JPH04142189A - Video signal through path circuit for video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a normal picture even in the case of the video signal including a copy guard signal by outputting the video signal including the copy guard signal to a picture display device without passing an automatic gain adjusting means at the time of connecting two or more video signal recording and reproducing devices and the picture display device in series. CONSTITUTION:A selecting means SW2 is provided which selects one of outputs of a video signal input terminal Vi and an automatic gain control means 2 to output the selected output to a video signal output terminal Vo. If a normal picture cannot be obtained because the copy guard signal is included in the video signal, a select signal to allow the video signal to pass through is given to the selecting means SW2 by a select signal generating means 3. As the result, the selecting means SW2 selects the video signal from the video signal input terminal Vi to output it to the video signal output terminal Vo, and the video signal is given to a picture display means from the video signal output terminal Vo. Thus, the normal picture is projected on a television receiver even in the case of the video signal including the copy guard signal.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a video signal through-pass circuit for a video signal recording/playback device, and in particular to an automatic video signal through-pass circuit for recording video signals from another video signal recording/playback device. The present invention relates to a video signal through-pass circuit for a video signal recording/reproducing device that can output the video signal to an image display device without passing through a gain adjustment circuit.

[Prior art] Video tape recorders are available in beta format,
Various systems are used, including the VH3 system. Therefore, it is not possible to dub a video signal recorded on a video tape unless a video tape compatible with each type of model is used.

However, even if the formats are different, the output signal to the television receiver is the same, so you can connect models with different formats and dub the contents of a videotape of one format onto a videotape of another format. be able to.

FIG. 3 is a diagram in which two video tape recorders of different systems are connected in series and connected to a television receiver. Referring to the figure, the video table recorder 13 has a VH
5 system, and the video tape recorder 14 is of the Beta system. A Beta video tape recorder 14 is connected to a television receiver 15 . The video tape recorder 13 and the television receiver 15 are connected through an AGC circuit within the video tape recorder 14. By making the connections as described above, the video signal output from the VH8 video tape recorder 13 can be dubbed by the Beta video tape recorder 14. Also, while dubbing, the television receiver 1
5 screen images can be displayed. In this case, the gain of the image signal from the video tape recorder 13 is adjusted by an AGC circuit built into the video tape recorder 14, so that it can be dubbed at an appropriate level.

[Problems to be Solved by the Invention] Incidentally, a recorded video tape recorder that is attached to a video tape recorder may include a copy guard signal to prevent dubbing. A video signal containing this copy guard signal is shown in FIG. This copy guard signal includes, for example, a plurality of pulses of 100% white level in the retrace period. The video signal containing the copy guard signal is sent to the AG of the video tape recorder 14.
When the gain is adjusted by the C circuit, the video signal from the video tape recorder 13 is attenuated as shown by the broken line in FIG. The image displayed on the television receiver 15 based on this attenuated image signal may become darker than its original brightness, or its brightness may change periodically. That is, even if the image signal is not intended for dubbing, passing the image signal through the AGC circuit built in the video tape recorder 14 lowers the level of the signal, making it impossible to obtain a normal image.

The present invention has been made in view of the above problems, and is a video signal recording/reproducing device that can display a normal image on the screen of a television receiver even if the video signal includes a copy guard signal. The purpose of the present invention is to provide a video signal through-pass circuit.

[Means for Solving the Problems] To achieve the above object, the present invention provides a video signal input terminal, automatic gain adjustment means for automatically adjusting gain for recording a signal from the video signal input terminal, and automatic gain adjustment means for recording a signal from the video signal input terminal. and a video signal output terminal for outputting the video signal whose gain has been automatically adjusted by the gain adjustment means to the image display device.
The playback device has the following features. That is, selecting means selects either one of the output of the video signal input terminal and the output of the automatic gain control means and outputs the selected one to the video signal output terminal, and generates a signal for causing the selection means to perform a selection operation. and selection signal generating means.

[Function] In the present invention described above, when a normal image cannot be obtained because the video signal input to the video signal input terminal includes a copy guard signal, the selection signal generating means deletes the video signal. A selection signal for passing through is given to the selection means. As a result, the selection means selects the video signal from the video signal input terminal and outputs it to the video signal output terminal. A video signal is given to the image display means from this video signal output terminal.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a video signal through-pass circuit of a video signal recording/reproducing apparatus of the present invention. Referring to the figure, the video signal through-pass circuit includes a video signal output terminal Vi connected to the output of another video tape recorder.
, a video signal output terminal Vo connected to a television receiver, an amplifier 1 and an AGC circuit 2 connected to a video signal input terminal Vi, and a signal whose gain has been automatically adjusted by the AGC circuit 2 is transferred to a video tape (not shown). ), a playback processing circuit 5 for playing back the video signal recorded on the videotape, and an output of the AGC circuit 2 and an output of the playback processing circuit 5. connected, selects the output of AGC circuit 2 during recording,
A recording/playback selection switch SWI that selects the playback signal during playback, and the output of amplifier 1 and the record/playback selection switch S
an output selection switch SW2 that is connected to the output of W1 and selects either the output of the amplifier 1 or the output of the selection switch SWI in response to an output selection signal to be described later;
It includes a selection signal generation circuit 3 that generates a selection signal for controlling selection of the output selection switch SW2.

