Audio watermarking based on amplitude modulation and modulation masking

An audio watermarking system based on amplitude modulation (AM) is tested under the evaluation criteria proposed by the Information Hiding Criteria committee. Sinusoidal AMs at relatively low modulation frequencies, applied in opposite phase to neighboring subband signals, are used as the carrier of embedded information. The embedded information is encoded in the form of the relative phase differences between the AMs applied to several groups of subband signals. Results of computer simulation to test robustness and objective sound quality of stego audio showed that the quality degradation caused by the watermarking was tolerable and the detectability of the watermark under mandatory attack tests (DA/AD conversion and MP3 coding) and optional attack tests (bandpass filtering, tandem MP3 coding, MPEG4AAC coding) was sufficiently maintained.