| With the rise of the Internet and reductions of the cost of video editing, a growing number of illegal video files have being widely spreading, which affects social harmony and stability seriously. So we need to resolve the legality of the digital video urgently.Digital video forensics is born for this, with the help of professional video forensics technology, we can identify prohibited content in pirated video or determine the authenticity and originality of video reliably and efficiently. At present, the technology has become a hot topic in the field of multimedia security. There are mainly three methods about video forensics, digital signatures, video watermark and video fingerprinting technology. Wherein the first two methods require pretreatment by video provider, such as extraction or embedded digest authentication information.Meanwhile, the actual forensics will encounter situations when the video file has been deleted, so that we can not often get or restore the complete video files, which brings enormous difficulties for forensic work.This study is actually for the fragmented video files existed in the disk. Combined with traditional methods, the paper made the following four studies。Firstly,research the Ex FAT file system in order to acquire fragmentations of videos. Secondly, analyse video formats and H.264 compression standard, and come up with an algorithm to search the H.264 stream from piecemeal. Thirdly, restore images of IDR frame by reconstructing sequence parameter set(SPS) and picture parameter set(SPS), which has been proved in practice. Finally, to compact with video steganography technology, we propose two kinds of information hiding detection algorithm with the consideration of characteristics of video fragments, they all achieve great results. |
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