Digital video watermarking in P-frames

Most video watermarking algorithms embed the watermark in I-frames, which are essential for the video signal, but refrain from embedding anything in P- and B-frames that are highly compressed by motion compensation. Furthermore, these algorithms do not take advantage of temporal masking in subjective perception of the video. In this paper, we explore the capacity of P-frames and the temporal masking effect in the video signal. The challenge in embedding watermark bits ill P-frames is that the video bit rate call increase significantly. Thus, we choose to embed watermark bits only in nonzero AC residuals in P-frames. Changing zero-valued coefficients to nonzero values can significantly increase the video bit rate because H.264 (and earlier coders as well) uses run length codes. We. show that avoiding zero-valued coefficients significantly reduces the percentage increase in the compressed video bit rate and makes watermark embedding in P-frames practical. Since the nonzero residuals in P-frames correspond to non-flat areas that are in motion., temporal and texture masking will be exploited at the same time. This is confirmed by showing the resemblance of the plots of the number of nonzero residuals in each frame to motion intensity plots.