Noise elimination device for the detection of the vertical sync pulse in video signals

• US 20090190032A1
• Filed: 06/30/2005
• Published: 07/30/2009
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Dynamic Data Technologies LLC
• Original Assignee: Entropic Communications Incorporated (Maxlinear Incorporated)
• Inventors: Hackmann, Hartmut, Pletz-Kirsch, Gerhard, Boehme, Siefried
• Granted Patent: US 8,068,176 B2
• Time in Patent Office: Days
• US Class Current: 348/537
• CPC Class Codes: H04N 5/10 Separation of line synchronising signal from frame synchronising signal or vice versa

Abstract

In order to create a noise elimination device for the detection of the vertical sync pulse in video signals, which has a very fast locking behavior and in which additional components can be integrated easily, which components can measure fundamental parameters of the underlying composite video signal, it is proposed that the device comprises a vertical pulse detector (12), which detects successive vertical sync pulses in the composite video signal and a VPLL (vertical phase locked loop), which comprises at least a phase detector (18) that produces a phase error, at least a loop filter (20), at least an oscillator (16) on which the output signal of the vertical pulse detector is present as an input signal and which oscillator produces a clock signal phase-synchronized with the input signal, whereas the oscillator (16) is a counter which counts with an approximately constant clock frequency, while the length of an oscillation period of the oscillator (16) is determined by the change in its count due to a correction value produced by the loop filter.

Claims

1. A noise elimination device for the detection of the vertical sync pulse in a composite video signal, comprising a vertical pulse detector, which detects successive vertical sync pulses in the composite video signal and a VPLL (vertical phase locked loop) comprising at least a phase detector producing a phase error, at least a loop filter and at least an oscillator, on which the output signal of the vertical pulse detector is present as an input signal and which produces a clock signal phase-synchronized with the input signal,

characterized in that the oscillator is a counter which counts with an approximately constant clock frequency, while the length of an oscillation period of the oscillator is determined by the change in its count due to a correction value produced by the loop filter.

2. A device as claimed in claim 1, characterized in that the phase detector comprises a phase stroboscope which measures the counts at which the vertical sync pulses occur and calculates phase errors from them, and a minimum finder which calculates the phase error with the lowest absolute value.

3. A device as claimed in claim 1, characterized in that the loop filter comprises a proportional part which outputs a component proportional to the phase error and an integral part which outputs a component proportional to a value stored in an integrator register.

4. A device as claimed in claim 1, characterized in that at the beginning of a new locking procedure, the first correction value equals the phase error measured during the first period and the second correction value equals double the phase error measured during the second period.

5. A device as claimed in claim 1, characterized in that the clock frequency of the oscillator is the half-line frequency of the composite video signal.

6. A device as claimed in claim 1 characterized in that the change in the count takes place approximately at the middle of the period of the oscillator.

7. A device as claimed in claim 1, characterized in that the device comprises means for detection of alternating field lengths and a window-based device for detection of vertical sync pulses so that in the event that alternating field lengths are detected, there is a switchover from the VPLL to the window-based device.

8. A device as claimed in claim 1, characterized in that the device comprises means for detection of the fundamental frequency of the composite video signal.

9. A device as claimed in claim 1, characterized in that the device comprises means for detection of standard field lengths.