CN105913008A - Crowd exceptional event detection method based on hypothesis examination - Google Patents

Crowd exceptional event detection method based on hypothesis examination Download PDF

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CN105913008A
CN105913008A CN201610213811.9A CN201610213811A CN105913008A CN 105913008 A CN105913008 A CN 105913008A CN 201610213811 A CN201610213811 A CN 201610213811A CN 105913008 A CN105913008 A CN 105913008A
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frame
sample set
video
crowd
value
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CN105913008B (en
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徐向华
吕艳艳
李平
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Hangzhou Dianzi University
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Hangzhou Dianzi University
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06VIMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V20/00Scenes; Scene-specific elements
    • G06V20/50Context or environment of the image
    • G06V20/52Surveillance or monitoring of activities, e.g. for recognising suspicious objects
    • G06V20/53Recognition of crowd images, e.g. recognition of crowd congestion

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Abstract

The invention relates to a <{EN0}>crowd exceptional event detection method based on hypothesis examination, particularly targeting the crowd of medium density. The crowd exceptional event detection method comprises steps of using an optical flow method to capture crowd motion information so as to obtain crowd motion characteristic descriptor, extracting a characteristic vector of each pixel point from each video frame, adopting a hypothesis examination statistics method to perform classification based on motion characteristic descriptor, and performing comparison on a statistical magnitude value and a threshold value which are obtained by calculation of the hypothesis examination model so as to detect whether the exceptional event happens. The crowd exceptional event detection method not only eliminates the tedious pretreatment step in the feature extraction phase, but also uses the hypothesis examination model in the detection step, which greatly reduces the time complexity and calculation complexity during the detection process on the basis that the detection result is not reduced. The crowd exceptional event detection method not only can be used for global exceptional event detection, but also can be applied to local exceptional event detection.

Description

Based on the assumption that crowd's accident detection method of inspection
Technical field
The present invention relates to a kind of method of crowd's accident detection under public place, particularly to one Kind based on the assumption that the method for crowd's accident detection of inspection.
Background technology
In recent years, security issues become increasingly urgent in public place, and the requirement to intelligent monitoring the most more comes The highest, therefore, Video Analysis Technology has become the focus of research in many countries, along with video divides Going deep into and systematization of analysis technical research, increasing problem also shows especially out.One of them weight The crowd to public domain carries out effective monitoring to want problem to be how.To this end, each intelligent monitoring Association area develops various technology.Wherein, crowd's accident detection based on video Technology development is particularly swift and violent, and this technology can find to monitor the anomalous event in region in time, improves The response of relevant departments and rescue efficiency, thus effectively reduce public's person and the loss of property.
For crowd's accident detection problem, it is broadly divided into two basic problems, i.e. elementary events Represent and the foundation of accident detection model.Wherein elementary event represents and is broadly divided into based on low layer The representations of events of visual signature and representations of events based on high-level semantics features.Special based on Low Level Vision The representations of events levied is mainly some features that can simply extract of manual extraction, and these features are not necessarily Having strong physical significance, its method mainly has: light stream, shade of gray, objective contour etc.. Representations of events based on high-level semantics features mainly needs to carry out data the process of complexity, its thing Reason meaning is obvious.Common high-level semantics features is target space-time track etc..Wherein anomalous event inspection Survey the foundation of model, mainly have: based on the accident detection model classified and cluster, based on pushing away Disconnected accident detection model, accident detection model based on energy and based on reconstruct different Ordinary affair part detection model etc..
Although the method for crowd's accident detection is varied, but most crowd's anomalous event inspection Method of determining and calculating can not process in real time, and main difficult point is that the calculating that model inspection is time-consuming and higher is multiple Miscellaneous degree.
Summary of the invention
For the problems referred to above, the invention discloses a kind of based on the assumption that crowd's anomalous event of inspection is examined The method surveyed, the method, in feature extraction phases, still uses light stream to describe son as target travel, In the abnormality detection stage, use the method event detection as crowd's exception of hypothesis testing.With biography System method is compared, and the method does not only has preferable testing result, its time complexity and calculating complexity Degree also has substantial degradation.
