extension cable  7 , and the common cable  11  is illustrated. Starting with the general-purpose remote interface  3 , transmit and receive serial interfaces are provided. These interfaces may support the EIA RS-232C standard, or the like. Commands may be sent through the transmit serial interface for camera selection or to poll individual cameras for status. Status may then be received at the receive serial interface. The transmit and receive serial interfaces of the general-purpose remote interface  3  are converted to and from differential signals at the remote converter  5  where they are differentially sent and received at the extension cable  7 . As is well-known in the art, differential signals exhibit a higher degree of immunity to noise and are therefore more suitable when driving over longer distances. At the local end of the extension cable  7 , the differential signals are converted back once again to single-ended signals for use at the common cable  7 . It should be apparent to one skilled in the art that differential signals on the extension cable  7  is one of many signal conditioning methods that can be employed for data transmission.  
         [0024]    At any time, the common cable  11  has one and only one camera node  12  driving its video signal onto it. Starting at the video interface on the common cable  11 , the video signal is converted by the local converter  9  to be driven down the extension cable  7 . This video signal may be digital or analog. The video signal is then received at the remote converter  5  where it is then converted for use at the general-purpose interface  3 .  
         [0025]    Lastly, power may be supplied remotely at the general-purpose interface  3 . In one embodiment, alternating current (AC) power is used. Power is passed through the remote converter directly to the extension cable  7  and then to the local converter  9  where is may be converted to preferred voltages before being driven onto the common cable  11 . Alternatively, power may be supplied locally at the array of camera nodes  10 . The recommended material for the extension cable  7  uses category ‘5’ cable which is cost-effective, has adequately controlled impedance, and contains four twisted pairs of conductors.  
         [0026]    Referring to FIG. 3, a second aspect of the invention is illustrated. The local converter  9  derives frame synchronization from the AC power, which is received from the extension cable  7 . It is standard practice that AC power oscillates at or near to the frequency of the local television field rate. In the case of the North American television standard, NTSC, AC power cycles at 60 Hertz, which is nominally equivalent to the field rate. The local converter  9  receives the power input. The power converter  20  then converts the AC power to DC, which is driven onto the common cable  11 . The power converter  20  drives the power phase to the rectifier circuit  22 , which provides the frame sync signal to the common cable  11 . Power converters and rectifier circuits are well-known in the art.  
         [0027]    Referring to FIG. 4, a detail of the preferred embodiment of the local converter  9  is illustrated. On one side of the local converter  9  is a segment of the extension cable  7 . Video is sourced from either of two differential drivers  32  and  34 . In one case, the video signal is received from the common cable  11 . In the other, the video signal is received from the microprocessor  30 . The microprocessor  30  provides the selection of the source as well as the data when differential driver  34  is selected. The content of the data will be detailed below in which the method for camera node identification insertion is described. Also from the extension cable  7  are the differential transmit and receive signals. Transmit is received by a differential receiver  36  and then by the microprocessor  30  where all remote commands may be decoded before being passed to the common conductor  30 . Likewise, receive is sourced from the common conductor  11  and passed to the microprocessor  30  for decoding before being passed to the differential driver  38  for transmission to the extension cable  7 .  
         [0028]    As described above in FIG. 3, AC power, DC power and the frame sync signals are shown with their corresponding parts, the power converter  20  and the rectifier circuit  22 . In addition, frame sync is input to microprocessor  30 . The frame sync enables the microprocessor to switch the differential drivers  32  and  34  synchronous to the video signal. In addition, the frame sync input enables the microprocessor  30  to determine which camera node is currently sourcing the video from common cable  11  at any time. Details of these methods are described hereinbelow.  
         [0029]    Referring to FIG. 5, a method  400  for using the wire harness apparatus, which generates address data for selection of individual uniquely addressable camera nodes based on activity within each node&#39;s field of view, is shown. In one embodiment, the method is implemented as a program executed by microprocessor  30  within the local converter  9 . The method  400  begins with the initialization of three registers node_ctr, next_node, and max_node at step  40 . Each camera node  12  in the array of camera nodes  10  is uniquely addressable. The three registers maintain the addresses of the camera nodes  12  and for simplicity, it is assumed that adjacent nodes are addressed sequentially. The first register, node_ctr maintains the address of the current node that is being polled. The second register, next_node, maintains the value of the node to be actively driving video onto the common conductor  11  in the event that there is no activity within the field of view of any of the nodes. The third register, max_node, maintains a constant that represents the highest cardinal value node address. This node is used to determine when node_ctr and next_node have counted to the last camera node  11  in the array of camera nodes  10 .  
         [0030]    Next, the program is synchronized to the start of a new video frame at step  42 . After initialization, the method  400  is carried out once every video frame period. The node_ctr register is then loaded with the value in next_node at step  44  and the corresponding camera node is polled for activity step  46 . If there is activity, then that camera node is enabled for driving its video during the next video frame step  62  and the program loop is completed for that frame. If not, the node_ctr register is incremented step  48  so that the next camera node may be polled. If after being incremented, node_ctr is equal to next_node step  50 , then this indicates that all camera nodes  12  have been polled and there is no activity on any camera node. Therefore, in this case next_node is incremented for the next video frame step  56 , compared with max_node step  58  to insure that next_node has not exceeded its valid range. If so, next_node is reset step  60 . In either case, the next_node value is used to enable the camera node  12  for the next video frame step  62  and the program loop is complete for the current video frame.  
         [0031]    If node_ctr is not equal to next_node at step  52 , then the value of next_node is compared to determine if it is greater than the value of max_node step  52  and thus requiring next_node to be reset to represent the value of the first node in the array of camera nodes  10  at step  54 . In either case, the program then proceeds to step  46  once again to poll the next camera node  12  for activity.  
         [0032]    Although method  400  takes advantage of enabling camera nodes  11  sequentially based on activity at each camera node  11 , any sampling pattern might be implemented to enable the sequence of individual camera nodes  12  in an array of camera nodes  10 .  
         [0033]    Referring to FIG. 6, a method  500  for using the wire harness apparatus, which modifies the video signal driven from a camera node with a code that uniquely identifies that camera node is illustrated. In one embodiment, the method is implemented as a program executed by the microprocessor  30  within the local converter  9 .  
         [0034]    The method  500  begins at the start of a video frame at step  70  and executes once for each successive video frame. In step  72 , the identification of the current camera node  12  driving the common conductor  11  is received. Recall that each camera node  12  in the array of camera nodes  10  is uniquely addressable. In step  74 , the program waits for the position or positions within the video frame in which the node identification may be inserted onto the video signal in a manner nondestructive to the video data. At that point, the differential drivers  32  and  34  are disabled and then enabled respectively in steps  76  and  78 .  
         [0035]    At step  80 , the node identification for the current node camera  12  sourcing the video signal is driven into the video signal. Upon completion of this step, the differential drivers  34  and  32  are disabled and then enabled respectively in steps  82  and  84 . This modified video signal allows other devices that use the video signal to discern the source camera node of each video frame composing the video signal. It should be apparent to one skilled in the art that current injection may also be employed to modify the video signal in a like manner.  
         [0036]    It is to be understood that variations and modifications of the present invention can be made without departing from the scope of the invention. It is also to be understood that the scope of the invention is not to be interpreted as limited to the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the forgoing disclosure.