Abstract:
A camera system having a plurality of camera pairs is provided. Each pair may have a camera control unit and a camera head unit respectively connected together by way of an asynchronous transmission network. The camera system may also have a central processing unit configured to obtain a video signal delay amount, representative of a time delay between a respective camera control unit and its respective camera head unit, for each of the plurality of camera pairs, and to adjust the video signal delay amount between at least one said camera control unit and its respective camera head unit to be equal to a selected video signal delay amount of another said camera control unit and its respective camera head unit.

Description:
TECHNICAL FIELD 
       [0001]    1. Cross-Reference to Related Application 
         [0002]    The present application claims priority from Japanese Patent Application No. JP 2010-082340 filed in the Japanese Patent Office on Mar. 31, 2010, the entire content of which is incorporated herein by reference. 
         [0003]    2. Technical Field 
         [0004]    The present invention relates to a camera system, a signal delay amount adjusting method and a program. 
       BACKGROUND ART 
       [0005]    Patent Literature 1 below has disclosed, for example, a camera control apparatus capable of controlling a plurality of cameras by one unit thereof. Patent Literature 1 has disclosed a configuration in which a CHU and a CCU are connected via a camera cable on a one-to-one basis to transmit reference signals and video signals. 
         [0006]    Further, Patent Literature 2 below has disclosed a method using an asynchronous switching network (an asynchronous transmission network) for transmitting between the CHU and the CCU. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1: Japanese Unexamined Patent Application Publication No. 09-238277 
         PTL 2: Japanese Unexamined Patent Application Publication No. 2004-304809 
       
     
       SUMMARY 
       [0009]    In an aspect of the invention, a camera system having a plurality of camera pairs is provided. Each pair may have a camera control unit and a camera head unit respectively connected together by way of an asynchronous transmission network. The camera system may also have a central processing unit configured to obtain a video signal delay amount, representative of a time delay between a respective camera control unit and its respective camera head unit, for each of the plurality of camera pairs, and to adjust the video signal delay amount between at least one said camera control unit and its respective camera head unit to be equal to a selected video signal delay amount of another said camera control unit and its respective camera head unit. 
         [0010]    In another aspect of the invention, a signal delay amount adjustment method is provided. Such method may include obtaining a video signal delay amount for each of a plurality of camera control units respectively connected to a plurality of camera head units via an asynchronous transmission network, such that each camera control unit is connected to a respective camera head unit via the asynchronous transmission network, in which a respective video signal time delay is representative of a time delay between a respective camera control unit and its respective camera head unit. The method may further include adjusting the video signal delay amount between one said camera control unit and its respective camera head unit to be equal to a selected video signal delay amount of another said camera control unit and its respective camera head unit. 
         [0011]    In a further aspect of the invention, a video camera system having a plurality of camera pairs is provided. Each pair may have a camera control unit and a camera head unit connected via an asynchronous transmission network, in which each said camera head unit has a video buffer. The video camera system may also have a central processing unit configured: to obtain a signal delay time for each of the plurality of camera pairs so as to obtain a plurality of signal delay times; to select a largest signal delay time from the plurality of signal delay times; to determine if the largest signal delay time exceeds a predetermined allowable time; to obtain a video buffer size that corresponds to the largest signal delay time, when a determination result indicates that the largest signal delay time does not exceed the predetermined allowable time; and to adjust a size of the video buffer of at least one of the camera head units to the obtained video buffer size. 
         [0012]    In yet a further aspect of the invention, a camera control unit is provided. The camera control unit may have a network interface that enables communication to a corresponding camera head unit via an asynchronous transmission network, in which the camera control unit and the corresponding camera head unit form a camera pair and in which the network interface also enables communication with a number of other camera pairs via the asynchronous transmission network, each of the number of other camera pairs having a respective camera control unit in communication with its camera head unit. The camera control unit may also have a central processing unit configured to obtain video signal delay amounts representative of respective time delays of the camera pair and each of the number of other camera pairs, each time delay being indicative of the time delay between a respective camera control unit and its corresponding camera head unit. The central processing unit may also be configured to adjust a video signal delay amount for at least one pair of the number of other camera pairs and the camera pair to be equal to a selected one of the obtained video signal delay amounts. 
         [0013]    When a video transmission is performed using the asynchronous transmission network as described in the Patent Literature 2, a transmission path varies for each combination of each of the CHU and the CCU, and therefore, a delay amount will be varied. For this reason, it is necessary to align arrival timing of video signals in each of the CCU by adjusting timing. Especially, since a route path is not fixed on the asynchronous transmission network and the route path varies depending on the situation, it is difficult to adjust timing of the video signals. 
