KR102638599B1 - Camera, method and computer program for operating syncronization between a plurality of cameras - Google Patents

Abstract

A camera that performs synchronization between a plurality of cameras includes a receiver that receives a first synchronization signal and a second synchronization signal generated based on a preset period from the main camera, a reception time for the first synchronization signal, and a reception time for the second synchronization signal. It may include a first determination unit that determines network validity between the main camera and the camera based on the reception time, and a second determination unit that determines the validity of the internal frame of the camera based on the first frame creation time.

Description

Camera, method and computer program for performing synchronization between a plurality of cameras {CAMERA, METHOD AND COMPUTER PROGRAM FOR OPERATING SYNCRONIZATION BETWEEN A PLURALITY OF CAMERAS}

The present invention relates to a camera, method, and computer program for performing synchronization between a plurality of cameras.

Referring to FIG. 1A, in the existing shooting synchronization method, the camera controller synchronizes the cameras by generating a synchronization signal and transmitting the generated synchronization signal to the camera. At this time, the synchronization signal is transmitted to the camera through an optical cable to exclude signal delay.

As such, in a wired environment, it is necessary to build an optical cable to synchronize camera shooting and receive video data. Accordingly, expensive optical cable installation costs are incurred, and installation of optical cables may be subject to environmental restrictions.

In the case of current broadcasting services, since shooting synchronization between cameras is not essential, video data can be compressed after shooting and transmitted through a WIFI network or cellular network. However, in the case of time slice video, due to restrictions on shooting synchronization, Service is not possible.

Meanwhile, the image capture environment in a wireless environment may be configured as shown in FIG. 1B. Referring to FIG. 1B, each camera 120 is connected to the AP device 110 to form the same network and is configured to communicate with the camera controller 100. Here, the camera controller 100 transmits commands to start and stop filming the cameras to each camera 120.

Looking at the characteristics of video shooting in such a wireless environment, delays occur due to wireless signal interference, delays occur due to packet collisions that are higher than in a wired environment, and delays occur due to switching of the AP device 110. Additionally, considering the conditions for synchronization between cameras (e.g., 1/2 ms) required when shooting video, synchronization between cameras in a wireless environment is almost impossible. Moreover, the conditions for confirming shooting synchronization between cameras are difficult. Specifically, for shooting synchronization, commands must be transmitted from the camera controller 100 to each camera 120 at the same time so that each camera can shoot at the same time. In the case of a wired environment, the phase difference is not large because the camera controller 100 transmits the shooting command to each camera 120 through an optical cable. However, in a wireless environment, there is a difference in the reception time of the shooting command depending on radio interference or distance. Referring to Figure 1c, the delay time from the transmission time of the shooting command to the reception time is α≤ It appears as ≤β.

For shooting synchronization, there is a minimum( ) should be the goal.

However, in a wireless environment, the transmission and reception delay time for shooting commands ( ), there is no way to measure it. To measure the actual delay time, use the following ① and ②.

① = -

② = -

In case ①, the delay time cannot be measured unless the transmitting device and receiving device are absolutely synchronized. For example, in order to measure the synchronization signal between the camera controller 100 and camera 1, Even if you measure and save it, Since is the time generated by the camera controller 100, the difference between the two is meaningful under the premise that the camera controller 100 and camera 1 are synchronized.

In case ②, the absolute time at which the camera controller 100 transmitted the shooting command ( ) and Camera 1 responds back to the camera controller 100 to determine whether or not the shooting command has been received, and the time at which it was received ( ) is a method of checking the difference in the camera controller 100. However, it is impossible to determine whether the delay time occurred during the process of transmitting the shooting command to Camera 1 or in response to Camera 1's shooting command. In addition, even if the delay time satisfies the requirement (②), synchronization determination is impossible due to the high uncertainty due to differences in wireless environments.

