Abstract:
A motion detection method based on a detecting system is used to detect a moving object and trigger a corresponding event through a set of consecutive frames. The motion detection method includes comparing duration of the event with a first threshold value for determining whether the event is valid, comparing an interval between two successive events for determining whether the latter of the successive events is combined with the first of the events, and comparing size of the moving object with a predetermined rectangle for determining whether the moving object meets a size limitation of the predetermined rectangle.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a motion detection method, and more particularly, to a motion detection method with user-adjustable parameters for better detection accuracy.  
           [0003]    2. Description of the Prior Art  
           [0004]    Digital video recordings (DVR), which have functions of monitor, video, playing, far-end control, and so on, are popular applications. The digital video recordings use a frame generator to photograph image frames and then store the image frames into a computer after a compression process. Since image compression technology is being developed rapidly, for example, MPEG4 has successfully been used in the digital video recordings, people can use limited hard disc capacity of computers to store the image frames for several weeks or one year. The digital video recordings replace old closed circuit televisions (CCTV). Since the digital video recordings use storage media (such as hard discs) to store the image frames, they do not have problems such as mildew, forgetting to switch to a new video, and difficult management of the videos, as was the case of the closed circuit televisions. Moreover, the image data are digital data, so that the image data can be quickly transmitted to distant places through a network, thereby decreasing the transmission time. People in the distant places can receive the image data fast. In addition, the digital image data can be further processed. For example, the digital video recordings always have a monitor and an alarm, so that the digital video recordings can perform the monitor operation through the digital signal. The digital video recordings determine whether an object is moving according to the computer operation, so as to generate a corresponding warning signal.  
           [0005]    A prior art detection method uses a calculating device to compare a plurality of image frames generated by a frame generator so as to determine whether an object is moving inside a scene. The calculating device compares a first image frame with a successive second image frame inside the plurality of image frames so as to determine whether the object is moving inside the scene. In general, when the object is moving, a plurality of pixels inside the image frame generated by the frame generator is changed. Therefore, when comparing the first image frame with the second image frame, the calculating device can use a change of the plurality of pixels inside the first and second image frame to be a judge criterion. That means when the plurality of pixels of the image frame are changed, the calculating device can determine whether something is moving inside the scene according to the first image frame and the second image frame.  
           [0006]    Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of a prior art detecting system  50 . FIG. 2 is a block diagram of the prior art detecting system  50 . As mentioned above, the detecting system  50  determines whether something is moving inside a scene  52  according to a predetermined detection method. The detecting system  50  comprises a frame generator  20  and a calculating device  30 . The frame generator  20  is used to periodically picture the scene  52  according to a predetermined period (30 times per second) to generate a plurality of image frames  22 . The calculating device  30  is used to process a first image frame  24  and a second image frame  26  inside the plurality of image frames  22 , and compare the first image frame  24  with the second image frame  26  according to the predetermined detecting method so as to determine whether something is moving inside the scene  52 . When the calculating device  30  determines whether something is moving inside the scene  52 , the calculating device  30  compares each pixel of the second image frame  26  with the corresponding pixel of the first image frame  24  so as to calculate an amount of different pixels between the first and second image frame  24 ,  26 . When the amount of the different pixels is larger than a predetermined value, the detecting system  50  determines that something is moving inside the scene  52 , otherwise, the detecting system  50  determines that there is not anything moving inside the scene  52 .  
