JPS6132677A - Recording and reproducing method of magnetic tape - Google Patents

Abstract

PURPOSE:To shut off only the confused part of reproduced signal generating at recording an information signal by shutting off the signal from one magnetic head only in the period in which video signal reproduced by one magnetic head and an information signal by other magnetic head are recorded. CONSTITUTION:A control device 12 reads the video signal recorded in a magnetic tape 2, judges whether or not an information signal from input device 14 is recorded, and a video signal from the magnetic tape 2 is inputted to a processing circuit 16 through a line l1, the output of a magnetic head M1 is shut off at the processing circuit 16 to add a horizontal synchronous signal. Thus, the picture plane is prevented from slipping off. A clamp circuit 17 cramps the signal from the processing circuit 16 to input the signal to an output circuit 18 through a switch SW1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic tape recording and reproducing method for recording and reproducing video signals and information signals.

BACKGROUND ART FIG. 4 is a simplified plan view of the magnetic drum 1. The magnetic drum 1 is equipped with magnetic heads Ml and M2. ``Video signals and information signals are recorded and reproduced on the magnetic tape 2 by magnetic heads Ml and M2. When recording and reproducing video signals and information signals, the magnetic drum 1 rotates at high speed.

The first angle θ1 at which the magnetic tape 2 is wound around the magnetic drum 1 is approximately 220 degrees, of which 180 degrees corresponds to an area for recording video signals, and 36 degrees corresponds to an area for recording information signals. It corresponds to the area of magnetic head Ml,
The video signal reproduced by M2 is shown in FIG. Usuki Hey FMI, M2 is magnetic 1'? Since the AIL second angle is 180 degrees apart, the magnetic head M
When the magnetic head M1 enters an area where an information signal is to be recorded after recording a video signal in a 180 degree area, the magnetic head M1 starts recording the video signal. On the other hand, magnetic head M
When the magnetic head M2 is recording an information signal, the magnetic head M2 starts recording a video signal. That is, the magnetic heads M1 and M2 operate simultaneously.

When recording an information signal in accordance with the reproduced video, for example, the magnetic head M1 performs reproduction and the magnetic head M2 records the information signal.

The rotary transformer 3 shown in FIG. 4 then causes so-called crosstalk between the b1 recording signal and the reproduction signal. The difference between the recorded signal and the reproduced signal is several tens of dB, and since the recorded signal is high, there are parts in the rotary transformer 3 where the recorded signal causes disturbances in the reproduced signal.

FIG. 6 is a diagram showing the timing of video signals and information signals. The upper part of FIG. 6 is a signal processed by the magnetic head M1, and the lower part is composed of an information signal s1 for changing the mode of the magnetic head M and a video signal S2 for one screen. The signal s2 has a portion 82a where the above-mentioned disturbance occurs. The regenerated portion of the disturbed portion 82a is shown in FIG. 7(1).
This corresponds to the part indicated by reference numeral N in .

Problems to be Solved by the Invention In such prior art, the problem is that the reproduced image is disturbed due to the power difference between the recording signal and the reproduction signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic tape recording and reproducing method that can block only the disturbed portions of reproduced video that occur when recording information signals.

Means for Solving the Problems The present invention interrupts the signal from one magnetic head only during the period when the video signal being reproduced by one magnetic head is being recorded by another magnetic head. ,
A magnetic tape recording and reproducing method is characterized in that a synchronizing signal is added to a line from which a signal from one magnetic head is derived.

According to the present invention, the signal from one magnetic head is blocked only during the period when the video signal being reproduced by one magnetic head is being recorded by another magnetic head. Since a synchronizing signal is added to the line from which the signal is derived, it is possible to block only the disturbed portion of the reproduced video.

Embodiment FIG. 1 is a block diagram of a playback device 10 according to an embodiment of the present invention, FIG. 2 is a block diagram of a video device 11, and FIG. 3 is a 70-chart for explaining the operation of the control device 12. be. The present invention will be described with reference to FIGS. 4 to 7. A video device 11 sends a video signal from a television receiver 13 and an information signal from an input device 14 to a recording device 1.
5, and a playback device 10 plays back the data. The information signal is PCM (Pulse Co
deM.

