KR20150027645A - Apparatus and method for synchronizating time - Google Patents

Apparatus and method for synchronizating time Download PDF

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Publication number
KR20150027645A
KR20150027645A KR20130106328A KR20130106328A KR20150027645A KR 20150027645 A KR20150027645 A KR 20150027645A KR 20130106328 A KR20130106328 A KR 20130106328A KR 20130106328 A KR20130106328 A KR 20130106328A KR 20150027645 A KR20150027645 A KR 20150027645A
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time
nvr
network camera
time stamp
offset
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KR20130106328A
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Korean (ko)
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KR102040940B1 (en
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차일황
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삼성테크윈 주식회사
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/765—Interface circuits between an apparatus for recording and another apparatus
    • H04N5/77—Interface circuits between an apparatus for recording and another apparatus between a recording apparatus and a television camera
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising

Abstract

The present invention relates to an image processing system including a network camera and an NVR and an operation method thereof, and more particularly, to a time synchronization apparatus and method for synchronizing time between a network camera and an NVR. The time synchronization device synchronizes the time between the network camera and the NVR. The time synchronization device includes an offset setting part for setting an offset as a reference time difference between the network camera and the NVR, a current time stamp information input from the network camera, A noise determination unit for determining that the current time stamp is a timeshift when the input is constantly out of the threshold range and determines that the current time stamp is a time spike as noise, And a setting control unit for setting a time stamp of the NVR by using a time stamp, an offset, and a time variation ratio of the network camera according to a noise determination result.

Figure P1020130106328

Description

[0001] APPARATUS AND METHOD FOR SYNCHRONIZATION TIME [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing system including a network camera and a network video recorder (NVR), and more particularly to a time synchronization apparatus and method for synchronizing time between a network camera and an NVR .

Recently, image processing systems including network cameras such as CCTV and NVR are rapidly spreading. The NVR of the image processing system registers a recording schedule for storing the image data acquired by the camera. In the NVR, the space for storing the image data is designated, and the image data is sequentially stored in the designated space. Then, when the specified space becomes full, the oldest image data is retrieved and deleted, thereby enabling the latest image data to be stored.

At this time, the image processing system should be operated by synchronizing the timestamp recorded in the video and audio frames transmitted by the network cameras having different formats or time with the time stamp of the NVR.

However, in the past, it was determined that the difference between the time stamp and the NVR time stamp recorded in the video and audio frames received from each of the network cameras was due to jitter on the network, and only the jitter on the network was detected and corrected. In this case, a temporal error of the time stamp generated by the network camera or a time stamp difference between the network camera and the NVR causes a temporal error in the image processing system, which causes the performance degradation of the image processing system.

Japanese Patent Application Laid-Open No. 2009-296207

SUMMARY OF THE INVENTION The present invention provides a time synchronization apparatus and method for synchronizing time between a network camera and an NVR by correcting a time stamp that is not received by statistically observing a time stamp of a network camera have.

In addition, a time synchronization apparatus and method for synchronizing time between a network camera and an NVR in consideration of a latency as a delay time for transmitting / receiving a signal when a network environment is unstable during signal transmission / reception between a network camera and an NVR .

The present invention also provides a time synchronization apparatus and method for correcting a time difference occurring when a time incremental variation of a network camera and a time variation of an NVR are different.

According to an aspect of the present invention, there is provided an apparatus for synchronizing time between a network camera and an NVR, the apparatus comprising: an offset setting unit configured to set an offset as a reference time difference between the network camera and the NVR; Setting section; If the time stamp of the current time stamp inputted from the network camera and the time stamp of the previous time stamp are out of the threshold range and is constantly inputted, the current time stamp is determined as a time shift, A noise judging unit for judging whether or not the input signal A calculation unit that calculates a time variation ratio as a ratio of a time variation of the NVR to a time variation of the network camera periodically; And a setting controller for setting a time stamp of the NVR using the time stamp, the offset, and the time variation ratio of the network camera according to the noise determination result.

In the present invention, the setting control unit sets the time stamp of the NVR by multiplying the sum of the current time stamp value of the network camera and the offset value by the time variation ratio with respect to the time shift determination result .