           [0007]    However, there are some things that are not important for users even though they are moving. For example, users use the detecting system  50  to detect whether something is moving around a door of a house (scene  52 ). When a leaf is falling down, the frame generator  20  pictures the falling leaf in order to obtain the plurality of image frames  22 . The calculating device  30  compares the plurality of image frames  22 . Since the falling leaf makes the pixels of each image frame  22  change, the detecting system  50  determines that an object is moving inside the scene  52  and generates a corresponding warning signal. However, the falling leaf is not important for users, it is unnecessary to process an event corresponding to the falling leaf or to detonate the warning signal. Similarly, when a passerby goes past the door of the house quickly, the detecting system  50  also determines that something is moving inside the scene  52 . Therefore, the detecting system  50  always detects events that are not important for users. Users hope that the detecting system  50  can generate a corresponding warning signal when a dubious stranger moves around before the door. However, when a large object (such as a truck) or a small object (such as a mouse) goes pass the door, that means objects are moving inside the scene  52 . Then the calculating device  30  compares the successive image frames  22  and the detecting system  50  determines that there are objects moving inside the scene  52 , thereby a warning signal is generated. However, the truck or the mouse is not the detecting target (dubious stranger) for users. That means the prior art detecting system  50  is unable to filter the unimportant large object and little object, meaning that the prior art detecting system  50  easily generates an incorrect determination. In addition, the detecting system  50  generates the warning signal only when object is moving inside the scene  52 . Therefore, when the dubious stranger is moving before the door of the user, the detecting system  50  records the corresponding image frame  22  and generates the warning signal. However, when the dubious stranger remains motionless, since the detecting system  50  does not detect anything is moving, the detecting system  50  does not record the corresponding image frame  22 . When the dubious stranger starts to move again after keeping motionless, the detecting system  50  determines that something is moving inside the scene  52 , generates the warning signal, and records the corresponding image frames  22 . Although the same object generates the first event and the second event, the detecting system  50  is unable to recognize this, so that the detecting system  50  determines that the two events are generated by different objects. Therefore, the detecting system  50  ignores a period in which the dubious stranger remains motionless. The detecting system  50  does not generate the corresponding warning signal or record the corresponding image frame during the motionless period.  
         SUMMARY OF INVENTION  
         [0008]    It is therefore a primary objective of the claimed invention to provide a motion detection method that can prevent incorrect detections.  
           [0009]    The claimed invention, briefly summarized, discloses a motion detection method with user-adjustable parameters for better detection accuracy. The motion detection method is based on a detecting system for detecting a moving object and triggering a corresponding event through a set of consecutive frames. The motion detection method comprises comparing duration of the event with a first threshold value for determining whether the event is valid, comparing an interval between two successive events for determining whether the latter of the successive events is combined with the first of the events, and comparing size of the moving object with a predetermined rectangle for determining whether the moving object meets a size limitation of the predetermined rectangle.  
           [0010]    It is an advantage of the claimed invention that the claimed invention satisfies the detection demands of users and also avoids the incorrect determinations.  
           [0011]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    [0012]FIG. 1 is a perspective view of a prior art detecting system.  
         [0013]    [0013]FIG. 2 is a block diagram of the prior art detecting system.  
         [0014]    [0014]FIG. 3 is a flow chart of a first embodiment of a present invention motion detection method.  
         [0015]    [0015]FIG. 4 is a perspective view of the first embodiment of the present invention motion detection method.  
         [0016]    [0016]FIG. 5 is a flow chart of a second embodiment of the present invention motion detection method.  
         [0017]    [0017]FIG. 6 is a perspective view of the second embodiment of the present invention motion detection method.  
         [0018]    [0018]FIG. 7 is a flow chart of a third embodiment of the present invention motion detection method.  
         [0019]    [0019]FIG. 8 to FIG. 10 are perspective views of the third embodiment of the present invention motion detection method. 
     
    
     DETAILED DESCRIPTION  
       [0020]    A structure of the present invention motion detection method is same as the prior art detecting system  50  shown in FIG. 1 and FIG. 2. The frame generator  20  is used to periodically picture a scene  52  according to a predetermined period to generate a plurality of image frames  22 . The calculating device  30  is used to compare successive image frames to detect whether an object is moving inside the scene  52 . When an object is moving, the calculating device  30  generates an event corresponding to the moving object. The event includes the image frames  22  associated with the moving objects. Please refer to FIG. 3 and FIG. 4. FIG. 3 is a flow chart of a first embodiment of the present invention motion detection method. FIG. 4 is a perspective view of the first embodiment of the present invention motion detection method. The procedures of the first embodiment of the present invention motion detection method are described as follows:  
         [0021]    Step  100 : Compare a duration of the event with a first threshold value, if the duration of the event is larger than the threshold value, execute step  102 , otherwise, execute step  104 ;  
         [0022]    Step  102 : Determine that the event is valid, the detecting system  50  records the event; and  
         [0023]    Step  104 : Determine that the event is not valid, the detecting system  50  does not record the event.  
