Audio Watermarking Using QIM on Wavelet Packet Coefficients

In this paper, we propose an audio watermarking method that is based on wavelet packet transform (DWPT) coefficients. One bit of watermark codes is embedded into the power ratio (quantization index) of a pair of DWPT coefficients by quantization index modulation (QIM). The encoded pair is selected from the higher harmonic regions of the most powerful coefficient in a DWPT. By using such a criterion to select the watermarked region, we can expect to deal with the conflict of the length of analyzing between the sides of embedding watermarks and detecting watermarks. Multiple bits are embedded into the several pairs that are selected from the coefficient series of a DWPT. If the selected pair was not expected to detect the power ratio, the watermark bit is not embedded into such a pair. This realizes various bit rate embedding of watermark.