Automatic wide dynamic control method for security and protection monitoring equipment

Abstract

The invention relates to an automatic wide dynamic control method for security and protection monitoring equipment, which can quickly and correctly judge whether a current scene is a wide dynamic scene or not, automatically switch a wide dynamic mode, give an intensity value after entering the wide dynamic mode, and further solve the problem that when a moving object exists in the scene, the current scene cannot be automatically switched. Image distortion is caused by scene fusion errors; and a Sensor wide dynamic algorithm has the problems of large low-illumination dark area noise, poor effect and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of image processing, and relates to an automatic wide dynamic range control method, in particular to an automatic wide dynamic range control method for security monitoring equipment. Background Art

[0002] In the field of images, the scenes that require technical processing are rich and varied, and these scenes have different color temperatures, brightness, dynamic ranges, etc. Among them, how to perfectly restore the real scene in a scene with a large dynamic range is a difficult problem in the field of security and even the entire digital photography.

[0003] What is a wide dynamic scene? When we watch the football match broadcast held in the afternoon, due to the open-air venue and the change of the sun's incident angle, there will be obvious shadow areas and direct sunlight areas on the field of the stadium. In the broadcast image, usually only one of the areas will look good, and the other area is usually underexposed with insufficient brightness or overexposed with excessive brightness. In a scene where light and dark exist at the same time, it is difficult to express all the detailed features of the light and dark areas at the same time, resulting in the loss of some scene elements in the image. The reason for this phenomenon is that the brightness of different areas of the shooting scene is very different. The actual brightness difference between the light and dark areas may be thousands of times or even greater.

[0004] At present, the storage and display format of common images is only 8-bit data, and the storage range is 0-255 characters. Therefore, there is a large gap between the data storage accuracy and the actual image accuracy. For scenes with a wide dynamic range of brightness, special processing is required.

[0005] In the field of security, there are many solutions for wide dynamic range on the market. They are roughly divided into the following two types: digital wide dynamic range algorithm and sensor wide dynamic range algorithm. The digital wide dynamic range algorithm maps the brightness value of each pixel in the image according to certain rules, stretches the grayscale of the frequency band with serious grayscale stacking, improves the image resolution, and achieves wide dynamic range scene adaptation. The sensor wide dynamic range algorithm is an algorithm based on sensor support. Each frame of the sensor output is a fusion of two frames of long frame exposure and short frame exposure. By controlling the ratio of exposure time, the problem of large dynamic range is solved.

[0006] However, both of these commonly used solutions have certain defects. The digital wide dynamic algorithm does not really increase the actual dynamic range of the image, so the brightness in the dark areas increases but the scene details are still not reflected, resulting in reduced image transparency and decreased image quality; and image distortion due to grayscale value mapping. Because the two frames of the Sensor wide dynamic algorithm are not synchronized in exposure, when there are moving objects in the scene, the scene fusion fails and causes image distortion; and the Sensor wide dynamic algorithm has problems such as large noise in low-light dark areas and poor effects.

[0007] In summary, current technical means can solve the problem of wide dynamic scenes in images, but have poor adaptability and will introduce new problems.

[0008] However, in the field of security, the same scene needs to be controlled 24 hours a day. Usually, the scene changes with the day and night cycle, so the scene elements are different in different time periods. The typical wide dynamic scene will also become a non-wide dynamic scene in different time periods. For users, it is impossible to manually switch or turn on and off the wide dynamic algorithm at any time in different time periods.

[0009] Therefore, the present invention proposes a wide dynamic range control method that automatically switches according to different scenes.

[0010] After searching, no public documents of the prior art identical or similar to the present invention were found. Summary of the invention

[0011] The purpose of the present invention is to overcome the shortcomings of the prior art and propose an automatic wide dynamic control method for security monitoring equipment, which can quickly and correctly determine whether the current scene is a wide dynamic scene, automatically switch the wide dynamic mode, and give an intensity value after entering the wide dynamic mode, thereby solving the problems of image distortion caused by scene fusion errors when there are moving objects in the scene; and the problems of large noise in low-light dark areas and poor effects in the Sensor wide dynamic algorithm.

