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 disturbanc e 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 cop y protected by briefly interrupting the writing of the information to an information carrier. The latter measure is also effective for copy protectin g software.