Meanwhile, even if the network problem is solved and shooting commands are transmitted to each camera simultaneously, synchronization is impossible due to the delay inside each camera. Referring to Figure 1d, Camera 1 receives a shooting command to start shooting. After the time, the actual shooting time of camera 1 is + am. The problem is latency ( ) is not the same for each camera.

Meanwhile, communication with the camera controller is essential for shooting synchronization in a wireless environment. To communicate with the camera controller, each camera must connect to an AP device. Accordingly, there is an inevitable distance limit where each camera must be located within a reachable distance from the AP device.

Japanese Patent Publication No. 2006-227245 (published on August 31, 2006)

The present invention is intended to solve the problems of the prior art described above, and seeks to perform synchronization between a plurality of wirelessly connected cameras. Specifically, the present invention seeks to perform synchronization between cameras based on network validity between cameras and internal frame validity within the cameras.

However, the technical challenges that this embodiment aims to achieve are not limited to the technical challenges described above, and other technical challenges may exist.

As a technical means for achieving the above-described technical problem, a camera that performs synchronization between a plurality of cameras according to the first aspect of the present invention includes a first synchronization signal and a second synchronization signal generated based on a preset period from the main camera. a receiving unit that receives; a first determination unit that determines network validity between the main camera and the camera based on the reception time of the first synchronization signal and the reception time of the second synchronization signal; and a second determination unit that determines the validity of the internal frame of the camera based on the first frame generation time.

A method of performing synchronization between a plurality of cameras performed by a camera according to a second aspect of the present invention includes receiving a first synchronization signal and a second synchronization signal generated based on a preset period from the main camera; determining network validity between the main camera and the camera based on the reception time for the first synchronization signal and the reception time for the second synchronization signal; and determining the validity of the internal frame of the camera based on the first frame creation time.

A computer program stored in a computer-readable recording medium including a sequence of instructions for performing synchronization between a plurality of cameras by a camera according to the third aspect of the present invention, when executed by a computing device, based on a preset cycle from the main camera Receive a first synchronization signal and a second synchronization signal generated by, and determine network validity between the main camera and the camera based on the reception time for the first synchronization signal and the reception time for the second synchronization signal. and may include a sequence of commands for determining internal frame validity of the camera based on the first frame generation time.

The above-described means for solving the problem are merely illustrative and should not be construed as limiting the present invention. In addition to the exemplary embodiments described above, there may be additional embodiments described in the drawings and detailed description of the invention.

According to any one of the means for solving the problems of the present invention described above, the present invention can perform synchronization between a plurality of wirelessly connected cameras. Specifically, the present invention can perform synchronization between cameras based on network validity between cameras and camera internal frame validity.

1A to 1D are diagrams for explaining an existing camera synchronization method.
Figure 2 is a block diagram of a camera, according to an embodiment of the present invention.
3A to 3B are diagrams showing an environment configuration for camera synchronization according to an embodiment of the present invention.
Figure 4 is a diagram showing the camera synchronization sequence according to an embodiment of the present invention.
Figure 5 is a flowchart showing a camera synchronization method according to an embodiment of the present invention.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only the case where it is "directly connected," but also the case where it is "electrically connected" with another element in between. . Additionally, when a part "includes" a certain component, this means that it may further include other components rather than excluding other components, unless specifically stated to the contrary.

In this specification, 'part' includes a unit realized by hardware, a unit realized by software, and a unit realized using both. Additionally, one unit may be realized using two or more pieces of hardware, and two or more units may be realized using one piece of hardware.

In this specification, some of the operations or functions described as being performed by a terminal or device may instead be performed on a server connected to the terminal or device. Likewise, some of the operations or functions described as being performed by the server may also be performed on a terminal or device connected to the server.

Hereinafter, specific details for implementing the present invention will be described with reference to the attached configuration diagram or processing flow diagram.

Figure 2 is a block diagram of the camera 20, according to one embodiment of the present invention.

