DIGITAL WATERMARK DETECTING DEVICE, METHOD, AND PROGRAM

According to an embodiment, a digital watermark detecting device includes a residual signal extractor, a voiced period estimator, a storage, a phase estimator, and a watermark determiner. The residual signal extractor is configured to extract a residual signal from a speech signal. The voiced period estimator is configured to estimate a voiced period based on the speech signal. The storage is configured to store pulse signals modulated in advance so as to have different phases. The phase estimator is configured to clip the voiced period in units of an analysis frame having a predetermined length, and perform pattern matching between the residual signal in the analysis frame and the pulse signals to estimate phase of the speech signal. The watermark determiner is configured to, based on a sequence of phases estimated by the phase estimator, determine whether a digital watermark is embedded in the speech signal or not.