Camera system

Abstract

To stably and appropriately perform monitoring by considering a situation of all of a plurality of cameras to be used.SOLUTION: A communication situation recognition part transmits a ping command to a radio terminal side and receives a response signal to the ping command as a response time confirmation operation (S11). It compares the recognized response time TR with a threshold T1 (S13), and transmits such a control signal to lower a frame rate of this camera toward to the camera side when the TR is equal to or more than the T1 (S21). In this manner, a camera control part performs adjustment so as to lower the frame rate of the connected camera. In the operation, the frame rate is set low (a data amount is small) because a reception situation from the radio terminal is not satisfactory when the response time TR is long. In the operation, the threshold T1 to be used to control the operation is set according to priority of the radio terminal.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a camera system that acquires images from a plurality of cameras. [Background technology]

[0002] For example, in a surveillance camera system, multiple cameras are used simultaneously to ensure reliable surveillance, and the field of view of each camera is set to be different so that there are no blind spots around the subject being monitored. Images from these multiple cameras are sent simultaneously to a server (camera server). A user (supervisor) can view the images from each camera on a monitor via this server.

[0003] In order to improve the quality of the video obtained by each camera, it is preferable that the image quality is high (high spatial resolution) and the frame rate of the video is high (high temporal resolution). However, when the quality of the video of each camera is improved in this way, the data amount of the video signal transmitted from each camera in the above configuration becomes large, and when the server simultaneously obtains video signals from multiple cameras, the total data amount transmitted on the line connecting the server and each camera becomes large, and the bandwidth used on the network line used becomes tight, and the server side may not be able to receive the video signal, or this may result in problems such as a limit on the number of cameras used.

[0004] For this reason, for example, Patent Document 1 describes a camera system in which the frame rate of each camera is set low so that the amount of data is small enough to prevent the above-mentioned problems, and the frame rate of a specific camera is increased as necessary. In this technology, a server obtains video signals from all cameras with low frame rates, and the server determines on the server side whether or not there is an event to be monitored in the video from each camera (for example, whether or not there is a person in the video). In this case, the server controls the camera so as to increase the frame rate of the camera determined to have such an event. As a result, the amount of data transmitted from this camera increases only when an event is recognized and it is recognized that detailed monitoring is particularly necessary, and problems such as congestion of the used bandwidth are less likely to occur. In other words, monitoring using multiple cameras can be performed stably and appropriately. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-133561 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] In the above camera system, the frame rate and other settings of one camera are changed based only on the video situation in that camera (whether or not an event occurs), without taking into consideration the situations of the other cameras, and the situations of the other cameras are not changed.

[0007] As described above, in order to perform monitoring properly, for example, it is preferable that the frame rate of each camera is high, but in the above camera system, for example, the frame rate of all cameras is set low even though there is sufficient bandwidth available, or the frame rate of one camera is set high, causing the bandwidth to become congested and sufficient monitoring capability to be unavailable. In recent years, local 5G networks are sometimes used for communication between each camera and the server, and in this case, such problems have become prominent, especially when a large number of cameras are used.

[0008] In other words, in the conventional technology, the overall situation of the multiple cameras used is not taken into consideration, and therefore sufficient surveillance capabilities may not be obtained. For this reason, a camera system that can perform stable and appropriate surveillance by taking into consideration the overall situation of the multiple cameras used is desired.

[0009] The present invention has been made in view of the above circumstances, and has an object to solve the above problems. [Means for solving the problem]

[0010] The present invention is a camera system comprising a plurality of cameras, a wireless terminal provided for each of the plurality of cameras and transmitting a video signal based on images obtained from the cameras, and a base station receiving the video signals from each of the cameras, wherein a priority is set for each of the plurality of wireless terminals, and a camera control server is provided which recognizes a reception condition parameter representing the reception condition of the base station from each of the wireless terminals, and controls each of the cameras based on the magnitude relationship between a threshold determined according to the priority and the reception condition parameter to reduce the resolution of the image to reduce the data amount of the video signal when the reception conditions are not good, and to improve the resolution of the image to increase the data amount of the video signal when the reception conditions are good. The camera may be provided with a video analysis unit that uses image analysis techniques to recognize the presence or absence of a specific event in the video obtained from each of the cameras, and the camera control server may re-set the priority of each of the cameras so as to increase the priority of the camera from which the video in which the event was recognized was obtained. The resolution may be controlled by controlling a frame rate of the video. Effect of the Invention

