Robust spectral encoding and decoding methods
First Claim
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1. A device for decoding a digital watermark embedded in an audio signal, wherein the digital watermark is embedded in the audio signal by adjusting signal values, the device comprising:
- a memory in which is stored blocks of the audio signal;
a processor in communication with the memory to obtain blocks of the audio signal, the processor configured with instructions to;
perform an initial synchronization of the digital watermark, distorted due to time scale change, by converting blocks of the audio to frequency domain data, pre-filtering the frequency domain data to produce first pre-filtered blocks, summing the first pre-filtered blocks to produce a first accumulated block, the first pre-filtered blocks being selected over a sufficiently long block of audio such that plural instances of watermark signal representing the same code at different time locations are accumulated, and correlating the first accumulated block with a pattern to detect a time scale of an embedded code signal; and
perform decoding of variable code data of the digital watermark at the detected time scale by correlating phase of the audio signal at the detected shift with a data signal pattern, wherein the processor is configured with instructions to decode the variable code data by correlating phase of the audio signal with a synchronization code signal to identify a start position of the variable code, and correlating phase of the audio signal with data code signals to detect data code signals encoded as the variable code data of the digital watermark.
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Abstract
Spectral encoding methods are more robust when used with improved weak signal detection and synchronizations methods. Further robustness gains are achieved by using informed embedding, error correction and embedding protocols that enable signal to noise enhancements by folding and pre-filtering the received signal.
15 Citations
15 Claims
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1. A device for decoding a digital watermark embedded in an audio signal, wherein the digital watermark is embedded in the audio signal by adjusting signal values, the device comprising:
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a memory in which is stored blocks of the audio signal; a processor in communication with the memory to obtain blocks of the audio signal, the processor configured with instructions to; perform an initial synchronization of the digital watermark, distorted due to time scale change, by converting blocks of the audio to frequency domain data, pre-filtering the frequency domain data to produce first pre-filtered blocks, summing the first pre-filtered blocks to produce a first accumulated block, the first pre-filtered blocks being selected over a sufficiently long block of audio such that plural instances of watermark signal representing the same code at different time locations are accumulated, and correlating the first accumulated block with a pattern to detect a time scale of an embedded code signal; and perform decoding of variable code data of the digital watermark at the detected time scale by correlating phase of the audio signal at the detected shift with a data signal pattern, wherein the processor is configured with instructions to decode the variable code data by correlating phase of the audio signal with a synchronization code signal to identify a start position of the variable code, and correlating phase of the audio signal with data code signals to detect data code signals encoded as the variable code data of the digital watermark. - View Dependent Claims (2, 3, 7, 8, 9)
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4. A tangible non-transitory, computer readable medium, on which is stored instructions, which, when executed by a computer, cause the computer to decode a digital watermark embedded in an audio signal, wherein the digital watermark is embedded in the audio signal by adjusting signal values, the instructions, which when executed by the computer, cause the computer to:
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perform an initial synchronization of the digital watermark, distorted due to time scale change by converting blocks of the audio to frequency domain data, pre-filtering the frequency domain to produce first pre-filtered blocks, summing the first pre-filtered blocks to produce a first accumulated block, the first pre-filtered blocks being selected over a sufficiently long block of audio such that plural instances of watermark signal representing the same code at different time locations are accumulated, and correlating the first accumulated block with a pattern to detect a time scale of an embedded code signal; and perform decoding of variable code data of the digital watermark at the detected time scale by correlating phase of the audio signal at the detected shift with a data signal pattern, wherein the instructions on the medium cause the computer to decode the variable code data by correlating phase of the audio signal with a synchronization code signal to identify a start position of the variable code, and correlating phase of the audio signal with data code signals to detect data code signals encoded as the variable code data of the digital watermark. - View Dependent Claims (5, 6, 10, 11, 12)
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13. A method for decoding a digital watermark embedded in an audio signal, the method comprising:
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converting blocks of the audio signal to frequency domain data; pre-filtering the frequency domain data to produce first pre-filtered blocks; summing the first pre-filtered blocks to produce a first accumulated block, the first pre-filtered blocks being selected over a sufficiently long block of audio such that plural instances of watermark signal representing the same code at different time locations are accumulated; detecting signal peaks in the first accumulated block; determining a time scale change of the digital watermark based on locations of the signal peaks; and decoding variable code data encoded in the digital watermark by correlating phase of the audio signal at the determined time scale change with a data signal pattern, the decoding comprising correlating phase of the audio signal with a synchronization code signal to identify a start position of the variable code, and correlating phase of the audio signal with data code signals to detect data code signals encoded as the variable code data of the digital watermark. - View Dependent Claims (14, 15)
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Specification