| 摘要 |
The method involves all the bits of the message being encoded by effecting a high pass filtering (F1) of two elementary audio signals (S1, S2) corresponding to two adjacent time ranges of equal duration of an initial audio signal (SA1). The high frequency component ( DELTA 2) of one of the two elementary audio signals is replaced by the high frequency component ( DELTA 1) of the other elementary audio signal which is modulated in sign as a function of the logical value of the bit. In this way the initial audio signal (SA1) is modified, thus forming the audio carrier signal (SA4) which contains the message. All bits of the message are filtered to obtains two elementary audio signals (S1, S2), and two high frequency intermediate signals ( DELTA 1, DELTA 2), and it is possible to derive a modified elementary audio signal (SM2) obtained from the difference between one of the elementary audio signals (S2) and its associated intermediate signal ( DELTA 2).
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