Magnetometer-Based Media Watermark Detection
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Solution Overview
Problem
Existing media watermark detection techniques fail to detect watermarks embedded in audio signals at frequencies below the threshold of speaker capabilities, especially when direct access to the audio signal is restricted by digital rights management, and they cannot utilize magnetic field variations induced by the audio circuitry.
Innovation Solution
The method involves accessing multidimensional magnetic field data from a magnetometer in portable devices to detect watermarks by processing magnitude values, transforming them into the frequency domain, and evaluating specific frequency ranges or correlating them with reference sequences to identify watermarks, even when they are inaudible or inaccessible through traditional audio signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional audio signal processing is used to detect watermarks, then watermarks at audible frequencies can be detected, but watermarks below speaker threshold frequencies cannot be detected
Solution Approach 1:
The patent uses magnetic field measurements as an intermediary to detect audio watermarks. Instead of directly analyzing audio signals, the system measures magnetic field variations caused by current flow in speaker voice coils, which indirectly reveals the audio signal including sub-audible watermarks that traditional microphones cannot capture.
Solution Approach 2:
The patent replaces the acoustic measurement system (microphones) with a magnetic field measurement system (magnetometers). This substitution enables detection of frequencies below the speaker's audible threshold because magnetometers can detect the magnetic field variations caused by electrical currents in the speaker wiring without being limited by acoustic frequency responses.
2Measurement precision
If direct access to audio signal is required for watermark detection, then watermark detection accuracy is high, but access is restricted by digital rights management
Solution Approach 1:
The magnetic field measurements serve as an intermediary that provides indirect access to the audio signal. The magnetometer captures magnetic field variations caused by the audio current in the speaker, allowing watermark detection without requiring direct access to the protected audio signal, thus bypassing digital rights management restrictions.
Solution Approach 2:
The system uses the speaker's own electrical current as the source of information. By measuring the magnetic field generated by the speaker's voice coil during normal operation, the system extracts watermark information from the speaker's self-generated electromagnetic emissions without needing external signal access or modification.
3Adaptability or versatility
If magnetometer is used to detect watermarks in magnetic field data, then watermarks below speaker threshold can be detected, but the system complexity increases
Solution Approach 1:
The patent leverages the existing magnetometer in portable devices, which was originally designed for other functions (such as compass or spatial orientation). By repurposing this existing sensor for watermark detection, the system gains extended frequency detection capability without adding dedicated new hardware, thus reducing the net increase in system complexity.
Solution Approach 2:
The system utilizes the speaker and magnetometer components that are already present in modern portable devices. By processing magnetic field data from the existing magnetometer during normal speaker operation, the system achieves extended functionality (sub-audible watermark detection) without requiring additional specialized hardware, thereby minimizing the increase in device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the detection of watermarks in magnetic field data without direct access to the audio signal, allowing for the identification of embedded information in frequencies below the speaker's threshold, overcoming limitations of prior techniques and providing effective media monitoring even when digital rights management restricts access.
Implementation Method 1
audio circuitry that is to output an audio signal... multidimensional magnetic field data representative of values of a magnetic field measured within a first distance of the audio circuitry
Data Source
AI summary
Methods, apparatus, systems and articles of manufacture (e.g., physical storage media) to detect media watermarks in magnetic field data are disclosed herein. Example media monitors disclosed herein include a magnetic field estimator to determine first magnetic field data, the magnetic field estimator in communication with a magnetometer. Disclosed example media monitors also include a correlator to correlate the first magnitude field data with a reference sequence to determine second magnetic field data. Disclosed example media monitors further include a watermark decoder to process the second magnetic field data to detect an audio watermark encoded in an audio signal.