Quantization -based data hiding employing calibration and locally adaptive quantization
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Accused Products
Abstract
Certain forms of distortion make it difficult to recover hidden data embedded in an audio or image signal by quanitzation techniques. To compensate for this distortion, an embedded data reader analyzes a statistical distribution (e.g., a histogram) of feature samples (124) in an audio or image signal suspected of having hidden auxiliary data to derive an estimate of quantizers used to encode a reference signal (126). The estimated quantizers then recover the reference signal (126), and the reader uses the reference signal(126) to determine and compensate for geometric or temporal distortion, like spatial scaling and rotation of image data, and time scale and speed changes of audio data. After compensating for such distortion, the reader can then more accurately recover hidden message data using quantization techniques to extract the message. The reference signal (126) is preferably repeated in blocks of the image or audio data to enable synchronization at many points in an image or audio data stream. An adaptive embedding and reading technique is used to adaptively define the quantization bins for regions of a host media signal based on signal statistics for each of the regions.
83 Citations
65 Claims
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1-50. -50. (cancelled)
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51. A method of embedding a digital watermark in a media signal comprising:
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embedding a first digital watermark in the media signal to produce a watermarked media signal;
quantizing elements of the watermarked media signal to values corresponding to message symbols of a secondary digital watermark;
wherein the first digital watermark is used to calibrate the media signal before extracting the secondary digital watermark. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58)
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59. A method of decoding a digital watermark from a watermarked media signal comprising:
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detecting a first digital watermark in the watermarked media signal, the first digital watermark enabling calibration of the watermarked media signal; and
quantizing elements of the calibrated watermarked media signal to extract values corresponding to message symbols of a secondary digital watermark;
wherein the first digital watermark is used to calibrate the watermarked media signal before extracting the secondary digital watermark. - View Dependent Claims (60, 61, 62, 63, 64, 65)
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Specification