In the present invention, the setting control unit sets the time stamp of the NVR by multiplying the result of the time spike determination by multiplying the prediction time stamp for the network camera and the offset sum result by the time variation ratio .

According to an aspect of the present invention, there is provided a time synchronization method for synchronizing time between a network camera and an NVR, the method comprising the steps of: Setting step; If the time stamp of the current time stamp inputted from the network camera and the time stamp of the previous time stamp are out of the threshold range and is constantly inputted, the current time stamp is determined as a time shift, A noise judgment step of judging the noise level as? Calculating a time variation ratio as a ratio of a time variation of the NVR to a time variation of the network camera periodically; And a setting step of setting a time stamp of the NVR using the time stamp, the offset and the time variation ratio of the network camera according to the noise determination result.

The setting step may include setting a time stamp of the NVR by multiplying the sum of the current time stamp value of the network camera and the offset value by the time variation ratio with respect to the time shift determination result ; And

In the present invention, the setting step may include setting a time stamp of the NVR by multiplying a result of the time spike determination by multiplying the prediction time stamp and the offset sum for the network camera by the time variation ratio .

As described above, according to the present invention, when the diversity of the time information format input from the network camera, the reference time inconsistency, and the time information error occur, the time stamp of the NVR is synchronized using the time stamp of the network camera, Can be improved.

In addition, when the network environment is unstable, the accuracy of the offset between the network camera and the NVR can be improved by considering the latency of the network, and the accuracy can be raised when the time stamp synchronization is performed between the network camera and the NVR.

Also, by correcting the time difference that occurs when the time increment of the network camera and the time difference of the NVR are different, the accuracy can be increased in the time stamp synchronization between the network camera and the NVR.

Furthermore, at the time of the time stamp synchronization between the network camera and the NVR, the computation amount can be minimized by using the statistical information without using the time of the NVR directly.

1 is a view showing the type and format of a time stamp of a network camera.
2 is a graph showing time information input to the image processing system.
3 is a block diagram illustrating a configuration of a time synchronization apparatus included in an image processing system according to an embodiment of the present invention.
4 is a flowchart illustrating an operation of a time synchronization method according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating an operation of a method of setting an NVR time stamp according to a noise determination result in FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The present invention may be represented by functional block configurations and various processing steps. These functional blocks may be implemented in a wide variety of hardware and / or software configurations that perform particular functions. For example, the present invention may include integrated circuit configurations, such as memory, processing, logic, look-up tables, etc., that may perform various functions by control of one or more microprocessors or other control devices Can be adopted. Similar to the components of the present invention that may be implemented with software programming or software components, the present invention may be implemented as a combination of C, C ++, and C ++, including various algorithms implemented with data structures, processes, routines, , Java (Java), assembler, and the like. Functional aspects may be implemented with algorithms running on one or more processors. Further, the present invention can employ conventional techniques for electronic environment setting, signal processing, and / or data processing. Terms such as mechanisms, elements, means, and configurations are widely used and are not limited to mechanical and physical configurations. The term may include the meaning of a series of routines of software in conjunction with a processor or the like.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Referring to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, do.

In the image processing system including the network camera and the NVR, the time information error between the network camera and the NVR may be caused by various types of time stamp format of the network camera, reference time inconsistency of the network camera, time shift, time spike, A change in the frame rate, and a latency.

In detail, FIG. 1 shows a time stamp type and a format of a network camera. Referring to FIG. 1, a type of a time stamp of a network camera is shown in FIG. 1A, and a time stamp format of a network camera is shown in FIG. 1B. Since the type and the format of the network camera are various, the time shift occurs in each network camera, which may cause a time information error between the network camera and the NVR.

In addition, the time information recorded in the video stream captured by the network camera is calculated as the reference time set in the network camera. Since the reference time may be set differently for each network camera, a time information error between the network camera and the NVR have.

Also, the time stamp reference time of the network camera can be changed. The movement of the reference time is referred to as a time shift (timeshift). A time shift is shown in Fig. For example, if the time stamp type and format of the network camera shown in FIG. 1 represent time information of 90 kHz resolution in unsigned 32 bits, an overflow occurs every 13 hours, 15 minutes and 21 seconds at maximum. This time shift occurrence can cause a time information error between the network camera and the NVR.

