左力文,骆挺,蒋刚毅,高巍,胡天佑(宁波大学信息科学与工程学院, 宁波 315211;宁波大学科学技术学院, 宁波 315211)
目的 数字视频通常经过压缩后传输，结合视频编码标准嵌入秘密信息是视频信息隐藏的主流技术。然而，现有基于HEVC（high-efficiency video coding）的视频信息隐藏技术存在码率增长过快、视频质量下降等问题。针对以上问题，提出结合恰可察觉编码失真模型（JNCD）的HEVC大容量信息隐藏方法。方法 JNCD模型是一种面向HEVC视频编码的视觉感知模型。该模型充分考虑编码过程的模糊和块效应，有效去除视频感知冗余，在相同码率下可获得更高的主观感知质量。结合JNCD模型，调节I帧中编码单元（CU）的最优量化参数（QP）值，并利用基于方向调整（EMD）算法嵌入秘密信息，进一步增加信息隐藏容量。为了提高信息的安全性，用密钥对秘密信息进行置乱加密处理，在解码端只有持有该密钥的用户才能正确解密，获得秘密信息。结果 实验使用HEVC参考软件HM16.0，选取分辨率不同的序列进行测试。结果表明，秘密信息嵌入后，视频测试序列的PSNR平均值为41.16 dB，与现有的信息隐藏方法相比，不仅保持较好的主观和客观视频质量，而且信息隐藏容量平均提升2倍左右。结论 采用本方法在保证原视频图像的质量的情况下，能够有效增加信息隐藏的容量，并能够一定程度阻止码率增长，符合信息隐藏的不可见性、安全性和实时性要求。
Large-capacity information hiding method for HEVC based on just noticeable coding distortion
Zuo Liwen,Luo Ting,Jiang Gangyi,Gao Wei,Hu Tianyou(School of Information Science and Engineering, Ningbo University, Ningbo 315211, China;College of Science and Technology, Ningbo University, Ningbo 315211, China)
Objective Information hiding technology can effectively guarantee information security by concealing secret information imperceptibly in digital media through the redundancy of multimedia data and human eye masking characteristics. The combination of a video coding process and standard is a critical approach to video information hiding technology because digital video is commonly stored and transmitted in compressed form. The next-generation high-efficiency video coding (HEVC) standard plays an important role in high-definition video applications due to its high encoding efficiency. Consequently, the information hiding method for HEVC has a theoretical value and practical significance. However, existing HEVC information hiding technology exhibits deficiencies, such as the rapid increase in bit rate and the degradation of video quality. Accordingly, a new large-capacity information hiding method for HEVC based on the just noticeable coding distortion (JNCD) model is proposed. Method The JNCD model is presented as a type of visual perception model for HEVC by considering the blurring and block distortion of the coding process. This model can effectively remove human perception redundancy and achieve higher subjective perceptual quality at the same bit rate. The optimal quantization parameter (QP) value for each coding unit is computed by using this model. An exploiting modification direction algorithm is utilized to adjust the optimal QP values and embed secret information. The algorithm maximizes the modified direction, thereby increasing embedding capacity from the usual four states to five states, in which a maximum of one bit data is changed for the two consecutive coded QP values. The extraction of information can be performed directly without referring to the original video, which can be satisfied with real-time and blind extraction performance. Result The HEVC reference software HM16.0 is used, and five sequences with different resolutions are tested. After the secret information is embedded, experimental results show that the average PSNR of the video test sequence is 41.16 dB. Unlike existing information hiding methods, our approach does not only maintain good subjective and objective video quality, but also increases information hiding capacity by approximately 2 times, on average. Conclusion The proposed method can effectively increase embedding capacity, prevent bit rate increases, and ensure the quality of the original video image. A secret key is used to scramble and encrypt the secret information, which increases information security. Only the user who holds the key can decrypt and obtain the secret information at the decoding side. Embedding the secret information into the frame with the highest priority prevents information loss caused by packet loss and dropped frames in the channel transmission. This process also effectively guarantees video perception quality. The proposed method fulfills the invisibility, security, and real-time requirements of information hiding, thereby making it suitable for military organizations, financial institutions, commercial markets, and other secure communication fields.