         [0024]    An operation of the first embodiment of the present invention motion detection method is illustrated as follows. For easy illustration, the frame generator  20  of the first embodiment pictures two image frames each second. One horizontal axis in FIG. 4 represents time, and another axis represents picture section number of the image frame. A first threshold value is set to be 1.5 seconds. The frame generator  20  pictures the scene  52  and generates an image frame  22  every 0.5 seconds. The calculating device  30  compares the successive image frames  22 . When the calculating device  30  compares the image frame  22  of picture section  2  with the image frame  22  of picture section  3 , since the image frame  22  of picture section  2  is different from picture section  3 , the calculating device  30  determines that an object is moving inside the scene  52  (according to the prior art detecting method). Therefore, the detecting system  50  detonates a first event  60 . The first event  60  includes the image frames  22  of picture sections  2  and  3 . Continuously, the calculating device  30  compares the image frame  22  of picture section  3  with picture section  4 . Since the image frame  22  of picture section  4  is different from picture section  3 , the calculating device  30  determines that the object is still moving. Therefore, the detecting system  50  continuously detonates the first event  60 . Now, the first event  60  includes the image frames  22  of picture sections  2  to  4 . Repeat the detecting operation above. When the calculating device  30  compares the image frame  22  of picture section  6  with picture section  5 , since the object dose not move in picture section  6 , the detecting system  50  stops to detonate the first event  60 . Therefore, the first event  60  is detonated starting from the image frame  22  of picture section  2  and stopping at the image frame  22  of picture section  5 . That means the first event  60  includes the image frames  22  of picture sections  2  to  5 . Similarly, the calculating device  30  detonates a second event  62  that includes the image frames  22  of picture sections  7  and  8 , a third event  64  includes the image frame  22  of picture sections  13  to  15 , and a fourth event  66  that includes the image frames  22  of picture sections  1   7  to  22 . The duration of the first event  60  is 2 seconds. The duration of the second event  62  is 0.5 seconds. The duration of the third event  64  is 1 second. The duration of the fourth event  66  is 2.5 seconds. Since the first threshold value is 1.5 seconds, the second event  62  and the third event  64  are ignored by the detecting system  50 . The detecting system  50  does not record the second event  62  and the third event  64 , and does not detonate any warning signal. Any event which has a duration less than the first threshold value is ignored by the detecting system  50 . Users can adjust the first threshold value according to the detection demand in order to control the detecting system  50  to filter the unnecessary events. When a leaf is falling down or a passerby is passing before the door, the detecting system  50  ignores the event which has a duration less than the first threshold value set by users. Therefore, the detecting system  50  does not generate incorrect determinations.  
         [0025]    Please refer to FIG. 5 and FIG. 6. FIG. 5 is a flow chart of a second embodiment of the present invention motion detection method. FIG. 6 is a perspective view of the second embodiment of the present invention motion detection method. Procedures of the second embodiment of the present invention motion detection method are illustrated as follows:  
         [0026]    Step  200 : The detecting system  50  detects two successive events which includes a first event and a second event, an interval separates a termination of the first event and a beginning of the second event;  
         [0027]    Step  202 : Compare the interval with a second threshold value, if the interval is larger than the second threshold value, execute step  204 , otherwise, execute step  206 ;  
         [0028]    Step  204 : Determine that the second event is not related to the first event, the detecting system  50  records both the first event and the second event; and  
         [0029]    Step  206 : Determine that the second event is related to the first event, the second event is merged into the first event, and the detecting system  50  only records the first event which includes image frames  22  generated within the durations of the first and second events and the interval between the first and second events.  
