KR0176533B1 - Tracking control apparatus and method - Google Patents

Abstract

The present invention discloses a tracking control method and apparatus for low speed playback of a video tape recorder. The method of the present invention comprises the steps of selecting the SP head and the EP head according to the head selection signal output from the capstan servo; A second step of generating an envelope comparison signal by comparing the envelope detected in the SP head selected in the first step with the envelope detected in the EP head; Extracting a waveform of a common part of the playhead switching signal and the envelope comparison signal generated in the second step; A fourth step of masking the waveform extracted in step 3 based on the rising and falling edges of the head selection signal for a predetermined time; A fifth step of determining whether the envelope comparison signal generated in the second step and the playhead selection signal are the same after the masking time in the fourth step has passed; And terminating the tracking program if the envelope comparison signal and the playhead selection signal are the same in the fourth step, and performing tracking up / down control until the waveform of the playhead switching signal and the envelope comparison signal are the same. Include.

Therefore, the present invention eliminates the need for a separate external input key operation by adjusting the capstan control signal so that the playhead selection signal and the signal output from the envelope comparator match.

Description

Tracking control method and device for low speed playback of video tape recorder

Fig. 1A is a block diagram of a tracking control device at low speed playback of a video tape recorder according to the present invention.

FIG. 1B is a detailed block diagram of FIG. 1A. FIG.

2 is a plan view showing four head drums of a video tape recorder used in the present invention.

3A to 3E are timing charts showing waveforms of respective components shown in FIG. 1B.

4 is a flowchart for explaining an automatic tracking control method for low speed playback of a video tape recorder according to the present invention.

The present invention relates to a tracking control method and apparatus for low speed playback of a video tape recorder, and more particularly, to a tracking control method for low speed playback of a video tape recorder controlling a capstan motor such that the position of the drum head and the video tape of the video tape recorder is exactly matched. And to an apparatus.

Video recording and reproducing apparatuses, such as a video tape recorder or a video camera, do not have a good picture state such as a bit generated on the screen if tracking is not corrected. Therefore, tracking control is essential to obtain a good picture.

Tracking control refers to controlling the head to accurately scan a prescribed track during playback to obtain the maximum envelope output.

Tracking control uses a separate control signal. In the VHS type video tape recorder, tracking is performed using the control signal formed on the control track of the tape by the fixed head.In the case of 8mm type, the track is automatically tracked to each track (ATF). A pilot signal with four different frequencies, called a signal, is recorded on a tape, and during playback, this signal is used to identify the tracking error, that is, the tracking error. Control in the decreasing direction.

Minimization of the detected tracking error is realized by controlling the rotational speed of the capstan motor. That is, the object of tracking control is the rotational speed of the capstan motor.

The basic principle of tracking control is to slow down the capstan motor when the head is ahead of the prescribed track and slow down the tape, and to speed up the capstan motor when the head is behind the prescribed track. The head may be controlled to accurately scan the prescribed track. The basic principle of such tracking control is still valid in the present invention as well as the conventional method.

Tracking at low speed means that when the videotape is played at low speed, the position of the tracks of the playhead and the videotape passing through the playhead does not exactly match, that is, when noise occurs due to the phase difference between the tracks of the videotape and the playhead. This is to control the capstan motor so that the video tape stops at the noise-free position.

In general, when a video tape recorder is played at a low speed, noise may appear on the screen because the video tape is played without the exact position of the drum head and the video tape of the video tape recorder. Manual tracking by user key input was done using tracking up / down keys to adjust head and videotape positions.

The conventional manual tracking method has a inconvenience in that the user needs to directly manipulate the tracking up / down keys while looking for a screen without noise. In addition, when the tracking is adjusted using the tracking up / down keys, it is difficult to set the timing of the control signal due to component characteristics and component deviation of the key input means.

Accordingly, an object of the present invention is to track during slow playback of a videotape recorder that performs tracking according to the signal by adjusting the capstan control signal so that the output of the envelope comparator and the playhead selection signal are the same in order to solve the above-mentioned problems. It is to provide a method and apparatus.

In order to achieve the above object, a tracking control method of a video tape recorder according to the present invention at low speed playback includes: a first step of recognizing a capstan motor driving start point of a capstan control signal according to a control signal output from a microcomputer; A second step of selecting the SP head and the EP head according to the head selection signal output from the capstan servo; A third step of generating a digital signal by comparing a signal reproduced from the SP head selected in the second step with a signal reproduced from the EP head selected in the second step; A fourth step of determining whether the digital signal generated in the third step and the playhead selection signal output from the capstan servo are the same; And when the digital signal generated in the third step and the playhead selection signal are different, the tracking is adjusted by controlling the capstan motor driving end point T _B of the capstan control signal, and the digital signal and the playhead selection signal generated in the third step are If the same, characterized in that it comprises a fifth step of terminating the tracking.

