Two-band amplitude scale estimation for quantization-based watermarking

Quantization-based watermarking schemes comprise a class of watermarking schemes that achieves channel capacity in terms of additive noise attacks. Unfortunately, quantization-based watermarking schemes are not robust against linear time invariant (LTI) filtering attacks. In this paper we concentrate on amplitude scaling of a multi-band system. First we derive the probability density function (PDF) of the attacked data. Second, using a simplified approximation of the PDF model, we derive a maximum likelihood (ML) procedure for estimating two-band amplitude scaling factor. Finally, experiments are performed with real audio signals showing the good performance of the proposed estimation technique under realistic conditions.