Robust blind extracting audio watermarking based on quadrature Phase Shift Keying and Improved Spread Spectrum

In this paper, a robust blind extracting audio watermarking scheme based on Improved Spread Spectrum (ISS) and Quadrature Phase Shift Keying (QPSK) is proposed. The frequency of direct spread spectrum sequence signal is reduced to limit its bandwidth, and then modulated to a higher frequency band with QPSK so as to lower the influence of watermarking to listener, meanwhile improve signal-noise ratio (SNR). The amplitude of watermarking to be embedded is determined by the correlation of spread spectrum (SS) sequence and the high frequency part of host audio signal. Experimental results show that the proposed scheme is more robust and transparent than traditional ISS watermarking.