JPH11103440A - Circuit for preventing vtr recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a VTR recording preventing circuit which is easily and inexpensively incorporated into a TV receiver or a TV monitor, etc. SOLUTION: A synchronization separating circuit 1 separates a composite synchronizing signal S2 (vertical and horizontal synchronizing signal after removing a video part) from a TV video signal S1. A delay circuit 2 outputs a pulse S3 which is given prescribed delay within the range of the pulse width of a horizontal synchronizing signal. A pulse generating circuit 3 generates the pulse S4 for preventing video recording, which can be inserted to the inside of the horizontal synchronizing pulse by receiving the pulse S3. A synthesizing circuit 4 inserts the pulse S4 into the whole horizontal synchronizing pulses including the vertical feedback erasion time of the TV video signal S1 and transmits it to VTR as a video recording prevention-processed output TV video signal S5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VTR recording prevention circuit, and more particularly to a VTR recording prevention circuit for processing a television video signal so that recording cannot be performed by a VTR (video tape recorder).

[0002]

2. Description of the Related Art Conventionally, recording prevention processing is performed on a video signal recorded on a video tape. When a videotape that has been subjected to recording prevention processing is played back on a general VTR,
Disturbances occur in the synchronous scanning servo system of the TR so that recording and reproduction become impossible. For example, JP-A-1-238
No. 287 discloses a VTR for preventing unauthorized duplication of a product video tape. According to this, during a plurality of horizontal scanning periods near the vertical synchronizing signal of the input television video signal, a similar horizontal synchronizing signal similar to the horizontal synchronizing signal whose amplitude changes is inserted, and the breathway of almost all the horizontal synchronizing signals is inserted. A pulse of almost 100% IRE level is inserted in a section (a section from a horizontal synchronization rising portion to before a color burst signal) and recorded on a video tape.

[0003]

In the above-mentioned conventional example,
In order to generate a disturbance in the synchronous scanning servo system of the VTR during video tape reproduction, a similar horizontal synchronizing signal whose amplitude changes near the vertical synchronizing signal is inserted. A television picture signal with a pulse inserted is generated and recorded on a video tape. For this reason, there is a problem that the circuit configuration is complicated and expensive.

[0004] It is an object of the present invention to provide a TV video signal input to a VTR by performing a video recording prevention process.
A VT that can be easily and inexpensively incorporated into a broadcast receiver, a TV receiver, or the like, and can easily perform a recording prevention process on a television video signal of a broadcast program that the user does not want to record.
An R recording prevention circuit is provided.

[0005]

SUMMARY OF THE INVENTION A VTR recording prevention circuit of the present invention has a width smaller than the width of a horizontal synchronization pulse and reaches a video level in all horizontal synchronization pulses including a vertical blanking period of a television video signal. Insert a recording prevention pulse.
More specifically, a sync separation circuit for separating a composite sync signal composed of a vertical and horizontal sync signal from an input television video signal, and a delay circuit for providing a predetermined delay within a horizontal sync pulse width based on an output signal of the sync separation circuit A pulse generation circuit for generating a recording prevention pulse narrower than a horizontal synchronization pulse width based on an output signal of the delay circuit; and a method for generating the recording prevention pulse including a vertical blanking period of the input television video signal. And a synthesizing circuit to be inserted into the horizontal synchronizing pulse.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. A sync separation circuit 1 for separating a composite sync signal S2 composed of a vertical and horizontal sync signal from the television video signal S1, a delay circuit 2 for providing a predetermined delay within the horizontal sync pulse width, and recording prevention narrower than the horizontal sync pulse width And a synthesizing circuit 4 for inserting the recording prevention pulse S4 into all the horizontal synchronization pulses including the vertical blanking period of the television video signal S1.

The VTR separates a synchronization signal from an input television video signal, detects synchronization, and controls a servo system to perform recording and reproduction. However, since the VTR synchronization detection is extremely sensitive, if a different type of pulse is mixed in the composite synchronization signal, even a general TV receiver or TV monitor will not affect the screen display. , A synchronization detection error occurs and disturbance occurs in the servo system,
Recording and playback become impossible.

According to the present invention, a general TV receiver or a TV monitor does not hinder the screen display at all, but inserts an extraordinary pulse into the synchronizing signal to the extent that recording cannot be performed on a VTR. The circuit configuration is simplified.

The sync separation circuit 1 includes a composite sync signal S2 (a vertical sync signal excluding a video portion) as shown in FIG.
Horizontal sync signal). The delay circuit 2 is shown in FIG.
As shown in (1), a pulse S3 having a predetermined delay width within the pulse width of the horizontal synchronization signal is output. Pulse generation circuit 3
Receives the pulse S3 from the delay circuit 2 and generates a recording prevention pulse S4 that can be inserted into the horizontal synchronization pulse as shown in FIG. 2C. As shown in FIG. 2D, the synthesizing circuit 4 inserts the pulse S4 into all the horizontal synchronizing pulses including the vertical blanking period of the television video signal S1, and outputs the recording-prevented output television video signal S5. As VTR
Send to

By inserting a pulse in all the horizontal synchronizing pulses including the vertical blanking period, the synchronous position of the vertical synchronizing signal is disturbed in a pseudo manner. When the television image signal S5 is supplied to a TV receiver or a TV monitor, the TV receiver or the TV monitor performs a soft synchronization detection using a blocking oscillation circuit, so that there is no problem and a normal display screen can be obtained. However, when the television video signal S5 is supplied to the VTR, in the synchronization separation and the phase difference comparison, the insertion pulse of the vertical synchronization part disturbs the servo synchronization system, and the pulse inserted in the horizontal synchronization pulse part causes the half pulse H killer. And the drum rotation control system is disturbed, so that normal operation cannot be maintained.

