Fade-to-black video signal processing apparatus

Claim 1

Fade-to-black video signal processing apparatus comprising: a. input terminals adapted to receive input video signals having horizontal and vertical blanking intervals, picture intervals therebetween and synchronizing pulses during said blanking intervals; b. means coupled to said input terminals and responsive to said synchronizing pulses to provide horizontal and vertical blanking interval pulse signals timed to be in synchronism with said horizontal and vertical blanking intervals of said input video signals; c. a source of adjustable direct current control signal; d. switching means coupled to said source of adjustable direct current control signals and to said means providing horizontal and vertical blanking interval pulse signals to provide a predetermined first output level during the time of said horizontal and vertical blanking interval pulse signals and a second output level during the time between said horizontal and vertical blanking interval pulses which is a function of said adjustable direct current control signal; and e. an analog multiplier, coupled to said input terminals and to said switching means, for providing output video signals which are the product of said input video signals and the output levels from said switching means such that said analog multiplier exhibits a predetermined gain during the time of said horizontal and vertical blanking interval pulse signals and a gain determined by said adjustable direct current control signal during the time between said horizontal and vertical blanking interval pulse signals; and wherein said means to provide blanking interval pulse signals comprises: a. a sync separator having an input coupled to said input terminals and an output to provide separated synchronizing pulses in response to said synchronizing pulses; b. trigger generating means having an input coupled to said output of said sync separator and having an output to provide triggering pulses in response to pulses supplied to its said input which are shorter in duration than the horizontal synchronizing pulses in said input video signals; c. a first one-shot having a trigger input coupled to said output of said trigger generating means and having an output to provide regenerated vertical blanking interval pulses, each of said regenerated vertical blanking interval pulses being provided by said first one-shot being placed into its unstable logic state in response to one of said trigger pulses and returning to its stable logic state after a duration selected to be equal in length to one of said vertical blanking intervals; d. a second one-shot having a trigger input coupled to said output of said sync separator and having an output to provide regenerated first partial horizontal blanking interval pulses, each of said regenerated first partial horizontal blanking interval pulses being provided By said second one-shot being placed into its unstable logic state in response to an edge of a particular separated horizontal synchronizing pulse and returning to its stable logic state after a duration selected to be equal to that of the remainder of the horizontal blanking interval in which the immediately aforesaid particular separated horizontal synchronizing pulse occurs; e. a third one-shot having a trigger input coupled to said output of said sync separator and having an output to provide regenerated second partial horizontal blanking interval pulses, each of said second partial horizontal blanking interval pulses being provided when said third one-shot is returned to and in its stable logic state, said third one-shot being placed into its unstable logic state in response to an edge of a particular separated horizontal synchronizing pulse and returning to its stable logic state after a duration selected to be equal to that of the remainder of the horizontal blanking interval in which the immediately aforesaid particular separated horizontal synchronizing pulse occurs plus the ensuing picture interval; and f. first pulse combining means having first, second and third inputs each coupled to respective separate ones of the outputs of said first, said second and said third one-shots and having an output maintained in one logic state when any of said regenerated vertical blanking pulses, said regenerated first partial horizontal blanking pulses and said second partial horizontal blanking pulses are formed and in a second logic state when they are all absent, said output of said first pulse combining means thereby providing said horizontal and vertical blanking interval pulse signals.