[0012] The present invention solves the practical problem by adopting the following technical solutions:

[0013] An automatic wide dynamic control method for security monitoring equipment comprises the following steps:

[0014] S1. Set the time filter counter time, and add time filter before all mode switching operations;

[0015] S2, obtaining the statistical information of the automatic exposure module AE of the current frame, and determining whether there is a difference between the statistical information of the current frame and the statistical information of the previous frame;

[0016] S3, determine whether the device has PTZ three-axis motion;

[0017] S4, determining whether the device meets the requirements of wide dynamic mode picture brightness;

[0018] S5, obtaining the brightness of each pixel block of the current frame AE statistical information to obtain a pixel block brightness histogram;

[0019] S6, counting the number of pure long-frame pixel blocks and the number of pure short-frame pixel blocks in the pixel block brightness histogram;

[0020] S7. Setting a long frame number threshold and a short frame number threshold according to experience values;

[0021] S8, determining the relationship between the number of pure long frame pixel blocks and the long frame number threshold;

[0022] S9. Determine whether to use the linear wide dynamic algorithm or the sensor wide dynamic algorithm:

[0023] S10, calculating a control strength value of the sensor wide dynamic algorithm according to the area and brightness difference between the dark area and the bright area in the current image, where the control strength value is used to measure the strength of the sensor wide dynamic algorithm's image control capability;

[0024] S11, calculating a control strength value of the linear wide dynamic algorithm according to the area of ​​the dark area and the brightness difference in the current image, where the control strength value is used to measure the strength of the linear wide dynamic algorithm's image control capability.

[0025] Moreover, the specific method of step 1 is:

[0026] Set the time filter counter time, using the "add one subtract one" method. When mode switching is required, it is not performed immediately, but replaced by the operation of adding one to the relevant counter. The mode switching is performed only when the counter value reaches a certain value. If the judgment result changes during the process, the counter is reduced by one.

[0027] Moreover, the specific method of step S2 is:

[0028] Get the statistical information of the automatic exposure module AE of the current frame, collect the overall brightness of the current picture, the ambient brightness, and the overall RGB pixel ratio of the current picture. If there is no statistical information of the previous frame, directly proceed to S3 judgment; if there is statistical information of the previous frame, judge it with the statistical information of the previous frame. When the above statistical information has not changed significantly, it is considered that the current scene is stable, and directly enter the next frame to re-judge S2, and counter time-1, the minimum time is 0; and when one or more of the above parameters have changed significantly, it is considered that the scene has changed, and continue to S3.

[0029] Moreover, the specific method of step S3 is:

[0030] When the device undergoes ptz three-axis motion, the counter time is reset, the AE statistical information cache of the previous frame is cleared, the algorithm judgment is suspended, and the wide dynamic state and intensity before the motion are maintained until the motion stops; after the device stops moving, S2 is re-judged; if the device does not undergo ptz three-axis motion, continue with S4.

[0031] Moreover, the specific method of step S4 is:

[0032] When in wide dynamic mode, when the overall brightness value of the AE statistical information is greater than the set over-brightness threshold or lower than the over-darkness threshold, the wide dynamic mode should be exited and the counter time should be reset. If it is not currently in wide dynamic mode, proceed to S5.