Referring to FIG. 2, the camera 20 may include a reception unit 200, a first determination unit 210, a second determination unit 220, a third determination unit 230, and a transmission unit 240. . However, the camera 20 shown in FIG. 2 is only one implementation example of the present invention, and various modifications are possible based on the components shown in FIG. 2.

Hereinafter, FIG. 2 will be described with reference to FIGS. 3A to 4.

For synchronization between cameras, the present invention can configure an environment in which multiple cameras can be connected to each AP device based on the number of cameras connected to each AP device preset, as shown in FIG. 3A. Referring to FIG. 3A, when the camera controller 100 connects to the first AP device, the first AP device and each other AP device communicating with the first AP device all cameras connected by wire are connected to the camera controller 100. ) can be relayed to communicate with. By having multiple AP devices like this, you can escape from the constraints of distance due to installation.

A plurality of cameras may be grouped into a plurality of groups according to preset criteria in the form of a hierarchical structure. At this time, the camera belonging to the group corresponding to the highest level serves as a reference for synchronization.

For example, referring to FIGS. 3A and 3B together, the group corresponding to the first layer may include {camera 1}. Here, Camera 1 belonging to the first layer can be set as the main camera for synchronization between cameras.

The group corresponding to the second layer mapped to camera 1 may include {camera 2, camera 3}.

Here, Camera 1, which corresponds to the main camera, may be included in the group corresponding to the upper layer, and {Camera 2, Camera 3} may be included in the group corresponding to the lower layer of the layer to which Camera 1 belongs.

The group corresponding to the third layer mapped to camera 2 includes {camera 4, camera 5, camera 6}, and the group corresponding to the third layer mapped to camera 3 includes {camera 7, camera 8, camera 9} may be included.

Here, {camera 4, camera 5, camera 6}, {camera 7, camera 8, camera 9} may be included in a group corresponding to a lower layer of the layer belonging to {camera 2, camera 3}.

The synchronization standard of {camera 2, camera 3} belonging to the second layer is based on the synchronization signal generated by {camera 1} belonging to the first layer. The synchronization criteria of {camera 4, camera 5, camera 6} and {camera 7, camera 8, camera 9} belonging to the third layer are based on the synchronization signal generated by {camera 2, camera 3} belonging to the second layer. do.

After synchronization between the first layer and the second layer, synchronization between the second layer and the third layer may be performed.

Hereinafter, with reference to FIGS. 2 and 3B, the main camera is Camera 1, the camera 20 is Camera 2, and at least one fellow camera in the lower layer mapped to the camera 20 is named Camera 4. I decided to do it.

The receiver 200 may receive a first synchronization signal and a second synchronization signal generated based on a preset period from Camera 1, which corresponds to the main camera. Here, camera 1 may be included in the group corresponding to the first layer, and camera 20 (camera 2) may be included in the group corresponding to the second layer, which is a lower layer of the first layer.

In a wireless network environment, synchronization between Camera 1 and Camera 2 can be performed only when Camera 1 transmits a synchronization signal to Camera 2 without delay.

To this end, the first determination unit 210 may determine network validity by confirming that there is no delay in receiving a synchronization signal on the wireless network.

Specifically, the first determination unit 210 determines the network validity between Camera 1 (main camera) and Camera 2 (camera 20) based on the reception time for the first synchronization signal and the reception time for the second synchronization signal. You can judge about it.

Referring to FIG. 1C for a moment, when camera 1 transmits the first synchronization signal and the second synchronization signal to camera 2 every 1/fps cycle, the transmission time for the first synchronization signal ( ) and transmission time for the second synchronization signal ( ) can be expressed, for example, as [Equation 1].

[Equation 1]

The first determination unit 210 determines the reception interval of the synchronization signal based on the reception time for the first synchronization signal and the reception time for the second synchronization signal ( ) can be obtained. For example, the reception interval of the synchronization signal can be calculated through [Equation 2] and [Equation 3].