         [0030]    An operation of the second embodiment of the present invention motion detection method is illustrated as follows. In the second embodiment, one horizontal axis represents time, and another horizontal axis represents a picture section number of the image frames  22 . The second threshold value is 4 seconds. The frame generator  20  pictures the scene  52  to generate an image frame  22  every 0.5 seconds. As mentioned above, the calculating device  30  compares two successive image frames  22  so as to detect the moving object inside the scene  52  (according to the prior art detection method). The detecting system  50  detects a fifth event  68  which includes the image frames  22  of picture sections  1  to  4 , a sixth event  70  which includes the image frames  22  of picture sections  6  and  7 , a seventh event  72  which includes the image frames  22  of picture sections  11  to  13 , a eighth event  74  which includes the image frames  22  of picture sections  22  and  23 , and a ninth event  76  which includes the image frames  22  of picture sections  25  to  29 . A first interval  78  between the fifth event  68  and the sixth event  70  is 1 second. Since the second threshold value is 4 seconds, the sixth event  70  is related to the fifth event  68  and the sixth event  70  is merged into the fifth event  68 . That means the fifth event  68  includes the sixth event  70  and the fifth event  68  records the image frames  22  of picture sections  1  to  7 . A second interval  80  between the sixth event  70  and the seventh event  72  is 1.5 seconds. The second interval  80  is less than the second threshold value. Therefore, the seventh event  72  is related to the sixth event  70  so that the seventh event  72  is merged into the fifth event  68 . That means the fifth event  68  includes the sixth event  70  and the seventh event  72 . The fifth event  68  records the image frames  22  of picture sections  1  to  13 . A third interval  82  between the seventh event  72  and the eighth event  74  is 4.5 seconds. The third interval  82  is larger than the second threshold value so that the eighth event  74  is not related to the seventh event  72 . The eighth event  74  is also not related to the fifth event  68 . A fourth interval  84  between the eighth event  74  and the ninth event  76  is 1 second. The fourth interval  84  is less than the second threshold value so that the ninth event  76  is related to the eighth event  74 . The ninth event  76  is merged into the eighth event  74 . The eighth event  74  includes the ninth event  76  and records the image frames  22  of picture sections  22  to  29 . As mentioned above, the detecting system  50  lastly obtains the fifth event  68  which includes the image frames  22  of picture sections  1  to  13 , and the eighth event  74  which includes the image frames  22  of picture sections  22  to  29 . Users can adjust the second threshold value according to the detection demand in order to control the detecting system  50  to filter the unnecessary events. When a dubious stranger walk-around inside the scene  52 , the detecting system  50  can determine the relationship of the events according to the second threshold value set by users. Therefore, the detecting system  50  does not detect the incorrect detection.  
         [0031]    Please refer to FIG. 7 to FIG. 10. FIG. 7 is a flow chart of a third embodiment of the present invention motion detection method. FIG. 8 to FIG. 10 are perspective views of the third embodiment of the present invention motion detection method. Procedures of the third embodiment of the present invention motion detection method are illustrated as follows:  
         [0032]    Step  300 : Set a first filtering range and a second filtering range, in which the second filtering range is larger than the first filtering range;  
         [0033]    Step  302 : Compare a size of the moving object with the first filtering range, if the size of the moving object is larger than the first filtering range, execute step  306 , otherwise, execute step  304 ;  
         [0034]    Step  304 : The detecting system  50  ignores the moving object and does not record the event associated with the moving object;  
         [0035]    Step  306 : Compare the size of the moving object with the second filtering range, if the size of the moving object is larger than the second filtering range, execute step  308 , otherwise, execute step  310 ;  
         [0036]    Step  308 : The detecting system  50  ignores the moving object and does not record the event associated with the moving object; and  
         [0037]    Step  310 : The detecting system  50  records the event associated with the moving object.  
