ANTI-COPYING METHODS AND DEVICES FOR DIGITAL INFORMATION SIGNALS

摘要

In order to protect audio signals against copying, it is proposed to mix the audio signal with at least one non-audible disturbance signal. A first disturbance signal may be a low-frequency signal which is added to the audio signal, while a second disturbance signal may be a high-frequency disturbance signal which is multiplied with the audio signal. Additionally, the second disturbance signal may be modulated by a modulating signal comprising either the original or inverted orginal signal, or spoken messages indicative of an illegal copy. Additionally, or alternatively, digital information may be copy protected by briefly interrupting the writing of the information to an information carrier. The latter measure is also effective for copy protecting software.