KR100196854B1 - Auto-tracking method in a video cassette recorder when the video cassette recorder is still/slow playback mode - Google Patents

Abstract

The present invention relates to an auto-tracking method for still / slow playback in a video cassette recorder. Detecting the time Tv of the time point at which the output is performed; (B) detecting and comparing the envelope of the video signal reproduced from the SP head and the EP head to detect a time Te at the time when chattering of the envelope comparison signal occurs; (C) The absolute value (│Tv-Te) and the output of the difference value (Tv-Te) between the time (Tv) at which the video switching high signal is output and the time (Te) at the time when the chattering of the envelope comparison signal occurs. Comparing the time ε corresponding to half of the blanking period of the video signal to be obtained; (D) Absolute value (│Tv-Te) and output of the difference value (Tv-Te) between the time (Tv) at which the video switching high signal is output and the time (Te) at the time of chattering of the envelope comparison signal. Determining whether the difference is greater than zero if it is greater than a time corresponding to half ε of the blanking interval of the video signal; (E) If the difference value is greater than zero, the stop time of the capstan motor is advanced by a predetermined area so that the difference value becomes zero; otherwise, the stop time of the capstan motor is set by the predetermined area so that the difference value is zero Slowing down; (F) the absolute value (| Tv-Te |) of the difference value in step (c) is less than or equal to a time corresponding to half (ε) of the blanking interval of the output video signal and the step (e) Executing playback on the still picture when it is completed; And (g) returning the flow if the capstan motor has moved by judging whether or not the cassette tape has moved by an area corresponding to a predetermined frame of the video signal.

Accordingly, the present invention has the effect of obtaining an optimal still picture by detecting a point in time when chattering occurs in the comparison signal of the envelope signal and matching the point with the rising edge or falling edge of the video switching signal.

Description

The present invention provides an auto-tracking method for still / slow playback in a video cassette recorder.

1 is a schematic block diagram of hardware for implementing the present invention.

2 is a schematic diagram of a head drum mounted with four playheads used in the present invention.

3A and 3B are diagrams for explaining an abnormal still picture reproduction and a normal still picture reproduction according to a chattering interval.

4 is a flowchart of an auto-tracking method in still / slow playback in a video cassette recorder according to a preferred embodiment of the present invention.

5 is a diagram for describing a blacking period in a video screen.

* Explanation of symbols for main parts of the drawings

10: key input unit 20: micom

30: deck part 40: free amp part

50: signal processor 60: comparator

The present invention relates to still / slow playback of a video cassette recorder (hereinafter abbreviated as V. C. egg), and more particularly, to perform still / slow playback on V. C. and egg. The present invention relates to an auto-tracking method that enables a normal picture with little noise when executed.

In general, V.C.E. has a special playback function. Such special reproduction is to reproduce by changing the traveling speed of the cassette tape.

By the way, when the running speed of the tape changes, the trajectory of the head changes in various ways. Thus, the trajectory of the head changes, which causes the head to deviate from the track at the time of recording. As a result, the playback output decreases linearly as the playhead deviates from the normal track at the time of recording, and at the same time, since it is invading the adjacent track, cross talk occurs in the adjacent track.

However, the crosstalk of the luminance signal is almost negligible because it adopts the oblique azimuth recording method, and since the crosstalk of the color signal is canceled according to the PS or PI method, it is not output. Do not. This means that, even if the head is shifted to near the trap width, the playback can be performed first. If the head is shifted beyond the track width, the playback is possible because the same track exists again.

However, when the reproduction head is shifted further by the track width, no effective reproduction output can be obtained and noise bars are generated on the reproduction screen due to noise bands. Therefore, during the special playback, the section in which the noise bar appears is controlled to be included in the vertical blanking section.

On the other hand, among these special regenerations there is still / slow regeneration, which is a function of driving and regenerating a capstan motor at a predetermined slower speed than during stop or regeneration.

On the other hand, conventionally, in order to obtain an optimal screen during such still / slow playback, a predetermined number of still field screens are reproduced to find an optimal screen. In other words, if still / slow play is performed, the capstan motor or outside of the capstan motor may be changed because the stop time is determined after the CTL signal is detected based on the tracking data obtained by executing auto-tracking during normal play. If the regular operation is not performed at the correct position due to the noise, noise is generated on the screen, and in order to correct the noise, the user needs to correct it with manual tracking, and the user stops at the correct position that he / she wants to see. In the early stages of still / slow playback, there was a problem that the screen was not visible.

Accordingly, the present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a video signal reproduced at an SP and EP head at the time when a rising edge and / or a falling edge of a video switching pulse occurs. By matching the Envelope's chattering time, the still / slow playback of V.C.R can be reproduced and outputted optimally for each still picture and slow picture from the start of still / slow playback. To provide a method for auto-tracking.