[0033] Moreover, the specific method of step S5 is:

[0034] Obtain the brightness of each pixel block of the current frame AE statistical information to obtain a pixel block brightness matrix, and perform a spatial filtering operation on the pixel block brightness matrix to obtain a pixel block brightness histogram;

[0035] Moreover, the specific method of step S6 is:

[0036] Obtain the short frame threshold and long frame threshold in the wide dynamic processing module and compare them with the pixel block brightness histogram obtained from the AE statistical information: in the pixel block brightness histogram, the pixel blocks less than the short frame threshold are regarded as pure short frame pixel blocks, the pixel blocks greater than the long frame threshold are regarded as pure long frame pixel blocks, and the pixel blocks greater than the short frame threshold and less than the long frame threshold are regarded as long-short frame fusion pixel blocks; count the number of pure long frame pixel blocks and the number of pure short frame pixel blocks in the pixel block brightness histogram.

[0037] Moreover, the specific method of step S8 is:

[0038] If the number of pure long frame pixel blocks is less than the long frame number threshold, the counter time-1, and re-judge S2 in the next frame; when the number of long frame pixel blocks is greater than the long frame number threshold, the counter time+1, if time<=10, re-judge S2 in the next frame, if the counter is greater than time>10, execute S9;

[0039] Moreover, the specific method of step S9 is:

[0040] If the following conditions are satisfied: Num_Long>Th_Long and Num_Short>Th_Short, use the sensor wide dynamic algorithm and execute S10; if the following conditions are satisfied: Num_Long>Th_Long and Num_Short≦Th_Short, use the linear wide dynamic algorithm and execute S11.

[0041] Among them, Num_Long: the number of pure long frame pixel blocks; Num_Short: the number of pure short frame pixel blocks; Th_Long: the long frame number threshold; Th_Short: the short frame number threshold;

[0042] Moreover, the calculation formula of the sensor wide dynamic algorithm control intensity value Hdr_Intensity in step S10 is as follows:

[0043] Hdr_Intensity_sensor=(Num_Long+Num_Short-Floor_Limit_long_short) / Top_Limit_long_short*255;

[0044] Among them, Num_Long is the number of pure long frame pixel blocks; Num_Short is the number of pure short frame pixel blocks; Floor_Limit_long_short is the lower limit of the reference long and short frame number; Top_Limit_long_short is the upper limit of the reference long and short frame number; the lower limit of the reference long and short frame number and the upper limit of the reference long and short frame number are preset values ​​in the wide dynamic processing module;

[0045] The calculation formula of the linear wide dynamic control intensity Hdr_Intensity in step S11 is as follows:

[0046] Hdr_Intensity_linear=(Num_Long-Floor_Limit_long) / Top_Limit_log*255

[0047] Among them, Num_Long is the number of pure long frame pixel blocks; Floor_Limit_long is the lower limit of the reference long frame number; Top_Limit_long is the upper limit of the reference long frame number; the lower limit of the reference long and short frame number and the upper limit of the reference long and short frame number are preset values ​​in the wide dynamic processing module.

[0048] Advantages and beneficial effects of the present invention:

[0049] The present invention proposes an automatic wide dynamic control method for security monitoring equipment, which uses the ratio of long to short frames to determine whether there is a large area of ​​light and dark areas in the current picture, and then determines whether the current picture is a wide dynamic scene. The present invention can quickly and correctly determine whether the current scene is a wide dynamic scene.

[0050] 2. After entering the wide dynamic mode, the present invention can provide a reasonable strength index to control the wide dynamic algorithm, thereby better allowing the picture to highlight more details.

[0051] 3. The method of the present invention is stable. When the device is focusing, rotating, or an object is moving rapidly in the scene, the image is stable, thus avoiding the screen flickering phenomenon caused by frequent switching of the wide dynamic mode, improving the feasibility of the algorithm, and making the image more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a process flow chart of the present invention;

[0053] Figure 2 It is a time filter counter processing flow chart of the present invention;

[0054] Figure 3 Schematic diagram of the AE brightness spatial filtering template of the present invention;

[0055] FIG4( a ) is a diagram showing the processing result of the present invention - with wide dynamic range turned off;

[0056] FIG4( b ) is a diagram showing the processing result of the present invention - linear wide dynamic range turned on (low intensity);