[0011] According to the present invention, surveillance can be performed stably and appropriately by taking into consideration the overall conditions of the multiple cameras being used. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a configuration of a camera system according to an embodiment. [Diagram 2] 2 is a diagram showing a configuration of a camera control server in the camera system according to the embodiment. FIG. [Diagram 3] 5 is a flowchart showing a first example of the operation of the camera system according to the embodiment. [Figure 4] 4 is a diagram showing an example of priorities and thresholds set in a camera (wireless terminal) in the camera system according to the embodiment. [Diagram 5] 10 is a flowchart showing a second example of the operation of the camera system according to the embodiment. [Figure 6] 13 is an example of resetting priorities and thresholds by a second operation in the camera system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, a camera system according to an embodiment of the present invention will be described in detail. In this camera system 1, multiple wireless terminals 10 are used, and each wireless terminal 10 is connected to a base station 20 installed at one point on the ground by wireless communication via a 5G (fifth generation mobile communication system) network. A network core device 30 is connected to the base station 20 for exchanging data with each wireless terminal 10.

[0014] A camera 40 is connected to each wireless terminal 10 in one-to-one correspondence, and the wireless terminal 10 transmits a video signal obtained from the connected camera 40 to the base station 20, and the network core device 30 can obtain this video signal from all the wireless terminals 10 (cameras 40). A video monitoring server 50 is connected to the network core device 30, and the administrator of this camera system 1 can view the video obtained from each camera 40 on a monitor (display) in the video monitoring server 50. Alternatively, the video can be viewed after various processing is performed on the video, or a specific object (e.g., a person) in the video can be recognized by a well-known image recognition method. In this case, by properly securing the field of view of each camera 40, blind spots in the object monitored by this camera system 1 can be eliminated, and proper monitoring can be performed.

[0015] A camera control server 60 that controls the state of the video signal output from each camera 40 based on information obtained from all the cameras 40 is also connected to the network core device 30. Correspondingly, each camera 40 (wireless terminal 10) is provided with a camera control unit 70 that controls the connected camera 40 according to instructions from the camera control server 60. A sensor 80 that recognizes various conditions (e.g., illuminance) when the camera 40 captures an image is also provided for each camera 40, and the wireless terminal 10 transmits the detection result of the sensor 80 together with the video signal to the base station 20 (network core device 30). In addition to the camera control server 60, a management server 90 that manages the entire camera system 1 is also connected to the network core device 30. Note that the base station 20 may use a single server that integrates the functions of the video monitoring server 50, the camera control server 60, and the management server 90. Note that the wireless terminal 10 may use a single device that integrates the functions of the camera 40 and the camera control unit 70.

[0016] The camera control server 60 recognizes the state of communication with each camera 40, and adjusts the resolution of the video signal of each camera 40 accordingly. At this time, a priority is set for each camera 40, and this control is performed using a threshold value set according to this priority. Furthermore, this priority is changed to a higher priority when a particular event that should be noted is recognized in the video obtained from each camera 40 (for example, when a person is recognized in the video).

[0017] 2 is a diagram showing the configuration of the camera control server 60. In reality, the camera control server 60 is configured from an ordinary computer, and therefore also uses an operation unit such as a keyboard and a touch panel display, a display (display unit), and the like that an ordinary computer is equipped with, but only the components directly related to the present invention are described here.

[0018] In this embodiment, a video signal input unit 61 is provided which receives video signals from all connected cameras 40 via the network core device 30. A video analysis unit 62 determines the presence or absence of a particularly noteworthy event in the video from each received video signal (for example, whether or not a person is present in the video) by using a well-known image analysis method.