The technical scheme steps that the present invention solves the employing of its technical problem is as follows:
By the present invention in that by optical flow method, capture the movable information of crowd, thus obtain the motion of crowd Feature Descriptor;For each frame of video, extract the characteristic vector of each pixel, use and assume inspection The statistical method tested carries out describing the classification of son based on motion feature;Then it will be assumed that testing model calculates The statistics value obtained compares with threshold value, thus whether detects the generation of anomalous event, is suitable for Need the crowd's scene processed in real time.
The present invention is directed to based on the crowd's accident detection under global scene specifically comprising the following steps that
Step 1: pretreatment;
First from video flowing, decoding obtains frame of video, then each frame of video is carried out gaussian filtering, Its concrete operations are: by each pixel in a template scan video frame, determine neighborhood by template The weighted average gray value of interior pixel, and by this weighted average gray value alternate template central pixel point Value;
Step 2: feature extraction;
Using the frame of video after step 1 gaussian filtering as input, use dense optical flow method Horn-Schunck calculates the light flow valuve of adjacent two interframe in video flowing pixel-by-pixel to every two field picture;
Step 3: model is set up;
The method using hypothesis testing sets up model;
Step 4: the detection of anomalous event;
By the detection model using step 3 to set up, the anomalous event under global scene is detected; This detection model is mainly each frame of video as the sample set detected, with putting down of multiple normal frame All light flow valuve is as training sample set, calculates the studentization pole between training sample set and test sample collection Difference statistic q value, and q value is made comparisons with threshold value, such as larger than threshold value, i.e. assume to be false, then Can determine whether out that this test video frame is abnormal frame, otherwise, it is assumed that set up, then can determine whether out that this test regards Frequently frame is normal frame.
The method using hypothesis testing described in step 3 sets up model, specific as follows:
3-1. process of data preprocessing
According to the result of the every two field picture light flow valuve calculated in step 2, as the sample needing detection This collection, wherein, a sample set is made up of smooth flow valuves all in single-frame images;But due to single frames In image, the quantity of pixel is more, the most just introduces the concept of integrogram, thus when reducing calculating Between;Its formula is as follows:
I'(x, y)=I (x, y)+I'(x-1, y)+I'(x, y-1)-I'(x-1, y-1)
I'(x in formula, is y) that (x, the result after y) place calculates integrogram, (x y) is single-frame images to I at point In point (x, y) the light flow valuve at place;
3-2. sets up hypothesis testing model
The general principle of hypothesis testing method is: the average assuming first that between sample set is equal, Then, according to the maxima and minima numerology biochemistry extreme difference Distribution Value of average in sample set, and with This compares with known level of signifiance selected threshold, thus judges to assume whether set up, if setting up, Then think between sample set be do not have differentiated, if being false, then it is assumed that be differentiated, go forward side by side one Step judges which sample set and other sample sets have difference;Use the sample of known normal event This collection is made comparisons with test sample collection, as long as drawing and being unsatisfactory for supposing between two sample sets, can sentence Breaking, this test sample be abnormal;Implement process as follows:
3-2-1, assumed condition H0: μ12
μ1For the average of training sample set, μ2Average for test sample;The present invention mainly chooses multiple The average of the light flow valuve of normal video frame is as training sample set, by single-frame images in test video stream Light flow valuve is as test sample collection;
3-2-2, the studentization extreme difference distribution statistics amount calculated between training sample set and test sample collection;
q = ( m a x ( &mu; d n e w , &mu; t n e w ) - m i n ( &mu; d n e w , &mu; t n e w ) ) m ( n - 1 ) C * s n e w
μ in formuladnewAnd μtnewFor the light flow valuve of test sample collection and training sample set after data prediction Average, snewFor the variance of test sample collection after data prediction and training sample set variance and Square root;Wherein, m is the number of sample set, and value is 2;N is sample point in sample set Number, C, for repairing inclined constant, is taken as 15;
3-2-3, the choosing of threshold value: for known level of signifiance α and the known free degree (m, m (n-1)), obtains q according to studentization extreme difference distribution tableαThe value of (m, m (n-1)) is as threshold value;
3-2-4, judge criterion: if calculated studentization extreme difference distribution statistics amount q is more than or equal to threshold Value qα(m, m (n-1)), then it is assumed that assumed condition H0It is false, i.e. variant between sample set, with this Just can determine whether that this test video frame is abnormal frame, otherwise, if q is less than threshold value qα(m, m (n-1)) then thinks Assumed condition H0Set up, i.e. think that this test video frame is normal frame.