[Equation 2]

[Equation 3]

The first determination unit 210 can confirm the network validity between Camera 1 and Camera 2 by determining whether the difference between the reception time for the first synchronization signal and the reception time for the second synchronization signal is less than or equal to a preset threshold. there is. Here, the threshold can be set based on the delay time of the synchronization signal.

For example, the first determination unit 210 determines the network validity between Camera 1 and Camera 2 when the difference between the reception time for the first synchronization signal and the reception time for the second synchronization signal is less than a preset threshold. I can admit it.

After this, Camera 2 can start filming when it is determined that the network between Camera 1 and Camera 2 is validated.

Meanwhile, due to internal factors of Camera 2, the first frame generation time upon starting shooting ( ) will have different values depending on the unique characteristics of camera 2 or the moment of the actual synchronization command. For synchronization of camera 2, the conditions shown in [Equation 4] must be satisfied, for example.

[Equation 4]

The second determination unit 220 may determine the validity of the internal frame of camera 2 based on the initial frame creation time.

The second determination unit 220 derives the first frame generation time from the time shooting starts, determines whether the derived first frame generation time is a multiple of the preset Frame Per Second (FPS), and determines whether the first frame generation time of Camera 2 is You can check the validity of the internal frame.

If the multiple of the preset number of frames per second does not have a natural number, filming by Camera 2 may be stopped.

For example, if the first frame generation time corresponds to a multiple of the preset number of frames per second, the second determination unit 220 may recognize the validity of the internal frame of camera 2.

If it is determined that the internal frame of camera 2 is valid, the transmitter 240 may transmit a synchronization signal to at least one fellow camera (camera 4) mapped to camera 2. Here, Camera 4 may be included in a group corresponding to a lower layer of the group that includes Camera 2.

Meanwhile, the overall synchronization order between multiple cameras with a hierarchical structure is shown in FIG. 4. Referring to FIG. 4, Camera 1 (main camera) belonging to the first layer operates in the On state, and periodically generates synchronization signals (first synchronization signal, second synchronization signal) accordingly. It is transmitted to Camera 2 and Camera 3 belonging to layer 2.

Each of Camera 2 and Camera 3 belonging to the second layer can confirm network validity with Camera 1 based on the reception time for the first synchronization signal and the reception time for the second synchronization signal received from Camera 1.

When the network validity with camera 1 is confirmed, each of camera 2 and camera 3 belonging to the second layer can set the camera operation state to on and start shooting.

Each of Camera 2 and Camera 3 belonging to the second layer can check internal frame validity by determining whether the first frame creation time derived from the start of filming is a multiple of the preset frames per second (FPS).

When the internal frame validity is confirmed in each of Camera 2 and Camera 3 belonging to the second layer, Camera 2 periodically sends a synchronization signal (third synchronization signal, fourth synchronization signal) to each of Camera 4, Camera 5, and Camera 6 mapped to Camera 2. signal), and Camera 3 may periodically transmit a synchronization signal (a third synchronization signal, a fourth synchronization signal) to each of Camera 7, Camera 8, and Camera 9 mapped to Camera 3.

Each of Cameras 4, Camera 5, and Camera 6 belonging to the third layer can confirm network validity with Camera 2 based on the reception time of the third synchronization signal and the reception time of the fourth synchronization signal.

Each of Camera 7, Camera 8, and Camera 9 belonging to the third layer can confirm network validity with Camera 3 based on the reception time of the third synchronization signal and the reception time of the fourth synchronization signal.

When the network validity with Camera 2 is confirmed, each of Cameras 4, Camera 5, and Camera 6 belonging to the third layer can set the camera operation state to on and start shooting.

Each of Camera 4, Camera 5, and Camera 6 belonging to the third layer can check internal frame validity by determining whether the first frame creation time derived from the start of filming is a multiple of the preset frames per second (FPS).

