Estimation of the primary quantization parameter in MPEG videos

The advanced technology and sophisticated software have rendered audiovisual content exposed to forgery, inspiring the emergence of multimedia forensic research. Since video tampering may involve double compression, the analysis of compression history is of significance. In this paper, we consider the processing chains of two compression steps and propose an algorithm that aims at identifying the quantization parameter used in the previous coding process. The method relies on the fact that characteristic footprints can be observed under different relationships between quantization parameters of consecutive compression operations. Features are extracted from both Discrete Cosine Transform (DCT) coefficients and their differential counterparts to capture the statistical disturbance. Experimental results demonstrate the effectiveness of our method.