         [0014]    Moreover, since a development of a camera system increases flexibility in case of the asynchronous transmission network, it is preferable that switching an asynchronous transmission wire such as a LAN cable, or a device such as a switching hub, a router, or the like, for example, can be flexibly accepted. In such case, adjusting timing of the video signals will be difficult. 
         [0015]    Further, by using the asynchronous transmission network, when a failure occurs on the route path currently in use, there is an advantage in developing a redundant configuration against the failure on a transmission device by changing into a different route path, however, it is also necessary to adjust the timing of the video signals in a flexible way according to the change of the route path. 
         [0016]    Further, due to a bandwidth limitation of the asynchronous transmission network, it is assumed that transmission may be performed after a video compression (encoding) in the CHU to compress (decoding) the compressed image in the CCU. In this case, it is necessary to consider a delay due to the encoding and decoding, accompanying with complicated processing for adjusting timing. 
         [0017]    In light of the foregoing, it is desirable to provide a camera system, a signal delay amount adjusting method, and a program, which are novel and improved, and which are capable of easily adjusting timing of video signals when a plurality of cameras are connected via an asynchronous transmission network. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a block diagram for illustrating a camera control system in which a camera (CHU) and a CCU are connected in a one-to-one basis. 
           [0019]      FIG. 2  is a schematic view for illustrating an example of a camera system using an asynchronous transmission network according to an embodiment of the present invention. 
           [0020]      FIG. 3  is a schematic view for illustrating the system illustrated in  FIG. 2  in more detail. 
           [0021]      FIG. 4  is a schematic view for illustrating a configuration for adjusting a delay amount in detail. 
           [0022]      FIG. 5  is a schematic view for illustrating a configuration for adjusting a delay amount in detail. 
           [0023]      FIG. 6  is a flowchart for illustrating a procedure of the system according to the present embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
         [0025]    The explanation will be given in the order shown below. 
         [0026]    1. Technological Basis 
         [0027]    2. Configuration Example of a Camera System According to the Present Embodiment 
         [0028]    3. Procedure of a System According to the Present Embodiment 
         [0029]    1. Technological Basis 
         [0030]      FIG. 1  is a block diagram for illustrating a camera control system in which a camera and a CCU are connected in a one-to-one basis so as to arrange or form a camera pair. This camera system is the one used in a studio of a TV station, or the like, in which a CHU  1200  and a CCU  1300  are connected via a camera cable  1100  on a one-to-one basis, and reference signals and video signals are transmitted. The camera system transmits/receives signals, such as video signals or return video signals, among a plurality of the CCU (Camera Control Unit)  1300  as a camera control apparatus, a plurality of the CHU (Camera Head Unit)  1200  connected to each of the CCU  1300  so as to arrange or form a plurality of camera pairs via the camera cable  1100 , and the CCU  1300 , and is configured from a video switcher  1400  for outputting video signals corresponding to the CHU  1200  and the CCU  1300  that have been selected, and a standard signal generator  1500  for outputting a standard signal that is a reference for establishing a video synchronization between each of the CHU  1200  and the CCU  1300 . 
         [0031]    The video switcher  1400  switches the video signals received from each of the CCU  1300  in accordance with selection to output. In order not to distort the video signals at a time of video switching, it is necessary that each of the video signals is synchronized, and that each of the CCU  1300  receives the video signals, which have been synchronized to the reference signal from the standard signal generator  1500 , from the CHU  1200 . The CCU  1300  transmits the reference signal from the standard signal generator  1500  to the CHU  1200 , while the CHU  1200  transmits the video signals synchronized to the reference signal to the CCU  1300 . 
         [0032]    However, although the video signals is synchronized to the reference signal, a timing error occurs in the actual video signals arrived at the video switcher  1400  due to a factor, such as a transmission delay of the camera cable connecting the CHU  1200  and the CCU  1300 , a delay in processing in the CCU  1300 , or the like. Therefore, in an input stage of the video switcher  1400 , a fine adjustment is to be performed for a transmitting timing of the video signals in the CHU  1200  so that the timing of each of the video signals from the each of the CCU  1300  can be matched. This assures an identity of input timings of the video signals transmitted from the CHU  1200 , in the video switcher  1400 . 
