FR2799563A1 - METHOD AND DEVICE FOR DETECTING THE APPEARANCE OF AN EVENT OR PRESENCE - Google Patents

Abstract

The invention concerns a method for detecting the occurrence of an event or a presence on a monitored site which consists in: receiving (12) digital images of the site or video images of the site converted into digital images; determining (14) the number of octets (Ni) contained in the current digital image received; comparing (16) the number of octets (Ni) contained in the current digital image received with the number of octets (Nref) contained in a previously stored reference digital image, so as to obtain a variate value of the number of octets ( DELTA Ni); from a table of reference of variate values of the number of octets ( DELTA Nref), determining whether the variate value obtained ( DELTA Ni) is representative of the occurrence of an event or of a presence, and if such is the case, storing (24) the current digital image received and transmitting it to a watch terminal.

Description

The present invention relates to a method and a device for detecting the occurrence of an event or a presence. More specifically, the invention relates to a method and a device for detecting event a presence in an image corresponding to a sensed optical scene.

The invention is described here more particularly in its application to the surveillance of sites (enclosed or not), either for private use, or for professional use, or for public use (town hall, museum, parking, etc.). However, more generally, the invention can be applied to other domains, such as home automation, and used for any data entry, analysis or design technique (possibly organic or quantum) requiring the detection of an event or a presence in an image.

Surveillance systems are known, including cameras located on the site to be monitored, and screens located in a monitoring center, receiving images captured by the cameras.

such an organization is burdensome and expensive because it generally requires the presence of personnel to constantly monitor the screens the whereabouts of authorized persons, and detect the presence of intruders or the occurrence of abnormal events.

Other systems of the prior art use video technology to analyze the lines of the image and their variation to determine a motion in the image, or to analyze the points constituting the images. WO 97/20293 discloses a method and a device for generating a visual record extending over a determined period of time.

However, noise related to image transmission conditions and lighting variations often distorts the analysis results.

In addition, the known systems generally do not allow to select the type of volume which one seeks to detect presence. This creates a sometimes significant uncertainty as to the nature of the event that gave rise to detection.

Moreover, the known systems generally do not allow to select with certainty the type of movement and / or event to be taken into account.

The present invention aims to overcome the aforementioned drawbacks, the comparative analysis of the amount, in bytes, of image files corresponding to the optical scenes captured.

On the one hand, the invention makes automatic the detection of the presence of an intruder from the appearance of an incident, from images captured by cameras, which eliminates the need for the constant and systematic presence of personnel in a monitoring center.

On the other hand, the invention makes it possible to take into account information on the type of volume, of movement, of the event to be detected. For this purpose, the present invention proposes a method for detecting the occurrence of an event or presence on a site under surveillance, according to which digital images of this site or video images of this site converted into images are captured. digital, characterized in that (a) a determination step is performed in which the number of bytes contained in the current sensed digital image is determined; a comparison step is performed in which the number of bytes contained in the current captured digital image is compared with the number of bytes contained in a reference digital image stored previously, so as to obtain a number variation value bytes; (c) performs a detection step, in which, from a table of reference values of changes in the number of bytes, determines whether the obtained variation value is representative of the occurrence of an event or of a presence on the site; and, if the obtained variation value is representative of the occurrence of an event or a presence on the site, (d) performs a storage and transmission step, during which the current captured digital image is stored and is transmitted to a monitoring terminal.

Thus, by a simple comparative analysis of the amount of bytes of the images captured successively, the invention makes it possible to automatically detect a presence (intruder or other) (person, animal, object) or occurrence of an event (incident or other) on the site under surveillance, and report such presence or event to a monitoring terminal with a view to preparing a possible intervention on the site.

In addition, the comparison of the number of bytes is an easy operation to implement and inexpensive in computing time.

In addition, the selective transmission to the monitoring terminal only suspicious images allows significant savings in the volume of information to be transmitted, compared to the prior art.

According to a particular characteristic, the reference digital image may be the digital image captured preceding the current digital image, if the value of variation of the number of bytes obtained from this preceding digital image is not representative. the appearance of an event or a presence.

This feature makes monitoring and detecting suspicious events more efficient by refreshing the reference image. According to a particular characteristic, the reference values table can be established by calibration of the site to be monitored, before being placed under surveillance.

There is thus real information measured to distinguish between variations in the number of usual bytes, not to give rise to detection, and variations in the number of bytes listed as being representative of an intrusion or a disaster, for example fire type.

According to a particular characteristic, when a variation value representative of the occurrence of an event or a presence, it is possible to trigger an audible alarm on the site and / or to the monitoring terminal.

