| 摘要 |
PURPOSE:To prevent a decoding error without destructing teletext data in a vertical blanking period of a video signal decoded in sinc shifting, in a video scramble decoder. CONSTITUTION:When a video signal processed in sinc shifting is inputted to a sinc shift decoding circuit 2, the sinc shift decoding is started by a sinc shifting pulse 29 generated by means of a key signal synchronizing with the video signal. A video signal 3 decoded in sinc shifting is inputted to a synchronizing separation circuit 8, an AFC signal 9 and a synchronizing separation signal 21 are outputted, the AFC signal 9 is hanged over to the key signal 16 after a certain period of time and inputted to a sinc shifting start point pulse generation circuit 26, the synchronization signal 21 is inputted to a sinc shifting end point pulse generation circuit 24, and the legal decoding in sinc shifting is performed in a sinc shifting decoding circuit 2 by the pulse 29 generated from the obtained start point and end point. Thus, the stability of the AFC does not affect the end point. |
