| 摘要 |
<p>A clamp (18) combines a video signal, which may be a digitzed video signal, with a DC offset to clamp the back porch portion of the video signal to a predetermined level, for example, an IRE level. A divider responsive to the clamp generates a reference signal (BACK PORCH REF) having values indicative of IRE levels of the back porch portion prior to being clamped. In an adaptive sync slicer (20), a summer generates slice level values indicative of a numerical relationship, for example, an average, of the reference signal values and a fixed value; and, a comparator generates a composite synchronizing signal by comparing the video signal to the slice level values. A limiter may be used to restrict the range of the slice levels. The clamp, summer, comparator and limiter may be digital circuits. <IMAGE></p> |