[0019] The communication status recognition unit 63 recognizes the communication status between the base station 20 and each wireless terminal 10 by converting it into a numerical value as a reception status parameter. Here, as such a reception status parameter, for example, a response time to a control signal (for example, a ping command) issued by itself is used. This operation will be described later.

[0020] The camera control instruction unit 64 outputs a control signal for controlling each camera 40 according to the results recognized by the communication situation recognition unit 63 and the video analysis unit 62. The control performed here is, for example, control of the frame rate (time resolution) of the video captured by each camera 40, thereby controlling the data amount of the video signal output from each camera 40. Such control of the data amount is performed to stabilize the communication in this camera system 1, particularly between the wireless terminal 10 and the base station 20, thereby stabilizing monitoring, and particularly enhancing the monitoring capability of the camera 40 (wireless terminal 10) in which the event has been recognized.

[0021] This operation is mainly a combination of two operations. The first operation is an operation for comparing the reception condition parameter (response time) for a certain wireless terminal 10 with a certain threshold, and adjusting the amount of data of the video signal obtained from this camera 40 by lowering (reducing) the frame rate of the corresponding camera 40 when the response time is long (short). Here, an initial value of the priority is set according to the camera 40, and this threshold is set according to the priority. If the number of cameras 40 is N (4 in FIG. 1), the priority is set to a different value from 1 to N for each camera 40, with "1" being the highest priority and "N" being the lowest priority.

[0022] When the priority is high, the threshold is set to make it easier to increase the frame rate, and when the priority is low, the threshold is set to make it easier to decrease the frame rate. By mixing video signals with higher frame rates (larger data amounts) and video signals with lower frame rates (smaller data amounts) in this way, the total amount of data transmitted by wireless communication of base station 20 can be kept within a certain range, enabling stable wireless communication.

[0023] The second operation is an operation in which, when a specific event is recognized by the video analysis unit 62 in the video from a certain camera 40, the priority, which was the initial value, is changed so that the priority of this camera 40 becomes the highest. In this case, the frame rate of this camera 40 is set to a threshold value that is likely to increase (the amount of data is likely to increase), and the priority of the other cameras 40 is accordingly lowered and set to a threshold value that is likely to decrease the frame rate (the amount of data is likely to decrease). This makes it easier to increase the frame rate of the camera 40 in which an event has been recognized, making it easier to increase the time resolution, thereby improving the monitoring ability of this camera 40, and by reducing the amount of data of the video signal emitted by the other cameras 40, stable wireless communication can be performed even in this case.

[0024] In this case, since only the threshold value used for controlling the frame rate is set according to the priority, for example, even for a camera 40 with a low priority, the frame rate is controlled to be low only when the response time is longer than the threshold value, that is, when the communication conditions are poor. Therefore, when the communication conditions are favorable, the frame rate of the camera 40 is not controlled to be low unnecessarily. Furthermore, even for a camera 40 in which an event is recognized in the video and the priority is set to be the highest, the frame rate is not increased when the communication conditions are poor. Such an operation is realized by changing the threshold value according to the priority, rather than directly controlling the frame rate according to the communication conditions.

[0025] 2, a storage unit 65 including a hard disk and non-volatile memory is provided, and stores such an initial priority value for each camera 40 and the relationship between the priority and the threshold value. Various data used in the image analysis in the video analysis unit 62 is also stored in the storage unit 65.

[0026] 3 is a flow chart showing the operation of the camera control server 60 during the first operation. This operation is repeated for each camera 40 (wireless terminal 10) at regular time intervals. Here, the communication status recognition unit 63 recognizes the current reception status from each camera 40, and the camera control instruction unit 64 controls the frame rate of each camera 40 based on the result. The reception status monitored here is evaluated as the response time from each wireless terminal 10 to a control signal from the camera control server 60 to the wireless terminal 10 on the camera 40 side. Here, as described above, the initial priority value of each camera 40 (wireless terminal 10) is stored in advance in the storage unit 65.

