Video signal processor employing edge replacement, preshoots and overshoots for transient enhancement

Claim 1

Video transition enhancement apparatus, comprising: a transition detector for detecting transients in a video input signal having a given transition period; a delay circuit having a center tap and a plurality of further taps disposed about said center tap responsive to said video input signal for providing a plurality of delayed replicas thereof; a pair of maximum and minimum selection switch circuits, each coupled to said taps, for providing respective output signals representative of the maximum value and the minimum value of the video signal present in the delay circuit; an output selector switch circuit, controlled by said transition detector, for coupling said center tap to an output terminal in the absence of a detected transition and, in response to a detected transition in a first sense, said output selector switch first couples the output of the minimum value selection circuit to the output terminal for substantially half the transition period and then couples the output of the maximum value selector to the output terminal for substantially half the transition period for producing a video output signal at said output terminal having a rapid transition in said first sense; said output selector switch being responsive to a detected transition in a second sense, for first coupling said output of said maximum value selector to the output terminal and then coupling the output of the minimum value selector to the output terminal thereby producing a video output signal having a rapid transition in said second sense; and circuit means for applying an offset signal of a first polarity, relative to said delayed replica at said center tap, to said maximum value selection switch circuit and for applying an offset signal of a second polarity to said output signal of said minimum value selection switch for producing pre-shoots and overshoots in said video output signal and for controlling the amplitude of said pre-shoots and overshoots.

Claim 6

A method for enhancing video transitions, comprising: detecting transitions of a video input signal and producing a control signal representative thereof; providing a plurality of delayed video signals; deriving maximum and minimum valued video signals from said delayed video signals; selectively coupling a given delayed video signal, said maximum valued video signal and said minimum valued video signal to an output in response to said control signal to produce a video output signal having an enhanced rise-time for said transitions of said video input signal; and adding a predetermined offset to each of said maximum and minimum valued video signals in a sense to produce a pre-shoot before each detected transition and to produce an over-shoot after each detected transition.

Claim 7

A method for enhancing video transitions, comprising: detecting transitions of a video input signal and producing a control signal representative thereof; providing a plurality of delayed video signals; deriving maximum and minimum valued video signals from said delayed video signals; selectively coupling a given delayed video signal, said maximum valued video signal and said minimum valued video signal to an output in response to said control signal to produce a video output signal having an enhanced rise-time for said transitions of said video input signal; and adding a predetermined offset to each of said maximum and minimum valued video signals in a sense to produce a pre-shoot before each detected transition and to produce an over-shoot after each detected transition.