When the network validity with camera 3 is confirmed, each of cameras 7, camera 8, and camera 9 belonging to the third layer can set the camera operation state to on and start shooting.

Each of Camera 7, Camera 8, and Camera 9 belonging to the third layer can check internal frame validity by determining whether the first frame creation time derived from the start of filming is a multiple of the preset frames per second (FPS).

Meanwhile, the third determination unit 230 may determine the synchronization validity between Camera 1 and Camera 2 based on the reception time of the synchronization validity command transmitted from Camera 1 and the frame creation time in Camera 2.

After determining the network validity between Camera 1 and Camera 2 and the internal frame validity of Camera 2 (pre-synchronization process), the third determination unit 230 aperiodically monitors Camera 1 and Camera 2 while each of Camera 1 and Camera 2 is filming. The effectiveness of synchronization between Camera 2 (post-synchronization process) can be determined.

For example, when receiving a synchronization validity command including the creation time of the 31st frame generated in camera 1, the third determination unit 230 determines the generation time of the 31st frame generated in camera 2 ( ) and the reception time ( ), and the derived difference value is the critical time value ( ) or less. The derived difference value is the critical time value ( ), the third determination unit 230 may determine that synchronization has been performed between Camera 1 and Camera 2.

Meanwhile, those skilled in the art will know that the reception unit 200, the first determination unit 210, the second determination unit 220, the third determination unit 230, and the transmission unit 240 are each implemented separately, or one or more of them. It will be fully understood that this can be integrated and implemented.

Figure 5 is a flowchart showing a camera synchronization method according to an embodiment of the present invention.

Referring to FIG. 5 , in step S501, the main camera 50 may transmit a first synchronization signal generated based on a preset cycle to the camera 20.

In step S503, the main camera 50 may transmit a second synchronization signal generated based on a preset cycle to the camera 20.

In step S505, the camera 20 determines network validity between the main camera 50 and the camera 20 based on the reception time for the first synchronization signal and the reception time for the second synchronization signal received from the main camera 50. You can judge.

If the network validity between the main camera 50 and the camera 20 is recognized in step S507, the camera 20 can start shooting in step S509.

In step S511, the camera 20 derives the first frame creation time from the point in time when shooting starts, determines whether the derived first frame creation time corresponds to a multiple of the preset number of frames per second, and confirms the validity of the internal frame of the camera 20. You can.

If the validity of the internal frame of the camera 20 is recognized in step S513, the camera 20 may transmit a synchronization success message to the main camera 50 in step S515.

In step S517, if the validity of the internal frame of the camera 20 is recognized, the camera 20 may transmit a synchronization signal to the fellow camera 52 mapped to the camera 20.

In step S519, the camera 20 may enter standby mode if the network validity between the main camera 50 and the camera 20 is not recognized.

In step S521, if the validity of the internal frame of the camera 20 is not recognized, the camera operation state may be changed to the Off state.

In the above description, steps S501 to S521 may be further divided into additional steps or combined into fewer steps, depending on the implementation of the present invention. Additionally, some steps may be omitted or the order between steps may be changed as needed.

One embodiment of the present invention may also be implemented in the form of a recording medium containing instructions executable by a computer, such as program modules executed by a computer. Computer-readable media can be any available media that can be accessed by a computer and includes both volatile and non-volatile media, removable and non-removable media. Additionally, computer-readable media may include all computer storage media. Computer storage media includes both volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data.

