KR100222996B1 - Reproducing method - Google Patents

Abstract

The present invention relates to a slow playback method of a VCR.

The conventional low speed regeneration method employs a step slow method in which the capstan motor is regenerated while driving and stopping are repeated. Accordingly, in the low speed reproduction, the image interrupted at a predetermined period is reproduced.

According to the present invention, a pair of main heads for constant speed reproduction and adjacent to the main heads are mounted so that noise can be reproduced and continuous video can be reproduced even at 2/3 times, 1/2 times and other low speed playback. A low speed reproduction method of a video cassette recorder comprising at least one pair of additional heads, the method comprising: detecting a periodically repeated period from an envelope waveform of a video signal reproduced by the main head, Generating a pseudo head switching pulse for switching the driving state of the auxiliary head to compare the voltage level of the envelope waveform detected by the main head and the voltage level of the envelope waveform detected by the additional head, according to the comparison result Provides a slow playback method of the video cassette recorder for selectively playing only the part with high voltage level. It was.

Therefore, the present invention can be applied to all video cassette recorders having four or more heads, and the shift range can be arbitrarily set.

Description

Slow playback method of video cassette recorder

The present invention relates to a low speed playback method of a video cassette recorder (hereinafter, abbreviated as 'VCR'). More specifically, the VCR is 2/3 times, 1/2 times and other low speeds with respect to a normal speed. The present invention relates to a slow playback method of a VCR that enables playback of continuous moving pictures at double speed.

The present invention also relates to a low speed reproduction method of a VCR which suppresses generation of noise on a reproduction screen when reproducing a continuous moving image at a low speed.

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, when the signals recorded in the first field and the second field are combined, one frame video signal can be reproduced.

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 to 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.

In the related art, the low speed reproducing method is limited to the method of simply rotating the capstan motor in a step-slow method and continuously and reproducing a still image irregularly for a predetermined time. In this case, because the screen is discontinuously reproduced, the phenomenon that the playback screen is interrupted every predetermined period occurs.

Accordingly, the present invention has been made to solve the above-described problem, and an object of the present invention is to reproduce continuous moving pictures even when performing low speed playback such as 2/3 times and 1/2 times using a 4-head VCR. To provide a low speed playback method of a VCR.

In addition, another object of the present invention is to provide a low-speed playback method of a VCR that can provide excellent image quality with noise suppressed even when performing low-speed playback such as 2/3 times and 1/2 times using a four-head VCR. In providing.

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 schematic internal block diagram of a video cassette recorder for performing a slow playback method according to the present invention;

4 is a schematic diagram showing a head arrangement structure in a head drum mounted on a four head video cassette recorder;

FIG. 5 is a diagram showing a field of a video signal recorded on a recording medium and a head following relationship at low speed reproduction at 2/3 times speed;

Fig. 6 is a waveform diagram of each part in 2/3 times slow playback;

6a shows a head switching pulse,

6b is a control pulse,

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,

7 is a diagram showing a field of a video signal recorded on a recording medium and a head following relationship at low speed reproduction at 1 / 2x speed;

Fig. 8 is a waveform diagram of each part at 1/2 times low speed reproduction;

8a shows a head switching pulse,

8b is a control pulse,

8C shows an envelope waveform of a video signal reproduced by an SP head,

8D is an envelope waveform of a video signal reproduced by an SLP head,

8E shows a pseudo head switching pulse for selecting an SP head and an SLP head;

8F is a synthesized envelope waveform diagram.

* Explanation of symbols for main parts of the drawings

1: Input 2: Drum Servo

3: capstan servo

4,5: SP Head (Standard Play Head)

6,7: SLP Head (Super Long Play Head)

8: microcomputer 9: headdrum

A feature of the present invention for achieving the above objects is a low speed playback method of a video cassette recorder comprising a pair of main heads for constant speed playback and at least one pair or more additional heads mounted adjacent to the main heads. A cycle for regularly repeating is detected from an envelope waveform of a video signal reproduced by the main head, and a pseudo head switching pulse is generated to switch driving states of the main head and the auxiliary head according to the detected period. The voltage level of the envelope waveform detected by the main head is compared with the voltage level of the envelope waveform detected by the additional head, and a reproduction signal is detected from the head where an envelope waveform having a high voltage level is detected according to the comparison result. A low speed reproduction method of a video cassette 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.

First, FIG. 3 shows a schematic internal block diagram of a VCR for performing the low speed reproducing method according to the present invention.

Referring to FIG. 3, an input unit 1 capable of selecting constant speed reproduction and shift reproduction and an input signal selected by the input unit 1 are applied to control the above-described drum servo 2 and capstan servo 3. And an envelope of a video signal reproduced by the first and second SP heads 4 and 5, outputting head switching pulses of the second SP heads 4 and 5 and the second and first SLP heads 6 and 7. It comprises a microcomputer 8 which determines the regularity of the waveform and outputs a pseudo switching pulse.

