# A Survey on Robust Video Watermarking Algorithms for Copyright Protection
## 5 Robust Watermarking Algorithms Based on Compressed Videos
### MPEG-Based Watermarking Algorithms  
MPEG is an expert group established jointly by the international organization for standardization (ISO) and the international electrotechnical commission (IEC) in 1988 to develop standards for the encoding, decoding, and synchronization of television image data and audio data. The standards developed by this expert group are called MPEG series standards, and different versions of the standards show different uses and visual quality, which have played a revolutionary role in promoting the development of multimedia communication. Next, MPEG-2 and MPEG-4 standards will be introduced, and several video watermarking algorithms based on them will be summarized. MPEG-2 is a lossy compression standard for video and audio organized and formulated by MPEG in 1994. It is a compression scheme for standard digital television and high-definition TV under various applications, and its coding rate ranges from 3 Mbit/s to 100 Mbit/s [70]. To reduce the computational complexity, many video watermarking algorithms in the compressed domain only need partial decoding in watermark embedding process [71; 72; 73]. To resist scaling attacks, [PERSON] and [PERSON] [71] proposed a MPEG-2 video watermarking algorithm based on shadow-frame generation in the compressed domain combined with DCT transform. In the watermark embedding phase, only partial decoding of MPEG-2 video and conversion between full DCT and block DCT are needed, and in the watermark extraction process, through the use of turbo codes, the BER can be reduced. On the basis of the in-depth analysis of video encoding formats under MPEG-2 standard, [PERSON] et al. [72] proposed a video watermarking algorithm based on DC coefficients. This algorithm also does not need to decode all the video data, and it does inverse DCT after the inverse quantization process. The watermark information is embedded into the last DC coefficient of the last macroblock of each slice in luminance component, which can solve the blocking artifacts. In a past paper [73], the watermark image was decomposed into eight binary images, and every image was embedded into different scenes of the video sequence. A suitable set of DCT coefficients partially decoded from compressed videos is found by combining with a visual mask based on local image features. The watermark is embedded by modifying these selected DCT coefficients, which can improve the image fidelity. In another past paper [74], a watermark system was designed from the architecture level combining with data compression, which has configurable spatial and frequency domain embedding and very large scale integrated circuit (VLSI) architecture. In yet another past paper [75], a new video watermarking method, based on empirical principal component analysis (PCA) decoding, was proposed. The intensity of embedding factors is determined according to the energy of high-frequency sub-bands and visual saliency. Decoding is performed through the comparison among elements of first principal component generated by empirical PCA, and the watermark is embedded in LL sub-bands adaptively. MPEG-4 is a multimedia communication standard with a wide range of data rates established by MPEG in 1998. Its code rate covers a range of 5 kbit/s to 5 Mbit/s, and its aim is to support a variety of multimedia applications. [PERSON] et al. [76] embedded the watermark into video objects by applying some predefined relationships between pairs of quantized DCT coefficients, which were in luminance blocks of pseudo-randomly selected macroblocks (MBs). Watermarks are equallyembedded in intra and inter MBs, and the masking method is also used to limit the visual artifacts in watermarked video object planes (VOPs). [PERSON] and [PERSON] [77] proposed a watermarking algorithm based on MPEG-4 fine granularity scalability (FGS) video codec, which embedded watermarks during the encoding process.