JP2023141291A - Camera system, and control method camera system - Google Patents

Abstract

The present invention provides a technique for preventing data loss and problems such as video stopping on a monitor due to data loss. A camera system including a plurality of cameras, the plurality of cameras outputting video data in a GOP format, and the plurality of cameras outputting video data whose I frame generation timings do not overlap with each other. [Selection diagram] Figure 1

Description

The present invention relates to a camera system and a method of controlling the camera system.

Ensuring the safety of passengers when getting on and off trains is an important issue for train operation. As part of such safety measures, a train monitoring system has been developed that uses a camera attached to the side of the vehicle to photograph the area around the door and displays the camera image on the driver's cab monitor (for example, see Patent Document 1). ).

By using such a system, the train driver will be able to operate the train by checking the boarding and alighting of passengers on the monitor in the driver's cab when the train stops at a station. In the past, analog systems with no delays were used preferentially because real-time performance was required for passenger safety monitoring, but in recent years, advances in IP technology have made low-latency transmission possible. , all devices are now connected to the IP network.

Japanese Patent Application Publication No. 2018-113602

However, since the communication band of the in-vehicle network is limited, if you try to display video data from multiple cameras at the same time on a monitor device, the communication band will be exceeded in the middle of the communication route, resulting in data loss. Something happened.

An object of the present invention is to provide a technique for preventing data loss and problems such as video stopping on a monitor due to data loss.

In order to solve the above problems, one of the typical camera systems of the present invention is a camera system including a plurality of cameras, the plurality of cameras outputting video data in the GOP format, and the plurality of cameras outputting video data in the GOP format. outputs video data whose I frame generation timings do not overlap with each other.

According to the present invention, it is possible to prevent data loss and problems such as video stopping on a monitor due to data loss.

Problems, configurations, and effects other than those described above will be made clear by the description in the following detailed description.

1 is a diagram illustrating a configuration example of a camera system according to an embodiment. FIG. 3 is a diagram showing functional blocks of a network camera according to an embodiment. FIG. 6 is a diagram showing the operation of the network camera according to the embodiment when the I frame generation timing is set by the system control device. It is a diagram showing functional blocks of a system control device according to an embodiment. FIG. 3 is a diagram illustrating an operation when the system control device according to the embodiment sets I frame generation timing for each network camera. FIG. 7 is a diagram showing an operation when a system control device according to a modified example sets I frame generation timing for each network camera.

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are denoted by the same reference numerals.

A system to which the video data traffic smoothing technology of this embodiment is applied is connected to a network camera equipped with a network interface such as a LAN, a network switch, a monitor device that decodes video data and displays video, and a system. It consists of a system control device that controls each device, and a network cable that connects them. In a system configured with these devices, the system control device can individually set the I-frame generation timing for each network camera based on the time managed by the system, thereby improving the communication of video data flowing over the network. Control is performed so that the amount is smoothed.

As a network camera, for example, H. 264 and H. There is a network camera that outputs video data in a compressed encoded stream in a GOP (Group of Picture) format, such as H.265. Video data in the GOP format is composed of consecutive multiple frame images in the format of I frame (Intra-coded Frame), P frame (Predicted Frame), or B frame (Bi-directional predicted Frame). . An I frame is an image that is encoded independently without using prediction in the temporal direction, a P frame is an image that is encoded using forward prediction, and a B frame is an image that is encoded forward, backward, or bidirectionally. This is an image.

As mentioned above, I-frames are images that are encoded independently without using prediction in the temporal direction, so it is generally known that the amount of data is much larger than that of P-frames and B-frames. . Therefore, if there are multiple network cameras on the system and the video data output from those cameras passes through the same route, if the timing of the I-frame video data overlaps, it is possible that the bandwidth of the communication route will be momentarily exceeded. There is sex.

