JPS6113666B2 - - Google Patents

Description

[Detailed Description of the Invention] With the spread of VTRs (recording and reproducing machines), recorded video tapes containing movies and the like are being sold.

However, if you use two VTRs, you can easily dub a copy from a recorded tape.

Although this kind of dubbing of recorded tapes is prohibited by law, if it is done on a small scale in ordinary homes, it cannot be regulated and it is inconvenient for tape manufacturers and copyright holders. It is.

In view of these points, the present invention aims to provide a recorded tape that cannot be dubbed.

First, if we consider a general VTR, it is configured as shown in Figure 1.

That is, in the figure, 10 indicates a recording system, in which a video signal is transmitted from an input terminal 11 through a recording circuit 12 to, for example, 2.
are supplied to two rotating magnetic heads 1 and 2. Heads 1 and 2 have an angular spacing of 180° and motor 3
The magnetic tape 4 is rotated at a frame frequency, that is, at a rate of 30 times per second, and the magnetic tape 4 is wound obliquely over an angular range of approximately 180 degrees with respect to the rotating circumferential surface, and is transported at a constant speed.

20 is a servo circuit, in which the video signal from terminal 11 is supplied to a vertical synchronization signal separation circuit 21 to extract a vertical synchronization signal P _V (A in FIG. 2), which is supplied to a frequency dividing circuit 22 to reduce the frequency to 30Hz. signal P _C
(Fig. 2B) is formed, and this is the phase comparator circuit 2.
3. On the other hand, a pulse generating means 24 is provided on, for example, the rotating shaft 5 of the heads 1 and 2, from which a pulse indicating the rotational phase of each rotation of the heads 1 and 2 is obtained.
supplied to Then, in the phase comparison circuit 23, the phase of the signal P _C from the frequency dividing circuit 22 and the pulse from the pulse generation means 24 is compared, and the comparison output is supplied to the motor 3 through the amplifier 25.
As a result, the rotational phases of the heads 1 and 2 are controlled, and the video signal from the recording circuit 12 becomes one field of one oblique magnetic track _TV , as shown in FIG. Recording is performed on the tape 4 so that the vertical blanking period is at the end of _the track TV, and so that the recording position _R of the vertical synchronizing pulse is at the same position in the extending direction of each track _TV . be done.

In addition, a signal P _C having a frequency of 30 Hz from the frequency dividing circuit 22 is supplied to the magnetic head 26, and as shown in _FIG . A signal trail T _C is formed.

On the other hand, numeral 30 indicates a reproduction system, in which a control signal is reproduced from the tape 4 by the head 26, and is supplied to the phase comparison circuit 23, and the pulse generation means 2
The pulse from 4 is supplied to the phase comparator circuit 23,
In the circuit 23, the phases of these are compared, and the comparison output is supplied to the motor 3 through the amplifier 25, thereby controlling the rotational phase of the heads 1 and 2, so that the heads 1 and 2 are connected to the magnetic track TV of the video signal _. will be scanned correctly.

In this state, a video signal is reproduced from the tape 4 by heads 1 and 2, and this reproduced signal is taken out through a reproduction circuit 31, a switching circuit 32 for muting, an output terminal 33, and further supplied to a monitor receiver 40. be done.

In this case, the playback control signal from the head 26 is supplied to the detection circuit 34 to detect its presence or absence, and the detection signal is supplied to the switch circuit 32. When the playback control signal is not obtained, that is, when the tape 4 When no video signal is recorded on the recording medium, the switch circuit 32 is turned off and muting is performed.

In this way, in a general VTR, when recording,
A vertical synchronizing signal of a constant frequency, that is, 60 Hz, is extracted from the input video signal, and the rotational phase of the rotating magnetic head is controlled based on this vertical synchronizing signal of constant frequency, and this is locked to the frame of the input video signal.
The video signal is recorded on the magnetic tape so that one field constitutes one magnetic track.

Therefore, if the frequency of the vertical synchronizing signal of the input video signal is not constant and its interval changes, the servo of the rotational phase of the rotating magnetic head will be disturbed during recording, and the video signal will no longer be recorded with the correct track pattern. Put it away.

