Patent ID: 7454327

Claim:
Method for introducing information into a data stream comprising data about spectral values representing a short-term spectrum of an audio signal, wherein a masking threshold used in generating the data stream as function of frequency for the short-term spectrum is present in the data stream as side information, comprising: processing the data stream to obtain the spectral values of the short-term spectrum of the audio signal; combining the information with a spread sequence to obtain a spread information signal, wherein the information includes information bits, and wherein the combining includes spreading the bits based on a spread spectrum modulation by combining the bits with the spread sequence; generating a spectral representation of the spread information signal to obtain a spectral spread information signal; establishing a psychoacoustic maskable noise energy as a function of the frequency for the short-term spectrum of the audio signal, wherein the psychoacoustic maskable noise energy is smaller or the same as the psychoacoustic masking threshold of the short-term spectrum by extracting the psychoacoustic masking threshold from the data stream, wherein the psychoacoustic maskable noise energy is the same as the psychoacoustic masking threshold; weighting the spectral spread information signal by using the established noise energy to generate a weighted information signal, wherein the energy of the introduced information is substantially equal to or below the psychoacoustic masking threshold; summing the weighted information signal with the spectral values of the short-term spectrum of the audio signal to obtain sum spectral values comprising the short-term spectrum of the audio signal and the information; and processing the sum spectral values to obtain a processed data stream comprising the data about the spectral values of the short-term spectrum of the audio signal and the information to be introduced.