The present invention is directed to based on the crowd's accident detection under the scene of local specifically comprising the following steps that
Step 1: pretreatment;
From video flowing, decoding obtains frame of video, then each frame of video is carried out gaussian filtering, its tool Gymnastics is made: by each pixel in a template scan video frame, determines picture in neighborhood by template The weighted average gray value of element, and by the value of this weighted average gray value alternate template central pixel point;
Step 2: feature extraction;
Using the frame of video after step 1 gaussian filtering as input, use dense optical flow method Horn-Schunck calculates the light flow valuve of adjacent two interframe in video flowing pixel-by-pixel to every two field picture;
Step 3: model is set up;
First frame of video is divided into the window of m1 × n1 size, then, according to calculated knot Really, the light flow valuve extracting one group of m1 × n1 area size carries out statistical analysis to draw its distribution curve, Thus find the equal Normal Distribution of light flow valuve of each window, use hypothesis testing the most equally Method set up model, detailed process is as follows:
(1) assumed condition H0: μ12
μ1For the average of training sample set, μ2Average for test sample;The present invention mainly chooses multiple The average of the light flow valuve of the window of multiple m1 × n1 sizes of normal video frame is as training sample Collection, using the light flow valuve of the window of each m1 × n1 size of single-frame images in test video stream as Test sample collection;
(2) the studentization extreme difference distribution statistics amount between sample set is calculated;
In this place owing to using the calculated feature interpretation of dense optical flow method in step 2 in the reason stage Sub-noise jamming is relatively big, and again using less m1 × n1 region as the target area of detection, this is just Make the studentization extreme difference Distribution Value calculated not accurate enough, therefore, to the light stream in m1 × n1 region Value carries out repairing operation partially, and computing formula is as follows:
x n e w = x w i n d o w - x &OverBar; w i n d o w s w i n d o w
X in formulanewFor the light flow valuve after optimizing in the window of m1 × n1 size, xwindowFor just The light flow valuve of the window of the m1 × n1 size begun,For initial m1 × n1 size The average light flow valuve of window, swindowLight flow valuve for the window of initial m1 × n1 size Standard variance;
Then the window of the m1 × n1 size after optimizing is calculated training window sample set and survey The studentization extreme difference Distribution Value of examination window sample set, computing formula is as follows:
q = ( m a x ( &mu; d n e w , &mu; t n e w ) - m i n ( &mu; d n e w , &mu; t n e w ) ) m ( n - 1 ) C * s n e w
μ in formuladnewAnd μtnewTest sample collection after optimizing for light flow valuve and training sample set equal Value, snewAfter optimizing for light flow valuve the variance of variance and the training sample set of test sample collection and flat Root;Wherein, m is the number of sample set, and n is the number of sample point in sample set, and C is for repairing partially Constant, is taken as 15;
(3) the choosing of threshold value: for known level of signifiance α and the known free degree (m, m (n-1)), Q can be obtained according to studentization extreme difference distribution tableαThe value of (m, m (n-1)) is as threshold value, and wherein m is sample This number, n is the number of sample point in each sample;
(4) criterion is passed judgment on: if calculated studentization extreme difference Distribution Value q is more than or equal to threshold value qα(m, m (n-1)), then it is assumed that assumed condition H0It is false, i.e. variant between sample set, with this just Can determine whether that this test video frame is abnormal frame, otherwise, if q is less than threshold value qα(m, m (n-1)) then thinks false If condition H0Set up, i.e. think that this test video frame is normal frame;
Step 4: the detection of anomalous event;
By the detection model using step 3 to set up, the anomalous event under the scene of local is detected; This detection model is mainly the window of certain m1 × n1 size of frame of video as the sample detected Collection, by the average light flow valuve of the windowd of multiple m1 × n1 sizes of multiple normal frame as training Sample set, calculates the studentization extreme difference statistic q value between training sample set and test sample collection, and Q value is made comparisons with threshold value, such as larger than threshold value, i.e. assume to be false, then can determine whether out that this test regards Frequently frame is abnormal frame, otherwise, it is assumed that sets up, then can determine whether out that this test video frame is normal frame.