         [0033]    The adjustment of the transmitting timing can be performed by a phase regulation in a PLL (Phase Locked Loop) of the CHU  1200  (camera). Performing a delay adjustment by the PLL phase regulation on the side of the camera realizes an adjustment of the input timing of the video signal at low cost and at low power consumption without creating a buffer for the timing adjustment of video data or audio data. However, in this method, range allowed to be delayed from a standard signal form is limited to within one field of the video signal. When a delay adjustment on the side of the CCU  1300  is performed, or when a delay adjustment is performed over one field, a delay adjustment using the buffer for video data and audio data is necessary. 
         [0034]    As described above,  FIG. 1  shows a configuration in which the CHU  1200  and the CCU  1300  are connected via the camera cable on a one-to-one basis, and reference signals and video signals are transmitted. In this configuration, since the factors, such as a transmission delay of the camera cable, the delay in processing in the CCU  1300 , are resolved, it is necessary to perform the timing adjustment. On the other hand, as described before, there exists a method using the asynchronous transmission network for transmission between the CHU  1200  and the CCU  1300 . In the asynchronous transmission network, each of the CCU  1300  and the CHU  1200  transmits the reference signal or the video signal on the same transmission network. In this case, as described before, as the route path is not fixed and the route path varies in accordance with situation, an amount of the timing adjustment of the signals is not to be uniquely defined. Therefore, there is a difficulty in the timing adjustment of the video signals and the audio signals. In light of the foregoing, the present embodiment is aimed to adjust optimally a timing of signals in a camera system using an asynchronous transmission network. 
         [0035]    2. Configuration Example of a Camera System According to the Present Embodiment 
         [0036]      FIG. 2  is a schematic view for illustrating an example of a camera system using an asynchronous transmission network according to an embodiment. As  FIG. 2  shows, a camera system  100  is configured from a plurality of a CHU (a camera unit)  200 , a CCU (a camera control unit)  300 , a video switcher  400 , and a standard signal generator  500 . The camera and the CCU are connected via an asynchronous transmission network  600 . Note that the present embodiment exemplifies the Ethernet (a registered trademark) as the asynchronous transmission network  600 , however it is not limited to this example. 
         [0037]    When a video transmission is performed using the asynchronous transmission network, since a transmission path varies for each combination of each of the CHU  200  and the CCU  300 , the delay amount will varies. In this case, it is also possible to align arrival timing of video signals in each of the CCU  300  by adjusting timing, similar to the configuration in  FIG. 1  where the CHU  200  and the CCU  300  are connected in a one-to-one basis. However, a route path is not fixed on the asynchronous transmission network  600  and the route path may vary depending on the situation. 
         [0038]    Moreover, in perspective of increasing flexibility in the development of the camera system  100 , it is desired that switching an asynchronous transmission wire such as a LAN cable, or a device such as a switching hub, a router, or the like, for example, can be flexibly accepted. In this case, the individual adjusting timing as described in  FIG. 1  will be difficult to be dealt with. 
         [0039]    Further, by using the asynchronous transmission network  600 , when a failure occurs on the route path currently in use, there is an advantage in developing a redundant configuration against the failure on a transmission device by changing into a different route path. In such a case, it is also difficult to deal with the individual adjusting timing as explained in  FIG. 1 . 
         [0040]    Further, due to a bandwidth limitation of the asynchronous transmission network, it is assumed that transmission may be performed after a video compression (encoding) in the CHU  200 , and the compressed image is to be decompressed (decoding) in the CCU  300 . In this case, it is necessary to take into consideration a delay due to the encoding and decoding, after all, dealing with the individual adjusting timing is associated with difficulties. 
         [0041]    For the reasons described above, a timing adjustment system of the CHU-CCU which is capable of coping flexibly with configuration changes of the camera system  100  is desired in the CHU-CCU camera system which is configured on the asynchronous transmission network  600 . 
         [0042]      FIG. 3  is a schematic view for illustrating the system illustrated in  FIG. 2  in more detail.  FIG. 2  exemplifies the Ethernet (a registered trademark) as the asynchronous transmission network, however, it is not limited to the Ethernet (a registered trademark). The asynchronous transmission network  600  includes a plurality of a switching hub  610 . A plurality of the CHU  200  and a plurality of the CCU  300  are configured so as to correspond with each other on a one-to-one basis, by setting IP address appropriately, for example. Moreover, the reference signal from the standard signal generator  500  is to be transmitted from the CCU  300  to the CHU  200  using the method described in the Patent Literature 2 above or a method of the IEEE1588, or the like. This enables a measurement of the transmission the delay amount between the CHU  200  and the CCU  300 . 
         [0043]    The configuration shown in  FIG. 3  includes a CNU (camera command network unit)  700  in order to adjust a signal delay amount. The CNU  700  has a function for adjusting the signal delay amount. As described later, it is possible not to have the CNU  700 , but to set a certain CCU  300  as a master device so that the CCU  300  of the master device is to adjust the delay amount. 
