2D Watermark Decoding for Low-Complexity Robust Bit Recovery
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Solution Overview
Problem
Existing watermarking systems face issues with unsatisfactory bit error rates and high 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 spread a single message bit in both time and frequency domains, creating a two-dimensional spread information representation to enhance reliability and robustness against typical distortion sources, using separate and common spread sequences for frequency and time directions to facilitate decoding while reducing computational complexity.
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 segments the single message bit into two separate spreading operations: first spreading in the frequency domain using a frequency spread sequence, then spreading the intermediate result in the time domain using a time spread sequence. This segmentation of the spreading process into orthogonal frequency and time components reduces the computational burden of decoding while maintaining the robustness benefits of long spreading sequences.
Solution Approach 2:
The patent introduces a two-dimensional spreading approach, spreading the message bit across both frequency and time dimensions independently. By adding this additional dimension (frequency spreading) to the traditional time spreading, the system achieves enhanced robustness without proportionally increasing decoding complexity, as each dimension can be processed separately during decoding.
2Ease of manufacture
If traditional watermarking methods are used, then implementation is simple, but bit error rate is unsatisfactory
Solution Approach 1:
The patent improves bit error rate by transitioning from traditional single-dimension (time-domain) spreading to two-dimensional spreading that includes both frequency and time domains. The frequency spreading component distributes the message across multiple frequency bins, providing redundancy that helps overcome narrowband distortions and improves detection reliability, while the time spreading maintains compatibility with existing watermarking frameworks.
3Reliability
If frequency spreading is applied, then robustness against narrow band distortion is improved, but computational complexity increases
Solution Approach 1:
The patent segments the spreading operation into distinct frequency and time components that can be processed independently. The frequency spreading is performed first to achieve robustness against narrowband distortion, then time spreading is applied. During decoding, these segmented operations can be reversed in sequence, reducing computational complexity compared to a monolithic spreading approach.
Data Source
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AI summary
A watermark generator (2400) for providing a watermark signal (2420) in dependence on binary message data (2410) comprises an information processor (2430) configured to provide, in dependence on a single message bit of the binary message data, a 2-dimensional spread information (2432) representing the message bit in the form of a set of time-frequency-domain values. The watermark generator also comprises a watermark signal provider (2440) 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.