Beneficial effects of the present invention:
1. the present invention is in feature extraction phases, simply original frame of video has been carried out simple denoising, Then carrying out the calculating of light flow valuve, this well reduces the complexity of calculating, and retains well The movable information of crowd, this is particularly suitable in middle-high density crowd.
2. the present invention sets up and detection-phase, the method employing hypothesis testing at model.The method pin To feature extraction phases, the noise that the calculating of optical flow method causes has good robustness, and the party Method is not under conditions of reducing testing result, and its time complexity has compared to traditional method very well Optimization.
Accompanying drawing explanation
Fig. 1 is the flow chart of crowd's accident detection in the case of global abnormal.
Fig. 2 is the image after frame of video carries out light flow valuve calculating in the case of global abnormal.
Fig. 3 is the testing result of frame of video in the case of global abnormal.
Fig. 4 is the flow chart of crowd's accident detection in the case of local anomaly.
Fig. 5 is the image after frame of video carries out light flow valuve calculating in the case of local anomaly.
Fig. 6 is the testing result of frame of video in the case of local anomaly.
Detailed description of the invention
Below in conjunction with the accompanying drawings, specific embodiments of the present invention are described in further detail.
Be illustrated in figure 1 based on the assumption that the method for the crowd's accident detection checked, for based on Crowd's accident detection under global scene, its concrete steps describe as shown in Figure 1:
Step 1: pretreatment.
First from video flowing, decoding obtains frame of video, then each frame of video is carried out gaussian filtering, Its concrete operations are: by each pixel in a template scan video frame, determine neighbour by template The weighted average gray value of pixel in territory, and with this weighted average gray value alternate template center pixel The value of point.
Described template, or claim convolution, mask, be size be the matrix of 0 and the 1 of N*N;
Step 2: feature extraction.
Using the frame of video after step 1 gaussian filtering as input, use dense optical flow method Horn-Schunck calculates the light flow valuve of adjacent two interframe in video flowing pixel-by-pixel to every two field picture.Its Result is as shown in Figure 2.
Step 3: model is set up.
Which frame of video in crowd's accident detection under global scene, mainly detection video set For there being anomalous event to occur.Therefore, if using the method for hypothesis testing to be modeled, then need to sentence The disconnected sample set being made up of the light flow valuve of single-frame images whether Normal Distribution.Count for step 2 The result obtained, draws its distribution curve to the light flow valuve size of every two field picture and carries out statistical analysis, It appeared that the equal Normal Distribution of light flow valuve of every two field picture, hypothesis testing therefore can be used Method sets up model.The present invention uses the method for hypothesis testing that detection target is set up model, its tool Body process is as follows:
3-1. process of data preprocessing
According to the result of the every two field picture light flow valuve calculated in step 2, as needing detection Sample set, wherein, a sample set is made up of smooth flow valuves all in single-frame images.But due to In single-frame images, the quantity of pixel is more, the most just introduces the concept of integrogram, thus reduces The calculating time.Its formula is as follows:
I'(x, y)=I (x, y)+I'(x-1, y)+I'(x, y-1)-I'(x-1, y-1)
I'(x in formula, is y) that (x, the result after y) place calculates integrogram, (x y) is single-frame images to I at point In point (x, y) the light flow valuve at place.
3-2. sets up hypothesis testing model
According to the statistic analysis result of step 3, it meets the precondition of hypothesis testing method, But owing to data are pre-processed, therefore pretreated data are further analyzed, After same drafting pretreatment, the distribution curve of data carries out statistical analysis, it appeared that pretreated Data set still Normal Distribution, therefore can use the method for hypothesis testing as anomalous event Detection model.
