Detecting media watermarks in magnetic field data
First Claim
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1. A method to detect media watermarks, the method comprising:
- accessing, by executing an instruction with a processor in communication with a magnetometer, multidimensional magnetic field data determined by the magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer, the multidimensional magnetic field data including a plurality of directional components; and
processing, by executing an instruction with the processor, the multidimensional magnetic field data determined by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, wherein the watermark modulates a first frequency of the audio signal, the multidimensional magnetic field data is accessed at a first sampling rate that is less than twice the first frequency, and the processing includes;
processing the directional components to determine magnitude values representative of a magnitude of the magnetic field over time;
transforming the magnitude values into a frequency domain to determine transformed magnetic field data; and
evaluating the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by accessing the multidimensional magnetic field data at 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 methods disclosed herein to detect media watermarks can include accessing multidimensional magnetic field data representative of values of a magnetic field measured within a first distance of audio circuitry that is to output an audio signal corresponding to media presented by a media device. Such example methods can also include processing the multidimensional magnetic field data to detect a watermark included in the audio signal.
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Citations
17 Claims
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1. A method to detect media watermarks, the method comprising:
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accessing, by executing an instruction with a processor in communication with a magnetometer, multidimensional magnetic field data determined by the magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer, the multidimensional magnetic field data including a plurality of directional components; and processing, by executing an instruction with the processor, the multidimensional magnetic field data determined by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, wherein the watermark modulates a first frequency of the audio signal, the multidimensional magnetic field data is accessed at a first sampling rate that is less than twice the first frequency, and the processing includes; processing the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; transforming the magnitude values into a frequency domain to determine transformed magnetic field data; and evaluating the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by accessing the multidimensional magnetic field data at the first sampling rate. - View Dependent Claims (2, 3, 5)
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4. A method to detect media watermarks, the method comprising:
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accessing, by executing an instruction with a processor in communication with a magnetometer, multidimensional magnetic field data determined by the magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer, the multidimensional magnetic field data including a plurality of directional components; and processing, by executing an instruction with the processor, the multidimensional magnetic field data determined by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, wherein the multidimensional magnetic field data is first magnetic field data, and the processing includes; processing the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; correlating the magnitude values with a reference sequence to determine second magnetic field data; and processing the second magnetic field data to detect the watermark. - View Dependent Claims (13, 14)
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6. A tangible machine readable storage medium comprising machine readable instructions which, when executed, cause a processor to at least:
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access multidimensional magnetic field data determined by a magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer, the multidimensional magnetic field data including a plurality of directional components; and process the multidimensional magnetic field data determined by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, wherein the watermark modulates a first frequency of the audio signal, and the machine readable instructions, when executed, further cause the processor to; access, at a first sampling rate that is less than twice the first frequency, the multidimensional magnetic field data; process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; transform the magnitude values into a frequency domain to determine transformed magnetic field data; and evaluate the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by accessing the multidimensional magnetic field data at the first sampling rate. - View Dependent Claims (7, 15)
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8. A tangible machine readable storage medium comprising machine readable instructions which, when executed, cause a processor to at least:
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access multidimensional magnetic field data determined by a magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer; and process the multidimensional magnetic field data determined by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, wherein the multidimensional magnetic field data includes a plurality of directional components, and the machine readable instructions, when executed, further cause the processor to; process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; correlate the magnitude values with a reference sequence to determine second magnetic field data; and process the second magnetic field data to detect the watermark. - View Dependent Claims (16)
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9. An apparatus to detect media watermarks, the apparatus comprising:
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a magnetic field estimator in communication with a magnetometer, the magnetic field estimator to access multidimensional magnetic field data determined by the magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer, the multidimensional magnetic field data including a plurality of directional components, the magnetic field estimator to process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; and a watermark detector to process the multidimensional magnetic field data measured by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, the watermark detector including; a frequency transformer to transform the magnitude values into a frequency domain to determine transformed magnetic field data; and a watermark decoder to process the transformed magnetic field data to detect the watermark, wherein the watermark modulates a first frequency of the audio signal, the multidimensional magnetic field data is to be accessed by the magnetic field estimator at a first sampling rate that is less than twice the first frequency, and the watermark decoder is to evaluate the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by the multidimensional magnetic field data being accessed at the first sampling rate. - View Dependent Claims (10, 11)
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12. An apparatus to detect media watermarks, the apparatus comprising:
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a magnetic field estimator in communication with a magnetometer, the magnetic field estimator to access multidimensional magnetic field data determined by the magnetometer, the multidimensional magnetic field data representative of values of a magnetic field measured by the magnetometer, the multidimensional magnetic field data including a plurality of directional components, the magnetic field estimator to process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; and a watermark detector to process the multidimensional magnetic field data measured by the magnetometer to detect a watermark included in an audio signal output by audio circuitry of a media device, the audio signal corresponding to media presented by the media device, wherein the multidimensional magnetic field data is first magnetic field data, and the watermark detector includes; a correlator to correlate the magnitude values with a reference sequence to determine second magnetic field data; and a watermark decoder to process the second magnetic field data to detect the watermark. - View Dependent Claims (17)
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Specification