This means makes it possible, on the one hand, to clearly signal the event to the monitoring terminal and on the other hand, at the site level, an element of intimidation for the possible intruder, and a piece of information intended for service providers. emergency (fire, police, ...) in case of disaster.

According to a particular characteristic, after transmission to the monitoring terminal of a digital image, it is possible to confirm visual assessment that an incident has actually occurred, that an intruder actually present, or that any other event or presence considered as suspect has actually been detected.

This allows the staff in charge of the monitoring terminal to verify that the event detected by image processing is indeed suspect, which considerably limits the risk of an unnecessary intervention on the site because of false alarm, without requiring continuous monitoring of one or more screens by specific personnel.

According to a particular characteristic, if a variation value is representative of the occurrence of an event or a presence, it is possible to memorize, in addition to the current image, the instant at which this current image has been captured.

Indeed, the moment of the detection is likely to constitute a dated proof if necessary, for example with an insurance company with which the site would be insured, or during a possible police investigation following an offense.

Advantageously, the images for which a succession of steps (a) of determination, (b) comparison and (c) detection mentioned above are carried out can be picked up at regular intervals.

This contributes to the efficiency of the monitoring and it also makes it possible to follow the progressive evolution of the variations of the number of bytes, for example according to the natural growth or decay of the daylight on the site. By way of non-limiting example, it is possible to capture images of the site at a rate of between 1 and 24 images per second. However, depending on the nature of the site, you may consider capturing less than one frame per second or more than 24 frames per second. Thus, images are captured at a variable rate depending on the nature of the site.

For the same purpose as that indicated above, the present invention also proposes a device for detecting the occurrence of an event of a presence on a site under surveillance, characterized in that it comprises: digital images or means for capturing video images and converting these video images into digital images, arranged in at least one location of the site; calculating means, for determining the number of bytes contained in a digital image, connected to the input means; comparison means, for comparing the number of bytes contained in two digital images, the comparison means being connected to the calculation means and providing variation values of the number of bytes; a table of reference values of variations in the number of bytes; decision means, for determining, from the reference value table, whether the variation values of the number of bytes provided by the comparison means are representative of the appearance of an event of a presence on the site; - Image storage means; and transmitting means, for transmitting to a digital image monitoring terminal whose number of octets variation value is representative of the occurrence of an event or a presence.

According to a particular characteristic, the aforementioned device may further comprise at least one loudspeaker on the site and / or connected to the monitoring terminal to deliver an audible alarm when a variation value is representative of the appearance of an event or a presence.

According to a particular characteristic, the detection device may furthermore comprise means for storing image capture times, the transmission means being adapted to transmit these image acquisition times to the monitoring terminal.

The advantages of this detection device and of these particular characteristics being the same as those of the detection method as briefly described above, they are not recalled here.

The method and apparatus of the invention can operate from both color images and black-and-white images.

According to one particular characteristic, the image acquisition means comprise a plurality of CCD type cameras (in English <I> "Charge </ I> Coupled Device") color.

Such cameras allow good quality visual recognition.

Depending on the nature of the site to be monitored and / or in case of night surveillance, image capture means may include infrared image capture means, such as at least one conventional infrared camera.

According to a particular characteristic, the transmission means comprise modem operating only in transmission.

This feature, which prohibits the monitoring terminal from taking images of the site apart from those transmitted to it because they are suspect, makes it possible in particular to preserve the confidentiality of the operation of the company if the site under surveillance is for professional use, and allows in particular to respect the privacy of individuals if the site is for private use. The present invention further provides a computer of personal type, characterized in that it comprises a device as briefly outlined above.

Other aspects and advantages of the invention will appear on reading the following detailed description of particular embodiments given as non-limiting examples. The description refers to the accompanying drawings, in which - Figure 1 is a flowchart illustrating the sequence of steps of the method of the invention, in a particular embodiment; FIG. 2 is a flowchart illustrating the choice and the updating mode of the reference image, in a particular embodiment; - Figure 3 schematically shows the device of the invention in a particular embodiment; and FIG. 4 is a graph illustrating, by way of nonlimiting example, the evolution curve of the number of bytes as a function of time for a site lit by daylight.

As shown in FIG. 1, during a first step 10, which corresponds to an installation and commissioning phase, a counter (for example at the value i = 0), designed to designate each, is initialized. digital image processed, and we capture a first digital image of the site (reference image), which is memorized. Then the counter i is incremented by one unit (i = 1).

