| 摘要 |
PURPOSE:To secure the process of the video signal with the flicker put out of the vision by carrying out the ciphering through the level inversion of the luminance signal based on the horizontal scanning period and thus fractionating the shift of the luminance level. CONSTITUTION:At the broadcasting station side, part of the video signal is inverted through the encoder to be transmitted, and the specified subscriber listens the received video signal through restoration via the decoder. In this case, the signal which is selected within each field based on the key code signal and within the horizontal scanning period is inverted at the side of the broadcasting station, and the code signal is transmitted in piling on the TV signal. The transmitted signal is received, the code signal is decoded through the decoder, and the inverted video signal is restored. In such system, the screen flicker caused by the difference among the parts used for the encoder and the decoder is limited to occur with every horizontal scanning period of the liminance level. Thus the flicker is averaged in a field to be put out of the vision. |
