Method and apparatus for recovering synchronizing signals in scrambled television pictures

摘要

Suppressed synchronizing signals of a scrambled standard TV picture are recovered and the picture unscrambled by a method including the steps of: separating a video portion having suppressed sync signals from an audio portion of a TV picture at an intermediate frequency level, amplifying the video portion through a gain controlled amplifier, selectively compensating for the suppressed levels of sync signals, passing the video portion with recovered sync signals of the TV picture through a demodulator, and providing a feedback signal from the demodulator to the gain controlled amplifier to automatically control its gain and thereby minimize artifacts in the TV picture after sync recovery. This new method is easily carried out by apparatus using only a few standard circuit components which can be manufactured as an application specific integrated circuit (ASIC).