A tracking apparatus during low speed playback of a video tape recorder according to the present invention comprises: SP / EP head selecting means for selecting the SP head and the EP head from the playback head according to the head selection signal; Envelope comparing means for comparing the envelope of the SP head selected from the SP / EP head selecting means with the envelope of the EP head and outputting the digital signal; A microcomputer inputting a digital signal output from the envelope comparing means and a playhead selection signal output from the capstan servo, determining whether these signals are the same signal, and generating a capstan control signal according to the determined result; And a capstan servo which outputs a head selection signal and a reproduction head selection signal and inputs a capstan control signal to drive the capstan motor.

In the tracking apparatus during low speed reproduction of a video tape recorder, it is preferable to further include a low pass filter for low-pass filtering the output of the envelope comparing means, and a comparator for reducing the rise time and fall time of the signal output from the low pass filter.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

1A is a block diagram of a tracking device for low speed playback of a video tape recorder according to the present invention, wherein the SP / EP head selection unit 2 selects the SP head and the EP head from the playback head under the control of the capstan servo 8, respectively. ) And the digital signal output from the envelope comparator 4 and the envelope comparator 4 for comparing the envelope of the SP head selected from the SP / EP head selector 2 with the envelope of the EP head and outputting the digital signal. And a microcomputer 6 generating a capstan control signal after inputting a playhead selection signal output from the capstan servo 8 and determining whether they are the same signals, and a capstan servo 8 for driving a capstan motor by inputting a capstan control signal. ).

FIG. 1B is a detailed block diagram of FIG. 1A, which controls a capstan motor (not shown) in accordance with the capstan control signal 108, and includes a head selection signal 101 and a playhead selection signal 102 for controlling the capstan motor. A capstan servo 8 for generating various control signals; An SP head selector SW1 for selecting an SP head in accordance with the head selection signal 101; An EP head selector SW2 for selecting an EP head in accordance with the head selection signal 101; A playhead selector SW3 for selecting the output of the SP head selector SW1 and the output of the EP head selector SW2 in accordance with the playhead selection signal 102; Inputting the envelope of the SP head selected by the SP head selector SW1 and the envelope of the EP head selected by the EP head selector SW2 to the inverting terminal (-) and the non-inverting terminal (+), respectively, and outputting the digital signal 103. Envelope comparator 44; A low pass filter 46 for low pass filtering the digital signal output from the envelope comparator 44; A comparator 48 for reducing the rise time and fall time by comparing the signal output from the low pass filter 46 with a reference level; And a microcomputer 6 which inputs the output of the playhead selection signal 102 and the output of the comparator 48 to determine whether these signals are the same signal, and generates the capstan control signal 108 according to the result of the determination.

Here, the low pass filter 46 and the comparator 48 are used to remove noise at the output 103 of the envelope comparator 44 and to make the digital signal accurate.

2 is a plan view showing four head drums of a video tape recorder used in the present invention, in which a normal playback head (hereinafter referred to as an SP head; R ', L') and a high density playback head (hereinafter referred to as an EP head); There are two R and L).

3A to 3E are timing charts showing the waveforms of the respective components shown in FIG. 1B, and FIG. 4 is a flowchart for explaining a tracking method during low speed playback of a video tape recorder according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to FIGS. 1B to 4.

As a prescribed specification which is set in advance when designing the tracking control device, if the position of the playhead and the video tape are exactly matched, the envelope of the head selector selected by the playhead selection signal 102 is larger than the envelope of the unselected head selector.

That is, in the low speed regeneration mode, the head selection signal 101 and the reproduction head selection signal 102 are controlled by the microcomputer 6 and the capstan servo 8 so as to select the reproduction head according to the prescribed design specification.

When the head select signal 101 is' low ', the R' head and the L head are selected from the SP head selector SW1 and the EP head selector SW2, respectively. When the head select signal 101 is' high ', SP is selected. The L 'head and the R head are selected from the head selector SW1 and the EP head selector SW2, respectively.

Further, when the playhead select signal 102 is 'low', the SP head selector SW1 is selected from the playhead select signal SW3 and the playhead select signal 102 is 'high'. ) Is selected and one playhead is selected from the four playheads.

The envelope comparator 44 inputs the signal output from the SP / EP head selector 2, and if the envelope of the signal output from the SP head selector SW1 is larger than the envelope of the signal output from the EP head selector SW2, Low 'and outputs a' high 'if the envelope of the signal output from the EP head selector SW2 is greater than the envelope of the signal output from the SP head selector SW1.

Therefore, if the positions of the playhead and the video tape are correctly matched, the output signal 103 and the playhead switching signal 102 of the envelope comparator 44 as shown in Figs. 3D and 3E according to the design specification of the tracking control device are shown. ) Exactly matches

The digital signal 103 output from the envelope comparator 44 generates unstable noise at the edge portion, and the digital signal 103 is filtered by the low pass filter 46 to increase the rise time and the fall time in the comparator 48. It is reduced and input to the logic comparator 62 of the microcomputer 6.

The logic comparator 62 of the microcomputer 6 inputs the playhead selection signal 102 and the output signal 103 of the comparator 48 to perform a logical comparison, and the masking unit 64 is the head selection signal 101. The input is masked for a predetermined time on the basis of the edge of the track. The tracking determination unit 66 determines whether the output signal of the playhead selection signal 102 and the comparator 48 are the same after a predetermined time. The result is output to the control signal generator 68.