         [0044]    In the system shown in  FIG. 3 , a structural element  800  which has functions of the CCU  300  and the CNU  700  can be configured by a central processing unit, such as a circuit (hardware) or a CPU, or the like, and a program (software) to function the central processing unit. In this case, the program may be stored in a recording medium, such as a memory included with a structural element such as the CCU  300  or the like, or a memory that is inserted externally, or the like. 
         [0045]      FIG. 4  and  FIG. 5  are schematic views for illustrating a configuration for adjusting the delay amount in detail. A configuration shown in  FIG. 4  corresponds to the configuration in  FIG. 3 , and separately mounts the CNU (camera command network unit)  700  for adjusting the delay amount. The delay amount between the corresponding CHU  200  and the CCU  300  is to be informed from the CCU  300  to CNU  700 . The CNU  700  arbitrates the delay amount to determine the optimal delay amount. The determined delay amount is to be informed through the CCU  300  to the CHU  200 , and the CHU  200  sets up with a video buffer accordingly in order to align timing of video signals reached at each of the CCU  300 . 
         [0046]    As a concrete method to determine the delay amount, there is a method for adjusting the video buffer so that, with respect to the pair of the CHU  200  and the CCU  300  whose delay is the largest, the delay amount of another pair of the CHU  200  and the CCU  300  to be the same. The concrete method to determine the delay amount will be explained in detail based on  FIG. 6  later. Note that the CNU  700  is used for the arbitration here, however, another structural element can be used as a device for arbitration in place of the CNU  700 . 
         [0047]      FIG. 5  shows a configuration in which any of the CCU  300  functions as a master device to arbitrate the delay amount without having the CNU  700 . As described above, a certain CCU  300  may be configured to perform function of arbitration without mounting newly an additional device for arbitration. 
         [0048]    3. Procedure of a System According to the Present Embodiment 
         [0049]      FIG. 6  is a flowchart for illustrating a procedure of the system according to the present embodiment. A flow of processing from activating the system power or resetting the system to determining the video buffer will be explained as below. Here, as shown in  FIG. 3  and  FIG. 4 , an explanation will be given on a case where the CNU  700  is set for arbitration. 
         [0050]    Firstly, in step S 10 , activation of the system or resetting the system is performed. When a change is made in the configuration of the asynchronous transmission network  600  (the number of the switching hub  610 , etc.), when a change is made in the number of CHU  200 , or the like, a calibration is performed for a whole system by a system reset. In the subsequent step S 12 , synchronization is established between each of the CHU  200  and the CCU  300 . In the subsequent step S 14 , delay time is measured for each of the pair of the corresponding CHU  200  and CCU  300 . Measuring the delay time can be performed along with establishing synchronization in step S 12 , using the method described in the Patent Literature 2 described above, the method of the IEEE1588, or the like. Specifically, the delay time is to be measured by comparing the timing of the video signal obtained in each of the CCU  300  and a reference pulse generated in the standard signal generator  500 . In the subsequent step S 16 , the CCU  300  notifies the CNU  700  of the delay time. In the subsequent step S 18 , a selection is made for the delay time of a one-pair of the CHU  200  and the CCU  300  whose delay time is the largest in the CNU  700 . 
         [0051]    In the subsequent step S 20 , a comparison is made between the selected delay time and a predetermined allowable time, and determination is made on whether the delay time is equal to or more than the allowable time. If the delay time is equal to or more than the allowable time, it proceeds to step S 22 , and a selection is made for the delay time of a one-pair of the CHU  200  and the CCU  300  whose delay time is the second largest in the CNU  700 . In the subsequent step S 24 , regarding a one-pair of the CHU  200  and the CCU  300  whose delay time exceeds the allowable time, the CCU  300  or the CHU  200  is to be notified that the delay time is more than the allowable time. The one-pair of the CHU  200  and the CCU  300  that has been notified of the notification above displays that it is operating asynchronously in the corresponding CCU  300 , the CHU  200  or the video switcher  400 , in order to notify the user of being operating asynchronously. If displaying in the CHU  200 , it can display within a finder that the CHU  200  includes, as well as on the outside surface of the CHU  200 . If displaying in the video switcher  400 , it can be displayed, corresponding to each of the CHU  200  close to a selection button of each of the CHU  200  that the video switcher  400  includes. This enables the user to recognize instantly whether a live video image that has been imaged in the selected CHU  200  is synchronizing. 
