A Digital Watermark for Stereo Audio Signals Using Variable Interchannel Delay in High Frequency Bands

The authors propose a watermarking algorithm for stereo audio signals which embeds data using delay values of the high frequency channel signals. Since the stereo image perception of the human auditory system is known to be relatively insensitive to phase in high frequency regions, we replace the high frequency components with one middle channel, and embed data as delay between the channels. Blind detection of embedded data is possible using correlation between high frequency channels at the detector. Embedded data rate was 7 to 30 bps depending on the host audio signal. Embedded data was detected with little or no errors for added noise at 20 dB SNR and above. MP3 and AAC coders were shown not to affect the embedded data as well. The embedded audio quality was shown to be sound dependent, with quality equivalent to MP3 coded audio with some audio, but significantly lower for other sources.