Imaging system, recording device, recording method and program

Abstract

To provide an imaging system, a recording device, a recording method and a program which can properly record moving image data before and after an event occurrence time point.SOLUTION: A recording device 1 comprises: a moving image take-out part 112 which takes out image data constituting moving image data stored in a moving image buffer 121 from the moving image buffer 121 at a second time point after a first time point at which the moving image data is acquired by a moving image acquisition part 111, and stores the moving image data in a moving image storage part 131; an extraction period specification part 116 which specifies a period including a time point at which only a delay time elapses via the moving image buffer 121 from an event occurrence time point as an extraction period for extracting a portion of the moving image data stored in the moving image storage part 131 when an event occurs; and a moving image extraction part 117 which extracts a portion of the moving image data corresponding to the aforementioned extraction period from the moving image data stored in the moving image storage part 131.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an imaging system, a recording device, a recording method, and a program. [Background technology]

[0002] A system has been proposed that uses an imaging means to monitor a specific target, and when an abnormality occurs in the target, the acquisition of information indicating the occurrence of the abnormality is used as a trigger to store image data captured before and after the occurrence of the abnormality in a storage means (see, for example, Patent Document 1). As a system having a similar function to this system, a system has been provided in which a network camera is used as the imaging means, and a recording device for recording image data captured by the network camera before and after the occurrence of the abnormality is connected to the network camera via a network. In such a system, for example, when the recording device acquires information indicating the occurrence of an abnormality, image data before and after the occurrence of the abnormality is extracted from the image data transmitted from the network camera to the recording device and stored. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-193283 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a system in which a network camera and a recording device are connected via a network as described above, in order to prevent image data loss due to communication delays and to achieve stable video transmission, the recording device generally buffers image data acquired from the network camera in a temporary storage means and then accumulates the image data in a storage. In this case, a time lag occurs between the time when the image data after passing through the buffer is saved in the storage and the time when the image data is actually captured. Therefore, there is a risk that the desired image data cannot be obtained even if image data around the time when the abnormality occurs is acquired based on the time when each image data is saved in the storage.

[0005] The present invention has been made in view of the above, and has an object to provide an imaging system, a recording device, a recording method, and a program that are capable of appropriately recording moving image data before and after an event occurs. [Means for solving the problem]

[0006] In order to achieve the above object, an imaging system according to the present invention comprises: An imaging device; a recording device connected to the imaging device via a network, The recording device is a video buffer for temporarily storing video data; a video acquisition unit that acquires the video image data transmitted from the imaging device and stores the video image data in the video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; Image data constituting the moving image data stored in the video buffer is taken out from the video buffer. Corresponding to extraction time information indicating the time when the image data was extracted, a video extracting unit for storing the video in the video storage unit; a delay time calculation unit that calculates a delay time caused by passing through the video buffer; When a preset event occurs in a subject to be imaged by the imaging device, Regarding the retrieval time information, From the time when the event occurred , the delay time calculation unit calculates When the delay time has elapsed A set period of time is set around the center of thean extraction period specification unit that specifies a period as an extraction period for extracting a portion of the video data stored in the video storage unit; The video extracting unit extracts a portion of the video data corresponding to the extraction period from the video data stored in the video storage unit.

[0007] From another viewpoint, the recording device according to the present invention is A recording device connected to an imaging device via a network, a video buffer for temporarily storing video data; a video acquisition unit that acquires the video image data transmitted from the imaging device and stores the video image data in the video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; Image data constituting the moving image data stored in the video buffer is taken out from the video buffer. Corresponding to extraction time information indicating the time when the image data was extracted, a video extracting unit for storing the video in the video storage unit; a delay time calculation unit that calculates a delay time caused by passing through the video buffer; When a preset event occurs in a subject to be imaged by the imaging device, Regarding the retrieval time information, From the time when the event occurred The delay time calculated by the delay time calculation unit When the delay time has elapsed A set period of time is set around the center of the an extraction period specification unit that specifies a period as an extraction period for extracting a portion of the video data stored in the video storage unit; The video data extracting unit extracts a portion of the video data corresponding to the extraction period from the video data stored in the video storage unit.

[0008] A recording method according to another aspect of the present invention comprises: A method for recording moving image data received from an imaging device via a network, comprising: acquiring video data transmitted from the imaging device and storing the video data in a video buffer that temporarily stores the video data; Image data constituting the moving image data stored in the video buffer is taken out from the video buffer. Corresponding to extraction time information indicating the time when the image data was extracted,storing the moving image data acquired from the imaging device in a moving image storage unit; a delay time calculation step of calculating a delay time caused by passing through the video buffer; When a preset event occurs in a subject to be imaged by the imaging device, Regarding the retrieval time information, From the time when the event occurs, The delay time calculated in the delay time calculation step The point at which the delay time has elapsed In the center, a preset period of time is set before and after specifying a period as an extraction period for extracting a part of the video data stored in the video storage unit; Extracting a portion of the moving image data corresponding to the extraction period from the moving image data stored in the moving image storage unit.