In addition, time information of a noise characteristic which is temporarily invalid can be input to the network camera, and this error of the temporal time information is called a time spike. A time spike is shown in Figure 2b. This time spike is a temporally inflowing noise as shown above, thereby causing a time information error between the network camera and the NVR.

In addition, there are times when a time stamp cycle of an image frame captured by a network camera is not constant and is slowed down or accelerated. In this case, when the synchronization is performed using only the offset set in the NVR, a time stamp difference between the network camera and the NVR may occur, thereby causing a time information error between the network camera and the NVR.

Furthermore, due to the latency as a delay time occurring during transmission and reception of signals between the network camera and the NVR depending on the network environment, the offset accuracy between the network camera and the NVR may be reduced to cause a time information error between the network camera and the NVR .

Hereinafter, a time synchronization apparatus and method for solving the cause of a time information error between a network camera and an NVR will be described with reference to FIG. 3 to FIG. 3 is a block diagram illustrating a configuration of a time synchronization apparatus included in an image processing apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the image processing apparatus 10 may include a network camera 100, an NVR 200, and a time synchronization apparatus 300.

The network camera 100 may be composed of a single fixed camera having a fixed lens and a fixed photographing range, or a pan-tilt-zoom (PTZ) camera having a variable photographing range. Here, the PTZ camera can easily change various surveillance areas with one camera by pan operation rotated in the horizontal direction, tilt operation rotated in the vertical direction, and zoom in / zoom out operation . The PTZ camera has the advantages of being able to detect the omnidirectional direction and have a uniform resolution because it can be horizontally, vertically, and rotated compared to a single fixed camera. The network camera 100 is connected to the NVR 200 via a network. The monitoring function is controlled by a command from the NVR 200, processes the captured image, and transmits the captured image to the NVR 200 via the network.

The NVR 200 has a built-in viewer and can store and display images taken by the network camera 100 through the network.

The time synchronization apparatus 300 synchronizes the time of the image processing system 10 including the network camera 100 and the NVR 200 using a time stamp. That is, the time stamp of the NVR 200 is synchronized using the time stamp of the network camera 100. The time stamps of the NVR 200 are synchronized based on the time stamps included in the video and audio frames sent by the network camera 100 having different formats or times to synchronize the time of the video processing system 10. [

Here, the time synchronization apparatus 300 may be physically separate from the network camera 100 and the NVR 200, or may be modularized and configured inside the NVR 200. It will be appreciated by those skilled in the art that the components of the time synchronization device 300 are generally a component of the image processing system 10 so that each component can be located inside or outside the NVR 200 without limitation something to do.

The time synchronization apparatus 300 includes a data receiving unit 310, a header information extracting unit 320, an offset setting unit 330, a storage unit 340, a noise determining unit 350, a time variation ratio calculating unit 360 And a setting control unit 370.

The data receiving unit 310 receives data of a packetized element stream (PES) structure including the data obtained by the network camera 100 and the time stamp indicating the time transmitted from the network camera 100. Here, the PES is a repacked stream in which an ES (element ray stream) having an infinite length is packetized and divided into variable lengths, and a packet header is added at the beginning. That is, a PES contains only one type of data (one source). The PES packet header includes an 8-bit stream ID identifying the source and provides time information by adding a timestamp for synchronization.

The header information extracting unit 320 extracts header information including the time stamp of the network camera 100 from the data of the PES structure received by the data receiving unit 310. [ Parses the header from the header information, and extracts the time stamp information of the network camera 100 required in the header.

The offset setting unit 330 compares the current time stamp of the network camera 100 with the current time information of the NVR 200 to set and adjust an offset between the network camera 100 and the NVR 200 do. Here, the offset means a reference time difference between the network camera 100 and the NVR 200. In general, the offset setting is performed under the circumstances such as reconnection between the network camera 100 and the NVR 200 or the time setting of the NVR 200 is changed.

