JPH04335779A - Input video signal changeover device - Google Patents

Abstract

PURPOSE:To select a video signal input terminal while a video signal input terminal receiving no video signal is skipped when the video signal input terminal is selected in the video equipment having at least three video signal input terminals or over. CONSTITUTION:The changeover device is provided with a synchronizing signal detection circuit 7, a color signal detection circuit 8 and a chageover switch circuit 2 selecting video signal input terminals. When a selection command signal is received, the switch circuit is sequentially switched and the synchronizing signal detection circuit 7 or the color signal detection circuit 8 discriminates whether or not a synchronizing signal or a color signal is detected from the selected video signal input. When the signal is detected, the selection is stopped for the video signal input terminal and when not detected, a succeeding video signal input terminal is selected. The switch circuit 2 is controlled by a control circuit 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input video signal switching device for selecting one signal from among a plurality of video signals input to a VTR.

0002

2. Description of the Related Art FIG. 11 is a block circuit diagram of a conventional input video signal switching device. In the figure, 1 is a group of input terminals, 1-1 to 1-n are video signal input terminals, 2 is a switch composed of electronic switches, 2-1 to 2-n are contacts of the switch circuit 2, and 3 is a group of input terminals. A video signal output terminal; 4 is a control circuit that sends out a switching signal 6 for the switch circuit 2; 5 is a control circuit 4 that switches the switch circuit 2;
This is a switch that commands the

Next, the operation will be explained. When the user closes the switch 5, a switching signal 6 is sent from the control circuit 4 to the switch circuit 2. The switch circuit 2 is initially connected to the contact 2-1, and each time the switching signal 6 is input, the switch circuit 2 is sequentially switched to the contacts 2-2, 2-3, . . . 2-n. The user listens to the video signal output from the output terminal 3 on a monitor (not shown) and repeats the selection operation until a desired program is selected. Although only the video signal switching circuit is shown in FIG. 11, the audio signal switching circuit is similarly configured, and the audio signal can be switched along with the video signal.

0004

[Problems to be Solved by the Invention] In recent years, the number of input terminals for video signals in VTRs has been increasing. For this reason, when the user selects a video input signal, the user also sequentially selects connection terminals to which no video signal is input, so there is a problem in that the input video signal selection operation is complicated.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a video signal switching device that selects only the video input terminal to which a video signal is input. .

[0006]

[Means for Solving the Problem] The device has a sync signal detection circuit and a chrominance signal detection circuit, and when a sync signal or chrominance signal is not detected from the video signal input terminal selected by the switch circuit, The present invention is characterized by comprising means for controlling the switch circuit to select the next video signal input terminal.

[0007]

[Operation] The means for controlling the selection operation of the switch circuit automatically selects the next video signal input terminal when no synchronization signal or color signal is detected from the selected video signal input terminal. Therefore, each time the user performs a switching command operation, the input video signal is always displayed on the monitor. Therefore, the user does not have to perform unnecessary switching command operations, and the complexity of the selection operation is reduced.

[0008]

【Example】

Example 1. FIG. 1 is a block circuit diagram of an embodiment of claim 1, in which 7 is a synchronizing signal detection circuit, 8 is a color signal detection circuit, and 9 is a control circuit.

The synchronization signal detection circuit 7 is a well-known circuit that separates the synchronization signal of the video signal and applies AFC to determine whether or not there is a synchronization signal in the video signal, although a detailed explanation of its configuration will be omitted. This is the circuit.

FIG. 2 is a block circuit diagram of the color signal detection circuit 8. The video signal is 3.58 in the case of NTSC system.
Since there is a color signal in MHZ, the color signal detection circuit 8 is amplified by an amplifier having characteristics as shown in FIG. That is, the transistor 100 has a capacitor 1 at its collector.
02 and a coil 101 as a load, the gain of the transistor 100 becomes maximum at the resonance point of the capacitor 102 and the coil 101, the color signal in the video signal is amplified to the maximum, and the impedance of the transistor 102 increases. It is converted into a direct current by a resistor 103 and a capacitor 104. Therefore, when the input of the comparator 106 becomes higher than the set voltage V105, that is, when there is a chroma signal, the output of the comparator 106 becomes "H".
level, and it is detected that there is a color signal, that is, a video signal.

