JPS61292482A - Device for deciding existence/absence of video signal - Google Patents

Abstract

PURPOSE:To automatically decide the existence/absence of a video signal by detecting the synchronizing signal of a prescribed cycle included in the video signal and deciding the existence/absence of the video signal by the existence/ absence of the pulse output of a longer pulse duration than the cycle of the synchronizing signal based on the output of a detecting means. CONSTITUTION:The output of an one shot section 4 has a previously set constant so as to obtain an one shot output (c) of a pulse duration from the leading time of t0 to the trailing time of t2. When the one shot section 4 is triggered by the trailing of the first synchronizing signal, the output thereof is led as t0 in the figure c. When the trailing of the second synchronizing signal comes before the trailing of t2, the one shot section 4 is triggered, further the one shot output is outputted from the t1 of a c with the pulse duration based on the constant and a high level is maintained for a long period. By this repetition thereafter, while the video signal comes, the output of the one shot section 4 constantly goes to the high level. By deciding this High level by a digital processing section 5, the existence/absence of the video signal is decided and the video signal is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for determining the presence or absence of a video signal of a television, video equipment, or the like.

[Conventional technology]

In the above-mentioned television or video equipment, for example, when the radio waves of TV broadcasting are weak, that is, signals in a weak electric field, or noise signals after the video signal from the video equipment disappears, the intended original video signal is Although it is different from
Conventionally, there was no means to automatically determine these, and the received video signal was sent as is to the next processing section.

[Problem that the invention seeks to solve]

Therefore, in the past, if the signal was in a weak electric field or if it was a noise signal from the video equipment, the screen would be distorted, so the operator would judge that the video signal was gone and operate the equipment themselves to cut off the signal. The problem was that it had to be done.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to obtain a video signal presence/absence determination device that can automatically determine the presence or absence of a video signal and deal with it. be.

[Means for solving problems]

A video signal presence/absence determination device according to the present invention includes a detection means for detecting a synchronization signal of a predetermined period included in a video signal, and outputs a pulse having a pulse width longer than the period of the synchronization signal based on the output of the detection means. The apparatus includes a pulse output means and a determination means for determining the presence or absence of a video signal based on the presence or absence of a pulse output from the pulse output means.

[Effect]

In the present invention, the detection means detects the synchronization signal included in the video signal, and from the time the synchronization signal is detected, the pulse output means outputs a pulse having a pulse width longer than the period of the synchronization signal. Therefore, if a video signal is present and a synchronizing signal is detected periodically, the pulse output of the pulse output means will be continuous, and the determination means will determine the presence or absence of a video signal based on the presence or absence of this pulse output.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block configuration diagram of the embodiment. In the figure, 1 is an amplification unit that amplifies a video signal sent from the outside by a predetermined time, and 2 is a unit that detects a synchronization signal from the amplified video signal a. A reference voltage generating section 3a which is a detection means and generates a reference voltage Vref set between a reference level of a synchronization signal and a video signal level, and a reference voltage generation section 3a which is a detection means and which compares this reference voltage Vref with the video signal a to generate a synchronization signal. It is composed of a comparison section 3b to be taken out. Reference numeral 4 denotes a one-shot section which generates a one-shot output C by being triggered by the falling or rising edge of the synchronizing signal extracted above, and the pulse width of this one-shot output C is longer than the predetermined period of the synchronizing signal. The pulse output means of the present invention is configured to have a long pulse width.

Reference numeral 5 denotes a digital processing section that determines the presence or absence of a video signal based on the output from the one-shot section 4 and controls intermittent, switching, etc. of the video signal, and constitutes the determining means of the present invention.

Next, the operation of this embodiment will be explained with reference to the timing chart shown in FIG.

A video signal a, which is a video signal sent from the outside and amplified by the amplifying section 1, is processed by the comparing section 3b, and only the synchronizing signal is extracted. Here, as shown in FIG. 2, in order to extract the synchronization signal b (only horizontal synchronization pulses are shown in the figure) from the video signal a, the synchronization signal is set to a level that allows a stable synchronization signal to be obtained from the reference voltage generator 3a. reference voltage Vref
Then, the comparator 3b compares the level of the reference voltage Vraf and the video signal a to obtain a synchronizing signal (FIG. 2(b)).
get. The output of the one-shot unit 4, which is triggered by the fall or rise of the synchronization signal from the comparison unit 3b, is triggered by the first fall or rise of the synchronization signal, for example, as shown in FIG. 2(C). , the constant of the one-shot section 4 is set in advance so that a one-shot output C having a pulse width from the rising edge of 10 to the falling edge of t2 can be obtained as shown in FIG.

Now, when the one-shot section 4 is triggered by the first falling edge of the synchronization signal, its output rises as indicated by to in FIG. 2 (0). Next, the second fall of the synchronization signal or t2
The one-shot section 4 is retriggered, and the one-shot output described above is further output with a pulse width based on a constant from tl in FIG.
By repeating this process, the output of the one-shot unit 4 is always kept at the "High" level while the video signal is being received.
``By determining the level with the digital processing unit 5,
It determines the presence or absence of a video signal and controls the video signal.

As explained above, by determining the presence or absence of a video signal, for example, if there is a signal on one of two video signals, automatic switching can be performed, or when there is no TV broadcast signal, it can be used to control the power of the TV, etc. , its application range can be considered in various ways. Furthermore, by connecting or incorporating the device of the present invention into a personal computer, video equipment can be easily controlled.

〔Effect of the invention〕

As described above, the video signal presence/absence determination device of the present invention includes a detection means for detecting a synchronization signal with a predetermined period included in a video signal, and a pulse width longer than the period of the synchronization signal based on the output of the detection means. and determining means for determining the presence or absence of a video signal based on the presence or absence of a pulse output from the pulse output means, and automatically determines the presence or absence of a video signal based on the presence or absence of a synchronization signal. This has the advantage that it is possible to control intermittent, switching, etc. of video signals without bothering the operator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a timing chart showing signals of each part of the above embodiment. 2...Detection means, 3a...Reference voltage generation section, 3b.
... Comparison section, 4. One-sit section (pulse output means), 5. Digital processing section (judgment means). Note that the same reference numerals are used for the middle part of the figure or corresponding parts. Agent Masuo Oiwa (and 2 others) Figure 1 Figure 2

Claims (1)

[Claims] detection means for detecting a synchronization signal with a predetermined period included in the video signal; pulse output means for outputting a pulse having a pulse width longer than the period of the synchronization signal based on the output of the detection means; 1. A video signal presence/absence determining device comprising: determining means for determining the presence or absence of a video signal based on the presence or absence of a pulse output.