KR100208007B1 - How to adjust tracking automatically during slow playback of video cassette recorder - Google Patents

Abstract

The present invention relates to a method for automatically adjusting tracking at low speed playback of a VCR.

The conventional tracking adjustment method is configured to detect and adjust the screen state optimally while finely shifting the position of the control signal within one period of the regularly generated head switching pulse. However, since the envelope waveform is irregularly detected during low speed reproduction, such tracking adjustment cannot be performed normally.

Accordingly, the present invention provides a pair of main heads for constant speed reproduction, and at least adjacent to the main heads for automatically performing tracking adjustments at 2/3 times, 1/2 times, and other low speed reproductions. A tracking automatic adjustment method for low speed playback of a video cassette recorder including one or more pairs of additional heads, the method comprising: detecting a periodically repeated period from an envelope waveform of a video signal reproduced by the main head, and detecting the repeated period according to the detected period. A pseudo head switching pulse is generated to switch driving states of the main head and the auxiliary head, and the control signal is moved within a section having a high level of the envelope waveform level among the positive and negative components of the pseudo head switching signal. Search for the point where the amount of change is maximum, and within the head switching pulse section corresponding to the We have proposed an automatic tracking method for low speed playback of a video cassette recorder that automatically adjusts tracking.

Description

How to adjust tracking automatically during slow playback of video cassette recorder

The present invention relates to a method of automatically adjusting tracking during low speed playback of a video cassette recorder (hereinafter, abbreviated as 'VCR'). More specifically, the VCR is 2/3 times the normal speed, The present invention relates to a tracking automatic adjustment method for low speed playback of a VCR that enables playback of a video signal recorded in a corresponding field in an optimum state even when playing at 1/2 speed and other low speeds.

In general, a VCR is a device for recording and reproducing video and audio signals recorded on a recording medium (video cassette tape). The VCR has a function of reproducing a video signal of a recording medium at a constant speed, a low speed picture, a still picture, and a high speed picture.

On the other hand, the servo system in the VCR is roughly classified into a drum servo which constantly controls the rotation of the head, and a capstan servo that controls the track and keeps the traveling speed of the recording medium constant. . In particular, the capstan servo controls the phase and speed of the capstan motor so that the head allocated to each channel can accurately reproduce the video signal of the corresponding channel, and keeps the traveling speed of the recording medium constant during playback or recording. At this time, the capstan speed control controls the rotation of the capstan motor by obtaining the capstan speed error voltage from the capstan frequency signal CFG corresponding to the traveling speed of the recording medium. In the case of special playback such as low speed playback, pause, division operation, etc., a step slow control signal output from the microcomputer is applied to the capstan motor.

In capstan phase control, the capstan phase error voltage is obtained by comparing the frequency of the control signal with the reference frequency at the time of reproduction, and adding the voltage to the capstan speed control voltage to control the capstan motor.

In the case of a typical two-head VCR, the first head (channel 1) and the second head (channel 2) are arranged at intervals of 180 degrees on the outer circumference of the head drum. In addition, a conventional recording medium employs a method of recording an image signal inclined on a recording medium in units of fields in order to improve recording density. Here, each field is recorded by alternately recording a first field corresponding to channel 1 and a second field corresponding to channel 2, and a signal recorded in the first field and a signal recorded in the second field are used to prevent disturbance of mutual signals. In order to prevent this, it is recorded by Azimuth recording method.

At this time, when the recording medium is driven at a predetermined speed by the capstan motor and the head drum is rotated at the predetermined speed by the spindle motor, the first head reproduces the video signal recorded in the first field (channel 1) according to the head switching signal. And the second head reproduces the video signal recorded in the second field (channel 2). Here, by combining the signals recorded in the first field and the second field, it is possible to reproduce a video signal of one frame.

On the other hand, in the case of a four-head VCR, the first SP (Standard Play) head (also referred to as the 'main head') and the second SP head are arranged at the outer circumference of the head drum at 180 ° intervals. A second super long play (SLP) head (also referred to as an 'EP head' or 'additional head') and the first SLP head may be spaced 180 degrees apart from each other at a predetermined distance from the first and second SP heads. It is arranged and mounted. Here, the first and second SLP heads are additional heads additionally mounted for shift reproduction, and are not used for constant speed reproduction but only for shift reproduction.

