JPH02274078A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of S/N of a reproducing image and pitching caused by an elongation of a magnetic tape and a bend of a track, etc., and to obtain a satisfactory reproducing image by adding a pseudo vertical synchronizing signal to a reproducing video signal at the time of regular reproduction, as well. CONSTITUTION:When a noise is generated in a reproducing image due to an elongation of a magnetic tape and a bend of a track at the time of regular reproduction, and a control for tracking adjustment is operated so that the noise does not appear, in the case pitching is generated in the reproducing image, a switch 11 is closed to the C side. In such a way, a switch 7 is closed to the A side and a pseudo vertical synchronizing signal is added to a reproducing video signal, and accordingly, in a monitor television set, a vertical scan is executed by the added pseudo vertical synchronizing signal, and a stable reproducing image being free from a noise, and also, being free from pitching is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording and reproducing device for video signals using a helical scan method.

[Conventional technology]

Conventionally, in a helical scan type magnetic recording and reproducing device (hereinafter referred to as a VTR), tracking control is performed by a servo circuit in a normal reproduction mode so that the magnetic head correctly reproduces and scans each track on a magnetic tape. This makes it possible to stably obtain a reproduced image with a good S/N ratio. It also enables so-called special playback, in which playback is performed by running the magnetic tape at a speed different from that during recording.

By the way, in the case of special playback, a magnetic head diagonally crosses multiple tracks to perform playback scanning, but conventional VTRs
, an azimuth recording method is adopted in which the azimuth angle is different between adjacent tracks, and a guard band is eliminated between adjacent tracks to increase the recording density, so a trajectory that crosses the track diagonally is repeatedly scanned. In still reproduction, when a magnetic head reproduces and scans adjacent tracks having different azimuth angles, no video signal is reproduced from the adjacent tracks, and noise appears on the reproduction screen.

On the other hand, video signals for one field are recorded on each track on the magnetic tape, and the rotational phase of the magnetic head is controlled during recording so that the vertical synchronization signal is recorded at the end of the track. There is.

Therefore, in still reproduction, the scanning position of the magnetic head is controlled so that the scanning locus of the magnetic head best matches the center of the track with the same azimuth angle. As a result, the magnetic head deviates from the track the most at the end of the track, and no noise appears in the still reproduced image.

However, when the magnetic head performs still playback scanning as described above, the reproduction of the vertical synchronization signal recorded at the end of the track becomes insufficient, and the phase of the vertical synchronization signal from which the reproduced video signal is separated becomes unstable. becomes. As a result, the still image on the playback screen shakes vertically and becomes unstable.

As one way to solve this problem, for example, “NH
K Home Video Technology, April 20, 1980, published by Japan Broadcasting Publishing Association, pp. 180-184, describes a technology that forms a pseudo vertical synchronization signal with a stable phase during still playback and adds this to the playback video signal. Disclosed. This technique will be explained below with reference to FIG. In addition,
In the figure, 1.2 is a magnetic head, 3 is a signal processing circuit, 4 is a drum motor, 5 is a head switching signal generation circuit, and 6
1 is a pseudo vertical synchronizing signal generating circuit, 7 is a switch, 8 is an input terminal, 9 is an adder circuit, and 10 is an output terminal.

In the figure, video signals alternately reproduced from a magnetic tape (not shown) by a magnetic head 1.2 are supplied to a signal processing circuit 3. - In synchronization with the rotational phase of the drum motor 4 that rotates the magnetic heads 1 and 2, the head switching signal generation circuit 5 generates a head switching signal. In the signal processing circuit 3, based on this head switching signal, the reproduced video signals from the magnetic heads 1 and 2 are spliced into a continuous video signal, and further undergoes processing such as demodulation.

The switch 7 is controlled by a control signal from an input terminal 8, and is closed to the A side during special playback such as still playback, and to the B side during normal playback. Therefore, during normal playback, no signal is output from the switch 7, and the reproduced video signal output from the signal processing circuit 5 passes through the adder circuit 9 and is output from the output terminal 10.

On the other hand, the head switching signal output from the head switching signal generation circuit 5 is supplied to the pseudo vertical synchronization signal generation circuit 6, and a pseudo vertical synchronization signal of a predetermined phase is generated with respect to the reproduced video signal output from the signal processing circuit 6. generated and switch 7 A
Supplied on the side.

Therefore, during special playback, the switch 7 is closed to the A side by a control signal from the input terminal 8, and the pseudo vertical sync signal output from the pseudo vertical sync signal generation circuit 6 is supplied to the adder circuit 9 through the switch 7, and the signal is It is added to the reproduced video signal from the processing circuit 3.