[0027] In addition, as described below, this operation uses thresholds T1, T2 (T1>T2) for response time and thresholds DT1, DT2 (DT1>DT2) for response time deviation, which are set according to priority and stored in storage unit 65. Fig. 4 shows an example of such a relationship between priority and thresholds T1, DT1. Here, only T1 and DT1 are shown, but T2 and DT2 are set similarly within the above-mentioned range. The threshold T1 for response time and the threshold DT1 for response time deviation are set larger as the priority becomes higher (the priority value becomes smaller).

[0028] In FIG. 3, first, the communication status recognition unit 63 transmits a ping command to the wireless terminal 10 as a response time confirmation operation, and receives a response signal in response to the ping command (S11). Here, the time difference between the transmission of the ping command and the reception of the response signal is recognized as the response time TR (S12). At this time, since this operation is repeated as described above, TR0, which is the average value of two or more response times including the response time TR obtained here and the response time TR obtained in one or more operations prior to this point, is also calculated at the same time. As a result, the difference (response time deviation ΔTR) between the response time TR obtained at this point and TR0 is also recognized (S12). As a result, the TR and ΔTR at this point in all the cameras 40 (wireless terminals 10) are recognized.

[0029] The camera control instruction unit 64 compares the recognized response time TR with a threshold value T1 (S13), and if TR is equal to or greater than T1 (if the response time is long due to poor reception conditions, S13: Yes), it transmits a control signal to the camera control unit 70 on the camera 40 side to lower the frame rate of the camera 40 (S21). This causes the camera control unit 70 to adjust the frame rate of the connected camera 40 to be lowered. The amount of reduction in this case is set appropriately, for example, to about 1 FPS. This completes the frame rate adjustment operation.

[0030] Furthermore, if the response time TR is less than T2 (if the reception conditions are good and the response time is short, S14: Yes), a control signal to increase the frame rate of this camera 40 is transmitted to the camera control unit 70 on the camera 40 side (S22). This causes the camera control unit 70 to adjust the frame rate of the connected camera 40 to be increased. The amount of increase at this time is set equal to the increase amount (S21) described above. This ends the frame rate adjustment operation.

[0031] On the other hand, when the response time TR is less than T1 (S13: No) and not less than T2 (S14: No), adjustment according to the magnitude relationship between the response time deviation ΔTR and the threshold values DT1 and DT2 is similarly performed. First, the camera control instruction unit 64 compares the recognized response time deviation ΔTR with the threshold value DT1 (S15). When ΔTR is not less than DT1 (when the response time deviation is large because the reception status is not good, S15: Yes), a control signal for reducing the frame rate of this camera 40 is transmitted toward the camera control unit 70 on the camera 40 side (S21). As a result, the camera control unit 70 adjusts to reduce the frame rate of the connected camera 40. The reduction width at this time is the same as described above. Thereby, the adjustment operation of the frame rate ends.

[0032] Also, when the response time deviation ΔTR is less than DT2 (when the reception status is good and the response time deviation is small, S16: Yes), a control signal for increasing the frame rate of this camera 40 is transmitted toward the camera control unit 70 on the camera 40 side (S22). As a result, the camera control unit 70 adjusts to increase the frame rate of the connected camera 40. The increase width at this time is the same as described above. Thereby, the adjustment operation of the frame rate ends.

[0033] When T2 < TR < T1 (S13: No, S14: No) and DT2 < ΔTR < DT1 (S15: No, S16: No), the frame rate is not changed (S17), and the adjustment operation ends.

