JPS6213874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION With the spread of VTRs (magnetic recording and reproducing devices), recorded video tapes containing movies and the like have been sold. However, two
If you have a VTR, you can easily dub copies from recorded tapes.

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 provides a VTR that prevents dubbing of recorded tapes.
(recording device).

First, an example of a method for producing a recorded tape will be explained.

In Figure 1, 1 is the master VTR (for playback).
VTR), 10 indicates a slave VTR (recording VTR) for producing a recorded tape, and a luminance signal Sa (Pv is a vertical synchronization pulse) is recorded on the master tape in the master VTR 1 as shown in FIG. 2A. At the same time, as shown in FIG. 2B, on the auxiliary track of this master tape, a pulse Pb indicating the cut is recorded for each cut of the scene (cut) of the luminance signal Sa.

In this case, when recording the brightness signal Sa from the TV camera on the master tape or its original tape, this pulse Pb shapes the switching signal of the TV camera and records the brightness signal Sa on the master tape or original tape at the same time. Alternatively, the brightness signal Sa may be recorded on a master tape or an original tape, and then played back to find a scene break and recorded.

In the master VTR 1, the luminance signal Sa is reproduced from the master tape and is supplied to the input terminal 11 of the slave VTR 10, and at the same time, the pulse Pb is also reproduced, and this is supplied to the input terminal 21 of the slave VTR 10.
supplied to And the brightness signal from terminal 11
Sa is supplied to the vertical synchronization pulse removal circuit 12 and also supplied to the synchronization separation circuit 22, from which the vertical synchronization pulse Pv is taken out as shown in FIG. 2C, and this pulse Pv is removed. is supplied to the circuit 12 as its control signal, and the removal circuit 1
As shown in FIG. 2D, the luminance signal Sd obtained by removing the vertical synchronizing pulse Pv from the luminance signal Sa is extracted from the luminance signal Sd. This luminance signal Sd is then supplied to the adder circuit 13.

Furthermore, the vertical synchronization pulse Pv from the separation circuit 22
is supplied to the vertical synchronization pulse forming circuit 23 to form a vertical synchronization pulse, and this pulse is supplied to the phase modulation circuit 24 as its carrier wave.
The pulse Pb from the terminal 21 is supplied to the flip-flop circuit 25, and as shown in FIG. is supplied to the modulation circuit 24 as its modulation input.

Therefore, the modulation circuit 24 outputs a modulated output as shown in FIG. A vertical synchronization pulse Pu whose phase is delayed from the regular vertical synchronization pulse Pv by the period is obtained.

This pulse Pu is then supplied to the adder circuit 13, where the pulse Pu is added to the luminance signal Sd, and as shown in FIG. A brightness signal Sg is formed, and this signal Sg is supplied to an FM modulation circuit 14 and converted into an FM signal, and this signal is supplied to, for example, two rotating magnetic heads 16 and 17 through a recording amplifier 15.

The heads 16, 17 have an angular spacing of 180° and are rotated by a motor 18 at a frame frequency, that is, 30 times per second, and the magnetic tape 30 is rotated approximately 180° relative to the rotating circumference. It is circulated diagonally over an angular range of 100° and is transported at a constant speed.

Further, 40 indicates a servo circuit, and the separation circuit 22
The vertical synchronizing pulse Pv from is supplied to the frequency dividing circuit 41 and frequency-divided into pulses Pf of the frame frequency, and this frequency-divided pulse Pf is supplied to the phase comparator circuit 42.

Furthermore, for example, the rotating shaft 19 of the heads 16 and 17
A pulse generating means 43 is provided, and from now on,
A pulse Pg indicating the rotational phase of each rotation of the heads 16 and 17 is taken out, and this pulse Pg is supplied to a comparator circuit 42 through a shaping amplifier 44.

In this way, in the comparator circuit 42, the pulses Pf,
Pg is phase compared and the comparison output is the amplifier 45
The FM signal supplied to the heads 16 and 17 by servo-controlling the rotational phase of the heads 16 and 17 is such that one field becomes one diagonal magnetic track, and the magnetic The tape 30 is recorded with vertical blanking periods at the ends of the tracks.