1 and 2 show an area in which the head tracks the video signal recorded on the recording medium during the constant speed reproduction of the VCR, the head switching pulse and the control signal waveform.

As shown, when the VCR is continuously played back, the video signal (see Fig. 1) recorded in each of the fields CH1 and CH2 has a corresponding channel according to the head switching pulse shown in Fig. 2A and the control signal shown in Fig. 2B. Since each of the heads SP1 and SP2 is reproduced, a stable envelope waveform having a constant level (see FIG. 2C) is always output. At this time, the control signal is detected at a time point elapsed by a predetermined time T from the positive edge component of the head switching pulse, which is related to the tracking position of the head capable of optimally reproducing the video signal recorded on the track.

Therefore, in the related art, the control signal detected within the range of one cycle of the head switching pulse is finely moved left and right so that the head follows the field at the optimum position of the corresponding field, thereby reproducing the optimum video signal. That is, during constant speed reproduction, since the envelope waveforms of the first and second SP heads maintain a constant level, the entire control signal is automatically adjusted as the fine control of one control signal.

On the other hand, when the VCR is played back at low speed, the first and second SP heads follow a state in which a track adjacent to the corresponding track is shared, so that an envelope waveform having an irregular level is output. For example, in the case of low speed reproduction at 2/3 times, since the first and second SP heads follow the track adjacent to the track, the first and second SP heads switched by the head switching pulses are controlled pulses. When the video signal recorded on the recording medium is reproduced, irregular envelope waveforms are detected. At this time, the envelope waveform is regularly and repeatedly outputted with the head switching pulse number corresponding to the least common multiple of the set double speed. In addition, in the case of low speed reproduction at 2/3 times speed, two control signals are detected while the head switching pulse passes three cycles. Since the slow playback method of the VCR is disclosed in detail in the patent application No. 97-03682 filed by the present applicant (name of the invention: the slow playback method of the VCR) (97.02.06), an additional description thereof is omitted. do.

However, in the case described above, since the envelope waveform is irregularly generated during low speed reproduction, when a control pulse is generated at an arbitrary position, a response to adjusting the control signal hardly occurs. Therefore, there was a problem that tracking adjustment is impossible.

In addition, when adjusting the tracking within the head switching pulse section of one cycle during low speed playback, the tracking adjustment response for 1/2 cycle and the tracking adjustment response for the other 1/2 cycle occur differently, so that accurate tracking adjustment There was a problem that this was impossible.

Accordingly, an object of the present invention is to solve the above-described problem, and an object of the present invention is to control a generation position of a control signal so that an optimum moving image can be reproduced even when low-speed playback is performed using a VCR. To provide automatic tracking of city tracking.

In addition, another object of the present invention is to provide a tracking automatic adjustment method for low-speed playback of the VCR to control the adjustment position of the control signal in order to reproduce the optimum moving picture in performing low-speed playback using the VCR.

1 is a diagram showing a field of a video signal recorded on a recording medium and a head following relationship in constant speed playback;

2A to 2B are waveform diagrams of a head switching pulse and a control signal during constant speed playback shown in FIG. 1;

3 is a diagram showing a field of a video signal recorded on a recording medium and a head tracking relationship at low speed reproduction at 2/3 times according to the present invention;

Fig. 4 is a waveform diagram of each part during 2/3 times slow playback.

4a shows a head switching pulse,

4b is a control signal,

4C is an envelope waveform of a video signal reproduced by an SP head,

4D is an envelope waveform of a video signal reproduced by an SLP head,

4E shows a pseudo head switching pulse for selecting an SP head and an SLP head,

4F is a synthesized envelope waveform diagram,

FIG. 5 is a diagram showing a field of a video signal recorded on a recording medium and a head tracking relationship at low speed reproduction at 1/2 times according to the present invention;

Fig. 6 is a waveform diagram of each part at 1/2 times low speed reproduction;

6a shows a head switching pulse,

6b is a control signal,

6C shows an envelope waveform of a video signal reproduced by an SP head,

6d is an envelope waveform of a video signal reproduced by an SLP head,

6E shows a pseudo head switching pulse for selecting an SP head and an SLP head,

6F is a synthesized envelope waveform diagram.

