JPH05219433A - Video signal changeover device - Google Patents

Abstract

PURPOSE:To reduce number of bits of control data latched by each video signal changeover device comprising plural video signal changeover devices and a 2-stage video signal changeover device selecting an output signal of them. CONSTITUTION:Latch control data in a 2-stage video signal changeover device 2 have a shelf address of a video signal changeover device selected at least by itself. Control data for each of video signal changeover devices 3, 4 have its own shelf address and an address of an input video signal selected by itself. The coincidence/anticoincidence between the shelf address from the video signal changeover devices 3, 4 returned in response to a tarry request from a host and a shelf address latched by the 2-stage video signal changeover device 2 is discriminated and its coincidence/anticoincidence information is returned to the host. Thus, since the host discriminates which video signal changeover device is set based on the coincidence/anticoincidence information, it is not required to allow each video signal changeover device to latch on/off data.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a video signal switching device, and more particularly to a control system of a video signal switching device used in a television studio transmission system.

[0002]

2. Description of the Related Art A video signal switching device is specifically constructed as shown in FIG. In this example, two video signal switches 3, 4
Are provided, and each of them is plural (4 in this example).
It has a function of selectively deriving one of the input video signals of 1) by an external command.

An address (generally called a shelf address) for specifying each of the video signal switches 3 and 4 is given in advance. In this example, the former address is (0,0) and the latter address is (0,1).

Each of the video signals (No. 4 and No. 7 in this example) selected by the video signal switching units 3 and 4 is input to the two-stage video signal switching unit 2 and selected again by an external command. It is selected once and becomes the final video output. In this example, the shelf address (0, 1) No. 7 shows a state in which the input video signal of 7 is output, and the control computer 1
One of these input video signals is selected by the control of.

The format of the control data in this case is as shown in FIG. The whole has a 5-bit structure of D0 to D4, and a 2-bit D1 and D2 represents a shelf address (address for specifying each video signal switch),
The two bits D3 and D4 represent the in-shelf address (the number of the input video signal in each video signal switch). In the case of a shelf (video signal switching device) selected by the two-stage video signal switching device 2, the bit D0 is 1 indicating ON, and in the case of an unselected shelf, 0 is indicating OFF.

When it is desired to control the selection state shown in FIG.
The control computer 1 outputs control data for a switching instruction, and switching processing of each unit is performed. Then, the control data shown in FIG. 1C is held in the registers (not shown) of the units 2 to 4. The control data shown in FIG. 1C includes the video signal switch 3, the video signal switches 4 and 2 from the left.
It is assumed that they are respectively held in the stage video signal switching unit 2.

In this state, the operation when the control computer 1 makes an inquiry (tally request) for the held data to each of the video signal switches 2 to 4 will be described with reference to the time chart of FIG. The tally request is made to know which input video signal is currently selected.

In step 1, the control data (× 00 ×) is sent together with the control data inquiry command from the control computer 1.
X) is transmitted (x is indefinite). The video signal switch 3 corresponding to the shelf address (00) sends out its own held data. The two-stage video signal switch 2 sends the control data to the computer 1 as it is because the bit D0 of the sent control data is 0 (OFF). The computer 1 ignores the control data sent by looking at 0 of D0.

The video signal switch 4 does not send its own control data because the shelf addresses do not match.

The control computer 1 proceeds to the next step 2 in order to generate an inquiry to the next video signal switch 4. In this step, together with the control data inquiry command,
Control data (x01xx) is transmitted. The video signal switch 4 corresponding to the shelf address (01) sends out its own held data. The two-stage video signal switch 2 sees the bit D0 of the transmitted control data and is set to 1 (ON). Therefore, the two-stage video signal switch 2 determines that it is holding (× 0100) and the transmitted control data. The data is compared, and if they match, the control data is sent to the control computer 1. The control computer will take in this control data.

In the above-mentioned conventional control method, the video signal switching devices 3 and 4 use 5 bits (D0
~ D4) must be held, and if this control data is lost at the momentary power failure on the video signal switch side, the address data of D1 ~ D4 showing the internal state can be restored by itself, but it is possible to use external information. Certain D0 on / off data cannot be recovered.