Advantageously, the captured images are not subjected to any compression. This allows for a maximum number of bytes to perform the image comparison step 16 described below.

In step 12, we capture a new digital image of the site, in this case, the index image i.

The next step 14 consists in determining the number of bytes Ni of which is constituted the current image index i captured.

In a particular embodiment, the number of bytes Ni can for example be obtained as follows: the aforementioned image acquisition means convert the captured image, which is for example in the form of video, analog or digital signal, in an image file, consisting of bytes. Furthermore, conventionally, each pixel (pixel) of the captured image is encoded by one or more of these bytes.

The number of Ni bytes may be different depending on the type of conversion used by the aforementioned image acquisition means.

In a particular embodiment, the aforementioned image acquisition means may comprise a digital camera. As a non-limitative example, we can use a camera of the type "Video Blaster Webcam II" ("Video Blaster": registered trademark) .This camera can provide captured images in the form of byte files having for example for extension " .mpg ".

Alternatively, the aforesaid image capturing means may comprise a conventional video camera and an acquisition card for converting video images provided by the conventional camera into digital images, i.e. in the form of bytes.

In step 16, comparing the number of bytes Ni of the current image number of bytes Nref of a reference image already stored; this is the first pass of the process, which will then be reiterated with images captured later; the reference image is here the first image captured during commissioning.

The above comparison consists in calculating the difference Ni - Nref between the two numbers of bytes. The result is an ONi value of variation of the number of bytes.

We seek to know if the value of variation aNi obtained is significant, that is to say if it is likely to correspond to the appearance of an event or a presence on the site.

For this, before commissioning, it proceeds, during a step 20, to a calibration of the site to be monitored, that is to say that captures images of the site in various specific situations of brightness, with and without moving people, animals and objects. Then a table of reference values of variations in the number of bytes ANref is established, based on the number of bytes recorded for each of these images and the variation in the number of bytes associated.

then stores the reference value table ANref for later reference.

As a non-limitative example, the reference values of changes in the number of bytes ANref stored during the calibration of the site make it possible to identify the following events: - variation of the lighting by increasing or gradually decreasing the daylight; - variation of lighting by sudden increase or decrease of daylight (opening or closing of shutters, doors, lighting or extinguishing of an electric lamp, etc.); - presence of an additional body on the site (for example, dog or cat); - presence of a moving or immobile human body, child or adult, on the site; presence of smoke or flames; brutal zeroing of the number of bytes of the current image, due to a technical incident (for example, destruction or camera failure, sectioning of a cable, etc.).

The list given above is not exhaustive.

Thus, we observe on the graph of the <B> figure 4 </ B> the evolution, during a period 24 hours, of the number of bytes, carried on the ordinate, as a function of the time, carries in abscissa, for a site lit only by daylight.

Two successive points of the curve are separated by 1 hour. number of bytes progressively increases from a maximum of about 1 221 bytes, which corresponds to the hours of greater brightness for example, to a minimum, 12 hours later, of about a few hundred bytes, corresponds to the hours nocturnal lights for this example. Variation values of the number of bytes are representative of a decrease or increase of the brightness. However, the values of the number of bytes carried on the curve are purely indicative <B>, </ B> they can vary very strongly (from a few bytes to values much higher than the figure of 1 221 200 given above), taking into account several parameters such as the nature of the site monitors (more or less volume of information), the average shooting sensitivity lux capture), or certain characteristics (memory capacity, capacity of treatment, etc.) of the various means implemented the detection device described below with the help of Figure 3.

In step 18, the variation value obtained from the current image is compared with the values contained in the reference value table.

If it turns out in step 22 that the variation value ANi is significant, the current image is stored (step 24) and transmitted to a monitoring terminal which monitors the site in question. It may be useful, as indicated above, on the one hand, also to memorize the moment at which the current image has been captured, for example in the form of a date in day, month, year, hours, minutes, seconds, and on the other hand, trigger an alarm, for example sound, on the site and / or to the terminal monitoring.

In step 28, the image received by the monitoring terminal is subject to the visual assessment of one or more persons, who verify that the suspect event has actually occurred and / or that the presence detected is indeed suspect and that it is necessary to intervene on the site.

Concomitantly, the counter i is incremented by one unit (step 26) and is waited for a time interval At (step 30) before capturing a new image. As a non-limiting example, At is between 1 second and 1 second, depending on whether we capture between 1 and 24 images per second. However, depending on the nature of the site, it is possible to choose a value of at greater than 1 second or less than 1124 seconds. This time interval can for example be adjusted so that fugitive events such as lightning, due to a thunderstorm or a flash of a camera are not taken into account. If, on the other hand, after consulting the table of reference values oNref, it appears that the variation value ANi relative to the current image is not significant, the steps 26 of incrementing the counter and 30 of waiting for a time interval At.