The general principle of hypothesis testing method is: the average assuming first that between sample set is equal, Then, according to the maxima and minima numerology biochemistry extreme difference Distribution Value of average in sample set, and Compare with known level of signifiance selected threshold with this, thus judge to assume whether set up, if becoming Vertical, then it is assumed that between sample set be do not have differentiated, if being false, then it is assumed that be differentiated, And judge which sample set and other sample sets have difference further.But in the present invention, We use the sample set of known normal event to make comparisons with test sample collection, therefore, as long as Go out and be unsatisfactory for supposing between two sample sets, may determine that this test sample is abnormal.Specifically Realize process as follows:
(1) assumed condition H0: μ12
μ1For the average of training sample set, μ2Average for test sample.The present invention mainly chooses many The average of the light flow valuve of individual normal video frame is as training sample set, by single frames figure in test video stream The light flow valuve of picture is as test sample collection.
(2) the studentization extreme difference distribution statistics amount between training sample set and test sample collection is calculated;
q = ( m a x ( &mu; d n e w , &mu; t n e w ) - m i n ( &mu; d n e w , &mu; t n e w ) ) m ( n - 1 ) C * s n e w
μ in formuladnewAnd μtnewFor test sample collection after data prediction and the light stream of training sample set The average of value, snewVariance for the variance of test sample collection after data prediction Yu training sample set Root sum square.Wherein, m is the number of sample set, and value is 2;N is sample in sample set The number of point, C, for repairing inclined constant, is taken as 15.
(3) the choosing of threshold value: for known level of signifiance α and the known free degree (m, m (n-1)), obtains q according to studentization extreme difference distribution tableαThe value of (m, m (n-1)) is as threshold value;
(4) criterion is passed judgment on: if calculated studentization extreme difference distribution statistics amount q is more than or equal to threshold Value qα(m, m (n-1)), then it is assumed that assumed condition H0It is false, i.e. variant between sample set, with this Just can determine whether that this test video frame is abnormal frame, otherwise, if q is less than threshold value qα(m, m (n-1)) then recognizes For assumed condition H0Set up, i.e. think that this test video frame is normal frame.
Step 4: the detection of anomalous event.
By the detection model using step 3 to set up, the anomalous event under global scene is detected. This detection model is mainly each frame of video as the sample set detected, by multiple normal frame Average light flow valuve, as training sample set, calculates the student between training sample set and test sample collection Change extreme difference statistic q value, and q value is made comparisons with threshold value, such as larger than threshold value, i.e. can not assume Vertical, then can determine whether out that this test video frame is abnormal frame, otherwise, it is assumed that set up, then can determine whether out This test video frame is normal frame.About the testing result under global scene as shown in Figure 3.
Be illustrated in figure 4 based on the assumption that the method for the crowd's accident detection checked, for based on The locally crowd's accident detection under scene, its concrete steps describe as shown in Figure 4:
Step 1: pretreatment.
From video flowing, decoding obtains frame of video, then each frame of video is carried out gaussian filtering, its Concrete operations are: by each pixel in a template scan video frame, determine neighborhood by template The weighted average gray value of interior pixel, and by this weighted average gray value alternate template central pixel point Value.
Described template, or claim convolution, mask, be size be the matrix of 0 and the 1 of N*N;
Step 2: feature extraction.
Using the frame of video after step 1 gaussian filtering as input, use dense optical flow method Horn-Schunck calculates the light flow valuve of adjacent two interframe in video flowing pixel-by-pixel to every two field picture, its Result is as shown in Figure 5.
Step 3: model is set up.
Which region in detection based on local anomaly event, mainly detection frame of video is different for having Ordinary affair part occurs.Therefore, if using the method for hypothesis testing to be modeled, then need to judge by list The sample set whether Normal Distribution of the light flow valuve composition in certain region of two field picture.First will regard Frequently frame is divided into the window of m1 × n1 size, then, according to the calculated result of step 2, takes out The light flow valuve taking one group of m1 × n1 area size carries out statistical analysis to draw its distribution curve, permissible Find the equal Normal Distribution of light flow valuve of each window, therefore can use the side of hypothesis testing Method sets up model.