In this embodiment, in order to intentionally shift the generation timing of the I-frame, the network camera under control has a function of generating I-frames according to the set timing, and the system control device that performs the control has a function to generate I-frames according to the set timing. There is a function to automatically set individual I frame generation timing for each camera according to the route band and the number of network cameras.

Furthermore, a GPS signal may be used as a reference for the time managed by the system. In this case, after the system control device synchronizes with GPS, each network camera may perform subordinate synchronization using NTP or the like, or each device may independently synchronize with GPS.

In this embodiment, a case will be described in which the present invention is used for train door monitoring. FIG. 1 shows an example of the configuration of a camera system according to this embodiment.

The camera system 100 shown in FIG. 1 is mounted on a train consisting of six cars 111 to 116. When a train moves toward the left in the drawing, the first car 111 shown at the left end is the first car, and the sixth car 116 shown at the right end is the last car. Conversely, when the train moves toward the right in the drawing, the sixth car 116 shown at the right end is at the front, and the first car 111 at the left end is at the rear. In the following, we will use an example where the driver is on board the first vehicle in the direction of train movement (for example, the first vehicle 111) and is responsible for operating the train (driving, opening/closing doors, etc.) by himself. explain.

The camera system 100 includes a network camera 121, a monitor device 122, a recording device 123, a system control device 124, a host system 125, and a network switch 126, but may include elements other than these. These devices are connected using network cables. Further, a power supply cable is connected to these devices, and power is supplied from a power supply section (not shown) of each vehicle.

Four network cameras 121-1 to 121-4 and a network switch 126 are installed in each of the vehicles 111 to 116. Further, the first vehicle 111 and the sixth vehicle 116 have a driver's cab, and two monitor devices 122-1 to 122-2 are installed in the driver's cab. The network camera 121 and monitor device 122 of each vehicle are connected to the network switch 126 of that vehicle via a network cable. Furthermore, a recording device 123, a system control device 124, and a host system 125 are also installed in the first vehicle 111. The recording device 123 and the system control device 124 are connected to a network switch 126 via a network cable, and the host system 125 is connected to the system control device 124 via a network cable. Note that the sixth vehicle 116 may also be provided with a system control device 124 and a host system 125, similar to the first vehicle 111, and these devices may be multiplexed.

Further, the network switch 126 of each vehicle is connected to the network switch 126 of an adjacent vehicle by a network cable. In this way, by connecting the network switches 126 mounted on adjacent cars, one network is constructed within the train. Note that these network cables are connected, for example, to a coverall box (not shown) via the underfloor of the vehicle, and jumper wires are used to connect the coverall boxes of adjacent vehicles between vehicles.

The host system 125 is, for example, a device that manages train operation. As the host system 125, a TMS (Train Management System) is used, for example. The host system 125 can output train operation information to the system control device 124 at predetermined intervals while the train is in operation. Train operation information includes train speed information, door opening/closing information (for example, information indicating the open/closed status of the door), boarding/exit information at the platform of the next station or the station where the train is currently stopping (for example, information indicating when the door should be opened). This includes information such as whether the door is on the right or left side of the train), the number of cars, and the train's direction of travel.

The network camera 121 of each vehicle can take images within a predetermined field of view (angle of view) at a predetermined frame rate (for example, 30 fps). Further, the network camera 121 of each vehicle encodes the captured video and transmits the obtained GOP format video data to the monitor device 122 and the recording device 123 via the network switch 126 and the network cable.

The recording device 123 can constantly record the video data received from the network camera 121 of each vehicle in association with camera identification information that identifies the source of the video data and the imaging time. The video data recorded in the recording device 123 is mainly used as analysis materials or video evidence in the event of an accident or crime.

The monitor device 122 in the driver's cab can display live video data transmitted from the network camera 121 of each vehicle. Further, the monitor device 122 in the driver's cab can also display past video data recorded in the recording device 123. The driver can use the monitor device 122 to check camera images taken by the network camera 121 of each vehicle.

