The basic principle of watermarking is the addition of the watermark signal to the host data that we wish to watermark. The addition is taking place in a way that the watermark signal is discreet and secure among the rest signals. Its retrieval, either partial or complete from the rest of signals, must be also possible only by using a secret key. In this chapter, we are going to deal with the digital video watermarking. First, we will name its applications, requirements, and the most important trends, then we will describe some of the most significant techniques of the specific process.
Requirements Of Video Watermarking
A video watermarking technique must fulfil some requirements. We mention below the three most principal requirements for video watermarking. The first is that the technique above should be robust to non hostile video processing. The second is that it should be robust to collusions and the third one is that it should be performed in real-time.
The robustness of the digital watermarking is always estimated in regard to the survival of the watermark after the implementation of the attacks. In the environment of digital watermarking the future value of attacks that take place in the video is multiple. Many different, non hostile attacks in video are in fact likely to happen. The term non-hostile refers to those attacks where for example, the provider of the content processes a bit of information from his digital data for the most efficient handling of his sources. Afterwards, we name any procedures that can lead to non hostile attacks: the addition of noise during the transmission through a wireless network, the conversion of a digital to analog or analog to digital signal, the gamma correction in order to increase the contrast, the changes across display formats (4/3, 16/9, 2.11/1), the changes of spatial resolution (NTSC, PAL, SECAM), the attack by a handheld camera, the changes in frame rate, the video editing process (cut-and-splice or cut-insert-splice) and the overlay with a chart (logos and labels).