According to a preferred embodiment of the present invention for achieving this object, in the auto-tracking method during still / slow playback in a video cassette recorder, (a) the still / slow playback key signal is inputted to the still / slow playback mode. If it is set, the step of detecting the time when the video switching high signal is output after stopping the capstom motor, and (b) detecting and comparing the envelope of the video signal reproduced from the SP head and the EP head to compare the envelope signal. Detecting a time point at which the chattering occurs and (c) chattering the time when the video switching high signal detected in steps (a) and (b) is outputted and the envelope comparison signal; Comparing the difference value of time at the time of occurrence with an absolute value and a time corresponding to half of the blanking interval of the output video signal, and (d) step (c). If the absolute value of the difference between the time at which the video switching high signal is output and the time at which an envelope comparison signal is chattered is greater than a time corresponding to half of the blanking interval of the output video signal, the difference is greater than zero. And (e) advancing the stop time of the capstan motor by a predetermined area so that the stop time of the capstan motor is zero if the difference value is greater than zero in the step (d), otherwise the difference is zero. Delaying the stop point of the capstan motor by a predetermined area such that the value is zero; and (f) the absolute value of the difference value is less than half the blanking period of the video signal outputted in the step (c). In the same case and when the step (e) is completed, executing the playback on the still picture; When you have to move by moving the cassette tape it is determined whether the area corresponding to the predetermined frame of the video signal includes the step of returning the flow.

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

1 is a schematic block diagram illustrating hardware for implementing the present invention.

As shown in FIG. 1, the hardware for carrying out the present invention includes a key input unit 10 for providing a predetermined function key signal for still / slow playback, and the like, and a key signal provided from the key input unit 10. FIG. A microcomputer 20 for generating a control signal according to the present invention, a deck unit 30 for performing playback from a cassette tape loaded and driven according to a control signal provided from the microcomputer 20, and outputting a playback signal accordingly, and a deck unit. A preamplifier 40 for amplifying and outputting a weak reproduction signal provided by the predetermined level by a predetermined level, a signal processor 50 for processing and outputting an output signal of the preamplifier 40 to a video signal, and Envelope detection unit 60 for detecting the video envelope signal from the output signal of the amplifier unit 40 and the detected analog envelope signal provided from the envelope detection unit 60 is converted into a digital signal to the microcomputer 20 And analog / digital converters (A / D: 70).

When a function key signal for still / slow reproduction is provided from the key input unit 10, the microcomputer 20 generates a control signal according to the deck unit 30. When a control signal for still / slow regeneration from the microcomputer 20 is provided to the deck unit 30, the capstan motor (not shown) built in the deck unit 30 stops driving, and the built-in play head (shown in FIG. Is executed to play the recording track at the stationary position and provide the reproduced video signal to the preamplifier 40. FIG.

The preamplifier 40 amplifies the weak reproduction signal provided from the deck unit 30 by a predetermined level and outputs the amplified signal to the signal processor 50 and the envelope detector 60. In this case, the signal processing unit 50 displays the reproduction signal provided from the preamplifier unit 40 and amplified to a predetermined level by processing the video signal and outputting it to a screen (not shown).

Meanwhile, the envelope detection unit 60 detects an envelope of the amplified video signal provided from the preamplifier unit 40 and provides the envelope to the A / D converter 70, and the A / D converter 70 provides the envelope detection unit. The analog envelope signal provided from 60 is converted into a digital signal and provided to the microcomputer 20.

2 is a schematic diagram of a head drum on which four playheads are mounted. As shown in FIG. 2, the EP L head and the SP R 'head and the SP L' head and the EP R head are mounted on the head drum at intervals of 2H sections, respectively.

On the other hand, in general, data of one track, that is, data corresponding to one field, is reproduced and output during the stop period of still / slow reproduction. At this time, if the stop time of the capstan motor is not correct, the head is off the track, the off portion is the edge of the head and the track is twisted, the noise is generated. To eliminate this, the head is switched using a head amplifier switch (not shown), in which a switching bar is generated on the screen. That is, at the point where the head crosses two tracks, since the SP head EP head passes through the track at intervals of 2H, the envelope of the video signal reproduced from each head is detected and compared during the interval. Chattering of the envelope comparison signal occurs, which is illustrated in FIGS. 3a and 3b.

3A and 3A are diagrams for explaining an abnormal still picture reproduction and a normal still picture reproduction according to the chattering period.

3A shows the relationship between the video switching signal, the envelope comparison signal, and the head amp switching signals when an abnormal still picture is reproduced. As shown in FIG. 3A, in the case of abnormal playback, an area where the head crosses the track occurs at the midpoint of the track after video switching and head amp switching occurs. In other words, the chattering area B of the envelope comparison signal occurs at the midpoint of the track. In this case, noise is generated at the top of the screen by an area corresponding to the section 'C'.

3B shows the relationship between the video switching signal, the envelope comparison signal and the head amp switching signals when a normal still picture is reproduced. As shown in FIG. 3B, the start point of the chattering area D of the point where the video switching and head amp switching high signal and the low signal occur and the envelope comparison signal of the SP head and the EP head The points across the track are nearly identical.