[0057] FIG4( c ) is a diagram showing the processing result of the present invention - linear wide dynamic range turned on (high intensity);

[0058] FIG4( d ) is a diagram showing the processing result of the present invention - sensor wide dynamic range is turned on (low intensity);

[0059] FIG4(e) is a diagram showing the processing result of the present invention - sensor wide dynamic range is turned on (high intensity). DETAILED DESCRIPTION

[0060] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

[0061] An automatic wide dynamic control method for security monitoring equipment, such as Figure 1 As shown, the following steps are included:

[0062] S1. Set the time filter counter time, and add time filter before all mode switching operations;

[0063] The specific method of step 1 is:

[0064] Set the time filter counter time, and use the "add one subtract one" method. When mode switching is required, it is not performed immediately, but replaced by the operation of adding one to the relevant counter. The mode switching is performed only when the counter value reaches a certain value. If the judgment result changes during the process, the counter is reduced by one.

[0065] like Figure 2As shown, in this embodiment, in order to solve the problem of screen flickering caused by frequent mode switching due to excessive algorithm sensitivity, the present invention adds time filtering before all mode switching operations. Time filtering adopts the "add one minus one" method, that is, when the above-mentioned judgment algorithms are successful and mode switching is required, the mode switching is not performed immediately, but replaced by the operation of adding one to the relevant counter. The mode switching is performed only when the counter value reaches a certain value. If the judgment result changes during the process, the counter is reduced by one.

[0066] S2, obtaining the statistical information of the automatic exposure module (hereinafter referred to as AE) of the current frame. Determine whether there is a difference between the statistical information of the current frame and the statistical information of the previous frame;

[0067] The specific method of step S2 is:

[0068] Obtain the statistical information of the current frame's automatic exposure module (hereinafter referred to as AE), collect the current picture's overall brightness, ambient brightness, and the current picture's overall RGB pixel ratio. If there is no statistical information of the previous frame, directly proceed to S3 judgment; if there is statistical information of the previous frame, judge it with the statistical information of the previous frame. When the above statistical information has not changed significantly, it is considered that the current scene is stable, and directly enter the next frame to re-judge S2, and counter time-1, with the minimum time being 0; and when one or more of the above parameters have changed significantly, it is considered that the scene has changed, and continue to S3.

[0069] S3, determine whether the device has PTZ three-axis motion;

[0070] The specific method of step S3 is:

[0071] When the device undergoes ptz three-axis motion, the counter time is reset, the AE statistical information cache of the previous frame is cleared, the algorithm judgment is suspended, and the wide dynamic state and intensity before the motion are maintained until the motion stops; after the device stops moving, S2 is re-judged; if the device does not undergo ptz three-axis motion, continue with S4.

[0072] In this embodiment, the current step is very important for monitoring equipment in the security field. A large number of devices have the capabilities of zooming, camera rotation, etc. Therefore, when the device performs PTZ three-axis motion, it must be ensured that the mode switching operation is not currently entered, otherwise there is a risk of screen flickering.

[0073] S4, determining whether the device meets the requirements of wide dynamic mode picture brightness;

[0074] The specific method of step S4 is:

[0075] When in wide dynamic mode, when the overall brightness value of the AE statistical information is greater than the set over-brightness threshold or lower than the over-darkness threshold, the wide dynamic mode should be exited and the counter time should be reset. If it is not currently in wide dynamic mode, proceed to S5.

[0076] In this embodiment, the effect of using the wide dynamic algorithm is poor in scenes with too bright or very low illumination, so when the overall brightness of the AE statistical information is too high or too low, the wide dynamic mode is exited. The design of the threshold is related to the device hardware, and different devices have different thresholds for brightness.