In addition, based on the same principle, by selectively amplifying only the burst signal (same frequency as the chrominance signal) in the video signal as described above and performing sample hold, the chrominance signal can be similarly amplified. The presence or absence can be detected.

When the selection command signal is input from the switch 5, the control circuit 9 discriminates whether or not a detection signal is input from the synchronization signal detection circuit 7 or the color signal detection circuit 8, and determines whether the detection signal is input. When the input signal is not input, the switch circuit 2 is switched to the next contact, and when the input is input, the switch circuit 2 is controlled so as to stop with that contact selected. Therefore, each time the user turns on the switch 5, the switch circuit 2 operates to sequentially select only the input terminals to which a video signal is input, and to skip over contacts to which no video signal is input.

FIGS. 4 and 5 are flowcharts when the control circuit 9 is composed of a microcomputer.
is a flowchart of an operation for detecting the presence or absence of an input video signal from input terminals 1-1 to 1-n.

First, when the switch 5 is turned on, S1
Clear registers A(1) to A(N) in S2, set M to O in S3, set M to 1 in S3, select input terminal M in S4, and check whether the detection signal is input in S5. If the detection signal is input, register A is input in S6.
If (M) is set to 1 and there is no input, set M to O in S7 and proceed to S8. In S8, it is determined whether M=N or not, and M=N.
If not, the loop returns to S3, and all input terminals 1
-1 to 1-N to detect input terminals to which a video signal is input and input terminals to which a video signal is not input.

The flowchart of FIG. 5 is a flowchart of the second and subsequent selection operations, in which the input terminal to which the video signal is input is selected in S9 to S12, and then the video selection command switch 5 is turned on in S13. And M in S14
=N is discriminated, and if M≠N, return to S10,
Repeat the operation of selecting the input terminal to which the next video signal is input.

In the above embodiment, the synchronizing signal detection circuit 7 and the control circuit 8 are provided on the output side of the switch circuit 2, but they may be provided for each input circuit before the changeover switch circuit 2.

Example 2. FIG. 6 is a block circuit diagram of an embodiment of the invention according to claim 2, and 2a to 2c are switch circuits,
Detection switches 31 to 34 constitute video signal cable connection detection means, and are connected to video signal input terminals 1-1 to 1-34.
When a video signal cable is connected to terminals 1-n, it turns ON and sends out an "L" level signal. Numerals 35 to 37 are logic circuit blocks that respond to the detection signals inputted from each of the detection switches 31 to 34 and the switching signals outputted from the output terminals A and B of the control circuit 9 based on the combinations shown in Table 1 shown in FIG. Basically, a switching signal is generated to control opening and closing of the switch circuits 2a to 2c.

Next, the operation will be explained. First, consider a case where video signal input cables are connected to all video signal input terminals 1-1 to 1-4. Now switch 5
When turned on, first, a switching signal (see Table 1 in FIG. 7) A=H, B=H signals for selecting the video signal input terminal 1-1 is output from the control circuit 9. The signal H output from the output terminal A switches the switch circuit 2c to the H side, and the signal H output from the output terminal B switches the switch circuit 2c to the H side.
5, an H level signal is input to the switch circuit 2a, and at the same time, an L level signal is output from the detection switch 31, but it is inverted to H level by the inverter and the H level signal is input. , the switch circuit 2a is H
It can be switched to the terminal side. As a result, the video signal input from the video signal input terminal 1-1 is selected and output from the output terminal 3.

Next, when the switch 5 is turned on, the switching signal A=H, which selects the video signal input terminal 1-2 in Table 1, is turned on.
B=L is output from the control circuit, and the switch circuit 2a is set to L.
The video signal input from the video signal input terminal 1-2 is selected and output from the output terminal 3. Thereafter, in the same manner, each time the switch 5 is turned on, the video signals input from the video signal input terminals 1-3 and 1-4 are sequentially selected.

Next, video signal input terminals 1-1, 1-2
This section explains the operation when the video signal cable is not connected. When switch 5 is turned on, A=H, B=
An H switching signal is output from the control circuit 9, but an H level signal is output from the detection switch 31, which is inverted by the inverter and an L level signal is input, so the switch circuit 2a is switched to the L side. .

