JPS5871777A - Magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To detect assuredly the position of noise and to perform good reroduction with variable speed, by detecting the correlation between the signal in an optional horizontal scan section of a reproduced video signal and the signal in a nearby horizontal scan period and then detecting the position of noise. CONSTITUTION:A switch 4 is controlled by the signal of a head switch signal producing circuit 6, and the reproduced video signals are obtained through heads Ha and Hb. These video signals are delivered to an output terminal 9 through an amplifier 7 and a demodulating circuit 8. The ordinary video signal is not virtually delivered from a subtractor circuit 13 since the correlation is extremely strong between the signals of adjacent horizontal scan period. The noises have no correlation at an area where the noises are reproduced, and therefore a signal of a high level is extracted from the circuit 13 and then supplied to an LPF 14. As a result, the signal due to a single-shot noise, etc. is deleted, and the signal corresponding to the noise position is delivered through a terminal 15.

Description

[Detailed Description of the Invention] A so-called helical scan type video tape recorder (
(VTR), the tape is moved at a different speed than when recording, allowing it to move at a stationary, slow, or quick speed.

There is a device that allows variable speed reproduction such as reverse rotation.

In this case, the inclinations of the first and second recording marks on the tape and the scanning locus of the head do not match.

Noise is reproduced in a portion of the head that is off the recording track, and the noise in that portion is degraded.

Figure 1 shows a recording pattern of a tape in which the recording density is increased by utilizing the so-called azimuth loss of the magnetic head. For example, if the position of the broken line a on this pattern is scanned with a head position of the azimuth equal to the azimuth of the track Ta.

The head Ha substantially coincides with the track Ta at any position from the scanning start point 1 (!11 to the end point Hsx).

A desired reproduction signal can always be obtained.

On the other hand, when the head & is scanned over tracks Tb having different recording azimuths as shown by the chain line (1), for example, the signal of the track Tb is not reproduced at the central position (LlB), but noise is reproduced.

Image quality deteriorates in the center of the screen.

Therefore, it has been proposed to detect the position of this noise and perform capstan servo or the like so that the position of this noise is within the vertical blanking period.

In this case, the conventional method for detecting the noise position is to detect the level of the reproduced signal from the head and detect the point where this level becomes small.

However, in some VTRs, the width of the head is larger than the width of the track, as shown in Figure 1.

The signal of the adjacent track Ta is also reproduced at the central position Has, and the level of the reproduced signal from the head does not drop much. For this reason, it is not possible to distinguish between a drop in the level of the video signal itself, and this type of VTR [playback
It was not possible to detect the door/eye position due to the signal level.

Alternatively, in a recording pattern in which the recording position of the horizontal synchronization signal shifts sequentially from track to track, the noise position can be detected by detecting the position shift of the horizontal synchronization signal. If the recording positions are lined up, the noise position cannot be detected using this method.

In view of these points, the present invention is designed to enable noise position detection in this type of VTR.

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

In FIG. 2, the magnetic data 1 (1) is the head Ha,
It is wound around a rotating head drum (2) containing Hb and transported by a capstan (3). Then, the (jI number reproduced by the head) ia and Hb is supplied to the switch (4), and the signal from the pulse generator (5) provided in series with the drum +27K II is sent to the head switching signal forming circuit ( 6), the switch (4) is controlled by this switching signal, and a reproduced video signal is taken out.This reproduced video signal is outputted to an output terminal (9K) through an amplifier (7) and a demodulation circuit (8). Ru.

Furthermore, the signal from the demodulation circuit (8) is sent to the modulation circuit αI.

The signal is supplied to the delay circuit αD for one horizontal period and the demodulation circuit Q21, and is delayed by one horizontal period. This delayed signal and demodulation circuit (8
) is supplied to the subtraction circuit αJ.

Here, in a normal video signal, since the correlation between signals in adjacent horizontal scanning periods is extremely strong, almost no output from the subtraction circuit (13) can be obtained.On the other hand, in the part where noise is reproduced, Since there is no correlation between
11! A high level signal is taken out from the calculation circuit α3.

Then, by supplying this signal to a low-pass filter circle, signals due to premature noise and the like are removed, and a signal corresponding to the noise position is outputted to the terminal (15+).

Furthermore, this figure shows a case where the present invention is applied to still image reproduction. In this case, the signal from the low-pass filter Q41 is supplied to the coincidence detection circuit (161), and the signal from the formation circuit (6) is fully supplied to the monostable multi-vibrator aη, resulting in a vertical blanking period after switching the switch. A signal for a predetermined period corresponding to 1 is formed, and this signal is supplied to the coincidence detection circuit (161).

The signal from the coincidence detection circuit αG is then supplied to the capstan motor a&, and the motor side is controlled so that the above-mentioned signals coincide.

In this way, the noise position is detected.According to the present invention, since the detection is performed based on the horizontal correlation of the reproduced video signal, the noise position is detected directly below the signal level at the noise position,
Even if there is no phase shift of the horizontal synchronization signal, the noise position can actually be detected.

In addition, in the present invention, the reduction in signal level and the horizontal synchronization g
Even if there is a phase difference t of r, it is possible for a colleague to detect the noise position.

Furthermore, as mentioned above, it is still! II playback in line 5.

By controlling the capstan motor so that the vertical blanking period matches the detected noise position,
Noise portions can be reliably removed from the playback screen.

Further, the noise position detection signal according to the present invention can be used to perform auto-tracking during Te, Slow, Quick, and Reverse playback.

That is, in conventional variable speed reproduction of this type.

Automatic tracking is performed by detecting the position of the video signal track using the control track/carano playback control signal. However, in that case, the installation of the control head may be due to errors.

There were cases in which the control signal and the video signal track position did not completely correspond, and there was no compatibility between VTRs.

In that case, by using the noise position detection signal according to the present invention instead of the control signal.

Since this noise position detection signal is detected from the actual track No. 100, accurate auto-tracking can be performed separately and there are no compatibility problems.

Specifically, when performing slow playback, the noise position detection signal and the switch switching signal are compared in phase.

The comparison output is supplied to the tracking servo circuit and servo is performed so that these match.

When performing quick and reverse playback, the noise position detection signal and switch switching signal are supplied to the phase servo circuit of the capstan motor, and this output signal is added to the speed servo signal and supplied to the capstan motor.

5. According to the present invention, the noise position can be reliably detected using a simple AG, and good variable speed reproduction can be performed using this detection g71.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the video tape recorder, Figure 2 is a diagram for explaining the video tape recorder.
The figure is a #l diagram of an example of the present invention. (1) Tape, (2) & (2) Rotating head drum, (
8■ Engineering circuit, αIJ is the delay loop, σ34 is the delay loop, and U gradient is the Rono cross filter.

Claims (1)

[Claims] When performing variable speed reproduction of the Eirin signal, the position of the noise can be detected by detecting the correlation between the signal of an arbitrary horizontal scanning section of the reproduced Eirin signal and the signal of the horizontal scanning section in the vicinity of this horizontal scanning section. A magnetic recording and reproducing device designed to do this.