The present invention uses the method for hypothesis testing that detection target is set up model, and its detailed process is as follows:
(1) assumed condition H0: μ12
μ1For the average of training sample set, μ2Average for test sample.The present invention mainly chooses many The average of the light flow valuve of the window of multiple m1 × n1 sizes of individual normal video frame is as training sample This collection, by the light flow valuve of the window of each m1 × n1 size of single-frame images in test video stream As test sample collection.
(2) the studentization extreme difference distribution statistics amount between sample set is calculated;
In this place owing to using the calculated feature of dense optical flow method in step 2 to retouch in the reason stage State sub-noise jamming relatively big, and again using less m1 × n1 region as the target area of detection, this The studentization extreme difference Distribution Value allowing for calculating is not accurate enough, therefore, to m1 × n1 district in the present invention Light flow valuve in territory carries out repairing operation partially, and computing formula is as follows:
x n e w = x w i n d o w - x &OverBar; w i n d o w s w i n d o w
X in formulanewFor the light flow valuve after optimizing in the window of m1 × n1 size, xwindowFor just The light flow valuve of the window of the m1 × n1 size begun,For initial m1 × n1 size The average light flow valuve of window, swindowLight flow valuve for the window of initial m1 × n1 size Standard variance.
Then the window of the m1 × n1 size after optimizing is calculated training window sample set and survey The studentization extreme difference Distribution Value of examination window sample set, computing formula is as follows:
q = ( m a x ( &mu; d n e w , &mu; t n e w ) - m i n ( &mu; d n e w , &mu; t n e w ) ) m ( n - 1 ) C * s n e w
μ in formuladnewAnd μtnewTest sample collection after optimizing for light flow valuve and training sample set equal Value, snewAfter optimizing for light flow valuve the variance of variance and the training sample set of test sample collection and Square root.Wherein, m is the number of sample set, and n is the number of sample point in sample set, and C is for repairing Constant, is taken as 15 partially.
(3) the choosing of threshold value: for known level of signifiance α and the known free degree (m, m (n-1)), can obtain q according to studentization extreme difference distribution tableαThe value of (m, m (n-1)) is as threshold Value, wherein m is the number of sample, and n is the number of sample point in each sample.
(4) criterion is passed judgment on: if calculated studentization extreme difference Distribution Value q is more than or equal to threshold value qα(m, m (n-1)), then it is assumed that assumed condition H0It is false, i.e. variant between sample set, with this just Can determine whether that this test video frame is abnormal frame, otherwise, if q is less than threshold value qα(m, m (n-1)) then thinks Assumed condition H0Set up, i.e. think that this test video frame is normal frame.
Step 4: the detection of anomalous event.
By the detection model using step 3 to set up, the anomalous event under the scene of local is detected. This detection model is mainly the window of certain m1 × n1 size of frame of video as the sample detected This collection, by the average light flow valuve of the windowd of multiple m1 × n1 sizes of multiple normal frame as instruction Practice sample set, calculate the studentization extreme difference statistic q value between training sample set and test sample collection, And q value is made comparisons with threshold value, such as larger than threshold value, i.e. assume to be false, then can determine whether out this survey Examination frame of video is abnormal frame, otherwise, it is assumed that sets up, then can determine whether out that this test video frame is normal Frame.About the testing result under the scene of local as shown in Figure 6.

Claims (5)

1. based on the assumption that inspection crowd's accident detection method, it is characterised in that by use light stream Method, the movable information of capture crowd, thus the motion feature obtaining crowd describes son;Regard for each Frequently frame, extracts the characteristic vector of each pixel, uses the statistical method of hypothesis testing to carry out based on fortune The classification of dynamic Feature Descriptor;Then it will be assumed that testing model calculated statistics value does with threshold value Relatively, thus whether detect the generation of anomalous event, be suitable for the crowd's scene needing to process in real time.