The storage unit 340 stores header information including a time stamp of the network camera 100 extracted by the header information extracting unit 320. In addition, various additional information related to the NVR 200 and a time stamp may be stored.

The noise determination unit 350 determines whether the time information input from the network camera 100 to the NVR 200 based on the time stamp included in the header information is noise. Here, the term " noise " means that temporal information of a temporarily non-valid noise characteristic is input to the NVR 200. [ That is, it means a temporary time information error.

The noise determination unit 350 determines whether the time difference between the time stamp currently input to the network camera 100 and the previously input time stamp is out of the threshold range and determines whether the time stamp currently input and the time stamp previously input If the time difference deviates from the threshold range, it is judged as a preliminary noise. However, when the time difference between the currently input time stamp and the previously inputted time stamp is within the threshold range, it is determined that the preamble is not a noise. If the time stamp of the network camera 100 is constantly exceeded beyond the threshold range after the preliminary noise determination, the preliminary noise is judged as a time shift rather than a noise. If the time stamp of the network camera 100 is within the threshold range If it is continuously deviated and is not constantly inputted, the preliminary noise is judged to be a time noise (time noise).

The time variation ratio calculating unit 360 periodically calculates the time variation ratio as a ratio of the time variation of the NVR 200 to the time variation of the network camera 100. The time variation of the camera 100 indicates the difference between the current time and the previous time of the network camera 100 and the time variation of the NVR 200 indicates the difference between the current time and the previous time of the NVR 200 . The time variation of the network camera 100 and the time variation of the NVR 200 must be constant. When the time variation of the network camera 100 and the time variation of the NVR 200 are not constant, The time information error between the camera 100 and the NVR 200 can be generated. Accordingly, by correcting the time difference by applying the time variation ratio when setting the time stamp of the NVR 200, it is possible to raise the accuracy at the time of the time stamp synchronization between the network camera 100 and the NVR 200.

The setting control unit 370 may use the time stamp of the network camera 100, the offset between the network camera 100 and the NVR 200, the network latency, and the time variation ratio according to the noise determination result of the noise determination unit 350 The time stamp of the NVR 200 is set. The time stamp of the NVR 200 can be obtained by Equation (1).

Figure pat00001

here,

Figure pat00002
Indicates a time stamp value of the NVR 200,
Figure pat00003
Offset represents an offset value between the network camera 100 and the NVR 200 and Latency represents an offset value between the network camera 100 and the NVR 200 according to the network environment, And M represents the time variation ratio as a ratio of the time variation of the NVR 200 to the time variation of the network camera 100.

If the time difference between the currently input time stamp and the previously input time stamp is within the threshold range as a result of the determination by the noise determination unit 350, that is, if the preamble is not the preliminary noise, the setting control unit 370 sets the network latency periodically And acquires a new secondary network latency when latency occurs. Here, the network latency calculation is the result of subtracting the current and previous time stamp difference of the NVR 200 from the difference between the current and previous timestamps of the network camera 100. The setting control unit 370 sets the time variation ratio to the sum of the time stamp value of the network camera 100, the offset value between the network camera 100 and the NVR 200, and the newly acquired secondary network latency And the time stamp of the NVR 200 is reset.

If the network camera 100 determines that the time stamp of the network camera 100 is constantly out of the threshold range and the preliminary noise is a time shift as a result of the determination by the noise determination unit 350, And obtains a new secondary offset between the NVRs 200. The setting control unit 370 multiplies the sum of the time stamp value of the network camera 100, the secondary offset value between the network camera 100 and the NVR 200 and the network latency by the time variation ratio, The time stamp of the terminal 200 is reset.