         [0052]    After the step S 24 , it returns to the step S 20 , and the same processing is to be performed for the one-pair of CHU  200  and the CCU  300  that has been selected in the step S 22 . A loop from the step S 24  to the step S 20  is repeated with respect to the one-pair of the CHU  200  and the CCU  300  selected in the step S 22  until the delay time becomes smaller than the allowable time. Therefore, when the delay time is larger than the allowable time regarding another one-pair of the CHU  200  and the CCU  300  which is selected subsequently, the fact that the delay time is larger than the allowable time will be displayed in either the CCU  300 , the CHU  200  or the video switcher  400 , which enables the user to recognize that the video image that has been imaged is asynchronous. 
         [0053]    Meanwhile, in step S 20 , if the delay time is less than the allowable time regarding the one-pair of the CHU  200  and the CCU  300  that is currently selected, it proceeds to step S 26 . In step S 26 , each of the CCU  300  is notified of the delay time of the one-pair of the CHU  200  and the CCU  300  that is currently selected. That is, all of the pairs of the CHU  200  and the CCU  300  whose delay time is smaller than the allowable time are to be notified of the delay time of one of the one-pair of the CHU  200  and the CCU  300  that is currently selected. Note that if the delay amount of all the pairs of the CHU  200  and the CCU  300  are smaller than an allowable delay amount, the delay time of the one-pair of the CHU  200  and the CCU  300  that is currently selected becomes the largest delay time, and the delay time of all other pairs is regarded to be the same with the largest delay time. In the subsequent step S 28 , in each of the CCU  300 , the amount of the video buffer corresponding to the notified delay time is to be calculated. Here, by calculating difference between the current delay time and the allowable delay time, the buffer amount for making the delay time to be the same with the allowable delay time will be calculated. 
         [0054]    In the subsequent step S 30 , each of the CCU  300  indicates the corresponding CHU  200  the calculated video buffer amount. This causes the CHU  200  to create a buffer in a memory for accumulating video signals therein based on the indicated video buffer amount, and to adjust timing of the signals. As shown in  FIG. 4 , in the CHU  200 , a buffer  204  is created in a memory for storing data of video signals obtained in an image pickup element  202 . This causes the CHU  200  to set up the buffer to start transmitting video images, therefore, it is possible to adjust timing of the video signals depending on the buffer amount. This causes the delay time to be set to be the same with respect to all of pairs of the CHU  200  and the CCU  300  whose delay time are smaller than the allowable time. Accordingly, since the delay amount of each of the video image are the same when the video images of each of the CHU  200  are switched in the video switcher  400 , it is possible to surely avoid distortion of the video signals. 
         [0055]    Further, the adjusting timing of signals can be performed not only by creating a buffer, but also by the PLL phase regulation in the CHU  200 . In this case, it is possible to make the delay time of signals to be the same with the allowable delay time by adjusting the timing in which the image pickup element  202  clicks a shutter. Further, it is also possible to adjust the timing of signals by creating a buffer in the CCU  300 . 
         [0056]    By performing processing described above, it is possible to synchronize the signals transmitted from each of the CCU  300  to the video switcher  400 . Then, after the step S 30 , processing will be end (END). Note that pairs of the CHU  200  and the CCU  300  whose the delay time is equal to or more than the allowable time are asynchronous, however, since being asynchronous has been displayed, the user can deal with the video image after recognizing that it is asynchronous. 
         [0057]    Note that in the explanations described above, a video buffer that adjusts the delay amount is created in the CHU  200 , however, the video buffer can be created in the CCU  300 . Also, when the adjusting delay is performed in the CHU  200 , the delay amount can be configured not by the buffer, but by the PLL phase regulation. Further, the adjusting delay can be realized using both crating a buffer and the PLL phase regulation. 
         [0058]    As described above, according to the present embodiment, it is possible to surely synchronize signals from each of the CHU  200  in a system which can make the transmission path simpler, reduce the cost, and develop a complex camera system with few wiring, by using the asynchronous transmission network. Therefore, it is possible to surely avoid distortion of video signals or audio signals when the video images that have been imaged in the each of the CHU  200  are switched. Further, using the asynchronous transmission network makes the flexibility in changing a camera network increased, and adapting a bus wiring makes the flexibility in wiring increased which leads to increase the flexibility in switching cameras and CCU. Further, by changing a destination address (IP address), it is possible to easily switch a camera (CHU  200 ) and the CCU  300 . 
         [0059]    A preferred embodiment of the present invention has been explained in detail above with reference to the attached drawings, the present invention is not limited to this example. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.