Recently, a friend from outside the security circle asked the small editor, video monitoring video has been tampered with the possibility? Therefore, dongguan yongxu security editor carefully considered this question...

Since video is also composed of pictures, the average 1 second is 25~30 frames (zhang). In theory, it is possible to modify video by modifying some key pictures in video. At the same time, small make up also consult a lot of data, found that the method is mainly used in video tampering with digital video processing technology, specific methods include heavy projection (use cameras on the existing video recording), frame (frame insert, delete and frame reordering frame), the super-resolution reconstruction, the video object based video object (including add, delete, and position).

So the question is, since surveillance video has the possibility of forgery and tampering, how can we tell?

Natural law test.

Monitoring video's real scenes is a natural order of natural law, including gravity and the movement of light from the sun. Gravity is mainly used to judge whether the motion trajectory of the object in video is reasonable to determine whether the monitoring of video is falsified or altered. The movement of the sun's rays are used to determine whether light and the object in the surveillance video projection is reasonable, and according to the sun's rays irradiation direction judgment in surveillance video shows that time is correct, the main use of light and shadow, depth and shelter and other information. For example, we can use the monitoring video in the last few days to compare and analyze whether the light projection in the time period of video monitoring is consistent, and of course, we should also consider the weather changes.

Different imaging equipment, overlapping scene verification method.

If there are two imaging equipment at the scene have overlap, can take advantage of these two imaging equipment to record the scene than surveillance video overlap, if there are abnormal illustrates one of the surveillance video is forged and tampered with.

If the two imaging equipment recorded surveillance video are forged and tampered with so the different imaging equipment, overlapping scene validation method is invalid, but it can make the two imaging equipment to record the monitoring video in overlapping scenes and completely at the same time, several obviously need higher technology. If there are multiple imaging devices with overlapping scenes, the value of this method is more valuable.

Different imaging equipment, adjacent field analysis.

Sometimes site is equipped with two or more than two imaging equipment, the equipment not to overlap the scenes, but their filming scenes with adjacent to each other, because of this, judge can through the comparison analysis of these scenarios to infer if surveillance video was forged and tampered with. For example, judging by the consistency of moving objects such as cars, animals, etc.

Field object change inference method.

The object in the scene appears or disappears with its motion track. If an object on the scene suddenly appears and disappears, it can be inferred that monitoring video is abnormal.

Monitor video data analysis.

A complete, unmodified monitoring of video's underlying data (mainly the header and tail information of video) is completely compact-coded. The falsification and tampering process that monitors video inevitably leaves some traces, such as a change in video statistical properties. These features include the characteristics of image evidence such as ambiguity, block effect and similarity between image regions, and the characteristics of video such as GOP periodicity. Through the analysis of the monitoring video underlying data testing, analysis of the video end whether information and video information there are discrepancies, thus analysis of surveillance video data is been tampered with, at present, this kind of method to paste, MPEG compression and double frame manipulation behavior identification such as the operation.

Monitoring video data is large, and testing is time-consuming. Even a small piece of monitoring video requires a very large amount of testing.

If the perpetrators to use forged and tampered with the surveillance video to conceal its purpose, its necessary to monitor video technology in-depth study and verification, the forged and tampered with monitoring video technology will also may be very advanced.