| 摘要 |
<p>PURPOSE: To surely encipher video type information without giving any damage to pictures by individually shifting the time of at least several active information sections of a signal line by a prescribed amount from the timing base of the line. CONSTITUTION: One video information line is extended between the front edges of horizontal synchronizing signals of adjacent lines and provided with a color burst reference signal section and a following active video section. During an enciphering period, the time of the normal section of active videos is shifted in an advancing direction (approaching the horizontal synchronizing section of a prescribed line) or delaying direction (toward the horizontal synchronizing section of the succeeding line). Namely, the normal section is shifted by NT, where the T and N respectively represent the accurate one-cycle duration of the frequency of color subcarriers and a number selected out of the field of sets of -1, 0, and +1, from the preceding line of each specific line and the number N is pseudo-randomly generated. Therefore, video type information can be enciphered by only giving a negligible degree of damage to the picture quality.</p> |