Also, at this time, the frequency divided pulse from the frequency dividing circuit 41
Pf is supplied to the magnetic head 47 through the recording amplifier 46, and this frequency-divided pulse Pf is recorded on the tape 30 as a magnetic track in the length direction of the tape 30. Note that this frequency-divided pulse Pf is used for tracking servo of the rotating magnetic head during reproduction.

In this way, the brightness signal Sa from the master VTR1 is
In the slave VTR 10, the brightness signal Sg having a vertical synchronization pulse Pu that is phase-modulated for each scene is recorded on the tape 30, that is, the recorded tape 30 is produced.

Recorded tape 30 produced in this way
When playing back on a general VTR or monitor receiver, the tracking servo of the rotating head of the VTR during playback is performed by the divided pulse Pf recorded on the tape 30 by the head 47, so that the recorded A brightness signal Sg is reproduced from the tape 30 and supplied to a monitor receiver. At this time, in the luminance signal Sg, the vertical synchronization pulse Pu is phase-modulated for each scene, so the playback screen on the monitor receiver shifts upward or downward at the scene break, and gradually settles into a steady position. However, by keeping the amount of phase shift with respect to the vertical synchronization pulse Pu small, the deviation of the reproduced screen at the scene break is small, and there is no problem in practical use. Especially since it shifts at the scene break, there is no problem. That is, when simply reproducing the recorded tape 30, it can be reproduced without any problem.

The VTR of the present invention is such that it is not possible to record on such recorded tape 30 during dubbing.

That is, in FIG. 3, reference numeral 110 indicates a VTR according to the present invention, and a luminance signal is supplied to an FM modulation circuit 114 through an input terminal 111 and converted into an FM signal, and this FM signal is sent to a recording amplifier 115.
and is supplied to rotating magnetic heads 116 and 117 through a switching circuit 100 for muting.

These heads 116, 117 and magnetic tape 13
0, the servo circuit 140 is the slave shown in FIG.
It has the same structure as the VTR 10, and corresponding parts are numbered 100 more than those in FIG. 1, and their explanation will be omitted. In addition, 12
2 is a vertical synchronization pulse separation circuit.

Further, the switch circuit 100 is turned on during general recording and turned off when dubbing the recorded tape 30, and 150 is a discrimination circuit that detects and discriminates between the general recording and the dubbing recording.

That is, the comparison circuit 142 outputs a voltage Vi whose level changes in accordance with the phase difference between the frequency-divided pulse Pf and the pulse Pg.

When a general luminance signal is supplied to the terminal 111 (during general recording), during steady state,
Since the pulse Pf is a pulse obtained by dividing the vertical synchronizing pulse of the input luminance signal, it has a constant phase, and since the rotational phase of the heads 116 and 117 is also almost constant, the pulse Pg also has a nearly constant phase. , Therefore, the phase difference between pulse Pf and pulse Pg is
Since it is approximately constant, the comparison voltage Vi is approximately a direct current voltage. And if this voltage Vi changes, this will change the voltage of the head 11 for the input luminance signal.
This is to maintain the synchronization of the rotational phases of 6,117, so the level change is extremely small and the frequency is extremely low.

On the other hand, the recorded tape 30 is connected to the terminal 111.
When the luminance signal Sg from the luminance signal Sg is supplied (during dubbing recording), the pulse Pf is a pulse obtained by frequency-dividing the vertical synchronization pulse Pu of the luminance signal Sg, so the phase of the pulse Pf changes due to phase modulation. Since the rotational phases of the heads 116 and 117 try to synchronize with this, the comparison voltage Vi includes the AC voltage ΔV, and this AC voltage ΔV is affected by the phase modulation of the vertical synchronization pulse Pu. The corresponding level and frequency will be obtained.