This is a signal that changes the display mode of the video signal from the television receiver 13. Assume now that the head that reads the reproduced signal is the magnetic head M1, and the magnetic head that records the information signal is the magnetic head M2.

When the control device 12 starts control, it transfers control from step n1 to step n2. In step n2, the video signal recorded on the magnetic tape 2 is read. step n
3, it is determined whether or not to record the information signal from the input device 14. If it is determined in step n3 that the information signal is to be recorded, step n4
control is transferred to In step n4, magnetic tape 2
A video signal is input to a processing circuit 16 via a line 11. The processing circuit 16 cuts off the output of the magnetic head M1.

When the output of the magnetic head M1 is cut off in step n4, a shifted portion N1 of the reproduced image occurs as shown in FIG. 7(2). The reason for this is shown below.

Referring to FIG. 5, when the video signal is cut off, the cut off waveform becomes a so-called synchronization head level indicated by reference numeral SH. Since the vertical synchronization signal has a width of, for example, 3H, the 3H portion of the interrupted signal is mistakenly recognized as the vertical synchronization signal, and is mistakenly recognized as the beginning of the screen. For this reason the reference P
The position indicated by 1 is the top of the screen. Further, the remaining part of the blocked signal becomes a no-signal part, which turns black and becomes a shifted part N1. The video signal corresponding to the position indicated by reference numeral P1 in FIG. 7 is shown in FIG. 6 with the same reference numeral.

In step n5, the processing circuit 16 adds a horizontal synchronizing signal to the interrupted reproduction signal. This prevents the screen from shifting. Clamp circuit 17 clamps the signal from processing circuit 16. The output from clamp circuit 17 is input to output circuit 18 via switch SWI. At this time, the switch SW1 is connected to the terminal sa by a signal from the control device 12. In step n6, the output circuit 18 outputs the video signal to the television receiver 13. Control ends at step n7.

When it is determined in step n3 that the information signal is not to be recorded, control moves to step n6. At this time, the video signal from the magnetic tape 2 is FIN! 2 to the clamp circuit 19.

The clamp circuit 19 clamps the video signal from the magnetic tape 2 and outputs the video signal to the output circuit 18 via the switch SWI. At this time, switch SW1 is connected to terminal sb. The output circuit 18 outputs the video signal to the television receiver 13 in step n6.

When recording an information signal in this way, if the reproduction signal is cut off and only the horizontal synchronization signal is output to the television receiver 13, the reproduced video will be the same as the video signal as shown in FIG. 7(3). Only the disturbed parts are blocked.

Furthermore, by adding information such as characters to the portion of the video signal that has been cut off by the processing circuit 16, it is possible to indicate that the information signal is being recorded.

In the above embodiment, the case where there are two magnetic heads is described, but the number of magnetic heads may be two or more.

Effects As described above, according to the present invention, it is possible to block only the disturbed portion of the reproduced signal that occurs when recording the information signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a playback device 10 according to an embodiment of the present invention, FIG. 2 is a block diagram of a video device 11, FIG. 3 is a 70-chart for explaining the operation of the control device 12, and FIG.
5 is a diagram showing the video signal, FIG. 6 is a diagram showing the timing of the video signal and information signal, and FIG. 7 is a diagram showing the display screen. 1...Magnetic drum, 2...Magnetic tape, 10...
Reproducing device, 11...Video device, 12...Control device, 13...Television receiver, Ml, M2...Magnetic head, 11, J22...Line agent Patent attorney Keiichi Hayabusa 1L hair position Fig. 1 Fig. 2 Fig. 3 Fig. 4 H Fig. 5 Fig. 7

Claims (1)

[Claims] A magnetic tape is wound around a rotating drum over a predetermined first angle, and a plurality of magnetic heads for recording and reproducing are attached to the rotating drum at a second angle smaller than the first angle. , a plurality of magnetic heads can store video signals and information signals including synchronization signals in their individually corresponding storage areas, and a single magnetic head can play back video signals recorded on a magnetic tape. When an information signal is recorded by another magnetic head, the video signal including the synchronization signal from the one magnetic head is cut off only during the period when the information signal is being recorded, and the video signal including the synchronization signal from the one magnetic head is interrupted. A magnetic tape recording and reproducing method characterized in that a separately generated synchronization signal synchronized with a synchronization signal included in the video signal is added to a line from which a signal from a magnetic head is derived.