JPS6011512B2 - Recorded recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION With the spread of VTRs (magnetic key image reproduction devices), pre-recorded video tapes containing movies and the like are now on sale to the general public.

By the way, if you prepare two VTRs, you can easily dub copies from this recorded tape. However, this kind of dubbing from recorded tapes is prohibited by law. However, when dubbing is carried out on a small scale in ordinary households, it is impossible to control this, which is inconvenient for tape distributors and copyright holders. From this point of view, the present invention aims to provide a recorded recording medium in which a normal playback screen cannot be obtained from a duplicate tape even if a duplicate tape is produced by dubbing.

Hereinafter, an example of a recorded recording medium according to the present invention will be explained using a tape as an example.

The present invention aims to prevent dubbing by specially processing the video signal to be recorded.
An example of a method for producing a recorded tape according to the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, 1 and 2 are a pair of rotating magnetic heads, which have an angular spacing of 1800 and are driven by a motor 4 at a frame frequency, i.e., at a rate of 3 m/s. It can be rotated with

Further, the magnetic tape 3 is wound obliquely over an angular range of approximately 188C with respect to the rotating peripheral surfaces of the heads 1 and 2, and is transported at a constant speed. - Then, the video signal Sv (Pc is a synchronization pulse) shown in FIG.
is supplied to the heads 1 and 2 through the recording circuit 13.

Then, this addition signal Sv^ is extracted as, for example, the following signal. That is, the video signal Sv is
4, from which the synchronization signal Pc (
PH is a horizontal synchronization pulse, PE is an equalization pulse, and Pv is a vertical synchronization pulse).After this signal Pc, the monostable multipipelator 15 is triggered at green, and from this, a pulse signal P is obtained.

(FIG. 2C) is obtained and supplied to the gate circuit 16. The synchronizing signal Pc is also supplied to the integrating circuit 17, which forms an integral signal S, (FIG. 2D). , and falls near the end of the period tv of the vertical synchronizing pulse Pv (Fig. 2E) is obtained. 19 is triggered, and a signal Sc (FIG. 2 F) rises near the end of the vertical synchronizing pulse period tv and falls several horizontal intervals before the vertical synchronizing pulse Pv of the next field. can get. Then, this signal Sc is supplied as a gate signal to the gate circuit 16, and this gate circuit 16 receives the "0" period tG of this signal Sc, that is, the vertical synchronizing pulse Pv
The signal P^ is turned on in the interval tv and the interval before the horizontal interval, and the pulse signal Po from the monostable multipipulator 15 is attached from this gate circuit 16 for the interval tc (Fig. 2 G). is obtained, and this signal P^ is supplied to the adder circuit 12, where it is added to the video signal Sv from the input terminal 11, and from this, the added signal Sv^ is obtained as shown in Fig. 2 H'. , the interval tG
The bed scale level in a certain section after the horizontal synchronizing pulse PH and the equalizing pulse PE is made equal to the peak value of these pulses, and the section tv of the vertical synchronizing pulse is made equal to the peak value of the synchronizing signal Pc. A signal equal to bell is taken out.

20' shows the servo circuit in this case, and the integral signal SI from the integrating circuit 17 is supplied to the frequency dividing circuit 21, from which a signal with a frequency of 30 days 2 is taken out, and this signal is sent to the phase comparator circuit 22. supplied to

Further, a pulse generating means 23 is provided on, for example, the rotating shaft 5 of the heads 1 and 2, and from this, a pulse indicating the rotational phase of each rotation of the heads 1 and 2 is taken out and supplied to the phase comparator circuit 22. . In this way, in the phase comparator circuit 22, the 30Hz signal from the frequency divider circuit 21 and
The phase of the pulse from the pulse generating means 23 is compared, and the comparison output is supplied to the motor 4 through the amplifier 24.
As a result, the rotational phases of heads 1 and 2 are servo-controlled, and one field of the video signal Sv^ from the recording circuit 13 becomes one diagonal magnetic track, and vertical planking is performed at the end of the magnetic track. It is recorded on tape 3 so that the period is reached.

At this time, the signal from the frequency dividing circuit 21 is combined with the magnetic head 25, and the frequency divided signal is recorded as a control signal on the tape 3 by forming a magnetic track in its length direction. Next, consider the case of dubbing to create a duplicate tape 33 from this recorded tape 3. In this case, the slave side VTR outputs a synchronizing signal after its recording system has clamped the vedestal level of the video signal. Use something that separates it.

