JPS6155833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video switch in an industrial television system.

More specifically, conventional switches of this type can be roughly divided into so-called manual video switching devices operated by manual switch operation, and automatic video switching devices controlled by cyclic control input. This is related to the switching device.

Typically, an automatic video switcher switches video at the same time a cyclic control input is applied. Therefore, when the video signal inputs are asynchronous with each other, one screen is often flowed vertically on the video monitor each time the video is switched.

Automatic video switching devices usually automatically switch the video one after another at approximately 10 second intervals, which can be an eyesore for observers and even cause eye fatigue during long-term operation.

In the prior art, as a means to solve this problem, a method of externally synchronizing each television camera that is a video input source, or a method of introducing a frame synchronizer has been used.

However, in the case of external synchronization, a synchronization signal generator is required, and a cable for transmitting the synchronization signal must be laid, which is disadvantageous in terms of economy.

Furthermore, frame synchronizers have the disadvantage of not only being economical but also requiring specialized skills for maintenance.

An object of the present invention is to provide an economical video switching method that can prevent transient disturbances in vertical synchronization when switching videos.

In order to achieve the above object, the video switching method according to the present invention uses the vertical synchronization signal of the video signal output from the video switcher as a reference in the video switching method of a video switcher that switches and selects a plurality of mutually asynchronous video signal inputs. , the video switching device is configured to switch when the phase difference of the vertical synchronization signal of the video signal to be switched next falls within a predetermined range in order to prevent disturbances on the screen when switching the video. .

According to the above method, smooth video switching is possible, and the object of the present invention can be completely achieved.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system diagram around an automatic video switching device in an industrial television system configured according to the method of the present invention.

In the figure, 1a to 1j are television cameras, and the video signals of these 10 television cameras are 10
An input-to-two output video switch 2 is supplied.

Assuming that the 10-input to 2-output video switching device 2 is configured so that the camera video signal 1a is selected for the output row 1 and the camera video signal 1b is selected for the output row 2 at the time of initial setting, first the video of the camera 1a is selected. The signal is received by a video monitor 4 via a video distribution amplifier 3. Further, the video signal of the camera 1a passes through a video clamper 5a, and a composite synchronization signal is separated and extracted by a synchronization separation circuit 6a.

7a is an integrating circuit which separates and extracts only the vertical synchronizing signal from the composite synchronizing signal.

The pulse width of the extracted vertical synchronization signal is expanded by the monostable multivibrator 8.
Here, this pulse signal will be referred to as a reference vertical synchronization signal.

On the other hand, at the time of initial setting, the video signal of the camera 1b to be selected as the next video monitor is supplied to the video clamper 5b input. The signal passes through a synchronization separation circuit 6b and an integration circuit 7b, and a vertical synchronization signal of the camera 1b is extracted.

Reference numeral 9 denotes an AND circuit, which sends out a logic output when the reference vertical synchronization signal and the vertical synchronization signal of the camera 1b match in phase.

FIG. 2 is a waveform diagram showing the above operation. In the figure, the vertical axis of each waveform represents the output level, and the horizontal axis represents the time t, where a represents the output of the integrating circuit 7a, b represents the output of the monostable multivibrator 8,
c is the output of the integrating circuit 7b, d is the inverter 10
, and e indicates the output of the AND circuit 9, respectively. The reference vertical synchronization signal width of the monostable multivibrator 8 determines a specific range of the phase difference between the vertical synchronization signal in the current image and the vertical synchronization signal of the camera to receive the next image.

In other words, it is determined by considering the state of the shock at the time of adjusting or switching the vertical hold. For example, the pulse interval of the output of the integrating circuit 7a is set to 16.7 ms.
(60Hz), it is possible to set it to either 2ms or 5ms considering the above-mentioned factors.

The vertical phase matching signal obtained in this way is
A total of 10 outputs are obtained by the fan-out circuit 11.

Next, the circuit 12' shown at the top of the figure is a timing signal circuit for automatic cyclic switching of the 10-input to 2-output video switching device 2. In this circuit, 12 is a clock pulse generator, and its output is converted into binary coded decimal (BCD) through a counting circuit 13.
It drives the counting circuit 14.