If the time stamp of the network camera 100 is constantly out of the threshold range as a result of the determination by the noise determination unit 350 and the preliminary noise is determined as a time spike that is an actual noise, 20) with the value of the predicted time stamp. Here, the predicted time stamp is an estimated value obtained from the time information values of the managed network camera 100. However, if it is impossible to acquire the predicted time stamp, the time stamp of the NVR 200 is replaced with the time stamp of the network camera 100, thereby resetting the time stamp of the NVR 200. This case occurs when the time information samples for obtaining the predicted time stamp are insufficient. When acquiring the predicted time stamp, the setting control unit 370 sets a time variation ratio (time variance ratio) between the predicted time stamp value of the network camera 100, the offset value between the network camera 100 and the NVR 200, and the network latency, And resets the time stamp of the NVR 200. [

When the diversity of the time information format input from the network camera 100, the reference time inconsistency, and the error of the time information occur, the time stamp of the NVR 200 is synchronized using the time stamp of the network camera 100, The performance of the processing system can be improved. When the network environment is unstable, the accuracy of offset between the network camera 100 and the NVR 200 is improved by considering the latency of the network, thereby increasing the accuracy of the time stamp synchronization between the network camera 100 and the NVR 200 . Also, by correcting the time difference that occurs when the time increment of the network camera 100 and the time variation of the NVR 200 are different, the accuracy of the time stamp synchronization between the network camera 100 and the NVR 200 can be increased have. Furthermore, at the time of the time stamp synchronization between the network camera 100 and the NVR 200, the calculation time can be minimized by using the statistical information without using the time of the NVR 200 directly.

Next, a time synchronization method according to the present invention will be described with reference to FIGS. 4 and 5. FIG. In the following description, the time synchronization method according to the present invention can be performed inside the time synchronization apparatus 300 with the help of peripheral components as shown in FIG. In the following description, the description of the parts overlapping with the description of Figs. 1 to 3 will be omitted.

4 is a flowchart illustrating an operation of a time synchronization method according to an embodiment of the present invention. 4, the time synchronization apparatus 300 compares the current time stamp of the network camera 100 with the current time information of the NVR 200 to determine the offset between the network camera 100 and the NVR 200 (step S100). Here, the offset means a reference time difference between the network camera 100 and the NVR 200.

Next, the time synchronization apparatus 300 performs a step S200 of determining whether the time information input from the network camera 100 to the NVR 200 is noise based on the time stamp included in the header information. Here, the term " noise " means that temporal information of a temporarily non-valid noise characteristic is input to the NVR 200. [ That is, it means a temporary time information error. The time synchronization apparatus 300 confirms whether the time difference between the time stamp currently input to the network camera 100 and the previously input time stamp is out of the threshold range and determines whether the time stamp currently inputted and the time stamp previously input If the time difference deviates from the threshold range, it is judged as a preliminary noise. However, when the time difference between the currently input time stamp and the previously inputted time stamp is within the threshold range, it is determined that the preamble is not a noise. If the time stamp of the network camera 100 is constantly exceeded beyond the threshold range after the preliminary noise determination, the preliminary noise is judged as a time shift rather than a noise. If the time stamp of the network camera 100 is within the threshold range If it is continuously deviated and is not constantly inputted, the preliminary noise is judged to be a time noise (time noise).

The time synchronization apparatus 300 then performs a step S300 of calculating the time variation ratio as a ratio of the time variation of the NVR 200 to the time variation of the network camera 100 periodically. The time variation of the camera 100 indicates the difference between the current time and the previous time of the network camera 100 and the time variation of the NVR 200 indicates the difference between the current time and the previous time of the NVR 200 . The time variation of the network camera 100 and the time variation of the NVR 200 must be constant. When the time variation of the network camera 100 and the time variation of the NVR 200 are not constant, The time information error between the camera 100 and the NVR 200 can be generated. Accordingly, by correcting the time difference by applying the time variation ratio when setting the time stamp of the NVR 200, it is possible to raise the accuracy at the time of the time stamp synchronization between the network camera 100 and the NVR 200.

The time synchronization device 300 may calculate the time stamp of the network camera 100, the offset between the network camera 100 and the NVR 200 according to the determination result of the noise determination, the time stamp of the network camera 100, A step S400 of setting the time stamp of the NVR 200 using the latency and the time variation ratio is performed. FIG. 5 is a flowchart showing the operation of the NVR time stamp setting method according to the noise determination result.