A feature of the present invention for achieving the above objects is a tracking automatic during low speed playback of a video cassette recorder comprising a pair of main heads for constant speed playback and at least one pair of additional heads mounted adjacent to the main heads. An adjustment method comprising: a pseudo head switching pulse for detecting a periodically repeated period from an envelope waveform of a video signal reproduced by the main head, and switching driving states of the main head and the auxiliary head according to the detected period. Generates a search signal to move the control signal within a section having a high level of the envelope waveform level among the positive and negative components of the pseudo head switching signal to search for a point where the variation amount of the envelope waveform is maximum, and corresponds to the found point. Video that automatically adjusts tracking within headswitching pulse intervals In the automatic tracking adjustment method when low-speed reproduction of the set of the recorder.

In the above-described feature of the present invention, it is preferable that the regularly repeated period is set to the number of head switching pulses corresponding to the least common multiple of the double speed to be reproduced.

Best Mode for Carrying Out the Invention A preferred embodiment of the slow playback method of a VCR according to the present invention will be described in detail with reference to the accompanying drawings.

3 to 6 are diagrams for explaining a tracking automatic adjustment method at low speed playback according to the present invention.

First, a tracking automatic adjustment method for low speed reproduction at 2/3 times speed will be described with reference to FIGS. 3 and 4.

When the video signal recorded on the recording medium is reproduced at a low speed at 2/3 times, the capstan motor is rotated at a low speed by 2/3 times as compared with the rotation speed at the constant speed reproduction, and the drum motor is rotated at the same speed as at the constant speed reproduction. Therefore, the recording medium is conveyed at 2/3 times the speed during the constant speed reproduction, and according to the head switching signal (see FIG. 4A), the first and second SP heads 4 and 5 are separated from the recording medium as shown in FIG. The recording signal is reproduced by following the corresponding fields alternately. At this time, as shown in FIG. 4B, the control signal delayed by 2/3 times as compared with normal playback is simultaneously reproduced, and the capstan motor rotates in synchronization with the control signal to drive the recording medium. The control signal is detected at a time point elapsed by a predetermined time T from the positive edge component of the head switching pulse, which is related to the tracking position of the head capable of optimally reproducing the video signal recorded on the track.

The envelope waveform and the pseudo head switching signal of the video signal reproduced by the head switching pulses are as shown in FIGS. 4C to 4F. In other words, at the time of low speed playback, since one head follows the track and the adjacent track at the same time, the envelope waveform of the SP head is six headswitching pulses, which is the minimum common multiple of the corresponding double speed, that is, as shown in FIG. 4C. It has regularity at intervals and is repeated and detected. At this time, an envelope waveform equal to or greater than a reference value (referred to as a reproduction screen with almost no noise) is detected in the four head switching pulse periods. As a reproduction screen containing noise, a reproduction screen of a degree that is difficult to see is detected).

However, when the second and first SLP heads mounted adjacent to the first and second SP heads are used, the envelope waveforms detected by the second and first SLP heads are the same as those shown in FIG. 4D. An envelope waveform of a voltage level opposite to the envelope waveform by the second SP head is detected.

Thus, the microcomputer (not shown) outputs a pseudo head switching pulse signal as shown in FIG. 4E to selectively detect envelope waveforms above the reference value. Accordingly, as shown in FIG. 4F, the composite envelope waveform obtained by combining the envelope waveforms of the first and second SP heads and the envelope waveforms of the second and first SLP heads is detected.

Then, the amount of change in the envelope waveform is detected while the control pulse is moved left and right within the positive section of the pseudo head switching pulse. At this time, the tracking adjustment is performed within a half period (1/2 period) of the head switching pulse corresponding to the corresponding point by finding the point where the variation amount of the envelope waveform is the maximum value. Here, in the case of performing low speed reproduction at 2/3 times, six head switching pulses (0 to 5) are regularly repeated. According to the experimental value, the third head switching pulse is indicated as '2' in FIG. 4A. It can be seen that the envelope waveform changes the most within the interval. Therefore, by finely adjusting the position of the control pulse within the third head switching pulse section, an optimum reproduction screen can be obtained.

Next, the tracking automatic adjustment method for the low speed reproduction at 1/2 times will be described with reference to FIGS. 5 and 6.

When the video signal recorded on the recording medium is reproduced at a low speed at 1/2 times, the capstan motor is rotated at a low speed by 1/2 times the rotation speed at the constant speed reproduction, and the drum motor is rotated at the same speed as at the constant speed reproduction. Therefore, the recording medium is conveyed at 1/2 times the speed of the constant speed reproduction, and according to the head switching signal (see FIG. 6A), the first and second SP heads alternately corresponding fields of the recording medium as shown in FIG. It follows to reproduce the recording signal. At this time, as shown in FIG. 6B, the control signal delayed 1/2 times as compared with the constant speed reproduction is simultaneously reproduced, and the capstan motor rotates in synchronization with the control signal to drive the recording medium.