The control signal generator 68 inputs the control signal 109 outputted from the capstan servo 8 and the outputs of the head selection signal 101 and the tracking determination unit 66 to control the playhead and the envelope comparator 44. The driving end point T _B of the capstan control signal (Fig. 3C) is controlled so that the output exactly matches.

FIG. 3A shows the head selection signal 101 output from the capstan servo, FIG. 3B shows the control signal 109, and FIG. 3C shows the capstan control signal 108 for controlling the capstan motor. 3d and 3e are the playhead switching signal 102 and the output signal 103 of the envelope comparator 44 after the tracking by the microcomputer 6 is completed.

4 shows a tracking program operation of the microcomputer 6 during low speed playback. The SP head and the EP head are respectively selected in accordance with the head selection signal output from the capstan servo, and the SP head selected in the second step. A second step of generating a digital signal by comparing the signal to be reproduced with the signal reproduced from the EP head selected in the second step; and a capstan motor driving start point (T _a) of the capstan control signal from the edge of the head selection signal output from the capstan servo; ), A fourth step of determining whether the digital signal generated in the third step and the playhead selection signal output from the capstan servo are the same, and the digital signal and the playhead generated in the third step If the selection signal is the same, the tracking program is terminated. If the digital signal generated in the third step and the playhead selection signal are different, the capstan control signal. It performs a fifth step of controlling the capstan motor driving end point (T _B).

After a predetermined input key to adjust during low-speed playback track is input to the microcomputer 6 through the key input means (1) recognizes the capstan motor driving starting point of the capstan control signal (T _a) (402), the tracking program The parameter used to perform the initialization is initialized. (404) At this time, the capstan motor driving start point T _a of the capstan control signal is input by a polling edge of the head selection signal shown in FIG. 3a as shown in FIG. 3c. After time passes.

The SP head and the EP head are selected from the SP head selector SW1 and the EP head selector SW2 of the SP / EP head selector 2 in accordance with the head selection signal 101 (406). After comparing the envelope of the output video signal and outputting the digital signal according to the design rule (408), the digital signal 103 output from the envelope comparator 44 and the playhead selection signal 102 are compared logically ( In response to the head selection signal 101, the output of the logic comparator 62 within a predetermined time is ignored (masked).

According to the output of the masking unit 64, the playhead selection signal 102 and the output comparator 105 of the envelope comparator are compared (414). If the two signals are not the same, the capstan driving end point T _B of the capstan control signal is adjusted. Repeat from step 406 again. At this time, the capstan motor driving end point T _B of the capstan control signal shown in FIG. 3C is after a predetermined time has passed after the control signal shown in FIG. 3B is input.

When the playhead switching signal 102 and the output comparator 103 of the envelope comparator are the same according to the output of the masking unit 64, in step 406 according to the design specification, step 406 to step 414 in accordance with the predetermined condition (418, 420). After repeating step 414, the tracking program ends.

As described above, the automatic tracking method and apparatus for low speed playback of a video tape recorder control the capstan control signal so that the playhead selection signal and the signal output from the envelope comparator are adjusted to perform the tracking operation by the user. Automatic tracking takes place without

Claims (3)

A video tape recorder tracking method for controlling a capstan motor so that a playhead accurately traces a video tape, the method comprising: a first step of selecting an SP head and an EP head according to a head selection signal output from a capstan servo; A second step of generating an envelope comparison signal by comparing the envelope detected in the SP head selected in the first step with the envelope detected in the EP head; Extracting a waveform of a common part of the playhead switching signal and the envelope comparison signal generated in the second step; A fourth step of masking the waveform extracted in step 3 based on the rising and falling edges of the head selection signal for a predetermined time; A fifth step of determining whether the envelope comparison signal generated in the second step and the playhead selection signal are the same after the masking time in the fourth step has passed; And terminating the tracking program if the envelope comparison signal and the playhead selection signal are the same in the fourth step, and performing tracking up / down control until the waveform of the playhead switching signal and the envelope comparison signal are the same. A tracking method during slow playback of a video tape recorder that includes. SP / EP head selecting means for selecting the SP head and the EP head from the playback head according to the head selection signal; Envelope comparing means for comparing the envelope of the SP head selected from the SP / EP head selecting means with the envelope of the EP head and outputting the digital signal; The waveform of the common part of the digital signal output from the envelope comparing means and the playhead selection signal output from the capstan servo is extracted, and the waveform is masked for a predetermined time based on the rising and falling edges of the head selection signal to obtain a predetermined masking time. A micom that terminates a tracking program if the digital signal and the playhead selection signal are the same and performs tracking up / down control until the digital signal and the envelope signal are the same; And a capstan servo for outputting the head selection signal and the reproduction head selection signal and inputting the capstan control signal to drive a capstan motor. The tracking method of claim 2, further comprising: a low pass filter for low-pass filtering the output of the envelope comparing means, and a comparator for reducing the rise time and the fall time of the signal output from the low pass filter. Device.