A blind audio watermarking technique based on a parametric quantization index modulation

In this paper, we propose an efficient transform-based blind audio watermarking technique by introducing a parametric quantization index modulation (QIM). Theoretical expressions for the signal to watermark ratio and probability of error are derived and then used in an optimization technique based on the Lagrange multipliers method to find the optimal values for the parameters of the parametric QIM that ensure the imperceptibility while maximizing the robustness under an additive white Gaussian noise (AWGN) attack. Moreover, a fast scheme for the implementation of the proposed watermarking technique is developed and an efficient procedure is suggested to find the interval for the best selection of the watermark embedding positions that provide a good trade-off between the effects of high and low pass filtering attacks. The parameters of the resulting optimal parametric QIM coupled with the embedding positions constitute a highly robust secret key for the proposed watermarking technique. We also carry out several experiments to show the usefulness of the theoretical analysis presented in the paper and compare the proposed technique with other existing QIM-based watermarking techniques by considering known attacks such as AWGN, re-quantization, resampling, low/high pass filtering, amplitude scaling and common lossy compressions.