At this time, the detection switch 32 is sending out an H level signal, and this signal becomes an L level signal via the logic block 37, causing the switch circuit 2c to go to the L level.
Switch to the side. On the other hand, the L level signal outputted from the detection switch 33 is input to the switch circuit 2b as an H level signal which is inverted by the inverter, so the switch circuit 2b is switched to the H side. As a result, video signal input terminals 1-1 and 1-2 are not selected, but video signal input terminal 1-3 is selected.

Next, when the switch 5 is turned on, signals A=L and B=L are sent out from the control circuit 9, and the switch circuits 2b and 2c are both switched to the L side, and the video signal input terminal 1 -4 is selected.

Example 3. FIG. 8 is a block circuit diagram of another embodiment of the invention according to claim 2, and FIG. 9 shows the output terminals A,
This is a diagram showing combinations of switching signals output from B and C, and the X mark in the diagram indicates that either 1 or 0 may be used. In addition, if the video signal cable is not connected from the detection switches 31 to 34, terminals D, E, F
, G are configured such that H level signals are input to each of them. Further, FIG. 10 is a flowchart of this embodiment.

Next, the operation will be explained. At S1, the microcomputer 9 takes in the detection signals from the detection switches 31 to 34 to P(1) to P(4) as "0" when they are not connected, and as "1" when they are connected. .

Next, in S2, registers A, B, and C are initialized, and then, in S3, settings for each register A, B, and C are performed based on Table 2 of FIG.

Next, in S4, N=0 and switch 5
Wait for the input of a selection command signal from , and each time the selection command signal is input, the settings of registers A, B, and C are switched based on Table 2 until N=4 in S6 to S8.
When a video signal input terminal to which no video signal cable is connected is selected, a logical AND operation is performed in S7, so that information A(N) to C(N) is not sent out. Therefore, unconnected video signal input terminals are skipped.

[0027]

As described above, according to the present invention, it is possible to perform a selection operation by skipping video signal input terminals to which no video signal is input or to which no video signal cable is connected. Therefore, even in video equipment equipped with a large number of video signal input terminals, as in recent years,
This provides the effect of reducing the complexity of input video signal selection operations.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the invention according to claim 1.

FIG. 2 is a diagram showing a color signal detection circuit of this embodiment.

FIG. 3 is an amplification characteristic diagram of the amplifier of this color signal detection circuit.

FIG. 4 is a flowchart of this embodiment.

FIG. 5 is a flowchart of this embodiment.

FIG. 6 is a block circuit diagram of an embodiment of the invention according to claim 2.

FIG. 7 is a chart showing combinations of output signals of the control circuit of this embodiment.

FIG. 8 is a block circuit diagram of another embodiment of the invention according to claim 2.

FIG. 9 is a chart showing combinations of output signals of the microcomputer of this embodiment.

FIG. 10 is a flowchart of this embodiment.

FIG. 11 is a block circuit diagram of a conventional video signal switching circuit.

[Explanation of symbols]

1-1, 1-2,...1-n Video signal input terminals 2, 2a, 2b, 2c Switch circuit 5 Switch 7 Synchronization signal detection circuit 8 Color signal detection circuit 9 Control circuits 31-34 Detection switches 35-37 logic circuit block

Claims (2)

[Claims] 1. A video signal switching device comprising at least three video signal input terminals and a switch circuit that sequentially selects the video signal input terminals each time an input video signal selection command signal is input. , a sync signal detection circuit and a chrominance signal detection circuit, and a sync signal or chrominance signal is included in the signal being input from the video signal input terminal selected by the switch circuit by the sync signal detection circuit and chrominance signal detection circuit. If the sync signal or chrominance signal is not detected, the switch circuit selects the next video signal input terminal, and if the sync signal or chrominance signal is detected, the above switch circuit selects the next video signal input terminal at that position. 1. An input video signal switching device comprising: means for controlling the switching operation of a switching circuit to be stopped. 2. A video signal switching device comprising at least three video signal input terminals and a switch circuit that sequentially selects the video signal input terminals each time an input video signal selection command signal is input. , means for detecting that a video signal input cable provided at each of the video signal input terminals is connected; and when receiving an input video signal selection command signal, the video signal input cable is connected by the detection means. An input video signal switching device comprising means for controlling the selection operation of the switch circuit so as to sequentially select only video signal input terminals.