Removal of fixed pattern noise and other fixed patterns from media signals
AssigneeDigimarc Corporation
InventorsBrett T. Hannigan, Brett A. Bradley, Geoffrey B. Rhoads
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Abstract
A method of removing fixed pattern noise derives an estimate of fixed pattern noise from a composite media signal and uses the estimate to evaluate and remove fixed pattern noise from selected frames. The technique is particularly suited for removing fixed pattern noise in images due to image capture processes, but applies to other media signals as well. In watermarking applications, the method can be used to improve detection and recovery of a watermark. Also, it may be used to remove components of a watermark or a watermark from a cover signal that contains two or more different watermarks.
Claims20
A method of removing noise from a media signal comprising:
- combining frames of the media signal to form a composite signal;
- removing a DC component from the composite signal;
- deriving a measure of fixed pattern noise from the composite signal;
- using the measure of fixed pattern noise to compute an estimate of fixed pattern noise in a frame of the media signal;
- and
- removing the estimate of fixed pattern noise from the frame.
A watermark decoder preprocessor comprising:
- a compositer for combining frames of a media signal into a composite signal;
- a filter for removing a DC component from the composite signal and creating a measure of fixed pattern noise;
- an estimater for using the measure of fixed pattern noise to estimate fixed pattern noise in a selected frame of the media signal;
- and
- a remover for removing the estimate of the fixed pattern noise from the selected frame.
A watermark decoder preprocessor comprising:
- means for combining frames of a media signal into a composite signal;
- means for computing a measure of fixed pattern noise;
- means for using the measure of fixed pattern noise to estimate fixed pattern noise in a selected frame of the media signal;
- and
- means for removing the estimate of the fixed pattern noise from the selected frame.
A method of removing fixed pattern noise from an image signal comprising:
- combining frames of images captured from an image sensor into a composite image;
- applying a high pass filter to the composite image;
- normalizing the composite signal by removing an average energy from the composite signal;
- deriving a measure of fixed pattern noise from the normalized composite signal;
- using the measure of fixed pattern noise to compute an estimate of fixed pattern noise in a selected image captured from the image sensor;
- and
- subtracting the estimate of fixed pattern noise from the selected image.
Dependencies are inferred from the claim text.