2D Watermark Decoding for Distortion-Robust Bit Detection
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Solution Overview
Problem
Existing watermarking systems face issues with high bit error rates and decoding complexity, particularly when using long spreading sequences, and are sensitive to narrow band and pulse-like distortions.
Innovation Solution
A watermark generator and decoder that utilize 2-dimensional spread information, spreading message bits in both time and frequency domains using orthogonal sequences, and perform 2-dimensional despreading to improve reliability and robustness against typical distortion sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long spreading sequences are used in watermarking systems, then robustness against distortion is improved, but decoding complexity increases
Solution Approach 1:
The patent divides the long spreading sequence into multiple shorter orthogonal sequences arranged in a two-dimensional structure (time domain and frequency domain). This segmentation reduces the computational burden of decoding while maintaining the robustness benefits of long spreading sequences through the combined effect of multiple orthogonal sequences.
Solution Approach 2:
The patent introduces a two-dimensional spreading structure with sequences arranged in both time domain and frequency domain. This dimensional expansion allows the system to achieve equivalent robustness to long single-dimensional sequences while enabling more efficient decoding through the orthogonal properties of the multi-dimensional sequence structure.
2Device complexity
If traditional watermarking methods are used, then implementation is simpler, but bit error rate increases under narrow band or pulse-like distortions
Solution Approach 1:
The patent employs two-dimensional spreading with orthogonal sequences in both time and frequency domains. This multi-dimensional approach provides redundancy that protects against narrow band distortions (affecting frequency domain) and pulse-like distortions (affecting time domain), significantly reducing bit error rates while maintaining practical implementation complexity.
Solution Approach 2:
The patent combines multiple orthogonal sequences in a composite two-dimensional structure, creating a robust watermarking signal that integrates the protective benefits of both time-domain and frequency-domain spreading. This composite structure maintains implementation feasibility while dramatically improving reliability under various distortion conditions.
Data Source
AI summary
A watermark generator for providing a watermark signal in dependence on binary message data includes an information processor configured to provide, in dependence on a single message bit of the binary message data, a 2-dimensional spread information representing the message bit in the form of a set of time-frequency-domain values. The watermark generator also includes a watermark signal provider configured to provide the watermark signal on the basis of the 2-dimensional spread information.A watermark detector, methods and computer programs are also described.