The two monitor devices 122-1 to 122-2 are preferably arranged vertically or horizontally so that the driver can view these displays at the same time. Furthermore, in the present embodiment, the display area of the monitor device 122-1 is divided into 12 areas, ie, two vertically divided areas and six horizontally divided areas, and the same applies to the monitor device 122-2. Therefore, the camera images of a 6-car train (total of 12 camera images on one side of the train) can be displayed simultaneously using only the monitor device 122-1. Furthermore, by using the monitor device 122-2, camera images of trains with up to 12 cars can be displayed simultaneously. It is also possible to use each monitor device for other purposes, such as enlarging and displaying an image selected by the driver from among multiple camera images displayed on the monitor device 122-1 on the monitor device 122-2. It is.

The system control device 124 can control the display on the monitor device 122 according to instructions received from the driver or according to the operating status of the train. For example, the system control device 124 controls the display of the monitor device 122 to be on when the train is stopping at a station, and to turn off the display of the monitor device 122 when the train is running. Such display control can be performed, for example, based on train speed information that can be obtained from the host system 125. Note that the display may be turned on/off depending on whether the train speed is zero or not, or the display may be turned on/off depending on whether the train speed is below a predetermined threshold. It's okay.

The system control device 124 also performs control to switch the network camera 121 to be displayed by the monitor device 122. For example, if the right side door of the train opens at a station, the network cameras 121-1 and 121-2 installed on the right side of the train will be displayed, and if the left side door of the train opens, , network cameras 121-3 and 121-4 installed on the left side of the train are displayed. The network camera 121 to be displayed can be specified based on, for example, boarding gate information or train traveling direction information.

Here, the system control device 124 of this embodiment is configured to transmit I frame generation timing to each network camera 121. As a result, the monitor device 122 can receive video data from each network camera 121 so that the I frame generation timings do not overlap with each other, so that the camera video can be displayed without problems such as video stopping.

FIG. 2 shows functional blocks of the network camera 121 of this embodiment. In the network camera 121 of this embodiment, an imaging unit 1211, an encoding unit 1212, a main storage unit 1213, a control unit 1214, and a network interface (I/F) 1215 are connected to each other via a bus 1216. ing.

The imaging unit 1211 can convert an optical signal imaged onto an imaging surface through an optical system such as a lens into an electrical signal and output it as digital data (RAW data). The encoding unit 1212 can compress and encode the digital data output from the imaging unit using a predetermined method to generate GOP format video data including I frames, P frames, and B frames. The main storage unit 1213 can store digital data captured by the imaging unit 1211, video data encoded by the encoding unit 1212, and the like. The control unit 1214 can control the operation of the encoding unit 1212, as described later. The network I/F 1215 is an interface for transmitting video data on the main storage unit 1213 to an external device through the network, and for receiving various control signals transmitted from the external device.

FIG. 3 shows the operation of the network camera 121 of this embodiment when the I frame generation timing is set by the system control device 124. The network camera 121 generates a new I frame at the time of the I frame generation timing received from the system control device 124, and thereafter continues the GOP structure based on that timing. This operation causes the I frame generation timing to move on the time axis from t2, t3, and t4 to t2', t3', and t4' before and after receiving control from the system control device 124.

FIG. 4 shows functional blocks of the system control device 124 of this embodiment. In the system control device 124 of this embodiment, a GPS antenna 1241 and a GPS receiver 1242 are connected by a high frequency coaxial cable 1243, and the GPS receiver 1242, a main storage section 1244, a control section 1245, and a network interface ( I/F) 1246 are connected to each other via a bus 1247.

GPS antenna 1241 can receive GPS signals from GPS satellites and send them to GPS receiver 1242. The GPS receiver 1242 can synchronize with the received GPS signal and send time information to the main storage unit 1244. The main storage unit 1244 can store time information synchronized with GPS signals, the number of network cameras 121, the GOP cycle, and the like. As described later, the control unit 1245 can calculate the I frame generation timing to be set for each network camera 121 based on the information stored in the main storage unit 1244, and can set it for each camera. The network I/F 1246 is an interface for transmitting the I frame generation timing on the main storage unit 1244 to each camera via the network.