The method of the invention may be triggered by a conventional type of voice control, or by means of a secret code entered on a control keyboard, or by means of a conventional type key mechanism. These securing arrangements are intended to ensure that the flow of the process can only be stopped by an authorized person.

The reference image and its associated number of bytes Nref are updated as images are captured, as shown in Figure 2. As mentioned above, during step 10 of installation it is the first captured image that is taken as a reference image.

Then, during each step 22 of determining whether the variation of the number of bytes ANi associated with the current image is significant in view of the table of reference values ANref, two cases may occur: either the variation ANi is significant , and in this case, in step 260, the counter i is incremented by one unit without modifying the reference image; or the variation ANi is not significant, and in this case, the reference image is updated in step 32 by replacing it with the current image index i, before incrementing the counter i d one unit in step 260.

We now describe a particular embodiment of a detection device according to the present invention, using Figure 3.

The device comprises means 401, 402,..., 40 "for capturing digital images, These means can be realized in the form of several cameras judiciously arranged in several locations of the site to be monitored, so as to visualize them. As much as possible, the cameras are CCD-type digital color cameras and produce images of sufficient size to allow good visual recognition of events, for example of the order of 640 × 480 pixels. provide a set of six cameras, each capturing 4 frames per second, between which images of the site from different angles are analyzed cyclically in turn.

The cameras 402,..., 40, are connected to a set of processing means described below which can for example be collected in a personal computer (PC, in English "Personal Computer") comprising a processor type <I> "Pentium" </ I> (registered trademark) operating at a frequency of 233 equivalent, in order to benefit from a sufficient speed of execution necessary for the processing of the digital data.

This average set comprises, first of all, calculation means 42, which receive as input a digital image captured from the means 401, 402,..., 40, image capture, which record each image in a data file. numerically and which determine the number of Ni bytes contained in this file. The cameras 401, 402,..., 40n can be connected to the calculation means 42 via a parallel type link.

Comparison means are connected to the calculation means 42, receive as input the number of bytes of two captured images, and output the value of the variation ANi equal to the difference between these two numbers of bytes.

The comparison means are also connected to a table 46 of reference values variations of the number of bytes ONref. The table 46 can be stored in a read-only memory or ROM and contains, as explained above, a series of values of variations in the number of bytes for specific situations tested before commissioning the detection system of the invention, during the preliminary phase of calibration of the site.

Decision means 48 are connected to the table 46 as well as the comparison means 44. decision means 48 receive as input the variation value associated with the current image, compare it with the different reference variation values ANref read in table 46, and output as information that the variation of the associated number of bytes ONi the current image is or is not significant. The decision means 48 are furthermore connected, on the one hand, to a RAM or RAM 50, and to sound reproduction means 52 such as one or more loudspeaker (s) located on the site. under surveillance and / or connected to the monitoring terminal.

The information on the character or non-significance of the variation value of the number of bytes ANi associated with the current image, delivered by the decision means 48, is a control message intended for the random access memory and the one or more (s) 52. Indeed, in the case where the value of variation is significant, the decision means 48 control RAM 50 so that it stores the current image optionally, furthermore, the time at which this current image has been captured, control also the speaker (s) 52 so that it (s) produce) an alarm sound signal.

RAM 50 is connected to transmission means 54, receiving from RAM 50 a current image whose variation in the number of bytes is representative of the occurrence of an event or a presence, and possibly in addition, the corresponding input time, and transmit this image and optionally, in addition, instant to a monitoring terminal 56, for the purpose of confirmation and preparation of a possible intervention on the spot.

These transmission means 54 are for example constituted by modem. For reasons of privacy or professional confidentiality, as explained in the introduction, the modem operates advantageously in a unidirectional, exclusively transmission. The monitoring terminal 56 therefore receives only the images considered as suspicious by the decision means 48 and which are transmitted to it by the modem 54 and can not take other images of the site under surveillance.

When the aforementioned means 42 to 50 are included in a personal computer type, the modem 54 then being a peripheral of this computer, succession of determination steps 14, comparison 16, detection 1 22 and storage and transmission 24 described higher can be stored in the hard disk of the personal computer. personal computer may also include a parallel port or a USB type connection (in English "Universal <I> Serial Bus", </ I> universal serial bus), making the interface between the camera outputs 401, 402, ..., 40 #, and the means 42 of calculation.