[0009] From another aspect, the program according to the present invention is Computer, a video buffer for temporarily storing video data; a video acquisition unit that acquires video image data transmitted from an imaging device and stores the video data in the video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; Image data constituting the moving image data stored in the video buffer is taken out from the video buffer. Corresponding to extraction time information indicating the time when the image data was extracted, a moving image extracting unit for storing the moving image in the moving image storage unit; a delay time calculation unit that calculates a delay time caused by passing through the video buffer; When a preset event occurs in a subject to be imaged by the imaging device, Regarding the retrieval time information, From the time when the event occurs, The delay time calculated by the delay time calculation unit The point at which the delay time has elapsed In the center, a preset period of time is set before and after an extraction period specifying unit that specifies a period as an extraction period for extracting a portion of the video data stored in the video storage unit; a moving image extracting unit that extracts a portion of the moving image data corresponding to the extraction period from the moving image data stored in the moving image storage unit; Function as. Effect of the Invention

[0010] According to the imaging system of the present invention, when a preset event occurs in an imaging target by an imaging device, an extraction period determination unit determines a period including a time point when a delay time caused by passing through a video buffer has elapsed as an extraction period for extracting a part of video data stored in a video storage unit. This makes it possible to determine the extraction period based on the delay time so that at least the time point of the event occurrence is included in the extraction period, and therefore makes it possible to appropriately record video data before and after the time point of the event occurrence. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing a configuration of an imaging system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a hardware configuration of the imaging system according to the first embodiment. [Diagram 3] FIG. 2 is a diagram showing a functional configuration of the imaging system according to the first embodiment. [Figure 4] FIG. 2 is an explanatory diagram of the operation of the imaging system according to the first embodiment. [Diagram 5] 5 is a flowchart showing an example of the flow of a recording process executed by the imaging device according to the first embodiment. [Figure 6] 10A and 10B are diagrams illustrating the operation of an imaging system according to a comparative example. [Figure 7] FIG. 11 is a diagram showing a functional configuration of an imaging system according to a second embodiment of the present invention. [Figure 8] FIG. 2 is a diagram showing a part of the protocol stack of RTP (Real-time Transport Protocol). [Figure 9] 11 is a flowchart showing an example of the flow of a recording process executed by an imaging device according to the second embodiment. [Figure 10] FIG. 11 is a diagram showing a functional configuration of an imaging system according to a third embodiment of the present invention. [Figure 11] 13 is a flowchart showing an example of the flow of a recording process executed by an imaging device according to the third embodiment. [Figure 12]FIG. 13 is a diagram showing a functional configuration of an imaging system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Embodiment 1) An imaging system according to an embodiment of the present invention will be described in detail below with reference to Figs. 1 to 4. The imaging system according to this embodiment includes an imaging device and a recording device connected to the imaging device via a network. The recording device includes a video acquisition unit that acquires video data transmitted from the imaging device and stores it in a video buffer, a video extraction unit that extracts image data constituting the video data stored in the video buffer from the video buffer at a second time point after the first time point when the video acquisition unit acquires the image data, and stores the image data in a video storage unit, an extraction period determination unit that, when a preset event occurs in a subject to be imaged by the imaging device, determines a period including a time point when a delay time due to passing through the video buffer has elapsed from the event occurrence time point when the event occurs as an extraction period for extracting a part of the video data stored in the video storage unit, and a video extraction unit that extracts a part of the video data corresponding to the extraction period from the video data stored in the video storage unit. This embodiment will be described in detail below.

[0013] The imaging system according to the present embodiment includes a network camera 2 and a recording device 1 connected to the network camera 2 via a network NW, as shown in FIG. 1. The network NW is, for example, a wired LAN (Local Area Network). The network camera 2 is used, for example, as a surveillance camera for monitoring production equipment. As shown in FIG. 2, the network camera 2 is an imaging device including a CPU (Central Processing Unit) 201, a main memory 202, an auxiliary memory 203, an imaging unit 204, a wired communication interface 206, and a bus 209 connecting the various units. The main memory 202 is composed of a volatile memory such as a RAM (Random Access Memory). The auxiliary memory 203 is composed of a non-volatile memory such as a ROM (Read Only Memory), and stores a program for controlling the network camera 2. The wired communication interface 206 is connected to the network NW and transmits and receives data via the network NW. The CPU 201 loads a program stored in the auxiliary memory unit 203 into the main memory unit 202 and executes it, thereby functioning as a video transmission unit 211 that transmits video data indicating video images captured by the imaging unit 204 to the recording device 1, as shown in FIG. 3.

[0014] 2 has a captured image buffer 221 for temporarily storing video data indicating a video captured by the imaging unit 204, as shown in Fig. 3. The video transmission unit 211 repeats a process of transmitting one frame of image data constituting the video data by the imaging unit 204 to the recording device 1, for example, every time writing of one frame of image data constituting the video data by the imaging unit 204 to the captured image buffer 221 is completed. The video transmission unit 211 also transmits the video data stored in the captured image buffer 221 to the recording device 1, for example, by RTP (Real-time Transport Protocol).

[0015] Returning to FIG. 2, the recording device 1 includes a CPU 101, a main memory unit 102, an auxiliary memory unit 103, a wired communication interface 106, an abnormality detection interface (hereinafter referred to as an "abnormality detection I / F") 107, a clock unit 108, and a bus 109 connecting the various units. The main memory unit 102 is composed of a volatile memory such as a RAM, and is used as a working area for the CPU 101. The auxiliary memory unit 103 is composed of a non-volatile memory such as a ROM, or an SSD (Solid State Drive), an HDD (Hard Disk Drive), or the like, and stores a program for controlling the recording device 1. The wired communication interface 106 is connected to a network NW, and transmits and receives data via the network NW. The abnormality detection I / F 107 is an interface for acquiring trigger information. The abnormality detection I / F 107 may be, for example, a serial port such as RS-232. The trigger information is based on, for example, an abnormality detection signal output from a production facility when an abnormality occurs in the production facility that is the subject of imaging by the network camera 2. The timing unit 108 has, for example, a hardware timer.

