Two channel digital watermarking for music based on exponential time-spread echo kernel

To robustly and imperceptibly embed copyright information as a watermark into music clips, a two channel digital watermarking system based on the least significant bit (LSB) method and echo hiding (EH) with a new exponential time-spread echo kernel (ETEK) is proposed. By spreading the echo so that it seems like natural room reverberation, as well as the use of two channels to separately watermark by the LSB method and the EH method which have complementary characteristics, the system provides satisfactory sound quality and exhibits both efficient retrieval capacity and robustness against attacks. Experiments show that the proposed system retrieves watermarks with 100% accuracy for all clips and is almost imperceptible. With a set of 42 attacks supplied by the StirMark Benchmark for Audio (SMBA), the proposed system has an average robustness of 0.98 where the ideal value is 1.00, and higher than any conventional methods. With these results, the proposed system is shown to be possible for the application to music distribution over the Internet.