JPH0721634A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce a jitter of a reproduced video signal and to obtain a stable picture of the video signal in a cylinder rotation control in the case of obtaining the reproduced video signal by the reproduction of a tape, by detecting the change of frequency against a center frequency of a horizontal synchronizing signal in the reproduced video signal and correcting rotating speed of the cylinder so as to reduce the change of frequency. CONSTITUTION:A horizontal synchronizing signal discriminator 108 to convert the frequency change of the horizontal synchronizing signal in the reproduced video signal into a DC voltage signal and a cylinder speed correcting part 109 to correct the rotating speed of the cylinder corresponded to a discriminating level of horizontal synchronizing signal are arranged further to the basic constitution for the rotation control of the cylinder 101 at the time of tape reproduction. Then, the rotating speed of the cylinder 101 is corrected in accordance with the discriminating level of horizontal synchronizing signal detected during the tape reproduction, and the jitter of the reproduced video signal is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus having a function of reproducing a video signal.

[0002]

2. Description of the Related Art In recent years, as television screens have become larger and wider, there has been developed a mechanism technology for reducing jitter of a reproduced video signal in tape reproduction by a VTR, a learning control technology in cylinder rotation control, and the like. I'm making progress.

A conventional cylinder rotation control technique for tape reproduction will be described below. FIG. 3 is a basic configuration diagram relating to the rotation control of a conventional cylinder.

First, in FIG. 3, 301 is a cylinder,
302 is a head for reproducing a video signal mounted on the cylinder 301, 303 is a cylinder driving device, 304 is a cylinder speed error detection unit, 305 is a cylinder phase error detection unit, 306 is a gain correction unit, and 307 is a reproduction video signal processing circuit. Is.

S3a to S3g are signals, S3a is a cylinder FG signal, S3b is a cylinder PG signal, S3c is a cylinder speed error signal, S3d is a cylinder phase error signal, S3e is a cylinder torque command, and S3f is a reproduction. The head output signal, S3g, is a reproduced video signal.

The rotation control operation of the cylinder at the time of reproducing the tape configured as described above will be described below.

The cylinder speed error detection unit 304 compares the speed of the cylinder FG signal S3a indicating the cylinder speed information generated by the rotation of the cylinder with the target speed, and detects the deviation amount of the current speed from the target speed as a cylinder speed error. Then, a cylinder speed error signal S3c that cancels the deviation amount is generated. Further, in the cylinder phase error detection unit 305, the phase of the cylinder PG signal S3b indicating the phase information of the cylinder is compared with the target phase to detect the deviation amount of the current rotation phase from the target phase as a cylinder phase error, and the deviation is detected. Generate a cylinder phase error signal S3d that cancels the quantity.

Then, S3c and S3d are mixed to generate a cylinder rotation control error, and the next gain correction unit 3
At 06, the required gain is multiplied by the cylinder rotation control error to generate a cylinder torque command S3e, which is transmitted to the cylinder 301 via the cylinder drive unit 303 to perform rotation control.

Further, the head 30 is rotated by the rotation of the cylinder.
The reproduction head output signal S3f picked up by tape 2 from the tape is restored to a reproduction video signal by the reproduction video signal processing circuit 307.

The capstan control is omitted here.

[0011]

However, in the above-mentioned conventional configuration, the rotation speed of the cylinder is controlled without using the video signal information itself of the reproduction tape for controlling the rotation of the cylinder.
In order to drive the cylinder by determining the cylinder torque command so that the rotation phase becomes the target speed and target phase generated by the cylinder speed error detection unit 304 and the cylinder phase error detection unit 305, the video signal is recorded on the tape to be reproduced. The jitter of the reproduced video signal that is restored may increase due to the effects of uneven rotation of the cylinder of the machine that records the data, expansion and contraction of the tape, and so on.

[0012]

In order to solve the above-mentioned problems, the present invention relates to a cylinder rotation control at the time of tape reproduction, in which a frequency change of a horizontal synchronizing signal of a video signal obtained from a reproduction video signal processing device is converted into a DC signal. A cylinder that corrects the rotational speed of the cylinder in order to reduce the frequency change of the horizontal synchronizing signal by using the horizontal synchronizing signal discriminating to convert and the DC voltage signal (horizontal synchronizing signal discriminating level) obtained from the horizontal synchronizing signal discretion. It has a speed correction device.

[0013]

With this configuration, when the reproduced video signal is obtained by reproducing the tape, the rotational speed of the cylinder is constantly corrected so that the frequency change of the horizontal synchronizing signal included in the reproduced video signal becomes small, so that the jitter of the reproduced video signal is corrected. Can be reduced and a stable video signal screen can be obtained.

[0014]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a basic configuration diagram relating to cylinder rotation control in this embodiment, and FIG. 2 is a timing chart of a cylinder speed correction example in this embodiment.

In FIG. 1, 101 is a cylinder and 10
2 is a head for reproducing a video signal mounted on the cylinder 101, 103 is a cylinder drive unit, 104 is a cylinder speed error detection unit, 105 is a cylinder phase error detection unit,
Reference numeral 106 is a gain correction unit, 107 is a reproduced video signal processing circuit, 108 is a horizontal synchronizing signal discretion, and 109 is a cylinder speed correction unit.

S1a to S1i are signals, S1a is a cylinder FG signal, S1b is a cylinder PG signal, S1c is a cylinder speed error signal, S1d is a cylinder phase error signal, S1e is a cylinder torque command, and S1f is a reproduction signal. A head output signal, S1g is a reproduced video signal, S1h is a horizontal sync signal discriminating level, and S1i is a cylinder speed correction signal.