FIG. 3 is a circuit diagram showing an embodiment of the present invention.

The input television video signal S1 branches into two circuit systems, one of which is supplied to a synthesizing circuit 4 via an input buffer amplifier 5 and a clamp circuit 7, and the other is supplied to an input buffer amplifier 6 and a clamp circuit 8. The signal is supplied to the synchronization separation circuit 1 via the synchronization separation circuit 1. The composite synchronization signal S2 output from the synchronization separation circuit 1 is supplied to the delay circuit 2.

The delay circuit 2 is a monostable multivibrator 2
A trigger is applied at the falling edge of the composite synchronization signal (start point of the horizontal synchronization pulse), and a pulse S3 having a fixed time width determined by the resistor 22 and the capacitor 23 is output. The pulse generation circuit 3 is also a monostable multivibrator 31
A trigger is generated at the falling edge of the pulse S3, and a pulse S4 having a fixed time width determined by the resistor 32 and the capacitor 33 is output.

This pulse S4 is supplied to a synthesizing circuit 4.
It is combined with the input television video signal S1 that has passed through the input buffer amplifier 5 and the clamp circuit 7. Here, the synthesizing circuit 4 includes a switch 41 that operates according to the pulse S4.
And a variable voltage source 42 for setting a predetermined voltage, and an output buffer amplifier 43. Switch 41 is pulse S
By switching to the input television video signal S1 and the variable voltage source 42 in response to No. 4, a pulse of a predetermined level is inserted into the input television video signal S1. This makes it possible to perform the same processing as directly combining the pulse S4 with the input television video signal S1.

FIG. 4 is a device connection diagram configured to evaluate the VTR recording prevention circuit of the present invention.

The signal source 11 uses the video output signals of the BS tuner and the CS tuner, and a comparison is made between a case where the video output signal of the signal source 11 is supplied to the VTR 15 as it is and a case where the video output signal is supplied through the VTR recording prevention circuit 13. Also, V
The display screen was checked by connecting the TV monitor 14 to the output side of the TR recording prevention circuit 13.

The position of the insertion pulse, the width of the insertion pulse, and the level of the insertion pulse are changed by adjusting the set values of the resistor 22 of the delay circuit 2, the resistor 32 of the pulse generation circuit 3, and the variable voltage source 42. As a result, the recording prevention effect was maximized when the position of the insertion pulse was about 1.3 μs from the falling edge of the synchronization signal, and the insertion pulse width was 0.3 μs.
5 μs, the insertion pulse level was 100% IRE.
At this time, recording was not possible at all in the VTR 15, and the reproduced image was a black screen. However, the TV monitor 14 was not affected at all.

The position of the insertion pulse is 0.2 μs or more from the falling edge of the synchronization signal, and the insertion pulse width is 0.5 μs.
It is effective if s to 1 μs. In addition, when a pulse of 100% IRE is added to the conventional breatheway section, noise may be generated on the TV monitor screen. Also, 100 only in the horizontal synchronization Breezeway section
Even if a pulse for% IRE was applied, recording could not be completely disabled.

[0020]

As described above, according to the present invention, V
By inserting a pulse narrower than the width of the horizontal synchronizing pulse into all the horizontal synchronizing pulses including the vertical blanking period of the television video signal supplied to the TR,
The recording by the VTR can be disabled without any trouble to the monitor, and a simple and inexpensive VTR recording prevention circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an output signal waveform of each circuit shown in FIG.

FIG. 3 is a circuit diagram showing one embodiment of the present invention.

FIG. 4 is a device connection diagram configured to evaluate the VTR recording prevention circuit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Synchronization separation circuit 2 Delay circuit 3 Pulse generation circuit 4 Synthesis circuit 21, 31 Monostable multivibrator 41 Switch 42 Variable voltage source S1 TV picture signal S4 Recording prevention pulse

Claims (5)

[Claims] 1. A VTR for processing a television video signal so that it cannot be recorded by a VTR (video tape recorder).
A recording prevention circuit, comprising: a means for inserting a recording prevention pulse narrower than the width of the horizontal synchronization pulse and reaching a video level in all horizontal synchronization pulses including a vertical blanking period of the television video signal. V characterized by having
TR recording prevention circuit. 2. The recording prevention pulse insertion means according to claim 1, wherein said recording separation pulse insertion means separates a composite synchronization signal composed of a vertical and horizontal synchronization signal from an input television video signal, and a horizontal synchronization pulse width based on an output signal of said synchronization separation circuit. A delay circuit for providing a predetermined delay within, a pulse generation circuit for generating a recording prevention pulse narrower than a horizontal synchronization pulse width based on an output signal of the delay circuit, and the input television video signal 2. The VTR recording prevention circuit according to claim 1, further comprising a synthesizing circuit that inserts into all the horizontal synchronization pulses including the vertical blanking period. 3. The synthesizing circuit includes a switch that operates in response to the recording prevention pulse, and a variable voltage source that outputs a predetermined voltage, wherein the switch controls the input in response to the recording prevention pulse. 3. The VTR recording prevention circuit according to claim 2, wherein the circuit is switched to one of a television image signal and the predetermined voltage. 4. The delay circuit has a monostable multivibrator that triggers on a falling edge of the composite synchronization signal (a start point of a horizontal synchronization pulse) and outputs a pulse having a fixed time width determined by a resistor and a capacitor. 3. The VTR recording prevention circuit according to claim 2, wherein , 5. The pulse generation circuit triggers on the falling edge (start point) of the pulse output from the delay circuit, and outputs the recording prevention pulse having a fixed time width determined by a resistor and a capacitor 33. 3. The VTR recording prevention circuit according to claim 2, further comprising a monostable multivibrator that performs the recording.