JP2000078487A - Video signal switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable display while suppressing synchronizing disturbance on a television monitor in the case of switching mutually asynchronous plural video signals. SOLUTION: Mutually asynchronous plural video signals A-H inputted to video signal input means 8a-8h are switched with the output of a control means 11 by a video signal selecting means 2. Until the television monitors pulls the synchronizing signals of switched video signals and sub carrier wave, the video signals are fixed at a constant level such as pedestal level for an effective period. Thus, the signal levels of video signals for ineffective and effective periods are made equal, and an operation can be provided for visually suppressing the synchronous disturbance on the television monitor caused by the discontinuity of vertical synchronizing signals in the case of switching video signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal switching system capable of displaying a plurality of video signals which are asynchronous with each other and suppressing a disturbance of synchronization on a television monitor at the time of switching the video signal inputs. Related to the device.

[0002]

2. Description of the Related Art Conventionally, a video signal switching device is disclosed in
One described in Japanese Patent No. 155,783 is known.

FIG. 5 shows the structure of a conventional video signal switching device. For example, cameras A, B, and C, which are asynchronous video signals, and a synchronization detecting means 1 for detecting a synchronization signal for each of these video signals. A video signal selecting means 2 for selecting a video signal from an output of the synchronization detecting means 1; a timing control means 3 for controlling switching timing; a digital memory 4; and controlling writing in the digital memory 4. It comprises a write timing control means 5, a read timing control means 6 for controlling reading, and a synchronization signal generating means 7 serving as a reference for reading.

More specifically, the cameras A, B, and C are each input to the synchronization detecting means 1, output the detected synchronization signal to the timing control means 3, and output the selected video signal to the digital memory 4. I do. The timing control unit 3 controls the switching timing of the video signal selection unit 2 based on the output of the synchronization detection unit 1. The video signal switched by the video signal selecting means 2 is written into the digital memory 4 for one field by the write timing control means 5 in accordance with the synchronization state of each camera. The video signal written in the digital memory 4 is read at a timing generated by the read timing control means 6 based on the output of the synchronizing signal generation means 7 at a fixed period independent of the writing side.

[0005]

In this video signal switching apparatus, a digital memory 4 is arranged as means for synchronizing a plurality of video signals that are asynchronous with each other, and the synchronization is performed by reading out the data at a constant period. Has been realized.

However, this configuration has a large circuit scale and is disadvantageous in terms of cost. Therefore, it is required to simplify the configuration. SUMMARY OF THE INVENTION It is an object of the present invention to provide a video signal switching apparatus which can display a plurality of video signals which are asynchronous with each other with a simple configuration while suppressing disturbance of synchronization on a television monitor without using a digital memory. And

[0007]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention does not use a digital memory and outputs a plurality of asynchronous video signals at the time of switching of each connected video signal input. Until the TV monitor pulls in by the synchronization signal and subcarrier of the video signal of
The configuration is such that the effective range according to the broadcast standard RS-170A or the like is masked.

As a result, disturbance of synchronization on the television monitor is suppressed, and high-quality video signal input switching can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a video signal input means connected to a plurality of mutually asynchronous video signals, and a video signal selection means for selecting the video signal input means. Mask means for masking an effective range within a horizontal period of a video signal; video output means for outputting a video signal output from the mask means; and control for controlling switching timing of the video signal selection means and the mask means. The control means switches the video signal from each of the video signal input means by the video signal selection means, and then controls the mask means at a timing when a vertical synchronization signal of the video signal reaches a predetermined number. It is characterized by canceling the synchronization and synchronizing with the video signal after the television monitor is switched during the masking period, and suppressing the synchronization disturbance at the time of switching the video signal. It has the effect of.

The invention according to a second aspect is characterized in that, in the first aspect, the video signal output from the video signal selection means and the mask means is switched to the video output means for output.

According to a third aspect of the present invention, in the first and second aspects, the switching signal is output to the video signal selecting device at the timing of the vertical synchronization signal in the video signal immediately before switching. I do.

According to a fourth aspect of the present invention, in any of the first to third aspects, a configuration is provided in which a control means capable of changing a timing for canceling a mask signal input to the mask means is provided.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. It is to be noted that components having the same functions as those of the conventional example shown in FIG.

(Embodiment 1) FIG. 1 is a block diagram of a video signal switching apparatus according to Embodiment 1 of the present invention, and FIG. 2 is an operation explanatory diagram.

In FIG. 1, cameras A to A which are asynchronous with each other
Video signal input means 8a to 8h to which H video signals are input
Are connected to the video signal selection means 2 prepared for each of the cameras A to H. 9 is a synchronization detecting means for detecting the synchronization from the output of the video signal selecting means 2, 10 is a masking means for making the output video signal of the video signal selecting means 2 a constant signal, and 11 is controlling the video signal selecting means 2 and the masking means 10. The control means 12 performs image output means.

The operation of the video signal switching device thus configured is as follows. 2, (a) is a video signal of camera A, (b) is a video signal of camera B, (c)
Is a video signal of the camera C. For example, when switching from the camera A to the camera B, the output of the video signal selecting means 2 becomes the video signal shown in (e) by the switching signal (d) output from the control means 11 to the video signal selecting means 2, and (d)
The vertical synchronizing signal between camera A and camera B is switched discontinuously at the time of the pulse of. A mask for setting the effective range of the video signal to a constant level such as a pedestal level by the control means 11 for a time period n frames or more until the television monitor pulls in the synchronization signal and the subcarrier of the video signal from the pulse of (d) as a starting point Masking means 1 for signal (f)
Output to 0. Thereafter, in the period (a) of (f), the mask is released and the video signal of the effective range is output.

