| 摘要 |
PURPOSE:To avoid the erasion of a black and vertically long line by inhibiting a white-level memory having a drop-down in response to an input video signal from being set under a drop-down state longer than a white-level memory which has no drop-down. CONSTITUTION:The input video signals V are compared 8-1-8-3 through comparators and supplied to an up-down logic (u/d)10. Then the (u/p)10 is carried out for each fixed period by the output, and the white level drops gradually and stored 5 by a white-level follower logic 6. While a white-level memory 14 holds the white level which is clamped continuously by an (u/p) logic 18 via a white-level follower logic 15. This white level is set down by 10% by a 10%- down logic 13 and fed to a selecting circuit 12 to prevent the value of the logic 6 from being set at <=10% down level. This avoid the erasion of the black and vertically long line. |