Therefore, there is a drawback that a holding circuit at the momentary power failure, a latch circuit and the like for the ON / OFF data of D0 are required.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video signal switcher capable of reducing the circuit scale by eliminating the need for a momentary power failure holding circuit and a latch circuit for ON / OFF data.

[0014]

According to the present invention, a plurality of video signal switching devices, each of which selectively derives one of a plurality of input video signals in accordance with an external command, and one of the selected outputs of these video signal switching devices. And a two-stage video switching device for selectively deriving one of the plurality of video signal switching devices according to an external command, wherein each of the plurality of video signal switching devices outputs an address of the selected input video signal in addition to its own address. The two-stage video switch has means for holding the video signal switch, and the two-stage video switch has a means for holding at least the address of the video signal switch being selected, and the video signal switch in response to an inquiry of the held data from the host device. Switching the video signal, each of the address data sent from each of the above and the address data held by itself is determined, and means for returning the match / mismatch information to the host device. The device is It is.

[0015]

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

FIG. 1A is a block diagram of a video signal switch applied to the present invention, which is the same as the conventional one, but the structure of the control data held in each video signal switch is the same as that of the conventional example. Different from the above, the format is as shown in FIG.

In the switching state shown in FIG. 1 (A), the respective control data held in the video signal switching units 3 and 4 and the two-stage video signal switching unit 2 are shown in order from the left in FIG. 1 (B). The ON / OFF data of bit D0 is not held and is unnecessary.

A case where the control computer 1 makes a tally request for the held data in this state will be described with reference to the time chart of FIG.

In step 1, the control computer 1
Control data (× 00
XX) is sent. In the two-stage video signal switch 2,
The shelf address portions of the control data (0110) held by itself and the control data from the computer are compared. In this case, since they do not match, the control data (0011) sent from the video signal switch 3 is added with 0 indicating that it is off at the bit D0 portion (00011).
It is returned to the control computer 1.

When the control computer recognizes that the ON / OFF data is 0, it does not take in the sent control data and proceeds to the next step 2.

In step 2, the control data (× 01xx) is sent from the control computer 1 together with the control data inquiry command.
Will be sent. The two-stage video signal switch 2 compares the shelf address portion between the control data (0110) held by itself and the control data from the computer. In this case, since they coincide with each other, the control data (0110) sent from the video signal switching unit 4 is added to the bit D0 portion by 1 indicating that it is turned on (10110) and returned to the control computer 1. ..

The control computer 1 recognizes that the on / off data indicates 1 (on), reads the transmitted control data, and ends the process.

[0023]

As described above, according to the present invention, since it is not necessary to add the ON / OFF data to the holding control data, the latch circuit for the latch is not required in each video signal switching device, and This has the effect of eliminating the need for a protection circuit for data instantaneous interruption.

[Brief description of drawings]

FIG. 1A is a system configuration diagram to which an embodiment of the present invention is applied, FIG. 1B is a diagram showing an example of held data according to an embodiment of the present invention, and FIG. 1C is an example of conventional held data. It is a figure.

FIG. 2 is a diagram showing a format of control data.

FIG. 3 is a sequence diagram showing an operation of the exemplary embodiment of the present invention.

FIG. 4 is a sequence diagram showing a conventional operation.

[Explanation of symbols]

 1 control computer 2 2 stage video signal switch 3, 4 video signal switch

Claims (1)

[Claims] 1. A plurality of video signal switches each of which selectively derives one of a plurality of input video signals by an external command,
A video signal switching device including a two-stage video switching device for selectively deriving one of the selected outputs of these video signal switching devices according to an external command, wherein each of the plurality of video signal switching devices has its own address. In addition to the above, there is provided means for holding the address of the input video signal being selected, and the two-stage video switching device holds at least the address of the video signal switching device being selected; In response to a data inquiry, it is determined whether or not the address data sent from each of the video signal switching devices and the address data held by the video signal switching device are matched, and the match / mismatch information is returned to the host device. And a video signal switching device.