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as single may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims described below rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

20: Camera
200: Receiving unit
210: Judgment 1
220: Second Judgment Department
230: Third Judicial Branch
240: Transmission unit

Claims (19)

In a camera that performs synchronization between multiple cameras,
a receiving unit that receives a first synchronization signal and a second synchronization signal generated based on a preset period from the main camera;
a first determination unit that determines network validity between the main camera and the camera based on the reception time of the first synchronization signal and the reception time of the second synchronization signal; and
A second determination unit that determines the validity of the internal frame of the camera based on the first frame creation time
Including,
The second determination unit derives the first frame generation time from the point in time when the camera starts shooting,
A camera that checks the validity of the internal frame based on the first frame creation time and a preset number of frames per second (FPS).
According to claim 1,
The first determination unit determines whether the difference between the reception time for the first synchronization signal and the reception time for the second synchronization signal is less than or equal to a preset threshold to confirm network validity between the main camera and the camera, and ,
The camera wherein the threshold is set based on the delay time of the synchronization signal.
According to claim 2,
The camera starts shooting when it is determined that network validity between the main camera and the camera is recognized.
delete According to claim 1,
When it is determined that the internal frame is valid, a transmission unit that transmits a synchronization signal to at least one fellow camera mapped to the camera.
It further includes a camera.
According to claim 1,
A third determination unit that determines synchronization validity between the main camera and the camera based on the reception time of the synchronization validity command transmitted from the main camera and the frame creation time in the camera.
It further includes a camera.
According to claim 5,
A camera wherein the plurality of cameras are grouped into a plurality of groups according to preset criteria in the form of a hierarchical structure.
According to claim 7,
The main camera is included in the group corresponding to the upper layer,
The camera is included in a group corresponding to a lower layer of the upper layer.
According to claim 7,
A camera wherein the fellow camera is included in a group corresponding to a lower layer of the group including the camera.
In a method of performing synchronization between a plurality of cameras performed by a camera,
Receiving a first synchronization signal and a second synchronization signal generated based on a preset period from the main camera;
determining network validity between the main camera and the camera based on the reception time for the first synchronization signal and the reception time for the second synchronization signal; and
Determining internal frame validity of the camera based on the first frame creation time
Including,
The step of determining the validity of the internal frame of the camera is
Deriving the first frame creation time from the point in time when the camera starts shooting; and
A method of performing synchronization, including the step of checking the internal frame validity based on the first frame generation time and a preset number of frames per second (FPS).
According to claim 10,
The step of determining network validity between the main camera and the camera is
Confirming network validity between the main camera and the camera by determining whether a difference between the reception time for the first synchronization signal and the reception time for the second synchronization signal is less than or equal to a preset threshold,
A method of performing synchronization, wherein the threshold is set based on the delay time of the synchronization signal.
According to claim 11,
Starting filming when it is determined that the network validity between the main camera and the camera is recognized.
A method of performing synchronization further comprising:
delete According to claim 10,
When it is determined that the internal frame is valid, transmitting a synchronization signal to at least one fellow camera mapped to the camera.
A method of performing synchronization further comprising:
According to claim 10,
Determining synchronization validity between the main camera and the camera based on the reception time of the synchronization validity command transmitted from the main camera and the frame creation time in the camera.
A method of performing synchronization further comprising:
According to claim 14,
A method of performing synchronization, wherein the plurality of cameras are grouped into a plurality of groups according to preset criteria in a hierarchical structure.
According to claim 16,
The main camera is included in the group corresponding to the upper layer,
A method of performing synchronization, wherein the camera is included in a group corresponding to a lower layer of the upper layer.
According to claim 16,
A method of performing synchronization, wherein the fellow camera is included in a group corresponding to a lower layer of the group containing the camera.
A computer program stored on a computer-readable recording medium comprising a sequence of instructions for performing synchronization between a plurality of cameras by a camera,
When the computer program is executed by a computing device,
Receiving a first synchronization signal and a second synchronization signal generated based on a preset period from the main camera,
Determine network effectiveness between the main camera and the camera based on the reception time for the first synchronization signal and the reception time for the second synchronization signal,
Determine the validity of the internal frame of the camera based on the first frame generation time,
Contains a sequence of commands for deriving the first frame generation time from the point in time when shooting in the camera starts and confirming the internal frame validity based on the first frame generation time and a preset number of frames per second (FPS). A computer program stored on a computer-readable recording medium.

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