| 摘要 |
PURPOSE:To obtain the steady and high-quality screen by writing the pedestal level partially in case the video signal is written into the memory. CONSTITUTION:Output signal SB of video detection circuit 7 is applied to two field memories 9 and 10. In this case, the pedestal level is also written into memories 9 and 10 together with signal SB. Thus signal SB of the field to be written next is clamped with the pedestal level read out at the reading time. The writing contents of the preceding field is read out of memory 10 when the writing is given to the field of memory 9. And when the reading is over, the contents of memory 9 is read out next. This reading is carried out in several times as high as the writing speed in the horizontal direction. For writing of these memories 9 and 10, the synchronization is secured with the synchronous signal of signal SB and then with the synchronous signal of signal SA for the reading respectively. The signals read out of memories 9 and 10 are applied to mixer circuit 8 to be compounded to the fixed area of signal A. Circuit 8 fits signal B into the fixed area of signal A via control circuit 13 and based on the blanking signal. |