As a result, during special playback, the monitor receiver performs vertical scanning using the pseudo vertical synchronization signal. Since this pseudo vertical synchronization signal has a stable phase, the displayed special playback image, such as a methyl image, is stable and free of vertical vibration.

[Problem to be solved by the invention]

Incidentally, in recent years, home VTRs have become widespread, and with this, opportunities to play back magnetic tapes recorded on other VTRs have increased.

However, the performance of each VTR is not exactly the same, and when playing back a magnetic tape recorded on another '/TR on your own VTR,
The magnetic tape may be stretched or the track may be significantly bent, and even during normal playback, tracking deviation may occur and noise may appear on the playback screen.

On the other hand, VTRs are usually provided with a knob for adjusting tracking theory, and by adjusting this knob, it is possible to prevent noise due to tracking deviation from appearing on the playback screen. However, when adjusting in this way, the magnetic head may be subject to large tracking deviations at the ends of the tracks where the vertical synchronization signal is recorded, and in such cases, the reproduction of the vertical synchronization signal may be insufficient. The reproduced image shakes vertically and becomes unstable.

In conventional VTRs, as mentioned above, consideration has been given to the instability of the reproduced image due to tracking deviation during special playback, but the reproduced image during normal playback due to elongation of the magnetic tape or bending of the track, etc. No consideration was given to the destabilization of the situation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording and reproducing apparatus that solves these problems and can always provide stable reproduced images even during normal reproduction.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a magnetic recording and reproducing apparatus configured to generate a pseudo vertical synchronizing signal, which includes a means for generating a control signal by an external operation, and a means for generating a reproduced image by the control signal during normal reproduction. means for adding the pseudo vertical synchronization signal to the signal.

The present invention also provides a magnetic recording and reproducing apparatus that generates a pseudo vertical synchronization signal, including a means for determining a vertical synchronization signal of a reproduced video signal, and an output from the means when the vertical synchronization signal is determined to be defective. and means for adding the pseudo vertical synchronization signal to the reproduced video signal according to a control signal.

[Effect]

In the former invention described above, during normal playback, if the reproduction of the vertical synchronization signal on the magnetic tape becomes defective due to elongation of the magnetic tape, track 9, etc., the reproduced image will be vertically shaken. However, by performing the above operation, a pseudo vertical synchronization signal is added to the reproduced video signal, and the monitor receiver performs vertical scanning using this pseudo vertical synchronization signal.

Therefore, even during normal playback, the vertical shake of the reproduced image is lost.

In addition, in the latter aspect of the present invention, if the reproduction of the vertical synchronization signal becomes defective as described above, this is detected and the vertical oscillation of the reproduced image is automatically added to the reproduced video signal during reproduction. I will lose it.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing device according to the present invention, in which 11 is a switch, 12 is an OR circuit, and parts corresponding to the third factor are given the same reference numerals and are duplicated. The explanation will be omitted.

In the figure, a pseudo vertical synchronization signal generation circuit 6 constantly supplies a pseudo vertical synchronization signal to the A side of a switch 7. The switch 7 is controlled by the output signal of the OR circuit 12, and when this output signal If HII (high level), the switch 7 is switched to the A side.
II L II (low level) (7) Close each to the Toki B side.

The control signal supplied from the input terminal 8 is
The signal is HIf, otherwise it is II L II, and is supplied to the switch 7 via the OR circuit 12.

Therefore, during special playback, the switch 7 is closed to the A side by the II HII control signal from the input terminal 8, as in the prior art shown in FIG. The pseudo vertical synchronizing signal is supplied to the adder circuit 9 and added to the reproduced video signal from the signal processing circuit 6.

Further, an output signal of the switch 11 which is manually switched is supplied to the switch 7 via an OR circuit 12 as a control signal. In the switch 11, the voltage source is connected to the C side and the D side is grounded. When the switch 11 is closed to the C side, the If HIf control signal is output, and when the switch 11 is closed to the D side, the II L II control signals are output. Ru. Even during normal playback when the control signal from the input terminal 8 is II L II, by closing the switch 11 to the C side, the control signal IIHll is supplied from the switch 11 to the switch 7 via the OR circuit 12, and the switch 7 closes to the A side. Therefore, even during normal playback, the pseudo vertical sync signal is supplied from the pseudo vertical sync signal generation circuit 6 to the adder circuit 9 via the switch 7, and is added to the reproduced video signal from the signal processing circuit 3. .