5, if the time difference between the currently input time stamp and the previously inputted time stamp is within the threshold range as a result of the noise determination, that is, not the preliminary noise, (410) the time stamp of the NVR 200 by multiplying the time stamp value of the network camera 100, the offset value between the network camera 100 and the NVR 200, and the newly acquired secondary network latency, . Here, the time synchronization apparatus 300 periodically checks the network latency and acquires a new secondary network latency when latency occurs. The network latency computation is the result of subtracting the current and previous time stamp differences of the NVR 200 from the difference between the current and previous timestamps of the network camera 100.

When the network camera 100 is judged to be a time shift by inputting the time stamp of the network camera 100 constantly out of the threshold range as a result of the noise judgment and judging the preliminary noise to be a time shift, the time synchronization device 300 may calculate the time stamp value of the network camera 100, The NVR 200 sets the time stamp of the NVR 200 by multiplying the sum of the secondary offset value and the network latency between the camera 100 and the NVR 200 by the time variation ratio (S420). Here, a new secondary offset between the network camera 100 and the NVR 200 is obtained.

When the network camera 100 continuously receives the time stamp out of the threshold range as a result of the noise determination and determines that the preliminary noise is a time spike that is an actual noise, the time synchronization apparatus 300 determines the prediction time of the network camera 100 A stamp value, an offset value between the network camera 100 and the NVR 200, and a network latency are multiplied by a time variation ratio to set a time stamp of the NVR 200 (S430). Here, the predicted time stamp is an estimated value obtained from the time information values of the managed network camera 100. However, if it is impossible to acquire the predicted time stamp, the time stamp of the NVR 200 can be reset by replacing the time value of the current NVR 200 with the time stamp of the network camera 100. This case occurs when the time information samples for obtaining the predicted time stamp are insufficient. When the predicted time stamp is obtained, the time stamp of the NVR 200 is set as described above.

Meanwhile, the present invention can be embodied in computer readable code on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored.

Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device and the like, and also a carrier wave (for example, transmission via the Internet) . In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily deduced by programmers skilled in the art to which the present invention belongs.

The present invention has been described above with reference to preferred embodiments. It will be understood by those skilled in the art that the present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100: Network camera 200: NVR
300: time synchronizer 310: data receiver
320: Header information extracting unit 330: Offset setting unit
340: storage unit 350: noise determination unit
360: time variation ratio calculating unit 370: setting control unit

Claims (6)

As a device to synchronize time between network camera and NVR,
An offset setting unit for setting an offset of the network camera and the NVR as a reference time difference;
If the time stamp of the current time stamp inputted from the network camera and the time stamp of the previous time stamp are out of the threshold range and is constantly inputted, the current time stamp is determined as a time shift, A noise judging unit for judging whether or not the input signal
A calculation unit that calculates a time variation ratio as a ratio of a time variation of the NVR to a time variation of the network camera periodically; And
And a setting controller for setting a time stamp of the NVR using the time stamp, the offset, and the time variation ratio of the network camera according to the noise determination result. 2. The apparatus according to claim 1,
Wherein the time stamp setting unit sets the time stamp of the NVR by multiplying the sum of the current time stamp value of the network camera and the offset value by the time variation ratio with respect to the time shift determination result. 2. The apparatus according to claim 1,
Wherein the time stamp setting unit sets the time stamp of the NVR by multiplying the prediction time stamp for the network camera and the offset sum result by the time variation ratio with respect to the time spike determination result. As a method of synchronizing the time between the network camera and the NVR,
An offset setting step of setting an offset of the network camera and the NVR as a reference time difference;
If the time stamp of the current time stamp inputted from the network camera and the time stamp of the previous time stamp are out of the threshold range and is constantly inputted, the current time stamp is determined as a time shift, A noise judgment step of judging the noise level as?
Calculating a time variation ratio as a ratio of a time variation of the NVR to a time variation of the network camera periodically; And
And setting the time stamp of the NVR using the time stamp, the offset, and the time variation ratio of the network camera according to the noise determination result. 5. The method according to claim 4,
And setting a time stamp of the NVR by multiplying the sum of the current time stamp value and the offset value of the network camera by the time variation ratio with respect to the time shift determination result. Way. 5. The method according to claim 4,
And setting a time stamp of the NVR by multiplying a prediction time stamp for the network camera and the offset sum result by the time variation ratio with respect to the time spike determination result.
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