| 摘要 |
PURPOSE:To enable chroma erasing completely, by generating a cancell subcarrier by making it follow to the change in the hue and chroma variation of the chroma- key back part. CONSTITUTION:A chroma-key signal from an input terminal 4 is applied to a sample pulse generator 5 and an NTSC signal from an input terminal 6 is applied to a BPF7 to pick up a subcarrier component. The subcarrier of a chroma-key back part is applied to an input terminal 8 and it is applied to a 90 deg. delay device 10, multiplier 11 and gain control circuit 12 via a phase adjusting circuit 9. The output of a multiplier 13 is applied to a phase adjusting circuit 9 as a control voltage. Further, the output of the multiplier 11 is applied to the gain control circuit 12 as a control voltage via a sample hold circuit 15. |
