JPS6257149B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus that allows good still reproduction.

Rotating head type magnetic recording/playback device, e.g. for home use
In a VTR or the like, still playback can be performed by stopping the running of the magnetic tape while the rotary head cylinder is rotating. However, if the running of the tape is stopped at random, the trajectory of the rotating magnetic head relative to the recording track during reproduction is not always in an optimal state, and there is a problem in that noise bands appear on the reproduced image surface.

For this reason, in the past, for example, after a still command, the tape was run at a sufficiently low speed, and when it was detected that the dropout output of the playback video signal corresponding to the appearing noise band entered the vertical retrace period, the tape run was stopped. However, efforts were being made to realize noiseless playback.

This situation will be explained with reference to the drawings in the case of an azimuth recording method in which recording and reproduction are performed by changing the gap angles of two rotary heads.

In FIG. 1, A1 and A2 indicate recording tracks by one of the two heads, for example, head A, and B1 and B2 indicate tracks recorded by the other head, for example, head B. If A is an odd field, , B form an even field, and A1 and B1 form one frame. Arrow T
is the tape running direction, arrow H is the head rotation direction, and dotted line 1 is an example of the rotating head trajectory when stopped at the optimum position. It can be seen that the A head output increases, the B head output decreases, and the dropout C is pushed to the lower end of the A1 recording track, that is, the vertical blanking period.

In this case, since the vertical synchronization signal is corrupted, it has been considered to add a pseudo vertical synchronization signal before the corrupted original vertical synchronization signal. Pseudo vertical synchronization signal to be added (hereinafter referred to as additional V pulse)
An example of this is shown in Figure 2b. Figure a shows a head switching signal indicating the start timing of the head.

As can be seen from Figure 1, the start of the B head coincides with the bottom of the B1 recording track, but
The head starts from the bottom of the A1 recording track and _αH.
There is a difference of (number of deviations in H between A track and B track).

Therefore, the phase of the additional V pulse during the A head regeneration period must be delayed by α _H compared to that during the B head regeneration period. That is, in Figure 2b, t ₁
The relationship −t ₂ = α _H holds true.

As explained above, in conventional still playback, a fixed even or odd field is stopped at a position where a dropout occurs during the vertical blanking period of a fixed field, and an additional V pulse is generated accordingly. . For this reason, the next position that can be stopped after head trajectory 1 is the position of the head trajectory shown at 2 in FIG. 1, and it will be stopped every frame. Therefore, in this method, the evenness of the field for detecting dropout, that is, the type of head, is fixed.

However, since the two heads have different outputs, variations in installation, etc., there is also a difference in the stability with which dropouts occur. This is a manufacturing issue and cannot be predicted and designed in advance. Therefore, if the vehicle stops on the less stable side of dropout, there is a drawback that the stopping accuracy is poor.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to improve stopping accuracy and to provide a still image without vertical fluctuation, by constantly stopping a magnetic tape on the side where dropout appears stably even if there are manufacturing variations. An object of the present invention is to provide a magnetic recording/playback device that can provide the following.

In order to achieve this objective, in the present invention,
It is possible to stop in either an even field or an odd field, and the phase of the additional V pulse is changed to an optimum state depending on whether the field is even or odd when the field is stopped.

Embodiments of the present invention will be described below with reference to the drawings. In Fig. 3, 3 is a magnetic tape, 4 is a rotating cylinder, 5 is a head, 6 is a cylinder motor, and 7 is a rotating cylinder.
is a tack head, 8 is a capstan, 9 is a capstan motor, 10 is a head switching signal generator, 1
1 is a still automatic stop section, 12 is a capstan drive section, 13 is an additional V pulse generation section, 14 is a signal addition section, and 15 is an even-odd discrimination section.

The magnetic tape 3 is run in the direction of arrow T by a capstan 8 driven by a capstan motor 9, and a recording pattern is traced by a rotary cylinder 4 rotated by a cylinder motor 6 to reproduce a video signal d. , still automatic stop section 1
1 and the signal adding section 14. On the other hand, the signal from the task head 7 is converted into a head switching signal a through a head switching signal generating section 10, and is supplied to a still automatic stop section 11, an additional V pulse generating section 13, and an even/odd discriminating section 15.