[0016] The CPU 101 loads the program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as a video acquisition unit 111, a video extraction unit 112, a trigger acquisition unit 113, an average calculation unit 114, a delay time calculation unit 115, an extraction period specification unit 116, and a video extraction unit 117, as shown in Fig. 3. The main storage unit 102 shown in Fig. 2 also has a video buffer 121 that temporarily stores video data acquired from the network camera 2 in a FIFO (First In First Out) format, as shown in Fig. 3. The auxiliary storage unit 103 shown in Fig. 2 also has a video storage unit 131 that stores video data acquired from the network camera 2, and an extracted video storage unit 132 that stores video data obtained by extracting a part of the video data stored in the video storage unit 131, as shown in Fig. 3. The video storage unit 131 stores multiple image data constituting the video data extracted by the video extraction unit 112 from the video buffer 121, each of which is associated with time information indicating the time at which the video extraction unit 112 extracted the image data (hereinafter also referred to as extraction time information).

[0017] Extracted moving image storage unit 132 stores moving image data obtained by extracting, from the moving image data stored in moving image storage unit 131, a portion corresponding to a period before and after an event occurrence time point, which is the time point at which a preset event occurs in an object captured by network camera 2. The moving image data stored in extracted moving image storage unit 132 is used, for example, for analyzing the cause of a preset event when the event occurs in an object captured by network camera 2.

[0018] The video acquisition unit 111 acquires video data transmitted from the network camera 2 and stores it in the video buffer 121. The video acquisition unit 111 stores a plurality of image data constituting the acquired video data in chronological order in the video buffer 121. Here, the delay time from the time when the network camera 2 captures an image of an object to the time when the video acquisition unit 111 acquires the video data is approximately equal to the time required for the network camera 2 to transmit one frame of image data to the recording device 1, and is sufficiently small enough to be negligible compared to the delay time from the time when the video acquisition unit 111 acquires the video data to the time when the video extraction unit 112 extracts the video data from the video buffer 121, which will be described later. Therefore, the time when the video acquisition unit 111 acquires the image data captured at the time of event occurrence can be considered to be approximately equal to the time of the aforementioned event occurrence.

[0019] The video extracting unit 112 extracts any image data constituting the video data stored in the video buffer 121 from the video buffer 121 at a time (second time point) that is a delay time due to passing through the video buffer 121 from the time (first time point) acquired by the video acquiring unit 111, and stores the image data in the video storage unit 131. As shown in Fig. 4, for example, the video extracting unit 112 extracts image data PI(T0) acquired from the network camera 2 at the first time point T0 from the video buffer at the second time point T1 and stores the image data in the video storage unit 131. As a result, the video storage unit 131 stores the image data PI(T0) in association with the second time point T1.

[0020] Returning to FIG. 3, when the trigger acquisition unit 113 receives an abnormality detection signal via the abnormality detection I / F 107, that is, when it acquires trigger information indicating that the above-mentioned event has occurred in the image capture target of the network camera 2, the trigger acquisition unit 113 notifies the extraction period identification unit 116 and the average calculation unit 114 of event occurrence notification information notifying that the event has occurred.

[0021] The average calculation unit 114 calculates the average data amount of the video data stored in the video buffer 121. The average calculation unit 114 constantly monitors the data amount of the video data stored in the video buffer 121, and when it acquires the event occurrence notification information from the trigger acquisition unit 113, it calculates the average data amount of the data amount stored in the video buffer 121 at each time point within a preset average calculation target period immediately before acquiring the event occurrence notification information. Here, the length of the average calculation target period is set to, for example, several seconds to several minutes. In this way, the average calculation unit 114 can calculate the smoothed data amount based on the average calculation target period. The calculation of the average data amount is useful when the buffered data amount varies due to fluctuations in the video data transmitted from the network camera 2 caused by going through the network (for example, a decrease in the data amount due to a lack of bandwidth, etc.). The average calculation unit 114 notifies the delay time calculation unit 115 of average data amount information indicating the calculated average data amount. In this embodiment, the average amount of data stored in video buffer 121 at each point in time within a preset average calculation period is calculated. However, for example, average calculation unit 114 may calculate the amount of data stored in video buffer 121 at that point in time upon receiving event occurrence notification information from trigger acquisition unit 113.

[0022] The delay time calculation unit 115 calculates the delay time from the first time point at the second time point, that is, the average delay time which is the average of the delay times at the time point when the video extracting unit 112 extracts the video data from the time point when the event occurs, based on the average data amount indicated by the average data amount information notified by the average calculation unit 114 and the bit rate when the video data is transmitted from the network camera 2 to the recording device 1. Specifically, the delay time calculation unit 115 calculates the average delay time by dividing the average data amount by the bit rate. For example, when the average data amount is 6 to 9 Mbits and the bit rate is 3 Mbps, the average delay time calculated by the delay time calculation unit 115 is 2 to 3 sec. The delay time calculation unit 115 notifies the extraction period specification unit 116 of the average delay time information indicating the calculated average delay time.

[0023] When an event occurs in an image capturing target of the network camera 2, the extraction period specifying unit 116 specifies a period including a time when the delay time caused by passing through the video buffer 121 has elapsed from the time when the event occurred as an extraction period for extracting a part of the video data stored in the video storage unit 131. Specifically, when an event occurs in an image capturing target of the network camera 2, the extraction period specifying unit 116 specifies a period including a time when the average delay time has elapsed from the time when the event occurred as an extraction period for extracting a part of the video data stored in the video storage unit 131. When an event occurs in an image capturing target of the network camera 2 and the trigger acquisition unit 113 notifies the extraction period specifying unit 116 of event occurrence notification information, the extraction period specifying unit 116 specifies a period including a time when the average delay time dT1 indicated by the average delay time information notified by the delay time calculation unit 115 has elapsed from the time when the event occurrence notification information was notified as an extraction period. Here, the extraction period is set as a period between a point (Tt-dT2) a preset fixed time dT2 before a point (Tt+dT1) which is the above-mentioned average delay time dT1 from the event occurrence point Tt and a point (Tt+dT2) the above-mentioned fixed time dT2 after the point, as shown in Fig. 4, for example. This fixed time dT2 can be preset by the user of the recording device 1 according to the purpose of video recording, and is set to, for example, 30 seconds. The extraction period specification unit 116 notifies the video extraction unit 117 of extraction period information indicating the specified extraction period.