The computer may furthermore be provided with a keyboard and screen (not shown in FIG. 3), which are used during the system configuration, in particular during the calibration phases (for the capture and storage of the table 46 of FIG. reference variation values of the number of bytes) and installation. This optional keypad and display can be removed after commissioning.

The computer may also include a battery-type backup power source, in order to mitigate a possible power failure, or in the event of a fire-type incident occurring on the site under surveillance.

suspicious images transmitted to the monitoring terminal can be stored on portable storage means of the diskette or CD-ROM type, for example in order to constitute for all purposes files containing the authors of possible infringements.

Advantageously, the means 42 to 50 described above can be contained in a housing protected against possible fraudulent opening attempts.

Claims (14)

<B> CLAIMS </ B> A method for detecting the occurrence of an event or presence on a monitored site, according to which digital images of said site or video images of said site converted into digital images are captured, characterized in that ) a determination step (14) is performed, during which the number of bytes (Ni) contained in the current captured digital image is determined; (b) performing a comparison step (16), in which the number of bytes (Ni) contained in the current captured digital image is compared with the number of bytes (Nref) contained in a digital reference image memorized previously, so as to obtain value of variation of the number of bytes (ONi); (c) performing a detection step (18, 22), in which, from a table of reference values of the number of bytes (ANref), it is determined whether said obtained variation value (ANi ) representative of the occurrence of an event or presence on said site; and if said obtained variation value (ANi) is representative of the occurrence of an event or a presence on said site, (d) a storage and transmission step (24) is performed, during which storing the current captured digital image and transmitting it to a monitoring terminal. 2. Method according to claim 1, characterized in that the reference digital image is the digital image captured preceding the current digital image, if the value of variation of the number of bytes (ONi) obtained from said previous captured digital image is not representative of the occurrence of an event or presence. 3. Method according to claim 1 or 2, characterized in that said table of reference values (ONref) is established during a calibration step (20) of the site to be monitored, prior to being placed under surveillance. 4. Method according to claim 1, 2 or 3, characterized in that when a variation value (ONi) is representative of the occurrence of an event or a presence, it triggers (24) an audible alarm on said site and / or to said monitoring terminal. 5. Method according to any one of the preceding claims, characterized in that after transmission to said monitoring terminal of a digital image, confirms (28) by visual assessment that an incident has actually occurred, an intruder is actually present, or that any other event or presence considered to be suspect has actually been detected. 6. Method according to any one of the preceding claims, characterized in that if a variation value (oNi) is representative of the occurrence of an event or a presence, it stores, in addition to the current image, the instant at which said current image was captured. 7. Process according to any one of the preceding claims, characterized in that the images for which the succession of steps (a) of determination, (b) comparison and (c) detection are recorded at regular intervals. 8. Process according to any one of the preceding claims, characterized in that it captures images at a variable rate depending on the nature of the site. 9. Device for detecting the appearance of an event or a presence on a site under surveillance, characterized in that it comprises - means (401, 402,... digital images or means for capturing video images and converting said video images into digital images, arranged in at least one location of said site; calculating means (42) for determining the number of bytes (Ni) contained in a digital image, connected to said input means (401, 402,..., 40 #,) <B>; </ B comparison means (44) for comparing the number of bytes contained in two digital images, said comparing means (44) being connected to said computing means (42) and providing values of variation of the number of bytes (ANi); a table (46) of reference values of the number of bytes (ONref); decision means (48) for determining, from said table (46) reference values, whether the number of byte variation values (ONi) provided by said comparison means (44) are representative of the appearance of an event or presence on the said site; means (50) for storing images; means (54) for transmitting, to transmit to a monitoring terminal (56) digital images whose value of variation in the number of bytes (ONi) is representative of the occurrence of an event or a presence. 10. Device according to claim 9, characterized in that it further comprises at least one loudspeaker (52) on said site and / or connected to said monitoring terminal, to deliver an audible alarm when a variation value ( ANi) is representative of the occurrence of an event or presence. 11. Device according to claim 9 or 10, characterized in that said means (401, 402, ..., 40 ") for capturing images comprise a plurality of color CCD type cameras. 12. Device according to any one of claims 9 to 11, characterized in that it further comprises means for storing image capture times and in that the means (54) for transmitting are adapted to transmitting said image capture times to said monitoring terminal (56). 13. Device according to any one of claims 9 to 12, characterized in that said means (54) for transmitting comprise a modem operating solely in transmission. 14. Personal computer, characterized in that it comprises a device according to any one of claims 9 to 13.