| 摘要 |
<p>The invention teaches a method, means and apparatus for clamping a back porch interval of a video signal including clamping a sync-tip level of said video signal to a variable reference voltage (33), comparing a back-porch voltage level of the sync-tip clamped video signal to a predetermined reference voltage (22), generating an error signal (24) representative of the difference between the back-porch voltage level and the predetermined reference voltage (22), and adjusting the variable reference voltage (33) in response to the error signal (24) such that the error signal (24) is minimized.</p> |