[0024] Returning to FIG. 3, the video extraction unit 117 extracts a part of the video data corresponding to the extraction period indicated by the extraction period information notified from the extraction period specification unit 116 from the video data stored in the video storage unit 131. Specifically, the video extraction unit 117 refers to time information associated with each of the multiple image data constituting the video data stored in the video storage unit 131, and extracts image data whose time indicated by the above-mentioned time information is included in the extraction period indicated by the above-mentioned extraction period information from the multiple image data. For example, as shown in FIG. 4, the video extraction unit 117 extracts video data corresponding to a time before and after including a time (Tt+dT1) that is the time when the average delay time dT1 has elapsed from the event occurrence time Tt, that is, a time period between (Tt+dT1-dT2) and (Tt+dT1+dT2) from the video data stored in the video storage unit 131. Then, the video extraction unit 117 stores the extracted part of the video data in the extracted video storage unit 132. 4, the video extraction unit 117 extracts video data corresponding to a period between a time point (Tt+dT1-dT2) a preset fixed time dT2 earlier than the event occurrence time Tt and a time point (Tt+dT1+dT2) a fixed time dT2 later than the event occurrence time Tt, including the time point (Tt+dT1) when the average delay time dT1 has elapsed, and stores the extracted video data in the extracted video storage unit 132. As a result, video data captured by the network camera 2 during the period from a time point (Tt-dT2) a fixed time dT2 earlier than the event occurrence time Tt to a time point (Tt+dT2) a fixed time dT2 later than the event occurrence time Tt can be stored in the extracted video storage unit 132.

[0025] Next, the recording process executed by the recording device 1 according to the present embodiment will be described in detail with reference to FIG. 5. This recording process is started, for example, when the recording device 1 is powered on. Here, in parallel with this recording process, the video acquisition unit 111 acquires video data transmitted from the network camera 2 and stores it in the video buffer 121, and the video extraction unit 112 extracts image data constituting the video data from the video buffer 121 and stores it in the video storage unit 131 in association with the extraction time information. First, the trigger acquisition unit 113 determines whether or not trigger information has been acquired (step S101). Here, as long as the trigger acquisition unit 113 determines that the trigger information has not been acquired (step S101: No), the process of step S101 is repeatedly executed. On the other hand, when the trigger acquisition unit 113 determines that the trigger information has been acquired (step S101: Yes), the average calculation unit 114 calculates the average data amount in the average calculation target period immediately before the video data stored in the video buffer 121 (step S102). Next, the delay time calculation unit 115 calculates an average delay time, which is the average of the delay times from the time an event occurs in the subject to the time when the video extraction unit 112 extracts the video data, based on the average data amount calculated by the average calculation unit 114 and the bit rate when the video data is transmitted from the network camera 2 to the recording device 1 (step S103).

[0026] Next, the extraction period specifying unit 116 specifies a predetermined period including the time when the calculated average delay time has elapsed from the time when the event occurred as an extraction period for extracting a part of the video data stored in the video storage unit 131 (step S104). After that, the video extraction unit 117 extracts a part of the video data corresponding to the extraction period specified by the extraction period specifying unit 116 from the video data stored in the video storage unit 131, and stores the extracted part of the video data in the extracted video storage unit 132 (step S105). Next, the process of step S101 is executed again.

[0027] Now, suppose that the video extraction unit 117, for example as shown in FIG. 6, refers to time information corresponding to each of the multiple image data constituting the video data stored in the video storage unit 131 and simply extracts a portion of the video data corresponding to the period between a time point (Tt-dT2) before and after the event occurrence time point Tt and a time point (Tt+dT2). In this case, the extracted portion of the video data is video data captured by the network camera 2 during the period between a time point (Tt-dT1-dT2) that is a certain time dT1+dT2 before the event occurrence time point Tt and a time point (Tt-dT1+dT2) that is a certain time dT2-dT1 after the event occurrence time point Tt, and the extracted portion of the video data is stored in the extracted video storage unit 132. That is, the length of time corresponding to the video data extracted before and after the event occurrence time point Tt is different. In particular, if the delay time dT1 is longer than the certain time dT2 set by the user, the image data at the event occurrence time point Tt cannot be extracted.

[0028] In contrast, according to the imaging system of the present embodiment, the extraction period specifying unit 116 specifies a period including a time point (Tt+dT1) when the average delay time dT1 determined based on the above-mentioned delay time has elapsed from the event occurrence time point Tt as an extraction period for extracting a part of the video data stored in the video storage unit 131. This makes it possible to specify the extraction period based on the above-mentioned delay time so that at least the event occurrence time point Tt is included in the extraction period, and therefore it is possible to appropriately record the video data before and after the event occurrence time point.

[0029] (Embodiment 2) The imaging system of this embodiment differs from embodiment 1 in that the recording device 1 has a sequence number extraction unit that extracts sequence number information indicating a sequence number assigned to a packet containing image data at the time an event occurs, which constitutes part of the video data, and calculates the aforementioned delay time based on the sequence number.

