Method and apparatus for watermarking successive sections of an audio signal
View Patent ↗Audio watermarking is the process of embedding watermark information items into an audio signal in an in-audible manner. In a first embodiment, in case the original audio signal has parts of low signal energy, an alternative signal having a level or strength given by the psycho-acoustic model is combined with the original audio signal. The combined signal is watermarked with watermark data to be embedded. In a second embodiment, in case the original audio signal has parts of low signal energy, an alternative signal having a level or strength given by the psycho-acoustic model is watermarked with watermark data to be embedded, and the audio signal is watermarked with the watermark data to be embedded. The watermarked alternative signal is combined with the watermarked audio signal.
1. A method for watermarking successive sections of an audio signal, comprising:
calculating using a psycho-acoustical model a masking curve for a current section of said audio signal, and determining for said current section of said audio signal whether it contains low signal energy or parts of low signal energy;
providing an alternative signal different from said audio signal, which is controlled by said low signal energy determination and the strength of which is controlled by said masking curve;
combining said alternative signal with said audio signal in case said current section of said audio signal has low signal energy or parts of low signal energy, so as to provide a combined signal;
watermarking said combined signal, controlled by water-mark data to be embedded and by said masking curve, so as to provide a watermarked audio signal.
2. The method according to claim 1 , wherein said masking curve calculation and said low signal energy determination are performed in the frequency domain.
3. The method according to claim 1 , wherein said alternative signal is a white or pink noise signal.
4. The method according to claim 1 , wherein said watermark data to be embedded is a bit sequence selected from a set of pseudo-random bit sequences modulated according to a watermark information bit value.
5. The method according to claim 4 , wherein said bit se-quence is used for modulating the phase of the signals to be watermarked.
6. An apparatus for watermarking successive sections of an audio signal, said apparatus comprising:
a calculator using a psycho-acoustical model which calculates a masking curve for a current section of said audio signal, and which determines for said current section of said audio signal whether it contains low signal energy or parts of low signal energy;
a source which provides an alternative signal different from said audio signal, which is controlled by said low signal energy determination and the strength of which is controlled by said masking curve;
a combiner which combines said alternative signal with said audio signal in case said current section of said audio signal has low signal energy or parts of low signal energy, so as to provide a combined signal;
a watermarker which watermarks said combined signal, controlled by watermark data to be embedded and by said masking curve, so as to provide a watermarked audio signal.
7. The apparatus according to claim 6 , wherein said masking curve calculation and said low signal energy determination are performed in the frequency domain.
8. The apparatus according to claim 6 , wherein said alterna-tive signal is a white or pink noise signal.
9. The apparatus according to claim 6 , wherein said water-mark data to be embedded is a bit sequence selected from a set of pseudo-random bit sequences modulated according to a watermark information bit value.
10. The apparatus according to claim 9 , wherein said bit se-quence is used for modulating the phase of the signals to be watermarked.