[0034] In the above operation, when the response time TR is long, the reception status from the wireless terminal 10 is not good, so the frame rate is set low (the data volume is small). When the response time TR is short, the reception status from the wireless terminal 10 is good, so the frame rate is set high (the data volume is large). However, in this operation, the frame rate is adjusted according to the magnitude relationship between the response time TR and the threshold value. The threshold values T1 and T2 used for this purpose are set according to the priority of the wireless terminal 10. Since the priority varies for each wireless terminal, if the priority (threshold value) is set appropriately, it is possible to prevent the frame rate of a certain camera 40 (wireless terminal 10) from being unnecessarily lowered. Also, until the used bandwidth of the network line becomes tight, it is possible to prevent the frame rate of a certain camera 40 (wireless terminal 10) from being increased. As a result, the base station 20 (network core device 30, video monitoring server 50, etc.) can stably and efficiently obtain the video signals from each camera 40 (wireless terminal 10).

[0035] Also, even if the response time TR at the measurement time is within T2 ≦ TR < T1, when the response time deviation ΔTR, which is the deviation from the average value of the response time TR within a certain period, is large, the reception status is recognized as unstable, so the frame rate is set low (the data volume is small). When the response time deviation ΔTR is small, the reception status is stable, so the frame rate is set high (the data volume is large). Also by this operation, the base station 20 (network core device 30, video monitoring server 50, etc.) can efficiently obtain the video signals from each camera 40 (wireless terminal 10) without waste.

[0036] In the operation of FIG. 3, the priority of each camera 40 (wireless terminal 10) and the above-mentioned threshold values associated therewith were set in advance. On the other hand, in the second operation, the priority (threshold value) of each camera 40 (wireless terminal 10) is changed according to the content of the video obtained from the camera 40, and then the operation of FIG. 3 is performed in the same manner. FIG. 5 is a flowchart showing the operation of the camera control server 60 in such a second operation.

[0037] Here, the camera control instruction unit 64 reads out the priority (initial value) of each camera 40 (wireless terminal 10) stored in the storage unit 65 and each threshold value for each priority (S31). After that, the video analysis unit 62 analyzes the video (still image) obtained from each camera 40 by a known image analysis method (S32) and determines whether or not there is a specific event that should be noted in this video (S33). When there is such an event, it is, for example, when a monitored object such as a person or a car is recognized in the video, and can be set appropriately according to the purpose of monitoring.

[0038] If there is a camera 40 for which an event has been recognized in this way (S33: Yes), the camera control instruction section 64 resets the priority so that the priority of this camera 40 becomes the highest (S34).

[0039] FIG. 6 is a diagram showing an example of transition of the priority and threshold (T1, DT1) in a case where there are four cameras 40, #1 to #4. Here, FIG. 6(a) shows an initial state (S31), and here, the priorities of #1 to #4, which correspond to the cameras 40, are set to 1 to 4. FIG. 6(b) and (c) show the priority and threshold (S34) after resetting when the event is recognized in #3 and #4, respectively. In FIG. 6(b), the priority of #3 is changed to 1, and the priorities of #1, #2, and #4 are changed to 2, 3, and 4, respectively. In FIG. 6(c), the priority of #4 is changed to 1, and the priorities of #1, #2, and #3 are changed to 2, 3, and 4, respectively. That is, in this case, as the priority (threshold) of the camera 40 in which the event is recognized is changed, the priorities (threshold) of the other cameras 40 are also changed.

[0040] Thereafter, the camera control instruction unit 64 recognizes each threshold based on the reset priority (S35), and adjusts the frame rate of each camera 40 using this threshold (S36). These operations are similar to those shown in Fig. 3. As described above, the operations in Fig. 3 can be performed at regular time intervals, but the operations in Fig. 5 can be similarly performed at time intervals longer than the operation intervals in Fig. 3.

[0041] In the step of resetting the priority (S34), if there are multiple cameras 40 that have recognized an event, the priority order among the multiple cameras 40 can be determined according to an appropriately determined rule. For example, the priority order of the camera 40 with a high initial priority value can be set high even in this case. Alternatively, if multiple types of events are set by the video analysis unit 62 as the events set as described above, the priority order can be determined according to the type of event.

