Digital Watermarking Geometric Distortion Correction
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Solution Overview
Problem
Existing digital watermarking algorithms face challenges in maintaining synchronization and robustness against geometric distortions such as cropping, rotation, and scaling, which often lead to failure in watermark decoding.
Innovation Solution
The method involves embedding three or more pilot signals in the spatial domain to estimate and invert geometric distortions, while embedding the watermark in the transform domain, using a just-noticeable-difference (JND) model to ensure robustness and high capacity, and spreading pilot signals across different frames to provide a geometric frame of reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If geometric distortions are applied to watermarked content during transmission, then the content can be processed and adapted to different devices, but the synchronization between watermark encoder and decoder is destroyed, leading to decoding failure
Solution Approach 1:
The patent applies preliminary action by embedding pilot signals into the watermarked content before transmission. These pilot signals serve as reference markers that enable the decoder to detect and correct geometric distortions in advance, maintaining synchronization even when the content is cropped, rotated, or scaled during transmission.
Solution Approach 2:
The patent implements feedback by using the detected pilot signals to estimate the geometric distortion parameters, then applying the inverse transformation to correct the distortion before watermark decoding. This feedback loop ensures that the decoder adapts to the actual distortions applied to the content, restoring synchronization between encoder and decoder.
2Device complexity
If traditional watermarking algorithms are used without pilot signals, then the system complexity is lower, but the watermark decoding fails under geometric distortions
Solution Approach 1:
The patent introduces pilot signals as intermediary elements that mediate between the watermark encoder and decoder. These pilot signals do not carry the actual watermark message but serve as auxiliary references that enable the decoder to locate and synchronize with the watermarked content even after geometric transformations.
3Measurement precision
If pilot signals are embedded in the spatial domain, then geometric distortion estimation becomes possible, but the watermark capacity in the transform domain must be maintained separately
Solution Approach 1:
The patent applies segmentation by separating the functionality into two distinct domains: spatial domain for pilot signal embedding (used for geometric distortion estimation) and transform domain for watermark embedding (used for high-capacity message transmission). This segmentation allows each domain to be optimized for its specific purpose without interfering with the other.
Data Source
AI summary
In an embodiment, a method of decoding a watermarked video includes receiving a video including a watermark and three or more pilot signals. The method includes attempting to detect the watermark and retrieve a corresponding message in the video based on one or more decoding starting points of the video. The method includes outputting the message if the attempt is successful. If the attempt fails, the method includes detecting the pilot signals in the video; based on the detected pilot signals, estimating a geometric distortion of the video; inverting the geometric distortion for the video to generate a warped video; and attempting to detect the watermark and retrieve the corresponding message in the warped video based on one or more decoding starting points of the warped video.