| 摘要 |
<p>A keyer with variable shaping combines the benefits of a luminance keyer with those of a linear keyer using a single set of gain and clip controls. A key signal is input to a first amplifier (10) having a high gain that is variable over an upper portion of a gain control signal's range. The output of the first amplifier is compared (20) with a clip control signal and input to a second amplifier (30) having a low gain that is variable over a lower portion of the gain control signal's range. The second amplifier includes a feedback circuit (39) that provides minimum gain and shaping when the feedback signal is maximum, and provides maximum gain and shaping when the feedback signal is minimum. <IMAGE></p> |
