Sync separator with a look-ahead clamp
AssigneeThe Grass Valley Group, Inc.
InventorBirney D. Dayton
Life of this patent
Estimating the term…
Abstract
An apparatus and method for precise separation of synchronizing information from a color television signal is described. Synchronizing signals are separated from the input video and used in a sample-and-hold circuit as the sampling pulses. The input video is sampled during the duration of the sync pulse. The sample is inverted and fed to a summing point where it is summed with a delayed version of the input video. A null is produced at the summing point during the duration of the input sync pulse. Since the input video to summing point has been delayed, the clamp null at the summing point begins during the front porch of the horizontal line interval allowing the leading edge of sync to be picked off very accurately by a sync separating comparator.
Claims23
A sync separator comprising:
- first means for separating a sync signal from an input composite video signal;
- first means for receiving and delaying said input composite video signal;
- a sample-and-hold circuit coupled to said first separating means and said first receiving and delaying means, the output of said sample-and-hold circuit being a sample of said delayed composite video signal;
- second means for receiving and delaying said input composite video signal coupled to a summing point;
- an inverter coupled to receive and invert said sample, the output of said inverter being coupled to said summing point;
- and
- second means for separating a sync signal coupled to receive the output of said summing point.
A sync separator comprising:
- first means for separting a sync signal from an input composite video signal;
- first means for receiving and delaying said input composite video signal;
- a sample-and-hold circuit coupled to said first separating means and first receiving and delaying means, the output of said sample-and-hold circuit being a sample of said delayed composite video signal;
- second means for receiving and delaying said input composite video signal coupled to a summing point;
- an inverter coupled between said second receiving and delaying means and said summing point for inverting said input composite video signal;
- and
- second means for separating a sync signal coupled to receive the output of said summing point.
A method for accurately separating a synchronizing signal from a composite video signal, comprising the steps of:
- (a) separating the synchronizing signal from the output signal to derive a sampling pulse;
- (b) utilizing said sampling pulse in a sample-and-hold circuit to obtain a sample of the input composite video signal;
- (c) delaying the input composite video signal;
- (d) inverting the output of said sample-and-hold circuit and combining it at a summing point with said delayed input composite video signal to produce a clamp null during the front porch of the horizontal interval of said input composite video signal;
- and
- (e) separating the synchronizing signal from the output of said summing point.
A sync separator comprising:
- first means for separating a sync signal from an input composite video signal;
- a sample-and-hold circuit coupled to receive the output of said first separating means and to also receive said input composite video signal, the output of said sample-and-hold circuit being a sample of said input composite video signal;
- means for receiving and delaying said input composite video signal coupled to a summing point;
- an inverter coupled to receive and invert said sample, the output of said inverter being coupled to said summing point;
- and
- second means for seprating a sync signal coupled to receive the output of said summing point.
A sync separator comprising:
- first means for separating a sync signal from an input composite video signal;
- a sample-and-hold circuit coupled to receive the output of said first separating means and to also receive said input composite video signal, the output of said sample-and-hold circuit being a sample of said input composite video signal;
- means for receiving and delaying said input composite video signal coupled to a summing point;
- an inverter coupled between said receiving and delaying means and said summing point for inverting said input composite video signal;
- and
- second means for separating a sync signal coupled to receive the output of said summing point.
Dependencies are inferred from the claim text.