[0077] S5, obtaining the brightness of each pixel block of the current frame AE statistical information to obtain a pixel block brightness histogram;

[0078] The specific method of step S5 is:

[0079] Obtain the brightness of each pixel block of the current frame AE statistical information to obtain a pixel block brightness matrix, and perform a spatial filtering operation on the pixel block brightness matrix to obtain a pixel block brightness histogram;

[0080] In this embodiment, the AE brightness spatial filtering template of the spatial filtering operation is as follows: Figure 3 shown.

[0081] This spatial filtering operation can effectively eliminate the interference caused by various noises such as circuit thermal noise and sensor thermal noise, and can also effectively reduce the order of magnitude of calculations in subsequent steps, providing feasibility for use in embedded devices.

[0082] S6, counting the number of pure long-frame pixel blocks and the number of pure short-frame pixel blocks in the pixel block brightness histogram;

[0083] The specific method of step S6 is:

[0084] Obtain the short frame threshold and long frame threshold in the wide dynamic processing module and compare them with the pixel block brightness histogram obtained from the AE statistical information: in the pixel block brightness histogram, the pixel blocks less than the short frame threshold are regarded as pure short frame pixel blocks, the pixel blocks greater than the long frame threshold are regarded as pure long frame pixel blocks, and the pixel blocks greater than the short frame threshold and less than the long frame threshold are regarded as long-short frame fusion pixel blocks; count the number of pure long frame pixel blocks and the number of pure short frame pixel blocks in the pixel block brightness histogram.

[0085] S7. Setting a long frame number threshold and a short frame number threshold according to experience values;

[0086] S8, determining the relationship between the number of pure long frame pixel blocks and the long frame number threshold;

[0087] The specific method of step S8 is:

[0088] If the number of pure long frame pixel blocks is less than the long frame number threshold, the counter time-1, and re-judge S2 in the next frame; when the number of pure long frame pixel blocks is greater than the long frame number threshold, the counter time+1, if time<=10, re-judge S2 in the next frame, if the counter is greater than time>10, execute S9;

[0089] S9, determine whether to use the linear wide dynamic algorithm or the sensor wide dynamic algorithm:

[0090] The specific method of step S9 is:

[0091] If the following conditions are satisfied: Num_Long>Th_Long and Num_Short>Th_Short, use the sensor wide dynamic algorithm and execute S10; if the following conditions are satisfied: Num_Long>Th_Long and Num_Short≦Th_Short, use the linear wide dynamic algorithm and execute S11.

[0092] Among them, Num_Long: the number of pure long frame pixel blocks; Num_Short: the number of pure short frame pixel blocks; Th_Long: the long frame number threshold; Th_Short: the short frame number threshold;

[0093] In this embodiment, if the number of pure long frame pixel blocks is greater than the long frame number threshold, it indicates that there is a large bright area in the picture. If the number of pure short frame pixel blocks is greater than the short frame number threshold, it indicates that there is a large dark area in the picture. When there is no large bright area, it does not enter the wide dynamic range. When there is only a large bright area, it is suitable to enter the linear wide dynamic range. When there are both large bright areas and large dark areas, it is suitable to enter the sensor wide dynamic range.

[0094] S10, calculating a control strength value of the sensor wide dynamic algorithm according to the area and brightness difference between the dark area and the bright area in the current image, where the control strength value is used to measure the strength of the sensor wide dynamic algorithm's image control capability.

[0095] The calculation formula of the sensor wide dynamic algorithm control intensity value Hdr_Intensity in step S10 is as follows:

[0096] Hdr_Intensity_sensor=(Num_Long+Num_Short-Floor_Limit_long_short) / Top_Limit_long_short*255;

[0097] Among them, Num_Long is the number of pure long frame pixel blocks; Num_Short is the number of pure short frame pixel blocks; Floor_Limit_long_short is the lower limit of the reference long and short frame number; Top_Limit_long_short is the upper limit of the reference long and short frame number; the lower limit of the reference long and short frame number and the upper limit of the reference long and short frame number are preset values ​​in the wide dynamic processing module.