15 is a BCD→decimal decoder, which provides a 10-cycle progressive logic output.

This walking force is at the time of initial setup.
A logic output is set to appear at the output a of the BCD→decimal decoder 15, and the logic output is held for the step setting time.

As an example, assume that it is held for 10 seconds.

Reference numeral 16a denotes an AND circuit, which is logically controlled by the output of the fan-out circuit 11 when a logical output appears at the output a of the BCD→decimal decoder 15.

That is, at the moment when the vertical phase difference between the initialized television cameras 1a and 1b falls within a specific range, a logical output is sent, and the video signals of the television cameras 1a and 1b are sent to the 10-input to 2-output video switch 2. Provides a switching control signal for simultaneous selection.

However, at the time of initial setting, the video signals of the TV cameras 1a and 1b have already been selected, and the video signals of the TV camera 1a and the TV camera 1b are output to the output row 1 and output row 2 of the video switch 2, respectively. Therefore, no change in control occurs.

In other words, the video signals of the television cameras 1a and 1b continue to be output. In this way, the video signal is selected for 10 seconds after the initial set.

Next, 10 seconds after the initial setup,
The BCD→decimal decoder 15 logically increments to b, and the AND circuit 16b is logically controlled by the output of the fan-out circuit 11.

That is, the logical control output is sent out at the moment when the vertical phase difference between the television cameras 1a and 1b falls within a specific range, and the television camera 1b is output to the output column 1 of the video switching device 2, and the output column 2 of the video switch 2 is output. The video signal of the television camera 1c is instantly switched and selected.

As a result, the switched video of the television camera 1b can be obtained on the video monitor 4 without causing vertical synchronization disturbance.

Through such a process, 1a→1b→1c...→1i, 1j→1a... at approximately constant time intervals.
...→ Smooth TV camera image switching can be achieved in the order of →.

Although an example of an embodiment constructed based on the method of the present invention has been described above, the present invention can be applied to a wide range of general industrial television systems, such as security monitoring in banks and security monitoring in various stadiums.

Note that since the present invention performs video switching at a timing when the vertical phases of the asynchronous video signals almost match, it is desirable that there be an appropriate scanning frequency difference between the video signals.

For example, if the video signal source is a 2:1 interlaced internally synchronized camera that conforms to the Japanese standard television system, and the horizontal scanning frequency difference between them is 200Hz, the maximum required time is required for the vertical phases to match. The time will be approximately 1.3 seconds.

This means that when the automatic switching interval of the video signal is set to 10 seconds, the actual switching interval will drift by about 1.3 seconds.

Therefore, the larger the horizontal frequency difference between the input video signals, the less the drift in the automatic video switching interval.

From the standpoint of system functionality, a slight drift in the automatic video switching interval is not a problem.

As explained above, the video switching method according to the present invention prevents transient disturbances in vertical synchronization and achieves smooth video switching without using external synchronization methods or frame synchronizers, which have problems in terms of economy and other factors as in the past. It can be made possible.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the automatic video switching device in an industrial television system according to the present invention, and FIG. 2 is a signal waveform diagram useful for understanding the system shown in FIG. 1a to 1j...TV camera, 2...10 input to 2 output video switcher, 3...video distribution amplifier, 4...
...Video monitor, 5a, 5b...Video clamper, 6
a, 6b... Synchronous separation circuit, 7a, 7b... Integrating circuit, 8... Monostable multivibrator, 9...
AND circuit, 10... Inverter, 11... Fan-out circuit, 12... Clock pulse generator,
13...Counting circuit, 14...Binary coded decimal (BCD) counting circuit, 15...BCD→decimal decoder.

Claims (1)

[Claims] 1. In the video switching method of a video switcher that switches and selects multiple mutually asynchronous video signal inputs, the vertical synchronization signal of the video signal output from the video switcher is used as a reference,
A video switching method configured to switch the video switching device when the phase difference of the vertical synchronization signal of the video signal to be switched next falls within a predetermined range so as not to cause disturbances on the screen when switching the video. .