[0042] In such a second operation, the frame rate is controlled to be higher by increasing the priority of the camera 40 in which an event is recognized, and the monitoring capability of this camera 40 can be improved. On the other hand, the frame rate is controlled to be lower by decreasing the priority of the other cameras 40, so that the amount of data received by the base station 20 can be kept within a certain range, and stable communication can be performed. At this time, the frame rate of each camera 40 is not controlled to be unnecessarily low (small amount of data). Furthermore, the frame rate of each camera 40 is not controlled to be high (large amount of data) until the bandwidth used on the network line becomes tight.

[0043] In the above operation, the response time to the ping signal is used as the reception condition parameter used to evaluate the reception condition from each wireless terminal 10. However, other methods can be used as long as they can properly evaluate the reception condition. For example, the band used in the communication between the base station 20 and each wireless terminal 10, the electric field strength at the time of reception, etc. may be used. The threshold value is appropriately set accordingly.

[0044] In the example of Fig. 3, two types of thresholds are used for both TR and ΔTR: a threshold (T1, DT1) used to determine whether to lower the frame rate, and a threshold (T2, DT2) used to determine whether to increase the frame rate. However, it is also possible to simply use only one type of threshold and control the frame rate to lower or increase based on the magnitude relationship with this threshold, or conversely, control using more thresholds. In this case, for example, it is also possible to further set a threshold Tx larger than the threshold T1, and when TR becomes equal to or larger than Tx, adjust the frame rate to be lowered (S21) by a larger amount than when TR is equal to or larger than T1 (S13: Yes).

[0045] In the above example, the frame rate is adjusted based on the magnitude relationship between each of TR and ΔTR and the threshold value set for each of them, as shown in Fig. 3. However, this adjustment may be performed using only one of TR and ΔTR.

[0046] In the above example, the frame rate reduction range (S21) and increase range (S22) are set in advance, but the reduction range and increase range can be adjusted as appropriate according to the average reception conditions of the base station 20 and the amount of data received, etc. This enables more efficient transmission of video signals.

[0047] In the above example, the frame rate of each camera 40 is controlled to adjust the amount of data. However, parameters related to the image that affect the amount of data to be transmitted other than the frame rate can be changed as appropriate. For example, instead of changing the frame rate (time resolution), the number of pixels of the image (spatial resolution) may be changed. Alternatively, both may be changed.

[0048] In the second operation (FIG. 5), the video analysis unit 62 on the camera control server 60 side is used to determine whether an event has occurred. However, for example, the presence or absence of an event can be determined on the side of each camera 40 or the video surveillance server 50, and the camera control server can recognize only the result and make similar adjustments on the camera control server side. In other words, the video analysis unit does not need to be on the camera control server side.

[0049] The present invention has been described above based on the embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0050] 1 Camera System 10 Wireless terminals 20 base station 30 Network Core Equipment 40 Camera 50 Video Surveillance Server 60 Camera Control Server 61 Video signal input section 62 Video Analysis Section 63 Communication Status Awareness Unit 64 Camera control instruction unit 65 Storage section 70 Camera control unit 80 Sensors

Claims

1. A camera system comprising: a plurality of cameras; a wireless terminal provided for each of the plurality of cameras, the wireless terminal transmitting a video signal based on an image obtained from the camera; and a base station receiving the video signal from each of the cameras, A camera system characterized in that it comprises a camera control server which sets a priority for each of a plurality of the wireless terminals, recognizes a reception condition parameter representing the reception condition of the base station from each of the wireless terminals, and controls each of the cameras so as to reduce the resolution of the image to reduce the data amount of the video signal when the reception conditions are poor, and to improve the resolution of the image to increase the data amount of the video signal when the reception conditions are good, based on the magnitude relationship between a threshold determined according to the priority and the reception condition parameter.

2. A video analysis unit that recognizes the presence or absence of a specific event in the video obtained from each of the cameras by an image analysis method, The camera control server includes:

2. The camera system according to claim 1, further comprising: resetting the priority of each of the cameras so as to increase the priority of the camera from which the image in which the event was recognized was obtained.

3. 3. The camera system according to claim 1, wherein the resolution is controlled by controlling a frame rate of the video.

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