Detecting media watermarks in magnetic field data
First Claim
1. A media monitor comprising:
- a magnetic field estimator in communication with a magnetometer, the magnetic field estimator to obtain magnetic field data determined by the magnetometer, the magnetic field data associated with a first sampling rate;
a frequency transformer to transform magnitude values of the magnetic field data to a frequency domain to determine transformed magnetic field data; and
a watermark decoder to process a portion of the transformed magnetic field data associated with a first frequency to detect an audio watermark encoded in an audio signal, the audio watermark having a frequency component associated with a second frequency different from the first frequency, the first frequency being aliased relative to the second frequency based on the first sampling rate.
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Abstract
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 monitoring methods disclosed herein include accessing magnetic field data determined by a magnetometer, the magnetic field data associated with a first sampling rate. Disclosed example methods also include transforming magnitude values of the magnetic field data to a frequency domain to determine transformed magnetic field data. Disclosed example methods further include evaluating a portion of the transformed magnetic field data associated with a first frequency to detect a media watermark having a frequency component associated with a second frequency different from the first frequency, the first frequency being aliased relative to the second frequency based on the first sampling rate.
91 Citations
20 Claims
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1. A media monitor comprising:
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a magnetic field estimator in communication with a magnetometer, the magnetic field estimator to obtain magnetic field data determined by the magnetometer, the magnetic field data associated with a first sampling rate; a frequency transformer to transform magnitude values of the magnetic field data to a frequency domain to determine transformed magnetic field data; and a watermark decoder to process a portion of the transformed magnetic field data associated with a first frequency to detect an audio watermark encoded in an audio signal, the audio watermark having a frequency component associated with a second frequency different from the first frequency, the first frequency being aliased relative to the second frequency based on the first sampling rate. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A media monitoring method comprising:
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accessing, by executing an instruction with a processor, magnetic field data determined by a magnetometer, the magnetic field data associated with a first sampling rate; transforming, by executing an instruction with the processor, magnitude values of the magnetic field data to a frequency domain to determine transformed magnetic field data; and evaluating, by executing an instruction with the processor, a portion of the transformed magnetic field data associated with a first frequency to detect an audio watermark encoded in an audio signal, the audio watermark having a frequency component associated with a second frequency different from the first frequency, the first frequency being aliased relative to the second frequency based on the first sampling rate. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A non-transitory computer readable medium comprising computer readable instructions that, when executed, cause a processor to at least:
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access magnetic field data determined by a magnetometer, the magnetic field data associated with a first sampling rate; transform magnitude values of the magnetic field data to a frequency domain to determine transformed magnetic field data; and evaluate a portion of the transformed magnetic field data associated with a first frequency to detect an audio watermark encoded in an audio signal, the audio watermark having a frequency component associated with a second frequency different from the first frequency, the first frequency being aliased relative to the second frequency based on the first sampling rate. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification