We have proposed a novel audio watermarking technique, which embeds a set of bitstream data by changing two-channel stereo locations of lower frequency components in an embedding target audio signal. This method features nearly lossless embedding, robustness against lossy data compression or analogue conversion, and enables contactless asynchronous detection of embedded watermarks through speaker and microphone devices without the original audio signals.

Then, we propose several extended monaural embedding methods, which embed data by changing level balances between two sets of lower frequency components, which are divided by either frequency or temporal dimensions. These methods also support nearly lossless embedding and enable watermark detection from only the left channel signal by a single monaural microphone, and we have confirmed detection capability by a cell phone.

In this paper, we describe abstracts of our proposed watermark embedding and extracting algorithms, experimental results of watermark extraction precision.