Patent ID: 7379878

Claim:
An information encoding apparatus for encoding information and recording the encoded information onto a computer-readable medium, the apparatus comprising: converting means for converting an input signal into a spectrum signal; removing means for removing the spectra of frequencies having levels below a minimum audible level curve among spectra converted by the converting means; first determining means for determining whether predetermined first frequency spectrum level and second frequency spectrum level are both above the minimum audible level curve; second determining means for determining whether one of the first frequency spectrum level and the second frequency spectrum level is below the minimum level if the first and second frequency spectrum levels are switched after the first determining means determines that the first frequency spectrum level and the second frequency spectrum level are both above the minimum audible level curve; adding means for adding information by controlling to switch or not to switch the spectra on the basis of the information to be added if the second determining means determines that one of the first frequency spectrum level and the second frequency spectrum level is below the minimum audible level curve when the first and second frequency spectrum levels have been switched; and encoding means for encoding a spectrum to which information has been added by the adding means.