CN1245018C - Method for eliminating scintilltion of moving picture - Google Patents

Abstract

The invention relates to a method for eliminating flicker in a moving picture, in particular to a method for eliminating rolling dark stripes that appear when the parameter setting of the camera device is not compatible with the external light source during the digital image display process. The purpose proposed by the present invention is achieved by the following scheme, a method for eliminating screen flicker in a digital image display process: firstly, switch the different parameter setting states of the camera device in turn and judge whether there are dark stripes on the image; then, according to the camera The device can determine the type of light source when there are rolling dark stripes under different parameter settings; finally, modify the parameters of the camera to adapt to the ambient light source to eliminate the rolling dark stripes on the image. The method of the present invention is mainly completed by a microcomputer, does not require too much manual operation, has high judgment accuracy, and has a small amount of calculation.

Description

How to Eliminate Flicker in Motion Picture

technical field

The invention relates to a method for eliminating flicker in a moving picture, in particular to a method for eliminating rolling dark stripes that appear when the parameter setting of the camera device is not compatible with the external light source during the digital image display process.

Background technique

When the digital camera device is working, in order to adapt to artificial light sources of different frequencies and outdoor natural light, some parameters of the camera device must be set accordingly, and one of the more important parameters is the automatic exposure time of the camera device. When the digital camera is working, it always adjusts the exposure time continuously according to the light and shade changes of the surrounding environment. For unused ambient light sources, the initial value of the exposure time and the step size of each adjustment will be different. However, in the process of actual use, there is often a mismatch between the parameter settings of the camera device and the actual ambient light source, and flickering of the picture will occur accordingly.

For example: under a light source driven by 50 Hz alternating current, the exposure time of the camera should always be an integer multiple of 0.01 second. The parameter setting of the camera device may be in the setting state of 60Hz or outdoor natural light. At this time, the exposure time is not an integer multiple of 0.01 second, so vertical scrolling dark stripes will appear on the image captured by the camera device. Will seriously affect the image quality. Similarly, under a 60Hz light source, the flickering period of the light source should be 1/120 second, so the automatic exposure time of the camera device should be an integer multiple of 1/120 second. But if the parameters of the camera device are set under 50Hz light source or outdoor natural light at this time, the actual exposure time is not an integral multiple of 1/120 second, and vertical scrolling will also appear on the displayed image of dark stripes.

In addition, in some cases, the dark stripes are very weak, and it is difficult for the user to judge with the naked eye. Under the operating standard that requires high image quality, this situation is very annoying.

The object of the present invention is to propose a method to avoid the above situation, to judge and detect the external light source when taking pictures, and then to select the appropriate shooting parameter settings, so as to effectively eliminate the flickering of the picture.

Contents of the invention

When the parameter settings of the camera do not match the actual ambient light source, rolling dark stripes will appear on the image captured by the camera. At this time, for a certain row of pixels, there may be obvious light and dark changes between two consecutive frames. , so it can be judged whether there are dark stripes on the image according to the light and shade changes of a row of pixels between two frames. However, if only one row of pixels is taken for judgment, the noise on the image and the shake of the camera will seriously affect the judgment accuracy, and it is possible that a certain row is in the dark stripes in the first frame, and when the second frame One line happened to be still in the dark stripes. Therefore, the purpose of judgment cannot be achieved. Therefore, if resources permit, it is recommended to take as many rows as possible for judgment to improve judgment accuracy.

The object proposed by the present invention is achieved by the following scheme, a method for eliminating screen flicker in a digital image display process:

First, switch the different parameter setting states of the camera device in turn and judge whether there are dark stripes on the image;

Then, the type of light source at this time is judged according to the rolling dark stripes appearing in the camera device under different parameter settings;

Finally, the parameters of the camera are modified to adapt to the ambient light source to remove dark streaks rolling across the image.

Wherein in the first step, the judgment whether there are dark stripes on the image is completed according to the following method:

First, intercept a frame of static image from a group of continuous images, and calculate the brightness value of each pixel, and then accumulate the brightness values of each pixel in each row to obtain a corresponding array one;

Second, take the second frame image and follow the same way as the above process to get another corresponding array two;

Then, subtract the corresponding row pixel brightness accumulation values in array 1 and array 2 one by one, and take the absolute value;

Finally, the above-mentioned absolute values are accumulated, and if the number is greater than the preset threshold, it can be judged that there are no scrolling dark stripes on the image captured by the camera under such an ambient light source; Rolling dark stripes.

In addition, the method of the present invention does not necessarily perform cumulative comparison calculations for each line of a frame of image, and can also extract a certain number of row pixels from the image to perform the comparison and judgment of the above method without reducing the judgment accuracy. to reduce the amount of computation.

Compared with the prior art, the present invention has the advantages of:

The method of the present invention is mainly completed by a microcomputer, does not require too much manual operation, has high judgment accuracy, and has a small amount of calculation. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings and non-specific embodiments.

