# MPEG and DA-AD Resilient DCT-Based Video Watermarking Using Adaptive Frame Selection
## 2 Background  
Digital-to-analog conversion is the process of transforming a signal from the digital to the analog domain. After this process, the receiver can receive digital information through an analog-to-digital conversion. When outputting this intermediate transmission channel or video, a problem called an analog-hole might be encountered. An analog hole (also known as an analog loophole) is the perceived fundamental and inevitable vulnerability inherent in copyright protection schemes for non-interactive works in digital format. Digital multimedia can be exploited to duplicate a copy-protected work that is ultimately reproduced through analog means [2]. Once digital content has been converted into a human-perceptible format, it is relatively simple to digitally recapture an analog copy in an unrestricted format, thereby fundamentally circumventing all protections on copyrighted digital distribution and reproduction.  
Digital watermarking provides robustness against analog hole piracy [2] when it is infeasible to protect original works of authorship through other protection techniques such as digital rights management (DRM). Owing to these characteristics, the application of digital watermarks as a technology in complementing DRM has been steadily receiving attention. A digital watermark is a technology that hides data in noise-resistant signals such as multimedia content. Many studies on watermarking technology applied to various contents have been conducted, such as watermarking based on neural networks [13], 3D meshes and prints [14; 15], and spherical panoramic images [16].  
Robust video watermarking methods based on various methodologies have been studied [17; 18; 19; 20; 21; 22] Robustness against non-hostile video processing must be ensured to achieve copyright protection in video distribution cases. To provide robustness of the embedding patterns against lossy compression, various watermarking domain and primitives have been adopted, including a contourlet transform and a principal component analysis [17], gradient magnitude similarity deviation [18], and a hyperchaotic Lorentz system [19]. [PERSON] et al. [23] proposed a significant frame selection and a quantization of the lifting wavelet transform coefficient difference based method for robust video watermarking. [PERSON] et al. [22] demonstrated that the dual tree-complex wavelet (DT CWT) domain is effective for achieving a high robustness. For enhancing the robustness against lossy video compression, [PERSON] et al. [21] used the coefficients of a contourlet transform to embed an encrypted watermark pattern using a singular value decomposition.  
In the case of video watermarking, a pattern embedded as a secret message should be retrieved after applying various non-hostile and common video processes [24]. Video editing, photometric attacks, and spatial and temporal shifts (or desynchronization) are included in non-hostile video processes [25]. Photometric attacks are a process for modifying the pixel intensities in a frame. Noise addition and DA-AD conversions belong to this category. Another common treatment involves applying gamma correction to increase the contrast. To reduce the storage and transmission requirements, content owners re-encode their digital videos to a different compression ratio using a video compression algorithm. Video compression algorithms are based on a lossy compression on spatial and temporal domains of the media, such that the loss of information induced easily alters the performance of the watermarking algorithm. Similarly, customers can choose from standard video formats such as MPEG-1, MPEG-2, or MPEG-4. Spatial filtering and inter-frame filtering also have to be considered. A spatial shift or desynchronization can occur with changes in the display and spatial resolution. Primarily, temporal desynchronization occurs because of changes in the frame rate. In addition, video editing includes various methods from video editing tools, such as fade-and-dissolve, copy-and-paste, and splicing.