| 摘要 |
PROBLEM TO BE SOLVED: To provide an acoustic digital watermark system that secures the communication speed of parallel information, secures the reliability of communication, and maintains audio quality without necessarily going through a digital communication path.SOLUTION: An acoustic digital watermark system includes: a first inverse filter that finds a first residual signal by filtering an input acoustic signal by using an FIR filter treating a first linear prediction coefficient, i.e. a linear prediction coefficient for an input acoustic signal as a filter coefficient; a first carrier wave generation unit that generates, as a first carrier wave, a sine wave which is N times a first fundamental frequency, i.e. a fundamental frequency of the first residual signal; a first phase modulation unit that obtains a modulation wave by phase-modulating the first carrier wave with parallel information so that a symbol rate is M times a pitch frequency; an addition unit that obtains a first signal by adding the modulation wave and the first residual signal; and a synthesis filter that obtains a reproduction signal by filtering the first signal by using an IIR filter treating the first linear prediction coefficient as a filter coefficient.SELECTED DRAWING: Figure 3 |