         [0038]    An operation of the third embodiment of the present invention motion detection method is illustrated as follows. In the third embodiment, users set the first filtering range  86  and the second filtering range  88 . The second filtering range  88  is larger than the first filtering range  86 . The second filtering range  88  is used to select large moving objects (such as a truck), and the first filtering range is used to select small moving object (such as a mouse). The first filtering range  86  and the second filtering range  88  can be rectangles, circles, or other polygons which are used to define a range. When a first moving object  90  (such as a mouse) appears inside the scene  52 , as shown in FIG. 8, since a size of the first moving object  90  is smaller than the first filtering range  86 , the detecting system  50  ignores the first moving object  90  and does not record the event associated with the first moving object  90  (step  304 ). When a second moving object  92  (such as a truck) appears inside the scene  52 , as shown in FIG. 9, since a size of the second moving object  92  is larger than the first filtering range  86 , the detecting system  50  continuously compares the size of the second moving object  92  with the second filtering range (step  306 ). The size of the second moving object  92  is also larger than the second filtering range  88 , so that the detecting system  50  ignores the second moving object  92  and does not record the event associated with the second moving object  92  (step  308 ). However, when a third moving object  94  (such as a person) appears inside the scene  52 , as shown in FIG. 10, since a size of the third moving object  94  is larger than the first filtering range  86 , the detecting system  50  continuously compares the size of the third moving object  94  with the second filtering range (step  306 ). The size of the third moving object  94  is smaller than the second filtering range  88 , so that the detecting system  50  records the event associated with the third moving object  94  (step  310 ). Users can adjust the first filtering range  86  and the second filtering range  88  according to detection demands so as to control the detecting system  50  to filter out unnecessary events. For example, users request the detecting system to generate the warning signal only when a dubious stranger walks around the door. Users can set the first filtering range  86  which is smaller than the size of a general human body, and set the second filtering range  88  which is larger than the size of a general human body. Therefore, the detecting system  50  can record the image frames  22  of all the moving objects which have sizes near that of the human body, according to the first filtering range  86  and the second filtering range  88 , and also generate the corresponding warning signal. The detecting system  50  ignores the moving objects which have size less than the first filtering range  86  (such as a mouse) or larger than the second filtering range  88  (such as a truck) in order to avoid incorrect determinations. The third embodiment uses the first filtering range  86  and the second filtering range  88  to filter the unimportant moving objects and record the events associated with the important moving objects. Users also can picture the different moving object according to the different combinations of the first filtering range  86  and the second filtering range  88 . For example, if users only use the first filtering range  86  to filter the moving object, the detecting system  50  can picture the moving objects which have size smaller than the first filtering range  86  or larger than the first filtering range  86 . If users use the first filtering range  86  and the second filtering range  88  to filter the moving object, the detecting system  50  can picture the moving objects which have size between the first filtering range  86  and the second filtering range  88 . If users only use the second filtering range  88  to filter the moving object, the detecting system  50  can picture the moving objects which have size larger than the second filtering range  88  or smaller than the second filtering range  88 . Therefore, users can select the filtering range and the combination of the filtering range according to the detecting demand. Thus, users can select one or two of the moving objects  90 ,  92 ,  94 , or all the moving objects  90 ,  92 ,  94  shown in FIG. 8 to FIG. 10. Moreover, the third embodiment can also choose the plurality of the combinations from the plurality of the filtering ranges so as to define the plurality of different filtering ranges. Therefore, the detecting system  50  can choose multiple moving objects which belong to different filtering range combinations.  
         [0039]    All of the first, second, and third embodiments of the present invention motion detection method can prevent the detecting system  50  from generating incorrect determinations. The present invention motion detection method can combine two of the embodiments to detect the moving objects, or combine all of the embodiments to detect the moving objects so as to further prevent the detecting system  50  from generating the incorrect determinations.  
         [0040]    In contrast to the prior art, the present invention motion detection method uses the first threshold value to filter events which have a short duration, uses the second threshold value to determine whether the two events are continuous so as to differentiate between the different events, and use two different filtering ranges to filter unimportant moving objects. Therefore, users can set and combine the first threshold value, the second threshold value, and the filtering ranges according to different detection demands. The present invention motion detection method satisfies the detection demands of users and also avoids the incorrect determinations.  
         [0041]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.