Therefore, by detecting whether or not the comparison voltage Vi includes the AC voltage ΔV, it is possible to distinguish between normal recording and dubbing recording.

Therefore, this comparison voltage Vi is determined by the discrimination circuit 150.
The switch circuit 100 is turned off at the time of dubbing recording based on the discrimination output.

That is, the comparison voltage Vi is supplied to the high-pass filter 151 and the AC voltage ΔV is taken out.
This AC voltage ΔV is supplied to the rectifier circuit 152 to become a DC voltage Vr, and this voltage Vr is applied to the switch circuit 100 through the source follower FET 153.
When the voltage Vr is obtained,
Switch circuit 100 is turned off.

Further, 155 indicates a reset circuit. That is, the voltage ΔV from the filter 151 is supplied to the differentiating circuit 156 and differentiated, and the differentiated pulse is
Pd is supplied to the shaping circuit 157 to generate a differential pulse
After Pd is obtained, a pulse Ps that rises for a certain period of time is formed, and this shaped pulse Ps is supplied to the base of the transistor 158, and between the collector and emitter of this transistor 158,
It is connected in parallel to the output end of the rectifier circuit 152.

According to this configuration, during general recording,
Since the comparison voltage Vi does not include the AC voltage ΔV, the DC voltage Vr cannot be obtained, and therefore the switch circuit 100 is on, so recording is performed in the same way as a normal VTR.

However, during dubbing recording, the comparison voltage Vi includes the AC voltage ΔV and the DC voltage Vr is obtained, so the switch circuit 100 is turned off and recording is no longer possible. Therefore, dubbing of the recorded tape 30 can be prevented.

Also, during general recording, momentary noises such as when switching reception channels may occur on the pulse Pf.
, the instantaneous noise voltage is included in the comparison voltage Vi, but this noise voltage is absorbed by the smoothing capacitor of the rectifier circuit 152, and therefore the switch circuit 100 is absorbed by the instantaneous noise. never turns off.

Furthermore, even during general recording, the rotational phases of the heads 116 and 117 are not stable for a certain period of time at the start of recording, so the comparison voltage Vi includes an alternating current voltage similar to the alternating current voltage ΔV.

However, when such an alternating voltage is generated, a differential pulse Pd is simultaneously obtained and a pulse Ps is formed, which turns on the transistor 158 for a certain period of time and shortens the output end of the rectifier circuit 152. Therefore, even if the comparison voltage Vi includes an AC voltage similar to the AC voltage ΔV for a short period at the start of general recording, the switch circuit 100 is not turned off and recording continues.

However, during dubbing recording, the comparison voltage Vi continuously includes the AC voltage ΔV, so even if the transistor 158 is turned off, the DC voltage Vr is obtained, and therefore recording cannot be performed.

Such an operation is similarly performed for the above-mentioned instantaneous noise.

Thus, according to the invention, recorded tape 30
can prevent dubbing. Moreover, since the recording itself cannot be performed during dubbing, dubbing can be reliably prevented.

In the example shown in FIG. 4, dubbing is prevented by digitally detecting and determining the phase difference between pulses Pf and Pg.

That is, during normal recording, the phase difference between pulses Pg and Pf is almost constant and small, as shown on the left side of Figure 5A and B, but during dubbing recording, as shown on the right side of the figure, Vertical sync pulse Pu
The phase difference between pulses Pg and Pf changes and becomes larger in response to the phase modulation of .

Therefore, these pulses Pg and Pf are supplied to the RS flip-flop circuit 161, and as shown in FIG. 5C, a pulse Pc is formed which rises at the rising edge of the pulse Pg and falls at the rising edge of the pulse Pf. Further, the pulse Pg is supplied to the monostable multivibrator 162 and falls at the rising edge of the pulse Pg, as shown in FIG. The pulse that is falling only
Pi is formed.

And these pulses Pc and Pi are AND circuit 1
63. Therefore, as shown in FIG. 5E, from the AND circuit 163, a signal Sj is obtained which has a falling edge during normal recording, and which becomes a pulse with a frame period during dubbing recording.