In FIG. 3, 40 is a slave side VTR, and 60 is a master side VTR. In the slave-side VTR 40', 31 and 32 are rotating magnetic heads, and 34 is a motor that rotates these heads 31 and 32. This is the same as the running system for the heads 1, 2, motor 4, and tape 3. Then, the video signal Sv^ reproduced from tape 3 from VTR 6 Kawako on the master side (Figure 4 A)
is supplied to the rotating magnetic heads 31 and 32 through the recording circuit 42 through the input terminal 41 of the slave side VTR 40.

Further, the video signal SvA from the input terminal 41 is supplied to a clamp circuit 43, and an oscillator 44 is provided. A pulse signal Po having a phase matching the vedestal position is obtained and is supplied to the clamp circuit 43.

Then, in this clamp circuit 43, this pulse signal P. The video signal Sv sampled in the pulse interval of
The level of ^ is clamped to a certain level Ec. By the way, in the video signal Sv^, the portion to be sampled is the vedestal after the synchronizing pulse Pc in sections other than the section tG, but in the section t. In this case, the video signal S
Since the vedestal after the synchronization pulse v^ has been changed to the peak value of the synchronization pulse Pc, it is the peak value of the synchronization pulse Pc in this interval tc. Therefore, in the interval other than the interval tc of the video signal SvA from the clamp circuit 43, the pulse signal Po samples the vedestal after the synchronizing signal Pc, and the vedestal of the video signal is clamped to a constant level Ec. In the signal interval tG, the peak value of the synchronization signal is the pulse signal P.

In this period to, a video signal Svc (FIG. 4C) in which the level of the peak value of the synchronizing signal Pc is clamped to a constant level Ec is extracted. In this case, the video signal Sv^ has its vertical synchronization pulse P
Since the interval tv of v is the peak value of all the synchronizing pulses Pc, this interval tv is also at a constant level Ec. Then, this clamped video signal Svc is supplied to the sync separation circuit 45 and sync-separated, and the output signal Pcc is assumed to have a sync pulse missing in the interval tc, as shown in FIG. 4D.

In this case, in order to accurately match the phase of the output pulse PH of the oscillator 44 to the position of the vedestal after the synchronization signal of the normal video signal, the synchronization pulse P from the synchronization separation circuit 45 is used.
cc is supplied to a phase comparison circuit 46, while the output pulse Po of the oscillator 44 is supplied to this phase comparison circuit 46, the phases of both signals are compared, and the comparison output is supplied to the oscillator 44. . The pulse Pcc synchronously separated in this way is supplied to a servo circuit 50 similar to the servo circuit 20 in FIG. However, the outputs S and c of the integrating circuit 51 are as shown in FIG. 4E, and since only a DC signal is obtained from the frequency dividing circuit 52, the rotational phases of the heads 1 and 2 are not servo-controlled.

Further, since the signal from the frequency dividing circuit 52 is a direct current, the control signal is not recorded on the tape 33 by the head 55.

Therefore, even if the dubbed tape 33 is loaded into a playback device in order to obtain a playback video signal, since there is no control signal, the heads 1 and 2 cannot accurately scan the tracks on which the video signals are recorded. Or, since the recorded signal is not subjected to recording servo, the reproduced image displayed on the monitor's receiver becomes unwatchable.

As described above, according to the present invention, dubbing can be effectively prevented by specially processing a video signal to be recorded on a tape as a recorded tape.

In addition, in the above example, the vedestal level was changed to a level equal to the peak value of the sync pulse, but by simply changing the vedestal level to the peak value side of the sync pulse, the peak value becomes equal to the bell. You don't have to.

Furthermore, the recording medium may be a magnetic sheet or a so-called video disk instead of a tape.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of a recording system of the method for producing a recorded tape according to the present invention, FIG. 2 is a waveform diagram for explaining the method, and FIG. 3 is a diagram of a recording system for dubbing a recorded tape according to the present invention. An example of a system diagram, FIG. 4, is a waveform diagram for explaining the system. 1, 2, 31 and 32 are rotating magnetic heads, 13 and 43
is a recording circuit, 14 and 45 are synchronous separation circuits, 15, 18
and 19 are monostable multipipelators, 17 and 51 are integrating circuits, 21 and 62 are frequency dividing circuits, 22 and 53 are phase comparison circuits, 23 and 54 are pulse generating means, 43 is a clamp circuit, and 44 is an oscillator. . Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A recorded recording medium on which a video signal is recorded in which the pedestal level is changed to the peak value side of the synchronization signal in the period of the vertical synchronization pulse and some horizontal period before the vertical synchronization pulse.