The present invention focuses on this point and makes it impossible to dub a recorded tape.An example of this will be explained below.

FIG. 4 shows an example of an apparatus for producing a recorded tape according to the present invention, in which 50 is a television camera and 60 is a recording VTR.

70 is a crystal oscillator and is the color subcarrier frequency
A 3.58MHz signal _SC is obtained. This 3.58MHz signal S _C is supplied to the first frequency divider circuit 71 and is 2/455
A pulse of 15.734kHz, which is the horizontal frequency divided by
pH is obtained, and this 15.734kHz pulsed pH
is supplied to the second frequency dividing circuit 72 and frequency-divided by 2/525 to obtain a 60 Hz pulse P _V . and this
The 60 Hz pulse P _V is supplied to a phase modulation circuit 73, from which pulses P _VV with varying intervals are taken out.

That is, in this phase modulation circuit 73, the sixth
As shown in the figure, while the input pulse P _V has a constant interval of 1/60 seconds, the output pulse P _VV has a period of 9 times 1/60 second, and the pulse is pulsed during this period. The modulation is performed such that the interval between the two points gradually decreases and gradually increases from the middle.

And 15.734KHz from the first frequency divider circuit 71
The pulse pH from the phase modulation circuit 73 is supplied to the television camera 50 as a horizontal synchronizing pulse, and the pulse P _VV whose interval varies as described above from the phase modulation circuit 73 is supplied to the television camera 50 as a vertical synchronizing pulse.
A 3.58 MHz signal S _C is supplied to the camera 50 .

In the camera 50, horizontal deflection is performed in synchronization with the horizontal synchronization pulse pH, and therefore the period of horizontal deflection is constant, but the vertical deflection signal S _VD
has a constant slope between the pulses P _VV , as shown in FIG. Thus, the center position in the vertical direction of the beam scanning area of the image pickup tube is scanned at this center. Therefore, the vertical deflection signal S
Corresponding to the change in the amplitude of _VD , the scanning range of the beam changes between the range shown by a solid line 82 and the range shown by a solid line 83, with its vertical center not moving. Of course, in this case, the interval between horizontal scanning lines is always constant.

Thus, from the perspective of the television camera 50, the interval of the horizontal synchronization pulses pH is constant, ie, the horizontal frequency is 15.734 kHz, and the interval of the vertical synchronization pulses P _VV varies. That is, the vertical frequency varies within a certain range. Therefore, a video signal in which the number of horizontal sections within one field is not constant but varies is extracted.

This video signal is then supplied to the VTR 60 for recording. As shown in FIG. 5, this recording VTR 60 has a recording system similar to the recording system 10 described in FIG. An input terminal 27 for an external synchronization signal is connected to. The video signal obtained from the camera 50 is supplied to the input terminal 11 of this recording VTR 60, and then sent to the second frequency dividing circuit 72.
A 60Hz pulse P _V from the input terminal 27 is supplied to the input terminal 27 .

Therefore, in the recording VTR 60, a 30 Hz signal P _C is obtained from the frequency dividing circuit 22 by the 60 Hz pulse P _V as shown in FIG. 6, and the rotational phase of heads 1 and 2 is controlled using this as a reference signal. Being done,
Heads 1 and 2 rotate at a rate of 30 times per second in synchronization with a constant frequency pulse P _V which is an external synchronization signal. In this state, the above-mentioned video signal is supplied to the heads 1 and 2, and as shown in _FIGS . One diagonal magnetic track _TV is formed every second, and an equal number of horizontal sections of video signals are recorded on each track _TV .
However, as mentioned above, the interval of the vertical synchronizing pulse P _VV in the video signal to be recorded is not constant and varies, so as shown in FIG _. Truck T
The recording position R _V in the extending direction of _V becomes different.

Further, a 30Hz signal P _C obtained from the frequency dividing circuit 22 is supplied to the head 26 as a control signal.
As shown in FIG. 7, control signal traces T _C are formed on the side edges of the tape 104 for every two video signal tracks T _V .

