How pixel manipulation of forensic watermarks protects premium OTT videos against piracy

Over-the-top (OTT) platforms use digital rights management (DRM) technology to control piracy and manager subscriptions across devices. But, they should be prepared for the eventuality of sophisticated piracy attacks from global hackers’ networks. The piracy industry of premium Hollywood and sporting content is a billion-dollar industry. OTT platforms combine DRM video protection with forensic/video watermarking to track pirated content and enforce legal costs on the user and networks responsible for piracy.

Watermark generation is the first step in protecting a video file with forensic watermarking technology. For the watermark to be secure and tamper proof, the developer needs to scramble a secret key randomly with watermark information. The effectiveness of a forensic watermark depends on how the watermark information, which may contain details of the subscriber, device, and other parameters, is rendered meaningless during preprocessing.

In one such method, called cat map, the preprocessing involves a combination of stretching, compressing, folding, and splicing. The transform process has a periodicity that can be used to regenerate the original frame when applied continuously. The principle behind forensic watermarking is to target pixels in each frame in such a way that they are displaced from their original position according to a set formula, leading to frame encryption. The developer can either change the value of each pixel in a frame, called the substitution scheme, or shuffle the pixel value, which is called the permutation scheme.

The cat map watermark-generation scheme is spatial in character and is conventionally applied to high-resolution images that require copyright protection. However, with the emergence of OTT platforms that play premium video content, this method of video watermarking is applied to video files as well after dividing video streams into individual frames. Here, the most important aspect is the transparency of the watermark, since a weak watermark can disturb the viewing experience of the legitimate user.

Once a robust and scrambled watermark has been generated by displacing pixels according to a set equation, the developer uses a frequency-based approach to embed it in individual frames. The robustness of the embedding process protects the copyright information contained in watermarks against manipulation and is used to reverse the process of embedding and detect copyright violations.