Data embedding and extraction

摘要

Disclosed are a method and arrangement for embedding data (dn) in a host signal (x_n) 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 (s_n) may have been scaled ( 72 ) unintentionally (by a communication channel) or intentionally (by a hacker). This causes the quantization step size (Delta_r) of the received signal (r_n) 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 (Delta_r) therefrom. In a preferred embodiment, a pilot sequence of predetermined data symbols (d_pilot) is embedded ( 76 ) in selected (S) samples of the host signal.