Description of drawings

Figure 1 is the storage structure of 24bits uncompressed RGB image;

Figure 2 is the change period of the current at 50Hz alternating current;

Figure 3 is the flickering cycle of the light source at 50Hz alternating current;

Fig. 4 is a simple schematic block diagram of the flow process of the method of the present invention;

Fig. 5 is the flow chart of carrying out accumulation operation to the row pixel of image;

Fig. 6 is the flow chart that carries out comparison step module;

specific embodiment

In the following description, well-known functions or structures will not be described in detail to avoid unnecessary confusion with the content of the present invention.

The present invention analyzes the continuous digital images captured by the camera as an example.

The video stream captured from the camera is composed of frame-by-frame still images, and each frame of still images in this method is an uncompressed 24bits RGB image. The storage structure of image pixels is shown in Figure 1 (assuming the image size is M*N, unit: pixel):

The storage of pixels follows the principle of left-to-right and bottom-up. For a 24bits RGB image, the pixel in the lower left corner is stored at the front of the file data area, and the pixel in the upper right corner is stored at the end of the file. Each pixel occupies 3 bytes, and its B, G, and R channel values are stored sequentially, from 0 to 255. These three channels represent the three optical primary colors of blue, green, and red respectively, and their values represent their respective light intensity, among which 0 means no light, and 255 means the maximum light intensity. So (0,0,0) represents pure black and (255,255,255) represents pure white. For the convenience of file storage, each row of pixels in an RGB image occupies an integer multiple of 4 bytes. Insufficient part needs to add 0 at the end. For example, if there is a 24bits RGB image with a width of 6 pixels, two 0s should be added after the R value of the sixth pixel in each row (20-3*6=2).

In this method, the luminance value of a pixel is used for motion image judgment, and this value is created by RGB input signals by superimposing specific parts of the RGB signals together, the specific formula is as follows:

Y＝0.299R+0.587G+0.114B (1)

Using different alternating currents, artificial light sources of different frequencies will be generated. In actual operation, two kinds of artificial light sources of 50 Hz and 60 Hz are commonly used, so in the present invention, we use these two kinds of light sources and outdoor natural light sources as examples to describe the method in detail.

In the case of using 50Hz alternating current, the change period of the current is 0.02 seconds, as shown in Figure 2;

Then, the flickering period of the light source when driven by 50Hz alternating current is 0.01 second, as shown in FIG. 3 . For outdoor natural light sources, since the flickering period of natural light can be regarded as infinitesimal, there is no flickering period, so when the automatic exposure time is any value, dark stripes will not appear on the image.

Fig. 4 is a simple schematic block diagram of the flow process of the method of the present invention, here for convenience of explanation, we divide the above-mentioned method into several step modules to express:

A. Toggle settings module

The function of this part of the module is to switch the camera under the parameter settings under different light sources. Under different light sources, in order to obtain a clear picture, several parameters of the camera must be set to different values. For example, in this method, we judge the ambient light source according to the dark stripes rolling on the image, and this The generation of dark streaks is mainly caused by the exposure time, so here we will explain the difference in setting the exposure time under different light sources:

Camera settings for 50Hz light source: Exposure time should be an integer multiple of 1/100 second

Camera settings for 60Hz light source: the exposure time should be an integer multiple of 1/120 second

Camera settings in natural light: Although the exposure time can be arbitrary and there will be no dark stripes on the image, for convenience and judgment, the exposure time under natural light cannot be set to an integer multiple of 1/100 second or 1/120 second. This is because: under the light source of 50Hz, the setting of the camera is under the condition of outdoor natural light, but the exposure time at this time is exactly an integer multiple of 1/100 second, so although the setting of the camera is wrong, the captured image There are still no dark stripes on the surface, so it is impossible to judge.

When judging, different switching settings can be adopted in an order, for example: camera setting under outdoor natural light→camera setting under 50Hz light source→camera setting under 60Hz light source. That is to say, no matter what kind of light source the environment of the camera is in, first set the parameters of the camera to the natural light condition, and then execute the B (accumulation) and C (comparison) modules to process the image; after that, sequentially Set the parameters of the camera to 50Hz and 60Hz under natural light conditions, and also execute the B (accumulation) and C (comparison) modules to process the image.

B. Accumulation module

After switching the camera settings to a certain light source, it is necessary to start the accumulation operation of the row pixels of the image. The specific process is shown in Figure 5:

a. Intercept a frame of image, calculate the brightness value of each pixel according to the formula (1), then accumulate the brightness value of each row of pixels, and pay the value to the array ulPrj1

line1: Y1+Y2+...+Ym →ulPrj1[0]

line2: Y1+Y2+...+Ym →ulPrj1[1]

…

…

line n: Y1+Y2+...+Ym →ulPrj1[n]

b. Taking the second frame of image is similar to process a, but also accumulating the brightness value of each row, and paying the value to the array ulPrj2.

