| 摘要 |
<p>Disclosed are a method and arrangement for embedding data (dn) in a host signal (xn) using dithered quantization index modulation (71), and extracting said data from the watermarked signal. A problem of this embedding scheme (71) is that the amplitude of the watermarked signal (sn) may have been scaled (72) unintentionally (by a communication channel) or intentionally (by a hacker). This causes the quantization step size (Δr) of the received signal (rn) to be unknown to the extractor (73) which is essential for reliable data extraction. The invention provides making a histogram (74) of those signal samples that have substantially the same amount of dither, and analyzing said histogram to derive an estimation of the step size (Δr) therefrom. In a preferred embodiment, a pilot sequence of predetermined data symbols (dpilot) is embedded (76) in selected (S) samples of the host signal.</p> |
