Patent ID: 7555432

Claim:
A method of embedding data in a host audio signal, comprising: defining a set of frames of said host audio signal; for each frame, determining a plurality of masked frequencies, those being spectral points having a power level below a masking threshold for the frame; selecting the two most commonly occurring masked frequencies f 1 and f 2 in said set of frames of said host audio signal; modifying a representation of each frame, using an audio steganography processor, at said masked frequencies f 1 and f 2 in accordance with a desired value of data in the frame, said modification at f 1 and f 2 being performed in a complementary manner to embed a single bit value; excluding frames with less than a minimum number of spectral points having a power level below the masking threshold for the frame; and normalizing the sound pressure level of each frame prior to determining said masking threshold; wherein said masking threshold for each frame varies in level with frequency, and wherein said modifying includes obtaining a cepstrum of each frame and modifying the frame cepstrum to produce complementary changes of the spectrum at said masked frequencies f 1 and f 2 to correspond to a desired bit value.