Therefore, during normal playback, noise may occur in the reproduced image due to elongation of the magnetic tape or bending of the track, and when you operate the tracking adjustment knob to prevent this noise from appearing, vertical shaking may occur in the reproduced image. Then, by closing the switch 11 to the C side, the switch 7 is closed to the A side, and a pseudo vertical synchronizing signal is added to the reproduced video signal. As a result, the monitor receiver performs vertical scanning using the added pseudo vertical synchronizing signal. As a result, a stable reproduced image without noise and pitching is obtained.

FIG. 2 is a block diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the present invention, in which 13 is a synchronization separation circuit, 14 is a synchronization failure determination circuit, and the parts corresponding to those in FIG. 1 are the same. Reference signs are added to omit redundant explanations.

In the figure, the reproduced video signal output from the signal processing circuit 5 is also supplied to a synchronization separation circuit 13, where the vertical synchronization signal is separated. This vertical synchronization signal is transmitted to the synchronization failure determination circuit 1.
4, the quality of the pseudo vertical synchronization signal from the pseudo vertical synchronization signal generation circuit 6 is determined.

Originally, during recording, control is performed so that the vertical synchronization signal of the recorded video signal and the head switching signal have a constant phase relationship, and during playback, they are also controlled so that they have this phase relationship. . For this reason, the pseudo vertical synchronization signal formed from the head switching signal must also be maintained in a predetermined phase relationship with the vertical synchronization signal of the reproduced video signal. Therefore, in the synchronization failure determination circuit 14, the vertical synchronization signal separated by the synchronization separation circuit 13 and the pseudo vertical synchronization signal are phase-compared, and the quality of the vertical synchronization signal is determined according to the phase relationship between them.

The synchronization failure determination circuit 14 outputs a control signal that becomes If HII when the vertical synchronization signal separated from the reproduced video signal is defective and becomes It L II when it is good. This control number 4M is supplied to the switch 7 via the OR circuit 12, and is closed to the A side when II HII.

As described above, in this embodiment, during normal playback,
If the reproduction of the vertical synchronization signal is insufficient due to the elongation of the magnetic tape or the curve of the track, this is automatically detected and a pseudo vertical synchronization signal is added to the reproduced video signal.
It is possible to prevent S/N deterioration and vertical shaking of reproduced video.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to add a pseudo vertical synchronization signal to the reproduced video signal even during normal reproduction, and the S/N of the reproduced image due to elongation of the magnetic tape, curvature of the track, etc. It is possible to prevent the deterioration and pitching of the image, and to obtain good reproduced images.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a block diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIG. 3 is a block diagram showing a conventional magnetic recording/reproducing apparatus. It is a block diagram showing an example of a device. 1.2... Magnetic head, Ro... Signal processing circuit, 4... Drum motor, 5...
Head switching signal generation circuit, 6...Pseudo vertical synchronization signal generation circuit, 7...Switch, 8...
- Control signal input terminal, 9... Addition circuit, 10
......Output terminal for playback video signal, 11...
・Switch, ...OR circuit, ...Synchronization separation circuit, 4 ...Synchronization failure judgment circuit. Diagram

Claims (1)

[Scope of Claims] 1. In a magnetic recording and reproducing apparatus that records and reproduces video signals on a magnetic tape using a rotating magnetic head, there is provided a first magnetic recording and reproducing apparatus that generates a pseudo vertical synchronization signal that is synchronized with the rotational phase of the rotating magnetic head. a second means that is operated from the outside and generates a control signal in response to the operation; and a second means that is controlled by the control signal during normal playback and adds the pseudo vertical synchronization signal to the reproduced video signal from the magnetic tape. 3. A magnetic recording and reproducing apparatus, characterized in that the pseudo vertical synchronizing signal can be added to the reproduced video signal at any time during normal reproduction. 2. In a magnetic recording and reproducing apparatus that records and reproduces video signals on a magnetic tape using a rotating magnetic head, a first means for generating a pseudo vertical synchronization signal synchronized with the rotational phase of the rotating magnetic head; and the magnetic tape. a second means for separating a vertical synchronizing signal from a reproduced video signal and determining whether the vertical synchronizing signal is good or bad; and a control signal from the second means accompanying the determination that the vertical synchronizing signal is defective. and a third means for adding the pseudo vertical synchronizing signal to the video signal, so that the pseudo vertical synchronizing signal can be added to the reproduced video signal when there is a reproduction failure of the vertical synchronizing signal during normal playback. A magnetic recording and reproducing device. 3. In claim 2, the second means determines the quality of the vertical synchronization signal by comparing the phases of the vertical synchronization signal separated from the reproduced video signal and the pseudo vertical synchronization signal. A magnetic recording/reproducing device characterized by: 4. The magnetic recording and reproducing apparatus according to claim 1, 2 or 3, wherein the third means adds the pseudo vertical synchronization signal to the reproduced video signal even during special reproduction.