# A Survey on Robust Video Watermarking Algorithms for Copyright Protection
## 5 Robust Watermarking Algorithms Based on Compressed Videos
### H.265-Based Watermarking Algorithms  
H.265, also called HEVC, was officially approved by ITU-T and ISO/IEC in 2013. It is the successor of H.264/AVC, and has better compression performance. It can transmit higher quality network video with limited bandwidth, and only needs half of the original bandwidth to play a video with same quality [89]. With the development and wide application of HEVC, video watermarking algorithms based on HEVC have become a hot research topic. [PERSON] et al. [90] used the motion information of the inter prediction frame adjacent to I frame to obtain the motion characteristics of I frame. The watermark is embedded by modifying the number of nonzero transform coefficients (NNZ) difference of 4 \(\times\) 4 luma blocks in consecutive intra prediction frames. Due to watermark embedding, drift error will occur. To eliminate the drift error, many related algorithms have been proposed one after another [91; 92; 93; 94; 95; 96]. On the basis of a past paper [90], [PERSON] et al. [91] analyzed the intra prediction process of HEVC standard, and embedded the watermark into pixels that were not involved in the prediction process. In this way, the drift error caused by watermark embedding can be resisted. In another past paper [92], to avoid intra frame drift errors, the direction conditions of intra prediction were given first, and the information was embedded into multi-coefficients in luminance components of 4 \(\times\) 4 DCT blocks of selected frames which can satisfy the condition. Based [92], [PERSON] et al. gave three conditions of intra prediction direction and multi-coefficients in [93], and the message was embedded into multi-coefficients in luminance components of 4 \(\times\) 4 discrete sine transform (DST) blocks of selected frames satisfying the specific condition. [PERSON] et al. [94] selected 4 \(\times\) 4 texture blocks in luma prediction unit (PU) for embedding based on the HVS. The watermark is adaptively embedded into quantized DST (QDST) coefficients in 4 \(\times\) 4 luma PU using the sum invariability method. [PERSON] et al. [95] proposed a first data hiding algorithm for HEVC intra-coded frames based on DCT/DST. The characteristics of block DCT and DST coefficients are explored to determine the positions of transform coefficients that can be perturbed and will not propagate errors to adjacent blocks. [PERSON] et al. [96] proposed a robust HEVC watermarking algorithm based on repetition-BCH syndrome code technology, which can not only resist distortion drift but also preserve the extracted watermark with good quality. The watermark is encoded by repetition-BCH code first, and then embedded into the quantized DCT/DST residual coefficients of transform units (TU) within the different size of TUs of I frames. After studying the spatiotemporal characteristics of the HEVC encoded video, [PERSON] and [PERSON] [97] embedded the watermark invisibly into low-frequency nonzero quantized AC coefficients in 4 \(\times\) 4 blocks of I frames, which can minimize the synchronization error. In addition, a framework composed of public key and private key is presented to enhance the security. To obtain better perceptual quality, they embedded the watermark into P frames invisibly [98]. Based on the analysis of spatiotemporal characteristics of compressed video, suitable blocks for embedding can be located, which can further minimize the quality degradation and improve the robustness. [PERSON] et al. [99] proposed a separable reversible