Audio Watermarking via Harmonic Frequency Embedding
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Solution Overview
Problem
Existing audio watermarking technologies often disturb listeners and are not effective in noisy environments due to their methods of embedding watermarks, which can be masked by re-encoding processes.
Innovation Solution
An audio watermarking system that encodes watermark data in or near harmonic frequencies of audio content sections, analyzing frequency domains to identify suitable encoding opportunities with minimal amplitude, ensuring the watermark is less disturbing and resilient to re-encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If watermark data is embedded in audio content using conventional methods, then watermark detection becomes possible, but the watermark disturbs listeners and is masked by re-encoding processes
Solution Approach 1:
The patent applies local quality by selectively embedding watermark data only in specific frequency ranges where the audio signal amplitude is below a predetermined threshold. The system analyzes the frequency spectrum of audio content and identifies regions with low signal energy, then embeds watermark bits only in those regions. This ensures that the watermark does not interfere with prominent audio components, thereby reducing listener disturbance while maintaining detectability.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the embedding strength and frequency selection based on the local characteristics of the audio signal. The system modifies the amplitude and frequency parameters of the watermark embedding process according to the analyzed spectral content, ensuring optimal placement in less perceptible regions. This adaptive parameter adjustment allows the watermark to remain detectable while minimizing auditory impact.
2Reliability
If watermark data is embedded with higher amplitude to improve detectability, then watermark detection becomes more reliable, but the watermark becomes more disturbing to listeners
Solution Approach 1:
The patent resolves this contradiction by applying local quality through frequency-selective embedding. Instead of using a uniform amplitude across all frequencies, the system embeds watermark data only in frequency ranges where the audio signal amplitude is below a predetermined threshold. This localized approach allows for reliable detection in quiet spectral regions while avoiding disturbance in regions with prominent audio content.
Solution Approach 2:
The patent applies the skipping principle by selectively bypassing frequency ranges that contain significant audio signal energy. The system analyzes the frequency spectrum and skips embedding watermark data in regions where the signal amplitude exceeds the threshold, rushing through those problematic regions to avoid disturbance. This selective skipping ensures that watermark embedding occurs only in safe, low-energy frequency zones.
3Device complexity
If watermark encoding is performed without pre-defining opportunities, then the process is simpler, but the watermark is more vulnerable to masking by re-encoding
Solution Approach 1:
The patent applies preliminary action by performing frequency spectrum analysis and identifying suitable embedding opportunities before actual watermark embedding. The system pre-defines which frequency ranges and time segments are appropriate for watermark placement based on the audio content characteristics. This preliminary analysis creates a roadmap for robust embedding that anticipates potential re-encoding operations, allowing the watermark to be placed in regions that will survive subsequent processing.
Solution Approach 2:
The patent utilizes beforehand cushioning by selecting embedding locations and parameters in advance that provide protection against re-encoding masking. The system identifies frequency ranges with low signal energy and embeds watermark data there, creating a cushion of robustness before re-encoding occurs. This prior preparation ensures that the watermark is positioned in regions least susceptible to being masked by re-encoding artifacts.
Data Source
AI summary
A system, including a processor to define opportunities for encoding a watermark into an audio stream having sections, each section, when represented in the frequency domain, including a signal of amplitude against frequency, the processor being operative to, for each one of the sections, identify a fundamental frequency, f being the frequency with the largest amplitude of the signal in the one section, the fundamental frequency f defining harmonic frequencies, each harmonic frequency being at a frequency f/2n or 2fn, n being a positive integer, and define the one section as an opportunity for encoding at least part of the watermark if the amplitude of the signal of the one section is less than a value v for all frequencies in one or more different frequency ranges, each of the different frequency ranges being centered around different ones of the harmonic frequencies. Related apparatus and methods are also described.