The rotation control of the cylinder configured as described above will be described below focusing on the operations of the newly installed horizontal synchronizing signal disk 108 and cylinder speed correcting unit 109.

First, in the horizontal sync signal discretization of the horizontal sync signal discretization 108, the reproduced video signal S1 restored.
The horizontal synchronizing signal is extracted from g, and the discriminator for detecting the frequency deviation of the extracted horizontal synchronizing signal with respect to the center frequency and converting it into a DC voltage. The deviation is always converted into a DC voltage and output to the cylinder speed correction unit 109 as a horizontal synchronization signal discriminating level S1h.

Next, the cylinder speed correction unit 109 samples the horizontal sync signal discreet level during one rotation of the cylinder based on the cylinder PG signal at m points with respect to the time axis, and the disk at the center frequency of the horizontal sync signal. Horizontal sync signal frequency deviation kl
Calculate as E and store the obtained data in memory. That is, the time change of the frequency deviation with respect to the center frequency of the horizontal synchronizing signal in one rotation of the cylinder is detected. Then, the detection operation is performed n times, and k of each of the m points is
The average value klE 'of 1E is calculated and stored as the average frequency deviation of the horizontal synchronizing signal generated by the current rotation of the cylinder.

Next, in order to bring klE 'close to 0, in the subsequent rotation control of the cylinder, correction data of the target speed for each cylinder FG signal S1a generated during one rotation of the cylinder based on the cylinder PG signal. Is calculated according to the value of klE ′ sampled near the input time of the cylinder FG signal, and the cylinder FG
Each time a signal arrives, it is generated as a cylinder speed correction signal S1i and transmitted to the cylinder speed error detection unit 104. still,
S1i is a DC voltage signal that changes according to the correction amount of the target speed. Also, the cylinder speed error detection unit 10
4, cylinder phase error detection unit 105, gain correction unit 1
06, the processing up to the cylinder drive unit 103 is the same as the conventional technique.

Next, an example of cylinder speed correction by the cylinder speed correction unit 109 will be described with reference to FIG.

First, in this example, the average value klE 'of the horizontal synchronizing signal discriminating level in one rotation of the cylinder is
This indicates that the frequency change of the horizontal synchronizing signal of the reproduced video signal is higher than the center frequency in the vicinity of the center of the track on the tape, and this is the case when the tape is expanded or contracted. Therefore, in order to bring klE ′ close to 0, the target speed of the cylinder FG signal in one rotation of the cylinder is set to the cylinder speed correction value (klV) with respect to the center speed.
By correcting only the rotational speed of the cylinder, the speed on the cylinder is slightly accelerated from the beginning of the track until it passes near the center to increase the speed, and the speed correction value klV decreases from the center to the end, so the actual The rotation speed is also reduced and approaches the center frequency. By performing the speed correction operation twice during one rotation of the cylinder, the frequency deviation of the horizontal synchronizing signal reproduced becomes small, and the jitter of the reproduced video signal can be reduced.

The above is the basic idea of the cylinder speed correction. However, in actuality, there is a time delay in the response of the cylinder to the rotation control of the cylinder, so the response time delay should be taken into consideration in the cylinder control system used. , Kl is the output timing of the cylinder speed correction value klV
Jitter can be reduced by transmitting the T-shifted cylinder speed correction value klV 'to the cylinder speed error detection unit 104 as a cylinder speed correction signal S1i and correcting the target speed by klV' with respect to the center speed.

[0025]

As described above, according to the present invention, in the cylinder rotation control during tape reproduction, the frequency change with respect to the center frequency of the horizontal synchronizing signal in the reproduced video signal is always detected to reduce the frequency change. By correcting the rotation speed of the cylinder, it is possible to reduce the jitter of the reproduced video signal and obtain a stable video signal screen.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram regarding rotation control of a cylinder in an embodiment of the present invention.

FIG. 2 is a timing chart of a cylinder speed correction example according to an embodiment of the present invention.

FIG. 3 is a basic configuration diagram of conventional cylinder rotation control.

[Explanation of symbols]

 101 Cylinder 102 Head 103 Cylinder Drive Unit 104 Cylinder Speed Error Detection Unit 105 Cylinder Phase Error Detection Unit 106 Gain Correction Unit 107 Playback Video Signal Processing Circuit 108 Horizontal Sync Signal Discrete 109 Cylinder Speed Correction Unit

Claims (1)

[Claims] 1. A cylinder having a head for reproducing a video signal, a cylinder control means for controlling the rotation of the cylinder, a capstan for running a tape, and a capstan control for controlling the capstan. A magnetic recording / reproducing apparatus having means for reproducing a signal reproduced from the head into a video signal by rotation of the cylinder, the horizontal direction of the video signal obtained from the reproducing video signal processing circuit. In order to reduce the frequency change of the horizontal synchronizing signal by using the horizontal synchronizing signal discriminant for detecting the synchronizing signal and converting the frequency change into the direct current signal, and the horizontal synchronizing signal discriminating level obtained from the horizontal synchronizing signal discriminant. A cylinder speed correction means for correcting the rotation speed of the cylinder,
A magnetic recording / reproducing apparatus characterized in that the rotational speed of the cylinder is constantly corrected so that the frequency change of the horizontal synchronizing signal in the reproduced video signal becomes small.