Robust Audio Watermarking Based on Empirical Mode Decomposition and Group Differential Relations

Abstract

An audio watermarking technique using Complementary Ensemble Empirical Mode Decomposition and group differential relations of average absolute amplitudes of the last Intrinsic Mode Function (IMF) is proposed. By using group differential relations, the relationship with neighboring samples in the last IMF is well preserved, and near-imperceptibility can be achieved. Placing a watermark on low-frequency components, the last IMF, which is perceptually significant, therefore makes the watermark difficult to be removed. The embedding watermark, which is a logo image in our experiment, is processed by Arnold transformation, secret key encryption, and Bose-Chaudhuri-Hocquenghem coding to enhance robustness and security. Experimental results of the signal-to-noise ratio fit the recommendations of imperceptibility of the International Federation of the Phonographic Industry. The average Objective Difference Grade (an objective measure that correlates very well with subjective assessment) and subjective quality assessment were performed to evaluate the imperceptibility. Furthermore, our method accomplishes robustness under 13 different categories of attacks, including noise corruption, amplitude scaling, echo addition, resampling, re-quantization, low-pass filtering, MPEG-1 Audio Layer III compression, Digital-to-Analog/Analog-to-Digital conversion, cropping, time shift, zero thresholding, jittering, and combined attacks.