Researches Of H.264 Video Steganography Based On Two DCT4×4 Blocks

With the security of Network becoming remarkable and the invention of new video compression standard, video steganography based on H.264 has become a hot spot for researchers. A lot of theories and algorithms about video steganography have been proposed by industry, but these algorithms, more or less, have some defects, for instance, big impact on quality of videos, low security, etc. So, research on H.264 video steganography is still significant.Proposed a steganographic algorithm based on two quantized DCT4×4 blocks. When embedding secret information, choose two DCT4×4 blocks that meeting certain conditions, each block has 15 AC coefficients that can be treated as a vector, and then modulate coefficients to make the remainder dividing by 8 of the product of these two vectors equal the decimal value of three bits of secret information. When extracting secret information, calculate the product of two DCT4×4 blocks that meet the same conditions, remainder of the product divided by 8 is the secret information to be extracted.Analyzed the impact of 15 AC coefficients on the growth of bit rate and PSNR(Peak Signal to Noise Ratio) for videos. By analyzing large amount of experiment data, the impact factor of 15 AC coefficients on bit rate and PSNR of videos could be got. Error is no more than 10% when estimating the impact on the quality of videos of each AC coefficients with different modified magnitude.Got the best composed impact factor of bit rate and PSNR. By applying the best impact factor to the basic steganographic algorithm based on two quantized DCT4×4 blocks, the optimal resolution which has the least damage to embedded videos could be got.1Experiments have shown that the algorithm has little impact on videos compared with the same sort of steganograhpic method. And the impact factor is universal, if applying the impact factor to the algorithm, both of the PSNR and growth of bit rate could be improved.