[0098] S11, calculating a control strength value of the linear wide dynamic algorithm according to the area of ​​the dark area and the brightness difference in the current image, where the control strength value is used to measure the strength of the linear wide dynamic algorithm's image control capability.

[0099] The calculation formula of the linear wide dynamic control intensity Hdr_Intensity in step S11 is as follows:

[0100] Hdr_Intensity_linear=(Num_Long-Floor_Limit_long) / Top_Limit_log*255

[0101] Among them, Num_Long is the number of pure long frame pixel blocks; Floor_Limit_long is the lower limit of the reference long frame number; Top_Limit_long is the upper limit of the reference long frame number; the lower limit of the reference long and short frame number and the upper limit of the reference long and short frame number are preset values ​​in the wide dynamic processing module.

[0102] In this embodiment, as shown in FIG. 4( a ), the wide dynamic range is turned off and the current scene is a wide dynamic range. When the wide dynamic range is turned off, the indoor scene is darker and the detail area is not bright enough, resulting in blurriness. The outdoor scene is overexposed and the picture is distorted.

[0103] As shown in Figure 4(b), the linear wide dynamic range is turned on and the intensity is low.

[0104] As shown in Figure 4(c), the linear wide dynamic range is turned on and the intensity is high.

[0105] When the linear wide dynamic algorithm is turned on, the indoor brightness is improved, the details in the dark area are visible, and the effect becomes more obvious as the wide dynamic intensity increases. However, the outdoor scene is still overexposed and the picture is distorted.

[0106] As shown in Figure 4(d), the sensor wide dynamic range is turned on and the intensity is low.

[0107] As shown in Figure 4(e), the sensor wide dynamic range is turned on and the intensity is high.

[0108] When sensor wide dynamic is turned on, the indoor brightness is improved, the details in the dark area are visible, and the effect becomes more obvious as the wide dynamic intensity increases. The outdoor overexposure problem is eliminated and the outdoor details are visible. Currently, the sensor wide dynamic is the best.

[0109] It should be emphasized that the embodiments of the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation modes. Any other implementation modes derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. An automatic wide dynamic control method for security monitoring equipment, characterized in that: The following steps are involved: S1. Set the time filter counter time, and add time filter before all mode switching operations; S2, obtaining the statistical information of the automatic exposure module AE of the current frame, and determining whether there is a difference between the statistical information of the current frame and the statistical information of the previous frame; S3, determine whether the device has PTZ three-axis motion; S4, determining whether the device meets the requirements of wide dynamic mode picture brightness; S5, obtaining the brightness of each pixel block of the current frame AE statistical information to obtain a pixel block brightness histogram; S6, counting the number of pure long-frame pixel blocks and the number of pure short-frame pixel blocks in the pixel block brightness histogram; S7. Setting a long frame number threshold and a short frame number threshold according to experience values; S8, determining the relationship between the number of pure long frame pixel blocks and the long frame number threshold; S9. Determine whether to use the linear wide dynamic algorithm or the sensor wide dynamic algorithm: S10, calculating a control strength value of the sensor wide dynamic algorithm according to the area and brightness difference between the dark area and the bright area in the current image, where the control strength value is used to measure the strength of the sensor wide dynamic algorithm's image control capability; S11, calculating a control strength value of the linear wide dynamic algorithm according to the area of ​​the dark area and the brightness difference in the current image, where the control strength value is used to measure the strength of the linear wide dynamic algorithm's image control capability.

2. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step 1 is: Set the time filter counter time, using the "add one subtract one" method. When mode switching is required, it is not performed immediately, but replaced by the operation of adding one to the relevant counter. The mode switching is performed only when the counter value reaches a certain value. If the judgment result changes during the process, the counter is reduced by one.

3. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S2 is: Get the statistical information of the automatic exposure module AE of the current frame, collect the overall brightness of the current picture, the ambient brightness, and the overall RGB pixel ratio of the current picture. If there is no statistical information of the previous frame, directly perform S3 judgment; If there is statistical information of the previous frame, it is judged with the statistical information of the previous frame. When the above statistical information has not changed significantly, it is considered that the current scene is stable, and directly enter the next frame to re-judge S2, and counter time-1, the minimum time is 0; and when one or more of the above parameters have changed significantly, it is considered that the scene has changed, and continue to S3.

4. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S3 is: When the device undergoes ptz three-axis motion, the counter time is reset, the AE statistical information cache of the previous frame is cleared, the algorithm judgment is suspended, and the wide dynamic state and intensity before the motion are maintained until the motion stops; after the device stops moving, S2 is re-judged; if the device does not undergo ptz three-axis motion, continue with S4.

5. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S4 is: When in wide dynamic mode, when the overall brightness value of the AE statistical information is greater than the set over-brightness threshold or lower than the over-darkness threshold, the wide dynamic mode should be exited and the counter time should be reset. If it is not currently in wide dynamic mode, proceed to S5.

6. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S5 is: The brightness of each pixel block of the current frame AE statistical information is obtained to obtain a pixel block brightness matrix, and a pixel block brightness histogram is obtained after a spatial filtering operation is performed on the pixel block brightness matrix.

7. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S6 is: Obtain the short frame threshold and long frame threshold in the wide dynamic processing module and compare them with the pixel block brightness histogram obtained from the AE statistical information: in the pixel block brightness histogram, the pixel blocks less than the short frame threshold are regarded as pure short frame pixel blocks, the pixel blocks greater than the long frame threshold are regarded as pure long frame pixel blocks, and the pixel blocks greater than the short frame threshold and less than the long frame threshold are regarded as long-short frame fusion pixel blocks; count the number of pure long frame pixel blocks and the number of pure short frame pixel blocks in the pixel block brightness histogram.

8. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S8 is: If the number of pure long frame pixel blocks is less than the long frame number threshold, the counter time-1, and re-judge S2 in the next frame; when the number of pure long frame pixel blocks is greater than the long frame number threshold, the counter time+1, if time<=10, re-judge S2 in the next frame, if the counter is greater than time>10, execute S9.

9. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The specific method of step S9 is: If the following conditions are satisfied: Num_Long>Th_Long and Num_Short>Th_Short, use the sensor wide dynamic algorithm and execute S10; if the following conditions are satisfied: Num_Long>Th_Long and Num_Short≦Th_Short, use the linear wide dynamic algorithm and execute S11. Among them, Num_Long: the number of pure long frame pixel blocks; Num_Short: the number of pure short frame pixel blocks; Th_Long: the long frame number threshold; Th_Short: the short frame number threshold.

10. The automatic wide dynamic control method for security monitoring equipment according to claim 1, characterized in that: The calculation formula of the sensor wide dynamic algorithm control intensity value Hdr_Intensity in step S10 is as follows: Hdr_Intensity_sensor=(Num_Long+Num_Short-Floor_Limit_long_short) / Top_Limit_long_short*255; Among them, Num_Long is the number of pure long frame pixel blocks; Num_Short is the number of pure short frame pixel blocks; Floor_Limit_long_short is the lower limit of the reference long and short frame number; Top_Limit_long_short is the upper limit of the reference long and short frame number; the lower limit of the reference long and short frame number and the upper limit of the reference long and short frame number are preset values ​​in the wide dynamic processing module; The calculation formula of the linear wide dynamic control intensity Hdr_Intensity in step S11 is as follows: Hdr_Intensity_linear=(Num_Long-Floor_Limit_long) / Top_Limit_log*255 Among them, Num_Long is the number of pure long frame pixel blocks; Floor_Limit_long is the lower limit of the reference long frame number; Top_Limit_long is the upper limit of the reference long frame number; the lower limit of the reference long and short frame number and the upper limit of the reference long and short frame number are preset values ​​in the wide dynamic processing module.

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