4 is a schematic diagram showing the head arrangement of the head drum mounted on the four-head VCR applied to the present invention.

As described above, the first SP head 4 and the second SP head 5 are arranged on the outer circumference of the head drum 9 mounted on the four-head VCR at intervals of 180 °. The second SLP head 6 and the first SLP head 7 are arranged and mounted at a distance of 180 ° from the first and second SP heads 4 and 5 at a predetermined distance (approximately 2H) from each other. have.

A case in which the video signal recorded on the recording medium is reproduced at a low speed at 2/3 times using the VCR according to the present invention having the above-described configuration will be described with reference to FIGS. 5 to 6 as follows.

When the video signal recorded on the recording medium is reproduced at low speed at 2/3 times, the capstan motor is rotated at a low speed by 2/3 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 2/3 times the speed during the constant speed reproduction, and according to the head switching signal (see FIG. 6A), 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. 6B, the control signal delayed by 2/3 times than the normal reproduction 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 signal, 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 pulse are as shown in FIGS. 6C to 6F. That is, during low speed playback, since one head follows the track and the adjacent track at the same time, the envelope waveforms of the SP heads 4 and 5 are the corresponding multiples, that is, the least common multiple of 2/3. It is regularly and repeatedly detected by six head switching pulses. 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 6 and 7 mounted adjacent to the first and second SP heads 4 and 5 are used, they are detected by the second and first SLP heads 6 and 7. As shown in FIG. 6D, the envelope waveform of the voltage level opposite to the envelope waveforms by the first and second SP heads 4 and 5 described above is detected.

Therefore, the microcomputer 8 outputs a pseudo head switching pulse signal as shown in Fig. 6E so as to selectively detect envelope waveforms higher than the reference value. Accordingly, as shown in FIG. 6F, the envelope waveforms of the first and second SP heads 4 and 5 and the envelope waveforms of the second and first SLP heads 6 and 7 are synthesized to suppress noise. The moving picture can be played back.

Meanwhile, a case in which the video signal recorded on the recording medium is reproduced at a low speed at 1/2 times will be described with reference to FIGS. 7 to 8.

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. 8A), 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. 8B, 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 pulses are as shown in FIGS. 8C to 8F. That is, during low speed playback, since one head follows the track and the adjacent track at the same time, the envelope waveforms of the SP heads 4 and 5 have a corresponding common speed, that is, a least common multiple of 1/2, as shown in FIG. It is regularly and repeatedly detected by four head switching pulses. 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 6 and 7 mounted adjacent to the first and second SP heads 4 and 5 are used, they are detected by the second and first SLP heads 6 and 7. As shown in FIG. 8D, an envelope waveform having a voltage level opposite to the envelope waveforms of the first and second SP heads 4 and 5 described above is detected.

Therefore, the microcomputer 8 outputs a pseudo head switching pulse signal as shown in Fig. 8E to selectively detect the envelope waveform above the reference value. Accordingly, as shown in FIG. 8F, the envelope waveforms of the first and second SP heads 4 and 5 and the envelope waveforms of the second and first SLP heads 6 and 7 are synthesized to suppress noise. The moving picture can be played back.

Accordingly, the present invention detects a corresponding period having regularity which is repeated by detecting envelope waveforms of the first and second SP heads, and based on the period, the first and second SP heads 4 and 5 and the second SP head are detected. And generating a pseudo head switching signal capable of switching the first SLP heads 6 and 7, thereby producing a portion of the envelope waveforms of the first and second SP heads 4 and 5 having a voltage level below a reference value. And the envelope waveforms of the first SLP heads 6 and 7 to suppress the noise and to detect the moving picture with continuity.

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.

Consequently, according to the slow regeneration method 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 the first and second SPs are referenced based on this period. A pseudo head switching signal capable of switching the head and the second and first SLP heads is generated to generate a reproduction signal having a voltage level below a reference value among the reproduction signals of the first and second SP heads. By substituting with the reproduction signal, there is an advantage that a moving image with a suppressed noise and continuity can be detected.

In addition, even when reproducing at low speed or reproducing a damaged recording medium at an arbitrary speed, the first and second SP heads and the second and first SLP heads are selectively switched to reproduce the reproduction signals and the first and second SP heads. By synthesizing the reproduction signals of the second and first SLP heads, the corresponding fields corresponding to envelope waveforms equal to or greater than the reference value can be reproduced, so that an image signal recorded on the recording medium can be reproduced in an optimal state.

Claims (2)

A low speed playback method 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 generating a pseudo head switching pulse for switching the driving state of the main head and the auxiliary head according to the detected period A video in which the voltage level of the envelope waveform detected by the head is compared with the voltage level of the envelope waveform detected by the additional head, and the playback signal is detected from the head where an envelope waveform having a high voltage level is detected according to the comparison result. Slow playback method of cassette recorder. The method according to claim 1, wherein the periodically repeated cycle, A low speed reproduction method 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 the double speed to be reproduced.

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