As described above, at the time of the pulse of the switching signal (d), the television monitor starts pulling in by the synchronization signal of the camera B and the sub-carrier output after the switching, and during this time, the video signal in the effective range Is masked to a certain level such as the pedestal level, so that the signal level of the invalid range of the video signal and the signal range of the effective range become the same, and the effect of visually suppressing the synchronization disturbance of the TV monitor caused by the discontinuity of the vertical synchronization signal. is there.

In the above description, the video signal selecting means 2
Has been described as an example in which the output of the masking means 10 is masked by the output of the control means 11.
A configuration in which the output of 0 and the output of the video signal selection means 2 are switched by the output of the control means 11 and output to the video signal output means 12 can be similarly implemented. Further, the number of cameras may be A to H or more.

(Embodiment 2) FIG. 3 is a block diagram of a video signal switching apparatus according to Embodiment 2 of the present invention, and FIG.

In FIG. 3, the switching of the video signal by the video signal selecting means 2 is performed at a timing based on the video signal immediately before the switching, that is, the timing based on the vertical synchronization signal of the currently selected video signal. Control means 13 for controlling is provided.

The operation of the video signal switching device thus configured is as follows. For example, video signal input means 8a
If 8b is selected next to the currently selected 8a among the outputs 8 to 8h, the output (a ') obtained by synchronously detecting the currently selected video signal by the synchronous detection means 9 is output to the control means 13 And the control means 13 outputs the switching signal of (g) to the video signal selecting means 2. The video signal switched by the video signal selection means 2 is as shown in FIG.
The vertical synchronizing signal between the cameras A and B is switched discontinuously at the time of the pulse of (g). The control unit 13 sets the effective range of the video signal to a constant level such as a pedestal level for at least n frames until the television monitor pulls in the synchronization signal and the subcarrier of the video signal from the pulse of (g) as a starting point. The signal (i) is output to the mask means 10. Thereafter, in the period (b) of (g), the mask is released and the video signal of the effective range is output.

As described above, at the instant of the switching of the pulse of the switching signal (g), the switching instant is switched to the pedestal level not in the middle of the horizontal period of the television monitor but in the vertical synchronization period. On the other hand, pulling in on TV monitor
The process is started by the synchronization signal of the camera B and the sub-carrier output after the switching. The video signal in the effective range is masked to a certain level, such as the pedestal level, until it is pulled in, so that the signal level in the invalid range and the effective range of the video signal becomes the same from the moment of switching, and the vertical sync signal is discontinuous Has the effect of visually suppressing the disturbance of synchronization of the television monitor caused by the above.

In the above description, the output of the video signal selection means 2 is masked by the mask means 10 by the output of the control means 13, but the output of the mask means 10 and the video signal selection Control means 13 controls the output of means 2
A configuration in which the output is switched to the video signal output means 12 and output to the video signal output means 12 can be similarly implemented. Further, the number of cameras may be A to H or more.

(Embodiment 3) Since the pull-in time varies depending on the TV monitor, the timing for canceling the mask can be set arbitrarily, so that the required minimum mask time is required depending on the TV monitor. The effect that the subsequent video signal can be seen as soon as possible can be obtained.

[0025]

As described above, according to the present invention, a plurality of video signals that are asynchronous with each other can be obtained immediately after video signal switching even if a digital memory for phase adjustment is not separately provided. By masking the effective range of the video signal until the television monitor pulls in the synchronization signal and the subcarrier, there is obtained an advantageous effect of visually suppressing television monitor synchronization disturbance caused by discontinuity of the vertical synchronization signal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a video signal switching device according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram showing a video signal switching device according to (first embodiment) of the present invention;

FIG. 3 is a block diagram showing a video signal switching device according to a second embodiment of the present invention.

FIG. 4 is an operation explanatory diagram showing a video signal switching device according to (Embodiment 2) of the present invention;

FIG. 5 is a configuration diagram showing a conventional video signal switching device.

[Explanation of symbols]

 2 video signal selection means 8a to 8h video signal input means 9 synchronization detection means 10 mask means 11 control means in (first embodiment) 12 video signal output means 13 control means in (second embodiment)

Claims (4)

[Claims] 1. A video signal input means connected to a plurality of video signals asynchronous with each other, a video signal selection means for selecting an output from the video signal input means, and a mask for masking an effective range of the video signals. Means, a video output means for outputting a video signal output from the mask means, and a control means for controlling switching timing of the video signal selection means and the mask means, wherein the control means selects the video signal. Means for switching the video signal from each of the video signal input means by means, and then releasing the mask means at a timing when a vertical synchronization signal of the video signal reaches a predetermined number. 2. A video output means for switching and outputting a video signal output from a video signal selection means and a mask means, wherein the switching is performed by the video signal selection means transmitting a video signal from each of the video signal input means. 2. The video signal switching device according to claim 1, further comprising control means for performing the switching at a timing when the number of vertical synchronization signals of the video signal reaches a predetermined number. 3. The control means, when switching the video signal from each of the video signal input means by the video signal selection means,
3. The video signal switching device according to claim 1, wherein a switching signal is output to the video signal selection device at a timing of a vertical synchronization signal in a video signal immediately before switching. 4. A control means for changing a timing for canceling a mask signal input to the mask means.
The video signal switching device according to claim 3.