| 摘要 |
<p>In a video signal character converting device, a sampling window signal generator (53) generates a signal for sampling an input video signal 'a'. An amplitude discrimination circuit (51) samples the video signal in response to the sampling signal, detects a change in picture level either field by field or frame by frame based on an integrated value for every duration of vertical scanning, and outputs a resetting pulse when the change in picture level exceeds a predetermined level. A periodicity discrimination circuit (52) measures a time interval between two successive resetting pulses, and outputs a control signal if the time interval is shorter than a predetermined period of time. A conversion circuit (54) converts a video scene in response to the control signal. The video signal character converting device of the present invention determines as to whether or not the input video signal has video images that present an adverse effect mentally and physically to viewers, by observing a picture level and periodicity of the video signal in this manner. The device is thus able to display harmless video images by converting them into a harmless level with a process of reducing contrast or blanking, if it determines the video images harmful.</p> |