As a result, in order to reproduce a normal still image, the capstan motor is stopped after a predetermined time after the CTL signal is detected, but when the chattering of the non-lobe comparison signal other than the rising edge and falling edge of the video switching signal is matched, do.

Therefore, according to the present invention, the microcomputer 20 compares the envelope signal, which is a digital signal provided from the A / D converter 70, detects a time point at which chattering occurs and accordingly the capstan motor of the deck unit 30. The control signal is generated to stop the driving of the capstan motor at the point where the video switching point coincides with the chattering occurrence point of the envelope comparison signal.

4 is a flowchart of an auto / tracking method in steel / slow regeneration in V.C.R according to a preferred embodiment of the present invention.

In step S10, it is determined whether the still / slow play key signal is input. When the still / slow play key signal is input in step S10 and set to the still / slow play mode, in step S20, the capstan motor is stopped, and at the track of the stopped position, the video switching high signal is output. The time Tv is detected. When step S20 is completed, step S30 detects and compares the envelope of the video signal reproduced from the SP head and the EP head to determine the time Te at the time when chattering of the envelope comparison signal occurs. Detect.

Thereafter, in step S40, the difference value between the time Tv at which the video switching high signal detected in steps S20 and S30 is output and the time Te at the time when chattering of the envelope comparison signal occurs. It is determined whether the absolute value of is greater than a time (ε) corresponding to half of the blanking section of the output video signal. As shown in FIG. 5, this section is a blanking section that does not appear on the video screen. It does not matter.

On the other hand, in step S40, the absolute value (│Tv-Te) of the difference between the time Tv at which the video switching high signal is output and the time Te at the time when chattering of the envelope comparison signal occurs is If it is greater than a time ε corresponding to half of the blanking interval of the output video signal, the process proceeds to step S50, otherwise proceeds to step S80.

When the process proceeds from step S40 to step S50, in step S50, the difference value Tv-Te> 0 between the time at which the video switching high signal is output and the time at which chattering of the envelope comparison signal is generated is greater than zero. If it is greater than zero, then the process proceeds to step S60 if it is greater than zero, and to step S70.

When the process proceeds from step S50 to step S60, in step S60, the capstan motor is stopped by a predetermined area in advance, that is, the capstan motor is stopped as soon as a predetermined time and the time when the video switching high signal is output is enveloped. When the difference value (Tv-Te> 0) of the time at which the chattering of the comparison signal is generated becomes zero, and the process proceeds to step S70, in step S70, the stop point of the capstan motor is delayed by a predetermined area to switch the video switching high. The difference value (Tv-Te> 0) between the time at which the signal is output and the time at which chattering of the envelope comparison signal occurs is zero.

When step S60 or step S70 is completed, playback of the still picture is executed in step S80. In step S90, it is determined whether there is a movement of the frame. At this time, if there is a movement of the frame, the flow returns.

Accordingly, the present invention obtains a comparison signal of an envelope signal reproduced from each head at the start point of the still / slow regeneration at the time of still / slow regeneration, detects the point at which the chattering is generated, and detects the point. By matching the rising edge or the falling edge of the video switching signal, there is an effect that an optimum still picture can be obtained.

Claims (1)

In the auto-tracking method for still / slow playback in a video cassette recorder, (a) If a still / slow playback key signal is input and set to the still / slow playback mode, the video switching high signal is output after stopping the capstan motor. Detecting a time Tv of the viewpoint; (B) detecting and comparing the envelope of the video signal reproduced from the SP head and the EP head to detect a time Te at the time when chattering of the envelope comparison signal occurs; (C) The difference value Tv-Te between the time Tv at which the video switching high signal detected in steps (a) and (b) is output and the time Te at the time when chattering of the envelope comparison signal occurs. Comparing the absolute value (| Tv-Te |) with time (ε) corresponding to half of the blanking interval of the output video signal; (D) The absolute value (Tv-Te) of the difference value Tv-Te between the time Tv at which the video switching high signal is output and the time Te at which chattering of the envelope comparison signal is generated in step (c). Determining whether the difference is greater than zero if Te | is greater than a time corresponding to half (?) Of the blanking interval of the output video signal; (E) In step (d), if the difference value is greater than zero, the stop time of the capstan motor is advanced by a predetermined area such that the difference value becomes zero, otherwise the difference value becomes zero. Delaying the stop point of the capstan motor by a predetermined area; (F) the difference in step (c); Executing playback on a still picture when the absolute value (Tv-Te) is less than or equal to a time corresponding to half (ε) of the blanking interval of the output video signal and when step (e) is completed; ; (G) determining whether the capstem motor has moved the cassette tape by an area corresponding to a predetermined frame of the video signal, and returning the flow if the capstem motor has moved, the auto-tracking method in still / slow playback in a video cassette recorder.