Synchronization pulse detection circuit

A method for detecting horizontal synchronization pulses of a sequence of video signals, each one of the video signals having video information subsequent to the horizontal synchronization pulse, such horizontal synchronization pulse having a substantially non-time varying tip portion disposed between a pair of substantially time varying transition portions, such method comprising:

• producing a level_detection signal in response to a comparison between actual time variations in the video signal and a predetermined time variation criterion representative of the tip portion of the horizontal synchronization pulse;
• producing, in response to the level_detection signal, a transition_detection signal in response to a comparison between actual time variations in the video signal and a predetermined time variation criterion representative of the transition portion of the horizontal synchronization pulse;
• producing, in response to the level_detection and transition_detection signals, output pulses when such comparisons indicate the level_detection and transition detection signals meet the criteria;
• determining time duration between output pulses and comparing such time duration with a predetermined time duration representative of the expected time duration of the video signal;
• determining a minimum value of the video signal for each one of the video signals and for determining whether the determined value representative of the level portion of one of the video signals is within a predetermined window about the lowest determined value of a preceding one of the video signals;
• and
• producing a sync pulse in response to the determined time duration and the determined minimum value.

A system for detecting horizontal synchronization pulses of a sequence of video signals, each one of the video signals having video information subsequent to the horizontal synchronization pulse, such horizontal synchronization pulse having a substantially non-time varying tip portion disposed between a pair of substantially time varying transition portions, such system comprising:

• a detector for producing a first detection signal in response to a comparison between actual time variations in the video signal and a predetermined time variation criterion representative of the one of the substantially non-time varying and substantially time varying portions of the horizontal synchronization pulse;
• a discriminator responsive to first detection signal for producing a second detection signal in response to a comparison between actual time variations in the video signal and a predetermined time variation criterion representative of the other one of the substantially non-time varying and substantially time varying portions of the horizontal synchronization;
• a processor responsive to the first detection and second detection signals for producing output pulses when such comparisons indicate the first detection and second detection signals meet the criteria;
• a time evaluator for determining time duration between output pulses and for comparing such time duration with a predetermined time duration representative of the expected time duration of the video signal;
• an amplitude evaluator responsive to the video signals for determining a minimum value of the video signal for each one of the video signals and for determining whether the determined value representative of the level portion of one of the video signals is within a predetermined window about the lowest determined value of a preceding one of the video signals;
• and
• a synchronization pulse generator for producing a sync pulse in response to the time evaluator and the amplitude evaluator.

A system for detecting horizontal synchronization pulses of a sequence of video signals, each one of the video signals having video information subsequent to the horizontal synchronization pulse, such horizontal synchronization pulse having a substantially non-time varying tip portion disposed between a pair of substantially time varying transition portions, such system comprising:

• a shape detector for producing a level_detection signal in response to a comparison between actual time variations in the video signal and a predetermined time variation criterion representative of the tip portion of the horizontal synchronization pulse;
• a transition discriminator responsive to level_detection signal for producing a transition_detection signal in response to a comparison between actual time variations in the video signal and a predetermined time variation criterion representative of the transition portion of the horizontal synchronization pulse;
• a processor responsive to the level_detection and transition_detection signals for producing output pulses when such comparisons indicate the level_detection and transition detection signals meet the criteria;
• a time evaluator for determining time duration between output pulses and for comparing such time duration with a predetermined time duration representative of the expected time duration of the video signal;
• an amplitude evaluator responsive to the video signals for determining a minimum value of the video signal for each one of the video signals and for determining whether the determined value representative of the level portion of one of the video signals is within a predetermined window about the lowest determined value of a preceding one of the video signals;
• and
• a synchronization pulse generator for producing a sync pulse in response to the time evaluator and the amplitude evaluator.