FIG. 2 is a circuit diagram showing details of the video signal through-pass circuit of the video signal recording and reproducing apparatus shown in FIG. 1. Note that this figure shows a state in which the input video signal is bussed to the output terminal Vo. In the figure, a plug-in type terminal 11 is used as the video signal input terminal Vi. A resistor R is connected to the terminal 11 for matching with subsequent circuits. The AGC circuit 2, the reproduction signal processing circuit 5, and the recording signal processing circuit 4 are incorporated into an integrated circuit 12 for luminance signal processing.

Amplifier 1 is connected to terminal 11 via coupling capacitor C1. This amplifier 1 includes an emitter follower circuit 13, a grounded base circuit 14, and an emitter follower circuit 15, and amplifies the video signal over a wide band at 6 dB. The selection signal generation circuit 3 includes an operation switch 17 connected between the power supply voltage Vcc and ground and operated by an operator. In the case of through-pass, the power supply voltage Vcc (high level) is set to the output selection switch S.
When applying to W2 to select the output of AGC circuit 2,
Earth level (low level) signal selection switch SW
Give to 2. An emitter follower circuit 18 is connected to the output of the selection switch SW2, and the output of this emitter follower circuit 18 is given to the video signal output terminal vO. In addition, 19
is an integrated circuit including an output selection switch SW2.

The operation of the video signal through-pass circuit shown in FIGS. 1 and 2 will be explained.

For the purpose of dubbing, the operation switch 17 is operated to apply a low level signal to the output selection switch SW2, so that the selection switch SW2 selects the output of the AGC circuit 2. In this state, a video signal from another video tape recorder is applied to the amplifier 1 and the AGC circuit 2 after passing through the video signal input terminal Vi. A
The video signal applied to the GC circuit 2 is applied to the recording signal processing circuit 4 after automatic gain adjustment. The signal applied to the recording signal processing circuit 4 is converted into a recording signal, and the converted signal is recorded on a videotape. Also, AGC
The output of the circuit 2 is also applied to a recording/reproduction selection switch SWI, and through this switch SWI to an output selection switch SW2. The output selection switch SW2 selects the output of the AGC circuit 2 because a low level signal is input from the operation switch 17. The selected signal is sent to the video signal output terminal V through the emitter follower circuit 18.
output to o. The television receiver displays an image based on the signal from the output terminal Vo.

Next, if the image displayed on the preview receiver is not normal due to the influence of the copy guard signal, the operation switch 17 is operated to apply a high level signal (Vcc) to the output selection switch SW2. Output selection switch S
W2 enters a state in which the output of amplifier 1 is selected. In this state, a video signal input manually from another video tape recorder is given to the amplifier 1 and the AGC circuit 2.
The output of the amplifier 1 is selected by the output selection switch SW2. The selected signal is current amplified by the emitter follower circuit 18 and then output to the video signal output terminal vO. Since the television receiver receives a signal obtained by amplifying the signal from another video deck by 6 dB by the amplifier 1, a normal image can be obtained. Note that if dubbing is not intended from the beginning, a high level signal may be output from the selection signal generation circuit 3 so as not to be influenced by the copy guard signal i.

In the above embodiment, an amplifier is connected between the video signal input terminal Vi and the video signal output terminal Vo, but if the level of the video signal from another video tape recorder is sufficiently high, this amplifier may be installed. You don't have to.

[Effects of the Invention] According to the present invention, when two or more video signal recording/reproducing devices and an image display device are connected in series, the video signal containing the copy guard signal is processed by the automatic gain adjustment means. Since the video signal can be output to the image display device without passing through the video signal, a unique effect can be obtained in that a normal image can be obtained even if the video signal includes a copy guard signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of FIG. 1, FIG. 3 is a connection diagram showing a state in which dubbing is performed with two video tape recorders, FIG. 4 is a diagram for explaining inconveniences when displaying a video signal containing a copy guard signal. In the figure, 1 is an amplifier, 2 is an AGC circuit, 3 is a selection signal generation circuit, Vl is a video signal input terminal, Vo is a video signal output terminal, and SW2 is an output selection switch.

Claims (1)

[Claims] A video signal input terminal, an automatic gain adjustment means for automatically adjusting the gain for recording a signal from the video signal input terminal, and an image display device for displaying the video signal whose gain has been automatically adjusted by the automatic gain adjustment means. A video signal recording/reproducing device including a video signal output terminal for outputting to the video signal output terminal, wherein either one of the video signal input terminal and the output of the automatic gain control means is selected and output to the video signal output terminal. A video signal through-pass circuit for a video signal recording/reproducing apparatus, comprising: a selection means; and a selection signal generation means for generating a signal for causing the selection means to perform a selection operation.