FIG. 5 shows the operation when the system control device 124 of this embodiment sets the I frame generation timing for each network camera 121. The system control device 124 calculates the I frame generation timing to be set for each camera from the time synchronized with GPS, the number of network cameras 121, and the GOP period. As a simple example, if the number of network cameras 121 is 10 and the GOP period of all cameras is 10 seconds, set each camera so that the I frame generation timing of each camera is shifted by 1 second. conduct. Furthermore, if the number of network cameras is 10 and the GOP period of all cameras is 1 second, settings are made for each camera so that the I frame generation timing of each camera is shifted by 100 milliseconds.

As described above, according to the video data communication amount smoothing technology of the present embodiment, the video data communication amount, which could not be handled by conventional systems, can be smoothed and can be accommodated within the limited communication band. By performing such control, it is possible to prevent data loss and problems such as stopping the video on the monitor due to data loss.

<Modified example>
In the above embodiment, the plurality of network cameras 121 were configured to output video data that all have the same GOP cycle, but the plurality of network cameras 121 output video data that has a different GOP cycle than other network cameras 121. The configuration may also include a network camera 121 that outputs data.

FIG. 6 shows the operation when the system control device of this modification sets the I frame generation timing for each network camera 121. For example, shorten the GOP cycle of the network camera 121 that photographs doors where many people get on and off (doors that should be checked with particular care), and instead lengthen the GOP cycle of the network camera 121 that photographs doors where few people get on and off. do. This smoothes the entire video data. Specifically, for example, the GOP cycle of camera 1, which photographs doors where many people get on and off, is set to 5 seconds, the GOP cycle of cameras 2 to 8 is set to 10 seconds, and camera 9, which photographs doors where few people get on and off, is set. And the GOP period of camera 10 is set to 20 seconds. The number of people getting on and off the train may be stored in advance for each station or door, or may be detected by image processing, sensors, etc., and the specific means are not critical.

In addition, in the embodiment mentioned above, the case where the present invention is used for train door monitoring was explained. However, the field of application of the present invention is not limited to this. The present invention is generally applicable to camera systems including a plurality of cameras that output video data in the GOP format.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various changes can be made without departing from the gist of the present invention.

100: Camera system, 111 to 116: Vehicle, 121: Network camera, 122: Monitor device, 123: Recording device, 124: System control device, 125: Upper system, 126: Network switch, 1211: Imaging unit, 1212: Code conversion unit, 1213: main storage unit, 1214: control unit, 1215: network I/F, 1216: bus, 1241: GPS antenna, 1242: GPS receiver, 1243: high frequency coaxial cable, 1244: main storage unit, 1245: Control unit, 1246: Network I/F, 1247: Bus.

Claims (6)

A camera system comprising multiple cameras,
The plurality of cameras output video data in GOP format,
The plurality of cameras output video data whose I frame generation timings do not overlap with each other,
camera system. The camera system according to claim 1,
The plurality of cameras are synchronized with a time managed by the camera system, and generate I frames based on the synchronized time.
camera system. The camera system according to claim 1 or 2,
The camera system includes a system control device,
The system control device specifies I frame generation timing for each of the plurality of cameras based on time managed by the camera system.
camera system. The camera system according to claim 2 or 3,
The time managed by the camera system is synchronized with a GPS signal.
camera system. The camera system according to any one of claims 1 to 4,
The plurality of cameras include the camera that outputs video data with a GOP period different from that of the other cameras.
camera system. A method for controlling a camera system including a plurality of cameras, the method comprising:
The plurality of cameras output video data in GOP format,
The plurality of cameras output video data whose I frame generation timings do not overlap with each other,
How to control the camera system.

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