First, a case will be described in which still playback is performed at the position of head locus 1 or 2 shown in FIG. In this case, since the dropout c appears at the A head start position, when the fallout of the dropout c created from the reproduced video signal d and the fall of the head switching signal a coincide, the still automatic stop section 11 sends the dropout to the capstan drive section 12. Give the off command e to the capstan motor to stop it.

The "H" or "L" level of the head switching signal a at the time when the off command e is issued is determined by an even/odd discriminator 15 using a latch means, etc., and an even/odd signal f is obtained, which is then applied to the additional V pulse generator. Send it to 13. That is, in this example, since the time point at which the off command e was issued is in the A head portion, the head switching signal a stops at "L", that is, at an odd field.

In this case, the necessary phase of the additional V pulse b is as shown in _FIG . An additional V pulse b of a predetermined width (approximately the width of the original vertical synchronizing pulse) is output after a time _t1 after the falling edge.

Next, the case where the head is stopped in a field between head trajectories 1 and 2 in FIG. 1 will be explained. The rotating head locus in this case is A as shown in FIG.
The head output decreases, the B head output increases, and a dropout c appears at the start of the B head. Therefore, when the dropout c coincides with the rise of the head switching signal a, the automatic still stop section 11 outputs the off command e to stop the magnetic tape 3, as described above.

In this case, the start of the A head coincides with the bottom edge of the A2 recording track, but the start of the B head differs from the bottom edge of the B1 recording track by α _H , so the required phase of the additional V pulse b is As shown in FIG. 5b, the situation in FIG. 1 must be reversed.

The head switching signal a at the time when the capstan motor off command e is issued is "H" (B
head part), so from the even/odd discriminator 15,
Adding an even number opposite to the above case V pulse creation unit 1
3 will be instructed. Therefore, contrary to the previous case, after the head switching signal a falls, t ₂
The additional V-pulse generator 13 is controlled to output the additional V-pulse b of a predetermined width after 1 hour and t ₁ hour after the signal a rises, thereby creating an additional V-pulse that does not cause vertical fluctuations. There is.

Note that this additional V pulse b is added to the reproduced video signal d by the signal adding section 14, and the output video signal g
becomes.

Whether to stop at an even field or an odd field is determined by the dropout detection level to be stopped. When the detection level is set to a shallow level, it stops at the side where dropout is more likely to occur stably due to manufacturing variations (heads and their mounting accuracy, etc.). This is a normal usage example and can improve stopping accuracy. On the other hand, if the same stopping accuracy as before is acceptable, if the detection level is set deep (in the direction of detecting even a small dropout), it is possible to stop at either even or odd feeds, so the feed speed when moving one frame can be doubled. It becomes possible to improve.

As explained above, according to the present invention, it is possible to stop the magnetic tape in either even or odd fields, so even if there are manufacturing variations, the magnetic tape can always be stopped on the side where dropout appears stably. Good still images with improved stopping accuracy can be obtained. Furthermore, if the dropout detection level is deepened, the feed speed for one frame can be doubled.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the recording track on the magnetic tape and the locus of the rotating head during still playback;
FIG. 2 is a waveform diagram explaining the generation timing of the additional V pulse at that time, FIG. 3 is a block diagram of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, and FIG. 4 shows a stop in a different field from that in FIG. 1. FIG. 5 is a plan view showing the locus of the head when the head is turned on, and a waveform diagram illustrating the generation timing of the additional V pulse at that time. DESCRIPTION OF SYMBOLS 10...Head switching signal generation part, 11...Still automatic stop part, 12...Capstan drive part, 13...
Additional V-pulse creation section, 14... Signal addition section, 15...
Even-odd discriminator.

Claims (1)

[Scope of Claims] 1. In a magnetic recording/playback device having a still playback mechanism, means for stopping tape running by forcing dropouts occurring in each even and odd field forming one frame of a playback video signal into a vertical blanking period. , means for adding a pseudo vertical synchronization signal to the reproduced video signal, and means for determining whether the field is even or odd based on the level difference of the head switching signal at the time when the stop command signal is generated. and, in accordance with the determination result of the even/odd determining means, when tape running is stopped, the phase of the pseudo vertical synchronization signal added to the field where dropout has occurred at the start position of the head is changed to the phase of the pseudo vertical synchronization signal added to the opposite field. 1. A magnetic recording and reproducing apparatus comprising means for creating a pseudo vertical synchronizing signal to be added to the reproduced video signal so as to lag behind the phase of the signal by the number of shifts in H between adjacent tracks.