This signal Sj is then supplied to a retriggerable type monostable multivibrator 164, and the fifth
As shown in FIG.
is falling, the switch circuit 10
0 is turned on, and when it is rising, it is turned off.

Therefore, general recording can be done in the same way as with a normal VTR, but recording during dubbing is no longer possible.

In addition, in this example, at the start of general recording,
This signal indicating the start of recording is supplied to the multivibrator 164 through the terminal 165, and the signal Sk
is lowered until the rotation of the heads 116, 117 is stabilized.

Thus, according to the present invention, dubbing of the recorded tape 30 can be prevented without interfering with general recording.

In the example of FIG. 3, the circuits 156 and 157
Alternatively, as in the example of FIG. 4, the transistor 158 may be turned on for a certain period of time from the start of recording by a signal indicating the start of recording. In the example of FIG. 4, instead of the multivibrator 164, an integrating circuit and a shaping circuit may be used to obtain the signal Sk from the signal Sj. Furthermore, switch circuit 1
00 may be in the previous stage of the modulation circuit 114.

Furthermore, in the luminance signal Sg of FIGS. 1 and 2, the vertical synchronization pulse Pu is phase-modulated so that it is located at a position shifted by a certain amount from the original vertical synchronization pulse Pv position. The phase of the vertical synchronizing pulse may be modulated so that the horizontal frequency is constant and the number of scanning lines in each field period changes continuously. In addition, without phase modulating the vertical synchronizing pulse, for example, as shown in FIG. The period may be continuously (or intermittently) set to the sync chip level as the pseudo vertical synchronizing pulse Pw.

Furthermore, in the above description, the phase of all the pseudo vertical synchronization pulses Pu is delayed in the even-numbered scenes, but the phase may be changed by, for example, only the first vertical synchronization pulse Pu of the even-numbered scenes. Alternatively, a vertical synchronization pulse Pu having a phase shift may be prepared in advance and replaced with, for example, all of the even-numbered scenes or the first vertical synchronization pulse Pv.

Furthermore, if the scene is dark, even if the playback screen shifts instantaneously upward or downward, it will not be noticeable, so instead of or in addition to the scene break, change the phase of the vertical synchronization pulse Pu in the dark scene. It's okay. Furthermore, instead of the pulse Pb, a signal Se may be recorded on the master tape or the original tape as a signal indicating a scene break.

Further, instead of the tapes 30, 130, a recording medium such as a magnetic card or a so-called video disk may be used.

Furthermore, the phase shift amount of the vertical synchronization pulse Pu is large,
In the case of being located in the vertical scanning period, blanking may be performed with the luminance signal Sg at the black level until the time of the pulse Pu.

Furthermore, if the brightness signal of the television broadcast is as described above, the television broadcast can be prevented from being recorded.

[Brief explanation of the drawing]

Figure 1 is a system diagram of an example of a slave VTR, Figure 2 is a system diagram of an example of a slave VTR.
The figure is a waveform diagram for explaining the same, FIGS. 3 and 4 are system diagrams of an example of the present invention, and FIGS. 5 and 6 are waveform diagrams for explaining the same. 140 is a servo circuit, and 150 is a discrimination circuit.

Claims (1)

[Claims] 1 The recording head and the recording medium are moved periodically to record the luminance signal, and at the time of this recording, the relative movement between the recording head and the recording medium is detected by a signal indicating this movement. In the recording device, synchronization is performed with the vertical synchronization signal based on a phase comparison output between the luminance signal and the vertical synchronization signal included in the luminance signal, a switch circuit for muting is provided in the signal path of the luminance signal, and master recording is performed. A luminance signal having a vertical synchronization signal phase-modulated for each scene is reproduced from the medium and recorded by the recording device, and at the time of recording, it is determined that the phase modulation is performed, and based on this determination, the switch circuit A luminance signal recording device configured to prevent recording of a reproduced luminance signal having the phase-modulated vertical synchronization signal by controlling the above.