[0030] The hardware configuration and the functional configuration of the imaging system according to the present embodiment are the same as those of the imaging system according to the first embodiment. Therefore, the hardware configuration of the imaging system according to the present embodiment will be described using the reference numerals shown in FIG. 2 as appropriate. As shown in FIG. 7, the CPU 101 of the recording device 2001 according to the present embodiment loads a program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as a moving image acquisition unit 2111, a moving image extraction unit 2112, a trigger acquisition unit 113, a delay time calculation unit 2115, an extraction period specification unit 116, a moving image extraction unit 117, and a sequence number extraction unit 2118. Note that in FIG. 7, the same components as those in the first embodiment are denoted by the same reference numerals as those in FIG. 3. In addition, the main storage unit 102 of the recording device 2001 has a moving image buffer 2121 that temporarily stores moving image data acquired from the network camera 2 in association with a sequence number assigned to a packet including image data constituting the moving image data transmitted from the network camera 2. Furthermore, the auxiliary storage unit 103 of the recording device 2001 includes a moving image storage unit 131 and an extracted moving image storage unit 132 .

[0031] The video acquisition unit 2111 stores image data at the time of the event occurrence, which constitutes part of the video data transmitted from the network camera 2, in the video buffer 2121 in association with the sequence number assigned to the packet containing the image data. Here, the packet containing the image data transmitted from the network camera 2 and acquired by the video acquisition unit 2111 conforms to the above-mentioned RTP and contains RTP header information as shown in FIG. 8. Here, "V" indicates the version number of RTP, and is set to "2", for example. "P" indicates whether the payload portion corresponding to the RTP header of the packet is padded or not, and is set to "1" if it is padded, and is set to "0" if it is not padded. "X" indicates whether an extension header is added or not, and is set to "1" if an extension header is added, and is set to "0" if an extension header is not added. "CC" indicates the length of a list of information indicating multiple media streams contained in the packet when the payload portion corresponding to the RTP header of the packet is a composite of multiple media streams. "M" indicates an event defined in RTP, such as start, restart, or end of a media stream. "PT" is information for identifying the media type of data stored in the payload corresponding to the RTP header. The sequence number is expressed as an unsigned 16-bit integer value that is incremented by one each time a packet is transmitted from the network camera 2. The timestamp indicates the time when the image data contained in the packet was generated. This is approximately equal to the time when the image was captured. When the video acquisition unit 2111 acquires a packet containing image data transmitted from the network camera 2, it extracts the image data from the acquired packet, and stores the extracted image data in the video buffer 2121 in association with sequence number information indicating the sequence number included in the RTP header of the acquired packet. Note that, although the sequence number described in the RTP header is used here for the explanation, it is sufficient that the image data and the sequence number are associated in the packet transmitted from the network camera, and is not limited to RTP.

[0032] Returning to FIG. 7, when the trigger acquisition unit 113 acquires trigger information indicating that the aforementioned event has occurred in the object being imaged by the network camera 2, the trigger acquisition unit 113 notifies the extraction period determination unit 116, the delay time calculation unit 2115, and the sequence number extraction unit 2118 of event occurrence notification information notifying that the event has occurred.

[0033] When the sequence number extraction unit 2118 is notified of the event occurrence notification information from the trigger acquisition unit 113, it extracts sequence number information indicating a sequence number assigned to a packet including image data at the time of the event occurrence that constitutes a part of the video data. Specifically, when the sequence number extraction unit 2118 is notified of the event occurrence notification information from the trigger acquisition unit 113, it extracts sequence number information indicating a sequence number included in the RTP header of the packet acquired by the video acquisition unit 2111 from the network camera 2. Since the delay at the time when the video acquisition unit 2111 receives the data can be almost ignored, the image data loaded into the packet with this sequence number is almost equal to the image captured at the time the event occurred. The sequence number extraction unit 2118 notifies the video extraction unit 2112 of the extracted sequence number information.

[0034] Similar to video extracting unit 112 according to the first embodiment, video extracting unit 2112 extracts image data constituting the video data stored in video buffer 2121 from video buffer 2121 and stores it in video storage unit 131. At this time, the time at which the video data is extracted from video buffer 2121 is delayed by the delay time caused by passing through video buffer 2121. Then, when video extracting unit 2112 extracts from video buffer 2121 the image data associated with the sequence number information notified by sequence number extraction unit 2118, video extracting unit 2112 notifies delay time calculation unit 2115 of event occurrence time point image extraction notification information notifying that the image data at the time point of the event has been extracted.

[0035] The delay time calculation unit 2115 specifies the extraction time when the video extracting unit 2112 extracts the image data at the time point of the event from the video buffer 2121 based on the sequence number, and calculates the time difference between the specified extraction time and the time point of the event as the delay time. Specifically, the delay time calculation unit 2115 specifies the time when the video extracting unit 2112 notifies the event occurrence time point image extraction notification information as the extraction time. Then, the delay time calculation unit 2115 notifies the extraction period determination unit 116 of delay time information indicating the calculated delay time. When the trigger acquisition unit 113 notifies the extraction period determination unit 116 of the event occurrence notification information, the extraction period determination unit 116 specifies a period including a time when the delay time indicated by the delay time information notified by the delay time calculation unit 2115 has elapsed from the time when the event occurrence notification information was notified, as the extraction period.

[0036] Next, the recording process executed by the recording device 2001 according to this embodiment will be described in detail with reference to Fig. 9. In parallel with this recording process, the video acquisition unit 2111 acquires video data transmitted from the network camera 2 and stores the data in the video buffer 121 in association with sequence number information, and the video extraction unit 2112 extracts image data constituting the video data from the video buffer 121 and stores the image data in the video storage unit 131 in association with extraction time information. First, the trigger acquisition unit 113 determines whether or not trigger information has been acquired (step S201). Here, as long as the trigger acquisition unit 113 determines that trigger information has not been acquired (step S201: No), the process of step S201 is repeatedly executed. On the other hand, when the trigger acquisition unit 113 determines that it has acquired trigger information (step S201: Yes), the sequence number extraction unit 2118 extracts sequence number information indicating the sequence number assigned to the packet from the RTP header information of the packet containing image data at the time of the event occurrence that constitutes part of the video data (step S202).