In actual calculation, the brightness accumulation value of each image row pixel contained in the array ulPrj may be relatively large, and the number of bits occupied is correspondingly large. According to this situation, these accumulation values can be proportionally reduced, then The threshold T1 also needs to be processed accordingly.

Of course, according to the present invention, it is not necessary to carry out cumulative comparison calculations for the N lines of the image in one frame, and it is also possible to extract a certain number of row pixels from the image for accumulation without reducing the judgment accuracy, for example, Draw one every other or draw one every two, etc., to reduce the amount of calculation.

C. Compare modules

After carrying out image line pixel luminance accumulation (B module), will compare (C module) to obtained array ulPrj1 and ulPrj2, Fig. 6 is the flow chart that carries out comparison step module:

a. Subtract the corresponding element values of the arrays ulPrj1 and ulPrj2 one by one, and take the absolute value:

V1＝|ulPrj1[1]-ulPrj2[1]|

V2＝|ulPrj1[2]-ulPrj2[2]|

…

…

Vn＝|ulPrj1[n]-ulPrj2[n]|

b. Then add up the obtained V value

nSum=V1+V2+...+Vn

c. If nSum is greater than the preset threshold T, it means that there are no scrolling dark stripes on the image captured by the camera under this ambient light source; otherwise, it means that there are rolling dark stripes on the image.

After the comparison (module C) is completed, the camera parameter settings can be switched to other light source conditions, and the operations of modules B and C can be repeated. Until the camera parameters are respectively set under outdoor natural light, 50Hz light source and 60Hz light source, the accumulation (B module) and comparison (C comparison) are completed.

D. Judgment module

Based on the results of the previous process, make a judgment, and finally find out whether the environment where the camera is located at this time is the artificial light source or the outdoor natural light source. For example: if the camera parameters are set at 50Hz, 60Hz and outdoor natural light, after judgment, there are no scrolling dark stripes on the image, then it can be concluded that the light source at this time is outdoor natural light; if the camera parameters are set at 50Hz If there are no dark stripes under light source conditions, but there are dark stripes under 60Hz and outdoor natural light conditions, then it can be concluded that the light source at this time is 50Hz artificial light source; if the camera parameters are set under 60Hz light source conditions, no dark stripes appear , and there are dark stripes under both 50Hz and outdoor natural light conditions, then it can be concluded that the light source at this time is a 60Hz artificial light source.

Then, according to the judgment result, module A is used again to switch the camera parameters to the ambient light source where the camera is located.

As mentioned above, this avoids rolling dark stripes on the image caused by the mismatch between the camera parameter settings and the actual light source. Obviously, the method described in the present invention is also fully applicable to other types of light sources. In addition, based on the idea of this method, some more complicated content can be realized in other fields.

Therefore, the method for eliminating flicker in the moving picture described in the present invention is not limited to the application listed in the description and the implementation, it can be applied to various fields suitable for the present invention, and can be used by those familiar with the field Additional advantages are readily realized and modifications are readily realized, so the invention is not limited to the specific details, representative apparatus and devices shown and described herein without departing from the spirit and scope of the general concept defined by the claims and equivalents. A graphical example of the description.

Claims (5)

1. A method for eliminating screen flicker in a digital image display process, comprising the steps: Step 1, switch the different parameter setting states of the camera device in turn and judge whether there are dark stripes on the image; Step 2, judging the type of light source at this time according to the rolling dark stripes appearing in the camera device under different parameter settings; Step 3, modify the parameters of the camera to adapt to the ambient light source to eliminate the rolling dark stripes on the image; Among them, the judgment of whether there are dark stripes in step 1 is completed according to the following steps: First, intercept a frame of static image from a group of continuous images, and calculate the brightness value of each pixel, and then accumulate the brightness values of each pixel in each row to obtain a corresponding array one; Second, take the second frame image and follow the same way as the above process to get another corresponding array two; Then, subtract the corresponding row pixel brightness accumulation values in array 1 and array 2 one by one, and take the absolute value; Finally, the above-mentioned absolute values are accumulated, and if the number is greater than the preset threshold, it can be judged that there are no scrolling dark stripes on the image captured by the camera under such an ambient light source; Rolling dark stripes. 2. the elimination method of picture flicker in the digital image display process according to claim 1, it is characterized in that, can carry out proportional reduction processing to the brightness accumulation value and the threshold value of each image row pixel contained in the array, then compare , to reduce the amount of computation. 3. The method for eliminating screen flicker in the digital image display process according to claim 1, characterized in that, it is not necessary to carry out cumulative comparison calculations for each row of a frame of image, and it can also be used without reducing the judgment accuracy. , extracting a certain number of rows of pixels from the image to perform the comparison and judgment of the above method, so as to reduce the amount of calculation. 4. according to claim from 1 to the elimination method of picture flicker in any described digital image display process in 3, it is characterized in that, the image file that this method uses is RGB file. 5. The method for eliminating screen flicker in any one of claims 1 to 3, wherein the applicable light source types of the method include 50Hz light source, 60Hz light source and outdoor natural light source.

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