The most according to claim 1 based on the assumption that inspection crowd's accident detection method, its It is characterised by specifically comprising the following steps that for based on the crowd's accident detection under global scene
Step 1: pretreatment
First from video flowing, decoding obtains frame of video, then each frame of video is carried out gaussian filtering, Its concrete operations are: by each pixel in a template scan video frame, determine neighborhood by template The weighted average gray value of interior pixel, and by this weighted average gray value alternate template central pixel point Value;
Step 2: feature extraction;
Using the frame of video after step 1 gaussian filtering as input, use dense optical flow method Horn-Schunck Every two field picture is calculated pixel-by-pixel the light flow valuve of adjacent two interframe in video flowing;
Step 3: model is set up;
The method using hypothesis testing sets up model;
Step 4: the detection of anomalous event;
By the detection model using step 3 to set up, the anomalous event under global scene is detected; This detection model is mainly each frame of video as the sample set detected, with putting down of multiple normal frame All light flow valuve is as training sample set, calculates the studentization pole between training sample set and test sample collection Difference statistic q value, and q value is made comparisons with threshold value, such as larger than threshold value, i.e. assume to be false, then Can determine whether out that this test video frame is abnormal frame, otherwise, it is assumed that set up, then can determine whether out that this test regards Frequently frame is normal frame.
The most according to claim 2 based on the assumption that inspection crowd's accident detection method, its Be characterised by the template described in step 1, or claim convolution, mask, be size be the 0 and 1 of N*N Matrix.
The most according to claim 2 based on the assumption that inspection crowd's accident detection method, its It is characterised by that the method using hypothesis testing described in step 3 sets up model, specific as follows:
3-1. process of data preprocessing
According to the result of the every two field picture light flow valuve calculated in step 2, as the sample needing detection This collection, wherein, a sample set is made up of smooth flow valuves all in single-frame images;But due to single frames In image, the quantity of pixel is more, the most just introduces the concept of integrogram, thus when reducing calculating Between;Its formula is as follows:
I'(x, y)=I (x, y)+I'(x-1, y)+I'(x, y-1)-I'(x-1, y-1)
I'(x in formula, is y) that (x, the result after y) place calculates integrogram, (x is y) that single-frame images exists to I at point Point (x, y) the light flow valuve at place;
3-2. sets up hypothesis testing model
The general principle of hypothesis testing method is: the average assuming first that between sample set is equal, Then, according to the maxima and minima numerology biochemistry extreme difference Distribution Value of average in sample set, and with This compares with known level of signifiance selected threshold, thus judges to assume whether set up, if setting up, Then think between sample set be do not have differentiated, if being false, then it is assumed that be differentiated, go forward side by side one Step judges which sample set and other sample sets have difference;Use the sample of known normal event This collection is made comparisons with test sample collection, as long as drawing and being unsatisfactory for supposing between two sample sets, can sentence Breaking, this test sample be abnormal;Implement process as follows:
3-2-1, assumed condition H0: μ12
μ1For the average of training sample set, μ2Average for test sample;The present invention mainly chooses multiple The average of the light flow valuve of normal video frame is as training sample set, by single-frame images in test video stream Light flow valuve is as test sample collection;
3-2-2, the studentization extreme difference distribution statistics amount calculated between training sample set and test sample collection;
q = ( m a x ( &mu; d n e w , &mu; t n e w ) - m i n ( &mu; d n e w , &mu; t n e w ) ) m ( n - 1 ) C * s n e w
μ in formuladnewAnd μtnewFor the light flow valuve of test sample collection and training sample set after data prediction Average, snewFor the variance of test sample collection after data prediction and training sample set variance and Square root;Wherein, m is the number of sample set, and value is 2;N is the individual of sample point in sample set Number, C, for repairing inclined constant, is taken as 15;
3-2-3, the choosing of threshold value: for known level of signifiance α and the known free degree (m, m (n-1)), Q is obtained according to studentization extreme difference distribution tableαThe value of (m, m (n-1)) is as threshold value;
3-2-4, judge criterion: if calculated studentization extreme difference distribution statistics amount q is more than or equal to threshold value qα(m, m (n-1)), then it is assumed that assumed condition H0It is false, i.e. variant between sample set, just may be used with this Judge that this test video frame is abnormal frame, otherwise, if q is less than threshold value qα(m, m (n-1)) then thinks hypothesis Condition H0Set up, i.e. think that this test video frame is normal frame.