[0037] Next, the delay time calculation unit 2115 identifies the extraction time when the video extraction unit 2112 extracted the image data at the time of the event occurrence from the video buffer 2121 based on the sequence number information extracted by the sequence number extraction unit 2118 (step S203). Then, the delay time calculation unit 2115 calculates the time difference between the identified extraction time and the time of the event occurrence as the delay time (step S204). More specifically, the delay time calculation unit 2115 calculates the time difference between the timestamp included in the packet at the identified extraction time and the timestamp included in the packet at the time of the event occurrence based on the sequence number information. Thereafter, the extraction period identification unit 116 identifies a period including the time when the calculated delay time has elapsed from the aforementioned time of the event occurrence as an extraction period for extracting a part of the video data stored in the video storage unit 131 (step S205). Next, the moving image extraction unit 117 extracts a portion of the moving image data corresponding to the extraction period identified by the extraction period identification unit 116 from the moving image data stored in the moving image storage unit 131, and stores the extracted portion of the moving image data in the extracted moving image storage unit 132 (step S206). Then, the process of step S201 is executed again.

[0038] As described above, according to the imaging system of this embodiment, the sequence number extraction unit 2118 extracts sequence number information indicating a sequence number assigned to a packet including image data at the time of event occurrence. The delay time calculation unit 2115 identifies the extraction time when the image data at the time of event occurrence was extracted from the video buffer 2121 by the video extraction unit 2112 based on the sequence number information, and calculates the time difference between the identified extraction time and the time of event occurrence as the delay time. The extraction period identification unit 116 then identifies a period including the time when the calculated delay time has elapsed from the time of event occurrence as the extraction period. This makes it possible to more accurately calculate the delay time corresponding to the image data at the time of event occurrence, and therefore makes it possible to appropriately identify the extraction period.

[0039] (Embodiment 3) The imaging system of this embodiment differs from embodiment 1 in that the recording device 1 has a time information extraction unit that extracts time information (timestamp) indicating the time when the event occurred that is contained in a packet containing image data at the time when the event occurred, and identifies the above-mentioned extraction period based on the extracted time information.

[0040] The hardware configuration and the functional configuration of the imaging system according to the present embodiment are the same as those of the imaging system according to the first embodiment. Therefore, the hardware configuration of the imaging system according to the present embodiment will be described using the reference numerals shown in FIG. 2 as appropriate. As shown in FIG. 10, the CPU 101 of the recording device 3001 according to the present embodiment loads a program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as a moving image acquisition unit 3111, a moving image extraction unit 3112, a trigger acquisition unit 113, an extraction period specification unit 3116, a moving image extraction unit 117, and a time information extraction unit 3118. Note that in FIG. 10, the same components as those in the first embodiment are given the same reference numerals as those in FIG. 3. Furthermore, the main storage unit 102 of the recording device 3001 has a moving image buffer 3121 that temporarily stores moving image data acquired from the network camera 2 in association with time information indicating the time when the image data constituting the moving image data transmitted from the network camera 2 was generated. Furthermore, the auxiliary storage unit 103 of the recording device 3001 has a moving image storage unit 3131 and an extracted moving image storage unit 132. The moving image storage unit 3131 stores a plurality of image data constituting the moving image data extracted from the moving image buffer 3121 by the moving image extracting unit 3112, in association with time information indicating the time when the image data was generated.

[0041] The video acquisition unit 3111 stores image data at the time of event occurrence, which constitutes part of the video data transmitted from the network camera 2, in the video buffer 3121 in association with time information indicating the time when the image data was generated. When the video acquisition unit 3111 acquires a packet including image data, it extracts the image data and generates time information indicating the time when the image data was generated by referring to the above-mentioned timestamp included in the RTP header of the packet. The video acquisition unit 3111 then stores the extracted image data and the generated time information in the video buffer 3121 in association with each other.

[0042] When the trigger acquisition unit 113 acquires trigger information indicating that the above-mentioned event has occurred in the subject imaged by the network camera 2, the trigger acquisition unit 113 notifies the time information extraction unit 3118 of event occurrence notification information notifying that the event has occurred.

[0043] When the time information extraction unit 3118 is notified of the event occurrence notification information from the trigger acquisition unit 113, it extracts time information indicating the time point when image data at the time point of the event occurrence that constitutes part of the video data was generated. Specifically, when the time information extraction unit 3118 is notified of the event occurrence notification information from the trigger acquisition unit 113, it extracts time stamp information indicating the time stamp included in the RTP header of the packet acquired by the video acquisition unit 2111 from the network camera 2, that is, time information. The time information extraction unit 3118 notifies the extraction period identification unit 3116 of the extracted time information.

[0044] The video extractor 3112 extracts from the video buffer 3121 the image data constituting the video data stored in the video buffer 3121 and the time information corresponding to the image data, and stores these in the video storage 3131 in association with each other.

[0045] The extraction period determination unit 3116 determines a predetermined period including the event occurrence time point as an extraction period from which to extract a portion of the video data stored in the video storage unit 3131, based on time information indicating the event occurrence time point notified by the time information extraction unit 3118. The extraction period determination unit 3116 notifies the video extraction unit 117 of extraction period information indicating the determined extraction period. The video extraction unit 117 refers to time information corresponding to the image data constituting the video data stored in the video storage unit 3131, and extracts a portion of the video data where the time point indicated by the time information is included in the period indicated by the extraction period information notified by the extraction period determination unit 3116.

