FIELD: method and device for inserting additional data in signal. SUBSTANCE: proposed method and device are intended for superposing shielding marks onto audio and video signals. Signal is coded by means of coder incorporating feedback circuit to control coding process, such as differential pulse-code modulated coder or (sigma-) delta modulator. Shielding mask is introduced by modifying coded-signal assigned samples. Modification is effected until feedback is applied to coded signal with the result that sampling errors brought in due to introduction of shielding mark are eliminated during next coding operations. In addition one or more samples preceding assigned ones are also modified so that error brought in by shielding mark is additionally reduced. This effect is attained due to anticipatory retrieval of sample (or combination thereof) whose modification yields best coding characteristics by reducing noise with respect to signal noise. EFFECT: improved coding characteristics. 15 cl, 16 dwg
