Watermark Extraction via Gain and Delay Compensation
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Solution Overview
Problem
Existing audio watermarking systems face a trade-off between reliability and audibility, with current methods being ineffective in extracting watermarks from output signals due to unknown and time-varying changes introduced by watermarking encoders, making it difficult to achieve 100% reliability and inaudibility simultaneously.
Innovation Solution
A system and method for extracting watermarks from the output of a watermarking encoder without accessing its internal operations, using a gain and delay adjustor and an adjustment signal generator to compensate for changes in the input and output signals, allowing for accurate subtraction of the watermark signal, independent of the encoder's specifics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If watermarking modifies the original audio to embed digital information, then reliability of watermark embedding is improved, but audibility of the watermark increases
Solution Approach 1:
The patent replaces traditional time-domain watermarking methods with frequency-domain processing. By transforming the audio signal into the frequency domain using FFT, the system can embed watermarks in specific frequency bins where they are less perceptible to human hearing, thus maintaining reliability while reducing audibility.
Solution Approach 2:
The system dynamically adjusts watermark parameters including frequency selection, amplitude modulation depth, and spectral spreading based on the local audio characteristics. This allows optimization of the watermark signal to be embedded in less perceptible frequency regions while maintaining robustness against playback conditions.
2Measurement precision
If adaptive filters are used to compensate for encoder changes, then measurement accuracy is improved, but reliability of extraction decreases due to spectrum dependency
Solution Approach 1:
The patent creates a digital twin or model of the watermarking encoder's effect on the signal. By analyzing how the encoder modifies specific frequency components and creating a corresponding compensation model, the system can accurately reverse the encoding process without relying on adaptive filtering that is sensitive to spectral changes.
Solution Approach 2:
The extraction algorithm is designed to be universal and independent of the specific audio content spectrum. It works reliably across different types of audio material (music, speech, noise) by using frequency-domain analysis that compensates for encoder effects without being dependent on the particular spectral characteristics of the input signal.
3Device complexity
If simple subtraction of input from output is used to extract watermark, then device complexity is reduced, but measurement precision deteriorates due to encoder-induced changes
Solution Approach 1:
The patent replaces simple time-domain subtraction with frequency-domain processing. By applying FFT to both input and output signals, the system can identify and isolate the watermark components in the frequency spectrum, then accurately subtract only the watermark portion while compensating for encoder-modified audio components.
Solution Approach 2:
The system segments the audio signal into frequency bins using FFT, allowing separate processing of different frequency components. This enables precise identification of watermark-bearing frequency bins and accurate reconstruction of the watermark signal by processing each segment independently and then recombining them.
Data Source
AI summary
A device for extracting a watermark signal from an output signal of a watermarking encoder in which the output signal includes an input signal portion corresponding to an input signal to the watermarking encoder and a watermark signal portion corresponding to the watermark signal includes an input configured to receive the input signal and the output signal. The device further includes an adjustment signal generator configured to generate a gain adjustment signal and a delay adjustment signal based on the input signal and the output signal, a gain and delay adjustor configured to adjust gain and delay of the output signal or the input signal based on the gain adjustment signal and the delay adjustment signal, respectively, to generate an adjusted output signal or an adjusted input signal, respectively, and an output configured to transmit a difference between the input signal and the adjusted output signal or a difference between the adjusted input signal and the output signal as the watermark signal.