The envelope waveform and the pseudo head switching signal of the video signal reproduced by the head switching pulse are as shown in FIGS. 6C to 6F. In other words, at the time of low speed playback, since one head follows the track and the adjacent track at the same time, the envelope waveform of the SP head is four headswitching pulses, which is the minimum common multiple of the corresponding double speed, that is, as shown in FIG. 6C. It has regularity at intervals and is repeated and detected. At this time, an envelope waveform equal to or greater than the reference value is detected in the two head switching pulse periods, while an envelope waveform smaller than or equal to the reference value is detected in the remaining two head switching pulse periods.

However, when the second and first SLP heads mounted adjacent to the first and second SP heads are used, the envelope waveforms detected by the second and first SLP heads are the same as those shown in FIG. 6D. An envelope waveform of a voltage level opposite to the envelope waveform by the second SP head is detected.

Therefore, the microcomputer (not shown) outputs a pseudo head switching pulse signal as shown in Fig. 6E to selectively detect envelope waveforms above the reference value. Accordingly, as shown in FIG. 6F, the composite envelope waveform obtained by combining the envelope waveforms of the first and second SP heads and the envelope waveforms of the second and first SLP heads is detected.

Then, the amount of change in the envelope waveform is detected while the control pulse is moved left and right within the positive section of the pseudo head switching pulse. At this time, the tracking adjustment is performed within a half period (1/2 period) of the head switching pulse corresponding to the corresponding point by finding the point where the variation amount of the envelope waveform is the maximum value. In this case, when the low speed reproduction is performed at 1/2 times, four head switching pulses (0 to 3) are regularly repeated. According to the experimental value, the first head switching pulse is indicated as '0' in FIG. 6A. It can be seen that the envelope waveform changes the most within the interval. Therefore, by finely adjusting the position of the control pulse within the first head switching pulse section, an optimum reproduction screen can be obtained.

As a result, the present invention detects the corresponding waveform having regularity which is repeated by detecting the envelope waveforms of the first and second SP heads, and based on this period, the first and second SP heads and the second and first SLPs are detected. After generating the pseudo head switching signal capable of switching the head, the control signal is moved within the positive component of the pseudo head switching signal to search for the point where the variation of the envelope waveform is maximum, and the head switching pulse corresponding to the detected point. By automatically adjusting the tracking in the section, it is possible to watch the optimum playback screen.

On the other hand, the low speed reproducing method according to the present invention is not limited to the aforementioned 2/3 times and 1/2 times speeds, and is applied to all low speed reproductions below 1x speed (constant speed regeneration) that can detect regularity according to a certain period. can do.

As a result, according to the tracking automatic adjustment method for low-speed playback of the VCR according to the present invention, the envelope waveforms of the first and second SP heads are detected to detect a corresponding period having a regularity which is repeated, and based on the period, And generating a pseudo head switching signal capable of switching the second SP head and the second and first SLP heads, and then moving the control signal within the positive component of the pseudo head switching signal to determine a point where the change amount of the envelope waveform is maximum. By searching and automatically adjusting the tracking in the head switching pulse section corresponding to the searched point, the optimum playback screen can be viewed.

Claims (2)

A method for automatically adjusting tracking during low speed playback of a video cassette recorder comprising a pair of main heads for constant speed playback and at least one pair of additional heads mounted adjacent to the main heads: Detecting a periodically repeated period from the envelope waveform of the video signal reproduced by the main head, and generates a pseudo head switching pulse for switching the driving state of the main head and the auxiliary head in accordance with the detected period In the positive and negative components of the head switching signal, the control signal is moved within a section having the highest level of the envelope waveform to search for a point where the variation of the envelope waveform is maximum, and within the head switching pulse section corresponding to the found point. A method for automatically adjusting tracking during slow playback of a video cassette recorder that automatically adjusts tracking. The method according to claim 1, wherein the periodically repeated cycle, A method for automatically adjusting tracking during low speed playback of a video cassette recorder, characterized in that it is set to the number of head switching pulses corresponding to the least common multiple of double speed to be played.

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