| 摘要 |
A digital watermark embedding apparatus (fig 6) generates an echo signal c, which is delayed a time period corresponding to digital watermark information b to be embedded with respect to each tone signal that forms an original audio signal a, and inserts the generated echo signal in the original audio signal by spreading the echo signal on the time axis using PN sequence generator 25 and time spread unit 24, thus outputting a watermarked audio signal d2. A digital watermark detection apparatus (fig 9) despreads echo signals contained in the watermarked audio signal d2 on the time axis, and extracts digital watermark information b from the generation time of the despread echo signal contained in the watermarked audio signal. The echo signal is despread by unit 31 which also computes the correlation between the watermarked audio signal and the signal g output by PN sequence generator 32.
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