Patent ID: 7072492

Claim:
A method for reading digital watermark data from digital data contents in which each bit of digital watermark data is embedded a plurality of times, said method comprising: receiving digital data contents; reading a digital watermark sequence from said digital data contents; performing soft decision in code theory by assigning weights to said digital watermark sequence with a weighting function; and reconstituting and generating digital watermark data from said digital watermark sequence; wherein said weighting function is a distribution function obtained by a method including: dividing first digital data contents into one or a plurality of first block data; dividing second digital data contents into one or a plurality of second block data, said second digital data contents being obtained by manipulating said first digital data contents with a predetermined manipulation method; transforming said first block data and said second block data into first frequency coefficients and second frequency coefficients respectively by applying an orthogonal transform; and obtaining distribution of difference values between said first frequency coefficients and said second frequency coefficients, said distribution function being an approximation of said distribution, wherein said weights are assigned to said digital watermark sequence according to values of said distribution function.