Recorded tape 10 produced in this way
4 is played back by the general VTR and monitor receiver shown in FIG. Since the tracking servo of the heads 1 and 2 during reproduction is performed by the reproduced signal, the video signal is reproduced from the recorded tape 104 in a predetermined time relationship and is supplied to the monitor receiver 40. In the receiver 40, the vertical synchronizing signal P _VV is extracted from the reproduced video signal and drives the vertical deflection circuit, but since the interval of the vertical synchronizing signal P _VV changes as described above, the vertical deflection The signal S _VD shown in FIG. 6, which is similar to that in the television camera 50, is obtained. Therefore, the receiver 40
In this screen, the scanning range of the beam changes between the range shown by solid line 32 and the range shown by solid line 83, with its vertical center not moving and the interval between horizontal scanning lines being constant. Yotsute 1
If the field is made up of the minimum number of horizontal sections and the vertical deflection width is the minimum, the range shown by the dashed line 84 inside the range 83 becomes the effective screen, and if the outside is masked, the reproduced image is the same as normal, and there is no problem.

That is, according to the recorded tape 104 according to the present invention, when simply reproducing the recorded tape 104, the recorded tape 104 can be reproduced without any problem.

However, when dubbing this recorded tape 104 using two VTRs, the recording side that records the video signal from the tape 104
In the VTR, that is, the recording system 10 shown in FIG. 1, in response to the vertical synchronizing signal P _VV whose interval changes as described above in the reproduced video signal, a signal P whose interval changes as shown in FIG. 6 is sent from the frequency dividing circuit 22. _CV is retrieved,
Since the signal P _CV whose interval changes is used as the reference signal for controlling the rotational phase of heads 1 and 2, the servo of the rotational phase may be deviated, and when the video signal is recorded on the duplicate tape, The track pattern will be disrupted. Further, a signal P _CV whose interval changes is recorded on this copy tape by the head 26 as a control signal. Some VTRs are of a type in which pulses from the pulse generating means 24 are supplied as control signals to the heads 26 for recording.
Since the rotational phase of the signal is disturbed, control pulses with irregular intervals are recorded. Therefore, even if you play a duplicate tape that has been dubbed in this way,
The reproduced image becomes out of synchronization and becomes unwatchable.

That is, according to the recorded tape 104 according to the present invention, even if a duplicate tape is made by dubbing, only a completely useless duplicate tape will be made.
Dubbing can be prevented.

As described above, according to the recorded tape of the present invention, dubbing can be prevented without causing any problem in the reproduction itself. Moreover, this recorded tape can be played back on any VTR or monitor receiver, and conversely, it can be prevented from being dubbed by any VTR.

In producing the recorded tape of the present invention, a normal video signal is supplied to a special processor circuit to obtain a video signal in which the vertical synchronization pulse interval changes as described above, and this is processed as described above. It may also be recorded in the same way as .

Further, instead of the tape 104, a recording medium such as a magnetic recording medium or a so-called video disk may be used.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an example of a VTR, Fig. 2 is a waveform diagram for explaining the same, Fig. 3 is a diagram showing a recording pattern of a general tape, and Fig. 4 is a recorded tape manufacturing apparatus according to the present invention. FIG. 5 is a system diagram of an example of a recording VTR, FIG. 6 is an explanatory diagram, and FIG. 7 is a diagram showing an example of a storage pattern of a recorded tape according to the present invention. be. 50 is a TV camera, 60 is a recording VTR, 2
7 is an input terminal for the external synchronization signal, 70 is an oscillator, 71 and 72 are frequency dividing circuits, and 73 is a phase modulation circuit.

Claims (1)

[Claims] 1. An equal number of horizontal sections of video signals are recorded on each track, and between the plurality of tracks, the recording position of the vertical synchronizing pulse in the extending direction of the track is periodically different between the leading direction and the delaying direction. . A recorded recording medium, characterized in that control pulses are recorded at regular intervals corresponding to the track.