JPH0723250A - Input composite video signal detection method for synchronous coupling - Google Patents

Abstract

(57) [Summary] [Purpose] The synchronization signal generator GL ON / OFF control is O
Even if noise is mixed in the input when there is no input GL signal at N, malfunction due to this noise can be prevented. [Structure] The sync signal obtained by sync separation from the input composite video signal is compared with the delayed sync signal obtained by delaying the main sync signal by one horizontal sync period (63.5 μsec in the case of NTSC), and this phase comparison signal is compared. With a retrigger / multivibrator circuit, a positive DC signal is obtained when the phases match,
When the phases do not match, try to obtain the DC of the ground potential,
This retrigger multivibrator circuit output and the command signal of synchronous coupling ON are passed through the AND circuit, and the phase comparison output is +
Only when there is a synchronous coupling ON command signal at 5V, the synchronous signal generator is in the synchronous coupling mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a video signal for input synchronization coupling of a color television synchronization signal generator.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example. 301 is an amplifier,
Reference numeral 302 is a DC reproducing unit, 303 is a comparator unit that separates only the synchronizing signal from the video signal (VBS), and 304 is a gate unit. The input composite video signal is amplified by the amplifying unit 301, the pedestal level of the VBS signal is fixed at the DC potential in the DC reproducing unit 302, compared with the reference potential in the next comparator 303, sliced, and only the synchronization signal is obtained. Become. This synchronization signal is suppressed in the next gate unit 304 so as to be output to the gate output when the GL (genlock) ON / OFF command is GL / ON, and is input to the synchronous coupling circuit. In the sync signal generator, an input cable is connected to the GL input signal plug, and when synchronous coupling is required, GL input signals such as in-office black burst and color bar signals are connected to this cable for GL. GL ON / OFF
The command is normally in the GL ON state. The problem here is that when noise etc. is input to the input cable, G
Although the L input signal is not input, this noise may be detected as a video input signal by the sync signal generator. For this reason, this noise causes a disturbance in the output signal of the synchronization signal generator, causing the next-stage device (camera, switcher, etc.) to malfunction, resulting in an abnormal image. The sync separation amplifier of the sync signal generator must sufficiently amplify so that the sync of the input video signal can be separated even if the sync component is 0.1 Vp-p or less. In addition, the band limitation is performed to prevent noise malfunction, and noise malfunction occurs. Is prevented, but is insufficient.

[0003]

As described above, the prior art has drawbacks of malfunction due to noise. The present invention eliminates these drawbacks, and an object of the present invention is to stably synchronize the synchronization signal generator. .

[0004]

In order to achieve the above-mentioned object, the present invention has a periodicity (pulses are every 63.5 μs) in a sync signal separated from a sync coupling video signal. By utilizing the fact that the noise that jumps into the cable when there is no signal input has no periodicity, both are selected, and the synchronous signal generator is set to the synchronous coupling mode only when the GL input signal is normal. is there.

[0005]

[Function] The normal sync signal after sync separation is delayed by 1H (63.5 μsec), the phase is compared with that of the sync signal before delay, a comparison pulse is generated, and a retrigger / multivibrator (hereinafter referred to as retrigger multi) is generated by this comparison pulse. ) When the circuit is operated and there is a comparison pulse, the retrigger multi-circuit output is set to plus (+ 5V), and when there is no comparison pulse, the retrigger multi-circuit output is set to 0V. Since there is no periodicity when noise is input, the retrigger multi-circuit output is always 0 V, and the synchronous coupling part of the synchronous signal generator is set to GL / OFF to prevent noise malfunction.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 101 to 104 are the same as 301 to 304 in FIG. Reference numeral 105 is a 1H delay unit, 106 is an AND circuit unit, 107 is a retrigger multi-circuit unit, and 108 is an AND circuit unit. 2a-f
1 is a waveform chart of each point in FIGS. GLVBS
The signal is sufficiently amplified by the amplification unit 101, and the direct current regeneration unit 1
The pedestal level is DC-reproduced at 02, and compared with the reference voltage at the comparator unit 103, and sliced to obtain a synchronization signal. (FIG. 2-b) The 1H delay unit 10 outputs the main synchronization signal.
5 is made 1 HDL, the phase is compared by the AND circuit 106 of the next stage, and the retrigger multi-circuit unit 107 is driven by the phase matching pulse. As shown in FIG. 2d, when there is a phase matching pulse, a positive (+5 V) output voltage is obtained. Become. This signal and GL
ON / OFF command GL ON signal and AND circuit 10
An AND is taken at 8, and the gate of the gate circuit 104 is opened by this AND output signal to output a stable synchronous separation output. When the GLON command is GLON and there is no input signal and noise jumps into the input cable, there is no phase matching pulse in the output of the AND circuit 106 because there is no periodicity in the noise. Since the output of the unit 107 is always 0, the pseudo sync signal due to noise is not output, and the operation is stable.

[0007]

According to the present invention, the synchronizing signal generator GL is provided.
Even if noise is mixed in the input when the ON / OFF control is ON and there is no input GL signal, malfunction due to this noise can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a waveform of each point in FIG.

FIG. 3 is a block diagram showing a conventional embodiment.

[Explanation of symbols]

 101, 301 Amplifying section 102, 302 DC regenerating section 103, 303 Comparator section 104, 304 Gate section 105 1HDL section 106 AND section 107 Retrigger multi section 108 AND section 109 Gate section

Claims (1)

[Claims] 1. A synchronizing signal generator, wherein a synchronizing signal obtained by synchronizing separation from an input composite video signal and a main synchronizing signal are one horizontal synchronizing period (63.5 μsec in the case of NTSC).
Phase comparison of the delayed delayed synchronization signals, and this phase comparison signal is obtained by the re-trigger multivibrator circuit when a positive DC signal is obtained when the phases match, and when the phases do not match, DC of the ground potential is obtained. This retrigger multivibrator circuit output and the command signal of synchronous coupling ON are passed through the AND circuit, the phase comparison output is + 5V, and synchronous coupling ON.
An input composite video signal detection method for synchronous coupling, characterized in that the synchronous signal generator sets the synchronous coupling mode only when there is a command signal.