[0046] Next, the recording process executed by the recording device 3001 according to this embodiment will be described in detail with reference to Fig. 11. In parallel with this recording process, the video acquisition unit 3111 acquires video data transmitted from the network camera 2, associates it with time information and stores it in the video buffer 3121, and the video extraction unit 3112 extracts image data constituting the video data from the video buffer 121 and the corresponding time information, associates it with each other and stores it in the video storage unit 3131. First, the trigger acquisition unit 113 determines whether or not trigger information has been acquired (step S301). Here, as long as the trigger acquisition unit 113 determines that trigger information has not been acquired (step S301: No), the process of step S301 is repeatedly executed. On the other hand, when the trigger acquisition unit 113 determines that it has acquired trigger information (step S301: Yes), the time information extraction unit 3118 extracts time information indicating the time when the image data was generated from the RTP header information of a packet containing image data at the time of the event occurrence that constitutes part of the video data (step S302).

[0047] Next, the extraction period determination unit 3116 determines a period including the time point when the image data at the time point of the event occurrence indicated by the time information extracted by the time information extraction unit 3118 was generated as an extraction period from which to extract a portion of the video data stored in the video storage unit 3131 (step S303). Next, the video extraction unit 117 extracts a portion of the video data corresponding to the extraction period determined by the extraction period determination unit 3116 from the video data stored in the video storage unit 3131, and stores the extracted portion of the video data in the extracted video storage unit 132 (step S304). Then, the process of step S301 is executed again.

[0048] As described above, according to the imaging system of this embodiment, the time information extraction unit 3118 extracts time information indicating the time when the image data at the time when an event occurred, which is included in a packet including image data at the time when an event constituting part of the video data occurred, was generated. Then, the extraction period determination unit 3116 determines, as the extraction period, the period including the time when the image data at the time when the event occurred, which is indicated by the time information extracted by the time information extraction unit 3118, was generated. This allows the time when the image data at the time when the event occurred to be accurately determined, and therefore allows the extraction period to be appropriately determined.

[0049] Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations of the above-mentioned embodiments. For example, the extraction period determination unit may determine, when an event occurs in an object captured by the network camera 2, a period including a time point that is a preset fixed delay time after the event occurrence as the extraction period.

[0050] The hardware configuration and the functional configuration of the imaging system according to this modification are the same as those of the imaging system according to the first embodiment. In the imaging system according to this modification, as shown in FIG. 12, the CPU 101 of the recording device 4001 loads a program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as the video acquisition unit 111, the video extraction unit 112, the trigger acquisition unit 113, the extraction period specification unit 4116, and the video extraction unit 117. Note that in FIG. 12, the same components as those in the first embodiment are given the same reference numerals as those in FIG. 3. The auxiliary storage unit 103 of the recording device 3001 has a video storage unit 131, an extracted video storage unit 132, and a delay time storage unit 4133. The delay time storage unit 4133 stores delay time information indicating a predetermined certain delay time as a delay time caused by passing through the video buffer 121 based on past experience, for example, the delay time from the first time point to the second time point described in the first embodiment.

[0051] When an event occurs in the object being imaged by the network camera 2, the extraction period determination unit 4116 determines a period including a point in time from the time the event occurred that is a certain delay time indicated by the delay time information stored in the delay time memory unit 4133, as an extraction period from which to extract a portion of the video data stored in the video memory unit 131.

[0052] According to this configuration, the processing executed by the recording device 4001 is simplified, and the processing load on the recording device 4001 can be reduced accordingly.

[0053] As another method for determining the delay time, a flag may be added to the video data obtained from the network camera 2 when trigger information is received, and the delay time may be determined from the difference between the time when this flagged video data is retrieved from the video buffer 121 and the time when the trigger information is received.

[0054] In each embodiment, an example has been described in which the video transmission unit 211 transmits the video data stored in the captured image buffer 221 to the recording device 1 by RTP, but the protocol used for transmitting the video data is not limited to this. For example, the video transmission unit 211 may transmit the video data stored in the captured image buffer 211 to the recording device 1 by HLS (HTTP Live Streaming), which is a streaming protocol that is a technology for distributing video on the Internet.

[0055] The various functions of the recording devices 1, 2001, 3001, and 4001 according to the present invention can be realized by using a computer system equipped with a wireless communication module, without using a dedicated system. For example, a program for executing the above operations may be stored in a non-transitory recording medium (such as a CD-ROM) that can be read by the computer system and distributed to a computer connected to a network, and the recording devices 1, 2001, 3001, and 4001 that execute the above-mentioned processes may be configured by installing the program in the computer system.

[0056] The method of providing the program to the computer is arbitrary. For example, the program may be uploaded to a server on a communication line and distributed to the computer via the communication line. The computer then starts up the program and executes it under the control of the OS in the same way as other applications. In this way, the computer functions as the recording device 1, 2001, 3001, 4001 that executes the above-mentioned processes.

[0057] Although the embodiment and the modified examples of the present invention have been described above, the present invention is not limited to these. The present invention includes appropriate combinations of the embodiment and the modified examples, and appropriate modifications thereto. [Industrial Applicability]

[0058] The present invention is suitable as an imaging system that performs event-driven recording using a network camera. [Explanation of symbols]

[0059] 1, 2001, 3001, 4001: Recording device, 2: Network camera, 101, 201: CPU, 102, 202: Main memory unit, 103, 203: Auxiliary memory unit, 106, 206: Wired communication interface, 108: Timekeeping unit, 109, 209: Bus, 111, 2111, 3111: Video acquisition unit, 112, 2112, 3112: Video extraction unit, 113: Trigger acquisition unit, 114: Average value calculation unit, 11 5, 2115: delay time calculation unit, 116, 3116, 4116: extraction period determination unit, 117: video extraction unit, 121, 2121, 3121: video buffer, 131, 3131: video storage unit, 132: extracted video storage unit, 204: imaging unit, 211: video transmission unit, 221: captured image buffer, 2118: sequence number extraction unit, 3118: time information extraction unit, 4133: delay time storage unit, NW: network

