On Distortion Measures Associated to Random Desynchronization Attacks

摘要

Desynchronization attacks based on fine resampling of a watermarked signal can be very effective from the point of view of degrading decoding performance. Nevertheless, the actual perceptual impact brought about by these attacks has not been considered in enough depth in previous research. In this work, we investigate geometric distortion measures which aim at being simultaneously general, related to human perception, and easy to compute in stochastic contexts. Our approach is based on combining the stochastic characterization of the sampling grid jitter applied by the attacker with empirically relevant perceptual measures. Using this procedure, we show that the variance of the sampling grid, which is a customary geometric distortion measure, has to be weighted in order to carry more accurate perceptual meaning. Indeed, the spectral characteristics of the geometric jitter signal have to be relevant from a perceptual point of view, as intuitively seen when comparing constant shift resampling and white jitter resampling. Finally, as the geometric jitter signal does not describe in full the resampled signal, we investigate more accurate approaches to producing a geometric distortion measure that takes into account the amplitude modifications due to resampling.