Method and apparatus for regaining watermark data that were embedded in an original signal by modifying sections of said original signal in relation to at least two different reference data sequences
First Claim
1. Method for regaining watermark data that were embedded in an original signal by modifying sections of said original signal in relation to at least two different reference data sequences, wherein a modified signal section is denoted as ‘
- marked’ and
an original signal section is denoted as ‘
non-marked’
, said method including the steps;
correlating in each case a current section of a received version of said watermarked signal with candidates of said reference data sequences, wherein said received watermarked signal can include noise and/or echoes;
based on the correlation result values for said current signal section,optionally determining whether said current signal section is non-marked and if not true, carrying out the following steps;
determining for each one of said candidate reference data sequences, based on two or more significant peaks in said correlation result values, the false positive probability, wherein said false positive probability is derived from the probability density function of the amplitudes of the correlation result for a non-marked signal section and from a first threshold value related to said probability density function;
selecting for said current signal section that one of said candidate reference data sequences which has the lowest false positive probability, in order to provide said watermark data.
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Accused Products
Abstract
Every watermarking processing needs a detection metric to decide at decoder side whether audio signal content is marked, and which symbol is embedded inside the audio signal content. The invention provides a new detection metric that achieves a reliable detection of watermarks in the presence of additional noise and echoes. This is performed by taking into account the information contained in the echoes of the received audio signal in the decision metric and comparing it with the corresponding metric obtained from decoding a non-marked audio signal, based on calculating the false positive detection rates of the reference sequences for multiple peaks. The watermark symbol corresponding to the reference sequence having the lowest false positive error is selected as the embedded one.
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Citations
16 Claims
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1. Method for regaining watermark data that were embedded in an original signal by modifying sections of said original signal in relation to at least two different reference data sequences, wherein a modified signal section is denoted as ‘
- marked’ and
an original signal section is denoted as ‘
non-marked’
, said method including the steps;correlating in each case a current section of a received version of said watermarked signal with candidates of said reference data sequences, wherein said received watermarked signal can include noise and/or echoes; based on the correlation result values for said current signal section, optionally determining whether said current signal section is non-marked and if not true, carrying out the following steps; determining for each one of said candidate reference data sequences, based on two or more significant peaks in said correlation result values, the false positive probability, wherein said false positive probability is derived from the probability density function of the amplitudes of the correlation result for a non-marked signal section and from a first threshold value related to said probability density function; selecting for said current signal section that one of said candidate reference data sequences which has the lowest false positive probability, in order to provide said watermark data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- marked’ and
-
9. Apparatus for regaining watermark data that were embedded in an original signal by modifying sections of said original signal in relation to at least two different reference data sequences, wherein a modified signal section is denoted as ‘
- marked’ and
an original signal section is denoted as ‘
non-marked’
, said apparatus including means being adapted for;correlating in each case a current signal section of a received version of said watermarked signal with candidates of said reference data sequences, wherein said received watermarked signal can include noise and/or echoes; based on the correlation result values for said current signal section, optionally determining whether said current signal section is non-marked and if not true, carrying out the following steps; determining for each one of said candidate reference data sequences, based on two or more significant peaks in said correlation result values, the false positive probability, wherein said false positive probability is derived from the probability density function of the amplitudes of the correlation result for a non-marked signal section and from a first threshold value related to said probability density function; selecting for said current signal section that one of said candidate reference data sequences which has the lowest false positive probability, in order to provide said watermark data. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
- marked’ and
Specification