The most according to claim 1 based on the assumption that inspection crowd's accident detection method, its It is characterised by specifically comprising the following steps that for based on the crowd's accident detection under the scene of local
Step 1, from video flowing decoding obtain frame of video, then each frame of video is carried out gaussian filtering, Its concrete operations are: by each pixel in a template scan video frame, determine neighborhood by template The weighted average gray value of interior pixel, and by this weighted average gray value alternate template central pixel point Value;
Step 2: feature extraction;
Using the frame of video after step 1 gaussian filtering as input, use dense optical flow method Horn-Schunck Every two field picture is calculated pixel-by-pixel the light flow valuve of adjacent two interframe in video flowing;
Step 3: model is set up;
First frame of video is divided into the window of m1 × n1 size, then, is calculated according to step 2 Result, the light flow valuve extracting one group of m1 × n1 area size carries out statistical to draw its distribution curve Analysis, thus find the equal Normal Distribution of light flow valuve of each window, therefore same use assumes inspection The method tested sets up model, and detailed process is as follows:
(1) assumed condition H0: μ12
μ1For the average of training sample set, μ2Average for test sample;The present invention mainly chooses multiple The average of the light flow valuve of the window of multiple m1 × n1 sizes of normal video frame as training sample set, Using the light flow valuve of the window of each m1 × n1 size of single-frame images in test video stream as test Sample set;
(2) the studentization extreme difference distribution statistics amount between sample set is calculated;
In this place owing to using the calculated feature interpretation of dense optical flow method in step 2 in the reason stage Sub-noise jamming is relatively big, and again using less m1 × n1 region as the target area of detection, this just makes The studentization extreme difference Distribution Value that must calculate is not accurate enough, therefore, enters the light flow valuve in m1 × n1 region Row repaiies operation partially, and computing formula is as follows:
x n e w = x w i n d o w - x &OverBar; w i n d o w s w i n d o w
X in formulanewFor the light flow valuve after optimizing in the window of m1 × n1 size, xwindowFor initially The light flow valuve of window of m1 × n1 size,Window for initial m1 × n1 size Average light flow valuve, swindowThe standard side of light flow valuve for the window of initial m1 × n1 size Difference;
Then the window of the m1 × n1 size after optimizing is calculated training window sample set and test The studentization extreme difference Distribution Value of window sample set, computing formula is as follows:
q = ( m a x ( &mu; d n e w , &mu; t n e w ) - m i n ( &mu; d n e w , &mu; t n e w ) ) m ( n - 1 ) C * s n e w
μ in formuladnewAnd μtnewTest sample collection after optimizing for light flow valuve and the average of training sample set, snewAfter optimizing for light flow valuve the variance of variance and the training sample set of test sample collection and square Root;Wherein, m is the number of sample set, and n is the number of sample point in sample set, C for repairing inclined constant, It is taken as 15;
(3) the choosing of threshold value: for known level of signifiance α and the known free degree (m, m (n-1)), Q can be obtained according to studentization extreme difference distribution tableαThe value of (m, m (n-1)) is as threshold value, and wherein m is sample This number, n is the number of sample point in each sample;
(4) criterion is passed judgment on: if calculated studentization extreme difference Distribution Value q is more than or equal to threshold value qα(m, m (n-1)), then it is assumed that assumed condition H0It is false, i.e. variant between sample set, just may be used with this Judge that this test video frame is abnormal frame, otherwise, if q is less than threshold value qα(m, m (n-1)) then thinks hypothesis Condition H0Set up, i.e. think that this test video frame is normal frame;
Step 4: the detection of anomalous event;
By the detection model using step 3 to set up, the anomalous event under the scene of local is detected; This detection model is mainly the window of certain m1 × n1 size of frame of video as the sample detected Collection, by the average light flow valuve of the windowd of multiple m1 × n1 sizes of multiple normal frame as training sample This collection, calculates the studentization extreme difference statistic q value between training sample set and test sample collection, and by q Value is made comparisons with threshold value, such as larger than threshold value, i.e. assumes to be false, then can determine whether out this test video frame For abnormal frame, otherwise, it is assumed that establishment, then can determine whether out that this test video frame is normal frame.
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