Digital watermarking
First Claim
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1. A method for inserting a watermark signal into data to be watermarked comprising the steps of:
- dividing data to be watermarked into a plurality of subregions;
computing frequency coefficients of the data to be watermarked in each subregion;
spread spectrum modulating a watermark signal to be inserted by mapping the watermark signal into a PN (pseudo-random noise) sequence;
spectral shaping the PN sequence as a function of the average power in each frequency coefficient of the data; and
inserting each spectral shaped PN sequence into predetermined coefficients in the data in each subregion.
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Abstract
Digital watermarking of data, including image, video and audio data, is performed by repeatedly inserting the watermark into subregions or subimages of the data. Similarly, the watermark is repeatedly extracted from the subregions of the data.
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Citations
28 Claims
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1. A method for inserting a watermark signal into data to be watermarked comprising the steps of:
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dividing data to be watermarked into a plurality of subregions; computing frequency coefficients of the data to be watermarked in each subregion; spread spectrum modulating a watermark signal to be inserted by mapping the watermark signal into a PN (pseudo-random noise) sequence; spectral shaping the PN sequence as a function of the average power in each frequency coefficient of the data; and inserting each spectral shaped PN sequence into predetermined coefficients in the data in each subregion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of extracting a watermark from watermarked data comprising the steps of:
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receiving subregions of watermarked data; spectrum normalizing the watermarked data as a function of the average power in each frequency coefficient of the watermarked data in each subregion to generate respective normalized signals; combining the respective normalized signals from each subregion to generate a single watermark; correlating the single watermark with predetermined PN (pseudo-random noise) sequences corresponding to predetermined symbols to provide correlated signals for each predetermined PN sequence in each subregion; deciding which correlated signal is most likely a current symbol; and extracting a sequence of most likely current symbols corresponding to the watermark. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. A method of extracting a watermark from watermarked data comprising the steps of:
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receiving subregions of watermarked data; spectrum normalizing the watermarked data as a function of the average power in each frequency coefficient of the watermarked data in each subregion to generate respective normalized signals; correlating the respective normalized signals with predetermined PN sequences corresponding to predetermined symbols to provide correlated signals for each predetermined PN sequence in each subregion; deciding which correlated signal is most likely a current symbol in each subregion for providing an extracted symbol stream; error correcting the extracted symbol stream; and extracting a sequence of most likely current symbols corresponding to the watermark. - View Dependent Claims (24)
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25. A method for inserting a watermark signal into data to be watermarked comprising the steps of:
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dividing data to be watermarked into a plurality of subregions; dividing a watermark signal into a plurality of subwatermarks where portions of the watermark are contained in more than one subwatermark; and inserting said plurality of subwatermarks into said plurality of subregions. - View Dependent Claims (26)
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27. A method for extracting a watermark signal from watermarked data comprising the steps of:
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receiving a plurality of subregions of watermark data; extracting a subwatermark from each subregion of said plurality of subregions; and combining and averaging the subwatermarks extracted from all the subregions to obtain a signal commensurate with the watermark signal. - View Dependent Claims (28)
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Specification