Claims

1. An imaging device; a recording device connected to the imaging device via a network, The recording device is a video buffer for temporarily storing video data; a video acquisition unit that acquires the video image data transmitted from the imaging device and stores the video image data in the video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; a video fetching unit fetching image data constituting the video data stored in the video buffer from the video buffer, and storing the image data in the video storage unit in association with fetching time information indicating a time point at which the image data was fetched; a delay time calculation unit that calculates a delay time caused by passing through the video buffer; an extraction period determination unit that, when a preset event occurs in an object to be imaged by the imaging device, determines, with respect to the retrieval time information, a period around a preset fixed time centered on a point in time when the event occurs and the delay time calculated by the delay time calculation unit has elapsed, as an extraction period for extracting a portion of the moving image data stored in the moving image storage unit; a moving image extracting unit that extracts a portion of the moving image data corresponding to the extraction period from the moving image data stored in the moving image storage unit, Imaging system.

2. The recording device is an average calculation unit that calculates an average data amount of the video data stored in the video buffer, The delay time calculation unit calculates an average delay time, which is an average of the delay times, based on the average data amount and a bit rate at the time of transmitting the video data from the imaging device to the recording device. The imaging system according to claim 1 .

3. the imaging device transmits the moving image data to the recording device using a protocol used for transmitting the moving image data; The recording device is a sequence number extraction unit that extracts sequence number information indicating a sequence number assigned to a packet including the image data at the time point when the event occurs, the sequence number information indicating a sequence number assigned to a packet including the image data at the time point when the event occurs, the sequence number extracting unit extracting ... the video acquisition unit stores the image data at the time point when the event occurs in the video buffer in association with the sequence number information corresponding to a packet including the image data; the delay time calculation unit specifies, based on the sequence number information, fetch time information indicating a time when the image data at the time point when the event occurs was fetched from the video buffer by the video fetch unit, and calculates, as the delay time, a time difference between the specified fetch time information and the time point when the event occurs. The imaging system according to claim 1 .

4. The delay time calculation unit sets a predetermined time as the delay time. The imaging system according to claim 1 .

5. An imaging device; a recording device connected to the imaging device via a network, the imaging device transmits moving image data of an object to the recording device according to a protocol used for transmitting moving image data; The recording device is a video buffer for temporarily storing video data; a video acquisition unit that acquires the video data and stores it in a video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; a video extracting unit that extracts image data constituting the video data stored in the video buffer from the video buffer and stores the image data in the video storage unit; a timestamp extracting unit that, when a preset event occurs in an object to be imaged by the imaging device, extracts a timestamp indicating a time when image data at the time point of the event occurrence was generated, the timestamp being included in a packet including image data at the time point of the event occurrence, the packet constituting a part of the video data; an extraction period determination unit that determines a period around the event occurrence time point indicated by the time stamp by a preset certain time as an extraction period for extracting a part of the video data stored in the video storage unit; a moving image extracting unit that extracts a portion of the moving image data corresponding to the extraction period from the moving image data stored in the moving image storage unit, Imaging system.

6. The recording device is A trigger acquisition unit that acquires trigger information indicating that the event has occurred. The imaging system according to claim 1 .

7. A recording device connected to an imaging device via a network, a video buffer for temporarily storing video data; a video acquisition unit that acquires the video image data transmitted from the imaging device and stores the video image data in the video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; a video fetching unit fetching image data constituting the video data stored in the video buffer from the video buffer, and storing the image data in the video storage unit in association with fetching time information indicating a time point at which the image data was fetched; a delay time calculation unit that calculates a delay time caused by passing through the video buffer; an extraction period determination unit that, when a preset event occurs in an object to be imaged by the imaging device, determines, with respect to the retrieval time information, a period around a preset fixed time centered on a point in time when the event occurs and the delay time calculated by the delay time calculation unit has elapsed, as an extraction period for extracting a part of the moving image data stored in the moving image storage unit; a moving image extracting unit that extracts a portion of the moving image data corresponding to the extraction period from the moving image data stored in the moving image storage unit, Recording device.

8. A method for recording moving image data received from an imaging device via a network, comprising: acquiring video data transmitted from the imaging device and storing the video data in a video buffer that temporarily stores the video data; fetching image data constituting the moving image data stored in the moving image buffer from the moving image buffer, and storing the image data in a moving image storage unit that stores the moving image data obtained from the imaging device in association with fetching time information indicating a time point when the image data was fetched; a delay time calculation step of calculating a delay time caused by passing through the video buffer; a step of, when a preset event occurs in an object to be imaged by the imaging device, specifying, with respect to the extraction time information, a period around a preset fixed time centered on a point in time when the delay time calculated by the delay time calculation step has elapsed from a time point when the event occurred, as an extraction period for extracting a part of the moving image data stored in the moving image storage unit; extracting a portion of the video data corresponding to the extraction period from the video data stored in the video storage unit. How to record.

9. Computer, a video buffer for temporarily storing video data; a video acquisition unit that acquires video image data transmitted from an imaging device and stores the video data in the video buffer; a moving image storage unit that stores the moving image data acquired from the imaging device; a video fetching unit fetching image data constituting the video data stored in the video buffer from the video buffer, and storing the image data in the video storage unit in association with fetching time information indicating a time point at which the image data was fetched; a delay time calculation unit that calculates a delay time caused by passing through the video buffer; an extraction period specifying unit that, when a preset event occurs in an object to be imaged by the imaging device, specifies, with respect to the retrieval time information, a period around a preset fixed time centered on a point in time when the event occurs and the delay time calculated by the delay time calculating unit has elapsed, as an extraction period for extracting a part of the moving image data stored in the moving image storage unit; a moving image extracting unit that extracts a portion of the moving image data corresponding to the extraction period from the moving image data stored in the moving image storage unit; A program to function as a

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